h a l f b a k e r yNot so much a thought experiment as a single neuron misfire.
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I saw recently that NASA's Deep Space One spacecraft had an ion engine on board. It basically accelerates negatively charged Xenon ions electrostatically, producing thrust.
It seems to me as though you could increase the exhaust velocity (and hence efficiency) of the engine by feeding the exhaust
Xenon ions into a linear particle accelerator of the type they use in large physics experiments, e.g. CERN in Geneva, Switzerland. The ions would experience extra acceleration, and thus the spacecraft would gain more thrust from the same mass of fuel used.
The way I see it, the "basic" ion engine and the particle accelerator would be built together into one very long engine unit. The accelerator could theoretically be extremely long, but it gets to a point where very long accelerators would be so heavy (and thus expensive to launch from the Earth) that it would be more efficient to launch the mass as fuel instead.
Can someone who's more versed in physics tell me if there's any reason why this wouldn't work? I must admit I don't know enough about the subject area to work out if it's a feasible idea or not!
(?) Micro-Black-Hole Particle Accelerator Annihilation Engine
Micro-Black-Hole_20...nihilation_20Engine
this idea is what has inspired that idea [quantum_flux, Mar 03 2007]
[link]
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I think you've answered your own question. Any accelerator worth bothering with would be too heavy to be worth bothering with. |
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Even though the DS1's ion engine doesn't produce much acceleration, it can accelerate over a very long period of time. Consequently, the DS1 is now the fastest moving man-made object ever. |
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Particle accelerators also use a ridiculous amount of energy. The goal of an ion engine is to generate the maximum momentum (mass times speed) in the output with the minimum energy (fuel/electricity) input. |
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Psst, buddy - forget about the Xenon, this is the Good Stuff:
1H + 11H --> 12H + +10beta
1H + 12H --> 23He
3He + 23He --> 24He + 11H + 11H
4He + 24 + 24He --> 612C
12C + 24He --> 816O
12C + 612C --> 1224Mg + gamma
16O + 24He --> 1020Ne
24Mg + 24He --> 1428Si
;-) |
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What about the opposite... 1) Place a particle accelerator through the core of an asteroid... maybe longitudinally along the axis. 2) point the particle accelerator at DS1. 3) let DS1 'particle decelerate' whatever hits it. Oh yeah, this is the real magic, pray that divine intervention guides each particle directly to DS1. Shoot, we don't need power... just divine accuracy :) |
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Instead of a linear accelerator or a synchrotron you might cogitate on a simple (well, relatively) cyclotron. There are facts 'n figgers on the Internet detailing the bigness of magnets you need to boost a given particle to x speed. I mean, if you have to add ten megatons of magnets and several gigawatts of energy to get from a particle moving at .5 c to one moving at .7 c then why not keep it simple and (well, relatively) lightweight? |
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[UnaBubba]'s right. If you want to keep the engine stationary, just use some mylar to focus the solar wind (or light) onto a solar sail attached to the spacecraft. No magic required. Unfortunately, DS1 doesn't carry a sail...| — | phoenix,
Nov 11 2001, last modified Nov 12 2001 |
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If the ions begin moving too fast they might flare like something from a Flash Gordon movie. |
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Why do these engines need to use particles? Would the same principle work for a gamma ray emitter? Could you just mount a chunk of some gamma-emitting isotope on the rear bumper of your space jalopy? I suppose this in the end is emitting mass also as the stuff will eventually decay into something slightly less massive. |
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What about an iron drive, the creases out the fabric of time. |
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Correct me if I'm wrong, but I believe the Ion drive *is* a variety of particle accelerator? |
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Bungston: they use particles because particles have mass. The more fast moving mass you eject, the greater the equal and opposite reaction driving the spaceship. |
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Bunsen, so glad you're still active. Hope Beaker has recovered from that unhappy incident. And that other incident. |
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Ions have mass - OK. It seems to me that radiation also must pack some sort of a wallop. Consider those solar sail space ship theories - what is pushing the sail? Solar radiation, presumably. Also consider the little rotating wheel in a vacuum bulb that spins when put in the sun. If light has no mass, what is pushing this? |
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I still think that a more elegant solution would be to breed trillions of hamsters, and trillions of anti-hamsters, and combine them at a rate directly proportional to how much acceleration you want. |
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[thumbwax] the kind of atomic fussion produced by a star as it decays would produce enough energy to push (and melt) any object very quickly.
[pmillerchip] a particle accelerator does increase the speed to a particle up to a certain point (~.99999xC) but as further kenitic energy is added to the particle it begins to accumulate mass according to E=MC2, so yes a particle accelerator would produce more drive but the mass and energy the particle acclelerator would entail would probably off set any reasonable gain. (as far as I understand, my knowledge of particle physics is quite limited) |
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BunsenHoneydew, you're right, an accelerated ion engine is a particle accelerator. This makes this idea not half-baked, but twice-baked. :) |
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For best effeciency, mass wise, c would be a desirable exit velocity. |
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But then there is available energy requirements. |
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Then there is engine mass. |
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It would seem that one could make some calculations based on upper and lower limits to get the best use of reaction mass for a given configuration. |
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What is the lighest possible construction for an accelator? |
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What is the conversion efficiency for the accelerator? |
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What avaiable power plants can be utilised? Solar, beamed, nuclear? |
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Give these questions then wher does DS1 stand on the optimisation curve? |
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[LED Prism], the heat and energy from fusion reactions (like the Big Bang, or "simple" solar fusion) can easily be contained in a magnetic field. Only problem, of course, is that powering and maintaining the field requires more energy than the decay generates. If you don't mind a huge energy deficit, and incredibly massive electromagnets, then generating a mini-bang is the way to go. |
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With the X prize coming up, and now that a site has been announced, my question (since I'm depressingly unfamiliar with the mass requirements of ion drives) is "Could an ion-drive system be used to propel an object outside of the Earth's gravity?" DS1's engine provided 4.5 km/s^2 of acceleration (still does, I guess) with Xenon gas and a solar panel, which comes out to about 10k MPH added per hour. Escape velocity is 27k MPH, right? So could ion drives (and 2 hours and 42 minutes of patience) be used to toss an object, or a crew, into space? Perhaps, like the current space shuttle, the object could use "booster drives" to accelerate more quickly? |
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Just a question. Flame away. |
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//Why do these engines need to use particles? Would the same principle work for a gamma ray emitter? Could you just mount a chunk of some gamma-emitting isotope on the rear bumper of your space jalopy?// - [Bungston] |
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This is an interesting idea. Radiation does have a mass, and a momentum, which is proportional to its frequency. So gamma rays have quite high momentum, and could be used to drive a space jalopy. Radioactive isotopes are often used to power space probes as they are an efficient form of long-term energy storage. The problem with this idea is that the gamma rays will be broadcast in all directions equally. Some will be emitted perpendicular to your direction of travel, and have no effect; some will be emitted parallel, and so actually slow you down, unless you put in shielding to absorb them. With an ion engine, in contrast, every ion is emitted in exactly the right direction, so there's a huge gain in efficiency. |
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[spacemoggy] and [Bungston]...the only problem is that there is no known way to do anything more than absorb gamma rays, outside of the only-theoretical realm of programmable matter (where matter is assembled atom-by-atom in a certain way to do a certain thing). |
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Should one be able to assemble this "programmable matter," you'd have to build a reflective surface of densely-arranged electrons on three sides, and have an array of hexagonally-framed holes on the fourth side (take a look at the tail light of your car for an example). |
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Barring this matter shielding, that you could just dunk a piece of gamma-emitting matter into, using that matter would simply destroy the jalopy and kill everyone aboard. Other than that, it's a good idea. |
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EDIT: Good heavens, I'm a killjoy. |
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[shapu] You could just place a sheet of lead between the spaceship and the gamma ray source. This would only absorb the rays, so you would only get half the momentum transfer that you would get from your reflector, but it would work, in a sort of rough-and-ready way. It would be hella heavy, of course. |
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Re my earlier anno, and the problem of rays going off in all directions: I'm wondering whether it is possible to focus at least some of the rays into the right direction, using a gamma ray lens. No idea what that would have to be made of though. |
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Wow, not only am I a killjoy, I'm a lazy one at that. |
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Right underneath the article I had read about programmable matter was an article touting the creation of the HESS telescope in Namibia. HESS is a gamma-ray observatory that by necessity must reflect gamma rays from a parabolic mirror into a camera.
(http://www.saao.ac.za/~wgssa/as5/steenkamp.html) |
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The rays are reflected by aluminized glass mirrors, with a quartz coating to protect the glass and alumnimum from breaking down. I don't know how well this would work with a much closer source of radiation, but it seems that it would be a start. As for directing the emission, I'm serious: take a look at your taillight or headlight on your car. That pattern of mirrors and reflectors does a fine job of doing it with light, so it could easily be adapted to gamma rays. |
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Still waiting and hoping my other plan isn't too idiotic. |
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Sooo... by placing the gamma ray source at the focus of a similar mirror you would produce a directed beam backwards, and so harness a good proportion of the momentum available. Looks like [Bungston]'s space jalopy might have legs after all. |
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The basic rocket equation describes how the exhaust velocity determines the final velocity of the spacecraft. Particle accelerators with energy beamed from the sun and converted to elecricity is the only way to go! Even thumbwax's fusion idea doesn't thow off an exhaust with anywhere near the required veloctiy.
Basic rocket equation:
e**(vel_change/vel_exhaust)
=(fuel_used/craft_mass) |
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//Combine a spacecraft ion engine with a particle accelerator// |
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Easier said than done! Unless you could create a.... hmmm.... [Micro-Black-Hole Particle Accelerator Annihilation Engine]! |
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So, take your glass eye, mount it on a
spindle, attach a small blower fan, place all
of this on top of the cylinder head, then
get into your car and go as fast as
you can from nought to sixty...... and what
have you got ? |
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an axle, aerated, eye on engine of course ! |
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[Shapu] //"Could an ion-drive system be used to propel an object outside of the Earth's gravity?" DS1's engine provided 4.5 km/s^2 of acceleration (still does, I guess) with Xenon gas and a solar panel, which comes out to about 10k MPH added per hour. Escape velocity is 27k MPH, right? So could ion drives (and 2 hours and 42 minutes of patience) be used to toss an object, or a crew, into space?// |
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No. That acceleration figure is WAY out. 4.5 km/s² is about 510 gees, and would turn a human to mush. DS1 has a mass of 373 kg, and a thrust of 92 millinewtons, giving an acceleration of about Œ mm/s². Enough to lift off from an asteroid with a radius of about 1œ km. |
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The ion drive is kind of nice because it does not particularly weight much. Most of the business end is a block of ceramic with some electrodes, then there's the fuel tank. The only heavy part is in the power supply system, which shrinks every year with the rest of our electronics. |
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//4.5 km/s^2 of acceleration// |
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Are you sure? That's 450G... |
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I'd already made that point, although I'm not sure how I got 510; it's more like 459. (Little 'g'. I wrote 'gees' to avoid confusion; G is the gravitational constant, g is local gravitational acceleration, and g<sub>0</sub> is standard Earth gravity, 9.80665 m/s²). |
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Micro black hole accelerator engine turns up file not found for
me.
That is precisely the drive I was proposing. |
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Funny, how in 2001 the annos were focused on concern for my
sanity. |
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Now the annos are are above my ability to comprehend. |
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Btw, I don't know who pmillerchip is, but I took he'll for this idea,
jutta. |
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Oh, oops. I'm very sorry. I did it 5 years later. Weird. No baked
or such. + from me. |
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isn't an ion drive already a particle accelerator ? |
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From my understanding ion drives are currently linear
accelerators. Maybe in the future they will twin them. |
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