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Comment by neaanopri | Hacker News Reader

I'm curious what the actual marginal cost of an additional pound on the shuttle is - surely you can't just divide?

According to https://en.wikipedia.org/wiki/Criticism_of_the_Space_Shuttle..., the incremental cost was $6,435 per pound and the complete cost was $27,000 per pound. I thought a lot about this, and there are arguments for using either number.

The incremental cost refers to one shuttle flight divided by pounds.

I think what OP was asking is - given shuttle already had a mission with some spare payload capacity, how much did it cost to bring one more pound into space? I think this question has a relevancy to the fact the printer was surprisingly heavy and came with a lot of paper. I'm not sure if there's a good way to calculate this though.

Its a bit of a nonsense calculation anyway. Fundamentally the shuttle's engines had a maximum thrust they could generate, and there's no amount of money that could easily change that. That dictates the maximum shuttle + crew + payload weight and it's just a question of how you parcel that out. Include a heavy printer, and you constrain the maximum crew and/or payload. (There was one flight, recently covered on HN - https://en.wikipedia.org/wiki/STS-93 - where they flew with fewer crewmembers because the payload was so heavy).

There are reasons for not using maximum load: Fuel. And the fuel to carry the fuel.

Thus even if there is capacity limits there may be reasons for loading less mass to reduce cost of a mission.

Fuel is not a significant mission cost.

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