Isn't the exhaust just water?!?
The Shuttle and the new Space Launch System will use hydrogen/LOX, which exhausts basically water vapor.
This is all quite separate from the moral issue, to which I have nothing to add.
Energy usage is not the only consideration, and it certainly does matter what it exhausts. Exhausting an inert gas is definitely preferable to a greenhouse gas, which would be preferable to exhausting anthrax, etc.
The composition of the exhaust is going to affect the positivity of the public reaction to a billionaire burning it into public air space for leisure.
You may have a point regarding the public perception; don't really care to weigh in.
Uhh, what moral issue, exactly?
[1] http://www.grida.no/publications/other/ipcc_sr/?src=/climate... (kind of old, but I think the more recent IPCC reports are in a similar vein)
[2] https://eos.org/research-spotlights/the-forgotten-water-vapo...
https://en.m.wikipedia.org/wiki/Kerosene The combustion reaction can be approximated as follows, with the molecular formula C12H26 (dodecane):
2 C12H26(l) + 37 O2(g) → 24 CO2(g) + 26 H2O(g); ∆H˚ = -7513 kJ
The atomic makeup of RP-1 is about CH1.97[1], so at stoichiometric ratio[2] that would yield 71.3% CO2 and 28.7% H2O by mass.
[1] http://www.qrg.northwestern.edu/projects/vss/docs/propulsion...
[2] in reality Falcon 9 burns fuel-rich
The expensive, exotic, high-specific-impulse, but low-density and dangerous option is liquid hydrogen + liquid oxygen (hydrolox), which does indeed create water vapor as exhaust. This particular rocket, however, uses RP-1 (similar to jet fuel - just highly refined kerosene) + liquid oxygen - still burning hydrocarbons, still releasing CO2, but favored because it's cheap, dense, safe, and doesn't need cryogenic cooling.
For comparison, the ITS (and many other Mars mission concepts) use liquid methane + liquid oxygen (methalox), which also outputs CO2, needs cryogenic cooling and is not as safe or dense as RP-1/LOX, but is still safer and denser than hydrogen, doesn't need to be kept quite as cold, and is easy to synthesize on-site on another planet.