Quote:
Originally Posted by Parag
why dont the space shuttles just take off from the ground off a runway? it seems easier than the massive fuel and disposable rockets. 747s take off and can fly almost into space with huge amounts of weight, i know the engines wont work without air. but they dont weigh all that much. just a thought i have had for a while now. i would feel alot safer taking off in a airplane than a rocketship.
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A 747 gets nowhere near space. They fly at about 6 or 7 miles above sea level. The edge of space is about 10x higher than that, and they shuttle orbited at about 3 or 4 times
that.
The rockets in the shuttle weren't disposable. After the boosters detatched they fell into the ocean, were recovered & reused on a later mission. The orange external fuel tank for the shuttles main engines was disposable though.
As for why the shuttle takes off vertically vs horizontally, you have to understand that the shuttle, boosters, and fuel tank weigh about 5 times as much as a fully loaded 747. To get the lift required to get such a beast off the ground using wings you would need to have an aircraft substantially larger than the 747, which would again make it heavier requiring a larger aircraft and so on. Assuming it does get off the ground, in order to reach orbit at some point it would have to change over from using the lift of its wings to the thrust of its engines due to the thinning atmosphere. When you change the orientation like that, you have to make everything stronger again, which adds more weight. In the end, to have a single stage to orbit spaceplane that could reach orbit without jettisoning booster rockets or fuel tanks you would have to either make the payload (the stuff you're sending into orbit) so tiny that its not practical,
or the spaceship would be so massive that it might require things like a 20 mile long runway carved out of bedrock, and simply building it could cost more than the entire 25 year shuttle program.
That said, there has been a 2 stage airplane-rocket combination that has gone sub-orbital (~60 miles). The airplane took off conventionally, carrying the small 2 man rocket up with it. The rocket was then released and took off, reaching the edge of space.
As for safety ... don't worry too much. Things can just as easily go catastrophically wrong when lifting off horizontally as vertically.
