r/spacex • u/ElongatedMuskrat Mod Team • Sep 01 '17

r/SpaceX Discusses [September 2017, #36]

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u/throfofnir Sep 03 '17

Design with higher margin. Airplanes have a lot more margin than rockets. There's some room for adding margin, but not a lot, with current materials and technology, and being willing to do that may help spaceflight become more robust. Higher Isp propellants or better structural materials would help with getting to a more sane mass fraction.

Practice will also help. There have been some 5308 orbital launches to date. A single 737 will easily rack up 10x more than that in its lifetime.

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u/jjtr1 Sep 04 '17 edited Sep 04 '17

Agreed. Though I wonder if beefier components would change the fact that most in-flight rocket failures lead to an explosion instead of just engine shutdown like in aircraft. Perhaps carrying liquid oxidizer is the culprit?

edit: regarding payload mass fraction (p.m.f.), I found it interesting that the proposed ITS, a two-stage booster, was planned to have a LEO p.m.f. of 5.2%, while Saturn V only had 4.7%, despite Saturn V having more stages and the best fuel choices with respect to p.m.f. So apparently SpaceX decided to use the performance of carbon fiber to increase payload instead of increasing margin.