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It's well known that pressure fed engines are mechanically simpler, and therefore cheaper than pump-fed cycles (although pressure fed has worse performance). However, I haven't found any sources that say how much cheaper pressure-fed engines are, compared to staged combustion, gas generator, and electric pump-fed cycles (specifically for a reusable mid-sized launcher, so something that has the payload capacity of a Falcon 9). Compared to staged combustion or gas generator, I would guess that it's substantially cheaper for a reusable vehicle, as the turbopumps require tons of maintenance between flights. However, it gets interesting for electric pump-fed. Anyone has any insight?

Thanks!

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    $\begingroup$ What's your cost metric? $\endgroup$ Sep 14 '20 at 19:20
  • $\begingroup$ @OrganicMarble Cost per flight seems to be the most logical one, assuming that all flights boost the same payload up to the same reference orbit. However, I'll admit that I'm not an expert in these matters, so if there's a better one feel free to suggest it. $\endgroup$ Sep 14 '20 at 20:36
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    $\begingroup$ Should development costs be included? $\endgroup$ Sep 14 '20 at 20:40
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    $\begingroup$ @OrganicMarble Hmm, good point. I'm asking about reusable launch vehicles that would have flown many times, so I guess the development costs would be spread over tons of launches so it wouldn't be significant - for example, the F9 cost 300 million to develop and flew 94 times, so development costs only accounts for around 3 million each flight. I guess it would be a major factor for a startup or something, but I guess just ignore it for now. $\endgroup$ Sep 14 '20 at 20:43
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    $\begingroup$ @OrganicMarble Yeah, I meant pressure-fed. I'll go fix that. $\endgroup$ Sep 14 '20 at 20:47

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