Re: starship-design: Thoughts on antimatter and fusion...

["N. Lindberg" <nlindber@u.washington.edu>]

Johnny,
	Ion accelerators (linacs, cyclotrons, betatrons, etc.) are usually
quite inefficient.  For example, last year i worked at a high current
vandegraff tandem that ran at 10's of MeV, and 10's of nA (so beam power
about .1 watt) - would anyone like to guess how much power it took to run
the thing?  And the accelerator is the size of a double-wide.  

Nels




On Mon, 12 Feb 2001, Johnny Thunderbird wrote:

> > ANY drive that requires reaction mass is inherently unsuited for
> > Interstellar space...
> 
> It's unwarranted to dismiss the reaction drive out of hand. That's the only
> thing that we know works. We have firm physical expectation that the photon
> drive will work, but no concrete reason to believe it preferable to
> rocketry. We can also expect that acceleration may be available from
> crossing magnetic lines of force, which are demonstrably present in
> interstellar space, for electric motors work that way. However, no net
> impetus is attained parallel to such lines of force. Electromagnetic drives
> won't get you much of anywhere. These three possibilities exhaust the
> physically demonstrated principles for space drives, and beyond these lies
> ectoplasmic vaporware.
> 
> I feel it's presumptuous to reject rocketry for the flashlight drive, when
> no one has a clue how the photons might be generated. Respondents here favor
> the (near) perfect conversion of mass to energy; so do we all. Until we know
> how to perfectly transduce one form of energy into another, say electricity
> into light, this is not even theorizing, just wishful thinking. I'd like to
> get some engineering done, show us the iron. OK, a resistance heater will
> perfectly transform electrical energy into (mostly infrared) light, but this
> has a blackbody spectrum, can't be collimated, so makes a lousy drive.
> 
> I think what I proposed last year, a relativistic linear accelerator for a
> reaction drive, will equal or beat (in terms of efficiency) any specific
> proposal you can produce for a drive based on photons generated onboard the
> ship.
> 
> Johnny Thunderbird
> 
>