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NASA's Ion Thruster Sets Continuous Operation Record
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."
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.
See my journal for slashdot ID's by year. Mine created in 2005. http://slashdot.org/journal/289875/slashdot-ids-by-year
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.
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.
See my journal for slashdot ID's by year. Mine created in 2005. http://slashdot.org/journal/289875/slashdot-ids-by-year
My calculations would say it probably went at a speed of around 0km/second, placing it now around 0km from Earth after 5 years.
EMail: 0110001101100010010000000110001101110010 0110000101111010011011100110000101110010 0010111001100011011011110110
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)
Check your maths. My calculations place it about .001 km from Earth...
How come Slashdot never gets Slashdotted?
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 (at STP), or about 35,000 kg. (This reference 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.
More importantly, some Xenon isotopes are common byproducts of our current fission reactors.
while(1) attack(People.Sandy);
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.
upon the advice of my lawyer, i have no sig at this time
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.
"His name was James Damore."
is there some sort of standard I don't know about?
Yes. Standard temperature and pressure.
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.
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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.
Intellectual Property is a monopolistic, selfish, and defective concept. It is "tyranny over the mind of man"
"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
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.
Doesn't sound like alot, but 75km/s would still make it the fastest man-made object in history.
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
http://en.wikipedia.org/wiki/Xenon
You figure out the rest.
Silence is a state of mime.
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
There are two types of people in the world: Those who crave closure
> Thinking that a gravity assist can help significantly ...
http://en.wikipedia.org/wiki/Gravity_assist
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.
Cogito, igitur comedam pizza.
That's still a lot of time to spend in Kansas.
They are used on satellites. http://en.wikipedia.org/wiki/Ion_thruster#Operational_missions
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.
#naabhaprzrag, #sverubfr-000, #agi-fcbafberq, negvpyr[pynff*=' negvpyr-ary-'] { qvfcynl: abar !vzcbegnag; }
If they shut them down how could it be claimed to be continuous operation? You do know that continuous means "uninterrupted", right?
Maybe they mean "continuous" operation the way ISP's mean "unlimited" bandwidth?
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.
I read the internet for the articles.
A few years of economic difficulties and some populist loudmouths talking about draconian cuts, and boom! There she goes.
(-1: Post disagrees with my already-settled worldview) is not a valid mod option.
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.
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.
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.
char*f="char*f=%c%s%c;main(){printf(f,34,f,34);}";main(){printf(f,34,f,34);}
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.
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.
Slashdot still doesnâ(TM)t support Unicode after it was added to the HTML standard in 1997.
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.
For the engine they probably store it as a liquid. Significantly below the transition point. On Earth that's not much of a problem, and in space not much of one either...unless you get near the sun. 165K seems to be cool enough.
Quote from Wikipedia:
Xenon is the preferred propellant for ion propulsion of spacecraft because of its low ionization potential per atomic weight, and its ability to be stored as a liquid at near room temperature (under high pressure) yet be easily converted back into a gas to
Note, however, that ion engines can theoretically work with any atom. Personally, I think they should be designed to use some common heavy element, like iron, and to accelerate the ions maximally. This, however, is an eventual design goal, not something to aim for in the next decade or so.
I think we've pushed this "anyone can grow up to be president" thing too far.
Through hardship to the stars! (Kansas state motto)
That would be pretty pointless though - pushing directly away from the planet you're orbiting just changes your orbital eccentricity, without significantly changing your orbital energy. Meaning that when you reach the opposite side of your orbit you'll be even closer to the planet than you were before. And since you'd have to be pretty close to begin with for a significant portion of your exhaust to collide with the planet that probably means you've just executed a de-orbiting maneuver. And actually, since we're talking about a very low-thrust, very long-duration engine, what we're probably doing is just continuously cancelling out the orbital adjustment we made while on the opposite side of the planet.
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