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Ion-Propulsion Craft Reaches The Moon

Posted by timothy on from the not-landing-just-saying-hello dept.

Rollie Hawk writes "It ain't warp speed, but it's exciting new technology at work! The European Space Agency put an ion-propelled rocket into lunar orbit today. While not much horsepower is generated, this method of propulsion could be ideal for travel in near-weightless space as it does not require any combustion to occur."

10 of 395 comments (clear)

  1. Is it regular speed? by xanthines-R-yummy · · Score: 4, Interesting

    Does anyone know how the trip time compared other expeditions? I realize that the longer the flight, the more efficient and speedy this method would be, but I was just trying to get an idea of how fast this thing moves. Could cryogenics and this propulsion technology together land humans on other planets?

    1. Re:Is it regular speed? by centauri · · Score: 5, Interesting

      Could cryogenics and this propulsion technology together land humans on other planets?

      No, especially if you're aiming for extrasolar planets. Ion engines are good for a small payload that can take its time getting to where it's going. Humans (even those in some kind of imagined stasis) need something with a higher thrust to get where they're going in a reasonable time (ie, before cosmic radiation carves up their DNA, or a micrometeor holes their lifesupport system).

      --
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    2. Re:Is it regular speed? by purfledspruce · · Score: 4, Interesting
      The high radiation environment of space keeps us from using this method for humans.

      However, it would be quite useful to use this technology to bring cargo to the Moon for possible astronauts to use. For instance, it's possible to deploy an entire habitat--crew quarters, energy producer, perhaps even in-situ resource production ("mining" water-ice for oxygen and hydrogen to feul your return vehicle)--all before we launch humans on a high-energy tracjectory that will get them there in three days, thus avoiding high radiation exposure.

      You could do similar things with Mars. Here's a reference done by the Revolutionary Aerospace Systems Concepts part of NASA:

      OASIS

      It will take a suite of technologies to get safely to other planets, and possibly another suite of technologies to get back.

    3. Re:Is it regular speed? by bcrowell · · Score: 5, Interesting
      Apollo 11 took 73 hours from the burn that took it out of Earth orbit to the burn that inserted it into lunar orbit. This is actually very close to the time it would take to free-fall to the surface of the Earth from a distance equal to the radius of the moon's orbit. This is pretty much always the case with chemical rockets, which work by doing short burns followed by very long periods of free fall: the time to get there is the time it takes to orbit from here to there. To go to Mars, you can use Kepler's laws, and you find that the time to get to Mars in an elliptical orbit is 0.70 years.

      The problem with getting to Mars is fundamentally the radiation. If you send astronauts to Mars on a 0.70-year orbit, without any shielding against penetrating radiation, their radiation dose ends up being on the same order of magnitude as the dose that kills you. This is Not Good :-) There is a variety of ways to get around this:

      1. Use electromagnetic shielding. (There was recently a Slashdot article on this. The idea is to use a quadrupole field, which discriminates between high-mass and low-mass particles.)
      2. Use really thick material shielding. This requires either a really really really thick layer of rock, steel, ... (very heavy), or a really really thick layer of liquid hydrogen. Either way, it's a lot of mass.
      3. Cut the trip time dramatically.
      Solar-powered ion drive could make method #2 practical, because it would theoretically allow very large masses to be moved around without having to lift huge amounts of propellant off of the Earth's surface. However, a ship with a nuclear reactor aboard (not just a passive RTG) could accomplish both #2 and #3.

      Fundamentally, I don't see the justification for sending humans to Mars in the forseeable future. The really exciting science task would be to find out of there is unicellular life on Mars (with a positive result probably qualifying as the most important scientific result of the last 200 years). This can be accomplished with an uncrewed sample return mission.

      Want to send humans to Mars? Great! Please dream up either (a) a valid scientific reason, or (b) a valid commercial reason. I don't think either exists presently, and I don't think either will exist within the next 100 years.

      --
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    4. Re:Is it regular speed? by Rei · · Score: 4, Interesting

      The problem with all shielding methods proposed is that none that are lightweight handle GCR well. Electromagnetic shielding, mind you, does have some very promising applications concerning the Van Allen belts and other lower-energy particles. Right now, it looks like either liquid hydrogen or heavily saturated plastics (HDPE, for example) are going to be the best way to shield a craft on long trips.

      While I agree that there *currently* isn't a good reason to send people to Mars, I think that once we can demonstrate some cost-effective mix of ability to mine low-G bodies, grow realistic amounts of food outside of Earth, create bulk raw structural materials outside Earth, and to produce fuel outside Earth, there is ample reason to work on colonizing Mars. Not only would being able to do these reduce the costs of operation, but even high costs could be justified by the future-potential of using Mars as a triangle trade with Earth and the asteroid belt (one of the few things I agree with Zubrin on). So, I would argue in favor of working on the technology with the goal of eventually having it become a realistic course of action.

      --
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  2. It REALLY Ain't warp speed by guitaristx · · Score: 5, Interesting

    Considering that Apollo 8 made it around the moon in less than a week, and this mission took over a year, we're not dealing with lots of speed here.

    I'm interested in seeing some comparisons with project cost, energy consumption, etc.

    --
    I pity the foo that isn't metasyntactic
  3. Re:Peak of eternal light by binarybum · · Score: 5, Interesting

    man, screw your moon base. Perfect place for a five-star resort. This sounds like prime realty. The europeans should stake a claim to it and auction it off as land for when the moon is colonized. The price this would go for would probably fund a colonization project, oh and a moonbase - somewhere else.

    --
    ôó
  4. Plasma technology is the space enabler by QuantumG · · Score: 5, Interesting

    Although it's called an "ion engine", it's really just the first step in the progression of plasma propulsion. Next up we have the VASIMR which they've been talking about testing on the space station. It can produce slow thrust like an ion engine, or it can produce hard thrust like a chemical rocket. You can power it with solar panels, or you can power it with a nuclear reactor. Eventually, almost the exact same design will be used in fusion rockets, and possibly even antimatter rockets. Then we're in Startrek country with plasma power distribution and ships which you can actually live and work on.

    --
    How we know is more important than what we know.
  5. How is weightlessnes relevant? by mowler2 · · Score: 5, Interesting

    I dont understand why they talk about the probe being (near) weightless in space in the same context as the engine beeing useful in space?

    No matter where the probe is, it has got the same mass, and hence the same inertia. Low-thrust engines work good in space because of no friction and often no requirement on quick travel (if it is a non-manned spacecraft). On earth an ion engine would never work for several reasons, one beeing friction against air and ground, but none of them has to do with the weight of the vechile/probe?

    Or have I misunderstood something?

  6. Re:I don't get it by Headw1nd · · Score: 5, Interesting
    Ok.. the reason this is noteworthy, despite it's lethargic speed, has to do with reaction mass. Ion propulsion and rockets are similar in that both require reaction mass for propulsion- the craft goes forward because something goes back. The speed which the craft goes forward is proportional to the speed that something is ejected out back. Ion drives have ejection speeds far above that of conventional rockets, thus are far more efficient in their use of their propellant.

    So?

    So this is crucial on the long haul. With a reaction drive, when you run out of reaction mass, you're done. The craft becomes inert. The trick here is that the saturn V was out fuel within 15 minutes, wheras this craft is still accelerating a year later. Concievably, it could run for another year, or a dozen. (I don't know how much reaction mass it has) An ion drive craft might be made that could with enough reaction mass for an interstellar voyage, where a chemical rocket could not. (esp. considering the mass needed to decelerate at the ead!)