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There's also the issue of the vehicle on the space elevator falling back to Earth if it detaches from the space elevator (accidentally or deliberately in case of malfunction that stops it from moving up). This means each vehicle will need rockets on it. At low altitude, the rockets are fired to keep the vehicle from reentering the atmosphere too fast at a steep angle, killing the passengers. At high altitude, the rockets fire to raise the perigee enough that the vehicle misses the atmosphere entirely (or enters at a very shallow survivable angle). There's a cross over point that dictates the delta V the rocket must be able to deliver. which if I vaguely recall correctly is greater than 4 km/s.

Pure payload capsules with no passengers wouldn't need this.

The argument for space elevators is that there's a pretty strong limit on how much payload can be launched by rockets due to injection of water into the upper atmosphere. Starship could arguably reach this limit with plausible projected growth rates in traffic.



Ouch, never thought of the re-entry angle problem. Straight down is bad.


Why is the water bad?


In the stratosphere it both contributes to IR opacity, increasing global warming, and can provide ice surfaces on which ozone destruction is amplified. The stratosphere is normally extremely dry, so even small inputs can have an effect that would be invisible in the much moister troposphere.


Aha, so in the stratosphere we should use oxygen / solid carbon boosters?


Their Isp is very low, unfortunately, because the molecular weight of the combustion gas is too high. Ditto for oxygen/carbon monoxide.

Maybe the Isp could be increased by mixing in some helium, but helium is very expensive.


Methalox should suffice for practical and technical reasons?

Compensate the slight loss of ISP by using aerospiked rotating detonation engines...


Methalox contains hydrogen (methane is CH4), which turns into water, either in the engine, or oxidized by the atmosphere after being expelled.


heavy as fuck


It would like, rain down hard?




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