With jet engines, it’s relatively easy to light it up and throttle. I know you can’t shut them down mid-flight and then turn them back on while still in the air, but you can easily throttle them. Now with rocket engines, you can only light most engines 1-3 times, and their throttle ability is minimal. Why is this so?
Thanks in advance.
In: Engineering
I’d guess the most famous engine with throttling ability would be the Apollo LEM descent stage. It was restarted 4 times on Apollo 9 (earth orbit test), though the design criteria was two restarts. Wouldn’t be a first choice these days due to hypergolic propellants I’d think, but it was mid-1960’s tech. There’s development these days on a throttling RL-10 (a 1960’s vintage that’s been upgraded over time), since NASA wants a much more powerful engine for future lunar use.
Rocket engines and jet engines are vastly different things though – jet engines use spinning vanes to increase air and fuel pressure, rockets require pressurization or pumps, or even a “mini rocket engine” that functions as a massive fuel and oxidizer pump.
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