NASA Ground Tests Ion Engine

herda05 writes "New Scientist reports from a press release by NASA on a successful ground test of the HiPEP (High Power Electric Propulsion) ion engine, which is the first 'major milestone' for Project Prometheus. Also some pictures and more info on the HiPEP engine."

Comments

Xenon gas?

[El]

The HiPEP thruster operates by ionizing xenon gas with microwaves.

Is there really a lot of xenon gas in outer space? Wouldn't ionizing hydrogent work a lot better? And, is it really a vacuum chamber if it's filled with xenon gas?

Re:Xenon gas?

[gl4ss]

they take the xenon with them.

harvesting type of engines/probes are still quite far off afaik so it hardly matters.

Re:Xenon gas?

[NanoGator]

"And, is it really a vacuum chamber if it's filled with xenon gas?"

A couple of implications can be drawn here:

- There is nothing but xenon inside the chamber.
- There isn't enough xenon in the chamber to generate significant pressure.

Re:Xenon gas?

[CXI]

The third inplication is that the chamber is a vacuum and the xenon is stored in a tank and expelled to generate thrust, as in actually the case.

Re:Xenon gas?

[deglr6328]

what is "hydrogent"? :) The reason Hydrogen is not used and Xenon IS, is because xenon is ~130 times more massive per atom than Hydrogen is. Therefore you'll get much more momentum from accelerating the Xenon out the back of an ion engine at a given speed than you will a Hydrogen atom. And for that matter why stop at Xenon? This guy is working on Bismuth powered Hall thrusters.

Re:Xenon gas?

[kinnell]

Therefore you'll get much more momentum from accelerating the Xenon out the back of an ion engine at a given speed than you will a Hydrogen atom

Close, but...

The speed isn't a constant for different gasses. What's important, as you point out is momentum.

Change of momentum = impulse = Force * time.

The advantage of heavier ions is that they accelerate slower, thus staying within the engine for longer. As a result, the force is applied to the ions for longer, therefore the change in momentum of the ions is higher, therefore, the change in momentum of the vehicle is also higher.

Re:Xenon gas?

[Muad'Dave]

Oh great! There goes the price of Pepto-Bismol. (Yes, it contains the metal Bismuth).

Now all I need...

[teridon]

is a portable 25-kilowatt reactor. Pluto here I come!

Obligatory TIE Fighter comment

[schnits0r]

I still want my TIE Fighter.

Re:Help! parsing the title!

[drakaan]

A "ground-test" is a test performed prior to putting the tested item in its normal operating environment (in this case, it's an appropriate description, since it stayed on the ground).

"NASA Ground-tested an Ion Engine" would have been a less headline-ish way of saying it.

Re:Am I interpreting this correctly?

[SmallFurryCreature]

Ion engines are very efficient with their propelant. So yes the longer you want to burn the more you need to carry but it is a fraction of what you would need to carry for a normal rocket engine. ION engines work by constantly burning of a tiny amount of fuel/propelant amazingly effciently. The accelarition is awfull but it can just keep on accelaring for years.

This I think makes it only usefull for long flights. No tie fighters. Fortuanly real space flight has a lot of long flights.

Re:Am I interpreting this correctly?

[Leroy_Brown242]

That's a good point.
Space is massivly huge. Nothing like Star Treck of Star Wars ever illustrated very well.
Years and years and years of vast nothing.

A slow burn over days or weeks would build a pretty good speed though.

Very very very low thrust

[G4from128k]

Before anyone has visions of nimble fighters, we must remember that ion engines have extremely low thrust. A quick calc based on the numbers in the article, which I hope I did correctly, suggests that the thrust is only about 0.3 Newtons (1 ounce for you Imperialists). What makes these engines exciting is that they can sustain that thrust of years. Estimated fuel consumption is only about 14 grams per hour.

Slow and steady wins the race.

Re:Very very very low thrust

[edunbar93]

Actually, what makes this new development exciting is the fact that the ion engine used on the Deep Space 1 probe produced much less than 0.3 Newtons of force... I don't recall the actual thrust, but it was roughly analagous to the amount of force a single piece of paper exerts on your hand if you were to hold it up near the earth's surface. So probably somewhere around 0.01 N. And yet, they were still able to measure the amount of acceleration due to the engine.

The real impressive engine...

[momerath2003]

One of the earlier "nuclear" test engines was this puppy, the nuclear thermal rocket. If you have seen a video of it when it was being tested, you would know that that thing is one mighty beast. The soviets also attempted to design one (both the Soviet and the American versions had the purpose of getting people to mars) which looks a lot cooler. I would love to have a model of that sitting on my desk. :)

Anyway, this nuclear propulsion is somewhat related to the newer Xenon method albeit with lower specific impulse but much higher acceleration.

And therein lies the problem

[SuperBanana]

Now all I need is a portable 25-kilowatt reactor.

Yep. And considering current "MMRG" units and SRGs(check out their homepage- they're basically two of I-dunno-how-many nuclear-powered generators NASA has at the moment) top out at 100W per module, well...

I think the problem is that NASA, rightly so, is extremely nervous about putting nuclear stuff into orbit, because of the frequency with which these things blow up. So it tends to be very simple, not very efficient(the MMRG only captures 100 out of 250w produced), and not very powerful. For example, the MMRG modules produce heat just by natural decay, and they're designed to survive a crash as a whole intact(nasa notes that previously they were designed to burn up, but are now designed to stay intact- probably because things don't always get high enough to burn up).

Problem is, even with solar power- which starts getting pretty sparse(why they came up with the nuclear power sources)- a large(sheet of plywood sized) solar panel isn't much, at least on earth(you get more power outside the earth's atmosphere). It'd take a LOT of that sized solar panels to power such an engine. Probably somewhere above 50 for starters...

Re:And therein lies the problem

[datenwolf]

I just want to remind you of the "Deep Space 1" probe, which is the very first utilizing a ion drive. The thrust isn't much, but a ion engine can run over a long period, allowing much higher "burnout" velocities, than the chemical rocket engines that are neccesary to launch a rocket.
And it has a power of only 1kW. IMHO such powerfull engines make most sense at solar swingby manouvers where you've a lot of light energy avaliable.

On earth it's the best to burn the whole fuel in a very short time(*) but in zero g this doesn't matter.

* think about, what happens, when you reduce the thrust so much, that the rocket would just levitate. You burn and burn fuel, but don't gain speed. But burning the same fuel in a short time gives you a lot of speed.

Re:And therein lies the problem

[confused one]

Actually, it's already been (in) development. DOE's been working on it for a decade and has working prototypes.

Cool.

[falsification]

I always liked ion engines. Back in the star frontiers, when I was a ranger, my commando team would hide in a freighter's hold. Listening to that steady purr of the ion engine made the days before hitting down the warp pass quickly by. We played jimble-jack, and 3-D chess, sure, but mostly you just sat on your ass on a crate smoking sourweed. It was kind of rough, because one of my comrades was a Vrusk, and the other was a Yazirian. They didn't like one another. Plus, the male and female Dralasites kept humping. It got to smell pretty bad in that hold. Eventually, we unwarped. We sneaked up to a Sathar and pirate base. They thought we were just smugglers, but they wouldn't have, except for that ion engine. Old, but reliable. We lost a lot of men that day, dammit all. And the Vrusk. Had to mercy kill him with a laser pistol. It was worth it, though. Disabled their chemical rocket system. We killed or captured the entire lot of bad guys. There was dead worm everywhere. The vibroblade was whirring that day, I'll tell you. It was beautiful. At that point, the base was about to fall into an event horizon, but with our trusty ion engine freighter, we got out of there, right before a dual star system was sucked into the black hole, which created a supernova.

Those were the days.

Re:Am I interpreting this correctly?

[jerde]

Ion propulsion works very differently than any other type of normal rocket. The idea with ion engines is that they're able to take individual atoms of their "propellant" and accelerate them to high velocities, using electricity as the energy, rather than some sort of chemical reaction.

Rockets in space work by taking some mass and throwing it in the opposite direction you want to go. Imagine yourself floating in space holding a bowling ball. You wouldn't have to push the ball away from you very hard to get yourself moving, since it's very heavy. But what if you only had a ping-pong ball: to get yourself moving quickly, you'd have to "throw" the ping-pong ball away from you very very very fast, to make up for its very small mass.

Chemical rockets take some combination of chemicals that react strongly together, creating heat. The result is a hot gas at high pressure, which blows out in the direction of the rocket nozzle, providing thrust the other direction.

The xenon ion engine takes xenon gas at very very low pressure, ionizes the atoms so that they're electrically charged, and then uses electric force to fling them at VERY high speed out into space. The velocity is much higher than in any chemical rocket. But ion engines aren't very strong -- the process works with just a little tiny bit of xenon at a time, so the engine as a whole winds up giving just a very gentle push. But since not much xenon is used up, the xenon that you have will last a LONG time.

That's the "specific impluse": a measure of how much a rocket can push you "per pound" of fuel. This page says that the space shuttle's chemical engines have a specific impulse of 460. This latest ion engine has a specific impulse of 6000!

So with the same weight of fuel, the ion engine would get you going about 13 times faster by the time you used up the fuel.

- Peter

So.....

[FinestLittleSpace]

.... can someone actually tell me what potential application this has... i.e. how far it'll get a rocket.... will it just be a quicker trip to mars for probes or are we looking at something which could send probes out the solar system and beyond...? If so... how long will/would it take to get to amrs, and simiarly, are we anywhere near reaching the nearest star after the sun? :)

Nuclear power in space

[dido]

What they really should be doing is coupling ion engines to nuclear reactors. Then you'd have a power plant capable of producing a large quantity of energy for a long time, and keep going for many, many years.

I remember reading somewhere that nuclear-powered ships could keep going and going for 20+ years or more. The only reason why such nuclear aircraft carriers eventually must return to port is other supplies like food and water for the crew, not fuel. Same thing goes for ballistic missile submarines, which can stay submerged for years on end, using the power from the nuclear reactor to produce drinkable water and breathable air for the crew. A typical deterrence patrol for an Ohio class SSBN only lasts for two months only because that's probably how long a crew can stay cooped up in a very small space without going crazy. :)

Only thing is there are all these groups that seem to be afraid to put anything nuclear in space for some reason. If anyone's still really serious about doing manned space exploration, we'll have to do this eventually, I think. Solar just won't be able to produce the kind of power required to provide extended life support and reasonably fast travel at the same time. It's no good to be cooped up in a space capsule for eight months to get to Mars, and back again... These ion engines could probably produce a lot more thrust with the kind of juice a nuclear reactor onboard could put out, possibly even enough to accelerate the ions to relativistic velocities, and then we could have some real serious speed, to make interstellar travel, at least by machines, a realistic possibility.

As for radiation shielding, that's something you'll have to deal with anyway, nuclear reactor or not. Even a small coronal mass ejection could produce far, far more radiation than the power plant would.