VASIMR Ion Engine Could Cut Mars Trip To 39 Days

An anonymous reader writes "It would take about 39 days to reach Mars, compared to six months by conventional rocket power. 'This engine is in fact going to be tested on the International Space Station, launched about 2013,' astronaut Chris Hadfield said. The Variable Specific Impulse Magnetoplasma Rocket (VASIMR®) system encompasses three linked magnetic cells. The 'Plasma Source' cell involves the main injection of neutral gas (typically hydrogen, or other light gases) to be turned into plasma and the ionization subsystem. The 'RF Booster' cell acts as an amplifier to further energize the plasma to the desired temperature using electromagnetic waves. The 'Magnetic Nozzle' cell converts the energy of the plasma into directed motion and ultimately useful thrust."

Comments

Billions and billions...

[GenP]

A few hundred Newtons here, a few hundred Newtons there, and pretty soon you're talking about some real delta-v!

Re:Billions and billions...

[ELProphet]

Let's run the math:

(Using classical mechanics, Google Calculator, and some rounding)
40 days, 60 million km to mars at closest approach.
Spend half the time accelerating, half the time decelerating.

For acceleration:
x = x0 + v0t + (at^2)/2
2 * 30 million km / (20 days) ^ 2 = 2e-2m/s^2

Let's use a Space Shuttle, 2,029,203 kg
The force of the engine is
F = ma = ((2 029 203 kg) * 2 * (30 million km)) / ((20 days)^2) = 40 774.5587 newtons
Work along a straight line is Force time distance
W = Fd = (40 774.5587 newtons) * 30 million kilometers = 1.22323676 × 10^15 joules
Power is work over time
P = W/t = 1.22323676 × ((10^15) joules)) / (20 days) = 0.707891644 gigawatts
Of course, we need to do this twice:
Ptotal = 2P = 2 * 0.707891644 gigawatts = 1.41578329 gigawatts

Which is surprisingly close to the power needed to propel a DeLorean through time...

Note that this is only the power needed to get the ship to Mars and then stop it; I have no idea the efficiency of their engine, life support, etc, but hey, the math works close enough for me.

I'm a little weak on my power generation math- anyone who knows something about solar panels and PV arrays want to take a shot at the power requirements?

No quite yet.

[Anonymous Coward]

No stated in this article.

But I'm pretty sure the engine discussed will need to be roughly 100x more powerful to make that 39 day trip a reality.

Re:No quite yet.

[doug]

No stated in this article.

But I'm pretty sure the engine discussed will need to be roughly 100x more powerful to make that 39 day trip a reality.

No, not really. Hauling the fuel for chemical rockets into orbit is expensive, so mostly they do hard burns to get the right speed and direction, then they coast most of the trip. VASIMR doesn't need the heavy fuel, as it is solar powered, so it provides constant thrust. Apparently days of constant acceleration makes a difference.

- doug

Re:No quite yet.

[inviolet]

No, not really. Hauling the fuel for chemical rockets into orbit is expensive, so mostly they do hard burns to get the right speed and direction, then they coast most of the trip. VASIMR doesn't need the heavy fuel, as it is solar powered, so it provides constant thrust. Apparently days of constant acceleration makes a difference.

There is no free lunch. VASIMR is not radically more efficient than a chemical rocket. Its advantage is that it can run off electricity. But the electricity available from solar panels is slight.

This particular VASIMR is an improvement because it can handle more power... more than solar panels could provide. It will require a nuclear powersource -- a fission plant, or a very very powerful RTG.

But if you are willing to heft a fission plant into orbit, then you could just use it as a conventional nuclear rocket (i.e. superheated steam).

Re:No quite yet.

[TheRaven64]

VASIMR doesn't need the heavy fuel, as it is solar powered, so it provides constant thrust

Ummm, no. Or, rather, technically yes, but not really. In a chemical rocket, fuel and reaction mass are the same thing. The fuel burns, expands, and flies out of the back. With an ion engine, they are separate. The fuel is anything that can produce electricity (e.g. solar or nuclear plants) and the reaction mass is something that you've ionised. This still has mass, and still has to be carried with you until you throw it out of the back, irrespective of where the power comes from.

The important thing to remember is that all of these are reaction drives. They work according to the principle of conservation of momentum. When you throw some mass out of the back of your space ship, the space ship gains the same amount of momentum as the thing you throw out of the back. You can double the momentum that you gain from your engine by either doubling the speed of the ejected reaction mass, or by doubling the amount you throw out. With conventional rockets, the speed is limited by the rate of reaction, which is fairly fixed. With an ion drive, the speed is limited by the amount of power you put in.

You still need to carry the propellant, but if you can throw it out at ten times the speed then you need a tenth of the amount. If you need a tenth of the amount, then your space ship will mass a little over a tenth as much, and so the speed that it gains from this change in momentum will be almost ten times as much.

In theory, you could use a small glass of water, accelerated to a significant fraction of the speed of light, as your propellant for an entire trip to Mars and back. In practice, there is a limit to the speed to which an ion thruster can accelerate the ions it's throwing out and so you still need quite a large amount of propellant.

Re:No quite yet.

[jollyreaper]

In theory, you could use a small glass of water, accelerated to a significant fraction of the speed of light, as your propellant for an entire trip to Mars and back. In practice, there is a limit to the speed to which an ion thruster can accelerate the ions it's throwing out and so you still need quite a large amount of propellant.

And also led to the scifi observation (niven or pournelle, I forget which) that any technology that makes for a decent spaceship engine also makes for a decent weapon.

Re:No quite yet.

[CopaceticOpus]

The VASIMR engine couples well with an idea I've been pondering. Imagine building a ship designed to latch onto a largish asteroid, and then use the asteroid's mass as the ejected reaction mass for acceleration.

The ship would need a powerful nuclear reactor, and robotics capable of slowly grinding the asteroid's mass to a fine powder. The engine would need to be able to accelerate this powder to an enormous speed, regardless of what the powder was made of.

Such a ship would be able to accelerate to amazing speeds, and could be a perfect deep space explorer. Imagine if we could do a close flyby on another solar system! The powerful nuclear reactor could be used to power advanced scientific instruments, and to beam a very strong signal back to earth.

I wonder how feasible this would be. I'd love to see an unmanned craft reach another solar system in my lifetime. To me, that would be more exciting than putting a man on Mars.

Re:No quite yet.

[Interoperable]

then you could just use it as a conventional nuclear rocket (i.e. superheated steam).

The VASMIR can accelerate a neutral gas to much, much higher velocities than a steam driven rocket would. This means significantly more impulse per unit mass so the fuel weight would be dramatically reduced. Sure the reactor is heavy but it still packs a much higher power density than combustibles so all in all a VASMIR can pull off an excellent power to weight ratio for an extended acceleration.

Re:No quite yet.

[GigsVT]

Imagine if we could do a close flyby on another solar system!

A close flyby at 0.5C might not be as exciting as you'd think.

Re:No quite yet.

[TheRaven64]

It would work better if you substituted 'comet' for 'asteroid'. For an ion engine, you (oddly enough) need ions, and something made mostly of ice is much easier to ionise than something made mostly of rock.

Re:No quite yet.

[drinkmorejava]

Actually, conventional rockets are not limited by the rate of reaction. Momentum is limited by the density of the gas and the cross sectional area at the throat of the nozzle where the flow hits the sonic condition. You could speed up the reaction a million times and increase the pressure in the reaction chamber as much as you wanted, but the flow will absolutely not go any faster than Mach 1 at the throat, period. ...Just saying. And yes, I am a rocket scientist.

Re:No quite yet.

[EvilTwinSkippy]

Nuclear reactors don't have to be all that heavy. The Pioneer and Voyager spacecraft had plutonium power cells. You pretty much can scale nuclear power to whatever size and power you need. (We don't usually use small power plants simply because it's more cost effective to power devices other ways.)

Re:No quite yet.

[JerryLove]

There is no free lunch. VASIMR is not radically more efficient than a chemical rocket.

Yes. Yes it is. It's a very efficient Ion drive.

http://www.projectrho.com/rocket/rocket3c2.html

This particular VASIMR is an improvement because it can handle more power... more than solar panels could provide. It will require a nuclear powersource -- a fission plant, or a very very powerful RTG.

Solar panels can potentially provide the entire output of the sun in relevent wavelengths / the efficency of the solar panel... though to do that, it would need to encompass the sun.

I suspect the most likely power would be a nuclear battery (thermo-couples powered by the heat of radioactive decay), but there are many options.

But if you are willing to heft a fission plant into orbit, then you could just use it as a conventional nuclear rocket (i.e. superheated steam)

You don't get the same speed out of that reaction mass, so you don't have the same efficiency.

Re:No quite yet.

[EvilTwinSkippy]

One minor knit to pick. The momentum doesn't double with a doubling of the speed of the reaction mass. It quadruples. Remember your high school physics: KE=0.5*m*v**2

If anything, it only reinforces your point.

Re:No quite yet.

[phaggood]

And within a generation; intrastellar travel goes from commonplace to non-existant as the system's only "intelligent" species decides to blanket their section of space with a fine, abrasive, high-velocity powder.

Might help as an alien-invasion repellant, tho.

Re:No quite yet.

[Anonymous Coward]

The Kzinti lesson.

Re:No quite yet.

[Anonymous Coward]

Niven, in his Known Space series.

Re:No quite yet.

[CopaceticOpus]

We could slow it down as needed by decelerating, just as the Mars mission would do. That does probably mean the mission would take 3-4 times as long, but it should still be feasible.

Alpha Centauri is 4.24 light years away. If the ship could reach 0.5c at the half way point, it should average 0.25c (very approximately) for the trip. This puts the trip at 17 years, plus another 4 years to receive the transmission.

Unfortunately, I doubt that 0.5c is feasible. Perhaps 0.1c is more attainable. This means it would take 89 years to get a signal back, which is outside my lifetime but still very respectable.

Even if it would take 1000 years, I think we should go for it if it can be done.

Re:No quite yet.

[Anonymous Coward]

You still need to carry the propellant, but if you can throw it out at ten times the speed then you need a tenth of the amount.

That reminds me of some parties I went to as a freshman.

Re:No quite yet.

[voidphoenix]

Momentum != kinetic energy.

Re:No quite yet.

[Xiterion]

Momentum != kinetic energy.
p = mv is the equation you're looking for.
Obligatory Wikipedia link.

Re:No quite yet.

[2short]

Why not?

CopaceticOpus specifically references an unmanned craft. We could argue how exciting that would be (I think very), or whether anything manned is likely in our lifetimes (clearly no) or ever (probably not).

But once we assume we're doing an unmanned flyby, 0.5C gets you somewhere between hours and weeks of taking better pictures than you could from Earth. How much depends on the quality difference of instruments on earth vs on the probe; which will obviously be huge, but it's hard to say exactly how huge.

Re:No quite yet.

[mhajicek]

I'd vote to sit back and wait another decade or two for further technological advance. Also remember that in order to capture an asteroid or comet to use it for reaction mass you have to match vectors with it. That means slowing practically to a stop to refuel unless it happens to be going your way. Your idea seems to be more useful as an option for refueling at or near the midpoint of a round trip.

Re:No quite yet.

[TheKidWho]

Vasimr is capable of Specific Impulses of 5000+... Chemical Rockets have Specific Impulses of maybe 500 at most.

That's an order of magnitude difference.

Re:No quite yet.

[Zerth]

You needn't rely on direct solar energy, you could easily beam power(laser or rectenna) from a larger facility.

Re:No quite yet.

[Anonymous Coward]

I think it was Niven - part of the Man Kzin Wars series, probably in the Ringworld series as well.

Re:No quite yet.

[dsvick]

... accelerated to a significant fraction of the speed of light ...

Unless you keep the actual acceleration down the problem would be the fact that anything above 15 - 20 gravities and all of your passengers will pass out, and anything above say 40 - 50 and you'll turn them all into paste. Of course,if the trip is long enough, any sort of constant acceleration, even if is just a few gravities would be much faster than a single acceleration stage followed by coasting and an equally short deceleration.

Re:No quite yet.

[Anonymous Coward]

But if you are willing to heft a fission plant into orbit, then you could just use it as a conventional nuclear rocket (i.e. superheated steam).

A conventional nuclear rocket will run out of steam (reaction mass) long before a VASIMR will. There's a tradeoff between using lots of reaction mass and using lots of energy. Chemical rockets are at the first end, then nuclear rockets, then things like VASIMR and ion drives. The first end is better for high-thrust applications (like launching from a planet), and the second end is better for long-duration applications (like traveling from Earth to Mars).

Re:No quite yet.

[ZombieWomble]

There's a bit of a confusion of terms here - nuclear reactors do have some degree of a size restriction, but neither the Pioneer or Voyager programs used nuclear reactors as their power source. They both used radiothermal generators (RTGs) - that is, they derived their power from the heat generated by the decay of a nuclear isotope, rather than a fission reaction.

This latter kind of generator is pretty much infinitely scalable, as you say, but aren't so efficient for big power demands - most of the RTGs in the probes you mention provide a few hundred watts, even when new.

For these thrusters, you're talking about burns of 10 MJ or more, which would require a vastly bigger RTG (or, more likely, a true reactor as the scaling would make it the more efficient choice) to get a reasonable pulse rate out of it.

Re:No quite yet.

[simcop2387]

yes but if we use all the comets, where will we get the ice without bugs in it to cool the oceans to combat global warming?

Re:No quite yet.

[Anonymous Coward]

Easily? You are joking, right? I don't think beaming anything to orbital target millions miles away (a rocket on it's way to Mars) is easy ... please stop your BS.

Re:No quite yet.

[NeutronCowboy]

Regarding the fuel, there is a distinct advantage to being able to use anything that can be ionized as fuel: you can scoop up interstellar dust during your voyage and use that. Yes, it's very little, and it won't be greater than burnrate, but it's something. And the longer the voyage, the more important this will be.

Re:No quite yet.

[MartinSchou]

Silly question, but what speed is Mach 1 in a vacuum?

Or is it Mach 1 for the exhaust fumes?

Re:No quite yet.

[Plunky]

1g is 9.8 m/s per second. After the first second, you are travelling at 9.8m/s. After the second you will be doing 19.6m/s .. to reach 10% of the speed of light (is that significant enough?) you need to accelerate for 299,792,458 (speed of light) / 10 (= 10%) / 9.8 (1g) / 60 (seconds) / 60 (minutes) / 24 (hours), or about 35 days. Thats not much eh?

Re:No quite yet.

[EnsilZah]

Heh, not exactly brain surgery, is it?
Sorry for the offtopic, I was just reminded of this.

Re:No quite yet.

[Nerdposeur]

This was one of the most interesting and well-written posts I've read in a long time.

Re:No quite yet.

[greyhueofdoubt]

You can double the momentum that you gain from your engine by either doubling the speed of the ejected reaction mass, or by doubling the amount you throw out.

I have one small quibble with your otherwise very informative post (and it may turn out that I'm wrong)... But I've always worked under the assumption that Ke=MV^2. Therefore, momentum will increase as a square of the velocity instead of the product, as you stated. Having the imparted momentum rise as a square instead of linearly is what gives an ion engine (very fast, lighweight particles) such an advantage over a chemical engine (slower but more massive particles).

I'm open to corrections.

-b

Re:No quite yet.

[Anonymous Coward]

In theory, you could use a small glass of water, accelerated to a significant fraction of the speed of light, as your propellant for an entire trip to Mars and back. In practice, there is a limit to the speed to which an ion thruster can accelerate the ions it's throwing out and so you still need quite a large amount of propellant.

And also led to the scifi observation (niven or pournelle, I forget which) that any technology that makes for a decent spaceship engine also makes for a decent weapon.

Ringworld, by Niven. I liked it a lot.

Re:No quite yet.

[avandesande]

Electricity also lends itself to a modular design- you can just plug it into a thruster module. There is no reason you couldn't get all of the components into orbit and put the spaceship together. If your module goes bad just replace it with a new one.

Re:No quite yet.

[qc_dk]

VASIMR is not radically more efficient than a chemical rocket

Yes it is. The efficiency of a rocket is tied to the velocity of the propellant. VASIMR has a much higher velocity(~ speed of light /- 10%) than chemical(liquid propelant ~4,400 m/s) rockets. On the other hand VASIMR has very litte thrust. That means it is only useful in situation where there are no forces working against you i.e. already in orbit and no atmosphere.

Re:No quite yet.

[Anonymous Coward]

And also led to the scifi observation (niven or pournelle, I forget which) that any technology that makes for a decent spaceship engine also makes for a decent weapon.

That's how the war with the Kzinti started, IIRC.

Re:No quite yet.

[CopaceticOpus]

Not really a problem. For one thing, space is really big, and the particles will disperse. Secondly, adding a slight curve to the flight path will result in the jet of particles missing our solar system .

Re:No quite yet.

[HiThere]

No, I don't think so. At mid-point slowing down is what the rest of the trip is about.

If would be interesting to know whether a Vasimir rocket could use boiling rock as an ion source, though. (But perhaps one should use a comet instead. Sounds much more practical.)

Note that for voyages of this length, a small improvement in ISP could produce extreme benefits. And remember that for a Vasimir engine the default assumption is that the acceleration is continually increasing. (Because the impulse is constant, and the mass being accelerated is continually decreasing.)

Re:No quite yet.

[Anonymous Coward]

>It will require a nuclear powersource -- a fission plant, or a very very powerful RTG.

Or a ZPM.

Re:No quite yet.

[IronChef]

That's the "Kzinti Lesson."

http://www.larryniven.org/kzin/worlds.shtml

Early interstellar ramships employed fusion-powered photon drives. The ships were launched by photon sails and the laser cannon batteries on the asteroids. The cannons were fired into the sails, providing the ramships with initial motive power before their huge scoops could pick up enough interstellar hydrogen to begin the fusion process. When the Kzinti ships moved within range of the cannons, the human crews fired and tore the enemy apart.

The Kzinti lesson is, "a reaction drive's efficiency as a weapon is in direct proportion to its efficiency as a drive."

Re:No quite yet.

[TheRaven64]

As someone else already pointed out to the last person to make that comment: Kinetic energy and momentum are not the same. Momentum is always conserved, even in the presence of special relativistic effects[1]. Kinetic energy is not. The total energy in a closed system is constant, but in a rocket a lot of it will be lost as heat, which adds nothing to the thrust.

This is actually partially the reason why ion drives are difficult to build and lower-velocity rockets are easier. The energy required scales with the square of the velocity, but the momentum scales linearly. If you double the mass of your propellant, you double the momentum and double the imparted momentum (and therefore the acceleration). If you double the velocity then you increase the power needed by a factor of four. You quickly run out of chemical energy if you try to scale this up with chemical rockets. The advantage that ion drives have is that the energy comes from outside, so the velocity is only limited by the amount of energy you are willing (and able) to pump into it. And the amount it can take before melting, of course.

If you've got a nuclear reactor then you can pump a huge amount of energy into your electromagnets and accelerate the ions to a very high speed, but (assuming no losses) you need to increase the energy you put in by a factor of four to double the acceleration.

Faster, less-massive, particles are still generally better because you have to carry fewer of them. This has a knock-on effect, because you don't have to accelerate the ones you aren't carrying, so the imparted momentum goes a lot further.

[1] You can actually derive special relativity from the principle of conservation of momentum. I had to at school; it's quite an elegant bit of mathematics, and only takes about one page. General relativity is a lot more complex and hurts my brain

Re:No quite yet.

[mmontour]

There's a bit of a confusion of terms here - nuclear reactors do have some degree of a size restriction, but neither the Pioneer or Voyager programs used nuclear reactors as their power source.

The Soviet Cosmos satellites used true nuclear reactors.

Re:No quite yet.

[Manhigh]

Technically speaking VASIMR, like ion propulsion, is electrically powered. For it to be constant thrust it would need to have that electricity generated by a nuclear reactor. Since solar power decreases as an inverse square law, a solar powered VASIMR would not be constant thrust.

Re:No quite yet.

[Anonymous Coward]

I would mod you up for the sig alone, but this comment is already a 5. I'll have to thread stalk you and do so elsewhere. =P

Re:No quite yet.

[CopaceticOpus]

Sitting back and waiting does not lead to much technological advancement. Taking on an ambitious project tends to inspire many advances.

The idea is not to catch asteroids along the way. Rather, the craft would catch one large asteroid of sufficient mass to provide all the raw material needed for the journey. Using an asteroid saves the huge cost of lifting this massive raw material into space.

Re:No quite yet.

[v1]

There's also one thing that I believe is being seriously overlooked.

“It turns electrical power into thrust so that we can use solar energy” to power a spaceship, he said.

I'd like to slightly adjust that to

“It turns electrical power plus a small amount of matter into thrust so that we can use solar energy” to power a spaceship

The key is to use the electricity to accelerate the matter to a very high velocity so that very little physical "fuel' can be used to achieve a large amount of thrust. Mass is still required to be thrown overboard in one direction to achieve thrust in the opposite direction. It's just that the faster you throw it away, the more thrust you get.

So, no, it does not use electricity as the sole fuel. It just does a very good job of making the best use of a limited consumable resource in the engine/ship.

Now if it were possible to skim the mass out of space as you travel, that could replenish your stock. Sort of like ships of the Star Trek lore grab deuterium from stars instead of carrying all they need. But then even if you can find something in space to use for mass, everytime you pick some up you're having to accelerate it to your speed when you catch it, thus slowing you down a bit, so the gain would not be as much as you might originally expect, and would become more of a problem as your speed increased.

Re:No quite yet.

[Anonymous Coward]

1MW of solar panel +Vasimr has a mass less than 5000kg and collects about 86GJ of energy per day.That's about the same energy as is in 8000kg of H2/LOX rocket fuel.

Each day the 1MW Vasimr delivers the delta v equivalent of 500kg of LOX/H2 using just 50kg of fuel. For trips that take weeks or months the potential mass savings are just enormous.

Re:No quite yet.

[ShooterNeo]

Question : There's a nasty logarithm in the rocket equation. Basically, the lower the exit velocity of your propellant, the larger the % of the mass of your spaceship has to be dedicated to just fuel. Also, the higher the delta V you want, the bigger that percentage gets, to where you might need a fuel tank the size of the moon to get a pebble to Alpha Centauri. Does a beam riding spacecraft where you ride on a beam of small smart rocks fired from a coilgun eliminate the logarithm? Basically, you'd have a coilgun out in space that would fire a series of tiny projectiles, weighing under a gram, with nanoscale guidance and maneuvering systems. They would hurtle through space until reaching your spacecraft, which would basically be a long coil-gun, and it would decelerate the projectile, storing the energy in capacitors, and then accelerate it the other direction. Momentum is transferred, your spacecraft speeds up. For slowing down, you throw away most of your space ship and use the thrown away portion like a reflector.

Re:No quite yet.

[TheCarp]

Thats true of many things really. Whether something is a weapon or not really has more to do with what use it is designed for, more than what it does. A large rail gun could be used for many things, you could use it to shoot a payload to the top of a mountain. You could use it to put a shuttle in space, you could use it to drop explosive shells on your enemies. One of these uses makes it a weapon.

Of course, dropping space shuttles all over your enemies is probably pretty effective too, though damned expensive. Then again, if you were routinely shelling with space shuttles, production volume would drastically reduce the per unit price of the shuttles....

-Steve

Re:No quite yet.

[mcrbids]

My maths around high-end physics is weak, so perhaps one of the more qualified slashdotters could answer my question?

Yes it is. The efficiency of a rocket is tied to the velocity of the propellant. VASIMR has a much higher velocity(~ speed of light /- 10%) than chemical(liquid propelant ~4,400 m/s) rockets. On the other hand VASIMR has very litte thrust. That means it is only useful in situation where there are no forces working against you i.e. already in orbit and no atmosphere.

Is there a limit to specific impulse? Do you "run out" of improvement as you pack ever more energy into each specific atom of propellant? Based on my "gut feeling", I'd say that there isn't any such limit, because as you approach the speed of light, the mass of the propellant rises with unlimited potential. (if a particle with mass were travelling at the speed of light, its mass would be infinite) Thus you can continue bundling ever-more energy into your propellant, and specific impulse would continue to increase, for as far as you have the ability to add more energy....

It makes sense to me, but is this right?

Re:No quite yet.

[Anonymous Coward]

Interesting idea, but there's a bit more work to be done. First off, if you shot the pebble back out the same way it came in, it'd collide with the next pebble coming in. If you didn't, that would require that (at least) one of these coils is off-center, meaning your ship will likely spin unless you have both receiving and shooting coils balanced and working at the same time. Secondly, as you accelerate, you'll get less benefit from catching the pebbles, and they'll arrive farther apart unless the cannon launches them faster to match your acceleration. How is this cannon going to stay still while firing all these little rocks at you? Finally, what if one of these pebbles misses the decelerator?

That said, if you held on to the pebbles instead of firing them back right away, you could turn around and use them to decelerate without needing to discard the ship.

Re:No quite yet.

[greyhueofdoubt]

Thanks for the clarification. This is not my area of expertise :)

-b

Re:No quite yet.

[torkus]

...a close flyby? If you're going to go almost all the way to another star, why not complete the trip?!

The majority of the distance is between the solar systems...and you still have to turn around and come back home.

You'd do better with a one-way trip, re-fuel, and come back. Unless you found a solar system devoid of mass...in which case you're SOL. Or...even better a true one-way trip and send information back.

The problem with going so far is technology is evolving at such a rate that any probe we send out would probably arrive after the second generation probe.

Re:No quite yet.

[Rising Ape]

The maximum would be if you had matter/antimatter fuel, and somehow reflected the annihilation photons all in the thrust direction. The specific impulse then would be 30 million seconds (photon energy = mc^2, photon momentum = E/c, therefore impulse = mc and specific impulse = mc / mg = 3e7 seconds. m here refers to mass of fuel.).

Mass is an invariant, it doesn't increase with speed. "Relativistic mass" isn't really helpful, as a concept, as it leads to confusion - if what you said was true, the usable energy in the fuel would be frame-of-reference dependent, which doesn't make a lot of sense.

Re:No quite yet.

[phantomcircuit]

Not to mention that it could be refueled in orbit, so the heaviest part of the rocket will only need to get off earth once.

Re:No quite yet.

[cheesybagel]

Nuclear reactors for electric propulsion in near Earth space are not nearly as useful as claimed... You need to dissipate a lot of thermal energy from the reactor using radiative dissipation. The dissipation panels end up being so large and heavy you were probably better off using the solar panels in the first place.

Once you get away from Mars though, they start to make sense.

Re:No quite yet.

[mcvos]

Easily? You are joking, right? I don't think beaming anything to orbital target millions miles away (a rocket on it's way to Mars) is easy

All the more reason to develop this technology.

Re:No quite yet.

[mcvos]

Mass is an invariant, it doesn't increase with speed. "Relativistic mass" isn't really helpful, as a concept, as it leads to confusion - if what you said was true, the usable energy in the fuel would be frame-of-reference dependent, which doesn't make a lot of sense.

Didn't Einstein write something interesting about this?

Re:No quite yet.

[mcvos]

Any solution where you don't have to bring your reaction mass with you, fixes the problem. I'd rather use light or charged particles than rocks, though.

(I'm not a rocket scientist, though.)

Re:No quite yet.

[Nefarious Wheel]

Nuclear reactors don't have to be all that heavy. The Pioneer and Voyager spacecraft had plutonium power cells. You pretty much can scale nuclear power to whatever size and power you need. (We don't usually use small power plants simply because it's more cost effective to power devices other ways.)

Radioisotope thermoelectric generators (RTG) have been going into space for quite a few years now. Basically you wrap fins around a slug of Plutonium 238 and suck the heat. They run as the hot end of little single-piston or acoustic stirling generators (cold end being a radiator into deep space) in some applications. You end up with a long-term, compact electricity source.

With this sort of long-term electricity source you can potentially run a VASMIR engine for a very, very long time. I think some interesting examples of how far continuous thrust could take you were worked out in "A Step Further Out" (Pournelle) a few years ago. Interesting reading.

Re:No quite yet.

[mcvos]

Unless you keep the actual acceleration down the problem would be the fact that anything above 15 - 20 gravities and all of your passengers will pass out, and anything above say 40 - 50 and you'll turn them all into paste. Of course,if the trip is long enough, any sort of constant acceleration, even if is just a few gravities would be much faster than a single acceleration stage followed by coasting and an equally short deceleration.

A few gravities? Ion engines work with tiny fractions of a g. The long trip + continuous accelleration is the entire point of the things.

Re:No quite yet.

[Patch86]

If you remove the life support bits (because you wouldn't want to be shelling your enemies with expensive astronauts), forget about making it reusable (try reusing one after dropping it on your enemies) and maybe beef up the payload with a bit of extra bang (and if you've got the lift, why not?) then a shuttle is basically the same as an ICBM.

Basically.

Re:No quite yet.

[Nefarious Wheel]

yes but if we use all the comets, where will we get the ice without bugs in it to cool the oceans to combat global warming?

I think we Oort to have enough.

Re:No quite yet.

[camperdave]

You're doing it wrong, then. Any thermal power you dissipate through cooling fins is power you should be dumping into your propellant.

Re:No quite yet.

[camperdave]

It still needs propellant. Rockets all work the same way, by throwing mass in the opposite direction to your desired direction of travel, and you have to bring that mass with you. It doesn't matter if the rockets are ion engines, hydrolox, kerolox, or Estes 1/4A model rocket motors. Chemical rockets use the byproducts of combustion as the propellant. Ion rockets (including VASIMR) use a store of a convenient gas, like xenon or argon, as their propellant. To make the trip from Low Earth Orbit to Lunar Orbit would require about eight metric tonnes of argon.

Re:No quite yet.

[Anonymous Coward]

Even if we make it there in your lifetime (unlikely), the infomration still has to travel back at light speed, so you'd probally never know what the sensors saw.

Re:No quite yet.

[ShooterNeo]

The reason for rocks is two fold : light and particle beams are subject to an inverse square law with distance. The spot size of the light or particle beam over a distance of light-years will quickly rise to the point that nearly all of the energy being beamed to your spaceship is wasted.

Re:No quite yet.

[ShooterNeo]

The receiving and shooting coil is the same coil. Or, rather, a linear series of coils...the spacecraft would be incredible long and would be mostly just a series of superconducting electromagnets.

To prevent collisions, when you fire the pebble back the other direction you steer it just slightly off axis so that it won't hit the incoming pebble. You cancel out the tiny amount momentum change by sending the next pebble slightly off axis the other way.

The cannon is a massive accelerator in our solar system. It stays stationary either by firing an identical pebble the OTHER direction each time it fires, or by being anchored to a moon or other large planetary body. (granted, it would slowly push a moon out of it's orbit, but that would not be a problem for a while. Yes, it would fire the pebbles faster or more often as necessary according to a pre arranged plan so that the starship could reach it's destination.

You can't hold on to the pebbles. Every time you catch a pebble using electromagnets, the momentum of the pebble is added to the momentum of your starship. That's the way the engine works :P

One alternate idea is to use matter/anti matter pebbles when you are decelerating.

Re:No quite yet.

[ShooterNeo]

The other reason for rocks is acceleration. Physical limits on how good your sail can be mean that the laser you use can only be so bright. This in turn limits the acceleration of your starship. Even though the starships I am proposing will never have human crew, the faster they reach the destination, the better. You don't want to wait for years just to get close to the speed of light. (I'm thinking 50%90% of the speed of light will be the target velocity you want to reach in order to make an interstellar journey)

If you are wondering, the 'crew' of the starship will be sentient beings running on molecular computers. They might be simulated versions of human beings, but would probably think in a manner quite different than humans. They will carry with them enough molecular tools to rapidly recreate the civilization that launched them at the destination star system.

Re:No quite yet.

[cheesybagel]

This is nuclear electric propulsion we are talking about here. Ever seen the designs for JIMO?

Re:No quite yet.

[physburn]

The article was about a 200Kilowatt drive, and yes the Mars drives, was nearer 20MegaWatt. Thats a lots of Solar Panels, so it would probably need an on board nuclear reactor. A reactor would still be a lot less weight than towing around 3 years worth of food.

---

Plasma and Ion Drive Feed Feed Distiller

Re:No quite yet.

[modmans2ndcoming]

the amps needed to power a 39 day trip would be generated from an on board nuclear reactor.

Re:No quite yet.

[modmans2ndcoming]

besides... they can build the ship in orbit and used a rail gun to heft the materials up there... including the power plant.

Re:No quite yet.

[Zerth]

Easy compared to doing it through a turbulent atmosphere from a fixed point on a spinning planet where the collimating optics can't be more than a few hundred feet from the source.

Re:No quite yet.

[camperdave]

Ah! I was thinking more along the NERVA/GCNR lines.

Re:No quite yet.

[drinkmorejava]

The speed of sound in space is not relevant, only the backpressure (pressure of the outside atmosphere) will matter. Mach 1 at the throat is calculated as sqrt(gamma*R*T) where T is in kelvin if R=287. Gamma will most likely be 1.4 and is pretty constant for ideal gases. T can vary greatly, but 3000K is around the right order of magnitude. Once flow hits the sonic condition, Bernoulli's principal switches, and you'll actually use an expanding nozzle to get a higher exhaust velocity. A cool thing to look out for are the plumes on the shuttle engines as it enters the upper atmosphere. These are due to a lower backpressure, and result in less efficient operation.

Re:No quite yet.

[drinkmorejava]

I'm not sure what formula you are using. The most simplistic thrust formula you'll see is T=me*Ue+Ae(Pe-Po) where Po is zero in space, m is the time derivative of mass exiting the spacecraft, and Ae is the area of the exit nozzle. This doesn't exactly apply to non-fluid mechanics though.

If you're slowing down the particles and generating a magnetic field, there's not necessarily any momentum transfered to the spacecraft. Kinetic energy can be exchange for a lot of stuff, heat, electric charge, and of course, an opposing force.

Re:No quite yet.

[camperdave]

You'd still have to get your charged particles from somewhere. That means bringing reaction mass with you.

Re:No quite yet.

[babymac]

This is exactly the idea behind the spacecraft featured in Mary Doria Russell's novel, The Sparrow. It's a pretty good read. One of the better SF novels I've ever read.

Re:No quite yet.

[khallow]

This latter kind of generator is pretty much infinitely scalable, as you say, but aren't so efficient for big power demands - most of the RTGs in the probes you mention provide a few hundred watts, even when new.

I thought that at one time too. But there's two obstacles, production of plutonium 238 or other appropriate isotope and the dissipation of heat from the RTG. Too much fuel in one place and it will melt due to the inability to carry heat away.

Re:No quite yet.

[CopaceticOpus]

Thank you! I will put it at the top of my to-read list. I've been thinking about this idea of asteroid-as-ejection-mass for quite some time, and it will be fun to read a novel on the subject.

Re:No quite yet.

[ShooterNeo]

Conservation of momentum is an absolute law of physics. You cannot ever violate it. You said you were a rocket scientist?

Re:No quite yet.

[rahultyagi]

hmmm... the problem is that for doing this you will also have to carry the whole asteroid with you. so, even though the thrust that will be provided by the ground asteroid should be enormous in totality, the acceleration it will provide will be mitigated to a large extent due to the necessity of accelerating the rest of the asteroid.

Then again, that is a problem with any rocket propellant/fuel... you take a lot of fuel and then propel it away, giving you some acceleration... you know what, never mind... that was a little stupid of me... the fact that you threw away the whole asteroid at the end, means that you gained that much momentum for yourself, regardless of how fast you threw the powdered substance away. I'll still post this, just in case someone else who, like me, has forgotten all physics might start wondering the same thing.

I wonder though, how much nuclear fuel would one have to carry to generate that much thrust? because, essentially the asteroid only gives you enormous amount of propellant to use, not fuel... to carry the amount of nuclear fuel that can propel essentially the whole asteroid away can't be a trivial problem!

Re:No quite yet.

[mcvos]

The reason for rocks is two fold : light and particle beams are subject to an inverse square law with distance. The spot size of the light or particle beam over a distance of light-years will quickly rise to the point that nearly all of the energy being beamed to your spaceship is wasted.

So how are you going to shoot rocks with greater accuracy than a particle beam? As far as I understand, a sufficiently long particle accellerator can be as accurate as you need it to be. And charged particles have the advantage that a mag sail can easily be very large. Which brings me to another question: how are you going to catch that beam of rock?

Re:No quite yet.

[mcvos]

You'd still have to get your charged particles from somewhere. That means bringing reaction mass with you.

No it doesn't. You take a big asteroid, build a big accellerator from one end to the other, and then shoot the asteroid's mass at the ship.

Re:No quite yet.

[mcvos]

I missed one detail from your post: nanoscale guidance and maneuvering systems. That'd probably work. For accuracy, that is. How you get nanoscale guidance and maneuvering systems to work is a different problem that you'll still need to solve.

Re:No quite yet.

[ShooterNeo]

Well, the PHYSICS clearly allow for it. We have extant examples of nanoscale sensors of all sorts. And since each rock is very small, just kicking off a few atoms would be enough to change it's course over a sufficiently long distance/time. For an interstellar trip, some of these rocks are going to travel for light-years before finally reaching the starship.

I think that any civilization capable of creating the linear accelerator millions of kilometers long, and packing sentience into molecular computers can probably solve the engineering problem of mass producing nanoscale pebbles with integrated guidance and maneuvering.

Re:No quite yet.

[ShooterNeo]

I mean, wormholes would of course be a ridiculously better way (you'd just fuel your starship through the wormhole, and of course once you get to the destination you have an instantaneous link between the two places). However, the laws of physics may not allow for them.

Re:No quite yet.

[Meumeu]

It's Mach 1 in the exhaust. But even if the flow won't go at more than Mach 1, the speed of sound is proportionnal to the square root of the temperature, so even if the Mach number is fixed at the throat, you can have a faster flow if you can get a hotter gas.

Of course the problem is that with any rocket engine, the gas are already hot enough to melt the nozzle: I've worked on Vulcain 2 and the nozzle is cooled with liquid hydrogen at 20K... I guess other rocket engines use similar solutions.

Re:No quite yet.

[Meumeu]

Mach 1 at the throat is calculated as sqrt(gamma*R*T) where T is in kelvin if R=287. Gamma will most likely be 1.4 and is pretty constant for ideal gases. T can vary greatly, but 3000K is around the right order of magnitude.

Uh? R=287 is true for air, with 29 g/mol, with pure water, it's 462, and more for the mixture of water and hydrogen that comes out of the nozzle.

Re:No quite yet.

[qc_dk]

I'm with mcrbids on this one, but it's some years since I studied relativity.

Of course the mass has to be measured in your frame of reference. As we near the limit of the speed of light(for the exhaust) your reaction mass would start to increase and therefore its impulse would increase. However the reaction mass is stationary in our frame of reference before entering the engine and will therefore have rest mass. The effect being that there is no limit to specific impulse.

... the usable energy in the fuel would be frame-of-reference dependent, which doesn't make a lot of sense.

Remember that we are simply talking propellant not fuel(It's the same in a chemical rocket, but not in engines like VASIMR). It's simply what we are throwing backwards to gain momentum. If we didn't take relativistic effects into account we would have a violation of the conservation of energy. Because we can pump however much energy we like into an exhaust particle, that must be translated into a similar increase in kinetic energy for our rocket and therefore a relativistic increase in momentum.

A perfect mirror in a solar sail would attain infinite specific impulse, since it's carrying no propellant.

In the end specific impulse isn't the only interesting measure. The problem is that it only covers the propellant. As mcrbids says: "as far as you have the ability to add more energy". We still have to find a way to bring this energy along, in a nuclear reactor or solar panels etc. And, we will have to scale up our energy generator as we scale up the energy spent on accelerating creating a limit on the rocket's efficiency.

Re:No quite yet.

[Anonymous Coward]

Based on my "gut feeling", I'd say that there isn't any such limit, because as you approach the speed of light, the mass of the propellant rises with unlimited potential. (if a particle with mass were travelling at the speed of light, its mass would be infinite) Thus you can continue bundling ever-more energy into your propellant, and specific impulse would continue to increase, for as far as you have the ability to add more energy....

It makes sense to me, but is this right?

Alas, no. You see, with velocity increase relativistic time dilation slows down rate of any "relativistic rocket engine" on-board process used for mass-spewing for exactly the same factor as its mass is increasing, thus keeping its dm/dt constant. At best, specific impulse would remain the same, but we haven't even taken into account relativistic formula for velocity addition, to calculate the resulting exhaust speed. The crew of the ship would see the craft steadily increasing its proper velocity up to infinity, but the observers (mission control, general TV audience) would see its acceleration stagnate as it picks up the speed.

Re:No quite yet.

[Rising Ape]

Of course the mass has to be measured in your frame of reference. As we near the limit of the speed of light(for the exhaust) your reaction mass would start to increase and therefore its impulse would increase. However the reaction mass is stationary in our frame of reference before entering the engine and will therefore have rest mass. The effect being that there is no limit to specific impulse.

That makes sense, although it reinforces my belief that "relativistic mass" is confusing and pointless. There's no limit to the momentum with which a given amount of propellant can be ejected, providing some external energy source is provided, as momentum = gamma * mass * velocity.

If you can only use what you can carry as an energy source, the best you can do with the mass you can carry is what I said - carry antimatter, annihilate it down to massless particle such as photons and use those annihilation products as propellant. We're a long way from being able to do that though.

Re:No quite yet.

[qc_dk]

If you can only use what you can carry as an energy source, the best you can do with the mass you can carry is what I said - carry antimatter, annihilate it down to massless particle such as photons and use those annihilation products as propellant. We're a long way from being able to do that though.

If you insist on bringing your fuel with you. But that might not be necessary. You could use solar power if you were only going places near a star.

The problem with antimatter(well besides making the antimatter and a bunch of other practical probems :-)) is that you cannot control the annihilation and be sure to get photons, sure its the first order reaction in low energy scenarios, but not the only one. So you will also get muon pairs etc. You could also just carry the anti matter, and then scoop up the matter you needed from space as you were flying along, effectively doubling the specific impulse of the antimatter rocket

Re:No quite yet.

[doug]

Technically speaking VASIMR, like ion propulsion, is electrically powered. For it to be constant thrust it would need to have that electricity generated by a nuclear reactor. Since solar power decreases as an inverse square law, a solar powered VASIMR would not be constant thrust.

s/constant/continuous/

The idea is that there is ongoing thrust, as opposed to burn then drift. Even if the additional thrust is small, it adds up over time.

- doug

Re:No quite yet.

[TheCarp]

You could get inexpensive astronaut standins. Maybe put some dirty telephone handsets on the shuttle and lock the door when the telephone handset cleaners go in....

-Steve

Re:No quite yet.

[Impy the Impiuos Imp]

What about Canada?

From TFA;

> "A whole bunch of countries (were involved), but Canada has one of the main pieces
> of hardware. And this engine can get us to Mars in 39 days.

Yay Canada! Finally something to brag about besides "the arm"!

Re:No quite yet.

[lennier]

"In theory, you could use a small glass of water, accelerated to a significant fraction of the speed of light, as your propellant for an entire trip to Mars and back."

Plus, it makes an entertaining practical joke when someone on board gets thirsty!

However it's more traditional to use a small piece of fairy cake for this purpose.

Re:No quite yet.

[Anonymous Coward]

The r^2 law is for a uniform omnidirectional radiator, and is usually thought of in terms of W/Sr.

Sr is steradian, which is the solid angle subtended at a given radial distance from the centre of a sphere, that is, it is to the surface of a sphere what a radian is to the circumference of a circle.

If power is uniform in 3 spatial directions, W at radius r spreads out to W/r^2, which is the inverse square law.

Directional radiators focus power such that the second term is a much smaller area than the square of the radius. A highly collimated beam of light through free and flat space will stay highly collimated rather than spreading out.

Interplanetary (r >= 1 AU from Msun) and interstellar space between Earth and nearby stars is sufficiently flat to ignore general relativity (spacetime curvature terms are dominated by those arising close to the emitter, especially if it's on or near Earth).

There is quite a bit of dust and gas that may serve to reflect, refract, absorb, reemit or scatter a high frequency light beam, however, which may pose some aiming problems. It's true that this becomes more difficult the radius increases (the solid angle of the beam target (i.e., the "sail") decreases as the square of the radius), but if we can solve this in part by not using a single-wavelength source.

You could jokingly call this "Heisenberg compensation", but you can mitigate some of the uncertanties of the off-axis position of the target by introducing some uncertainty in its axial momentum and that of the photons -- in extremis, use extremely low-frequency photons that will almost certainly interact with the distant probe; alternatively you can "wiggle" the directionality of the beam at the source and intercept the distant probe only statistically but with a single photon frequency.

Generally you want to launch a collimated beam of photons with a maximum momentum transfer potential. If you have a gamma or x-ray mirror for the target sail, use it! p = h/\lambda where h is the Planck constant and \lambda is the wavelength of the photon striking the mirror,

There may be a non-negligible Lorentz redshift from gravitational time dilation depending on where in the solar system the beam emitter is, and a further redshift from special relativity if the target has a high recession velocity.

Note that for braking and returning you can use the source beam to power an outgoing beam (or to heat a shielded blackbody radiator), with E = pc, and p recovered from the incoming beam.

Re:No quite yet.

[TheRaven64]

So close, but the fairy cake was used for the total perspective vortex. A cup of tea was used as a brownian motion source for the improbability drive.

Sound

[whisper_jeff]

But does this process create feedback over communications systems to create cool sound effects as the ship whooshes by?

Sorry. Star Wars geek moment...

Re:Sound

[Jeng]

My thoughts on why one hears other spaceships around in sci-fi movies is that their propulsion pushes directly off of space time which creates waves which one can hear when they hit the side of the spaceship.

Re:Sound

[isaac]

But does this process create feedback over communications systems to create cool sound effects as the ship whooshes by?

Quite possibly, actually; at the very least, there might be enough radio emissions at audible frequencies as the plasma dissipates in the presence of a magnetic field (i.e. planetary orbit) to induce something audible in a speaker wire or analog amplifier. It's been speculated that such a mechanism is responsible for the phenomena of hissing, whooshing, or popping sounds heard simultaneously with the appearance of meteorites passing through the atmosphere (as opposed to delayed like a sonic boom.)

-Isaac

Re:Sound

[MobileTatsu-NJG]

My thoughts on why one hears other spaceships around in sci-fi movies is that their propulsion pushes directly off of space time which creates waves which one can hear when they hit the side of the spaceship.

Ah. That explains the John Williams score we hear in space, too.

Re:Sound

[mlush]

I've always assumed the whoosh was synthesized by the ships systems as a audio representation of the local battlespace

Re:Sound

[tsm_sf]

If they don't have an audio representation for silent space battles, someone always ends up piping 'Blue Danube Waltz' over the ship's PA.

Re:Sound

[Jeng]

Oddly the ricers of the future may just modulate their engines so that one hears a John Williams score as they pass by.

Re:Sound

[Anonymous Coward]

Only if the Linux running the ship is equipped with PulseAudio :-P

Re:Sound

[mlush]

That or some joker changes the audio skin for 'Toontown'

Re:Sound

[rbanffy]

Actually, depending on what frequencies you use for communication, you may hear the engine very clearly. Unfortunately, unless it passes by at really high (close to c) speeds, you will get no doppler pitch change.

Re:Sound

[EvilTwinSkippy]

Or Blur's "Song #2"

Re:Sound

[Zencyde]

That's my favorite song to kill to!

Re:Sound

[Captain Jameson]

Sorry.

Re:Sound

[SleazyRidr]

That's the way they explained it in a space-invaders style game I used to enjoy. Thanks for reminding me of it: 'Tyrian'.

Re:Sound

[kimgkimg]

Yes, but what about the re-modulated tachyon generators?

Re:Sound

[camperdave]

It was a storytelling device in Space 1999. When they showed a space ship on the monitor, there was silence. When there was sound, it meant that the audience was viewing the events "in person".

Re:Sound

[Anonymous Coward]

Quite possibly, actually; at the very least, there might be enough radio emissions at audible frequencies as the plasma dissipates in the presence of a magnetic field (i.e. planetary orbit) to induce something audible in a speaker wire or analog amplifier.

Um, does that also mean no radio communications with the ship while engines are on? I mean, I see no reason why the effect would be contained in AF part of the spectrum.

Re:Sound

[OwMyBrain]

Sorry. Star Wars geek moment...

But I want to know in how many Parsecs VASIMR can do the Kessel run!!!

I'm dizzy.

[garcia]

From the article:

A new NASA rocket engine, designed partly in Canada, raises the revolutionary possibility that a manned trip to Mars could take less than three months instead of two years.

[...]

It would take about 39 days to reach Mars, compared to six months by conventional rocket power.

In three paragraphs we go from 89 days to 39 days. So which is it? With that kind of difference, I'm not quite sure it would be any faster than conventional rockets.

Re:I'm dizzy.

[ageoffri]

39 * 2 = 78 days for round trip to Mars in the article which is less then 3 months. The 39 days is one way just to get there.

Re:I'm dizzy.

[Michael_gr]

They will have to get back, won't they? 39 days one way, 39 days the other way, ~10 days on Mars.

Re:I'm dizzy.

[ircmaxell]

89 days for a round trip mission. 39 out, 11 in orbit, 39 back...

Re:I'm dizzy.

[garcia]

Thanks everyone. I'm dumb. I blame the 800 miles of driving in the last 24 hours.

Re:I'm dizzy.

[click2005]

You could have travelled those 800 miles in 4 hours with a VASMIR Ion Drive.

Re:I'm dizzy.

[Anonymous Coward]

your math sucks.

Re:I'm dizzy.

[DoofusOfDeath]

In three paragraphs we go from 89 days to 39 days.

It's called acceleration. Duh...

Re:I'm dizzy.

[MoobY]

You're confusing going one-way and the whole trip. Go to Mars = 39 days, stay at mars = 10 days, come back to earth = 39 days, total = about 3 months.

Re:I'm dizzy.

[wren337]

From the article:

A new NASA rocket engine, designed partly in Canada, raises the revolutionary possibility that a manned trip to Mars could take less than three months instead of two years.

[...]

It would take about 39 days to reach Mars, compared to six months by conventional rocket power.

In three paragraphs we go from 89 days to 39 days. So which is it? With that kind of difference, I'm not quite sure it would be any faster than conventional rockets.

Round trip. Less than three months round trip, 39 days each way.

Re:I'm dizzy.

[DJProtoss]

Eh? more like under a minute actually. (couldn't see any particular speed figures, but assuming mars earth distance is ~5.5x10^10m, and assuming perfectly linear accel / deccel (which in space ain't that wrong I guess), you get a deltav of ~1.7x10^3ms^-2, now given his trip was only under 1.3x10^6m, using good old a level mechanics that gives you a time of just under 40s...*

*of course, this assumes vast amounts of stuff, including no air resistance and instant change from accel to deccel, but hey.

Re:I'm dizzy.

[gEvil (beta)]

He's clearly taking the Interplanetary Date Line into account in his calculations.

Re:I'm dizzy.

[Anonymous Coward]

except in 78 days, the earth will have completed 21.% of its orbit of the sun...

Re:I'm dizzy.

[Aceticon]

I think they mean 39 work-days, 89 days in total.

Obviously the engine will not work on weekends, so that's 2 days out of 7, roughly 24 in total.

Then there are religious holidays for the astronauts, not to mention national holidays for each nationality represented in the team. I reckon that's about 3 days a month, or roughly 9 days in total.

Then there's mandatory vacation time, about 25 days a year or roughly 8 days for the trip.

Assuming everybody is working really hard, coffee, cigarette and bathroom breaks will probably only add up to 3 days in total.

Of the remaining 45 days, one is preparation before the trip, one to really get going and one is basically wasted on the whole "arrival, get the luggage out and unpack it". Same thing on the Mars side. That's another 6 days.

This is the reason for the difference.

Re:I'm dizzy.

[operagost]

Cigarette breaks? Ridiculous. With the new Obama tax on tobacco, they're too expensive on the average astronaut's salary.

Re:I'm dizzy.

[Canazza]

It'll average 0.02% of c, that's about 134123mph, so to travel 800 miles would take 21.47 seconds

Re:I'm dizzy.

[TheRaven64]

Depends on how much he weighs. The drive provides a force of 0.5N. A typical car plus passengers masses around 1000kg. F=ma, so, 0.5 / 1000 gives him an acceleration of 0.0005 m/s/s (ignoring friction and air resistance). 800 miles is a little under 1,300 km, or 1,300,000m. Assuming a stationary start, and accelerating for the whole time, we get sqrt(2s/a), which is around 51,000 seconds, or around 14 hours. Of course, after that time he'd be going quite quickly, so he'd probably want to be slowing down for the second half of the journey which increases the total travel time to about 20 hours.

Ion drives are not (yet) fast. They provide a much lower acceleration than conventional rockets, which is why no one is talking about using them to get to orbit. They use a lot less propellant to produce this thrust than an equivalent chemical rocket though, which means that they can provide this thrust for longer. After 14 hours, the car would be going at 25m/s. Not particularly fast; a chemical rocket can get to that speed in a couple of seconds. After a week it would be going at over 300m/s, which is a lot more respectable.

Your distance from earth to mars looks sensible, and makes the average speed 16.3km/s. Assuming linear acceleration and deceleration (which is incredibly wrong when we're talking orbital mechanics, because this would be a transfer orbit so you'd actually be accelerating for most of it), that would mean that the top speed would be 32.6km/s and you'd spend half of the time accelerating to this speed and half slowing down from it. That gives a delta v of just under 0.02m/s/s, which means that either they have more than one ion engine on the craft, or they are using something that weighs a lot less than a car. At that acceleration it would take just over 3 hours to travel 800 miles, which is close to what the grandparent said. I'm not sure where you get your 1.7km/s/s from, but I I think you dropped a 'k' somewhere in your calculations.

Re:I'm dizzy.

[JWSmythe]

    Are your numbers off on the excuse too? You averaged 33.34mph? A 800 mile highway trip should be easily accomplished in 13.3 hours, considering 3 fuel stops. If it was 400 miles each way, that wasn't the best plan, to drive 6 hours to spend 12, and turn right around. Always leave relaxation time at your destinations. :)

Re:I'm dizzy.

[JerryLove]

That assumes a lot. The return trip could be an entierly different amount of time than the departure trip.

It depends on the path that needs to be taken and the involved DeltaV.

Re:I'm dizzy.

[CrimsonAvenger]

Depends on how much he weighs. The drive provides a force of 0.5N. A typical car plus passengers masses around 1000kg. F=ma, so, 0.5 / 1000 gives him an acceleration of 0.0005 m/s/s (ignoring friction and air resistance). 800 miles is a little under 1,300 km, or 1,300,000m. Assuming a stationary start, and accelerating for the whole time, we get sqrt(2s/a), which is around 51,000 seconds, or around 14 hours. Of course, after that time he'd be going quite quickly, so he'd probably want to be slowing down for the second half of the journey which increases the total travel time to about 20 hours.

"quite quickly"? He'd be going (using your approximations) about 25.5 m/s. Which is only about 92 km/hour (57 miles per hour for those who don't do metric). He should be able to stop just fine with normal brakes in just a hundred feet or so.

Re:I'm dizzy.

[rossdee]

Maybe it depends on the orbital positions of both planets, there can be quite a difference in travel times.

Re:I'm dizzy.

[TheRaven64]

Yup, I wrote that before calculating exactly how fast. Of course, in a hypothetical world where friction is low enough that you could use a 0.5N ion engine on the ground, your brakes probably wouldn't work so well...

Re:I'm dizzy.

[2short]

"In three paragraphs we go from 89 days to 39 days. So which is it?"

Either estimate is based on using a non-existant upscaling of an engine whose much smaller proto-type is scheduled for testing maybe 4 year from now. An of course, attaching that engine to an entirely unspecified payload. So really, who cares if it's 89 or 39? Anyone making such a specific estimate at this point is making stuff up, almost certainly to push some agenda.

Re:I'm dizzy.

[Adm.Wiggin]

Somebody mod these guys "Funny" for taking it so far. Good show!

Re:I'm dizzy.

[gnieboer]

Another main reason for the length of time involved is the orbital dynamics of the positions of the two planets. There is a astro concept called a Hohmann Transfer (http://en.wikipedia.org/wiki/Hohmann_transfer_orbit), which is a specific impulse efficient way of moving from one orbit to another. But it takes time, and requires waiting until the bodies are in the right position before we do it.

So you end up having to hang around on Mars for several months.

Going just a -little- bit faster doesn't gain anything because then you just have to wait longer for the planets to align.

Since this proposes something vastly quicker, the comment in the article about being able to do it in one planetary pass is what makes the 89 days possible. Requires tons more delta-V to do an orbital transfer this way, but the amount we'd save on human sustainment would more than make up for it.

Of course, not sure yet about hauling the nuke reactor into space...

Re:I'm dizzy.

[dzfoo]

Uh, 39 days is still less than 3 months.

        -dZ.

Re:I'm dizzy.

[Anonymous Coward]

The Hohmann paths are the two-year estimate, I think. Using those, you only thrust to get just over the tipping point between two gravity wells; the rest of the time, you're "falling" unpowered towards somewhere. That's why they're so fuel efficient-but-slow.

The 39-89 day estimates are for more direct paths with long burns. (Continuous thrust, using WASIMR). So those will vary based on the engine and how much mass you send and the relative positions of Earth and Mars. I assume we'd time the mission to leave Earth a few months before the closest alignment and leave Mars a few months after, to minimize the round trip time, but spending a longer time at Mars could dramatically increase the travel time.

Re:I'm dizzy.

[suomynonAyletamitlU]

I called the interplanetary date line, but apparently nobody out there is interested in dating me...

Re:I'm dizzy.

[zippthorne]

Orbital mechanics does not work like that.

Re:I'm dizzy.

[Nefarious Wheel]

Anyone making such a specific estimate at this point is making stuff up, almost certainly to push some agenda.

Perhaps, where Agenda=[intent to work a problem]. Add theory, speculation, a white board (or electronic equivalent), intelligent and learned people, a refining dialogue for long enough and you end up with science. The real thing, that you can prove independently and predict with. It was people discussing the problem that allowed us to ultimately find out what our neighboring planets are made of. You start with rough figures, rough methods, and you refine them until you have a set of workable orbital parameters in combination with a mechanism and method for acquiring them.

Or did you think it all came out of a magic book somewhere? Don't diss the dialogue mate.

Re:I'm dizzy.

[2short]

Yes, obviously I though Science came out of a magic book, that's why I was dissing dialogue...

Wait, no. Actually, I was complaining about people entirely making shit up in order to push the idea that what they work on is a good idea. Agenda=[fund my research, not some other research]

Saying this drive technology will make a mission to Mars take 39 days isn't a rough figure; it's meaningless. It's like estimating the time to move across town using wheels without specifying what you're moving or whether the wheels are attached to roller skates or a semi. And you've though about wheels a bunch, but never used one yet. It's not the start of a scientific dialogue. It's marketing.

Add theory, speculation, a whiteboard, and massive amounts of government funding, and some researchers will have a nice career. They might even do something worthwhile, but that's not the objective served by the guy saying "39 days".

Re:I'm dizzy.

[bondsbw]

The 39 days takes into account that fact. And remember, in 78 days Mars will have also completed 11% of its orbit, in the same direction.

Mars and Earth will be at their closest approach exactly halfway through the mission. If it were a single-pass mission, that would also be the time that the spacecraft was closest to Mars and farthest from Earth.

Re:Tag as SLASHVERTISEMENT

[Anonymous Coward]

Yeah, I was totally going to go for one of those conventional rockets for my trip to Mars, but now I'm seriously considering a VASIMR Ion Engine.

Re:Tag as SLASHVERTISEMENT

[dkleinsc]

Yeah, coverage like this really makes we want to go out and buy one for my own space ship.

Seriously, I think this might be getting coverage because this is potentially technology that could make a manned mission to MARS much more feasible and safer. Of course, getting back might still be challenging, but I for one would take the honor of being the first man on Mars away from Philip Fry if I could.

Please, please, PLEASE...

[Kirin Fenrir]

Let the common name be "impulse engines".

Re:Please, please, PLEASE...

[John Hasler]

All rockets are "impulse engines".

Re:Please, please, PLEASE...

[confused one]

Impulse engines have fusion reactors at their core, or so I read. While VASIMR borrows technology from fusion research, You'd need to change the fuel used, change the shape of the magnetic confinement, and increase the energy input of a VASIMR engine many orders of magnitude, in order to reach that point. So, a totally new design...

Re:Please, please, PLEASE...

[Hal_Porter]

You'd also have to be living in a Universe with Star Trek physics.

Re:Please, please, PLEASE...

[Anonymous Coward]

Also, instead of "Lift off," please say "FULL IMPULSE POWER!"

Re:Please, please, PLEASE...

[confused one]

Well, yeah. I tried to keep it simple (only refer to the fusion reactor) and leave out the Star Trek physics (like the FTL acceleration of the exhaust plasma)

Re:Please, please, PLEASE...

[confused one]

There is a concept which saw some development in the '90's, which paralleled the VASIMR work: Gas Dynamic Mirror Fusion Propulsion

Can it be used for ISStation keeping?

[wisebabo]

Anyone know if there is enough thrust to counteract the drag the ISS has in the extremely thin atmosphere up there?

Does the running of the ion engine cause adverse effect to any of the delicate instrumentation on board? Does it mess up any electric/magnetic measurements?

Is the power draw too great for it to be used in this fashion?

(TFA says "there are plans" to use it in this fashion but nothing beyond that).

*application of Niven's law: is there any way to make it into a beamed energy weapon against "soft targets" like other satellites in LEO?

Re:Can it be used for ISStation keeping?

[Anonymous Coward]

LOL, if it can push a rather large ship out of Earth's orbit, it can keep the ISS in orbit. The one that is being sent up is rather on the small side though. There was mention in one of the articles about it recently that it could be used for station keeping however.

Bear in mind that it requires a power source for all the energy expended in heating and controlling that plasma, shich in this instance would have to come frrom the station's solar panels. That kind of energy draw was never considered in the original design.

Re:Can it be used for ISStation keeping?

[Anonymous Coward]

I tend to doubt it. Ion drives have extremely low thrust. It's their efficency that makes them interesting. Everything I ever read considered them only practical outside both atmosphere and a planet's gravitational field. They really excel in interplanetary or even interstellar space. Keeping the ISS in orbit isn't hard it's having the will and the cash to do it. An ion drive would limit the number of trips if it would work but it would still take transporting it to the ISS and the weigh would be the same as a lot of fuel.

Re:Can it be used for ISStation keeping?

[GordonBX]

That's the whole point of this type of engine - it's not your traditional ION drive which has very low thrust but high specific impulse. VASIMR has relatively high thrust - not enough to travel through the atmosphere, but high enough to be used to shove the ISS up to a higher orbit.

Re:Can it be used for ISStation keeping?

[Anonymous Coward]

LOL

No you didn't. We need to abolish that "word".

Re:Can it be used for ISStation keeping?

[TheRaven64]

LOL, if it can push a rather large ship out of Earth's orbit, it can keep the ISS in orbit.

One does not follow from the other. It can provide a thrust of about 0.5N. It could not, for example, lift itself off the ground. It could not, if you were in orbit and pointed it at the ground, break you out of orbit. It can, if you are in a sufficiently high orbit not to be subject to atmospheric drag, accelerate you such that your orbital period increases and eventually you fly out of orbit. If the atmospheric drag on the ISS exceeds 0.5N, then this engine could not keep it in orbit.

Re:Can it be used for ISStation keeping?

[Tekfactory]

With trickle charge batteries the VASIMR will be fired for 10 minutes at a time. The Drive will be using 200 kW which is more than the ISS Solar Array can produce continuously.

According to papers from AdAstra the engine is supposed to deliver 5 Newtons using Argon as a fuel.

The 200 kW tests were important because they meant the engine could sucessfully lift the ISS. The previous motor which used 100 kW coud only create 1 Newton of thrust.

Re:Can it be used for ISStation keeping?

[GigsVT]

It could not, if you were in orbit and pointed it at the ground, break you out of orbit.>

You're doing it wrong. Google prograde burn.

Re:Can it be used for ISStation keeping?

[TheRaven64]

You mean, the thing I described in the sentence immediately following the one you quoted?

Needs serious power input for fast travel

[Anonymous Coward]

Mind you to obtain this 39 day route, you're not going to be doing it by feeding the VASIMR's klystrons off solar cells stuck to the outside of the ship. That's more of a one year sort of trip.

If you want the 39 days, you're going to need to pump the voltage in with a classic onboard nuclear reactor. Not to worry though, both the US and Russians made and tested (The Russians flew) several dozen types of space borne fission reactors in the 60s-80s so this is no great leap. Other than perhaps getting the eco-hippies to shut up about lofting lots of highly enriched nuclear fuel.

Re:Needs serious power input for fast travel

[Anonymous Coward]

Hey How about a small Fussion Reactor? As reported on shashdot they are starting testing it now. http://science.slashdot.org/story/09/10/18/1652201/A-Step-Closer-To-Cheap-Nuclear-Fusion

Re:Needs serious power input for fast travel

[__aahsjj4927]

Is it possible to enrich the stuff in space?

Re:Needs serious power input for fast travel

[khallow]

Nuclear power in space is very much a dead end. You don't need to be an eco-hippy to see that. People don't like it, politicians and managers don't like to take the responsibility, you can't make money from it, it gives no spin-offs, you'll never have private companies involved: it's a single-purpose, money wasting government exercise. SF from the past, not more.

And it's a key technology for opening up the Solar System to us since it is a compact power source which doesn't depend on sunlight to provide power.

Comment removed

[account_deleted]

Comment removed based on user account deletion

"A new NASA rocket engine"

[Sumbius]

"A new NASA rocket engine" Is VASIMIR really all that new technology. It has been in development for quite a while now, and has gotten quite much publicity in the past few years or so. Also, correct me if I'm wrong, but ain't VASIMIR developed private company, not by NASA? Sure, NASA is working together with Ad Astra Rocket Company, but does NASA really deserve all the fame? Anyway, I truly hope that we will be sending a man in Mars in the upcoming years and I think that VASIMIR os one of the best ways of doing so. The problem is that Mars has always seemed to be just a bit under decade away for quite a long while now...

Re:"A new NASA rocket engine"

[John Hasler]

> Also, correct me if I'm wrong, but ain't VASIMIR developed private company,
> not by NASA?

Who is paying for it? Who is going to buy it?

Re:"A new NASA rocket engine"

[sh00z]

Also, correct me if I'm wrong, but ain't VASIMIR developed private company, not by NASA? Sure, NASA is working together with Ad Astra Rocket Company, but does NASA really deserve all the fame?

This started as a NASA project, at the Advanced Space Propulsion Laboratory at the Johnson Space Center.

Dr Franklin R. Chang Diaz (the other former astronaut involved, and not mantioned in this Canada-centric article) took the project to private industry in 2005

Re:"A new NASA rocket engine"

[WindBourne]

NASA has paid solely for it. I suspect that a number of countries will be trying to buy it. Others will try to steal it.

Re:"A new NASA rocket engine"

[rbanffy]

I was going to buy it, you insensitive clod

Re:"A new NASA rocket engine"

[Zvezdanaut]

Actually, this was started as a private project. Dr. Chang Díaz has been working on some form of concept/design since his graduate school days at MIT in the late 70s. See the Ad Astra site. "Dr. Chang Díaz invented the VASIMR® concept and has been working on its development since 1979, starting at The Charles Stark Draper Laboratory in Cambridge Massachusetts and continuing at the MIT Plasma Fusion Center before moving the project to the Johnson Space Center in 1994. In the development of the VASIMR® engine, Ad Astra Rocket Company was teamed with NASA JSC, Oak Ridge National Laboratory, University of Texas at Austin, University of Houston and other various government space and research centers, industrial companies and academia including foreign universities." Ad Astra subsequently went private again on January 14th, 2005.

ion cannon

[meow27]

deos this mark 1 step towards making the ion cannon?

Re:ion cannon

[Anonymous Coward]

Y .. you thinking of defending the ice planet Hoth?

Re:ion cannon

[Anonymous Coward]

Perhaps... but until then, nobody stands in Kane's way!


Peace Through Power!
Long live the Brotherhood!

Name

[Anonymous Coward]

If they were going through the trouble of registering the name they should have gone with something more speak-friendly then VASIMR. Besides that, this name reminds me of vasectomy which is not the best of thoughts.

Actually...

[denzacar]

It already is.

But will it break the warp barrier?

[ThorofAsgard]

If not then the Vulcans won't come down and make First Contact!

Re:But will it break the warp barrier?

[FauxPasIII]

Yeah, but we've got til April of 2063, and we've still got a nuclear world war to contend with between now and then. =/

Re:But will it break the warp barrier?

[Hal_Porter]

Let's get the nuclear war out of the way first, then we can work on the warp drive.

Re:But will it break the warp barrier?

[Anonymous Coward]

I think I'd rather be safely off the planet, with a thousand females. For breeding.

Re:But will it break the warp barrier?

[Anonymous Coward]

Artificial insemination could save the human race in that situation, you are correct.

You'd be so important that you would be kept away from all dangers, including the women, and milked daily for such artificial insemination needs.

Indeed, they'd probably "pre-milk" you, so they could put 1001 females on that spaceship.

Re:But will it break the warp barrier?

[amliebsch]

Who needs to be off-planet?

Terrestially, I would not rule out the chance to preserve a nucleus of human specimens. It would be quite easy... at the bottom of ah ... some of our deeper mineshafts. The radioactivity would never penetrate a mine some thousands of feet deep. And in a matter of weeks, sufficient improvements in dwelling space could easily be provided.

It would not be difficult....Nuclear reactors could provide power almost indefinitely. Greenhouses could maintain plantlife. Animals could be bred and slaughtered. A quick survey would have to be made of all the available mine sites in the country. But I would guess... that ah, dwelling space for several hundred thousands of our people could easily be provided.

It could easily be accomplished with a computer. And a computer could be set and programmed to accept factors from youth, health, sexual fertility, intelligence, and a cross section of necessary skills. Of course it would be absolutely vital that our top government and military men be included to foster and impart the required principles of leadership and tradition. Naturally, they would breed prodigiously, eh? There would be much time, and little to do. But ah with the proper breeding techniques and a ratio of say, ten females to each male, I would guess that they could then work their way back to the present gross national product within say, twenty years.... I hasten to add that since each man will be required to do prodigious... service along these lines, the women will have to be selected for their sexual characteristics which will have to be of a highly stimulating nature.

Can this be the primary engine of a space shuttle?

[asliarun]

Noob question: IIRC from an earlier thread on this subject, this is supposed to be a high-efficiency but low-thrust engine as opposed to say, conventional rocket engines that are the opposite. I guess this would allow the VASIMR engine to provide sustained acceleration over a long period of time. Does this imply that this would be paired with a rocket engine and would kick in when the rocket is spent? In other words, do the basic characteristics of this engine force it to be only used as an additional engine or is it capable of being the one and only engine of a space shuttle?

Primary power source?

[JSBiff]

So, it appears that the VASIMR page shows a diagram where an external power source is applied to the engine (I presume in the form of electricity). Are there any electrical generators currently in existence which would be suitably compact and low enough mass, while at the same time generating sufficient power, to actually power this thing (basic physics tells me that no matter what propulsion method you use, energy is energy, and it takes a LOT of energy to generate large accellerations)? Or is this engine gonna have to sit on the shelf after being developed, while we figure out how to power it?

I suspect this thing would need some sort of small/light power generator that can produce a GW or more of power. So, do we need to first perfect fusion power before we can actually use this engine?

Re:Primary power source?

[Guysmiley777]

You hit on exactly the problem people don't discuss with ion engines. They require a source of electric power. The Deep Space 1 probe used solar panels, but it only has 2.5 kW of electrical power available. Large engines would take hundreds of kilowatts, more than any solar array could provide and be of a practical size. Maybe a nuclear fisson power supply? But that would add a huge amount of mass and volume to the spacecraft. Not to mention how up in arms some people get when you talk about launching nuclear material into space.

Re:Primary power source?

[confused one]

They usually discuss using it with solar arrays for near Earth use and with nuclear reactors on the order of 10-100MW for Mars and outer solar system.

Re:Primary power source?

[wisty]

You can point a great big space laser at them (from space station with a big array of solar panels), but the crew might get a bit nervous.

Re:Primary power source?

[Professeur Shadoko]

No, you cannot.

Do you know that the laser used to measure the distance between the earth and the moon has a radius of over 6km when it reaches the moon, and that only one photon every few seconds comes back to the detector on earth ?

Considering how far the spaceship will be from earth, it is not even remotely possible to focus a beam precisely enough to transfer energy.

Re:Primary power source?

[poopdeville]

WARNING: Do not look at moon with remaining eye.

Re:Primary power source?

[TheDarkMaster]

We can combine the ideas. Launch the reactor with or without the ion engine. Launch the crew section, after that the ion engine section or the remaining equipament (if the ion engine is already attached to the reactor section). Dock then all into a one big ship and then set the course to your favorite planet using the low but constant impulse. Maybe will be possible even to get to reality the project Pegasus from BBC

Re:Primary power source?

[Zerth]

Why would you put the laser on earth and have to deal with the havoc the atmosphere would do to accuracy and spread?

Stick the laser in space, where you can have an enormous collimating lens at a significant distance from the laser if it is still too divergent.

Re:Primary power source?

[joh]

The point is that solar panels in zero gravity (and at very low accelerations) can be made nearly as lightweight as you want to make them. It's just plain engineering. It may be hard to do, but there is no physical reason you couldn't spread out square miles of solar panels out in space. This is very different from chemical engines which are already pretty close to their physical limits. We are in no way near such limits with solar panels. Treating the sun as a large fusion reactor beaming power at you and harvesting as much of this power as you can could well be a working approach in the long run.

Re:Primary power source?

[John Hasler]

> Maybe a nuclear fisson power supply? But that would add a huge amount of mass > and volume to the spacecraft.

Fission reactors can have extremely high power to mass ratios: so high that, except for the political problems, a thermal rocket using hydrogen for reaction mass and a fission reactor for power would be one of the most cost-effective routes to LEO. The designs are quite straightforward and were done (and partially tested) in the seventies. The Soviets actually launched some spy satellites that contained small fission reactors for power: they worked fine and provided more power per kg than solar cells would have. The US designed several reactors intended for satellites and interplanetary spacecraft (that's reactors, not passive thermal generators) but never deployed any due to political pressure.

The ISS is seriously deficient in not having a reactor.

made in Webster, TX

[boristdog]

Hooray! Now maybe Webster, TX will be know for something other than being a speed trap between NASA and I-45.

Re:made in Webster, TX

[ColdWetDog]

Hooray! Now maybe Webster, TX will be know for something other than being a speed trap between NASA and I-45.

A wet, muddy, mosquito infested speed trap between the JSC and I-45, perhaps. Not bloody likely anything else ...

Re:made in Webster, TX

[guyminuslife]

With the new offramp from I-45 to Nassau Bay, I didn't realize it was still known for anything. ;-)

Re:Tag as SLASHVERTISEMENT

[wisty]

And in 12 months time, Richard Branson will probably have one.

Well

[MistrX]

With all other news that comes as to be a 'breaktrough' in some field: First see then believe.
And I see it when flight plannings are altered.

Exactly wrong!

[starglider29a]

At least from the "perception" angle. This is NOT the impulse engines from Star Trek. You can't limp to another star system on it. It doesn't fit nicely into the back of the saucer.

Having an efficient engine is great (when it gets here), but having 10-fold better efficiency mean you need ONLY 1/10 the amount of propellant. Propellant to accelerate you "halfway", propellant to decelerate you halfway... OK, then more propellant to accelerate you back home, then more to decelerate you as you approach earth. And that "few hundred newtons of thrust" won't accelerate/brake the ship very quickly.

You are still talking a Saturn V worth of Argon to get you to Mars and back. Think about 2001's Discovery. That spine was propellant tanks. Full.

How are you going to lift the ship? Space elevator?

And I haven't even asked how you are going insert back into earth orbit. Atmospheric re-entry from the Moon was very tricky. And we were only falling from 1/4 million miles.

Re:Exactly wrong!

[Vanderhoth]

Why does the ship have to come back to earth? Couldn't you just worry about getting it into space, then leave it there and have a secondary mode of transport to get people to and from the ship?

If we had a space station dedicated to constructing and maintaining ships in space, we'd only have to get the required ship building materials there. Not that this would ever happen in our lifetime. We can't make it to other solar systems to explore planets we could potentially live on and other then researching rocks on other planets in our solar system, which a robot can do, there is no real need to have a ship dedicated to flying around space. So a "ship dock" and exploration ship in space would be expensive and unnecessary.

Main point is, I doubt we would have trouble getting a ship or the materials to put together a ship into space and once there, there wouldn't be a need to land the main ship smaller shuttles could be used to ferry astronauts to the surface of planets.

I can't resist - They do it in star trek all the time

Re:Exactly wrong!

[mpe]

And I haven't even asked how you are going insert back into earth orbit. Atmospheric re-entry from the Moon was very tricky. And we were only falling from 1/4 million miles.

The only part of Apollo which came back to Earth was the command module. You only need to get the ship back into Earth orbit. Then you either have parts of the crew accomodation serve as suitable capsules or you send up some Soyuz-TMA craft to dock.

Re:Exactly wrong!

[Nefarious Wheel]

How are you going to lift the ship? Space elevator?

Philosophically the same way a VASIMR rocket works -- not all at once, but little bits of it over a long period of time. You assemble it in orbit.

Re:CANADA ROCKS!!!! Woooh

[thrillseeker]

Oh good point ... so is it 39 days or, ahem, 39 Canadian days ...

Re:CANADA ROCKS!!!! Woooh

[Anonymous Coward]

How many Canadians have walked on the moon, again?

Old news

[davidwr]

If I'd left when I first heard this, I'd be about 1/3 way there, time-wise.

Re:CANADA ROCKS!!!! Woooh

[DoofusOfDeath]

Yeaaaaaaaaaaaaaaaaaahhhhhhh!

C'mon you Americans, it's not like you don't defend your national pride in space either! :-)

Bad premise. Since the Bush administration, most of us don't have any national pride.

Re:Tag as SLASHVERTISEMENT

[Anonymous Coward]

Since when do more powerful engines imply safer?

Bathroom stops

[NoYob]

Trip times may vary as folks stop for bathrooms, coffee, and whatnot along the way. So that's where they're getting the 50 day difference.

Re:Bathroom stops

[iamacat]

Trip times may vary as folks stop for bathrooms

Why would you want to waste a valuable propellent?

Re:Bathroom stops

[Nefarious Wheel]

Trip times may vary as folks stop for bathrooms

Why would you want to waste a valuable propellent?

Found a use for Darl then. Reaction mass.

Re:Can this be the primary engine of a space shutt

[geckipede]

The vasimr can operate in a high thrust mode. It's got an operating method that acts a bit like an afterburner, if you're willing to lower your efficiency.

It can't manage a positive thrust to weight ratio in any mode, and in any case can only operate in a vacuum, so it would end up being launched from ground on top of a chemical rocket. In theory once in space you shouldn't need other types of engine.

Re:Tag as SLASHVERTISEMENT

[Anonymous Coward]

For 10 years now, I'm commuting to work with my old Ford Pinto.
Until I read the ad in the news paper and decided it was time for a change.
Now I'm owning on of the modern cars with a VASIMR Ion Engine and have cut my commuting time down by 105 percent. And with the money saved I'm buying a new house, yacht, motorbike and wife.
And when my boss saw my new VASIMR ion engine has gave me a raise and promoted me !

Thanks VASIMR ion engine cooperation, your incredible product saved the day and changed my life for the better !

Re:Can this be the primary engine of a space shutt

[Guysmiley777]

These types of ion engines are only useful once you're in orbit, they're of no use in a deep gravity well or in an atmosphere. They are useful for things such as station keeping thrusters in satellites where you don't want to have to carry a lot of fuel with you.

Sure, they'd be nice for a Mars mission as well, the problem is that they require external power. Not a big deal when you're talking about a couple hundred watts of electric power for less than a Newton of thrust. When you're talking about hundreds of kilowatts it gets a lot more impractical.

Re:CANADA ROCKS!!!! Woooh

[machine321]

Yeah, I lost my patriotism in 1989 too.

Re:CANADA ROCKS!!!! Woooh

[Anonymous Coward]

Bad premise. Since the Bush administration, most of us don't have any national pride.

True, but then Canada isn't a real country either! (ducks!)

Not in space

[NoYob]

Other than perhaps getting the eco-hippies to shut up about lofting lots of highly enriched nuclear fuel.

From what I gathered from Googling, the only thing the "eco-hippies" have a problem with is when those nuclear reactors fall back to Earth - or when they're sunk during a nuclear submarine or ship accident.

I don't think anyone will have any problem launching a nuclear reactor into space other than the astronauts who are on board with it. And considering the long track record of such things, I don't think they will have a problem either.

Re:Not in space

[Anonymous Coward]

The issue is what happens if the launch fails? The juicy payload potentially gets spread all over the place.

Re:Not in space

[TheRaven64]

The problem is getting the reactor into orbit in the first place. If you have a Challenger-style problem with the launch, then you can end up distributing fissile materials over a rather large area. Once the reactor is in orbit, no one cares.

Re:Not in space

[Tim C]

I don't think anyone will have any problem launching a nuclear reactor into space

Well, I've read people arguing that it's too dangerous because of the risk of rocket failure on or shortly after lift-off.

Not saying that's the majority view by any means, but it is a view.

Re:Not in space

[QuantumPion]

Reactors made for space are loaded with fresh (not radioactive) fuel and designed in such a way that they can't become critical until specifically signaled to do so. If the launch fails, all that will fall to Earth will be a few kilograms of Uranium dust over tens of thousands square miles.

Re:Not in space

[QuantumPion]

The problem is getting the reactor into orbit in the first place. If you have a Challenger-style problem with the launch, then you can end up distributing fissile materials over a rather large area. Once the reactor is in orbit, no one cares.

Reactors made for space are loaded with fresh (not radioactive) fuel and designed in such a way that they can't become critical until specifically signaled to do so. If the launch fails, all that will fall to Earth will be a few kilograms of Uranium dust over tens of thousands square miles.

Re:Not in space

[CrimsonAvenger]

From what I gathered from Googling, the only thing the "eco-hippies" have a problem with is when those nuclear reactors fall back to Earth - or when they're sunk during a nuclear submarine or ship accident.

Nah, when the subject of launching one into space came up decades ago, they opposed it completely, on the grounds that it might fall back to Earth.

I should also note that the reactor vessel of a ship's nuclear reactor isn't going to corrode to the point of allowing the contents out in less than many centuries.

I don't think anyone will have any problem launching a nuclear reactor into space other than the astronauts who are on board with it. And considering the long track record of such things, I don't think they will have a problem either.

Considering the way the word "nuclear" causes panic in the minds of many Greens, I'd guess you'd have a lot more problems than that if you tried to launch one.

Re:Not in space

[Anonymous Coward]

Reactors made for space are loaded with fresh (not radioactive) fuel and designed in such a way that they can't become critical until specifically signaled to do so. If the launch fails, all that will fall to Earth will be a few kilograms of Uranium dust over tens of thousands square miles..

Re:Not in space

[Matrix14]

Given that we have a TWO PERCENT failure rate on shuttle launches at this point, those fears aren't entirely ungrounded, at least when it comes to the American space program.

Re:Not in space

[John Hasler]

> The problem is getting the reactor into orbit in the first place. If you have
> a Challenger-style problem with the launch, then you can end up distributing > fissile materials over a rather large area.

There are no dangerously radioactive materials in a reactor until it has run for a while. The reactor would not be started until it was safely in orbit. In any case, the reactor cores can be and are designed to survive rentry unbreached.

Re:Not in space

[Anonymous Coward]

Actually, speaking as a Green (but one of the intelligent ones) - Nuclear is the hip word in the intelligent green community. Nuclear provides all the power necessary while greatly decreasing the polution produced from other sources in the grand scheme.

Maybe it's just Canadian / European Green thing, but Nuclear is what we're all hoping will save us from Coal, Fossil Fuels, and all the other retarded energy solutions we currently have. I live in British Columbia, and we have an enormous amount of hydro-electric power in operation, as well as geo-thermal energy - but until wave energy and high-efficiency solar panels are a cheap reality - Nuclear is the answer to our Gaia-worshipping prayers.

Also, speaking as a geek - 39 days to Mars? Fuck earth let's terraform that shit and move on to the awesomest phase of humanity: galactic conquest!

Re:Not in space

[Anonymous Coward]

We've had one failed shuttle launch in 120+ launches. How the hell does that give a failure rate of 2%?

Re:Not in space

[Anonymous Coward]

In the way that a car "might" crash?

(Captcha: "momentum")

Re:Not in space

[abarrieris5eV]

As much as this has gone badly in the past, with sunken submarines, lost hydrogen bombs, and at least one crashed space craft I know of, I think this could be done reasonably safely. The fuel may not have to be weapons grade, and it should be possible to launch it in such a way that if something goes wrong it at the very least crashes into a place where it will do little damage (especially compared with the above mentioned accidents). The likelyhood of an accident releasing nuclear fuel can be reduced with appropriate containers. While in space radiation exposure is already very dangerously high. A nuclear reactor driven ship could actually be a benefit, since it alleviates some design limitations on weight and could therefore allow for better shielding for the passengers.

Re:Not in space

[mcvos]

I'm suddenly reminded of the Casini. There was a bit of worry surrounding it because it carried several kilograms (32 I think?) of Plutonium, which is quite a lot more dangerous than Uranium if it burns up in the atmosphere.

Re:CANADA ROCKS!!!! Woooh

[Anonymous Coward]

About as many as don't have heath care coverage.

4 out of 5 astronauts surveyed

[bl8n8r]

preferred 39 days of abstinence to 6 months!

Re:4 out of 5 astronauts surveyed

[RivenAleem]

It's only 4 out of 5 because the 5th astronaut had nobody to hook up with (Zero-G threesomes don't work out as the collisions are elastic)

Re:4 out of 5 astronauts surveyed

[cathector]

.. implying there's a whole passel of people to it with once you reach Mars ??

Re:4 out of 5 astronauts surveyed

[Tetsujin]

It's only 4 out of 5 because the 5th astronaut had nobody to hook up with (Zero-G threesomes don't work out as the collisions are elastic)

Obligatory XKCD...

Re:4 out of 5 astronauts surveyed

[MadCow42]

>> preferred 39 days of abstinence to 6 months!

So, bring girl astronauts too... problem solved. As long as they look like the Bond girls in Moonraker, who cares how long the trip takes? :)

Re:4 out of 5 astronauts surveyed

[hansraj]

Damn it! modded you flamebait trying to lose the focus of the moderation field. Commenting to undo the mod.

Re:4 out of 5 astronauts surveyed

[Anonymous Coward]

39 days is one way... your post implies a gigantic interplanetary orgy once they arrive on mars
maybe they should aim for phobos

Re:4 out of 5 astronauts surveyed

[elrous0]

Except for one guy, who is apparently quite content with being locking in a small capsule in close quarters with several other men.

Re:4 out of 5 astronauts surveyed

[Anonymous Coward]

It would take about 39 days to reach Mars

Oh wait, they planned to have sex on Mars?

Re:4 out of 5 astronauts surveyed

[Anonymous Coward]

Because you're going to have sex with the martians, right?

Re:4 out of 5 astronauts surveyed

[Anonymous Coward]

And getting away from annoying coworkers: Mission to Mars: Day 312

Re:Tag as SLASHVERTISEMENT

[slack_justyb]

I have to agree with the grandparent. VASMIR is old news as far as cutting edge technology. Really, why not put out an article about how awesome Blu-Ray is (rolls eyes)? So let's look pass the whole VASMIR thing and start looking at the applications themselves, "to be used on ISS in 2013" strikes me as the most useful piece of information in the summary. VASMIR technology is getting better and better every day, but so is diesel and bio-diesel technology.

At some point, continuing to beat the gong on something starts to make it look like those "Wow" commercials from the Windows Vista days, or all those promises of action during the campaigning days here in the United States.

Re:CANADA ROCKS!!!! Woooh

[Bob-taro]

Oh good point ... so is it 39 days or, ahem, 39 Canadian days ...

That's 39 Metric days. To convert to American days, you double it and add 30.

LCD vs Plasma

[Anonymous Coward]

Take that, LCD pundits ! Could you fly to Mars on a Variable Specific Impulse MagnetoLCD Rocket ? No ! That requires the power of plasma ! Don't talk about contrast, color accuracy, response time or resolution : if you can stick it to a rocket is the only relevant criteria. And if it goes kaboom, it's ever better.

Get u ass to Mars

[Latinhypercube]

Get u ass to Mars. Get u ass to Mars. Get u ass to Mars.
(In Schwarzeneggarian )

Well that's just great...

[FrozenGeek]

A motor that runs on hydrogen - a non-renewable resource. How long will it be before we run out of hydrogen????

Re:Well that's just great...

[mcgrew]

A motor that runs on hydrogen - a non-renewable resource.

Going for "funny" can be hazardous to your karma.

Re:Tag as SLASHVERTISEMENT

[scorp1us]

I would change my name to Philip Fry if I was selected for the mission.

Re:CANADA ROCKS!!!! Woooh

[operagost]

So, were you guys most proud during the "sorry hostages, we crashed the rescue helicopter" administration or the "I did not have sex with that woman" administration?

Re:Tag as SLASHVERTISEMENT

[lordfoul]

Pass..I hear it won't run Hulu in full Screen..

Re:CANADA ROCKS!!!! Woooh

[Anonymous Coward]

Embarassed beyond words, truthfully...so much so, I'm posting anonymously...

Re:CANADA ROCKS!!!! Woooh

[Anonymous Coward]

Bad premise. Since the Obama administration, most of us don't have any national pride.

ALIENZ

[Anonymous Coward]

Sweet!
39 days to bring back a carnivorous alien life form to earth, instead of 6 months!

Re:Tag as SLASHVERTISEMENT

[operagost]

Why buy a new car, when you can just make your "pinto" bigger with C1AL15!

Newsflash

[Dunbal]

Engine that hasn't really been invented yet might rhubarb rhubarb rhubarb rhubarb....

      Of course as a nationalized Costa Rican citizen, perhaps I should celebrate the fact that Franklin Chang Diaz is the creator of this engine, however let's wait and see until it has actually been tested before we make specific claims, yes?

Re:Newsflash

[WuphonsReach]

Engine that hasn't really been invented yet might rhubarb rhubarb rhubarb rhubarb....

Ah, a fellow Goon Show fan?

The Lyle Drive

[Tetsujin]

Sweet!
39 days to bring back a carnivorous alien life form to earth, instead of 6 months!

But, on the other hand, we'll be able to bring back the one human survivor of the last Mars mission much more quickly! All will be well as long as he doesn't wish us into the cornfield.

Re:Can this be the primary engine of a space shutt

[TheDarkMaster]

VASIMR + Nuclear power plant = Beware Mars! We are incoming!

Artificial gravity?

[Anonymous Coward]

So presumably this thing is thrusting all the time it is travelling: Accelerating constantly for the first half of the journey, and then flipover half way to decelerate for the second half, to arrive at the destination without any excess velocity.

How much acceleration does it provide? Is it enough that the crew would experience some kind of weak "artificial gravity" effect?

Re:Tag as SLASHVERTISEMENT

[bds1986]

If something goes wrong on the surface, help is 39 days away, instead of 6 months.

no big loss

[juan2074]

If we launch from Cape Canaveral, we only risk contaminating Central Florida.

Re:Can this be the primary engine of a space shutt

[joh]

Where to get the power from is a main problem in spaceflight, regardless of engine. Anything you have to carry with you is a problem since you have to accelerate it along. Chemical engines get their power by burning fuel and fuel is heavy. The only way to overcome that problem is to use power you *don't* have to carry. That means getting power beamed to you from elsewhere and this can be either from the sun (solar power) or via microwave or laser. Electric engines have an advantage here because you can beam electricity but not fuels.

By the way: There already were a probe going from low earth orbit to the Moon with nothing else than solar power and an ion engine. Look up Smart-1.

Re:Tag as SLASHVERTISEMENT

[pixelpusher220]

I believe the 'safer' idea is that instead of a 2 year round trip, we might be talking a few months. Lots easier to get help when it's only 45 days away rather than 6-12 months.

And yes, 'easy' in this case is still ridiculously hard...but still it's a good bit better than 2 years.

Light speed probes

[GodfatherofSoul]

I'd like to see a test probe fly just as fast as we can get it to go. I'm sure it'll be pulverized by dust motes if you can get it moving fast enough, but it would be cool to see something we've created jetting about a some considerable fraction of light speed. Maybe you can get to another star system in a human lifetime?

Re:Light speed probes

[John Hasler]

This is many orders of magnitude away from near-light-speed capability.

Re:Light speed probes

[GodfatherofSoul]

Is there a theoretical limit?

Re:Light speed probes

[nitehawk214]

Yes, as you get get going faster, your effective mass goes up. This means to get to relativistic speeds you must apply thrust exponentially. Another problem is an engine of this type will eventually spit out all of its plasma and will run out of "fuel", so to speak.

Still, since you can run a plasma or ion engine from an external power source (the sun), you do get a massive jump in specific impulse.

Re:Light speed probes

[mcvos]

Still, since you can run a plasma or ion engine from an external power source (the sun), you do get a massive jump in specific impulse.

At any meaningful fraction of lightspeed, the distance to the sun will quickly get too big to be able to rely on it for energy.

Edge of the Solar System?

[XFire35]

So does that mean that we could venture to the edge of the solar system in under two years? (Two years comes form a guestimate from wikipedia image)

Re:CANADA ROCKS!!!! Woooh

[Anonymous Coward]

Well, to be fair, the planet does spin faster the closer you get to the poles.

Re:Tag as SLASHVERTISEMENT

[avandesande]

The logical thing to do would be to get the return vehicle in orbit around mars, ready to go before an astronaut leaves earth. This would be make reduce the number of errors that would put an astronaut into a life threatening situation (return failure).

A relatively small rocket could be used to get the astronaut off of Mars' surface. It won't take much with its lower gravity and thin atmosphere. We could even test all these scenarios remotely.

Re:Tag as SLASHVERTISEMENT

[oldspewey]

If something goes wrong on the surface, help is potentially as little as 39 days away, depending on the relative orbital positions of Earth and Mars, instead of 6 months.

Fixed.

You were up-modded by people who don't read

[Anonymous Coward]

Why is it that people who don't read spend so much time here? In point of fact, it is far more "efficient" measured in "rocket terms" like "specific impulse". Spend more time reading, and less time posting, please.

Re:You were up-modded by people who don't read

[andrikos]

Spend more time reading, and less time posting, please.

You must be new here, right?

Not to worry

[WindBourne]

Between Rush and the future Mildred E. Gillars, William Joyce's, that AC will fit right in.

How did you get modded up?

[WindBourne]

First, it is easy to send up lots of uranium into space. It can be sent in capsules that can take any issue (heat, water, etc). BUT, the simple fact is, that the moon has been found to contain Uranium. And it appears to be a LOT. It should be possible to mine it and send it various places. While I was actually a fan of Mars first, now I back the moon due to the water and uranium. Combine that with an electric launcher and it should be possible to send missions at extremely fast rates through the solar system.

Re:Tag as SLASHVERTISEMENT

[Anonymous Coward]

could make a manned mission to MARS much more feasible and safer.

It also places manned missions to other planets within reach. Trips to Titan anyone?

Don't let this one fade into obscurity

[prisoner-of-enigma]

I for one am tired of hearing about all these wonderful propulsion ideas that inevitably fade into the background. What is it going to take to get one of these damned things built and tested?

Yes, I know the trite answer is "money," but that's merely a means. What we lack is desire. I have a funny feeling that all the billions we've wasted on the ISS and keeping the nigh-useless Shuttle flying these past decades could've easily funded an unmanned test vehicle that could've used VASIMIR to fly to Mars and back as a technology demonstrator.

Let's quit talking about what this technology "could" do and actual do it for a change. If it's feasible then we should be screaming at our Congress-critters to get behind it.

Re:Don't let this one fade into obscurity

[DigiShaman]

I'm afraid our Government is strapped for cash, and will be in debt for a very long time. I propose setting up a donation system that will we can help fund NASA.

Oh, BTW. The donations *must* go directly to NASA and not some Government slush fund!

Re:Don't let this one fade into obscurity

[mcvos]

I for one am tired of hearing about all these wonderful propulsion ideas that inevitably fade into the background. What is it going to take to get one of these damned things built and tested?

Aren't other ion engines already being used?

Oy...

[xx01dk]

VASIMR.





...what.

Re:CANADA ROCKS!!!! Woooh

[Anonymous Coward]

No it spins slower... fucking Creationists.

Re:CANADA ROCKS!!!! Woooh

[KWolfe81]

Last I checked the markets... a Canadian day was just about on par with a US day. What a weird world indeed!

Comment removed

[account_deleted]

Comment removed based on user account deletion

Re:CANADA ROCKS!!!! Woooh

[Anonymous Coward]

Wrong... the planet spins faster at the equator

Both at the equator and at the poles, it takes the same amount of time to make one rotation. However, the equator has a significantly larger circumference of rotation than the poles, so therefore the equator must be travelling much faster.

Re:CANADA ROCKS!!!! Woooh

[jafac]

I dunno.

If Freud were alive today, he'd have a field-day comparing launch vehicles (size, reliability, national ego, etc.) to penises. I reckon especially with the new flesh-colored Ares upper-stage.

I know I do.

Re:Tag as SLASHVERTISEMENT

[Creepy]

Actually, I've found the latest VASIMR progress quite interesting, but that article seemed more intent on promoting Canada than feeding news. Heck, the ISS mission has been known since 2007.

A google search was also able to come up with an article with a lot more meat. This explains that the project is working towards 200MW ion rockets (MUCH more powerful than the earlier .3kW), would be powered by a cheap nuke drive instead of solar panels, and they believe it's doable by 2020. Similar info is in PopSci this month.

Now if they could just get that dense plasma fusion device (see Slashdot yesterday) to power the craft instead of fission, that would be cool... yeah, I know I'm pipe dreaming again, but I can't help it.

great research, no let come down to earth

[recharged95]

Ion engines are worth nothing if you can't get from Earth (the GROUND) to space efficiently and effectively.

And a bunch of Aries rockets isn't going to cut it.

We have a dream (Just to goto space), why do we need to have more dreams (Mars)? Why can't we keep the problem simple?

Re:great research, no let come down to earth

[Anonymous Coward]

mars is in space.

Re:great research, no let come down to earth

[Galestar]

If we just "keep it simple", we'd just stay home.

Stupid in public

[sjbe]

One minor knit to pick. The momentum doesn't double with a doubling of the speed of the reaction mass. It quadruples. Remember your high school physics: KE=0.5*m*v**2

Momentum = mass * velocity (linear momentum of a particle)
Kinetic Energy = 0.5 * mass * velocity^2 (for a newtonian rigid body)

Apparently you flunked high school physics...

Re:Stupid in public

[dkf]

Momentum = mass * velocity (linear momentum of a particle)
Kinetic Energy = 0.5 * mass * velocity^2 (for a newtonian rigid body)

For the correct definitions of mass and velocity, those work for bodies with relativistically-significant speeds. (In short, you can have arbitrarily high kinetic energy and momentum without infinite velocity, because of how the interpretation of mass and time changes. This stuff is very odd when you think about it...)

these are like "smashing Moore;s Law" articles

[peter303]

Only a tiny percent of them are commercially viable.
But enough to keep the trend going.

Slight Problem

[maroberts]

Gravity wells. As has been mentioned before, ION engines are great for long distance travel. The only problem is getting down and up from Mars or any other planet you decide to visit, where you're back to needing a big rocket for the high thrust needed. So you can get your astronauts in orbit round Mars, but the problem is how to get them down and up from the surface?

Off Topic to Star Trek - What's next?

[abbynormal brain]

From the article: "Ion propulsion, discussed since the original Star Trek TV series"

Seeing a pattern here:
- First inter-racial kiss on TV > now a normal occurrence
- "Beam me up Scotty" on a *communicator* > now a cell phone
- TV Ion propulsion > now, Real Ion propulsion!

What's next?!

- Plastic surgery > yes, you too can have Spock ears. I dare you.

Re:Off Topic to Star Trek - What's next?

[NotBornYesterday]

- "Beam me up Scotty" on a *communicator* > now a cell phone

Yeah, we have cell phones, but they still can't beam me up.

Re:Tag as SLASHVERTISEMENT

[BB_Cat_3k]

A better idea for error free is to place the return vehicle on the surface before launch, and have the crew land at that point as described in Rob Zubrins A Case for Mars. One less docking maneuver is that much safer, and the useful payload can be larger.

Canadian Space Agency

[stoob0]

Do all Canadian astronauts launch with mittens close at hand? Does the other pocket visible in the picture contain pucks?

lol.

[Anonymous Coward]

You've instantly garnered my respect,

but dude, this is Slashdot, not rocket science!

-Matt

Re:CANADA ROCKS!!!! Woooh

[Gerafix]

Even the Republicans know that Canada is a real Communist Socialist Marxist Death Panel Lottery Country(TM).

Hope for the future!

[Anonymous Coward]

I'm glad to see we're planning beyond 2012. I thought for sure we'd be skunked for sure with doomsday quickly approaching.

Re:Tag as SLASHVERTISEMENT

[SECProto]

yeah... except it would be 6 months /at the best of times/ with conventional rockets. change none or change em both, as they are both dependent on orbital positions

return is faster possibly?

[hydromike2]

im not claiming to have RTA but depending on how fast they are going couldnt they just orbit mars while sending a smaller craft down to the planet and already be at the speed they were at when they came to mars and not need to accelerate as much? Or for that matter, get the craft started going in orbit remotely around the earth, then send the crew up and be on their way?

Mod the parent up!

[slack_justyb]

That's very informative. I wish I could mod you up. That's much better than TFA.

Re:CANADA ROCKS!!!! Woooh

[Arthur Grumbine]

True, but then Canada isn't a real country either! (ducks!)

Perhaps (Geese!) would have been more appropriate?

Re:Tag as SLASHVERTISEMENT

[AGMW]

If something goes wrong on the surface, help is 39 days away, instead of 6 months.

Not sure that is always going to be the case, unless the VASIMR also has a side effect of locking Earth and Mars so they don't move relative to each other because I'm guessing the quoted 39 days is the minimum time for when Earth and Mars are at their closest.

Yea, but.....

[Anonymous Coward]

"A whole bunch of countries (were involved), but Canada has one of the main pieces of hardware. And this engine can get us to Mars in 39 days."

What they don't mention is that if you want to stop off at Mars you have to slow down before getting there - so it still takes 6 months to get there. Doh!

(trollin' for people that didn't read the article)

Poor style...

[onemorechip]

Please do not start an article (or summary of an article) with "It", even if the referent appears in the title.

Re:Poor style...

[Anonymous Coward]

Seriously, "offtopic"? Surely you could have found a better use for your mod points. What is this world coming to if recommendations on style are discouraged?

Re:CANADA ROCKS!!!! Woooh

[Blakey Rat]

Canada has one of the main pieces of hardware? You mean this engine runs on moosehide!?

Re:Tag as SLASHVERTISEMENT

[GradiusCVK]

Interesting point; 39 days is around the limit of how long an average healthy human can go without food before they begin to starve - it's tough to be exact because it is heavily dependent on the person (i.e. fat stores), but it's almost definitely surviveable if they send healthy people who've been prepped with a little bit of chub. On the other hand, six months is quite a different matter... almost definitely not survivable.

Of course, running short of water or oxygen, or any number of other disasters (exploding and what have you), are still a danger - but any improvement in the odds of survivability is welcome.

Re:Tag as SLASHVERTISEMENT

[Bent Spoke]

article seemed more intent on promoting Canada than feeding news.

Gee, an article from canada.com that's Canada centric. Who'd of thought!

Re:Tag as SLASHVERTISEMENT

[DJRumpy]

What happened to the 'old hat' where ION rockets were considered great long range solutions, but terrible for short term acceleration? Has the technology changed that much that they are just much more efficient on actual thrust?

Re:Tag as SLASHVERTISEMENT

[pixelpusher220]

according to Wikipedia:

"every part of a VASIMR engine is magnetically shielded and does not come into direct contact with ionized plasma, the potential durability of this engine design is greater than other ion engine designs"

Re:CANADA ROCKS!!!! Woooh

[Anonymous Coward]

Yeaaaaaaaaaaaaaaaaaahhhhhhh!

C'mon you Americans, it's not like you don't defend your national pride in space either! :-)

Well, come on man, it's not really so much "National Pride" as it is more like State Pride.

Ok, so we haven't gotten around to adding the 51st star to the flag yet. But given the current economic climate you gotta admit that there are more important things that we could be spending tight budgets on instead of updating all the flags all over our collective country, right?

BTW, you new guys should remember to mark your calendars for July 4th... Remember, you're not supposed to go to work that day, eh?

This was an Israeli invention.

[RiddleyWalker]

Israel has been working on the Oy Vasimir engine for some time. Gevult.

Re:Tag as SLASHVERTISEMENT

[Pictish Prince]

I heard Terrence & Phillip were going to be on the first mission.

Reaction mass vs. Reactor Mass

[James McP]

The features of nuclear steam and VASIMR are pretty much a list of opposite pros and cons. E.g.:

nuclear steam doesn't waste any mass with electrical generating components so it is lighter overall than VASIMR.

Contrast this with VASIMR which can run on solar arrays and can share its electrical power source with other components.

Nuclear steam has a lower exhaust velocity so the overall power source requirement is lower.

Vasimir's higher velocity mean the specific impulse of reaction mass is 5x greater than nuclear steam, reducing carried mass and power generating needs. This has significant impact when duration of thrust is very large.

These attributes define the design envelopes.

If you need occassional thrust without a lot of mass and already have an electrical power source, VASIMR is good (e.g. orbital correction for satellites and space stations).

If you want to move a payload under continous thrust for days on end, a nuclear rocket is a good choice.

If you have a payload that has a fairly beefy electrical power source that you want to move under continous thrust for weeks on end, VASIMR is worth considering but may or may not be the best choice.

If you want to move a payload under continous thrust for a many months, go with VASIMR.

E.g. a russian ERTA generator can produce 150kW for 1.5 years while weighing 7500kg. A 150kW VASIMR drive would weigh 225kg and produce 4N. Fuel for 1.5 years is 9300kg. Total starting mass for 1.5years of 4N thrust is 17,025kg.

The SNTP nuclear rocket weighs ~13kg/N so 50kg of motor. Generously assuming the nuclear fuel would last 1.5 years, it still needs 49,000kg of reaction mass. Total starting mass for 1.5 years of 4N thrust is 49,050kg.

Assuming I've done the math right (which is not guaranteed since it involves partial fraction calculus) under that whopping 4N of thrust the VASIMR rocket will crank up to yawn-inspiring 0.004 m/s while the nuclear rocket will do a pokey 0.0012 m/s. Distance wise, the Vasimir will traverse 10.8 km vs. the nuclear rocket has only covered 3.8km.

While utterly theoretical, it does show that for ultra long burns, the reactor overhead of VASIMR is outweighed by the reaction mass increase of a nuclear rocket.

Re:Reaction mass vs. Reactor Mass

[holmstar]

You're math is way off. My (rather rough) math based on your numbers says that the vasmir probe would be traveling about 16km/s after 1.5 years.

if you somehow managed to contain 49000kg of water within your 50kg of nuclear probe mass (must be some mighty thin tank walls), it would be going about 26km/s after 1.5 years. Most of that velocity is gained at the end when the probe mass is just a little over 50kg. If you add, say 2000kg for the water tank, the velocity is closer to 12.4km/s after 1.5 years.

Re:Reaction mass vs. Reactor Mass

[James McP]

Your points about storage and fuel are valid. I ignored storage compartments for water/argon as well as the mass of a nuclear motor equipped with 1.5 years worth of fuel. If the final "dry" mass of the VASIMR and nuclear rocket are closer, the Vasimr becomes more appealing.

The math on this sucks. Rounding is a total PITA. You need like 8 significant digits for the final periods (which are critical) to work out. It's been almost twenty years since my last calculus class so yeah, my math could be fubar.

Here's my physics algebra:
Force = mass x acceleration
Force = 4N = mass x acceleration
acceleration = 4N/mass

Mass is reduced over time based on the Isp of each thruster. Time (t) is in seconds.

So acceleration = 4N / (start mass - (Isp^-1)t)

because acceleration is itself a function of time you can't use the pre-solved newtonian v=at or d=0.5at^2 to calculate velocity and acceleration.

So v= integral(acceleration)dv/dt

and distance = integral(velocity)dv/dt

Final velocity and distance is solved by integrating across t from t=0 to t=47,304,000s (1.5 year in seconds)

With the variable in the denominator you need partial fraction calculus which results in natural log terms which then get integrated again. The double integral of c/(a-bx) is a right nuisance and I could easily have screwed up the order of operations on the second integral.

Ready to Colonize!

[Anonymous Coward]

39 days!
Colonization is very doable with only a month...the Europeans took longer to get to N. America by sail (or Polynesians going east to Hawaii).
Fast enough that it may be possible to go out even on non-ideal planetary alignments.
One could send out plants and basing stuff right off the bat and follow with ship 2 with supplies and more permanent base-making stuff.
One could also set up a base in Mars orbit to refuel multiple ships to mine asteroids :0)

Re:Can this be the primary engine of a space shutt

[johno.ie]

Ok, I'm not trying to be pedantic here. Is there any chance that a VASIMR-based engine could be used for a lunar takeoff? How much would you need to improve the efficiency in terms of power to weight to achieve that?

Re:Tag as SLASHVERTISEMENT

[KeensMustard]

Not wanting to start a holy war here, but what is the deal with you VASIMIR powered car fanatics? I've been sitting in my freelance camry with an attached VASIMIR (a 8600/300 w/64 Kg Propulsion Mass) for about 20 minutes now while it attempts to transfer a 17*10^1 kg Slashdot reader from his home to the electronics store. 20 minutes. At home, on my RD-180 powered Datsun running Kerosene, which by all standards should be a lot slower than this VASIMIR, the same operation would take about 2 minutes. If that.

It's not about *energy* efficiency.

[zippthorne]

With rockets, you have to consider mass-efficiency AND energy efficiency. They are not equal, and they are often opposed: high output velocity is mass efficient, getting the most change in velocity per particle lost, but provides little thrust for the energy input.

For example, in the limiting case of a flashlight rocket, zero mass is lost, but the kinetic energy return on radiation energy output is ~delta-v/(2c). IOW, a flashlight rocket would be great for relativistic velocities, but not so great for orbital maneuvering in the 8 km/s range.

Low velocity particles give much better thrust performance, at a cost of depleting the mass reserves much more quickly. This is why you see jet engines powering a fan to move more air-mass through. It slows down the exhaust velocity (and cools the exhaust temperature), but provides a much wider stream and more thrust. Air-breathing engines have unlimited reaction mass available to them: the atmosphere that impedes flow also provides a ready source of mass for the engines.

In space, reaction mass is limited, but energy need not be. Near a star, there is a constant radiation flux, which if you're patient can be collected indefinitely (compared to the length of the typical space-mission, anyway).

Electric drives are very relevant in space for this very reason.

However VASIMR is not an electric engine. It's a hot-plasma engine. Instead of using electric fields to accelerate particles, it uses magnetic field-lines to guide them. It is basically agnostic about the heat source, although conventional combustion is not hot enough and too high density, so the first models will probably use microwaves. But it doesn't have to be microwaves. One of the pie-in-the-sky goals is use the magnetic field to induce fusion (much like in z-pinch devices), and use that output for thrust.

SNAPs

[lennier]

While it's true that the Pioneers and Voyagers used RTGs, it's interesting that the SNAP program developed both RTGs (odd-numbered) and fission reactors (even numbered). SNAP 10A apparently was the only true reactor to get launched. Only 500 watts though, so not so much bigger than an RTG, but...

http://en.wikipedia.org/wiki/Systems_Nuclear_Auxiliary_Power_Program
http://en.wikipedia.org/wiki/SNAP-10A

Re:SNAPs

[Mr. Roadkill]

SNAP-10A is also still up there in a stable orbit, although it's no longer functional or complete - a failure in an electrical system, plus the beryllium neutron reflector was ejected.

Somebody (NASA? Or, if you're not keen, how about giving the Chinese or the Indians all the design specs) should be looking at this thing. It's already up there, and won't require a launch of radioactive materials. Worst case, it may be possible to simply re-use the fuel rods in another reactor - one with another 44 years of advances and design experience behind it. It's also been up there for 44 years - admittedly in mothballs rather than functional - and may provide some insights into the effects of long-term exposure to space for those kinds of systems.

What are the salvage laws, as applicable to space? Would China or India even need permission to simply take the fissionable material for re-use in another reactor? NASA "Parked" it, but could it be considered "abandoned"?

You mean like this NASA fission plant?

[Machupo]

http://www.technologyreview.com/energy/23247/

Re:Tag as SLASHVERTISEMENT

[DJRumpy]

I meant more in a mechanical sense that the old idea for an Ion engine had them taking forever to build up acceleration, but give the fact that they could accelerate plasma out at extremely fast speeds, they were great for long range implementations. How did they resolve the poor thrust issues?

Re:Tag as SLASHVERTISEMENT

[gyrogeerloose]

it's tough to be exact because it is heavily dependent on the person (i.e. fat stores)

Right. Most of us Slashdotters could easily go 39 days. On the other hand, if Kate Moss misses lunch she has to be hospitalized.

Re:CANADA ROCKS!!!! Woooh

[tsotha]

You guys should be very proud of your arm on the ISS. Seems to be the most useful bit on the whole thing.

Re: The catch...

[Anonymous Coward]

The major catch is that when you throw stuff out the back twice as fast, it takes four times as much energy.

Ten times as fast -- 100 times as much energy.

So what you gain in propellant efficiency, you lose in energy efficiency.

This will be much bigger than it appears

[Impy the Impiuos Imp]

If this pans out, it will be much bigger than it appears. A huge multi-government Mars trip will be little more than a test run for industry. Now getting about the solar system is on the order of sailing ships traveling the ocean under wind power, rather than a ridiculous, multi-year trip just for one way.

Basically, you just need to build ships to be sturdy enough to last out a few months if they break down, so a "rescue ship" can come get them.

If you can get to Mars in 39 days, the asteroids, Jupiter, Saturn and beyond are not much further. It's now feasible to populate the solar system.

Eat your Wheaties so you can live long enough to take a poop on Europa just to spite the monoliths.

Re:Can this be the primary engine of a space shutt

[putaro]

Just a quick look, without factoring in any real design details like weight of the ascent stage, propellants, etc.

Apollo LM ascent engine = 15.6kN thrust. VX-200 is expected to have a thrust of 5N. So, about 3000x increase in thrust appears to be needed to get into the ball park of lunar liftoff.