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Ion-Propulsion Craft Reaches The Moon
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."
I think what is most interesting is one of the destinations they're going to visit - the peak of eternal light. Perfect spot for a moonbase - constant sunlight instead of 2 weeks of light and 2 of darkness, water ice likely in nearby craters, and temperatures warm enough that you might be able to get by with passive solar heating alone.
Nobody pushes buttons like our bunny. Big red buttons with labels that say "IGNITION", apparently.
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
it's http://www.esa.int/ not http://www.esa.in/
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.
Well, apollo took a little over 3 days to accomplish what this craft took a year to do. And it's not neessarily "the longer the flight, the more efficient and speedy this method would be". It's all about ISP. The faster the "exhaust" leaves the craft, the less mass of propellant you need to achieve a given delta-V - and it falls off fast.
In fact, ion drives tend to be rather energy-inefficient. However, they get their energy from electricity, which is renewed either by solar or RTG energy. Since RTGs are extremely energy-dense compared to conventional fuels, and solar cells constantly take in more energy, the penalty for a large amount of electrical waste and much, much larger propulsion system (for a given amount of thrust) is dwarfed by the benefits in terms reduced propellant mass.
Nobody pushes buttons like our bunny. Big red buttons with labels that say "IGNITION", apparently.
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).
Don't blame me, I voted for Durga.
Isn't this how TIE Fighers from Star Wars worked? Their wings were solar panels, and TIE stood for Twin Ion Engine.
Brilliant science journalism there. If the smart probe was splitting atoms it wouldn't need solar panels. Not to mention you don't need to split atoms to get ions.
That reminds me of the article that was written on some research I was involved with. We were pulsing cells with high potential electric fields. The field strength was measured in MegaVolts per meter due to a very small gap between the electrodes, the actual voltage was only a kilovolt or so (over a 300ohm load for 5-15 ns). The journalist / engineer-reject thought that megavolts sounded really big and took it upon herself to proclaim that our pulse generators could power a whole city. Moan, groan....
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?
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!)
"After hearing the news that the ESA's slow ion-powered probe has entered Moon orbit after a record-long 13 month voyage, NASA has announced that it will launch an even slower probe that propels itself by gliding on a trail of its own mucous."
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:
- 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.)
- 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.
- 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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