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Although the border to outer space lies only about 100
km from us, getting there and staying there remains
extremely difficult and expensive.
It was realized early on that rockets would be needed
for space travel since they carry their own oxidizers
into the airless void. Furthermore, if a rocket could
throw away fuel and oxiders tanks when they are empty,
reaching orbit with a reasonable payload gets much easier.
The staged, expendable rocket thus became the key enabler
for space exploration. However, throwing away most of
a complex vehicle, which can cost as much as $100million,
after only one use is obviously a major drawback.
If a launcher could be totally reusable, just like
a jet airliner, it would seem obvious that costs of
reaching space (currently about$10000 per kg) should
fall.
However, the Space Shuttle, despite being semi-reusable,
actually costs more per kg than expendables. About 10000
people are needed to maintain and refurbish a shuttle
after every flight. The shuttles were once predicted
to fly 50 times a year but in fact, only about 6-8 flights
per year are practical. (Pressure to increase the flight
rate led indirectly to the Challenger
disaster.)
So clearly, reusability alone will not reduce flight
costs. It must be produced by a robust platform that
requires low operating costs and minimal refurbishment
between flights. A commercial firm must also ensure
that development costs can be covered by operational
income.
Attempts to develop reusable launch vehicles (RLV)
continue with private companies and at NASA (see the
RLV
Countdown and RLV
News sections.) Alternatively, low
cost expendable launch vehicles (ELV) are
also being pursued.
Virtually everyone agrees that at a very high flight
rate, reusables are vastly superior to ELV's. However,
at current launch rates, ELV proponents believe the
development costs of a RLV could never be recovered.
RLV proponents counter that lowering costs will inspire
many new applications and these will in turn drive the
launch rate higher.
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