Ion Engine Propels Probe to Moon 330
lenin writes "The BBC is reporting that Europe's first moon mission, SMART-1, appears to be a success thus far. It also talks about the low-cost technology being used and the charged xenon (ion) propulsion system. Can TIE-fighters be far off?"
Dupe ! (Score:1, Informative)
Karma Whore for the Non-Star Wars Obsessed (Score:0, Informative)
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Re:Ooh, IONs (Score:3, Informative)
Rockets move exactly in the same way an Ion propulsion engine would move. By forcing mass out the rear. Unlike jet or propeller, a rocket ejects its fuel as a means to propel itself.
Re:Ooh, IONs (Score:5, Informative)
Rockets use the same priciple that ion propulsion uses, the law of action and reaction (one of Newton's Laws, can't remember which one off the top of my head). Basically matter is accellerated out the back of the engine (by chemical means in the chemical rocket engine, and by using electro-magnetic forces in the ion propulsion engine). This accelleration causes causes a force to be placed on the engine that is equal to, but oppisite in direction, to the force accellerating the matter.
To answer your first question, Deep Space 1 [nasa.gov] used ion propulsion.
Re:Ooh, IONs (Score:3, Informative)
Re:ionize xenon atoms? (Score:3, Informative)
Re:Ooh, IONs (Score:5, Informative)
I think what confuses some people is that we're used to pushing against something to go somewhere. People have a misguided idea that it's the exhaust pushing against the ground that makes a rocket go, but it's actually the rocket pushing against its exhaust that makes it go. Basically, you mix two things together in a chamber, and under high pessure you shoot ("throw" in the parent's words) the resulting gases out the back end, and away you go. There's no need to interact with the atmosphere which is why rockets work in space and propellers don't.
Re:ion engine limitations (Score:3, Informative)
Even better, if you are doing something like flying to Mars, an ion engine combined with a normal engine has a lot of potential. Just strap a big old disposable solid fuel engine onto your spacecraft and let it burn dry. This will get you well on your way to your destination. Dump the solid fuel engine and continue to burn with the ion engine. You will get to where you are going fairly quickly.
Re:Ooh, IONs (Score:2, Informative)
Rocket exhaust (the flames, etc.) provide a force, yes, but THEY PUSH AGAINST THE ROCKET.
If you are standing on ice (wearing skates) and you throw a bowling ball away from you, you will slide in the opposite direction. The bowling ball doesn't need to hit anything for you to move.
Re:Tie fighters (Score:2, Informative)
Re:Ion drive is cool, but... (Score:5, Informative)
In the future missions you will see these sorts of drives giving much faster flight times to Mercury, Mars, Jupiter, Saturn.. - although for the outer system you may need nuclear instead of solar power.
Yes both this and parent are dupes from previous thread..
Ion Propulsion (Score:5, Informative)
1) Ion Propulsion is NOT new technology. The Russians and German's have been experimenting with Ion Propulsion since the early 1950's. NASA is actually a late comer to the game, although the first with a completed ion propulsion engine.
2) Ion Propulsion do not work in an environment with an atmosphere. An ion engine does not have enough force to lift a sheet of paper more than a few inches.
3) An Ion Engine is very simple in design. For a simple explanation, an inert gas is ionized and injected into a chamber with an opening on one end. The opening has a magnetized torid ring around it. Using the right hand rule (make a fist, stick your thumb out like you are hitchhiking...your thumb is the direction of the electric current, your fingers are curled in the direction of magnetic field flow) you create an electrical flow around the metal torid ring. The resulting magnetic field 'pulls' the ions through the ring, resulting in propulsion.
4) The reason for slow inital acceleration is because the force of the ions passing through the ring is very small, but the velocity of the ions is very high. So, since there is no friction or other losses in space, after a period of time the velocity of the ions leaving the ring increases the velocity of the engine. After a matter of days the engine can be travelling at 10-30,000MPH.
For more information and history on Ion Propulsion engines you can go to the following websites:
http://science.nasa.gov/newhome/headlines/prop0
http://www.grc.nasa.gov/WWW/PAO/ds1.htm
http://space-power.grc.nasa.gov/ppo/projects/ns
Re:Ion drive is cool, but... (Score:3, Informative)
Once you start tying ion propulsion to a nuclear power source, you start being able to achieve higher thrust levels. SMART only uses a little over 1kW of power.
Its very practical.
Ion propulsion can take longer than chemical (although this is not always the case) but it has a much higher specific impulse, and therefore a much lower propellant mass fraction. That means you can get more mass to a destination given the same launch mass, or, take the same payload and use a much smaller (cheaper) launch vehicle.
Re:Ion Propulsion (Score:5, Informative)
First, this probe was from the European Space Agency, not NASA. NASA doesn't own Europe, as far as I know, and can't even afford to replace the bearings on the ancient platforms that carry the Space Shuttles to the launch pad.
Second, NASA's Ion engine (on Deep Space 1) failed in lab tests, and then failed in space. NASA had to "shake" the probe using the gas-based manoevering jets, using up valuable fuel. The probe was a success in the end, but more by luck than design.
Re:Ooh, IONs (Score:5, Informative)
All means of propulsion -on Earth and in Space- use Newton's third law.
In practical terms, the difference is that Ion engines use energy from the sun, to accellerate small portions of matter (ions) over a long period of time.
Rockets use chemical energy to throw out matter, typically violently for a short period of time.
For these reasons Ion engines are predicted a bright future for travel over long distances (to the moon is unusually short in this context), there efficient use of energy wins out in the long run.
However, it seems unlikely that they could be used for lifting things into orbit; then you need to quickly accelerate to high speeds and get out of the athmosphere. Ion Engines are probably not suitable for chasing X-Wings around the Death Star either for that matter.
Tor
Not the first time an ion engine has been used... (Score:3, Informative)
Re:thoughts (Score:4, Informative)
In Kilometers this is:
41,220,846,106,794
So you calculation is a bit off in the time scale.
To reach it in 10 years you would have to be going roughly half the speed of light or 150,000,000 meters per second
This is NOT the first ion engine in use (Score:3, Informative)
They dont really make sense as backup as you have to have two completely separate systems to support them (propellant feed, power, etc). Thats a lot of mass for something that may be nothing more than backup.
They make perfect sense for unmanned missions. Theres typically no hurry to get where youre going, and the mass benefits are large.
They can be used on manned missions, the crew would simply rendezvous with the craft in high Earth orbit rather than being aboard for the entire escape spiral from Earth.
Re:Ion Propulsion (Score:4, Informative)
Actually, what you describe there sounds like a Hall effect thruster. Not all ion drives are Hall thrusters.
DS1's ion engine used charged grids rather than a metal toroid to achieve the acceleration of the ions.
In addition to Hall effect thrusters and grid-based ion engines, there are also arcjets, resistojets, and the ever-sexy-but-a-few-years-off magneto-plasma-dynamic thrusters.
Re:Ooh, IONs (Score:3, Informative)
This is very true, but
1 All ion engines currently discussed use solar cells as their energy source. The whole point is that you only bring matter, not the energy source to accelerate it.
2 If you are prepared to bring an energy source as well, then you are basically back to the rocket case. Sure, you can bring a nuclear reactor, use heated atoms to drive a turbine and generate electricity, and then use the electricity to accellerate ions. But then it is more efficient to use your reactor to throw out particles directly, skipping the step of turbines and electricity generation. Btw researchers are working on such nuclear rocket systems. These would be much more efficient than anything we have today, but also politically problematic to say the least.
Tor
Re:Build your own ion drive (Score:1, Informative)
Army Research Labs:
arxiv.org/pdf/physics/0211001
Re:Other science fiction reference... (Score:3, Informative)
No doubt someone here will do the math that I never bothered trying to do.
I ran some numbers and the feasibility depends pretty much entirely on the weght of the spacecraft.
If we assume a 250,000 mile race, completed in 10 days, (with no resting, since that complicates things more than I want to deal with right now), that means you need a constant acceleration of 0.11 cm/s^2. Not very much, right? Not if you're just accelerating your own weight. In fact, if *all* you had to push was, say, 60kg, it'd be fairly easy. You'd have to generate about 20W of power, sustained, transforming about 1700 food Calories per day into thrust (assuming 25% efficiency).
However, you have to have all of your food, air and water, the spacecraft structure, engines and reaction mass. If all of that (plus your own body) masses 1000 kg, you'd have to sustain 334 W of energy output continuously for 10 days. It's extremely unlikely that any human could do that (even ignoring the non-sleeping issue). According to an article [washington.edu] I found, maximum sustained human energy output is around 150-200 W. It also mentions that Bryan Allen, in his 1979 English Channel crossing in the Gossamer Albatross, managed to sustain ~250 W for 49 minutes, and it wiped him out.
Even a 500 kg gross vehicle weight requires a sustained output of 167 W. 300 kg would require 100 W, so you'd have to be somewhere in that range.
In practice, of course, these numbers are really messed up by the no-resting assumption, so it's really harder than they would show. On the other hand, in practice the vehicle mass would not be constant, it would decline as reaction mass and other consumables were ejected, which means you can get away with higher vehicle masses.
And, finally, these numbers don't even attempt to account for initial velocities or any kind of realistic trajectories.
Conclusion: Your guess is as good as mine!