Re: We Go back to the Moon tonight, after 32 Years


Posted by Uncle Al on Sep 27, 2003 at 18:17
(68.5.243.16)

Re: We Go back to the Moon tonight, after 32 Years (Mike Kremer)

It's a good thruster experiment carrying a silly experimental package. Nothing is going to "travel across the universe at high speed" unless you can propose an energy source way better than matter-antimatter annihalation. The math is explicit.

It will be interesting to see if the emission aperture and associated circuitry can survive 18 months of continuous thrust. The stuff is blowing out of there at serious relative velocity (high temp) to be efficient. All at once or atom by atom, surface erosion adds up. Look what happened during the last (PLEEEZE!) Space Scuttle mission.
NASA ion engines started with mercury after considering cesium. Mercury ion engines have multifold curious surprises if you are Officially allowed to think about them. About a $billion later, the engineers were allowed to think bad thoughts - electrical shorts from vapor condensed metal, amalgamation. No more mercury ion engines.

An ion engine blowing xenon doesn't scale well. Price 100 kg of xenon - I bet you can't get it for much less than $100K. Since it is solar-powered, Smart-1 as such won't work past Mars. Nuclear reactors are heavy if you like niceties like radiation shielding so your circuit boards don't get fried.

And one last thing... for maximum energy efficiency you want your end velocity to be about 2/3 your thrust velocity. An ion engine only makes sense if the energy is free (harvested externally) or the /_\v is small (satellite station-keeping).

--
Uncle Al
http://www.mazepath.com/uncleal/eotvos.htm
(Do something naughty to physics)

Follow Ups:


Post a Followup

Name:
E-Mail:

Subject:
Comments:

[ Forum ] [ New Message ]