Centerfield

I'm glad you posted this, it's a bit of serendipity. I saw a bit of a Modern Marvels program on jet engines just the other night. They suggested that flight path restrictions made necessary due to sonic booms were what made the SST a financial failure. This implies that the speed of sound will continue to be a practical limit on decreasing commercial air flight times. Is that right?

Seeing this show made me realize I don't really understand what sonic boom is in terms of who hears it. If a plane flies over my head at SS speeds, what do I hear? What's the deal?

Pretty much correct. Mach 1+ commercial flight at normal (sub-40K ft) flight levels is restricted to trans-oceanic travel, as they have to get out where the trailing boom won't bother anyone before they can go mach-plus. Gotta be sub-sound over inhabited areas. (The military is a different story--special circumstances.)

"Sonic boom" is an atmospheric overpressure wave caused by the aircraft moving faster than the air can dissipate the compression energy. It's usually no more than the pressure change you get moving a few floors in an elevator, but the magnitude can be quite a bit higher....obviously, the lower and closer the aircraft, the higher the magnitude at ground level. Anywhere really close to ground it can knock you flat and deafen you. Once the craft gets up past 60K or so the effect is negligible at ground level. The military has been using sonic boom overflights at near-ground level to disorient enemy troops in Afghanistan, BTW, and it's reported to be pretty effective as a psy-op weapon. Like having a bomb go off next to you, without quite the force. You're getting slapped with a wall of air, and the boom reaches you before you even hear the plane coming.

I have a friend on this project. If he passes me anything new from yesterday, I'll post it. I'm real glad they aren't going to scrap the BUFF. Too much history there to throw away!

My husband has suggested that, in addition to the sonic problem, the g-forces involved in such fast travel makes the scram jet not very viable. However, by advancing the technology, it could lead to other solutions for speed vs. cost effectiveness.

I love watching the History and Discovery channels. It's so fascinating to see how far we have come technologically and where we are heading.

Have a neighbor who's worked on this project. The spped (Mach 7) is apparetnly prohibitive for passengers.

Chris

Yeah, it's the getting up to speed that hurts, when you've gotta be at Mach 4+ just to torch up. Doesn't apply to all Mach+ travel, but sure does to the scramjet. HyperX was dropped at altitude by the BUFF, then used a Pegasus rocket as a booster to push it up to speed and altitude.

Hyper-X was pure science, not an attempt at a passenger carrier. Unlike SpaceShipOne.

This from my friend on the project, cleared and vetted:

Monday was the first launch window for our bird but we spent the entire day chasing and fixing problems caused by gremlins...Today things worked beautifully. We stayed ahead of the timeline the entire day and at about 2:35 PM PST, the third Hyper-X vehicle was launched. I cannot give exact numbers because of security issues but at real close to Mach 10 and around 100,000 feeet our Hyper-X research vehicle successful separated from her Pegasus booster and flew on her own. The Hyper-X vehicle was a scaled down version of the McAir concept for a Mach 10 cruiser which they developed as part of a program called NASP (National Aerospace Program) back in the 80's so we never really expected this vehicle to do much better than cruise (i.e. maintain a constant velocity with thrust equal to drag in this speed regime) and that is exactly what she did for approximately 10 seconds--she maintained a constant velocity of about Mach 9.6. Then we ran out of fuel and the vehicle flew on and eventually splashed in the Pacific ocean. In a 15 minute trip, we went about 850 nautical miles.

So in one year we have broken the airbreathing flying speed record for a second time. Unfortunately, it may be quite some time before anyone else comes close to breaking this. It will depend if we can get funding to keep this research going--only time will tell.

Anyway, I am very happy now. The only sad note to the day is this was the last research flight for our mother ship--the oldest B-52 still flying. She is 49 years young and has been at Dryden for 45 years. She has to retire because we just can't get parts for her any more and whenever we fly her we need to go to a refinery and make up a batch of her fuel as it is no longer commercially available (JP-4). There may be one final ceremonial flight but that will be it. When she retires she will be parked in front of the main Dryden NASA building next to the last SR-71 that flew. On her side is a silhoutte of every mission and drop that she made at Dryden including the almost 200 X-15 flights. From her nose to her tail, she is covered with her aviation history. The pilot for this last flight, Gordon Fullerton, did a flyby down the runway for everyone to admire her and then did one final touch and go before her probably last landing.