Virtually all managers and most all engineers that have grown up in the
current space hardware design bureaus have been steeped in the "rockets
as artillery" school. Design constraints are fire the engine once for
testing, put it on the stand for its first flight, then through it away
after four or five minutes operation. Any effort or materials to give
it a longer life are considered a waste. This does not mean that large
rocket engines can't be built for longer service, only that the
engineers don't need it for "artillery" use. A good example of a flight
weight engine with long life is the RL-10. This engine used on several
upper stages was used (in the short bell version) for the DC-X, and has
had dozens of starts and hours of total time.
Another area that is not considered by most engineers developing RLVs is
that propellents used by most designs are about three orders of
magnitude lower in cost than flight hardware, and that adding propellent
to reduce the quantity of flight hardware will eliminate any failure
modes that were possible in the eliminated hardware. An example would
be if the Shuttle had no wings there would have been no wing leading
edge failure.
RLVs require companies and engineers willing to try new paradigm, not
just incremental improvements. The Space Shuttle was a try, however
many of its design requirements were made for political reasons not
economic or technical.

Mike

In article ,
(Henry Spencer) wrote:

In article ,
Paul Spielmann wrote:
that i have asked peoeple that i think are credible people that work
in the field of physics (not space engineering though) and accoarding
to what they have said: the energy and heat stress of going to orbit
and back are much more higher than for example what a car experience
and therefore it cuts back what is possible to do with space crafts.

...I still wonder though how long
life spans sub/orbital rlv vehicles will have though..