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NASA Space Science

NASA's Ion Thruster Sets Continuous Operation Record 165

Posted by Soulskill
from the burnin-out-its-fuse-up-there-alone dept.
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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NASA's Ion Thruster Sets Continuous Operation Record

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  • by MyLongNickName (822545) on Friday December 28, 2012 @10:16AM (#42410647) Journal

    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:Ion thrusters (Score:4, Informative)

    by flyingfsck (986395) on Friday December 28, 2012 @10:17AM (#42410653)
    Ion thrusters are in wide use on satellites for many years already. This is merely an improved version.
  • Re:Ion thrusters (Score:5, Informative)

    by Lincolnshire Poacher (1205798) on Friday December 28, 2012 @10:22AM (#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.
     

  • by Anonymous Coward on Friday December 28, 2012 @10:33AM (#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)

  • by necro81 (917438) on Friday December 28, 2012 @10:46AM (#42410791) Journal
    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.
  • by O('_')O_Bush (1162487) on Friday December 28, 2012 @10:48AM (#42410805)
    More importantly, some Xenon isotopes are common byproducts of our current fission reactors.
  • by compro01 (777531) on Friday December 28, 2012 @10:54AM (#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:Cool... (Score:5, Informative)

    by bzipitidoo (647217) <bzipitidoo@yahoo.com> on Friday December 28, 2012 @11:01AM (#42410895) Journal

    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.

  • by davydagger (2566757) on Friday December 28, 2012 @11:03AM (#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
  • by Anonymous Coward on Friday December 28, 2012 @11:20AM (#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:Cool... (Score:4, Informative)

    by NatasRevol (731260) on Friday December 28, 2012 @11:25AM (#42411021) Journal

    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]

  • by belthize (990217) on Friday December 28, 2012 @12:02PM (#42411215)

    They are used on satellites. http://en.wikipedia.org/wiki/Ion_thruster#Operational_missions [wikipedia.org]

  • Re:Xenon? (Score:5, Informative)

    by burisch_research (1095299) on Friday December 28, 2012 @12:43PM (#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? (Score:5, Informative)

    by jo_ham (604554) <joham999NO@SPAMgmail.com> on Friday December 28, 2012 @12:50PM (#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.

  • by HiThere (15173) <charleshixsn@ear ... t ['hli' in gap]> on Friday December 28, 2012 @03:16PM (#42412719)

    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.

  • by Immerman (2627577) on Friday December 28, 2012 @03:35PM (#42412891)

    Umm, no. Maximum energy gain for a gravitational assist is a slingshot maneuver where you narrowly miss a head on collision with the planet, you will then be whipped around on a parabolic path and depart in the opposite direction with twice the planet's velocity added to your own. The "gravitational tugboat" maneuver you describe is great for minor boosts and course corrections, but is unlikely to be used for speed unless a slingshot maneuver is incompatible with reaching the desired destination.
    http://en.wikipedia.org/wiki/Gravity_assist [wikipedia.org]

    As for a solar slingshot, yeah it's pretty pointless for in-system travel - it's hard to get close (not to mention survive the passing), and since it's basically the "stationary point" for the solar system you can't steal much speed from it, so once you reach your starting distance you'll have roughly* the same velocity as when you started with. Unless you just want to briefly go really fast for some reason, or are on an interstellar vessel seeking a gravity assist on your way to somewhere else in the galaxy, the sun is pretty useless for gravity boosts.

    * You won't leave a solar slingshot with exactly the same velocity because the sun itself is orbiting the solar-system's barycenter, typically between about 1/2 and 1 solar-diameter from the sun's center and constantly moving as the orbiting of the outer planets shift the system's center of mass. So there will be some velocity transfer, just not enough to be actually useful.

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