So this morning I watched the space shuttle begin it’s journey back to Florida on the back of a modified 747. I’ve always wondered a couple of things about that process; 1) would there be anyone on the shuttle during this flight to monitor systems, stresses, etc? 2) in the event of an emergency on the 747 at altitude, would the shuttle be able to disengage and glide to a landing? Or would the fate of both craft be dependent on the health of the 747? I don’t think I’ve seen this touched on before but please correct me if it has. Thanks.
Related Wikipedia article. I’m pretty positive that no-one is onboard during transport. Way too much risk involved, and any important systems that need to be monitored can be done so remotely. I’m unsure as to the second question, as there was a way to disengage the shuttle during early testing (it’s how they first flight-tested the shuttle’s gliding abilities), but the Enterprise was crewed for that portion.
The systems are all shut down, so that’s not a problem. The Shuttle’s control surfaces are locked into the neutral position during SCA flights.
Stresses on the orbiter aren’t really a big deal either. The 747 is obviously under a lot of stress, but the shuttle is built to handle loads many times more severe than any it experiences in level in-atmosphere flight.
It was always my understanding that the two are bolted together for the duration of the trip and that the shuttle is unmanned.
The flight is meticulously planned since even a few raindrops at 400-500mph can damage the thermal tiles. A plane flies the exact route about 30 minutes ahead of the 747/Shuttle and looks for adverse weather.
Here, this is quite funny: http://upload.wikimedia.org/wikipedia/commons/thumb/f/f7/Shuttle_mounting_point.JPG/719px-Shuttle_mounting_point.JPG
Yep, I’ve flown in front of the Shuttle as the Pathfinder aircraft. We had a NASA guy on the jumpseat who would evaluate what very little turbulence we encountered on the flight and relay it back to the 747. Very cool mission, I’m glad I got to do it.
Damn. That’s one cool job.
Anyways, I am trying to imagine the action of disengaging the shuttle from the top of the 747. That thing falls like a piano, so how could the 747 maneuver out of from under it? Could the shuttle glide at a ratio that would allow it to float from on top of the 747 (at 747 speeds)?
Plus, I don’t think the shuttle could land on a highway or a corn field. If the plane fails, the shuttle is as good as dead anyways.
I’m continually amazed at the wide variety and high level of experienced Dopers we have here!
I sort of got a chuckle reading this post because at first I thought of the guys who drive spotter/signal trucks for wide highway loads… and then I thought of some guy trying to move a couch by tying it to the roof of his minivan while his buddy follows behind to make sure it doesn’t fall off.
Only in a fighter jet. And it’s a 747, not a minivan. And a Space Shuttle orbiter, not a couch. 
The shuttle can be flown away safely, but the crew of the 747 are inevitably killed in the process.
I can’t believe I’m the first to cite to the British documentary Moonraker in this thread! 
The 747 pilot would simply need to push over enough to create some mild negative G.
Nor at any normal (or even abnormally large) airfield. This would be the big argument against having an emergency crew on board: the extremely limited number of places where it can safely land.
Great stuff folks! Thanks for the excellent responses.
Could an argument be made for the need to jettison the shuttle for the safety of the crew of the 747? Is the 747 somehow prepared to evacuate the crew if needed?
If I had to explain to my boss how I had to ditch the Shuttle, I think I’d rather be dead. 
Would the required landing distance change based on the comparatively slow speed the 747/Shuttle flies at? (Compared to reentry.)
Why not? I know it would be going to fast if it was coming down from space, but if there was some way to safely detach it from the 747, couldn’t it land on a normal runway?
The shuttle isn’t going all that fast when it lands even after reentry. It’s doing about 220 miles an hour when the wheels touch down. A fully laden (regular) 747 will be doing about 160 miles an hour when it touches down.
Bolted together the shuttle should add another lifting surface to the mix making it the world’s largest biplane.
As RNATB indicates, the Shuttle’s landing speed and distance don’t depend on whether it’s recently returned from space - like nearly all fixed-wing aircraft, these are simply a function of mass, air density and local wind.
After reentry the flight path and profile are designed to dissipate most of the energy, yielding a normal landing. But even when this is done precisely under favorable conditions - and with a drag parachute - the landing can require over 10,000’.
The longest commercial runways exceed that length, and so might work. But the Shuttle uses a special microwave guidance system, and without this a precise touchdown is unlikely.
Weren’t they originally landed conventionally, though?
I know it can be done because it was done. The Approach and Landing Tests were done with Enterprise before any of the orbiters were launched into space. There’s video at the link.