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I don't know much about it, but I'm interested to know why the space shuttle solid rocket boosters were so much more powerful than the F1 engine. 2 of them prod

I don't know much about it, but I'm interested to know why the space shuttle solid rocket boosters were so much more powerful than the F1 engine. 2 of them produced about 87% of the thrust of the 5 F1 engines on the Saturn V. I thought combustion chamber instability was the biggest issue with the big engines. Are solid rockets much more stable?

panick21_ 5y ago
Solid rockets don't really have that problem in the same way. The instability happens in the thrust charmer of a liquid engine resulting from non-uniform burning. The chamber is not very big if you compare it to the size of the tank. Once you press that non-uniform hot gas threw the neck out into the nozzle the expansion happening in the nozzle also expands those imbalances. So you can end up with different pressure pressure in different part of the nozzle leading to vibration and potentially the nozzle ripping itself into pieces. Solids rocket are like a candle with a hole threw it. They burn inside out, not from the button to the top. So there is not really a thrust chamber in the same way. A channel goes from buttom to the top inside the booster. So the 'thrust chamber' is essentially the hole length of the booster. And all that material gets pushed down in the direction of the nozzle. I have never heard any rocket engineer explicitly explain this, but my assumption is that on the way down when everything is pushed threw the neck the gas has time to mix enough so that the instabilities are not that large anymore. I also think the pressure is lower in a solid. Solids have higher thrust but lower efficiency. The thrust comes from the fact that in the solid fuel mix there is lots of other stuff that need to form the solid. Heavier elements that don't participate in burning (thus less efficient) but add thrust. Solids also have the draw back of being incredibly loud and having massive vibrations. Solids also can have 'stability' problems as in that if they are not correctly manufactured, they might not burn uniformly and that can lead to a whole lot of problems and additional vibrations too. Almost no new rocket company uses solids. Its far to expensive and operationally dangerous. At best you can reuse some outer shell, but not the expensive part.

panick21_ 5y ago

Solid rockets don't really have that problem in the same way. The instability happens in the thrust charmer of a liquid engine resulting from non-uniform burning. The chamber is not very big if you compare it to the size of the tank. Once you press that non-uniform hot gas threw the neck out into the nozzle the expansion happening in the nozzle also expands those imbalances. So you can end up with different pressure pressure in different part of the nozzle leading to vibration and potentially the nozzle ripping itself into pieces. Solids rocket are like a candle with a hole threw it. They burn inside out, not from the button to the top. So there is not really a thrust chamber in the same way. A channel goes from buttom to the top inside the booster. So the 'thrust chamber' is essentially the hole length of the booster. And all that material gets pushed down in the direction of the nozzle. I have never heard any rocket engineer explicitly explain this, but my assumption is that on the way down when everything is pushed threw the neck the gas has time to mix enough so that the instabilities are not that large anymore. I also think the pressure is lower in a solid. Solids have higher thrust but lower efficiency. The thrust comes from the fact that in the solid fuel mix there is lots of other stuff that need to form the solid. Heavier elements that don't participate in burning (thus less efficient) but add thrust. Solids also have the draw back of being incredibly loud and having massive vibrations. Solids also can have 'stability' problems as in that if they are not correctly manufactured, they might not burn uniformly and that can lead to a whole lot of problems and additional vibrations too. Almost no new rocket company uses solids. Its far to expensive and operationally dangerous. At best you can reuse some outer shell, but not the expensive part.