New Ion Engine Enters Space Race

Bibek Paudel brings us a BBC report on the development and testing of an new ion engine by a security firm named Qinetiq. The engine will be used in an ESA spacecraft tasked with mapping the Earth's gravitational field from orbit. Only a handful of ion drives have been used for space missions before, some of which we have discussed. Quoting: "Cryogenic pumps can be heard in the background, whistling away like tiny steam engines. Using helium gas as a coolant, they can bring down the temperature in the vacuum chamber to an incredibly chilly 20 Kelvin (-253C). The pressure, meanwhile, can drop to a millionth of an atmosphere. Ion engines ... make use of the fact that a current flowing across a magnetic field creates an electric field directed sideways to the current. This is used to accelerate a beam of ions (charged atoms) of xenon away from the spacecraft, thereby providing thrust."

Comments

why xenon?

[Justabit]

Wouldn't a heavier material like lead be more efficient at mass transfere and therefor thrust?

Re:why xenon?

[Anonymous Coward]

Wouldn't a heavier material like lead be more efficient at mass transfere and therefor thrust? Mass has nothing to do with it. The only thing that matters is charge. If you put H+ or Xe+ in a constant electric field they will will both have the same kinetic energy once they exit (hence, something that has a 1 e charge put across a 1 V potential will have 1 eV of kinetic energy on exit). Xenon is useful because you can strip a lot of electrons off of an atom to make a highly charged ion. It is also easy to store and ionize.

Re:why xenon?

[calebt3]

"Late" is a matter of perspective.

Anyways, it is 7:25 PM in the Pacific Time Zone right now.

Re:why xenon?

[mk_is_here]

From wikipedia:
Xenon is the preferred fuel for ion propulsion of spacecraft because of its low ionization potential per atomic weight, and its ability to be stored as a liquid at near room temperature (under high pressure) yet be easily converted back into a gas to fuel the engine. The inert nature of xenon makes it environmentally friendly and less corrosive to an ion engine than other fuels such as mercury or caesium. Xenon was first used for satellite ion engines during the 1970s. It was later employed as a propellant for Europe's SMART-1 spacecraft[16] and for the three ion propulsion engines on NASA's Dawn Spacecraft.

Re:why xenon?

[doctor_nation]

No, mass is important. The fact that xenon is so massive is exactly why it's used- that and the fact that it has a very low ionization potential. The only better material is mercury, but they stopped using that several years ago for obvious reasons.

Re:why xenon?

[Anonymous Coward]

No, the only thing that matters is momentum. If you shine a 3 MW laser out the back of the spacecraft for 1 s it is only going change the momentum of the spacecraft by 3 MJ/c = 0.01 kg*m/s. If you toss a 145 g baseball out the back of your spacecraft at 30 m/s (KE of baseball = 130.5 J) you will gain 4.35 kg*m/s of momentum, 435 times what the laser would do.

In the case above p = sqrt(2m * E). While E is a function of charge alone, the momentum is a function of both mass and kinetic energy. But it is a sqrt so you need to take into account your ion charge and its mass. A +16 charge is only twice as good as a +4 charge and 16 u is only twice as good as 4 u. Once you take this into account you will find that the difference between Xenon's 131.3 u mass and lead's 207.2 u mass is not as significant as other factors (like ease of use or ease of ionization).

Re:why xenon?

[Anonymous Coward]

If you toss a 145 g baseball out the back of your spacecraft at 30 m/s (KE of baseball = 130.5 J) Whoops, I failed to divide by 2. s/130.5/65.25/

Re:why xenon?

[zippthorne]

Smaller molecular weight typically preferred for space thrusters, due to the higher exhaust velocities for similar amounts of energy or momentum imparted. p=mv and E=mv^2 and all.

Which in turn means higher specific impulse.

Which in turn means greater delta-v budget for the same mass.

The price for pushing fewer molecules at higher speeds? Lower thrust at the same power level. But if you've got "unlimited" energy (solar) or "nearly unlimited" (RTG), you can take afford to take the time.

In fact, there are transfers calculated that take less time, despite taking longer to get up to speed, due to the greater delta-v.

Since double-ionzation is much more difficult than single ionization, different atoms have different work functions, and there is a limit to the electric field you can practically achieve, charge:mass ratio is a design constraint.

Re:why xenon?

[Anonymous Coward]

Um, I think this is the link you're looking for.

Re:why xenon?

[schon]

Whoops, I failed to divide by 2 That's OK - everybody knows that rocket scientists don't need to be proficient at math. :)

Re:why xenon?

[evanbd]

It's more complicated than that. To good approximation, ion engines add energy, not momentum or velocity, to the particles they accelerate. So heavier ions leave slower, resulting in lower Isp. Thus, Xenon has relatively low Isp. However, it has the huge advantage of being easy to ionize, a gas, and nontoxic (mercury manages the first two but not the third (at ion engine pressures it's a gas), and adds the downside of tending to dissolve the engine too much).

However, for most ion engine applications, Isp isn't the primary concern -- thrust is. Ion engines easily manage more Isp than they need, but the solar cells to power them are heavy. It would be simpler and produce a shorter flight time to lower the Isp, not to mention reducing the delta-v required (orbital transfers using very long burns, as with ion engines, pay a penalty in delta-v for doing some of their burn higher in the gravity well than they have to; this can be as much as 50% iirc).

In short, Xenon is chosen because it's easy to work with and not too expensive; the heavy mass is a plus in many applications, but the reasons are more complicated than most people realize.

Re:why xenon?

[Nullav]

So...you're proposing that we propel spacecraft with baseballs?

Re:why xenon?

[Anonymous Coward]

You also don't appear to be a fan of significant figures.

Re:why xenon?

[Manhigh]

When it comes to ion propellant, the important figure of merit is the ratio of ionization energy to atomic weight. For each unit of energy spent creating an ion, you want a relatively heavy ion to propel for some "oomph." Historically, mercury and argon have also been used, though they are less efficient (and in mercury simply undesirable).

Re:why xenon?

[jollyreaper]

So...you're proposing that we propel spacecraft with baseballs? No, we're propelling our baseballs with spacecraft, depending on your frame of reference.

Re:why xenon?

[RobertM1968]

Hmmm... I think I really need to re-watch my episodes of Star Trek TOS... I know they covered the whole Ion Engine thing in one of them... THEN I can come back and comment intelligently on this topic.

Re:why xenon?

[zippthorne]

Ah, but how many baseballs can you carry on your spacecraft?

What about photons? ..
there are many kinds of efficiency. You must always remember to be most efficient with the thing you have the least of.

Re:why xenon?

[Tom9729]

And you're just feeding trolls. :)

Re:why xenon?

[nomadianomad]

They would be called Spaceballs.

Re:why xenon?

[LittleBigLui]

So...you're proposing that we propel spacecraft with baseballs?

(emphasis mine)

Re:why xenon?

[Anonymous Coward]

I know a few pitchers you can start with.

Re:why xenon?

[vought]

Fuckin' Zito.

Re:why xenon?

[kcbanner]

Hard to store lead as a gas.

Re:why xenon?

[yahooadam]

by a security firm named Qinetiq security firm? since when? http://en.wikipedia.org/wiki/QinetiQ

Re:why xenon?

[dintech]

Now all you need is a replicator and you're good to go.

Re:why xenon?

[PJ1216]

more complicated than most people realize. since when is rocket science complicated?

Re:why xenon?

[Anonymous Coward]

Spaceballs? There goes the neighborhood.......

Re:why xenon?

[Timberwolf0122]

The only problem with any engine that needs a propellant (Spaceballs or Xenon) is that it will run out eventually a Laser will run as long as it has power (along time if you use solar or say nuclear decay).

XKCD has an interesting way to get more out of a laser

Re:why xenon?

[Gilmoure]

The only better material is mercury, but they stopped using that several years ago for obvious reasons.

They don't want to pollute space?

Re:why xenon?

[turgid]

To good approximation, ion engines add energy, not momentum or velocity, to the particles they accelerate.

How did you get +5 Informative spouting drivel of this kind?

Re:why xenon?

[evanbd]

Because it's correct. You can put a variety of particles in the front of an ion engine and have them come out the back. The simplest approximation for what speed they come out at is that they all have the same kinetic energy, rather than the same momentum or velocity. Obviously all three change in the process, but the governing equation is closer to "KE += x" than anything else simple. Which makes sense, because the ion is presented with an electric field over a distance -- force times distance is energy.

Re:why xenon?

[owndao]

Actually Xenon is expensive because it is rare. See http://en.wikipedia.org/wiki/Xenon. And, you are correct about about specific impulse being more complicated than just mass. One can get a simple idea of what can/needs to change when one considers that energy is conserved. To increase the kinetic energy of the craft one must apply at least that amount of energy toward acceleration with conservation of mass and energy as it is.

Re:why xenon?

[evanbd]

Xenon isn't too expensive -- it's expensive enough to make testing obnoxious, but still quite cheap compared to the cost of launching chemical propellants. Interestingly, it got a lot cheaper with the fall of the Soviet Union -- the Soviets only had one model of air liquefaction plant, and since there was only one it had a Xenon tap. They didn't have a lot of uses for it, so they stored it (it was valuable, after all). Then, after the fall, they started selling it, and of course a lot of the equipment is still around, so even after prices recovered total supply was higher.

Talking about adding energy to the craft isn't a terribly useful concept in rocketry, since it depends so much on your frame of reference. Delta-v is much more directly relevant. Of course, you can solve the equations any way you choose, but for a good intuitive sense, delta-v is the metric to use (generally). One obvious case where paying attention to the spacecraft kinetic energy is useful is when looking at delta-v penalties for doing burns higher up in the gravity well (or, inversely, gains for doing them low down as in some forms of slingshot maneuver).

My point about kinetic energy wasn't anything that complicated, though -- it was simply that if you vary the mass of the ion you're using as propellant, the kinetic energy of that ion when it leaves the engine stays the same -- whereas the momentum and velocity change (to first order approximation, anyway). So when looking at the engine behavior, and considering alternate propellants, that's the model to use.

Re:why xenon?

[turgid]

Well, I'll take your word for it. "Obviously all three change in the process," which is quite correct.

Re:why xenon?

[evanbd]

I do build rocket engines, both professionally and as a hobby. Not ion engines, but I have a passing understanding of the physics involved. I know that KE, momentum, and velocity are related ;)

Re:why xenon?

[turgid]

I do build rocket engines, both professionally and as a hobby.

Is building your own rocket engine hard? I mean, making sure it doesn't melt or explode?

Re:why xenon?

[evanbd]

Most hobby engines (including mine) are ablatively cooled -- the combustion chamber is lined with something (usually an epoxy/paper composite, or something similar -- remarkably closely related to Apollo-era heat shields) that chars and outgases, forming a "cool" layer between it and the combustion gases, thereby reducing heat flow. A 1/16" liner will function for 5 seconds or more without any particular design effort, and that's long enough for most amateur rocketry work.

Making them not go boom just takes paying attention to the design. For solid propellants, there's a burn rate (that's dependent on pressure), and then you just have to balance the nozzle throat size against the burning surface area to make sure that it has enough area to escape through (so the pressure isn't too high), but little enough that the pressure is high enough to produce thrust. Then you have to make sure the casing is strong enough to support that, taking into account safety margins and such.

If you're interested, the place to start is probably with commercial motors and either kit-built or scratch-built rockets, and then moving on to potassium nitrate / sugar propellants. Tripoli is the major group that organizes launches (they'll handle details like sites and insurance); there should be a launch at least somewhat within driving distance, and people are generally quite friendly to spectators -- but get in touch with the launch organizers first. Commercial motors are a little pricey (expect to spend perhaps $70 on the motor and $30 on propellant for an I-class motor -- sufficient to launch several pounds of rocket to a few thousand feet), but the reusable motors are well made and provide excellent casings for custom solid propellant work. Richard Nakka has a most excellent page discussing sugar propellants, both in practice and in theory.

My work is with nitrous oxide hybrids, and is somewhat documented at HybridSky. It assumes you have some working knowledge of how hybrid motors work, though; Nakka's site is a much better starting point.

Interesting...

[TFer_Atvar]

I'll have to keep an ion this.

Re:Interesting...

[jd]

You only need the merest whisper of an ion propulsion system story and Slashdot users will go atom with puns.

Re:Interesting...

[Dracophile]

Two atoms were walking down the street and one says to the other, "hey, I think I lost an electron." The other says, "are you sure?" The first one replied, "yeah, I'm positive."

bad idea

[ILuvRamen]

Xenon isn't exactly in great supply. I think they might want to rethink that and design it with a more common material. But sweet that they're finally testing an actual ion drive.

Re:bad idea

[wizardforce]

Xenon isn't exactly in great supply

Xenon is present in our atmosphere at roughly 1 part in 180 million and so its cost is about 1 dollar per gram. considering it costs about 25 dollars a gram to launch things into orbit, Xenon isn't that bad when you consider that just a fraction of the fuel is required for the same thrust as chemical fuels. It is used because it is more easily ionized than the higher "inert" gases, is relatively un-reactive and is more easily utilized in the engine, as it is already a gas.

Re:bad idea

[morgan_greywolf]

Xenon is apparently plentiful enough to be in most of many so-called "neon" signs: The gas that's in "neon" signage isn't always neon -- different gases are used, including argon, krypton and xenon. Neon gives a reddish-orange glow. If it's more blueish, it's probably krypton or xenon.

Re:bad idea

[actionbastard]

Xenon is used because it is the heaviest of noble gases.

You'd best bone up on your Newtonian physics.

Re:bad idea

[doctor_nation]

It is expensive, but it has great performance compared to almost all other materials (the one better is mercury...). Sure, you can use other materials, but the efficiency drops like a rock. I think the use of Krypton or Argon is being looked at for some thrusters (maybe not ion thrusters). Oh, and ion thrusters have been around since the 60's, and Hall thrusters before that (made by the Russians). They've flown on a lot of missions already- this one isn't at all remarkable to be honest. Deep Space 1 was a lot more impressive.

Re:bad idea

[Brett Buck]

There have been very similar drives for at least 30 years. This is just a new model. I spent all day in a meeting discussing control system issues related to the use of a very similar engine on our spacecraft.

      Xenon is a good propellant since it's easy to ionize.

          Brett

Re:bad idea

[v1]

sort of what I was wondering. I suppose there's no escaping physics though, you have to use something for fuel. (ok "fuel" is a bad word for it, how about "mass"?) I was hoping ion drives could run without losing mass, but that's the only fundamental way to accelerate something in a vacuum isn't it? by throwing mass overboard, preferably at high speed? (the high speed part being what the ion drive specializes in)

I suppose the only way around this would be a solar sail, or perhaps such a thing powered by some sort of a beam (of mass, energy, or a combination of the two) from the origin.

Re:bad idea

[CastrTroy]

What about Radon. According to my periodic table Radon would be the heaviest noble gas. Not countijng Ununoctium of course, but that's a synthetic element.

Re:bad idea

[Anonymous Coward]

Well, Radon has some, let's say, unusual side effects, including a strange tendency to make your neon sign glow mysteriously without turning the power on....

Re:bad idea

[Lord Apathy]

If xenon is an inert gas, will any inert gas do?

Re:bad idea

[evanbd]

The 3.8 day half-life might cause some difficulty. Not to mention that the short half-life implies a high radiation output. Generally, it's a good thing not to have your propellant tanks glow on their own.

Besides, $6000 per milliliter is expensive, even by aerospace standards.

Re:bad idea

[davolfman]

Radon has this annoying tendency to emit alpha radiation. Alpha radiation does nasty things to any materials it contacts by embedding helium nuclei in their structure. That and it has a half life of less than 4 days so it's not really suitable for any sort of long term use, and if you're using an ion drive you've already chose to do things the long, efficient way.

Re:bad idea

[Anonymous Coward]

for bluish signs it is actually argon with a touch of mercury. argon on its own is a dim purple color which is too dim to see with other lighting, but is really neat in a very dim room. the added drop of mercury causes the chemical to fluoresce bright blue. All other colors are by putting a phosphor coating on the inside of the tubes, which emits different colors when excited by the argon-mercury mixture. Neon is only used for the classic tomato orange color, or the deep red or purple which is done with different colored glass tubing. Krypton and xenon can also be excited to emit light, but they require more energy than is commercially viable, and are rather dim.

Re:bad idea

[rilister]

I'll pass by most of that comment, but you might be interested to know that, amongst many others, NASA's Deep Space 1 probe is in space right now using an (older design of) ion drive.

It uses Xenon atoms

http://en.wikipedia.org/wiki/Ion_engine#Deep_Space_1

Re:bad idea

[morgan_greywolf]

Krypton and xenon can also be excited to emit light, but they require more energy than is commercially viable, and are rather dim.

Pffft. You're talking to a guy who grew up in the sign business. Xenon and Krypton are often used because they are dimmer -- typically for "accent" neon where you don't typically want the full garishness of something like argon or neon.

Re:bad idea

[CastrTroy]

I'm not saying it would be better suited to the purpose. All I was refuting was the fact that Xenon is the heaviest noble gas. I don't think Radon would be the best thing to use, but that doesn't disprove that fact that there are heavier noble gases than Xenon.

Re:bad idea

[Anonymous Coward]

Radon has this annoying tendency to emit alpha radiation. Alpha radiation does nasty things to any materials it contacts by embedding helium nuclei in their structure.

OTOH, you don't heave to spend any energy to ionize Radon, as it readily ionizes itself. Just keep high positive potential on the walls of the chamber (tank) to fend of alpha particles.

Re:bad idea

[sudog]

You are being pedantic. If you had made an effort to actually comprehend the point in the OP's posting, you would have simply added the "heaviest usable" in there somewhere and moved on. As it is now, all it looks like you're doing is rationalising why you weren't completely wrong. However, technically the OP you responded to was describing *why* Xenon was used *in propulsion* and therefore by proposing Radon as *an alternative to that* you were by your own abstract form of reasoning as presented in your clarification--still fucking wrong.

Cool but...

[Fluffeh]

As cool as it is, these engines are pushing the xenon gas out at over 40,000m/s, they still only push out 40kg (http://news.bbc.co.uk/2/hi/science/nature/7346789.stm)if the stuff before the fuel runs out. As much as I am all for cool new space stuff, I am also a fan of manga and sci-fi. Some of these guys should watch more Star Trek - we need THOSE sort of engines powering our experiments.

Re:Cool but...

[Nyeerrmm]

Any kind of rocket propulsion will inherently have these limits. Whether its a chemical rocket at 3000m/s with lots of thrust, an ion thruster (which aren't that uncommon, not sure why the article says it is) with 30000m/s and fractions of newtons, or something advanced like VASMIR with high exit velocities and relatively high thrust (and large power requirements), you run into the basic problem that you have to carry all your fuel with you, and the thrust you get out of it is limited by the velocity of the fuel, for which the power requirements increase my v^2 (E=1/2 m v^2).

The only ways I can see to get away from this rather immutable law of nature is to use something like solar sails, which are cool but have a lot of engineering work still needing to be done, or designing a whole new kind of physics that lets us warp space to our needs. I'm pretty sure thats how even the impulse engines work on Star Trek, since if it wasn't, the Enterprise would probably have to be mostly fuel tanks. Of course if you're working on those physics, good luck, I hope you figure out.

Re:Cool but...

[evanbd]

Alas, the energy requirements are tough. About the only option is some form of nuclear propulsion -- though there are a number of interesting varieties of nuclear. The original Orion concept is an interesting one -- I've been reading some of the original cost estimates (pdf), and they get quite interesting -- $3.30 per kg for a Jupiter mission, assuming reasonable costs for the plutonium. (Not 2008 dollars, and I don't know what the actual price of plutonium is these days.)

More modern interesting proposals include the nuclear salt-water rocket and the fission fragment rocket. Of course, neither of these is particularly well suited to in-atmosphere work, and you have to be careful where you point the exhaust (but since it's moving faster than solar escape velocity, that's a relatively simple problem).

Re:Cool but...

[CastrTroy]

Well, if you have 40 kg of fuel being propelled at 40,000 m/s out the back of the spaceship, then assuming and equal force pushing the fuel backwards pushes the spaceship forwards, this would mean that a 5000 KG spaceship would be travelling at 320 m/s, which is 1152 KM/h, which is just under Mach 1. Of course, this assumes that everything is 100% efficient.

Please feel free to correct me. I am not a physicist, and I'm probably completely wrong about this.

Re:Cool but...

[timmarhy]

that's how fast you'd be accelerating, so given enough time you'd be going a lot faster.

Re:Cool but...

[camperdave]

Those engine suggestions all spew radioactive exhaust. What you want is a gas core nuclear rocket. The reactor uses radioactive gas contained in a closed vessel made of a material that is transparent to ultraviolet. The propellant can be hydrogen, which get heated by absorbing the UV. Because the reactor fuel is already a gas, there's no danger of a meltdown, and because the system is closed, there is no radioactive exhaust, just hot hydrogen.

Re:Cool but...

[evanbd]

No, that's not what I want. Current estimates put maximum Isp for closed cycle gas core rockets low -- perhaps 2000s or so, maximum. That's far better than chemicals, certainly, but not anywhere near what the other designs are capable of. The open cycle designs also spew radioactive exhaust.

For the first stage, chemical rockets will do just fine. Once you're out of the atmosphere, the high-Isp nuclear designs are fine -- just make sure the flamey stuff misses the Earth, which is a relatively trivial trajectory constraint, and it'll leave the solar system.

There are, of course, nontrivial issues about reliability and accidents and such. Those, along with some significant engineering headaches, will keep any of these designs from becoming reality for quite some time yet.

Re:Cool but...

[camperdave]

Ah, but what you really want is the heavy lift, first stage stuff. After all, the point is to get off of this rock and out into the big wide black. For that, you need a clean propellant and lots of power. We're pretty much at the limit of what chemical rockets can do. So, we need to go nuclear, and GCNR is the way to go. Once you're out of the gravity well, then you're free to do whatever.

Re:Cool but...

[evanbd]

GCNR is nice, but chemical rockets will work too, with a lot less hassle. It doesn't have to reach orbit -- a high enough trajectory that the exhaust from the high-energy stage misses the Earth is good enough. The paper I linked above discusses options for an Orion stage launched from a S-IC booster (first stage of Saturn V).

It's also worth noting that chemical rockets work just fine to the Moon and Mars -- the cost barriers are a result of design decisions, not because it has to be that way. It's not until you start trying to go beyond Mars that nuclear propulsion becomes as important.

Still just a curiosity...

[OldFish]

As long as the ion drive has to carry all the mass it'll ever use it will never be useful for seriously long trips. It would need to vacuum up stray particles as a mass source for that. But it's mildly interesting anyway.

Re:Still just a curiosity...

[bagboy]

couldn't they just tie a Roomba to the back of the space craft?

Re:Still just a curiosity...

[calebt3]

Like this?

Re:Still just a curiosity...

[JustOK]

It would be better on the front, but, still, it wouldn't really get into all four corners of space.

Re:Still just a curiosity...

[evanbd]

What kind of mission delta-v did you have in mind, exactly? Some of the modern nuclear engine proposals can get single-stage delta-v over 1% c (nuclear salt water rocket and fission fragment rocket, for example). There is some debate about whether going even that fast in interstellar space is feasible, I believe. Besides, modern analysis indicates that there isn't enough hydrogen in the local neighborhood for Bussard's proposal to work, even if you manage to build a functioning fusion reactor for it.

Re:Still just a curiosity...

[Nyeerrmm]

It depends on how long you mean. Its certainly still a long way from being able to run an interstellar mission, but for an interplanetary mission it provides a lot of benefits. Lower mass and faster travel times are the primary ones; even though its low thrust its constant thrust so it can build up, particularly on longer missions (think to Jupiter rather than the moon).

Also, the one problem I see with the idea of 'vacuuming' space, beyond the obvious engineering problems, is that in order to use them in a system you'd lose more momentum than you'd gain, at least using engine technology of this sort. Imagine it from the spacecrafts point of reference, all the very rarefied gas is coming towards it at the speed the spacecraft is traveling in the inertial frame. As it captures the gas, it has to slow it down to stationary, and then speed it up and send it back out; in doing so unless the exhaust velocity is faster than the spacecraft velocity, you're going to lose momentum rather than gain it.

Now if you could come up with a way to ionize the gas as it passes and use magnetic fields to accelerate it further (like a swimmer or an air-breathing engine) that would certainly be interesting.

Re:Still just a curiosity...

[Anonymous Coward]

I think that is the whole point of an ion drive. You always need to carry all the mass on board(being that there isn't much mass in space to shoot in one direction to propel you the other-- conservation of momentum). The idea behind an ion drive is to carry much less mass and shoot it out at much higher speeds.

Re:Still just a curiosity...

[evanbd]

The drag problem isn't that clear cut. The reference frame isn't "spacecraft velocity" in any sense you'd normally think of it -- it's the solar wind, at ~500,000 km/s. In interstellar space it slows enough that fusion engines could easily have a higher exhaust speed, up to several % c spacecraft velocity. The problem becomes one of collecting enough hydrogen, and getting it to fuse. In-system, though, you can use the solar wind drag to your advantage, at least if you want to head outbound. Wikipedia has a good discussion of the issues involved.

Re:Still just a curiosity...

[Lord Apathy]

indicates that there isn't enough hydrogen in the local neighborhood

I've heard this before, this and there are many other reasons that don't make a pure Bussard ramjet possible. A few years ago I came across these guys. While I don't know how realistic their ship but one thing that did catch my eye was this.

I was especially fascinated by how they address the fuel problem. They created something called an acceleration track. The idea is that fuel is launched before the ship is in packages. The ship would over take each fuel and supply package as it left the system. I always thought that was a elegant solution to the fuel and supply problem.

Re:Still just a curiosity...

[OldFish]

well, the concept is probably doomed. The better solution is a hybrid light drive (yes, massless photons have momentum) and an ion drive that uses spent fuel as mass. Just my 2c

Re:Still just a curiosity...

[DerekLyons]

The mass of the fuel and the mass of the engine are pretty much meaningless - what kills ion engines is generally the mass of the power supply.

Re:Still just a curiosity...

[Anonymous Coward]

Are you sure about that? My understanding regarding interplanetary missions is that most of the fuel has to be spent in getting out of Earth's gravity well, and then braking on the other side (when applicable). That sounds like something a low, constant thrust won't be able to help.

Once you're in interplanetary space, almost all of your velocity comes from the relative motion of the Earth with respect to the target. It would take order of magnitude developments in propulsion to become comparable. Is that really something our ion drive can achieve?

Re:Still just a curiosity...

[fractoid]

Yes, but... actually, "Roomba Ramjet" sounds a lot cooler than "Bussard Ramjet", you may be on to something. Stick the roomba on the front, though, to clean up all that pesky space debris!

Re:Still just a curiosity...

[delt0r]

The speed of light is 300,000 km/s. So i think your figure on the solar wind velocity might just be off a tad.

Re:Still just a curiosity...

[evanbd]

You are, of course, correct. That should be m/s.

Re:Still just a curiosity...

[bug]

An ion drive, along with most forms of propulsion, would indeed run out of juice for the reasons that you mentioned. If you want to keep the peddle to the floor during your trip across the stars, then you might want this instead:

http://en.wikipedia.org/wiki/Bussard_ramjet

A system like that would take a helluva beating. I'm a bit skeptical.

Re:Still just a curiosity...

[Hucko]

So you are saying, it would make a great brake?... now if only we can get approach the speed of light...

Re:Still just a curiosity...

[dreamchaser]

As long as the steam engine has to carry all the mass it'll ever use it will never be useful for seriously long trips. It would need to stop frequently for more coal and water as a power source for that. But it's mildly interesting anyway.

Moral of the story: you have to start somewhere.

Re:Still just a curiosity...

[justthinkit]

There is some debate about whether going even that fast in interstellar space is feasible

It seems to me that the faster a spacecraft travels, the more damage is done when a random chunk of whatever collides with the spacecraft. Outside of comet tails and meteor showers, I am not sure there are that many random chunks of matter in space but travelling at 1% of the speed of light when you hit a speck of sand, for example, must be a bad thing. Has this been quantified? Would a steel plate at the front of the spacecraft help?

Re:Still just a curiosity...

[Bloodoflethe]

Yes, that's part of the reason TIE fighters never did very well in interplanetary travel, even in-system.

Re:Still just a curiosity...

[Bloodoflethe]

Space pirates would love that solution too!

Re:Still just a curiosity...

[evanbd]

The right shield is probably a very thin shield, well in advance of the craft, and then a heavy shield -- the dust spec explodes on contact with the thin shield, and then has some time to disperse before hitting the actual armor. Note that a 1mg dust spec at 1% c has the energy content of 1kg of TNT. The armor should be doable, but it's not trivial -- and as you get much faster, it gets *really* nontrivial.

Ooo

[dreamchaser]

TIE Fighter's, anyone? (Twin Ion Engine, for those of you who are not true geeks)

Re:Ooo

[cashman73]

Forget the twin ion engines, dude! I want a fracking beowulf cluster of 'em! :-)

T.I.E.

[Anonymous Coward]

In Star Wars, the name "TIE fighters" was actually an acronym for Twin Ion Engine.

So I'm wondering if this new engine makes a cool sort of tiger-roaring sound when it's running.

Cryogenic pumps can be heard in the background, whistling away like tiny steam engines.

Oh... more like a Model T, I guess. :-(

Re:T.I.E.

[calebt3]

From Wikipedia:

Sound designer Ben Burtt created the distinctive TIE fighter sound effect by combining an elephant call with a car driving on wet pavement.

Re:T.I.E.

[doctor_nation]

Since these thrusters only operate in a vacuum, I'm afraid they don't make any sound at all...

Re:T.I.E.

[Hucko]

Referencing the engine, yes they do, but you need at the very least to have a primitive stethoscope to hear it. A laser should be able to detect the vibrations. Unless the electric field is stationary, in which case I am wrong and you are right. Actually the cooling pumps would be producing the sound if nothing else did.

You mean it's NOT because ....

[Ungrounded Lightning]

TIE Fighter's, anyone? (Twin Ion Engine, for those of you who are not true geeks)

You mean it's NOT because they're shaped like bow ties?

Darn!

Re:You mean it's NOT because ....

[coren2000]

I find your lack of fashion-sense disturbing.

Re:You mean it's NOT because ....

[RoboRay]

Vader, accessorise him!

Re:You mean it's NOT because ....

[Anonymous Coward]

What does a Star Destroyer wear to a formal dinner? ...

A bow TIE!

Re:You mean it's NOT because ....

[SimonInOz]

TIE fighters conjures a wonderful image of two Dilberts in some sort of battle.

Evenly matched, of course.

Re:You mean it's NOT because ....

[Adambomb]

I thought Carrot Top wasn't allowed back here.

Re:You mean it's NOT because ....

[smithmc]

TIE Fighter's, anyone? (Twin Ion Engine, for those of you who are not true geeks)

You mean it's NOT because they're shaped like bow ties?

Nah, NASCAR wasn't big enough back in '76 to be worth going after the "bowtie crowd".

No no no. Faraday effect!

[Ungrounded Lightning]

Ion engines ... make use of the fact that a current flowing across a magnetic field creates an electric field directed sideways to the current.

No it doesn't. It creates a MECHANICAL FORCE directed sideways to the current. It's the Faraday effect, which is what drives electric motors.

It's also how you can use the Hall effect to determine whether the majority current carrier is positive or negative: The carriers are accelerated toward the same side of the conductor, so the sign of the hall voltage tells you whether you have more + or - charge carriers.

(IIRC It's how they showed that Franklin guessed wrong when he assigned + and - to charges, leading to the sign of "classical current" and the points of arrows on semiconductor diagrams being opposite to the direction of electron flow.)

Obligatory Niven-Known Space reference

[Nefarious Wheel]

You're both right.

http://en.wikipedia.org/wiki/Bussard_ramjet

http://en.wikipedia.org/wiki/Tales_of_Known_Space

There are a lot of unanswered questions about this technology, but I'd quote AC Clarke at you if someone says it's impossible.

Twin Ion Engine

[Anonymous Coward]

I'm keeping my eyes peeled for a twin ion engine

Makes me pine for the old days...

[actionbastard]

of the NRX program. NRX (NERVA [NERVA - Nuclear Engine for Rocket Vehicle Application] Reactor-Experimental Research) was the engine that would power the spacecraft that was supposed to take us to Mars and beyond. Unfortunately it was cancelled because of 'environmental concerns' http://www.fas.org/nuke/space/kiwi.gif.

Re:Makes me pine for the old days...

[Anonymous Coward]

Unfortunately it was cancelled because of 'environmental concerns' http://www.fas.org/nuke/space/kiwi.gif. Don't be a dumbass. The caption on the page that photo belongs to reads "This KIWI-B type reactor was deliberately destroyed on January 1965 by subjecting it to a fast excursion. This test was intended to confirm theoretical models of transient behaviour."

The project was canceled because they had an intractable exhaust problem. The engine would actually emit huge amounts of uranium and carbon from the lining of the reactor during use, creating a pollution and service life problem. It's also true that nobody wanted to risk a nuclear explosion in the atmosphere over populated areas just to make space exploration cheaper, but there were plenty of other problems with the system.

Re:Makes me pine for the old days...

[olman]

The project was canceled because they had an intractable exhaust problem. The engine would actually emit huge amounts of uranium and carbon from the lining of the reactor during use, creating a pollution and service life problem. It's also true that nobody wanted to risk a nuclear explosion in the atmosphere over populated areas just to make space exploration cheaper, but there were plenty of other problems with the system. That was 40 years ago, thought. Doesn't mean that with all the advances we've made in materials science and with applications from fusion research nuclear propulsion shouldn't be actively researched.

Good luck proposing nucular engine project for goverment funding, thought.

In any case, sans the cool orion nuclear impulse drive, I don't think any of these things would be appropriate to do heavy lifting in atmosphere. Would be good for a propulsion when you're in the orbit for much the same reasons as ion engine, except you can have proper thrust..

Re:Makes me pine for the old days...

[cheesybagel]

IMO Project Timberwind was much more interesting.

Spock's Brain

[Anonymous Coward]

"Brain, brain, brain, what is brain? It is controller, is it not?"

"Either it's an atomic pile a hundred miles in every direction or ... ion power."

Not news, and not impressive

[doctor_nation]

The T5 is hardly a new thruster- it's probably been around for 10 years or more. And it's not that impressive in terms of performance for an ion thruster. More impressive ion thrusters exist, like the NSTAR thruster they used on Deep Space 1. That provided main propulsion and lasted way longer than expected, so DS1 got a lot done. Or look at the nuclear-reactor powered ion thrusters that were under development until Bush decided we were going to Mars (NEXUS and HiPEP).

Ion thrusters (and electric propulsion) have been around since the 60s. Back then, they used mercury for propellant and they had grid voltages of 13kV. Tons of ion thrusters have flown already and are already doing stationkeeping on satellites right now.

Re:Not news, and not impressive

[olman]

Or look at the nuclear-reactor powered ion thrusters that were under development until Bush decided we were going to Mars (NEXUS and HiPEP). Maybe you explain to us forehead slope challenged viewers why nuclear ion engine wouldn't be perfect for something that is going to Mars?

Re:Not news, and not impressive

[doctor_nation]

Not enough thrust, mainly. You could get there with a lot less fuel, but it would take a very long time. Even with a direct-launch rocket, they're looking at 6 months (I think). So they'd be great for getting supplies to Mars, because you'd be able to send a ton of stuff, and it wouldn't matter so much that it took a long time (so long as you have a steady chain). But for people, it would be a very long and boring trip (as if 6 months isn't bad enough!).

There may have been some backlash against the nuclear reactor too- I'm not sure about that. It's funny, because those programs came about because when Bush got into office he allowed for the possibility, then a few years later essentially killed them by mandating that most NASA money had to go towards getting a man to Mars.

Re:Not news, and not impressive

[Anonymous Coward]

Actually the Anti-nuclear sentiment came about after the Columbia disaster in 2002. They figured that if a nuclear reactor were to experience a malfunction on liftoff, the possible damage would be much greater than just falling debris.

We've had nuclear powered satellites in the past, the Viking probes I believe had nuclear generators on them, but again that was back in the day when NASA was recieving ~15% of the national budget, and not less than 1%, like now.

And you're right, Boeing has been using XIPs (Xenon-Ion Propulsion) engines for a long time now on their satellites...even the latest XM Radio satellites have it, so its certainly not anything novel.

Re:Not news, and not impressive

[olman]

Then again, with the nuclear reactor you have all the power anyone could ask for, in relative perpetuity.

As an EE engineer I could imagine limitless energy source would allow you to have several particle accelerator stages and you could use the waste heat to do all manner of useful stuff inside the space vehicle. Can't do that with batteries and/or solar panels.

There are also the more "radical" nuclear drives I've seen proposed without touching the good old nuclear impulse engine.

One proposal was something like you "blow" gas through the reactor so it works a bit like water cooled reactor and heats up to plasma levels, giving you rather respectable thrust.

Plus, well, if you're going to mars, I rather imagine it'd be good to have your very own nuclear reactor while you're there. Energy is life as they say.

Hit the wayback machine Mr. Peabody

[zazenation]

I remember back in the 60s that even Jim Kirk was impressed with "Ion Power".

It followed one of those cosmic dramatic pauses after Spock gives Jim the technical skinny on the "alien vessel" and Kirk speaks out in one of his classic redundant clarifications for the home viewer and says:

"Ion Power" in a hushed, almost reverent tone. (can't remember the name of the episode, Maybe it was the one with the Gorn ---that frog head alien with asthma that Kirk nailed with the diamond/gunpowder cannon)

I mean really, he can mix matter and anti-matter at will, modulate photons into gigawatt phaser banks and he starts going all wistful over ---
"Ion Power"?

Star Trek scripts, gotta love 'em!

Like Kirk's glaring scientific faux pas where he says the " --- the magnitude is amplified ONE to the 28th power"...

Re:Hit the wayback machine Mr. Peabody

[scottrocket]

I believe it was "Spock's Brain", but there may well have been another episode with ion power.... (Either it was ions, Scotty surmised or a nuclear pile 100 Km in diameter - yes, you do have to love them 'Trek scripts).

You know what this means...

[milbournosphere]

Now I can finally finish the TIE Fighter thats been in my garage all these years! Now the star destroyer, that won't be so easy....

Ions and magnetic fields

[EmbeddedJanitor]

Measuring magnetic fields with an ion generator nearby sounds a bit disturbing. They better turn it off while making measurements.

You've got to say these obvious things because the space boffins seem to forget now and then.

Re:Ions and magnetic fields

[atomicdragon]

Measuring magnetic fields with an ion generator nearby sounds a bit disturbing. They better turn it off while making measurements.

You've got to say these obvious things because the space boffins seem to forget now and then.

Why? Magnetic field measurements are very common on plasma experiments, which can have similar or even more severe environments than this ion engine. Turning the plasma/ions off kind of defeats the purpose of most such measurements.

Re:No no no. Faraday effect!

[Anonymous Coward]

First of all, it does create an electric field, just as the summary said. I have no idea what you meant by a "MECHANICAL FORCE", since the only thing that can create a force on ions is either an electric or magnetic field-- so one of those two has to be there! Also, it is not called the "Faraday effect", that is an effect of magnetic fields on light polarization-- nothing to do with this. It's the Hall effect, which you later mention anyway.

The reason it creates an electric field is the same as the reason there is an electric field in the Hall effect. The negative ions (electrons) are much more mobile than the positive ions (charged xenon atoms), since they are much less massive-- same as in a solid, except here the positive ions are slightly mobile (not in a crystal lattice.) So, the electrons whiz away from the positive ions, causing a net electric field to form.

But, you were spot on about the hall effect, and you did recall correctly about Franklin.

Yer both wrong/right

[starglider29a]

The only thing that matters is VELOCITY, not momentum. Mass flow RATE. At least if the test is "efficiency". That is what we (rocket scientists) call "Specific Impulse" (Isp). When you do the Delta-V equation, it's only

DeltaV = Isp*ln (m1 - m2) if memory serves. If not, someone will fix it for me. Nothing about momentum. The difference in mass is the only factor for a given propellant/engine combo

Whatever you can get out of the poopchute the fastest is the most efficient. Without speaking of the ionization process, hydrogen is prolly the best, being the lightest, BUT it's density is so low that the mass to contain it lowers the return. Recall that Clarke's Discovery had ammonia instead of hydrogen as Sakharov propellant, because it was denser (smaller, lighter tanks). And thus, it didn't leak out after 9 years (2010 - 2001)

Xenon is probably an optimum of mass and density. Plus whatever they said about ionization.

Re:Yer both wrong/right

[evanbd]

That's ln(m1/m2); units analysis is sufficient to show your version is wrong (you can't take the log of a quantity with units in it).

The problem is that in chemical rocketry, Isp and density Isp matter, but in ion engines energy efficiency matters too. Raising the Isp raises the mass efficiency, but at high Isp the energy efficiency drops. Since the solar cells and power electronics are heavy, energy efficiency matters. For most current applications, ion engines have more Isp than they need, even with xenon. Besides, excessively long burn times add a delta-v penalty for doing too much of the burn high in the gravity well.

Re:Yer both wrong/right

[starglider29a]

Thanks for the correction. These days, I'm doing more with ASP than ISP. In fact, ISP now means something else.

Re:Yer both wrong/right

[dino2gnt]

>Whatever you can get out of the poopchute the fastest is the most efficient.

So we should power the spacecraft with laxative burritos?

Just one engine? We need more ...

[Spectrum_Leap]

I can't wait for Twin Ion Engines!

why Xenon

[Jeff1946]

The main reason to use xenon is that you can ionize more of it due its larger size (ionization cross section), most the gas in these trusters is not ionized and is wasted. The ionization energy is insignifcant (tens of volts) compared to the expulsion voltage (tens of kilovolts).

Re:No no no. Faraday effect!

[evanbd]

It all depends how you do the math. In the reference frame of the magnetic field, there is a direct force on the moving charged particle, and no electric field is present beyond what the charged particle itself creates. In the frame of the particle, the magnetic field shows up as partially an electric field, which is where the force comes from (since the particle isn't moving in its own reference frame). See special relativity and the Lorentz transformation.

Higher Efficiency?

[Doc Ruby]

Are these ion engines more efficient in turning the power stored in their fuel into kinetic energy of the vehicle than the efficiency of, say, liquid fuel rockets we use to launch satellites and the Space Shuttle?

Re:Higher Efficiency?

[aXis100]

Not so much efficiency, the main benefit is reduced weight.

Simply put, they dont have "fuel" in the conventional sense. They use electricity (which can be sources externally or generated oboard from a nuclear source) to exject a reaction mass at high speed. Over time this reaction mass will be consumed, but get far more benefit from it that they would with normal combustible fuel.

Re:Higher Efficiency?

[Urkki]

Yes, much more efficient, if by efficient you mean how much mass you need to achive certain change in velocity.

The problem is how fast they can convert the energy of the fuel into acceleration. I think we're still a long way from an ion engine that could lift even it's own weight on Earth surface, let alone weight of an entire spacecraft of any kind. A current or foreseeable technology ion engine on the surface of Earth will just sit there, even on full power.

So you still need something with a lot of thrust to get to a stable orbit (current option: chemical rocket; future options: nuclear rockets or laser "rockets" or space elevators). Once on stable orbit, you can use all the time you want to slowly but efficiently accelerate with an ion engine.

Re:Higher Efficiency?

[Doc Ruby]

By "efficient" I mean how much potential energy in the fuel is converted by the engine into kinetic energy of the vehicle. I suppose that a smaller reaction mass that's expended by the engine per distance means less reaction mass carried before it's expended, which means the vehicle can be less massive, therefore require less energy to move. But if the lighter vehicle is overbalanced by a less efficient energy conversion from potential in the fuel into kinetic of the vehicle, then it's not really worth it. It's just a cool way to build a TIE Fighter replica.

Re:Higher Efficiency?

[Doc Ruby]

Well, they do have conventional fuel, just not conventional for rockets, which use an unconventional fuel that's also used as the reaction mass in exhaust.

Has anyone tried powering an ion engine vehicle with an external laser? How about a laser-driven interplanetary scoop that collects ions from interstellar space to drive as reaction mass powered by that remote laser?

Re:Higher Efficiency?

[Urkki]

Ok. The problem with that is, how do you define what "potential energy of fuel" means in ion engine. It has separate electric energy source (with nuclear fuel, or solar energy and no fuel at all), and separate propellant (like Xenon) with almost negligible mass.

So you'd have to make a lot of assumptions (type and mass of energy source, amount of fuel on board, amount of propellant on board) to calculate efficiency like you say.

But for any sensible assumptions, the efficiency will be much much higher than with chemical rockets.

Re:Higher Efficiency?

[Doc Ruby]

Assumptions are not necessary. We're talking about a specific implementation of an ion engine, not it's theoretical efficiency.

This new engine has a power source that has its own efficiency converting its fuel to electricity, which is the starting point. Then there is the efficiency of the ion engine itself converting that electricity to the kinetic energy of the moving vehicle. Multiply those two (fractional) efficiencies together for the total fuel efficiency of this vehicle. That's what I want to know.

There is a larger question that is theoretical, the theoretical maximum fuel efficiency of any ion engine vehicle. What is the most efficient conversion of fuel by any power source into energy that an ion engine can use to convert into kinetic energy of the vehicle. It's the same exercise, but you don't have to build it to "measure" its efficiency. It's worth knowing because then we can see what percentage of theoretical efficiency this new actual engine gets, of its theoretical efficiency.

And then those efficiency answers can be used to tell whether this engine, and its whole class of engines, is really interesting as a useful device. Whether it's really better than chemical rockets. Or whether it's exciting only for Star Wars TIE Fighter reenactors.

Re:Higher Efficiency?

[Urkki]

Ah, this particular device. Well, it uses solar power and (according to TFA) 40 kg of Xenon, which will last for 20 months, providing constant thrust. I'm not sure how you'd go about determining the efficiency in any meaningful way.

I guess you could sum up the weight of ion thrusters, Xenon tanks and extra solar panels needed by it, and compare that to weight of a chemical rocket thrusters and rocket fuel capable of giving same average thrust for the same perioid of time.

However, if we just consider Xenon (exhaust velocity 50km/s) vs. Hydrazine (exhaust velocity 1km/s) and forget engine mass, then 40kg Xenon is worth 2000kg of hydrazine. Since the entire craft weight is only 1000kg, I'd say Xenon ion engine is much more efficient.

Re:Higher Efficiency?

[Doc Ruby]

I'd compare the energy of the incoming solar power, about 1KW:m^2 at sunny Solar Noon, to the vehicle's velocity after some time under solar power, applying the usual E = 1/2 * m * v^2 kinetic energy measurement.

That is the way we measure the energy efficiency of any machine.

say what now?

[ILuvRamen]

I thought I learned in HS that no noble gasses could be ionized because all their electron shells were already perfectly full. How can Xenon run an ion drive?

Re:say what now?

[Ihlosi]

I thought I learned in HS that no noble gasses could be ionized because all their electron shells were already perfectly full.

They may be harder to ionize than other substances, but it's not impossible to do so. Heck, if they could not be ionized, it would mean that they hang on to their electrons with infinite force ...

Re:say what now?

[Ihlosi]

... which would also mean that you could extract infinite amounts of energy from an alpha particle (which is an ionized helium nucleus ... and energy required to remove an electron from a noble gas is infinite (i.e. a hard "cannot be ionized ever"), then adding an electron to the alpha would release infinite amounts of energy.

Re:say what now?

[ILuvRamen]

oh, so they strip off an electron instead of adding one? I thought ion drives negatively charged the particles before expelling them and you have to add one to do that. I thought adding one was what was impoosible.

Re:say what now?

[Ihlosi]

oh, so they strip off an electron instead of adding one?

Yes.

I thought ion drives negatively charged the particles before expelling them

That would be problematic since it would lead to the spacecraft becoming positively charged over time. If positively charged ions are used, the engine can be designed so that the ions pick up electrons on their way out, so that a neutral plasma is expelled and the charge of the space craft does not change.

Finally... TIE Fighters!

[kickdown]

We just need TWO of those Ion Engines.

Qinetiq

[julesh]

security firm named Qinetiq Security firm? Are people starting to forget that Qinetiq is a privatised government agency (formally known as DERA, the Defence Evaluation and Research Agency)?

Re:Qinetiq

[Anonymous Coward]

Yes, privatized, as in the opposite of public. In all seriousness, though, they do still have strong connections to the UK government, though they they aren't run by it anymore (hmmm, I bet you could say that about any "security" firm)

BTW, I am pretty disappointed with /. commenters. Nobody's mentioned the fact that we've been talking a lot about their North American subsidiary this week, you know the one that runs the SWORDS program?

Re:Qinetiq

[clickclickdrone]

And lets not forget all the drama etc when the press found out how that little deal was managed and how much money the new owners made when the government woefully undervalued it (as per usal).

Re:Qinetiq

[Anonymous Coward]

In a word, yes.

GOCE satellite

[catfry]

The focus of this story is completely wrong. Ion propulsion is kinda old hat, there has been more than just 'a handful' of satellites flying with some form of it, unless your hand is really big. Granted, most of them have been as a secondary propulsion mode and for stationkeeping, but now it is also increasingly being taken up as primary probpulsion for deep space missions.
What is really interesting is the satellite GOCE.
Tasked with mapping out the gravitational pull of earth with very high fidelity, it needs to fly as close to the earth as possible without being dragged out of orbit by the athmosphere, and to remain stable in this very low orbit.
For this reason this is the only satellite I know of where a major design driver was that it be aerodynamic! The ion propulsion is primarily to counteract the constant drag so the satellite maintains it's orbit, and to this end it is projected to be thrusting almost continuously.

UK chucking money around like there's no tomorrow

[Richard Kirk]

"Yet despite this humble appearance, it took 20 to 30 years to develop, at a cost of tens of millions of pounds."

Divide tens of millions of pounds by 20-30 years, and you get an annual cost of some UK engineers and their equipment. Unless, of course the figures aren't right, but I have a feeling that they are not too far out.

I say, dash it all, buck it up you fellows! I know chaps in the RFC who are just itching to slap a couple of ion drives on their kites, what?

Nuclear Pulse Drive

[funkboy]

Research into Ion engines is promising, but every time I see something like this I reminisce about the promises of the nuclear pulse drive.

beta tagging, obviously

[misterthirsty]

Why isn't this tagged with millennium falcon?

Near Light Speed Propulsion Engine Unveiled

[fedrive]

The plasm engine is old stuff with the propulsion power of 1 feather !

Copied from Corporation for Space Transportation Website :

This propulsion technology supplements its nuclear power by using renewable free electrons from space for continued 24 x 7 electron propulsion.

The Space Shuttle using an Advanced Electric Propulsion Linear Electron Beam Particle Accelerator (LINAC) for light speed electron particle propulsion using the Sunyaev-Zel'dovich effect and Birkeland currents is a unique concept. The shuttle would have the capability of paying all of its expenses for the first time !

Dr. Steve Schaefer, Ph.D. Princeton University (Physics), "Calculates if X = 4.3 light-years, then T = 3.6 years. Dozens of stars could be reached in five to six years. In fact, a traveler could even go the Andromeda galaxy (2,000,000 light years) in under 29 years (Ship Time in Years) if a constant acceleration could be maintained." Also see Dr. Carlos I. Calle, PhD, NASA senior research scientist, below on page.

Dr. Schaefer calculates, "If the total distance is X, then the total travel time T is given by expression

X / 2 = (c 2 / g) [cosh (0.5 g T / c) - 1] : T = (2 c / g) cosh -1(1 + 0.5 g X / c 2) "

The NLS propulsion technology has been peer reviewed by several physicists as being valid technology following Newton's and Einstein's laws using invariant mass propulsion.

Present Day Solid Rocket Exhaust is 1,000 to 4,000 m/s with 10^3 N to 10^7 N thrust and a firing duration of minutes.

The Proposed NLS Propulsion uses 300,000,000 metres per second electrons with 1 N to 1x10^6 N thrust and a firing duration of years - decades and capable of developing > 50,000 hp.

The cost per pound for current Chemical Rocket technology is $ 2,000 to $ 27,000 dollars per launch. This generally runs into hundreds of millions of dollars per launch as verified by the industry.

A future spacecraft, using technologies that we haven't even dreamed of, may use an engine that could sustain a constant acceleration of 1 g until the ship reaches relativistic speeds. With such an engine, a trip even to Andromeda may be possible within a human lifetime. "Einstein For Dummies", By Dr. Carlos I. Calle, PhD, NASA senior research scientist Pub. Date: June 2005, ISBN: 978-0-7645-8348-3, Pages: 384 Pages.

Several possible trips on a ship constantly accelerating at 1 g. The figure for "Distance in Light-Years" is also the time that would pass on Earth while the ship traveled to its destination.

Also has a webpage discussing Mars colony.

http://nlspropulsion.net/

Re:Near Light Speed Propulsion Engine Unveiled

[fedrive]

Forgot to mention there are no gas stations out in space and the Ion Engine just like an automobile needs
refilling.

Poor concept that I think will hurt man's exploration into space.

That's old school.

[Anonymous Coward]

Yah, back in the day (when I was also a rocket scientist) it was all about the impulse, with the caveat that the materials that gave you the very best Isp were so excessively toxic (beryllium and aluminum gasses, for example) that you couldn't really use 'em in atmosphere. Unless it was pouring rain I guess.

But we're talking electric drives here, so just like with the toxicity issues mentioned above there are additional considerations beyond specific impulse.

Puns...

[clbyjack81]

Two atoms were walking down the street and one says to the other, "hey, I think I lost an electron." The other says, "are you sure?" The first one replied, "yeah, I'm positive."

As a chemist, this is my favorite corny science joke! Thanks for the smile...

Mach 1 in space...

[clbyjack81]

...this would mean that a 5000 KG spaceship would be travelling at 320 m/s, which is 1152 KM/h, which is just under Mach 1.

A minor point, to be sure, but mach numbers relate speed with the speed of sound in the same medium. Since sound does not travel in a vacuum, using mach as a unit of speed in space is meaningless.

Cheers!

Deflector...

[clbyjack81]

It seems to me that the faster a spacecraft travels, the more damage is done when a random chunk of whatever collides with the spacecraft.

That is what the 'deflector dish' is for. Now, if only we could stop burning it out when using it for other random purposes, such as an ill-fated weapon against Borg cubes...

Cheers!

Three years later...

[Anonymous Coward]

I have to post this AC because this is such a strange question, but:

Almost 3 years ago, you made this prediction.

Given the stock's performance since then, would you say you were mistaken?

Actually, it's not THAT weird, i just randomly ran across that thread during a search, and decided to see how that prophecy had turned out. Since you're still around /. I thought I'd ask you.

Re:Three years later...

[zippthorne]

Well if you check the PE, it's now down around 40, so I think you could make the argument that it has been growing it's way out of its bubble.

You could make that argument, but I fully expected a burst, so, I guess I was mistaken.

Wish you hadn't posted AC, though, because now you won't get notified of my reply.

Re:Three years later...

[Anonymous Coward]

I'm a different AC... don't worry, lots of AC posters bookmark their postings when they hope for replies.

And, lots of people read AC/non-AC exchanges, too.

Some even contribute useful things. This is not really an example.

Re:No no no. Faraday effect!

[Anonymous Coward]

Huh. The only reason electrical phenoms create
mechanical forces is because they accelerate
charged particles or magnetized ones.