Rockets

A couple of years ago, I went to the Kennedy Space Center. Among the exibits was a full-scale Saturn V. I was amazed that each of the five F-1 engines on the first stage generated 1.5 million pounds of thrust. Though the supports which attached the engines to the first stage were heavy,(maybe four inches or so, the rest of the engine, especially the nozzle which would have to contain the pressure to generate all that thrust, appeared to be relatively flimsy. We’re talking about a force equivalent to the weight of about a dozen main battle tanks. How can this be?

WAG: Most of the pressure/thrust is born by the combustion chamber inside the engine, rather than the exhaust nozzles.

Yeah, the nozzles are open. If they were enclosed, you’d definitely need thicker walls. They also wouldn’t be nozzles anymore. :slight_smile: Anyway, you actually get all that thrust/pressure at the constriction point at the top of the nozzle. When you’re in the shower, get a mouthful of water and spit it out. You’ll get more distance if your mouth is only slightly open.

The energy and power of the thrust also depends on the type of fuel used. Some rockets burn liquid oxygen and liquid hydrogen, like the final stage of the Saturn V and the Space Shuttle upon lift-off. That’s what’s in that big orange fuel tank. (The Shuttle also uses solid-fuel boosters.) Others use liquid oxygen and kerosene, believe it or not. There’s also a fuel called hydrazine used in small rockets and in the thrusters spacecraft use to change their position in space. It needs no oxydizer like liquid hydrogen does, but it produces less thrust.

This is probably more than you wanted to know. I just like to show off. :slight_smile: (I just hope it’s not my ignorance I just showed.) :frowning:


Fighting my own ignorance since 1957.

Another point is that although 1.5 million pounds of thrust seems like a lot of thrust (well, it is!) it is not acting at a single point. I don’t know the diameter of the throat of an F-1 engine is, but say it is 2 feet. Doing the math (let’s see, pi are square – no pie are round, cornbread are square) that would be an area of 450 sq.in. Dividing 1.5M lbs by 450 sq.in. = 3300 psi. Certainly a high pressure, but not unreasonable.

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