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Science-Compliance t1_j1rgx7z wrote

Reply to comment by Mandelvolt in Question about rocket thrust / engines in space and in atmosphere… by MyShatsRRadioactive

Different altitudes / ambient pressures, not temperatures, and no, they're not "optimal". You pay a penalty for using an aerospike over a standard nozzle, but unlike standard bell nozzles, they're less bad at a wider range of altitudes.

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ERROR_396 t1_j1rpnp0 wrote

The nozzle geometry is optimal at a wide range of pressures. He never said aerospikes are the best, just they work optimally at various pressures, rather than just one pressure like with a bell nozzle

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Science-Compliance t1_j1rs56t wrote

Not sure if I didn't explain well enough or you just don't understand, but, anyway, the point I was trying to make is that the aerospike operates at lower efficiency at every altitude than a bell nozzle tailor-made for each altitude would. Over a range of widely varying altitudes, though, the aerospike nozzle, is, cumulatively much more efficient than a bell nozzle that only has one exact design altitude at which it is neither over- or under-expanded. Neither a bell nozzle nor an aerospike exhibit "optimal" expansion in any real-world scenario.

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