Why do space shuttles require so much thrust for lift off when a small plane only requires a small engine?

Question

Thrust

Answer 1

a small plane (any plane for that matter) is using its wings for lift ... the space shuttle uses only its engines for lift.

Answer 2

Do the math. A small plane only needs to go about 120 mph. The Shuttle, at the end of the boost phase needs to be going about 17000 mph.

On top of that is the fact that the Shuttle weighs 2000 times more than a Cessna Skymaster.

And, of course, the Shuttle is doing a vertical takeoff, while a Cessna is doing a horizontal takeoff, making maximum use of its wing lift.

Answer 3

I'm afraid you're comparing apples with oranges. If a small plane had to be boosted into orbit, it would have to be strapped to a huge rocket first.

A plane only needs to go fast enough to generate lift with its wings.

But remember that the object of a Shuttle launch is to get it into orbit - which means that the Shuttle has to end up going at least 17,000 miles an hour! That's a lot of fuel for a spacecraft that masses something like one hundred tons.

But remember that you not only have to lift an orbital vehicle like the Shuttle off the ground - you have to lift the *fuel* it'll take to get it up there as well, which means even more fuel in turn, which means a much larger launch rocket...

So rocket enginners prefer to "stage" rockets, dropping off the bits of them that don't absolutely need to get into orbit - kind of like dropping the fuel tank of your car when it gets empty. That may sound silly, but your car will be lighter after having done so.

And this makes sense for a vehicle that is *mostly* a fuel tank, like a rocket or a Shuttle.

Most of the takeoff mass of the Shuttle is expended in the first two minutes of it's flight. The solid rocket boosters, for example, mass nearly 57% of the total mass of the Shuttle at takeoff, but only burn for two minutes or so, then are jettisoned.

At that point, the Shuttle is well on it's way to orbit, and can use it's remaining fuel to acheive orbital velocity.

Does this help?

Answer 4

Single engine airplanes range in weight from less than 1,000 lbs to about 3,000 lbs at takeoff, and rely on the lift of the wings to rise. The engine must produce only enough power to accelerate the airplane forward to a speed that moves enough air over the wings to overcome the weight. This speed varies from under 50 mph to around 90 mph depending on the design of the airplane.

A typical single engine light plane cruises at speeds anywhere from 80 mph to 200 mph, depending on the design and power.

The space shuttle orbiter weighs as much as 290,000 lbs, and the whole rig at takeoff weighs as much as 4.5 million lbs. The rocket thrusters must lift this entire weight straight up off the launch pad.

The weight begins to decline as soon as the engines start, because most of the weight is fuel. But the shuttle must inject a good 3/4 million pounds into orbit at 17,500 mph or thereabouts.

(That speed is not "escape velocity," by the way, but "orbital velocity." Escape velocity is about 25,500 mph.)

Answer 5

A typical model of the Cessna 172, which is the most common trainer airplane, will lift off the ground at 55 knots (about 63 mph) in still air if lightly loaded on an "average" day. It's possible to get it off a smooth runway at a lower speed, but the plane normally won't climb away from the ground at less than that airspeed. In certain configurations, a Cessna 172 might take off and climb with as low as 50 knots of airspeed (about 57 mph), but I wouldn't try that unless absolutely necessary. At that low of an airspeed in a climb, a gust of wind or pilot inattention could be a problem in a Cessna 172. Cessna 172 engines are air-cooled, so best not to climb too steeply/slowly for any longer than needed. Usually try to climb at 70-90 knots. Exact numbers are hard to give - because the answer varies... air temperature, humidity, runway altitude, density of the air, weight, balance of the airplane, whether you use flaps to assist takeoff, type of landing gear, runway surface conditions, direction and strength of wind, etc...

Answer 6

Because the rocket (carrying the shuttle) is trying to work against the Earth's gravity to reach escape velocity--the speed needed to get out of the Earth's gravity well--whereas the plane only needs enough thrust to get off the ground and keep moving forward. The shape of the plane's wings give it "lift"as air goes under/over the wings (easier to illustrate than describe). No amount of "lift" will (at present) allow a vehicle to reach escape velocity, because the atmosphere thins out the higher you go.

Answer 7

The airplane requires only enough forward momentum for the wings to provide lift. The shuttle needs to escape the earths gravity with an acceleration greater than 32/ft per second per second. The shuttles speed would need to increase about 22 mph every two seconds. The airplane need only maintain a constant speed of about 100 mph to remain airborne.

Answer 8

First, the Shuttle is far larger than a small plane. It is more like an airliner.

Second, it needs to get up to orbital speed, 17,500 miles per hour; not the mere 150 mph of a light plane or 550 mph of an airliner.

Third, in order to get up to speed in a vacuum, it needs to use brute rocket power, wings, propellers and jet engines do not work in a vacuum. It can't get up to that speed while still in the atmosphere because friction with the air would use up all the power, just like during reentry.

Answer 9

The shuttle must reach Orbital Velocity, which is the velocity that is required for it to stay in orbit without crashing back down to the earth. This is something like 18,000 mph for the shuttle (I am not sure about that number, somebody correct me if I'm wrong).

Answer 10

Space shuttles are much bigger, and they are taking off vertically. A small plane is taking off horizontally, which doesn't require as much thrust.