Why can't the space shuttle be launched by a plane?

A little backstory: when I was in grade school I remember a big to-do about the space shuttle (Columbia?) being shipped from one launch pad to another, I think from Florida to California. The shuttle was simply set right on top of what must’ve been a Boeing 777, as it can’t take off like a plane.

My 7-year-old mind just assumed that those smart astronauts just figured a better way to launch the shuttle: just strap it onto the back of a plane, plane goes up, up, up, shuttle get out of the atmosphere, they cut the lines, and presto! it’s in orbit. I was baffled to learn that it was just a means of transport, and that puzzlement has always stuck with me.

Obviously a 777 isn’t really equipped for extreme altitude flight, but a plane could be modified for this, even with liquid fuel rockets in low orbit. My question is this: wouldn’t it expend less energy to launch this way rather than starting from a dead stop and shooting straight up? It seems that with the fuel burnt in the first 15 seconds of a normal launch you could fly a plane (yes, even a very heavy one) for a considerably long time/distance.

747 is the transport plane.

There are no free rides, it would take just as much energy whether launched by plane or from the ground. what the shuttle didn’t use to reach orbit, the launch plane would.
Besides, it would still take a stupendous amount of fuel to reach orbital velocity, I don’t think that a 747 has the ability to carry that big fuel tank.

There have long been advocates of attempting to do just that, but we have not yet developed the technology to accomplish it. It is not simply a matter of flying high enouh to cast off the shuttle. At some point, well below the altitude to go into orbit, we run out of enough oxygen to propel a turbojet. At that point, the ferry plane must change from jets to rockets, so you have to build a plane that is large enough to carry rockets, rocket fuel, and the shuttle high enough to engage the rockets and then continue to carry the turbo jet engines (with enough fuel to let the plane return safely to earth) while the rockets take the ferry and shuttle closer to a point where the shuttle engines could carry it the rest of the way to orbit.

In addition, a plane carrying the shuttle may not burn as much fuel in level flight as the current rocket system, but carrying the shuttle upward, fully loaded (unlike the current ferry system where the shuttle is carried empty), would take an awful lot more fuel.

The dreamers as NASA hope to have a hybrid jet/rocket ship that will carry itself into orbit some day, but we are quite a few years from developing that vehicle. And rockets work. They have been proved over 45 years.

The Shuttle is still transported on top of a 747. However that’s just the orbiter. You need to add an external fuel tank and booster rockets to put it into orbit.

Launching a rocket from an airplane is not a bad idea. The Orbital Sciences Corp. Pegasus rockets are launched from a modified Lockheed L-1011 airliner.

I think it would be difficult to do this with a Shuttle-sized launcher. The difficult part of a rocket launch is not to get up to the required altitude, but to accelerate to orbital speed (roughly Mach 25). An airliner can only take you 1/30 of the way there. Even the air-launched Pegasus weighs 20 tons, of which the payload is less than half a ton.

Air-launching any sort of space vehicle has a lot of inherent peril, due to the extremely high energy required to put anything in orbit, and the proximity of two large and complex systems. There have been programs designed to roll a solid rocket with a small payload out of the rear door of a large cargo plane in flight, then hang the rocket from parachutes while the plane gets clear. Once the plane reaches safe range, the rocket fires and squibs separate the 'chutes. I don’t know how far those programs ever got, but the limitations are basically:

  1. no room in even the largest cargo planes for much more than a Minuteman solid rocket booster
  2. Minuteman has a surprisingly small cargo capacity (remember, it was designed to get a very small object in a sub-orbital trajectory)

There’s room for a Great Debate, but the closest we’ve got to a manned exoatmospheric vehicle that’s air-launched is SpaceShipOne, a contender for the X-Prize.

But let’s keep in mind that this is not an orbital spacecraft. Suborbital flight is much easier because you don’t have to accelerate to orbital speed. The requirement for the X prize is to reach 100km altitude, which isn’t high enough to achieve a stable orbit even if you could accelerate to orbital speed. As von Braun said in The Right Stuff, “It goes up like a cannonball, and comes down like… a cannonball.”

Remember: There ain’t no such thing as a free launch.

:: D&R very fast :: :smiley:

It’s that “out of the atmosphere” bit that’s the problem. A plane with any sort of claim to serious load-carrying ability and fuel efficiency has to stay well within the atmosphere.

The Russians had planned a similar method for launching their MAKS spacecraft, which was never built or flown.

But the spacecraft itself would still have needed a large external fuel tank to power it’s engines after it lifted off from it’s Mriya carrier plane.

And it would have been a much smaller spacecraft than our shuttle, to boot. Might have been cheaper, tho’.

Personally, I thought it was a shame rocket sleds fell out of favour. Build a five-mile westward railroad track on a gradual upward slope, slap some rockets on a railroad car along with a spacecraft with its own ramjets and rockets and kablam!

My favourite idea, though, is a space elevator built out of buckytubes. In any case, the stifling of other ideas by the enourmously expensive shuttle is reprehensible.

What, nobody’s made a Moonraker reference yet?
(In the movie, a shuttle is launched from its transport position on top of a plane. The plane is destroyed by the shuttle’s launch thrusters.)

(Yes, I know a cite to a James Bond movie ain’t that rigorous. The result shown actually seems logical, though.)

When I was a young kid, sixish, my dad was in the Air Force and for some mysterious reason we were allowed to drive up right next to a 747 that was carrying a shuttle (the Challenger…sigh) and get a good look, or as good as I could get from the back seat of a car and over the heads of the armed guards. The shuttles themselves are not all that big, which was actually quite impressive to little kid me.

I know there are theoretical plans for this sort of thing, but with the current state of the space program I can’t hold out much hope that they’ll ever come off of the drawing board. I’m such a romantic that I hate hate hate hate to say that, but it’s the truth.