Dealing with Stress

K-4 Lesson Plan

Can you deal with pressure? Can you keep going when things get tough? Astronauts have to.

It's not easy going into space. NASA has to know that the crew will be able to do their jobs. And, they have to do it no matter what happens. That's one way that astronauts and fuel tanks are alike.

The fuel tanks of a rocket are under a lot of pressure during the launch. And, NASA has to be sure they can hold up. A lot of forces push on a tank during liftoff. Some are inside the tank. Some are outside. Rocket fuel burns very quickly during a launch. That means the tank empties quickly, too. Have you ever had a drink pouch? You know what happens, to it. The liquid inside pushes on the pouch. You pull the liquid inside out through a straw. There is nothing left inside to push on the pouch. The sides of the pouch cave in.  It gets flat. This is a lot like what happens to a rocket tank when it empties. It doesn’t hurt anything when it happens to your drink pouch. It can cause a lot of problems if it happens to a rocket. So, the rocket has to be made so it will not cave in.

Things happen outside the tank, too. The thrust from the engine pushes up on the rocket. The Earth's atmosphere pulls it down at the same time. The rocket is being pushed and pulled at the same time. What happens to that drink pouch if you push it at the top and bottom at the same time? It crumbles. NASA doesn't want that to happen to a rocket when it launches!

So, fuel tanks have to be strong enough to make it through liftoff. That is why fuel tank testing is so important. But, how do you know if a tank is strong enough without launching it? NASA tests tanks at an engine test stand.

Fuel is put into a tank. The fuel is put under the same pressure it would be at during a launch. The test stand pushes in on the outside of the tank. Then, the tank is emptied. This copies what would happen when fuel is burned out of the engine during liftoff.

If a fuel tank can hold up to testing, then NASA can be pretty sure it will hold up during a launch. And, that takes a lot of stress off everyone.