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NASA's Ion Thruster Sets Continuous Operation Record

Soulskill posted about 2 years ago | from the burnin-out-its-fuse-up-there-alone dept.

NASA 165

cylonlover writes "NASA's Evolutionary Xenon Thruster (NEXT) ion engine has set a new world record by clocking 43,000 hours of continuous operation at NASA's Glenn Research Center's Electric Propulsion Laboratory. The seven-kilowatt thruster is intended to propel future NASA deep space probes on missions where chemical rockets aren't a practical option. The NEXT is one of NASA's latest generation of engines. With a power output of seven kilowatts, it's over twice as powerful as the ones used aboard the unmanned Dawn space probe, yet it is simpler in design, lighter and more efficient, and is also designed for very high endurance. Its current record of 43,000 hours is the equivalent of nearly five years of continuous operation while consuming only 770 kg (1697.5 lbs) of xenon propellant. The NEXT engine (PDF) would provide 30 million newton-seconds of total impulse to a spacecraft. What this means in simple terms is that the NEXT engine can make a spacecraft go (eventually) very far and very fast."

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If I am doing the math right (4, Interesting)

MyLongNickName (822545) | about 2 years ago | (#42410597)

This ion thruster placed on Voyager 1 would have taken it up to 37 km/s over 5 years compared to the 17km/s it is going now. Not part of my calculations is that Voyager 1 would have been slightly lighter due to the reduced fuel load. i don't have exact enough numbers to do the calc, but it would have likely been in the low 40's km/s.

Re:If I am doing the math right (4, Informative)

MyLongNickName (822545) | about 2 years ago | (#42410647)

Just realized how careless I was. My calcs assume acceleration from propulsion only. Voyager 1 took up much less fuel but is going at a pretty good clip due to gravitational assists. So the comparison is not apples-to-apples. Voyager 1 has used about 80 kg of mass to get to its current speed, but a good part of that was due to energy from being placed in orbit and from a slingshot around Jupiter.

Re:If I am doing the math right (2)

necro81 (917438) | about 2 years ago | (#42410659)

Also not included in your calcs is the velocity "lost" due to escaping from the sun's gravity well. Still, it's a hell of a lot faster.

Only problem is coming up with a multi-kilowatt electrical source that far out in space. Voyager's RTGs were only a few hundred watts, I believe.

Re:If I am doing the math right (4, Interesting)

Rich0 (548339) | about 2 years ago | (#42410927)

Agreed. You can get a lot of energy from solar in the inner solar system, but ion engines are about long durations, and you're not going to be spending that much time in the inner solar system. I guess you could launch it towards the sun and do a slingshot around it. That will let you pick up a lot more velocity due to spending more time where your panels are effective, but it obviously adds a lot more distance to your trip as well.

You could just use a much larger RTG, or perhaps even a reactor. Not sure how that works out in terms of mass trade-off vs just using a conventional rocket.

Re:If I am doing the math right (4, Informative)

Anonymous Coward | about 2 years ago | (#42410995)

You would think that launching towards the sun would help; so did I. After hours of playing Kerbal Space Program, I've learned that in order to even get to the sun, you have to negate then Earth's velocity in order to fall close enough to the sun to get a boost, and you'd have to get pretty close to get a boost. Not sure if the time and energy expended doing a sun flyby (not to mention having to add extra solar shielding) would provide enough of an advantage for extra-solar trips.

Even gravitational boosts from other planets are tricky. You have to make sure you're coming from behind in order to get a boost since it allows you to fall into the planet while it's still traveling away from you, giving you more speed longer. If you intercept in front of it, the planet basically stops you in your tracks and pulls your towards itself, killing your momentum.

Re:If I am doing the math right (1, Interesting)

Impy the Impiuos Imp (442658) | about 2 years ago | (#42411297)

> I guess you could launch it towards the sun and do a slingshot around it.

No, too much energy! That will make it go faster than is possible in normal space, i.e. faster than the speed of light, and thus throw it back in time.

Previous to this discovery, only the mysterious energies released in a warp core cold start implosion could make you go faster than light while still in normal space.

Re:If I am doing the math right (1)

OakDragon (885217) | about 2 years ago | (#42411695)

Sorry, I'm replying to negate my accidental Overrated mod... meant to be : Funny+1 :)

Re:If I am doing the math right (1)

Impy the Impiuos Imp (442658) | about 2 years ago | (#42411761)

Thanks! I was wondering what kinds of asses mod down humor. -1 lame, maybe, but on principle? =D

Re:If I am doing the math right (1)

CapOblivious2010 (1731402) | about 2 years ago | (#42411701)

You'd get solar energy by going close to the sun, but no "slingshot" - the slingshot trick relies on the fact that the planets are moving in their orbits. In fact the technique slightly reduces the planet's orbital velocity - the energy has to come from somewhere! But because the sun is stationary (with respect to the solar system, of course) there's no advantage to be gained.

Re:If I am doing the math right (1)

John Hasler (414242) | about 2 years ago | (#42412063)

Only problem is coming up with a multi-kilowatt electrical source that far out in space.

Purely a political problem. Suitable and inexpensive reactor designs have existed for decades.

Re:If I am doing the math right (1)

K. S. Kyosuke (729550) | about 2 years ago | (#42412187)

Also not included in your calcs is the velocity "lost" due to escaping from the sun's gravity well.

The funny thing is that higher initial speed (or, more on the note of continuous acceleration, comparatively short acceleration deep inside the gravity well) actually diminishes the effects of the speed loss. Do the math yourself. If you accelerate to the local parabolic speed, your speed in the infinity is going to be zero. If you accelerate to local parabolic speed plus, say, 3 km/s, your speed in the infinity is going to be significantly higher than those 3 km/s. You don't even need to integrate anything, it's a simple matter of total (potential + kinetic) mechanical energy preservation, and as you surely recall, there is a squaring in the 1/2*v^2*m term.

Re:If I am doing the math right (0)

Anonymous Coward | about 2 years ago | (#42410743)

Sweet, that's 0.000133 the speed the light! If we strap 100 of these together (assuming good scaling) we can finallly achieve 1% of c -- which, is not supposed to occur ... darn... where is that nifty reference that predicts when humanity will achieve such goals?

Re:If I am doing the math right (1)

Bengie (1121981) | about 2 years ago | (#42411573)

I am curious as to why we're not supposed to achieve 1% of c. I thought the whole purpose of using an ion-thruster was to potentially achieve relativistic speeds, which you can't do with chemical rockets.

Mind my laymen's explanation, which could be completely wrong. My understanding was that chemical rockets have a maxed velocity because the energy departed from burning fuel is based on the the relatively slow speed that the matter leaves the rocket based on the temperature of exhaust. Ion-thrusters shoot ionic matter out the back-end at much higher speeds, much like a particle accelerator, but slightly lower power right now.

Re:If I am doing the math right (2)

Guspaz (556486) | about 2 years ago | (#42411951)

The exhaust velocity on an ion thruster is nowhere near that of a partical accelerator. According to a 1996 NASA document I found, the exhaust velocity of an ion thruster is 31.5 kilometers per second, while particle accelerators are very close to the speed of light. The speed record is 0.999999999976c, which is roughly ten thousand times faster than the ion thruster exhaust velocity. That's not to say that thruster exhaust velocity is the speed limit, since the thruster exhaust velocity is relative to the thruster, not the third party observer measuring the speed of the spacecraft.

At some point, though, you're going to be getting hit pretty hard by interstellar particles. Even in diffuse regions, you get a particle density of 10^-4 particles per cubic centimeter, so if we assume a spacecraft with a surface area of 10,000 square centimeters (one square meter) traveling at 3000 kilometers per second, you're going to be hit by (if my math holds up), 300 million particles per second travelling at a rather high speed, although that's not actually that much energy. I don't know enough to say if that would cause a problem.

Given that we aren't actually simpletons... (0)

Anonymous Coward | about 2 years ago | (#42410601)

... it might have been nice to know how far and how fast.

Re:Given that we aren't actually simpletons... (1)

MyLongNickName (822545) | about 2 years ago | (#42410623)

Most likely this thing was not aboard any ship or probe or any other object in outer space. This thing is being developed, so it is likely attached to some instruments in a lab where they can monitor it continually and make sure there aren't any problems. Likely they shut it down periodically to look for any problems, signs of breakdown or other signs that this cannot be scaled up for any reason.

So how far and how fast are irrelevant. There are enough numbers in the summary that you can do your own calculation on any object you like.

Re:Given that we aren't actually simpletons... (5, Insightful)

Anonymous Coward | about 2 years ago | (#42410935)

Likely they shut it down periodically to look for any problems, signs of breakdown or other signs that this cannot be scaled up for any reason.

.

Not. It was 43,000 hours of continuous operation.

Re:Given that we aren't actually simpletons... (2)

Desler (1608317) | about 2 years ago | (#42411245)

If they shut them down how could it be claimed to be continuous operation? You do know that continuous means "uninterrupted", right?

Re:Given that we aren't actually simpletons... (4, Funny)

Aaden42 (198257) | about 2 years ago | (#42411279)

Maybe they mean "continuous" operation the way ISP's mean "unlimited" bandwidth?

Re:Given that we aren't actually simpletons... (0)

Anonymous Coward | about 2 years ago | (#42411405)

Except that the unlimited never meant "unlimited bandwidth". That issomething invented by idiots. The term has always meant unlimited connection time. It was to differentiate from earlier dialup times where your billing plan usually cost per minute of service or had hard limits to how much uptime alloted to you vefore overage charges.

Re:Given that we aren't actually simpletons... (0)

Anonymous Coward | about 2 years ago | (#42411399)

Good job repeating what the guy above you said an hour ago. Mod parent down, "redundant"

Re:Given that we aren't actually simpletons... (1)

Desler (1608317) | about 2 years ago | (#42411447)

Repeat:

"To utter in dulication of another's utterance".

Which my post wasn't. Fail.

Re:Given that we aren't actually simpletons... (0)

Anonymous Coward | about 2 years ago | (#42411641)

Yes it was. I pointed out that the OP missed the "continuous" in the title. You did the same thing. Quit being stupid.

Re:Given that we aren't actually simpletons... (0)

Anonymous Coward | about 2 years ago | (#42410667)

Apparently you are.

Re:Given that we aren't actually simpletons... (5, Funny)

craznar (710808) | about 2 years ago | (#42410689)

My calculations would say it probably went at a speed of around 0km/second, placing it now around 0km from Earth after 5 years.

Re:Given that we aren't actually simpletons... (4, Funny)

avgjoe62 (558860) | about 2 years ago | (#42410725)

Check your maths. My calculations place it about .001 km from Earth...

Re:Given that we aren't actually simpletons... (1)

JWSmythe (446288) | about 2 years ago | (#42411661)

    My maths are 0.00074295 km from the Earth. :)

Re:Given that we aren't actually simpletons... (1)

Anonymous Coward | about 2 years ago | (#42411691)

Tse.Tse. It's underground, you both got the sign wrong.

Ion thrusters (3, Interesting)

P-niiice (1703362) | about 2 years ago | (#42410607)

The simple concept that we now have "Ion Thrusters" is extremely cool to me. Only "Warp Drive" would be cooler, be we have a ways to go there.

Re:Ion thrusters (3, Informative)

flyingfsck (986395) | about 2 years ago | (#42410653)

Ion thrusters are in wide use on satellites for many years already. This is merely an improved version.

Re:Ion thrusters (4, Informative)

Lincolnshire Poacher (1205798) | about 2 years ago | (#42410677)

The simple concept that we now have "Ion Thrusters" is extremely cool to me.

OK, brace yourself for techno-orgasm.

The first recorded successful firing of ion thrusters in space was onboard the Soviet Zond 2 probe. 8th December 1965.

Yes, fifty years ago.

That particular installation was experimental, but ion engines were widely used in subsequent Soviet probes. Mainly developed at the Kurchatov Institute.
 

Re:Ion thrusters (1)

renoX (11677) | about 2 years ago | (#42410809)

> The first recorded successful firing of ion thrusters in space was onboard the Soviet Zond 2 probe. 8th December 1965.

Thanks for the information, I knew that it was Russians who worked first in this field, but I didn't know that this was *that* early.
As there was discussion about Voyager 1, it's interesting to remind ourself that it was launched in 1977..

Re:Ion thrusters (4, Funny)

ArsonSmith (13997) | about 2 years ago | (#42411229)

And first put on a small one man fighter called the Twin Ion Engine fighter in 1977.

Re:Ion thrusters (4, Funny)

Rob the Bold (788862) | about 2 years ago | (#42411681)

And first put on a small one man fighter called the Twin Ion Engine fighter in 1977.

But it was short range only, and couldn't operate far from base.

Re:Ion thrusters (0)

Anonymous Coward | about 2 years ago | (#42412251)

or moon.. wait, that's no moon....

Re:Ion thrusters (1)

Narishma (822073) | about 2 years ago | (#42410711)

Only "Now"? They've been in use for decades in various probes and satellites...

Re:Ion thrusters (0)

Anonymous Coward | about 2 years ago | (#42411043)

The simple concept that we now have "Ion Thrusters" is extremely cool to me.

Why? Because it sounds cool, huh. Do you even know how they work? Do you know what an Ion is? Are you just impressed because of that one Star Trek episode where they say the aliens have an "Ion Drive" which is centuries ahead of Star Fleet? Hint: That was just technobabble. In reality these engines are just repelling charged particles of gas. You can get your own Ion Generator for less than $100 on Ebay. Search: "Air Purifier".

Re:Ion thrusters (0)

Anonymous Coward | about 2 years ago | (#42411411)

I thought it was cool because Star Wars has TIE Fighters. Of course as a kid I thought it was named that way because it looked like a bow tie and not Twin Ion Engine Fighter.

Re: Ion thrusters (0)

Anonymous Coward | about 2 years ago | (#42412355)

Wow way to be a pompous Debbie Downer. Do you feel better about yourself now that you've demeaned someone else?

Re:Ion thrusters (1)

Anonymous Coward | about 2 years ago | (#42411369)

It's going to be a while on "Warp Drive". They're working on a detection device [nasa.gov] for the required field now. It's called the "White-Juday Warp Field Interferometer". I don't think anyone has a clue as to how to alter space, but at least they will be able to detect any changes. Let the testing commence!

Unit conv. (-1)

Anonymous Coward | about 2 years ago | (#42410609)

One point twenty-one jiggawatts?

Re:Unit conv. (-1)

Anonymous Coward | about 2 years ago | (#42410969)

No, but enough to get jiggy with it.

Um, they used what? (1)

Anonymous Coward | about 2 years ago | (#42410627)

while consuming only 770 kg (1697.5 lbs) of xenon propellant.

Last I heard, xenon was a gas, and that sure sounds like an awful lot of it - how much is left (on our planet)?

Re:Um, they used what? (1)

dr.Flake (601029) | about 2 years ago | (#42410657)

My first thought as well.

Wikipedia's first hit:

"Extraction of a liter of xenon from the atmosphere requires 220 watt-hours of energy.[52] Worldwide production of xenon in 1998 was estimated at 5,000–7,000 m3"

Sounds like we have some scaling issues before this engine puts us on mars on a regular basis.

Re:Um, they used what? (1)

19thNervousBreakdown (768619) | about 2 years ago | (#42410807)

What I don't understand is why you would measure "production" of a gas as a unit of volume. And if you're going to do that, why wouldn't you include the pressure as well? Doesn't this tell us basically nothing, or is there some sort of standard I don't know about?

Re:Um, they used what? (3, Informative)

compro01 (777531) | about 2 years ago | (#42410843)

is there some sort of standard I don't know about?

Yes. Standard temperature and pressure [wikipedia.org] .

the IUPAC's definition is a temperature of 273.15 Kelvin (0 C) and a pressure of 100 kilopascals, though there's a bunch of other standards to choose from.

Re:Um, they used what? (2)

jo_ham (604554) | about 2 years ago | (#42411463)

If a pressure is not given, assume STP. At least, according to IUPAC. Though like many unit cock ups in the past, assumptions can get you in all sorts of trouble. however if it was given in m^3 then it's going to be reasonably safe to assume STP, then you just use the ideal gas law to work out quantity - Xenon is reasonably close to one.

Re:Um, they used what? (4, Informative)

davydagger (2566757) | about 2 years ago | (#42410909)

"220 watt-hours of energy."

Less power than running a dungeon in world of warcraft using a decent gaming rig. doubly so, if you run dual cards.

total power usage of gaming rig under load - ~400 watts

Time to run a dungeon - between 45 min - 1 1/12 hours.

300 - 600 watt hours

Re:Um, they used what? (1)

JoeSchmoe999 (782579) | about 2 years ago | (#42410687)

Approximately 1/2 trillion kilograms give or take

Re:Um, they used what? (0)

Anonymous Coward | about 2 years ago | (#42410695)

Wolfram alpha says that the "volume of 770kg of xenon" is 131,000 liters (34,500 gallons). Unfortunately it doesn't know the answer to "volume xenon on earth"...

I'm not entirely sure the 34,500 gallon answer is right either (i didn't spend the time to re-verify by pV = nRT -- I think that's it) and I didn't immediately find at what pressure they keep this stuff at -- I was wondering about the storage-space aspect of this myself.

Re:Um, they used what? (5, Informative)

Anonymous Coward | about 2 years ago | (#42410723)

lots and lots and lots. just expensive to separate as it is widely distributed.
Xenon is a trace gas in Earth's atmosphere, occurring at 87±1 parts per billion (nL/L)

(wikipedia is fun)

being heavy it doesn't escape the atmosphere.
It is very dense as a liquid, stores compactly, and can used as a heatsink for the engine.

for fun:
770kg of xenon is 130641 L at STP
it is 252 L at xenon boiling point (as liquid)
it is also ~2% of total xenon production (in 1998)

Re:Um, they used what? (3, Informative)

necro81 (917438) | about 2 years ago | (#42410791)

Unlike helium, which is so tenuous it escapes the atmosphere, xenon is a relatively heavy gas that sticks around. It's not particularly abundant (less than 100 parts per billion in the atmosphere) but it can be pretty easily separated out. According to wikipedia's references, annual xenon production is 5000-7000 m^3 [wikipedia.org] (at STP), or about 35,000 kg. (This reference [bgcspecgas.com] estimates 9000 m^3/yr, or 53,000 kg.) So 770 kg used in one multi-year experiment isn't such a big deal. When it is used in various applications, it tends to return to the atmosphere, from whence it can be separated again.

Re:Um, they used what? (4, Informative)

O('_')O_Bush (1162487) | about 2 years ago | (#42410805)

More importantly, some Xenon isotopes are common byproducts of our current fission reactors.

Re:Um, they used what? (2)

compro01 (777531) | about 2 years ago | (#42410815)

Xenon makes up about 87 parts per billion of the Earth's atmosphere.

The dry mass of the Earth's atmosphere is approximately 5.14 quadrillion tonnes.

That comes to about 447 million tonnes of Xenon.

Xenon is also a waste product from nuclear fission.

Re:Um, they used what? (3, Interesting)

Rockoon (1252108) | about 2 years ago | (#42410837)

Last I heard, xenon was a gas, and that sure sounds like an awful lot of it - how much is left (on our planet)?

Seriously man.. 770kg shouldnt sound like "an awful lot of it" when you are asking about how much we have "on our planet." You do know how massive the atmosphere is, right?

Extracting a liter of xenon from the atmosphere requires 798000 joules of energy, and 770 kg of xenon is 131804 liters. So thats 104388768000 joules of energy.

(yes, I am shooting for "oh noes big number")

Thats equivalent to under 3 minutes of output of the typical (average American) coal plant that puts out 667MW.

Re:Um, they used what? (1)

RevDisk (740008) | about 2 years ago | (#42410881)

Xenon in atmosphere is 1 part per 11.5 million, and our atmosphere is about 5×10^18 kg. So rough guess is about 400,000,000,000 kg of xenon is left. Which is only about 240 million units of that amount of propellant. Happy news is that it's quite plentiful on Jupiter.

Re:Um, they used what? (1)

RevDisk (740008) | about 2 years ago | (#42410907)

520 million units, rather. Friggin English/metric. Sorry about that. Again, very rough estimated.

Re:Um, they used what? (0)

Anonymous Coward | about 2 years ago | (#42411063)

Shouldn't be hard to switch to something else when we ru out of Xenon.

Re:Um, they used what? (1)

Anonymous Coward | about 2 years ago | (#42411615)

And every molecule of xenon used in this experiment... went back into the atmosphere.

Re:Um, they used what? (0)

Anonymous Coward | about 2 years ago | (#42411831)

Probably was recycled.

Re:Um, they used what? (1, Interesting)

Anonymous Coward | about 2 years ago | (#42410971)

That's about a $1 Million dollars worth of Xenon. Now, if they used mono-isotopic Xenon, they could improve the efficiency probably by a factor of two, which would cut way down on launch and carrying costs. But Xe-136, if it could be gathered in that amount, would cost over a Billion.
    As long as I'm throwing millions and billions around, I should point out that the quantity of Xenon available is in the range of millions to billions of Kilograms. It's just difficult and expensive to purify. Unless we let an improperly run Nuclear Reactor make it for us. All the hot isotopes decay away rapidly, into chemically separable daughters, which leaves an enriched Xe-136 feedstock.
    (My numbers may be way off; It's been a few years since I worked in those fields. If Xenon looks expensive... I once had to guard and supervise the purification of four grams of Calcium-48. It was, theoretically at least, (We were the only people on Earth using it.), worth about $1 Million a _gram_.)

Re: Um, they used what? (1)

JoeRobe (207552) | about 2 years ago | (#42412383)

Why would isotopic purification increase the efficiency by a factor of 2?

Re:Um, they used what? (1)

50000BTU_barbecue (588132) | about 2 years ago | (#42411227)

One would assume since ion thrusters only work in a vacuum, that whatever test chamber they used to fire the engine also recuperates the xenon. One hopes. One further hopes that in reality only a small amount of xenon was continuously cycled between the test chamber and the engine.

Re:Um, they used what? (2)

jo_ham (604554) | about 2 years ago | (#42411509)

The hassle of recovery of the gas is entirely based on cost. Helium is routinely recovered and recompressed in research labs and institutions, usually centrally because of the high cost and scarcity - the helium compressor at my university consumes 0.125 MW, by far the single biggest energy sink on the campus, when a critical volume has been recollected ready for purification and reliquification. It's still cheaper doing it this way than just buying more in.

Xenon is relatively easy to extract from the air, despite its low partial pressure.

If only it could use a cheaper reaction mass (0)

Anonymous Coward | about 2 years ago | (#42410629)

xenon is a rather rare gas...

Re:If only it could use a cheaper reaction mass (-1)

Squidlips (1206004) | about 2 years ago | (#42410885)

And non-renewable. Once it is used, it is GONE forever.

Re:If only it could use a cheaper reaction mass (1)

Anonymous Coward | about 2 years ago | (#42411113)

Strictly speaking, that's not correct, because a significant amount of xenon is generated during uranium fission reactions and some of that will decay to stable Xe isotopes. I don't know if that is possible to recover in commercial quantities at a reasonable price, but there are ways to do it [acs.org] .

Re:If only it could use a cheaper reaction mass (1)

jandrese (485) | about 2 years ago | (#42411267)

Depends, if the Xenon is shot back at Earth it could re-enter the atmosphere and be ready to be extracted again.

Cool... (0)

Anonymous Coward | about 2 years ago | (#42410635)

Now we just need something 1000X faster to make interstellar (robotic) probes practical.

Re:Cool... (3, Interesting)

MyLongNickName (822545) | about 2 years ago | (#42410679)

Although acceleration is not the same as speed, AC is right. Even if you assume the probe's weight is negligible, you begin to run into issues with thrust to weight of fuel. Over the five years cited in this story, the ion thruster consisting of fuel only would get you to 75km/s, or about a 14,000 year flight to alpha centauri. Scaling up doesn't help much as the ion thruster has to accelerate a larger mass.

Re:Cool... (4, Informative)

bzipitidoo (647217) | about 2 years ago | (#42410895)

I keep hoping, but interstellar is extremely difficult. It won't happen in our lifetimes. To get to Alpha Centauri in just 70 years requires acceleration to near 0.1c. That takes way more energy than we can currently give our probes. Thinking that a gravity assist can help significantly with that is like thinking you can make your car go significantly faster by having a person stand beside the road and blow air at your back as you pass.

Maybe we could eventually swing something on the order of 700 years. But just 70 years is really pushing the longevity of our current designs. Plutonium doesn't last long enough. In any case, how to make a probe last 700 years is only half the problem. Keeping a project alive, relevant data fresh on current media, and people trained for such a length of time would be the other half. 700 years is an awful long time for circumstance to scuttle the project. Can NASA or any other agency last that long? Can the US?

Barring catastrophe, we will eventually do it.

Re:Cool... (3, Interesting)

smpoole7 (1467717) | about 2 years ago | (#42411049)

> Thinking that a gravity assist can help significantly ...

http://en.wikipedia.org/wiki/Gravity_assist [wikipedia.org]

Right. Most folks, even amateur space enthusiasts like us, don't really understand the gravity "slingshot" and how it works. Some have the idea that you can just accelerate like a demon toward a given planet or moon, whip around it and somehow gain all sorts of new velocity. That's not so.

What you will gain is part of the orbital velocity of the object that you're "slingshotting" around. Nice boost and it makes a difference -- our space probes use it all the time -- but it's not some magical means by which you can accelerate to C-fractional speeds.

Re:Cool... (4, Insightful)

Megane (129182) | about 2 years ago | (#42411243)

To get to Alpha Centauri in just 70 years requires acceleration to near 0.1c.

And then to actually stop there to land on a planet requires deceleration by nearly 0.1c.

Re:Cool... (0)

Anonymous Coward | about 2 years ago | (#42412037)

nah man, just jump out as you shoot past =D

Re:Cool... (2)

Impy the Impiuos Imp (442658) | about 2 years ago | (#42411409)

A few years of economic difficulties and some populist loudmouths talking about draconian cuts, and boom! There she goes.

Re:Cool... (3, Interesting)

MachineShedFred (621896) | about 2 years ago | (#42412233)

Trying to work a project for 700 years would also inevitably land you in the position of launching something that is 300 years newer that would pass your 300 year old probe long before it got to it's destination, because propulsion tech is 300 years better.

I mean, 700 years ago was 150 years before Copernicus created his heliocentric model of the solar system, and was lambasted for it. Now we've got probes on their way out of the solar system that he was mostly correct about.

Re:Cool... (3, Insightful)

qwak23 (1862090) | about 2 years ago | (#42412291)

The christian church (in various forms) has been around for millenia awaiting the return of their messiah. That is quite a bit of longevity. Perhaps we should convert NASA to a religion, then there will be no problem having someone wait a few hundred years for the return of their white metallic savior.

Re:Cool... (3, Interesting)

atrain728 (1835698) | about 2 years ago | (#42410937)

Doesn't sound like alot, but 75km/s would still make it the fastest man-made object in history. [wikipedia.org]

Re:Cool... (3, Informative)

NatasRevol (731260) | about 2 years ago | (#42411021)

For a more earthly comparison, it would take about 8.6 seconds to drive across Kansas at that speed.

http://en.wikipedia.org/wiki/Kansas [wikipedia.org]

Re:Cool... (5, Funny)

Anonymous Coward | about 2 years ago | (#42411055)

That's still a lot of time to spend in Kansas.

Re:Cool... (1)

NatasRevol (731260) | about 2 years ago | (#42411095)

But it's still a lot better than the 8.6 hours it takes to drive across it.

Re:Cool... (1)

ThatsNotPudding (1045640) | about 2 years ago | (#42412253)

That's still a lot of time to spend in Kansas.

Hoo, clever! What, no Wizard of Oz reference? Those are always so insightful.

Re:Cool... (1)

Impy the Impiuos Imp (442658) | about 2 years ago | (#42411425)

Bullshit!

I send photons out my flashlight way faster than that.

Turn To Slide 6 For Recent Updates (1)

bwohlgemuth (182897) | about 2 years ago | (#42410683)

The nice thing is if you want a more recent update, just start calling all of the people on Slide 6. Then again, this is a four year old presentation...some have probably moved onto other positions.

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Why no ion thrusters on satellites? (1)

storkus (179708) | about 2 years ago | (#42410949)

This is a question I've wondered for years and have never seen answered: why can't chemical thrusters used on satellites (particularly in geostationary orbit) be replaced with ion ones? It seems to me that running out of fuel is the primary method of "death" for a geostationary satellite. Do station-keeping maneuvers really require that much thrust?

Cool (0)

maroberts (15852) | about 2 years ago | (#42410953)

Imagine 2 of these engines in a single pilot machine, equipped with lasers and with a solar panel on each side for electricity generation and to shield the body from excess solar radiation. We could call it a TIE Fighter....

Re:Cool (5, Funny)

jandrese (485) | about 2 years ago | (#42411307)

The villainous Tie fighter pilot straps in, ready to squash the rebellion once and for all. He charges his heavy blasters, straps into the seat, and twists the knob for full throttle, feeling the exhilarating rush of a barely perceptible acceleration and the knowledge that in two or three years time he will be moving at a pretty good clip, just so long as he never has to change directions.

Re:Cool (0)

Anonymous Coward | about 2 years ago | (#42411413)

The only problem with this is that a dogfight above a hypothetical artificial moon would take months to conclude.

Re:Cool (1)

TFAFalcon (1839122) | about 2 years ago | (#42411499)

Nah, we'll need to give them a bit more thrust before they become useful. Considering the fighter itself has no life support, the pilot will be dead before he gets to above walking pace if we use the current model.

Xenon? (1)

slashmydots (2189826) | about 2 years ago | (#42410975)

I thought to use something as fuel in an ion thruster, it has to be able to ionize? Xenon is about as inert as it gets and really isn't useful for anything because nothing reacts with it in any way. In fact, wasn't hydrogen or something the typical fuel for an ion thruster? Can one of the hundred or so ion thruster engineers that are likely here on slashdot (lol) explain it to us?

Re:Xenon? (3, Funny)

wbr1 (2538558) | about 2 years ago | (#42411011)

I thought to use something as fuel in an ion thruster, it has to be able to ionize? Xenon is about as inert as it gets and really isn't useful for anything because nothing reacts with it in any way. In fact, wasn't hydrogen or something the typical fuel for an ion thruster? Can one of the hundred or so ion thruster engineers that are likely here on slashdot (lol) explain it to us?

http://en.wikipedia.org/wiki/Ion_thruster [wikipedia.org]
http://en.wikipedia.org/wiki/Xenon [wikipedia.org]
You figure out the rest.

Re:Xenon? (4, Informative)

burisch_research (1095299) | about 2 years ago | (#42411523)

In a chemical sense, yes Xenon is inert and doesn't like to ionize. However, in the case of an ion thruster, the ionization is accomplished using high voltages - very easy to do.

Xenon is preferred because it's non-toxic, comparatively easy to handle, and has a 'heavy' nucleus -- meaning that you can more easily give each atom more of a push, resulting in higher thrust. You could use ions of any atom you like, though. Hydrogen's got the lightest nucleus there is, so it's not much use, not to mention being a royal pain to handle.

The Russians started out with, iirc, cesium and mercury thrusters. But of course these are really nasty substances and you really don't want to be around them if you can help it.

Re:Xenon? (5, Informative)

jo_ham (604554) | about 2 years ago | (#42411561)

Xenon is easy to ionise - it's a large, diffuse atom with the outer electrons far from the nucleus. It's also inert and heavy, giving you a non-toxic, non-corrosive fuel with a high mass/charge ratio; ideal for an ion thruster.

If only it were cheaper to buy!

It's also not true that "nothing reacts with it". The lower end of group 18 does react with strong oxidisers and you can form (and isolate) crystals of XeO4 and so on. The closest to being truly "noble" gasses are helium and neon.

Re:Xenon? (1)

neurocutie (677249) | about 2 years ago | (#42411605)

Recall the existence of all those xenon arc bulbs in photo flash and strobe lights and the answer is obvious...

Re:Xenon? (1)

spectral7 (2030164) | about 2 years ago | (#42412067)

Ion thrusters don't depend on chemical reactions. Ionization is through colliding a high-energy electron with the propellant, and then the ionized propellant is accelerated.

Using hydrogen is pretty dumb because you're trying to generate thrust. F=ma. Hydrogen has low mass.

TIE (-1)

Anonymous Coward | about 2 years ago | (#42410977)

if they put twice engines will be the firts TIE, and if they put a gun too would be a real TIE Fighter

Soviet Russia (0)

Anonymous Coward | about 2 years ago | (#42411791)

In Soviet Russia ions thrust you! ooooh, wait a minute.....

Ion Thrusters (1)

Brad1138 (590148) | about 2 years ago | (#42412367)

I just like saying it, it sounds so cool. Ion Thrusters....
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