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."
(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?
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.)
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.
by Anonymous Coward
on Monday October 19, @09:29AM (#29793897)
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.
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. (...) A whole bunch of countries (were involved), but Canada has one of the main pieces of hardware.
Yeaaaaaaaaaaaaaaaaaahhhhhhh!
C'mon you Americans, it's not like you don't defend your national pride in space either!:-)
by Anonymous Coward
on Monday October 19, @09:53AM (#29794267)
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 !
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.
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.
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 [nextbigfuture.com]. 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 [slashdot.org] 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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.)
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.
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 [wikipedia.org] satellites used true nuclear reactors.
by Anonymous Coward
on Monday October 19, @09:36AM (#29794011)
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.
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?
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.
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
Billions and billions... (Score:5, Funny)
Re:Billions and billions... (Score:4, Funny)
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?
Parent
Sound (Score:5, Funny)
Sorry. Star Wars geek moment...
Re:Sound (Score:5, Interesting)
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
Parent
Re:Sound (Score:4, Funny)
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.
Parent
Re: (Score:3, Funny)
Please, please, PLEASE... (Score:5, Funny)
Actually... (Score:5, Informative)
It already is. [wikipedia.org]
Parent
Re: (Score:3, Interesting)
All rockets are "impulse engines".
Needs serious power input for fast travel (Score:5, Interesting)
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.
CANADA ROCKS!!!! Woooh (Score:5, Funny)
(...)
A whole bunch of countries (were involved), but Canada has one of the main pieces of hardware.
Yeaaaaaaaaaaaaaaaaaahhhhhhh!
C'mon you Americans, it's not like you don't defend your national pride in space either!
Re: (Score:3, Funny)
Re:CANADA ROCKS!!!! Woooh (Score:5, Funny)
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.
Parent
Re: (Score:3, Funny)
About as many as don't have heath care coverage.
made in Webster, TX (Score:3, Funny)
Hooray! Now maybe Webster, TX will be know for something other than being a speed trap between NASA and I-45.
4 out of 5 astronauts surveyed (Score:5, Funny)
Newsflash (Score:3, Insightful)
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? [wikipedia.org]
Oy... (Score:4, Funny)
Re:Tag as SLASHVERTISEMENT (Score:5, Funny)
Parent
Re:Tag as SLASHVERTISEMENT (Score:5, Funny)
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 !
Parent
Re: (Score:3, Funny)
Pass..I hear it won't run Hulu in full Screen..
Re:Tag as SLASHVERTISEMENT (Score:5, Interesting)
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.
Parent
Re: (Score:3, Funny)
And in 12 months time, Richard Branson will probably have one.
Re: (Score:3, Insightful)
At some point, continuing to beat the gong on som
Re:Tag as SLASHVERTISEMENT (Score:5, Informative)
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 [nextbigfuture.com]. 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 [slashdot.org] 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.
Parent
Re:Tag as SLASHVERTISEMENT (Score:4, Interesting)
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.
Parent
Re:Tag as SLASHVERTISEMENT (Score:5, Interesting)
If something goes wrong on the surface, help is 39 days away, instead of 6 months.
Parent
Re: (Score:3, Insightful)
And yes, 'easy' in this case is still ridiculously hard...but still it's a good bit better than 2 years.
Re:I'm dizzy. (Score:5, Informative)
Parent
Re: (Score:3, Funny)
It's called acceleration. Duh...
Re: (Score:3, Funny)
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
Re:I'm dizzy. (Score:5, Funny)
You could have travelled those 800 miles in 4 hours with a VASMIR Ion Drive.
Parent
Re:I'm dizzy. (Score:5, Informative)
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.
Parent
Re:I'm dizzy. (Score:4, Funny)
Parent
Re:No quite yet. (Score:5, Insightful)
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
Parent
Re:No quite yet. (Score:5, Insightful)
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.
Parent
Re:No quite yet. (Score:5, Interesting)
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.
Parent
Re:No quite yet. (Score:4, Interesting)
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.
Parent
Re:No quite yet. (Score:4, Insightful)
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.
Parent
Re:No quite yet. (Score:5, Funny)
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.
Parent
Re:No quite yet. (Score:5, Informative)
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.
Parent
Re:No quite yet. (Score:4, Interesting)
Parent
Re:No quite yet. (Score:5, Informative)
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.
Parent
Re:No quite yet. (Score:4, Interesting)
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 [wikipedia.org] satellites used true nuclear reactors.
Parent
Re:No quite yet. (Score:4, Informative)
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.
Parent
Re:Can it be used for ISStation keeping? (Score:4, Interesting)
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.
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Re:"A new NASA rocket engine" (Score:5, Informative)
This started as a NASA project, at the Advanced Space Propulsion Laboratory [nasa.gov] 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 [adastrarocket.com]
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Re:Can this be the primary engine of a space shutt (Score:4, Informative)
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.
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Re: (Score:3, Insightful)
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
Re:Primary power source? (Score:4, Informative)
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