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Comment by jillesvangurp | Hacker News Reader

Methane is about 900-1500$ / ton. About 1000 tons is used for the launch in addition to 3600 tons of lox. That should be a bit cheaper than methane per ton. Ballpark, the propellant might cost around 2M$.

A modern airliner on a long flight might burn around 80 tons of kerosene. It's slightly cheaper than methane. Call it 75-80K$.

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That's $7 of fuel per pound of payload, that is not bad at all.

Indeed. You sometime see an argument that launch to space is expensive because of the propellant and therefore energy required. And as you note this argument is utterly wrong.

not sure how anyone can miss the "throwing away the airplane" part as being the cost driver.

It's the same cognitive error as thinking nuclear energy must be cheap because the fuel is cheap.

>And as you note this argument is utterly wrong.

Am I mistaken, or are there distance/payload combinations for which Starship is cheaper per pound on a point-to-point basis than air transport, even setting aside 30 minutes versus 12 hours? Isn't that the non-intuitive outcome of ballistic trajectories?

No. But it gets within an order of magnitude, which is remarkable. Economy class on starship could be priced similar to first class tickets on transoceanic flights.

Is the $1000/ton a law a physics, or could that ever possibly scale up and come down an order of magnitude?

There are no dollars in the laws of physics. It's connected ultimately to productivity of all the activities involved, and there's no obvious upper bound to productivity.

There's the rocket equation.

https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation

Which doesn't have dollars anywhere in it.

The point of the rocket equation is there are hard physical limits on what rockets can do, and dollars won't change it.

That's nice. It doesn't imply a lower bound for costs, just of ratios of costs.

Just the current market price for fossil methane, which of course goes up and down. But I'm assuming SpaceX gets their methane on the open market.

It's quite possible that SpaceX has access to some cheaper methane source. Texas produces a lot of it.

And SpaceX has speculated about eventually switching to some renewable source by e.g. synthesizing methane. In which case that would boil down to cost of electricity and carbon. I don't see that becoming cheaper short term but that could happen long term.

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