[ExI] Spacecraft (was MM)

Eugen Leitl eugen at leitl.org
Wed Jan 5 12:05:57 UTC 2011


On Tue, Jan 04, 2011 at 07:34:14AM -0800, spike wrote:

> That's a really interesting notion Keith.  I have a hybrid notion of sorts:
> we do single axis control using all ground-based drive lasers, and the other

There's one advantage is you put the laser battery at 6 km height,
just as your vehicle leaves the maglev: optical clarity of air.
3 g has acceleration with maglev launch prototypes has been
demonstrated, so after mere 10 km you're well beyond Mach 2.
Assuming you can track the vehicle for another 100 km after
release, this still gives you a minute or so of extra burn.

Instead of accelerating a 100 ton craft, you could probably cut
the mass further, which would need less expensive maglev and
less (you need at least 10^3) of these ~MW solid state lasers,
and according tracking optic.

(There's another advantage of the battery: you could use 
photonic sails, for orbits much above 100 km).

I think the key is leave as much of the drive at home as possible.
Maglev could save you the first stage, the laser could save you
the second, so you're at the Holy Grail: one vehicle to LEO.
Particularly, if you don't bother with controlled reentry, this
can get very simple and cheap (but for the maglev and the laser
stage, and enough photovoltaics and buffer capacity to power 
each shot, which could be once a day, or hourly, for that 
matter). 

> axis of control is done by the spacecraft.  The idea of sweeping in only one
> axis necessitates being on or very near the equator, so imagine one of those
> equatorial mountains as a base.  We lift to 10k using solids or perhaps even
> air breathing recoverable propulsion, then use a sweeping single axis
> control (elevation only) on the ground firing due east, where the bird is
> responsible for moving in the north-south axis to stay in the beam.  
> 
> Another way to do this is to have a variable roll rate on the bird, then
> take advantage of asymmetric thrust of an ablative propulsion system to
> steer itself into the beam.  I need to work on that idea some more.
> 
> Thanks Keith, this is an interesting idea.

-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
______________________________________________________________
ICBM: 48.07100, 11.36820 http://www.ativel.com http://postbiota.org
8B29F6BE: 099D 78BA 2FD3 B014 B08A  7779 75B0 2443 8B29 F6BE



More information about the extropy-chat mailing list