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
It basically comes down to complexity. The scale goes something like:
steam engine < Otto engine < turbine engine < rocket engine
In terms of complexity of combustion and thermodynamics.
A rocket engine is generally running right on the edge of what’s physically possible. If you disturb it too much, bad things tend to happen.
Moreover a lot of (first stage) rocket engines are designed for single use, and are most efficient on their highest power setting. There’s just no reason to add restart or deep throttle capabilities. The recent development of reusable first stages has somewhat changed that, but even on reusable rockets (Falcon 9) only 3 out of the 9 engines have the ability to restart, because for the others that’s just not needed.
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