speed needed to leave earth?

Question

I've read here that to go into orbit, a spacecraft has to go thousands of mph to do this due to some physics law. I never understood why the shuttle needs a rocket to get into orbit.
So if it just took off on its own, say at the speed of a jetliner, what happens? If it can cruise at the altitude of a jetliner, why no go into space. What would happen? At the edge of being in outer space, does it just get yanked back down?

thanks to the 1st answer below, but I'd have to be Einstein to understand anything from what that link said.

Answer 1

The earth rotates about 1000 mph and travels about 17,500 mph around the sun in orbit.Speed needed would have to equal that. It is possible to have a body float if all the forces were equal. Escape velocity could be found over at NASA or the USAF. Ask Burt Rutan!

Answer 2

Several answers are correct. It is not necessary to achieve "Escape Velocity" to get out of the gravity of the earth IF (underline if) you have a motor and fuel to keep accelerating until you are captured by the gravity of another body. It's like climbing a hill on a bicycle: at the bottom, if you are going really fast you can climb the hill without more pedalling. Or, if you are going too slow you can pedal all the way. By using multi-stage rockets it is easier to get to orbit (or to escape velocity) using the "push like the devil" approach because stages (unnecessary weight) are shed from time to time. To maintain orbit the shuttle must move 5.5 miles every second so that it won't fall more than the curvature of the earth has dropped away in 5.5 miles. If the shuttle engines could run continuously then there probably would be some combination of pitching it up (tilting it) and thrusting, but it would not be practical. Airplanes can fly at lower speeds only because their wings provide lift and they don't fall as they fly.

Answer 3

As the wikipedia entry states -- escape velocity is the speed needed for an object *with out propulsion* to escape the field of gravity. Hence the velocity needed for a space craft without an engine to leave the earth gravity field. The principle is that the object need to have sufficient force to counter the gravitational force -- and one way to have sufficient force is to have the velocity from the set-go (which is the definition of escape velocity).
If the space craft *has* an engine then this is a different matter, as the force can be applied over a longer time -- you just need to have an engine which can burn and provide a slightly higher-than-gavtitational force for long egnough to leave the earth orbit.
So yes you can fly to the edge of the atmosphere but flying require air for the wings to work,so at the time reaching edge of the atmosphere you need a second engine system to leave the earths gravitational field -- in fact this is what space-ship-one does -- which one the competition for being the first private reuse able space flight.

Answer 4

The physics of it is that although it is outside of the atmosphere, the shuttle, and any other satellite, is subject to the gravitational attraction of Earth. The orbital velocity the shuttle obtains is what is needed to move far enough around the Earth that it does not fall closer to Earth. Escape velocity is high enough that the ship will not fall back to Earth under any circumstances. It will fall into the Sun or orbit the sun instead. There is a higher velocity needed to exit the solar system. The exact numbers should be in the Wickpidea reference of answer 1.

Answer 5

You're referring to the "escape velocity." The "escape" part refers to the acceleration associated with the earth's gravity. That's 32 ft/sec/sec. This acceleration applies whether you're going up against the force or free falling with it.
At extremely high altitudes, the air is not sufficient to provide the lift that the high flying jet liners need to stay air born. If you are to fly a space craft into space orbit, you cannot count on the aerodynamics associated with lift - you must simply provide enough thrust to "escape" the force of the gravitational pull - and that is achieved through sufficient acceleration.
Interestingly, many of the experiments pertaining to space travel originate from the belly of a high flying plane - kind of like getting a head start instead of boosting all the way from the earth's surface.

Answer 6

See if this works for you

From the surface of the Earth, escape velocity (ignoring air friction) is about 7 miles per second, or 25,000 miles per hour. Given that initial speed, an object needs no additional force applied to completely escape Earth's gravity. Escape velocity is defined to be the minimum velocity an object must have in order to escape the gravitational field of the earth, that is, escape the earth without ever falling back.

The object must have greater energy than its gravitational binding energy to escape the earth's gravitational field. So:

1/2 mv2 = GMm/R

Where m is the mass of the object, M mass of the earth, G is the gravitational constant, R is the radius of the earth, and v is the escape velocity. It simplifies to:

v = sqrt(2GM/R)

or

v = sqrt(2gR)

Where g is acceleration of gravity on the earth's surface.

The value evaluates to be approximately:

11100 m/s
40200 km/h
25000 mi/h


So, an object which has this velocity at the surface of the earth, will totally escape the earth's gravitational field (ignoring the losses due to the atmosphere.) It is all there is to it.

Answer 7

a space shuttle needs to be blasted into space with the help of a rocket because the space shuttle itself cannot reach such high speeds that a rocket can.
a rocket can use solid or liquid fuel to create that much energy so as to propel it into outer space. the energy to push the rocket and space shuttle has to be large enough so as to lift such a heavy vehicle beyond the force of the earth's gravity. to do this, the rocket (and space shuttle on its back) has to reach a certain velocity so as to escape the earth's gravitational field. this velocity is very aptly named 'escape velocity' and any celestial body can have an escape velocity including black holes. but for black holes, the escape velocity is somewhere close to or even higher than the speed of light (3 x10^8m/s)
rockets are specially designed with certain materials (like fibreglass and other composite materials) to tolerate the huge explosion of heat and energy generated inside it. a space shuttle may not have that much tolerance and it is much smaller so, like other small satellites, it would have to be carried into space by the rocket.
i'm not too sure about jetliners, but i do know that a space shuttle going at that speed and altitude would not get yanked back down. i think the space shuttle has to reach much higher altitudes, than jetliners and therefore requires rockets to take it there in one go.
i hope that answeres some of your queries

Answer 8

try http://en.wikipedia.org/wiki/Escape_velocity