Scramjets !!!! It works

ANTIcarrot wrote:

>There are reasons rockets go up and then sideways, and not the other
way
round as the spaceplane concept requires.

With respect, that's a deeply biased argument. Rockets go up for two
reasons:

1/ to get out of the bulk of the atmosphere as efficiently as possible
since it's nothing but drag for them.

2/ to reduce gravity costs on a non-lifting body.

Scramjets will fundamentally take a different approach ("flying into
space") since:

1/ flying your scramjet up and through Mach10 to Mach20ish requires an
atmosphere. ...Preferably a very thin high altitude one. ;-)

2/ the airframe will provide lift to offset gravity.

Thinking further on that thin atmosphere issue (and how the recent test
was /hot/ on the vehicle)...Drag is proportional to the density times
velocity-squared. So it must be possible to develop a scramjet airframe
for which the drag (and hence the heating) is comparable to modern jet
aircraft, by simply flying it high enough.

Here's an example: the SR-71 flew at (a sustained) Mach-3 over forty
years ago, at an altitude of 85000' (~22mb) and it reached skin
temperatures of 430C. If I want to fly my scramjet to Mach-20 before
lighting the rockets for orbit, I'd want to do it where the pressure's
about 1mb for a similar level of skin heating. Say at 48km or so.
(There's a handy pressure/altitude calculator here:
http://www.digitaldutch.com/atmoscalc/). Hmmm...Are there any online
studies of scramjet launch profiles I could be pointed to that have
previously looked into this? Or does the additional need for a TPS on
the vehicle for re-entry generally mean that high speed flight
conditions are automatically covered?

Andy Goddard