[ExI] powersats

[Tom Nowell]

I've been following the "getting big loads into orbit"
discussions, and I'm quite a fan of the subject.
 The space elevator does require amazing materials,
but they are theoretically possible. The problem is,
given space junk (all but the lowest part of the
cable) and monatomic oxygen attack (the lowest part),
how do you keep repairing it in time? The wikipedia
article on space tethers 

http://en.wikipedia.org/wiki/Space_tether

mentions the SEDS-2 experiment was expected to last 2
weeks, but was cut after 3.7 days. (the wiki article
includes references to your space elevators, skyhooks
which don't reach the ground, satellite orbit
alteration with tethers - all articles accessible from
the main one).

I like the idea of the launch loop - 2000km iron cable
track moving at 14km/s, using magnetism to accelerate
loads. There's something pleasingly Isembard Kingdom
Brunel about the whole concept, and while it has
issues it doesn't use any materials that don't
currently exist. (The potential dealbreaker on this on
is control circuits capable of adjusting the capable
every microsecond).

Laser launch looks very feasible - the heat exchanger
rockets seem doable with today's technology, it's just
the control system that would require serious R&D. The
only issue with this launch type is that it launches a
huge number of very small packages skywards - Keith,
how small a package can you get away with for powersat
construction?

Railgun/gas gun/launch track technologies - there
exist several possibilities for boosting things to
orbit with short,massive acceleration - I doubt solar
cells would survive it.

The overall space launch market isn't huge at the
moment (55 launches in 2005, according to one report I
read - couldn't find what the total launch mass was
though). Power satellites require a massively bigger
capability than at present. On the other hand, massive
launch capabilities won't be developed unless there's
an industry crying out for it. So, keep on designing
the power satellites - it will keep the hope of space
resource utilisation going.

Tom


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