Re:The SpaceX Starship is a big deal
by davidhyde on Wednesday October 30, 2019 @11:57AM
(#21399106)
I hope SpaceX figures out how to make hydrogen more feasible than methane if they plan to scale up to such high emission levels. I know why hydrogen is not used today. Primarily because of the cryogenic storage requirements in the rocket itself and the requirement to have much larger tanks. Also because of heat problems in the combustion chamber. There are a handful of other reasons but really, the human race should be able to overcome them.
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Re:The SpaceX Starship is a big deal
by brunoTbear on Wednesday October 30, 2019 @12:00PM
(#21399130)
Don't forget the impact of hydrogen on metals: turn everything brittle. For a company founded on reusable componentry, Hyrdogen in your turbopumps, fuel chambers, combustion chambers etc. is kind of a deal breaker.
Interesting that RL-10 descendants are quite reusable. Guess they solved the embrittlement problem :) .
The SSME (now the RS-25 engine) seems to handle the H2 just fine.
They only flew each Shuttle an average of 34 times, with months of refurbishing between flights. SpaceX wants to fly each engine hundreds or even thousands of times, with turnaround less than a day.
IIRC, SpaceX is planning to generate all their methane using CO2 captured from the atmosphere as a test of the equipment that will do this on Mars.
Eventually, it won't be true for a while. Still, the carbon impact of launch one of these isn't that far off from sending a 747 around the world. Most of the fuel mass it's carrying is oxygen and methane is relatively carbon efficient as a fuel compared to bigger hydrocarbons.
We do not need to eliminate every carbon producing process in order to address climate change. There are ways to balance carbon emission with carbon capture.
Let's not give the climate change deniers any additional ammo. Scientifically, our carbon emissions can be high, carbon capture just needs to be higher.