Ian Woollard wrote:

Michael Walsh wrote in message ...
Ian Woollard wrote:

Michael Walsh wrote in message ...
The only virtue that a SSTO has over a TSTO (two stage to orbit) reusable
vehicle is the reduction in cost by developing and using only one vehicle
instead of two. If the SSTO does not show a cost advantage then there
is no reason to build one.

That's not necessarily the case, there may very well be reliability
advantages of SSTO, due to system simplicity.

I have made the implied assumption that safety should not be
compromised.

I do not see how you implied that.

Written in between the lines. I made the assumption, but did not
state it.

I should not have made the mistake of using the term "only virtue" but
there is still no reason to build a SSTO unless it shows a cost advantage.

Yes, you said that. It's not totally clear why you said that. If the
cost was much the same for example, then SSTO may be more desirable.

Nope. The cost of developing the SSTO would, in my opinion, be higher
than that of a two stage vehicle. If you disagree with this, that is your opinion,
but not I believe a sound one.


In addition, SSTO does not have the strong tendency of TSTO to drop
stages onto occupied land that can preclude many orbits.

If we are talking about fully recoverable systems then I would expect a
the recovery to take place in a controlled location, even if it was not
a "flyback" system.

Yes, that may help.

I could go on at greater lengths about my opinions on the probable
costs of SSTO development vs. costs of developing a multi-stage
system.

Basically, a SSTO is a more difficult technical problem than the
TSTO systems. NASA claims that SSTO is beyond our current
technological level. However, this looks more like a way of
excusing management failures that resulted in them giving up on
the X-33 and X-34 rather than hitting technological barriers.

Mike Walsh