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Giving CubeSats Electric Propulsion 74

Posted by timothy
from the how-repellant dept.
eldavojohn writes "Thirteen picosatellites were launched back in June of 2006 with the price coming down dramatically in the years since. But the Rubik's cube sized devices have no mobility, meaning once they're put in orbit, they stay in that orbit. The big problem is that traditional chemical propulsion systems are too large for ten-centimeter sided cubes weighing a kilogram. A new electric propulsion system designed by Paulo Lozano of MIT might change that. "
"The article explains how it works: 'Lozano's design relies on electrospraying, a physics process that uses electricity to extract positive and negative ions from a liquid salt that is created in a laboratory and serves as the system's propellant. The liquid contains no solvent, such as water, and can be charged electrically with no heat involved. Whereas other electric propulsion systems charge the ions in a chamber on the satellite, the ionic liquid in Lozano's design has already been charged on the ground, which is why his system doesn't need a chamber. Electricity is then converted from the main power source of the CubeSat, typically batteries or a solar panel, and applied to a tiny structure roughly the size of a postage stamp. This thin panel is made of about 1,000 porous metal structures that resemble needles and have several grams of the ionic liquid on them. By applying voltage to the needles, an electric field is created that extracts the ions from the liquid, accelerates them at very high speeds and forces them to fly away. This process creates an ionic force strong enough to produce thrust.'"
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Giving CubeSats Electric Propulsion

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  • by QuantumG (50515) * <qg@biodome.org> on Wednesday February 03, 2010 @07:37PM (#31016772) Homepage Journal

    CubeSats are the "cheap access to space" needed for research and technology risk reduction that's been needed since the dawn of the space age.. and it didn't require some magical new propulsion method or even new economies of scale in launchers, just good standards and a very big customer, the Airforce academy.

    For those of you who find the article a little light on details, here's the scientific paper:

        http://sgc.engin.umich.edu/erps/IEPC_2007/PAPERS/IEPC-2007-145.pdf [umich.edu]

    This preliminary work is now being flight tested.. and, if all goes well, it'll soon be commercially available. When's soon? 3 to 5 years. That's what CubeSats give you, a reduction in lab-to-market from 10 years or longer to 6.

    • by girlintraining (1395911) on Wednesday February 03, 2010 @07:48PM (#31016866)

      CubeSats are the "cheap access to space" needed for research and technology risk reduction that's been needed since the dawn of the space age.. and it didn't require some magical new propulsion method or even new economies of scale in launchers, just good standards and a very big customer, the Airforce academy.

      Yeah... Just what we need -- more tiny objects in orbit around Earth. We have enough problems avoiding crashing into the big satellites we can actually see with radar, let alone worrying about a few hundred rubic's cubes up there. -_- Big satellites can be retired from choice orbits and sent to a maintenance orbit, or back plunging into the atmosphere to burn up. Is this tech going to provide enough thrust to de-orbit when they die?

      • by Angst Badger (8636) on Wednesday February 03, 2010 @07:54PM (#31016924)

        Yeah... Just what we need -- more tiny objects in orbit around Earth. We have enough problems avoiding crashing into the big satellites we can actually see with radar, let alone worrying about a few hundred rubic's cubes up there.

        That was my first thought, too. My second thought, after reading TFA, was that this guy has slightly modified the basic design of an inkjet printer and figured out a way to avoid having his business cut into by refill vendors.

        • by girlintraining (1395911) on Wednesday February 03, 2010 @08:26PM (#31017240)

          That was my first thought, too. My second thought, after reading TFA, was that this guy has slightly modified the basic design of an inkjet printer and figured out a way to avoid having his business cut into by refill vendors.

          At $6,000+ a gallon, we should consider using rocket fuel in our inkjet printers instead. It'd be cheaper...

        • by paganizer (566360)

          My 1st thought was "Damn. I've been hearing about $10,000 to put up 1kg for almost 15 years now; when is it finally going to get here"?
          My 2nd thought was that I'm not going to update my plans for a primarily Solar Powered, electrostatic ion thruster propelled, Black Sabbath "Sabotage" playing mars probe.
          It would take about 15 years to get there.

      • by wizardforce (1005805) on Wednesday February 03, 2010 @08:00PM (#31016986) Journal

        This is where electrodynamic tethers [wikipedia.org] and laser brooms [wikipedia.org] come in handy.

      • What about having Packing Ratio Sats that are designed to stuff as many sats as possible into the payload faring of a rocket? Are cubes the best for cylindrical rockets?
        • Re:PACKING RATIO (Score:5, Interesting)

          by Areyoukiddingme (1289470) on Wednesday February 03, 2010 @08:46PM (#31017424)

          Cubesats are never the primary payload. They're individually tiny, so they're launched in bunches as a secondary payload along with something else much bigger. Their cubical shape makes for easy fabrication of both the satellite itself and the spring-loaded launcher that they're packed in for the launch. Since they're basically freeloading on some other launch, using empty space that would otherwise be completely wasted, their own form factor doesn't really matter much. They fit in the odd bits of leftover space that a typical satellite leaves inside a rocket faring.

      • by QuantumG (50515) * <qg@biodome.org> on Wednesday February 03, 2010 @08:25PM (#31017230) Homepage Journal

        Well, despite what the article says, most CubeSats are launched into deteriorating orbits which eventually burn up.

        As for radar, yes, it's nice to be able to get ground confirmation and CubeSats are more than big enough to do that, especially considering they are deployed on-orbit in clusters.

        • by riboch (1551783)

          I think it is actually the FCC that dictates that a satellite must decay in 25 years after the completion of the mission. This all comes about because they license LEO.

      • by Kral_Blbec (1201285) on Wednesday February 03, 2010 @08:47PM (#31017428)
        FTA

        The Air Force and other government agencies are interested in using CubeSats that can move between different orbits in space, and more specifically, that have the propulsion required to reenter Earth’s atmosphere and destroy themselves at the end of their mission (thereby keeping them from becoming “space junk”).

        • The article also says they don't need it because they'd be placed in a destructive orbit anyway. So which is it? Probably both. There's nothing about the design that requires it to be in a certain orbit. Some may be placed in LEO. Others in polar orbit... others, maybe into a non-destructive orbit.

          Where's the backup if the primary propulsion system fails? Oh. Right... there isn't one. One loose wire and it'll be up there for centuries, instead of years.

      • by chromas (1085949)
        They merge together, synchronize Swatches and assimilate our Trapperkeepers.
      • Cubesats are generally chucked in LEO, and as TFS says, generally don't have propulsion. For this reason, they fall out of the sky very quickly. A few years tops. Once you introduce propulsion, you can keep them up longer, but then you can also have the ability to de-orbit at EOL.
      • by physburn (1095481)
        At least this plan (that all it is, the demo propulsion system, hasn't been built yet). We allow the Cubesats to steer themselves away from potential collisions.

        ---

        Space Craft [feeddistiller.com] Feed @ Feed Distiller [feeddistiller.com]

    • Re: (Score:2, Informative)

      by xquercus (801916)
      The cubesat platform [amsat.org] has provided a means for quite a few orbiting radio amateur experiments [amsat.org].
    • by khallow (566160) on Wednesday February 03, 2010 @10:33PM (#31018214)
      ISP of 3500 s and 5.6 micronewtons of thrust. Not bad for a station keeping device on a 10 cm cube (generates roughly 3 m/s of delta v over a month, if the cube is dense as solid iron), but it's going to be vastly slow (unless, of course, you have an array of them) for other uses.
  • Pico (Score:5, Funny)

    by Brian Gordon (987471) on Wednesday February 03, 2010 @07:37PM (#31016774)

    What, we've exhausted the marketability of the buzzword nano and have stepped it up to pico? Somehow I doubt that regular satellites mass 10^12 kilograms.

  • by $RANDOMLUSER (804576) on Wednesday February 03, 2010 @07:49PM (#31016876)
    The engines on the the DNEPR-1 launched on 26 July 2006 shut down 86 seconds into the flight. It crashed approximately 25 km downrange. So, quite a bit of "bang" for your buck.
    • by nanoakron (234907)

      This should be part of the intro - none of these satellites currently exist. They were all blown up during their failed launch.

      • by Avacar (911548) on Wednesday February 03, 2010 @10:00PM (#31017970) Homepage

        This should be part of the intro - none of these satellites currently exist. They were all blown up during their failed launch.

        Actually that's incorrect. My predecessors had a cubesat on the DNEPR-1 launch; yes it blew up. That said, it was neither the first rocket to carry cubesats, nor by any means the last. TFA is correct in saying there are at least a dozen of these satellites in orbit right now, although many are now past their operation a life, and are waiting to naturally burn up. Saying that "none of these exist" is a bit of a misnomer as well, since there are cubesats waiting for launch in labs all around the world; I myself have two that will likely be going up in about three years from now.

        TFA is correct, however, in saying that no cubesat currently has a propulsion system. It is wrong, however, in saying that no one else is working on this problem; in fact that is the very topic of my own research. I'd be much more impressed, however, if we could see simulations of the corrected orbits, estimated increases in lifetime, and, best yet, a working prototype. Claiming you can do this is bold; it is not an easy problem. Chemical rockets, and even 'standard' electric propulsion are become well-characterized solutions. Cubesat propulsion is on a completely different level, based on both the weakness of the thrusters, and the relatively low masses of the satellites. I feel this is a bit premature to be posted on the front of slashdot; this should have gone up in the 4-5 months TFA claims it will take to get a working prototype. That said, I applaud the novel approach. I hope it works, 'cause I know I'd buy one.

  • A physics process? (Score:4, Insightful)

    by Hurricane78 (562437) <deleted@s l a s h dot.org> on Wednesday February 03, 2010 @08:17PM (#31017158)

    Lozano's design relies on electrospraying, a physics process...

    No way! I thought it would be a magic fairy magic process! (So magic, they used the word twice!) With glitter and unicorns!

    </sarcasm>

    • Re: (Score:1, Offtopic)

      I thought it would be a magic fairy magic process!

      Personally, I was expecting that every CubeSat would have its own pony. OMG! PONIES! LOTS AND LOTS OF PINK PONIES!!!11!!!!

  • Ion drive (Score:3, Interesting)

    by l00sr (266426) on Wednesday February 03, 2010 @08:18PM (#31017168)

    Sounds like a variant of an ion drive [wikipedia.org], which have been around since the 50's.

    • Re:Ion drive (Score:4, Insightful)

      by blair1q (305137) on Wednesday February 03, 2010 @08:34PM (#31017312) Journal

      A variant, yes, but without the high energy cost of ionizing the fuel during thrusting. Also not much need for accelerating structures. if the article is accurate, the reaction mass is pre-ionized and locked into the structure. When you need thrust you pretty much just release it and it pushes you away. Neat trick, if the article is accurate.

      • Re: (Score:3, Insightful)

        by Nyeerrmm (940927)
        Looking at the author's site [mit.edu], the research group has 3 peer reviewed journal articles, 6 conference papers, some ground tests and experimentation, and flight experiments by the summer -- and quite frankly as someone with a bit of experience in electric propulsion and satellite design (grad student in AERO, did some undergrad EP work), it sounds reasonable.

        This doesn't sound like vaporware or pseudo-science -- I'd imagine the article is pretty accurate.
      • "the reaction mass is pre-ionized"

        I wonder how they manage that? Isn't it equivalent to carrying a very large electric charge and somehow keeping it from getting neutralized? Same problem as in large capacitors. If they have tech to do that, wouldn't it be a wonderful electricity storage system!

  • Engage the Ion [memory-alpha.org] Thrusters [wikipedia.org], No. 1.

  • by Jeremy Erwin (2054) on Wednesday February 03, 2010 @09:37PM (#31017824) Journal

    Each edge of a Rubik's cube is 5.7 cm long. The cubesats are 5.5 times as large.

  • You know what's funny about this, is we're going to end up with a situation where increases in the propulsion systems end up sending newer satellites past ones launched earlier before they complete their missions. We'll end up with a cloud of ever decreasing technological junk arriving at distant civilizations....

  • I remember in physics class theorizing a propulsion system for a space ship. I figured that the only way to get thrust would be to accelerate hydrogen to as fast as you can then zip it out the thrusters. You'd have low mass, but high velocity propulsion. It sounds like this guy figured out a way to do this in a compact form. If this seriously works, I'm excited because it will allow satellites all over the solar system for relatively cheap. Put a high imaging camera on your satellite and snap pictures
    • Kinda like the ion thruster on Deep Space 1 [wikipedia.org]
    • If it's in LEO, there should be enough free atmospheric molecules (and hydrogen) to run an EHD-based "lifter" type of propulsion (aka Biefeld-Brown or Serrano effect), given an electrical supply (solar cells?):
      http://en.wikipedia.org/wiki/Ionocraft [wikipedia.org]

      So, no need to store fuel, either.

    • One problem I see coming up is energy, roughly speaking (Newtonian physics) kinetic energy is proportional to the square of the velocity

      So if you double your exhaust velocity (and keep your energy losses the same) you double your propellant efficiency but halve your energy efficiency.

      In other words if you want a spaceship with high acceleration and high propellant efficancy you are going to need to find a shitload of power from somewhere....

  • by buanzo (542591)
    Sorry, had to say it. That CubeSats? BORG CUBES!
  • I stopped reading after the 3rd or 4th time they explained what something as simple as an ion was. Hello MIT, you guys are eggheads, not the Discovery Channel.

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