Launching a Scram Off the Blackbird

Considering that Pegasus is capable of puting a payload in to LEO, Pretty fast. Much faster than Mach 3. According to the NASA Site, it is something over Mach 4, and 95000 feet MSL--well beyond the operating capability of the Blackbirds. Check

Reynolds Numbers don't mean much in those flow regimes.

Bret

Depends upon the deign. Lower that Mach 4, how much is an issue. Recent programs have looked at designs which would start around Mach 3.5 using either turbine or rocket based low speed systems to get them there.

Specifically with regard to the Hyper-X tests, these were point deigns. The engines for the Mach 7 and 10 tests were optimized for operation at each specific test point.

In each of the two Hyper-X tests the Pegasus actually boosted the research vehicles to Mach numbers slightly over the test point. Ie the faster speed reached in each flight was during the final portion of the boost phase. The RV slows down a bit after separation from the booster while it's attitude is adjusted and then during a cowl open unfueled tare portion preceding the scramjet powered portions of the flights.

Doesn't matter, there are no operational SR-71s. Also the track recode of launching the D-21 drone from between the tails was not so good. The designs of turbine and rocket based combined cycle systems mentioned above assumed ar-launch of the B-52 around Mach 0.8, using the turbine or rocket systems to get to scramjet takeover. The programs doing this, X-43B and ISTAR were canceled over a year ago. ________________________________________________________ Ed Ruf Lifetime AMA# 344007 ( snipped-for-privacy@EdwardG.Ruf.com)