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.

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.

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.

The Russians continually launch over land areas and the Soyuz reaches the
ISS on a regular basis. I am not sure what the flight path would have been
for a Columbia rescue mission.

There isn't one, first stage drops on China IRC.

That is somewhat of a special case.

No, not at all. It heavily constrained the location of the ISS itself;
the ISS is where it is because the Russians could reach it even though
many other orbits were within delta-v range of the Soyuz vehicle. The
ISS is constained by the multiple stage vehicles used to reach it.

Mike Walsh