Jimpop From United States, joined Sep 2004, 49 posts, RR: 0 Posted (1 month 1 week 17 hours ago) and read 2614 times:
I was just watching NASA TV and viewed a replay of Endeavour's landing from earlier today. It seems that there was optimal amount of time and speed for a quick Barrel Roll prior to touchdown. So... would the airframe hold? Is this technically possible?
GST From United Kingdom, joined Jun 2008, 239 posts, RR: 0 Reply 1, posted (1 month 1 week 12 hours ago) and read 2501 times:
Speaking as a glider pilot I can tell you that in an unpowered aircraft a barrel roll is a very difficult maneuver in an unpowered aircraft. To fly the wing inverted usually required increased speed, which means pushing the nose down. Factor in the performance effects of a delta wing and you have a recipe for unpleasantness. Not to mention that you would end up low on the glide slope, which is not something you can easily make up like in a powered bird. I'm sure the airframe can take it, but why would you want to?
A long time ago NASA boffins realized that the shuttle glide flies much like a Gulfstream-2 with thrust reversers open. What did they do? They bought a Gulfstream-2 and modified it to fly with the buckets open. NASA pilots train landing this with reversers, would you barrel roll a plane with reversers open?
Vikkyvik From United States, joined Jul 2003, 3177 posts, RR: 16 Reply 4, posted (1 month 1 week 4 hours ago) and read 2243 times:
Far as I know, a properly executed barrel role is a 1g maneuver, so the airframe shouldn't see any great stresses.
However, the shuttle being unpowered in its descent, I don't know how well it would handle it without losing a lot of altitude - so they probably wouldn't make the runway.
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GST From United Kingdom, joined Jun 2008, 239 posts, RR: 0 Reply 5, posted (1 month 1 week 4 hours ago) and read 2241 times:
Quoting Vikkyvik (Reply 4): Far as I know, a properly executed barrel role is a 1g maneuver, so the airframe shouldn't see any great stresses.
In a powered aircraft this is true, but in a glider I do not know of a way to perform a roll as a 1g maneuvre and maintain the same direction. It can be done as a chandelle, but that would leave you pointing in the exact opposite direction than you were before, height lost and pointing the wrong way....lovely!
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Ferrypilot From New Zealand, joined Sep 2006, 828 posts, RR: 1 Reply 6, posted (1 month 6 days 11 hours ago) and read 1943 times:
Quoting Vikkyvik (Reply 4): Far as I know, a properly executed barrel role is a 1g maneuver,
That's not really true. Imagine you are flying around a helix in the sky or around the coil of a spring. That's what a barrel roll is and you have to pull significantly more than 1g at the start to go up around that helix. The notion of it being a 1g manoeuvre probably stems from the fact that it is possible to unload to 1g as you pass through the inverted. However, shortly thereafter it is necessary to pull more g again as you plunge down around that helix. ...You might expect to accomplish a gentle barrel roll by pulling in the order of 2 to 2.5g depending on the aircraft type and if you are good at them, but 3 to 4g isn't unusual.
2H4 From United States, joined Oct 2004, 7373 posts, RR: 54 Reply 7, posted (1 month 6 days ago) and read 1729 times:
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Quoting GST (Reply 1): A long time ago NASA boffins realized that the shuttle glide flies much like a Gulfstream-2 with thrust reversers open. What did they do? They bought a Gulfstream-2 and modified it to fly with the buckets open.
Rwessel From United States, joined Jan 2007, 612 posts, RR: 0 Reply 10, posted (1 month 3 days 17 hours ago) and read 1250 times:
Aerodynamically, rolling a glider is no problem. Point the nose down far enough to get enough energy input, and shove the stick over. That's key - keeping enough energy coming in to the system (and on a powered aircraft, the engine can do that as well). The problem with almost all gliders is that they're so clean that it's almost impossible not to blast far past redline in the process.
And if do keep your speed within limits, the very slow roll rates of most gliders makes it very easy to get stuck about half way around, leaving you in a very bad situation (true inverted flight) where you need a pretty good pull on the stick the get the nose pointed down far enough to roll back over, and controlling your airspeed in such an unusual attitude (nose way down and inverted) is even harder, not to mention the rather lower negative G limits.
So doing a proper (and safe) roll requires walking a very fine line, and should not be attempted in an unrated glider or without proper instruction.
While there are some gliders that can be rolled (per their limitations), it tends to be the poorer performers with shorter wings. The 1-26, for example, is fully aerobatic, and can be looped, rolled, and whatever (subject to you getting the proper training). The 1-26 is also considered a trainer (or at least something mild enough that it's often used for a first single-seater), and only does 23:1 with a short 40ft wing. Many gliders (but by no means all) can be looped, and that's largely because most gliders are not lacking for pitch control. The rather spiffier Grob 103 can be looped, but not rolled (the POH suggests loop entry at 97kts with a 3G pullup).
Now the Shuttle obviously doesn't have the kind of speed limits your average glider does, nor does it appear particularly slow in roll, nor is it particularly clean aerodynamically (unless you're comparing it to a clump of grass, maybe).
So other than the severe loss of altitude, there should be no reason you couldn't roll it once it got down to about Mach 3 or 4. Before that, there would be no problem with control authority doing the roll, but the altitude loss would probably increase the air density far too quickly, leading to terminal thermal problems. But once you're down to that, why the heck not. You just have to remember to move the landing site a couple of hundred miles further west, and to start the roll at about 100kft...
RomeoKC10FE From United States, joined Jul 2004, 192 posts, RR: 0 Reply 11, posted (3 weeks 6 days 18 hours 51 minutes ago) and read 797 times:
Didn't Chuck Yeager roll the X-1 at the end (powerless) of one of his test flights, I think they show it on the opening to the TV show Star Trek: Enterprise.
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From United States, joined Sep 2004, 49 posts, 
So... would the airframe hold? 
Is this technically possible?
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