@OrganicMarble: I've heard STS called "one-and-a-half stages", probably because how the SSMEs kept burning all the way uphill. What's your take on this term?

Because of IR radiated from ... the Sun (avg. temp dang hot) That's an xkcd-type parenthetical note. Kudos for the meaningful note.

I'm guessing the OP made a unit conversion error. Apollo By the Numbers lists propellant in pounds mass (lbm), but the OP posted the same numbers with the incorrect unit of kilograms. 18,218 kg = 40,164 lbf... now we just need to find the other 13,000 lb.

(continued) If we stick 100 NEXT engines on this ship, the thrust becomes 100 * g * Isp and the mass ratio falls to a more reasonable 430. Again, someone please check my work.

I took your delta-v (equation 4) and ran Tsiolkovsky in reverse to find the mass ratio. Someone please check my work: 2.38*10^7 (delta-v) / (9.81 * 4000) (g0 times Isp of the best ion engine) = 606.524. e^606.5 = mass ratio of 2.57*10^263. Eek!

@geoffc I appreciate the clarification on Orion drop tests vs. flight tests.

2021 update: Orion has had its fourth and fifth test flights since geoffc's answer, while SLS has had none (per Wikipedia). SLS's first flight is presently scheduled no earlier than January 2022 with an uncrewed Orion Block 1 Crew craft. In the meantime, SpaceX has flown four crews on Crew Dragon (one currently docked to ISS), and three Cargo Dragon trips to ISS.

The last paragraph is roughly what happened with aircraft jet engines. The 747-100 needed four engines partly due to the tech limit on how powerful an engine could be, and partly due to the tech limit on how reliable an engine could be.

Point 3 sounds a lot like cutting Lex Luthor a check. (Warning: TV Tropes link!)

It has now been proven that a helicopter can fly on Mars. Finding reliable cites is left as an exercise for the interested student.

@uhoh Given that these were ubernerds playing with incredibly fancy toys (and getting paid to do it!), I imagine that it was one part "we need to test the entire TTS and LES to validate ascent abort modes producing LOV meet RSO and MFCO specifications without an accompanying LOC" and one part "let's blow stuff up".

I may have misunderstood what was being queried for a citation in CSM's comment. The handbook I posted addresses rockets being on the US munitions list, independent of the top-level requirement to place rockets on the list. I now see the request for cite was over that top-level requirement.

Citation to November 2017 handbook: faa.gov/about/office_org/headquarters_offices/ast/media/…

@peterh-ReinstateMonica: That makes getting back into space even more difficult.

@GdD: Very good question. I'll check the linked question to see if it has an answer, and if not, I'll ask that so that others may learn.