On Wed, 19 Feb 2003, Ian Woollard wrote:
> Semiconductor lasers >30+% efficient (wall plug to light)
50% DC-to-light is now COTS for 800nm infrared diode arrays. *But*, and
it's not a trivial but, the output of those arrays is incoherent: there's
currently no practical way to phase the diodes together. This makes it
awkward to use them for laser launchers. Not impossible, just awkward.
Cheap big lasers are the primary bottleneck for laser launch. A way to
phase-lock diode lasers would be a major breakthrough.
> Coupling ? (how efficient can you absorb laser light and turn it into
> heat) 50%?
80%+ for heat-exchanger rockets, like Jordin Kare's current concepts.
Not nearly as good for the more elegant scheme which blows thin layers of
gas off a chunk of solid propellant: 10-30% and lots of fairly difficult
development needed to make it work well.
> The rule of thumb is 1MW/kg. Actually that's one problem, probably one
> of the bigger problems; is that you need a reasonably huge power plant
> to do this.
Depends on how big your loads are. Jordin said that getting 100MW is no
problem and ConEd can typically give you half a gigawatt on a few hours'
notice. However, there is definitely a bonus for choosing a location
that's fairly near a big power plant or a big power line, because they
can't ship such large amounts to arbitrary locations without running
expensive new lines.
Henry Spencer
[EMAIL PROTECTED]
_______________________________________________
ERPS-list mailing list
[EMAIL PROTECTED]
http://lists.erps.org/mailman/listinfo/erps-list
