"Paul F. Dietz" wrote:
Mach 4 and Mach 25 are very different goals. SS1 is an interesting
step, but don't overstate the size of that step.

SS1 is like a commercial X-15, except more oriented toward
sub-orbital flight than super/hypersonic flight in the
atmosphere. That is, I think, quite an achievement.
Especially considering the way a lot of people go on and on
about the X-15 in the sci.space newsgroups.

The real achievement though will not be technological but
operational. The creation of a profitable company
dedicated to providing commercial manned spaceflight
services. And the creation of a profitable aerospace
venture creating new manned rockets for that purpose.
That would be a far more impressive achievement, should it
happen, and just now there's no guarantee it will, because
it would mean all bets are off in manned space. It would
mean that there was a path (via profitability and new
vehicle design) to orbital manned spaceflight, and to new
designs for such, and finally to activities *beyond* what
governments have done so far.