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## VASIMR Ion Engine Could Cut Mars Trip To 39 Days356

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."
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## VASIMR Ion Engine Could Cut Mars Trip To 39 Days

• #### Billions and billions... (Score:5, Funny)

on Monday October 19, 2009 @10:14AM (#29793697)
A few hundred Newtons here, a few hundred Newtons there, and pretty soon you're talking about some real delta-v!
• #### Re:Billions and billions... (Score:4, Funny)

<davidsouther@gmail.com> on Monday October 19, 2009 @11:49PM (#29803907) Homepage

Let's run the math:

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

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

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

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

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

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

• #### No quite yet. (Score:2, Informative)

by Anonymous Coward

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

• #### Re:No quite yet. (Score:5, Insightful)

on Monday October 19, 2009 @10:34AM (#29793971)

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

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

- doug

• #### Re:No quite yet. (Score:5, Insightful)

on Monday October 19, 2009 @11:18AM (#29794609) Journal

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

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

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

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

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

• #### Re:No quite yet. (Score:5, Interesting)

on Monday October 19, 2009 @11:46AM (#29794949)

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

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

• #### Re:No quite yet. (Score:4, Interesting)

on Monday October 19, 2009 @11:51AM (#29795009)

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

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

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

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

• #### Re:No quite yet. (Score:4, Insightful)

on Monday October 19, 2009 @11:58AM (#29795093) Journal

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

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

• #### Re: (Score:3, Interesting)

Actually, conventional rockets are not limited by the rate of reaction. Momentum is limited by the density of the gas and the cross sectional area at the throat of the nozzle where the flow hits the sonic condition. You could speed up the reaction a million times and increase the pressure in the reaction chamber as much as you wanted, but the flow will absolutely not go any faster than Mach 1 at the throat, period. ...Just saying. And yes, I am a rocket scientist.
• #### Sound (Score:5, Funny)

on Monday October 19, 2009 @10:20AM (#29793783)
But does this process create feedback over communications systems to create cool sound effects as the ship whooshes by?

Sorry. Star Wars geek moment...
• #### Re: (Score:2)

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

• #### Re:Sound (Score:4, Funny)

on Monday October 19, 2009 @11:29AM (#29794727)

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

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

• #### Re: (Score:2)

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

• #### Re:Sound (Score:5, Interesting)

on Monday October 19, 2009 @11:00AM (#29794373)

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

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

-Isaac

• #### Re: (Score:2, Interesting)

I've always assumed the whoosh was synthesized by the ships systems as a audio representation of the local battlespace
• #### Re: (Score:3, Funny)

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

on Monday October 19, 2009 @10:25AM (#29793839)
Let the common name be "impulse engines".
• #### Actually... (Score:5, Informative)

on Monday October 19, 2009 @10:31AM (#29793937) Journal

• #### Re: (Score:3, Interesting)

All rockets are "impulse engines".

• #### Exactly wrong! (Score:2)

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

Having an efficient engine is great (when it gets here), but having 10-fold better efficiency mean you need ONLY 1/10 the amount of propellant. Propellant to accelerate you "halfway", propellant to decelerate you halfway... OK, then more propellant to accelerate you back home, then more to decelerate you as you approach earth.
• #### Re: (Score:2)

Impulse engines have fusion reactors at their core, or so I read. While VASIMR borrows technology from fusion research, You'd need to change the fuel used, change the shape of the magnetic confinement, and increase the energy input of a VASIMR engine many orders of magnitude, in order to reach that point. So, a totally new design...
• #### Can it be used for ISStation keeping? (Score:2)

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

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

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

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

*application of Niven's law: is there any way to make it into a beamed energy weapon against "soft

• #### Re:Can it be used for ISStation keeping? (Score:4, Interesting)

by Anonymous Coward on Monday October 19, 2009 @10:36AM (#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.

• #### Re: (Score:2)

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

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

• #### Needs serious power input for fast travel (Score:5, Interesting)

by Anonymous Coward on Monday October 19, 2009 @10:29AM (#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.

• #### Not in space (Score:2, Informative)

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

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

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

• #### Re: (Score:2)

The problem is getting the reactor into orbit in the first place. If you have a Challenger-style problem with the launch, then you can end up distributing fissile materials over a rather large area. Once the reactor is in orbit, no one cares.
• #### Re: (Score:2)

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

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

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

• #### Re: (Score:3, Informative)

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

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

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

• #### How did you get modded up? (Score:3, Interesting)

First, it is easy to send up lots of uranium into space. It can be sent in capsules that can take any issue (heat, water, etc). BUT, the simple fact is, that the moon has been found to contain Uranium. And it appears to be a LOT. It should be possible to mine it and send it various places. While I was actually a fan of Mars first, now I back the moon due to the water and uranium. Combine that with an electric launcher and it should be possible to send missions at extremely fast rates through the solar syst
• #### CANADA ROCKS!!!! Woooh (Score:5, Funny)

on Monday October 19, 2009 @10:29AM (#29793901)
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! :-)
• #### Re: (Score:3, Funny)

Oh good point ... so is it 39 days or, ahem, 39 Canadian days ...
• #### Re:CANADA ROCKS!!!! Woooh (Score:5, Funny)

on Monday October 19, 2009 @11:12AM (#29794527)

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.

• #### Re: (Score:3, Funny)

I dunno.

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

I know I do.

• #### Can this be the primary engine of a space shuttle? (Score:2)

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

• #### Re:Can this be the primary engine of a space shutt (Score:4, Informative)

on Monday October 19, 2009 @10:53AM (#29794261)
The vasimr can operate in a high thrust mode. It's got an operating method that acts a bit like an afterburner, if you're willing to lower your efficiency.

It can't manage a positive thrust to weight ratio in any mode, and in any case can only operate in a vacuum, so it would end up being launched from ground on top of a chemical rocket. In theory once in space you shouldn't need other types of engine.
• #### Re: (Score:3, Insightful)

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
• #### Primary power source? (Score:2, Interesting)

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

• #### Re: (Score:2)

You hit on exactly the problem people don't discuss with ion engines. They require a source of electric power. The Deep Space 1 probe used solar panels, but it only has 2.5 kW of electrical power available. Large engines would take hundreds of kilowatts, more than any solar array could provide and be of a practical size. Maybe a nuclear fisson power supply? But that would add a huge amount of mass and volume to the spacecraft. Not to mention how up in arms some people get when you talk about launching nucl
• #### Re: (Score:2)

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

• #### Re: (Score:2)

No, you cannot.

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

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

• #### Re:Primary power source? (Score:4, Informative)

on Monday October 19, 2009 @11:03AM (#29794383)
They usually discuss using it with solar arrays for near Earth use and with nuclear reactors on the order of 10-100MW for Mars and outer solar system.
• #### made in Webster, TX (Score:3, Funny)

on Monday October 19, 2009 @10:36AM (#29794015)

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

• #### Re: (Score:2)

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

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

• #### Re: (Score:2)

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

• #### Old news (Score:2, Funny)

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

• #### 4 out of 5 astronauts surveyed (Score:5, Funny)

on Monday October 19, 2009 @11:04AM (#29794405)
preferred 39 days of abstinence to 6 months!
• #### Re: (Score:2)

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

• #### Re: (Score:2)

>> preferred 39 days of abstinence to 6 months!

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

• #### Newsflash (Score:3, Insightful)

on Monday October 19, 2009 @11:38AM (#29794855)

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]

• #### Light speed probes (Score:3, Interesting)

on Monday October 19, 2009 @11:57AM (#29795079)
I'd like to see a test probe fly just as fast as we can get it to go. I'm sure it'll be pulverized by dust motes if you can get it moving fast enough, but it would be cool to see something we've created jetting about a some considerable fraction of light speed. Maybe you can get to another star system in a human lifetime?
• #### Oy... (Score:4, Funny)

on Monday October 19, 2009 @12:33PM (#29795661)
VASIMR.

...what.

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