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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."
A few hundred Newtons here, a few hundred Newtons there, and pretty soon you're talking about some real delta-v!
But does this process create feedback over communications systems to create cool sound effects as the ship whooshes by?
Sorry. Star Wars geek moment...
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.
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.
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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.
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Let the common name be "impulse engines".
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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.
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You could have travelled those 800 miles in 4 hours with a VASMIR Ion Drive.
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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
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.
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
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 !
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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.
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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.
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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.
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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.
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If something goes wrong on the surface, help is 39 days away, instead of 6 months.
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.
So if this is the future...where's my jet pack?
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.
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.
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.
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