Talk:Ion thruster
From Wikipedia, the free encyclopedia
Contents |
[edit] Electric propulsion not ion thruster
Hi i think it would be better if the main page for ion thrusters was electric propulsion. This is how it is done in major engineering books on the subject - see Sutton, Rocket Propulsion Elements, or Stark, Fortescue etc, Spacecraft systems engineering. Then electric propulsion is divided into 3 categories; 1. electrostatic propulsion 2. electromagnetic propulsion 3. electrothermal propulsion
Then the different types of electric propulsion (they are many!) are listed in their relevent categories. So ion thrusters would be in electrostatic propulsion, whilst arcjets would be in electrothermal propulsion. Is it ok with ppl if i do this? Can i do this?! Charlie
[edit] Craft charge
Question:
Why is it important that the Ion thruster driven space engine stays electrically neutral? I tend to think that in an almost perfect vacuum (outer space) electrical charge doesn't matter. Because charge is relative to its surroundings - basically nothing in space.
Or is there still too much dust around in "empty" space?
Or is there electrical attraction to be expected from really far away objects (say, a planet)?
- Charge isn't relative: like mass, it's a property of the object, whether or not there's anything nearby to be affected by it. Also, ion drives are being used in places that are, in terms of particles, far from empty, like near-Earth space. Vicki Rosenzweig 11:59, 29 Sep 2003 (UTC)
The problem with needign to remain electricalyl neutral is that if the chassis becomes too electrically negative, then the device must perform extra work to remove the extra electrons adn ionize the workign fluid, plus the exhaust beign still ionized would be attracted to the highly negative chassis instead fo open space, producing no thrust. Its far more complex than that but the explanation should suffice.
[edit] Deep Space 1
Also it needs to be noted in here that DS-1 will NOT be using an ION engine it will be using a HALL EFFECT engine, the difference is technical but ion drives are no longer used for future designs.
Au contrare! DS-1 used the xenon ion thruster developed under the JPL NSTAR program, it was definitely a gridded ion thruster, not a Hall thruster.
[edit] Limits to specific impulse
My understanding of ion engines is that they can increase their specific impulse simply by increasing the grid voltage. However, they normally only operate with an isp of about 3000 because higher isp values would require too much power to produce a decent thrust. Is there any practical limit to how high the grid voltage and isp can get if power supply is not a problem? Could an ion engine vary its isp over a wide range of values by changing the ratio of power being used to ionize fuel to the power being used to accelerate the fuel?--Todd Kloos 23:01, 9 Jun 2004 (UTC)
- Yes and no; ion drives have problems with ions striking electrodes and eroding the electrodes. If you just crank up the voltage, the ions will start to wreck the electrodes. Other problems may also occur; I'm guessing, but you may also have to avoid arcing and corona discharge in the ion stream, and there may be other concerns as well. But certainly power consumption is a major design issue: you have to trade off the mass of fuel required against the mass of the power generation equipment. For very large delta-v (comparable to the specific impulse) improving specific impulse is a very big win. But if delta-v is relatively small compared to exhaust speed, then the reaction mass is not very large, so boosting specific impulse may require you to increase launch weight to generate enough power. This becomes worse when you want to travel far from the sun; power generation gets more difficult, and if it requires an expendable resource, you might as well throw the expended resource out the back as extra reaction mass. --Andrew 06:53, 11 Jun 2004 (UTC)
-
- Thank you for replying. I know that the current generation of ion thrusters (HiPEP) has very significant advantages in thruster lifetime compared with previous ion engines. Presumably this would also allow higher voltages without wrecking the electrodes? Anyway, I know that higher specific impulse is not always better. However, for many missions using a constant isp value is not the most efficient way. I have seen profiles for optimized VASIMR missions to Mars where the spacecraft will start out with an isp of 3000, but the isp will slowly rise during the trip (sometimes reaching a peak as high as 50,000) before going back down to 3000 at the end of the trip. If ion engines can go through a similar variation of specific impulse, it should allow them to increase efficiency shorten mission durations considerably.--Todd Kloos 08:05, 11 Jun 2004 (UTC)
[edit] Scotty Quote
Uh, unless my understanding of wikipedia format is totally off, the quote by Scotty is not appropriate
- Personally, I'd like to know which episode that was. 65.60.222.179 11:24, 15 January 2006 (UTC)
[edit] Freelancer Speculation
The following quote from the fiction section of the article is gibberish to me:
The engine exhaust is visible (relatively) low frequency energy pulses and some fans theorize this could be achieved with a form of electromagnetic flux compression to ramp up the power output of the reactor.
If it's gibberish to someone else (ie, it's not just me), could it be simply deleted?
- What they're describing is a pulsed fusion reaction, where you increase the magnetic confinement field's strength to compress the plasma, which substantially increases the rate of fusion. I'll try to clean it up. --Christopher Thomas 16:08, 6 January 2006 (UTC)
[edit] Delta V?
From the article, under missions: "Of all the electric thrusters, ion thrusters have been the most seriously considered commercially and academically in the quest for interplanetary missions. Ion thrusters are seen as the best solution for these missions as interplanetary trajectories require very high delta V (the overall change in velocity, taken as a single value) that can be built up over long periods of time (years)." This seems wrong. What's important is a very high _average_ velocity, and that can be built up over many years. A high average acceleration doesn't come into it except in that it in turn implies a high average velocity.
- You seem to have misunderstood slightly. Delta-v isn't acceleration. Delta-v is (basically) the total speed change the vehicle would get if you were to accelerate it in a straight line, without gravity, until you run out of fuel.
- Also actual velocity isn't right at all. For example, as a vehicle climbs higher and higher in an orbit around the Earth or the Sun or whatever, it actually slows down. It's all a bit counterintuitive; but as you drop into lower orbits the speed goes up, as you climb it goes down. But you're spending delta-v to do either manouever.
- Sorry, bet that's clear as mud.WolfKeeper 17:19, 3 October 2005 (UTC)
[edit] Imperial Units
Please clear the article of them or at least make SI units the primary unit.
[edit] Illustration
Would this one be worth using as a base for an illustration here? Scoo 21:53, 14 December 2005 (UTC)
[edit] TIE Fighters?
Should some mention of Ion Thrusters in fiction be made? Like, you know, the TIE Fighter. Twin Ion Engine - TIE. Not sure if it's appropriate, but it is a significant cultural thing (Star Wars, not Ion thrusters). --Phant 21:49, 2 June 2006 (UTC)
[edit] Video of Running Ion Drive
I did some google searching and looking on here and no where on the internet can I find any video of an ion drive actually running. I am personally very curious on how the beam of particles looks in motion, and if there is any wobble or anything else of that matter. If anyone has a link to a video, has a video themselves, or knows someone who does, please put it on the net and on Wikipedia as well.
- Found this, it's timelapsed and no sound and real bad quality. http://nmp.jpl.nasa.gov/ds1/tech/ds1_ips.mov If I find another one I'll add that. --62.220.161.10 06:55, 31 August 2006 (UTC)
