Why can't space shuttle enter without using heat shield?

Question

I know the space shuttle enters the atmosphere at very fast speeds and thus reaches EXTREME temperatures and so the need for the heat shield. My question, assuming fuel resources, why can't the space shuttle slow down sufficiently to enter the atmosphere slowly? Someone mentioned to me that at slow velocities they would bounce off. WHY???? It is not a hard object, so why can't they just gradually push through??? Confused!!!! Thanks!!!

As for the pond example, but the stone does finally enter the pond. So, why can't the shuttle find someway to enter slowly?

Albert, I understand the phases it goes through. That is NOT my question. Why CAN'T it go through slowly????

Answer 1

Basically, the shuttle travels at orbital speed to stay aloft. Slowing from that kind of velocity requires incredible force that can harm the crew. The slowing is accomplished safely by turning the shuttle bottom forward so that the force of the atmosphere pushes against the bottom of the shuttle. This creates a tremendous amount of heat, which is why the heat shield is required.

The shuttle can't enter the atmosphere more slowly because there is no way to exert the forces necessary to do so without harming the crew.

A similar question was asked on a NASA Q&A site:

"Shuttle re-entry from space-
How come when the space shuttle re-enters the atmosphere it does not enter more gradually to avoid heating up a lot? I have wondered about that for a while. Hope you can clear that up for me. Thanks."

Reply
"The answer is, such gradual re-entry will not work.

Generally, a craft suspended above the ground (excluding balloons) stays up in one of two ways. Either it has enough velocity (looking at it one way) for the curvature of its fall to match the curvature of the round Earth. Or else, it gets lift from the air its motion encounters, the way airplanes do.

At orbital speed, at least 8 km/sec, the shuttle keeps its height the first way. However, once it enters the atmosphere and slows down, its fall no longer matches the curvature of the Earth, and instead it gets lower and lower. It could have entered more gradually if it could have used the atmosphere to keep its height, the way an airplane does. But at 15-20 times the speed of sound, wings create more resistance than lift, and anyway, presenting a wing edge-forward as an airplane does would concentrate too much heating and pressure on its front.

The shuttle starts re-entry with appreciable altitude and a lot of forward speed, so its fall will take some minutes. The trick is now to lose speed and kinetic energy safely in the time allowed by this fall, and it turns out possible to do so--just barely--without deceleration forces getting too high for the crew. To lose its energy, the shuttle turns its bottom (covered with heat resisting tiles) to face forward, creating a wide shock front in which most of the heating occurs, sparing the shuttle itself. Only at the last stage of its descend does the shuttle actually "fly." By that time, only a small fraction of its energy remains."

Search the NASA website to learn more.

Answer 2

Apparently you are too young to remember the Apollo and gemini Missions but speed had little to do with the heat at reentry.

You can slow it down to a crawl and it won't make it unnecessary to have a heat shield. Basically that is what the old space capsules use to do. They still lit up from the effects of gravity pulling them down at an accelerated rate of speed.

Your question is can you diminish speed to the point that the heat generated by gravity is disipated. Answer No. The slower you go the hotter you will become. If you wanted to lose heat you would have to go faster not slower. However, in going faster the effects of gravity and centripetal force will make stearing the ship nearly impossible and perhaps creat a new heat signature on the top of the shuttle from the added g force due to the added cetripedal force. You are also talking about needing more fuel, and fuel is a combustable. It would be like riding a stick of dynamite.

I also believe you would burn out the hydralics on the flaps, brakes and stearing when you tried to navigate the ship.

Now if you can come up with some sort of anti-gravitational force field which doesn't exist right now then you could slow down the shuttle to where it can make a gradual landing without heat. Otherwise the current landing procedures are the best possible solution. It limits heat primarily to the heat shield. It diminishes speed. And, it allows the pilot to go immediately to manual after reentry.

Sorry but that is just the way it is. It is a relative mass and speed thing.

Answer 3

I don't think that the changing the speed of the object can stop or remove aerodynamic friction. Even if the object entering the atmosphere didn't move, the Earth still is. As long as the Earth (and the atmosphere with it) is moving, I imagine that friction will be present regardless of what speed the object is moving at. After all, it the shuttle wants to reenter the atmosphere it has to move at a different pace then the Earth moves or it would just stay in orbit. Also, at the speed the Earth is moving and the speed the shuttle is moving for entry the atmosphere is like a solid. I don't remember the whole theory, but it has to do with the behavior of molecules and atoms with they hit an object moving at a different speed. It's like a giant car crash between the atoms in the shuttle and those in the atmosphere. When they collide, heat is released.

Answer 4

Well, here's what I'm thinking: The air is really really thin in the upper atmosphere; therefore, if the shuttle slows down too much with reverse thrusters or whatever, it will lose lift and stall. It's the forward speed of the shuttle that keeps it from stalling! In order for the shuttle to slow down enough that it doesn't need the heat shield, it would probably have to use lots of fuel to thrust it upwards like it was hovering. As you know, the space shuttle does slow down eventually before it lands, but not until it's in thicker air. The "bounce off" thing might also be true, and it is definitely true that the air resistance offers a fuel-free way to slow down.

Answer 5

think about it, it's not rocket science (ok, it is!). The shuttle would have to expend a great deal of fuel to resist the acceleration attributable to gravity. engineers do not consider this a serious possibility, and the shuttle is therefore treated as a ballistic body for purposes of re-entry. it is using no fuel at all, except sometimes (usually before actual re-entry) to adjust attitude (pitch, yaw, roll). this does not require large quantities of fuel.

once the orbiter is on proper trajectory for re-entry, it is not using any fuel, and is travelling much the same way as a bullet travels. the atmospheric friction forces on re-entry have been the single greatest design problem for the space program. the tile system which the orbiter uses for a heat shield has been a laughing stock since the '70's. (i'm letting you in on a little secret, here). No credible engineer ever said tiles would work well, and they don't. Why? Because everyone knew they would constantly fall off, endangering the craft and crew. Why was it done anyway? Because NASA is principally a public relations enterprise. The politics were such that many powerful, toupe wearing white guys who drove Chrysler LeBarons with vinyl seats, and cheated on their wives, and were generally not nice people, would have been "embarassed" by a dismantling of the shuttle program. but that's America.

Answer 6

OK folks here ya go. You are correct that the space shuttle comes into the atmosphere at a high rate of speed however the burning effect comes into play once the shuttle hits the atmosphere or air.,gravity comes into play since the shuttle is coming from space with no gravitational pull at all. So the earth pulls the shuttle down as it breaks the atmosphere causing the heat & burn the shuttle comes in at an extreme angle which is actually acting like a break rather than coming in head first & immediately crashing into the Earth. Hope this helps with your question.

Answer 7

The Earth has a protection system in the atmospheree that will burn up any object entering the atmosphere like for example meteorites , that's why you see them going across the night sky , because they are hot and glowing from being burned by the atmosphere to stop it from hitting the earth. although these objects small and big still penetrate the earths atmosphere but they are burned . the space shuttle needs the heat tiles to reenter the earths atmosphere to keep from being burned up. the shuttle must travel at certain speeds to enter earth because of the earths speed and gravitational pull. also the shuttle will enter the atmospher at a angle allowing the heat to hit the bottom of the shuttle where the tiles are at. but most important is the shuttle must enter the earth at certain times so the shuttle can glide to the destination it needs to land. because it is not using any power to fly like a plane to go just anywhere and land. maybe this will make some sense to you.with out the heat tiles the shuttle would burn killing whoever is in it.

Answer 8

Maybe it's more of a precautionary measure? In case the shuttle HAS to enter the atmosphere faster than normal.

Here's another idea: the space shuttle would have to have rocket thrusters pointing all over the place in order to slow itself down enough to enter the atmosphere without the heatshield, and that might be more expensive to do (because of cost of the fuel) than just using a heatshield.

Once you get going in space, you don't stop until you hit something or gravity catches you, hence the need of my expensive directional thrusters for deceleration without a heat shield.

I hope you find a good answer, this one is on my Watch list.

Answer 9

The shuttle cannot enter slowly because it has no power to slow itself down. The shuttle itself does not carry fuel (except small amounts for maneuvering is space). Only the rocket that launches it into orbit carries fuel, and that fuel is totally used up during the launch. Since the shuttle cannot reenter slowly, the friction creates heat, just as others have explained above. Now in case you’re wondering why the shuttle doesn’t carry fuel, the answer is that fuel is too heavy, so they don’t send any more into space than absolutely necessary. In fact, most of the fuel burned during the early phase of the launch is needed just to lift the rest of the fuel for the final phase. The goal is to burn up all of the launch fuel, then discard the rocket so that just the shuttle itself actually goes into orbit. (The rocket parts fall back to earth.)

Answer 10

The only reason that I know that the space shuttle has a heat shield is because of the earth's atmosphere. I believe that when the space shuttle is coming back done to earth it has to break through the area between the earth's sky and the area of actual outer space and this causes a friction and if the space shuttle does not have a heat shield, everyone in the space shuttle would burn up like in a very massive house fire.