Fun rocket-engineering stuff (intro to exhaust shape):
• The three outer engines are optimized for on-orbit ops,
while the three inner engines are optimized for sea-level ops, i.e. landing.
• The larger expansion ratio produces low nozzle exit pressure to match atmospheric pressure in space,
so the plume gets squeezed into an hour-glass shape by sea-level atmospheric pressure in ground testing.
• The smaller expansion ratio produces a higher exit pressure that matches ground atmospheric pressure,
so it’s not squeezed and is more efficient for landing.
• Any mass not moving straight back reduces thrust and efficiency.
• Yes, this will be on the exam (slide rules only, please)
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• Cultural ref (re: Dostoevsky)
• NOTE: although I try to be original, I’m unlikely to be unique,
so if anyone has a good link to a discussion about this, I’d love to see it