The 747-100s used by NASA are almost completely stripped out on the inside (they're basically the cargo versions without the cargo-handling hardware). The shuttle is below -- actually, quite a bit below -- the maximum lifting capacity of the airframe. The takeoff weight of the 747 with the shuttle is actually less than the takeoff weight of a passenger 747 with a full 460+ passenger load fueled for a SFO-Tokyo run.

The trick with the shuttle ferry configuration is the greatly increased drag and the change in the overall vehicle's center of gravity -- not the weight.

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Nobody has ever claimed that the shuttle is "enviro-friendly".

They don't launch it from California because you can't launch things over populated areas. You maximize your lifting capacity if you launch in the direction that the Earth is spinning -- i.e. to the east. East of Florida is about 6000 miles of open ocean. East of California is all of America. You can launch into a polar orbit from California -- and the Air Force does exactly that from Vandenberg AFB -- but that's less efficient. There was a shuttle launching facility built at Vandenberg, but (a) it was only going to be used for military shuttle payloads -- spy satellites, which use polar orbits or sun-synchronous orbits (which are a specific type of polar orbit), and (b) the military decided to remove its payloads from the shuttle after Challenger, which eliminated the need for California launches.

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They film everything so that in case something does go wrong, even minorly so, they can review the tapes afterward.

If it wasn't for this level of detailed recording, we'd never have Spacebat, now would we? No.

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@Jeff_McAwes0me:
It has manouvering thrusters, but the main three only draw fuel from the big external tank. And there is no way those teensy little thrusters are going to provide enough thrust to do more than creep down the runway. Heck, I'd put money on the first snail that comes along...

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Instead, the orbiter is designed as a glider -- and a poor one at that. This turned out to be the best option available from an aerodynamic standpoint. Ultimately, the primary job of the shuttle's wing is NOT flying -- it's dissipating energy. The shuttle has to slow itself from orbital speed (about 18,000 MPH) to 200 MPH in order to land. This is, in large part, accomplished by just smacking that big, flat bottom surface directly into the atmosphere, which generates drag and friction. It also generates a lot of heat, which is where the tiles come in.

But ultimately, the wing isn't designed to be a lift generator, like it is on a normal aircraft. It's designed to best handle the energy dissipation issue while still leaving the vehicle as a whole as a controllable, landable glider. To make a long story short, this means that the wing does not have nearly the lifting ability as a normal aircraft's. The shuttle drops like a rock -- a controlled rock, but a rock nonetheless. Its angle of descent (the angle between a baseline that's straight ahead with no altitude change along the direction of travel and the line that marks the actual path of the plane) for most of the aerodynamic portion is something in the 45-50 degree range. Airliners approach at 5-10 degrees, tops. The wing provides enough lift to "flare" at the tail end -- right above the runway -- and reduce the landing force to a small enough value that the landing gear can handle it. But the shuttle doesn't even approach "flying" like we know it.

So even if you strapped engines onto the shuttle, the wings aren't designed to take off. You'd have to get the vehicle up to a HUGE velocity before the lift generated by the wing would offset the total vehicle weight. We're talking thousands of miles per hour. So it's impractical even in theory to fly the shuttle.

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That said, I have to imagine the shuttle's wings do lift, taking some load off the 747's wings.

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@Marcelo: Well, if it DID fall..... from what... like 350 miles high or something.... i seriously doubt there'd be anything left for them to piggyback on that 747. Think you might be thinking of those old command modules that would be occupied upon reentry such as the one used on the Apollo mission..... which i think only really had a parachute, and i believe generally shot for a water-landing.

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@I said Bud Lite, not Flashlight Mr. Officer.:
I'd guess that has more to do with the extreme altitude/airspeed restrictions on flying when laden, as they don't get to benefit from the same jetstreams that civilian passenger jets use, and flying too slow means you're fighting gravity for a longer period of time over the same distance.

@OMG! Con Seannery!:
On a landing approach, that's more or less true, but primarily because they're running on fumes at that point. They simply don't have the fuel reserves to achieve the speeds they'd need to regain any altitude that they've lost. When it's strapped to a fully fueled 747, things are a bit different in that regard.

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And the G-forces experienced returning in an Apollo-like capsule are greater than that of the Shuttle.

The height used varies based upon where the shuttle is/was going. I believe Hubble sits up around the 380+ mile mark? But, much of the controlled fall through the atmosphere is burning off energy. All of that energy used to put the damn thing in orbit has to be bled off at a controlled rate.

It's glide characteristics vary based upon speed. Hypersonic is 1:1, Supersonic is 2:1 and Subsonic is like 4:1? It has a pretty severe descent rate and you'll read common comparisons to it being a "flying brick".

It really isn't a very good glider at all.

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The Shuttle is mounted in a slightly nose-down position to give it a slightly NEGATIVE lift -- i.e. it pushes down a little on the 747. This greatly simplifies the mounting hardware.

If you wanted to use the shuttle's wings to contribute lift -- and it would be a minor amount of lift in any event, certainly not enough to offset the increased drag -- you'd need a very strong mounting system that was integrated with the overall airframe of the 747. If you basically eliminate the lift, you need a lot less structure to hold the shuttle onto the 747, because you're not generating a lot of "pull" upwards on the mounting struts.

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Wikipedia tells me that NASA has two Shuttle Carrier Aircraft, one 747-100 and one 747-100SR.

Some quick Googling reveals that the maximum payload of the 747-100 is 76,280 Kg.

The empty weight of the Space Shuttle is 78,000 kg, leaving it a smidgeon above the maximum payload of the 747 (if a smidgeon can be 2000kg).

[en.wikipedia.org]

[en.wikipedia.org]

[en.wikipedia.org]

[www.zap16.com]

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Also covered in the Wiki article is the performance characteristics of the Shuttle Carrier Aircraft...

Empty weight: 318,000 lb (144,200 kg)

Max takeoff weight: 710,000 lb (322,000 kg)

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"The aircraft was extensively modified by Boeing in 1976.[2] Its cabin was stripped, mounting struts added, and the fuselage strengthened; vertical stabilizers were added to the tail to aid stability when the Orbiter was being carried. The avionics and engines were also upgraded, and an escape tunnel system similar to that used on Boeing's first 747 test flights was added. The flight crew escape tunnel system was later removed following the completion of the Approach and Landing Tests (ALT) due to concerns over possible engine ingestion of an escaping crew member."

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There have been several newer more efficient and larger revisions of the 747 fuselage and engine choices in the 80's and 90's alone, not to mention the current decade in which we should the the 747-8 Cargo model released.

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