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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.
Nature has a better article here.
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it's http://www.esa.int/ not http://www.esa.in/
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.
Boing has developed the PAS-5, the world's first commercial satellite with an ion thruster.
It'll be interesting to see, if the Pluto probe ever flies, whether that uses ion propulsion. An ion drive could really make a difference on such a long-haul flight.
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Ion propulsion would be the last drive I'd consider for human transport. It is extremely low thrust, but can maintain drive for a very long time. Take a look at nuclear thermal rockets at nuclearspace.com. The book TO THE END OF THE SOLAR SYSTEM is an excellent primer on the technology and history.
I think it was the TOS Trek episode "Spock's Brain" where Scotty commented on an ion-driven ship, "they could teach us a thing or two!" Right.
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....
In case you're not clear about this... SMART1 was built by ESA, not NASA. With that out of the way... SMART1 costs less than $100M, which is pretty cheap. It was the smallest of 3 payloads on an Ariane 5 rocket. So, this is a small, R&D style mission, very much unlike what happened in 1969.
Ion drives are great in some situations, because they give you a lot more thrust (over time, of course) per pound, then chemical drives. I believe they're about 5 times as efficient. Thus, if you're not in a hurry, this is indeed useful. And NASA used an ion drive for it's Cassini mission to Saturn too...
'Fraid not. To do that requires an enormous, lightweight, electrical power source. No current powerplant, solar, nuclear, chemical or other can provide enough power to generate high thrust when used with VASIMR.
VASIMR is a wannabe fusion power drive. Trouble is, fusion doesn't work well enough right now to use it for this; and they are stuck with trying to powering it the old fashioned ways. It works, but not noticeably any better than ion drive- if you were to get VASIMR to work with a new power supply, you can pretty much just gang up any of the existing ion drive thrusters and get about the same thrust.
VASIMR has theoretical advantages of being able to vary the exhaust velocity to increase the thrust, but even on the lowest settings I've seen them talk about, ion drives usually give better thrust.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"To maintain the acceleration, you need sunlight hitting the solar panels. When you get that far out, the sunlight's going to be very weak. By then you might have picked up plenty of speed (I haven't done the math) but at the halfway point you won't have the acceleration you had near the inner planets.
WWJD for a Klondike Bar?
Inspite of early promise it turned out that the thrust/drag of the ramjet against solar wind and interstellar gas turned out to be below unity. That's bad- you don't go anywhere.
This lead to a concept called M2P2, which is an 'inflatable' plasma. You turn it on and it expands out to a few tens of kilometers, the solar wind pushes on it, and a few months later you are leaving the solar system at high speed, dragged along by the plasma. Basically they ditched the drive system, and just used the collection field.
It worked in a small scale lab test, but nobody knows whether it will really expand out to a few tens of kilometers, and there were a few potential problems, such as tending to vapourise the vehicle due to the very high temperatures of the plasma, still it shows some promise, it's similar to the way the Earths magnetosphere operates.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"Isn't the Washington Times the same paper that is owned by the Moonies?
Yep... if you're uncomfortable getting your news from Rev. Moon (a.k.a. God himself) there are plenty of non-cult-affiliated links for this story.
While you are correct in saying that for such a short distance it seems somewhat a long time to get from point A to point B to use such a propulsion system to travel a huge distance it becomes a much more viable proposition. In terms of acceleration we are talking slow, but over a larger distance it becomes significantly more economic in terms of efficiency. You can travel large distances with greater overall speed compared to traditional means because it will just keep on accelerating.
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This was not about speed. It was about low costs and testing of durability. The US did the testing with Deep Space one. ESA has elected to do a moon mission.
The engine has ran quite a while and has proven that it is well made. I suspect that with the next generations of satillites (micro-sats), this will be the norm for propulsion.
I prefer the "u" in honour as it seems to be missing these days.
well yeah.. or RTG's (Radioisotope Thermoelectric Generators) I'm sure the power-plant will well outlast the propellant supply
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Actually, if you maintain any constant acceleration you can outrun light (you have to do the math, but basically, it's like a variation on Zeno's paradox of Achilles and the tortoise). Given a sufficiently large distance, constant acceleration will always win. Interstellar distances, and in some cases, interplanetary distances are likely to be sufficient to ensure that the constantly accelerating vehicle arrives first.
Well, the flag which the crew from apollo 11 apparently got toasted a bit, IIRC the planted the flag a bit further away on the later missions
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The project home page can be found here: http://www.ssc.se/ssd/smart1.html
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>not for e.g. atmospheric flights.
In atmospheric flights you also have problem with air friction.
>you're mixing up mass and weight.
The mass of the probe is the same in a zero-g environment, or on jupiter - it is the weight that is different, we both agree on that.
However, I still dont see why weight, in it self, is (always) relevant for the acceleration of the probe. When we calculate the resulting acceleration from the engines we only consider the mass of the probe and the engine thrust. Now imagine if we have the probe on earth in a vacuum tube floating on some zero-friction surface or magnetic field (we have force equlibrium). Then if the engine are turned on, they would accelerate the probe as much as they do in empty space even though the probe has weight, right? (now the gravitational force is counteracted by the force of the magneticfield, instead of the centrifugal force in orbit)
SMART-1 uses Hall effect thrusters, somewhat different from the ion thrusters that the U.S. usually uses.
No. statistically speaking the odds are the same as they always were. Just because you flipped heads, does not make tails more likely to come up next.
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However, this is the first time an ion engine has been used to leave orbit and re-enter orbit.
"I'm not impatient. I just hate waiting." - My Dad
You will never reach light speed, but you can still outrun light, as long as you start accelerating at more than a distance of c^2/A away from the light source, where A is your proper acceleration and c is the speed of light (assuming constant proper acceleration). Consider this spacetime diagram; any light emitted beyond the indicated Rindler "event horizon" (blue 45-degree line) will never intersect the worldline of the accelerated observer (red hyperbola).
Look, strictly speaking, the first man, woman, dog, satellite, etc. in space were all European.
There are mirrors left on the moon by the Apollo 11 astronauts that were put there to be able to measure the distance to the moon by laser. It's mentioned here for example. But the conspiracy theorists won't listen to that...
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