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Fuel is not cheap. Fuel is heavy and payload reduction is money lost.
by brmgb 7y ago
Fuel is not cheap. Fuel is heavy and payload reduction is money lost.
- inetknght 7y agoFuel is cheap. Spaceships are not.
- JshWright 7y agoFuel is very cheap. SpaceX has built their whole business around the idea that it's worth trading payload for re-usability.
- outworlder 7y agoFuel is cheap on a monetary basis. _Lifting_ that fuel is NOT CHEAP. See also, the rocket equation.
- ethbro 7y agoBut the primary cost of lifting fuel (if you have a reusable rocket) is fuel. Leaving us back at cheap. But we're essentially arguing whether max payload per launch or payload efficiency to orbit is more important.
- saagarjha 7y agoWith exponential compounding, I wouldn’t be so sure that it’s still cheap…
- CydeWeys 7y agoYeah, and with much higher required dv and more required stages this would be a huge problem. But we only need two stages to orbit when launching from Earth, so it's really not that big of a deal, and it turns out that optimizing for reusability ends up being a lot cheaper than optimizing for minimum fuel use. For example, it only costs $200k for a fuel load of Falcon 9 fuel. If you got rid of reusability you'd need less fuel and could save tens of thousands of dollars ... but at the cost of needing to build a new $54M spacecraft with each launch. Clearly that trade-off isn't worth it. So yes, fuel is cheap.
- Retric 7y agoFuel becomes more expensive on reusable spacecraft. Granted, the first pound of fuel is cheap, but the costs keep rising. With one and done you have a larger mass fraction to work with. Reusable spacecraft operate on much tighter constraints. Every single wasted pound in Space X’s design likely costs them 100’s of thousands of dollars in lost profit over time.
- Retric 7y agoNot sure what’s to disagree with about that: “The reusable Falcon 9’s performance to GTO is listed at 5,500 kilograms. The same rocket in fully expendable version can lift 50 percent more payload — 8,300 kilograms. For the Falcon Heavy, the performance to GEO is about 2.8x that of the reusable version” https://spacenews.com/spacexs-new-price-chart-illustrates-performance-cost-of-reusability/ https://spacenews.com/spacexs-new-price-chart-illustrates-pe... Reusable means cost savings, but it has a dramatic reduction in cargo capacity. This means more trips to get the same mass into orbit, which means mire fuel directly used and every extra lb in the design is then carried up multiple times while further requiring more trips.
- ncmncm 7y agoWhich trips each cost much less because you don't have to build another rocket to do each with. Or, equivalently, in one trip with a bigger rocket you have left over from another launch, because you didn't ditch it.
- Retric 7y agoThat’s great if you’re transporting large numbers of the same thing like star link satellites. However, many payloads are worth sacrificing the first stage. Just look through the “No attempt“ missions in 2018 for some of the reasons why: https://en.m.wikipedia.org/wiki/List_of_Falcon_9_and_Falcon_Heavy_launches https://en.m.wikipedia.org/wiki/List_of_Falcon_9_and_Falcon_... Which again demonstrates reusability is really expensive, though clearly not always as expensive as a new rocket.
- brmgb 7y agoSpaceX has built part of their business around the idea that it's worth trading a moderate amount of payload for re-usability as long as they can still reach the orbit their customers care about and it was considered an extremely risky bet before they made it routine. It doesn't make fuel cheap, let alone very cheap. Actually another significant part of SpaceX business is modern engineering and modern mean of production. They used to launch without recoverability for some high orbit payloads and they were competitively priced for that too.
- DennisP 7y agoMusk has said the cost of the methane for one Starship/Super Heavy launch will be about $1 million.
- Agathos 7y agoFuel on the ground is cheap. Halfway to orbit, nothing is cheap.
- cameronbrown 7y agoSpeaking relatively here.. spaceships are still more expensive.