7
$\begingroup$

The fuel for a Falcon 9 (SpaceX) costs around \$200,000 per launch, while the launch itself costs \$62,000,000. Safety precautions, rocket shell and rocket engines cost a lot. But why not fuel?

$\endgroup$

4 Answers 4

15
$\begingroup$

As noted by others, Methane, RP-1, LOX are manufactured in large scale across the US and much else of the world. (Manufactured may be the wrong word, perhaps produced is better).

It is functionally a commodity.

On the other hand, aerospace engineers get relatively high salaries. Space rated components, come from a world where you get one shot on a launch and it better work absolutely perfect. That sort of reliability is much more expensive, than simply processing LOX by compressing and cooling it.

SpaceX employs several thousand employees. The launches generate most of the money to fund their salaries. The reason the Space Shuttle cost so much was not the hardware per se but rather the 20+ thousand employees directly considered working to ensure each launch.

Lean implies smaller workforces.

Interesting anecdote to which I cannot find a reference. While a Falcon 9 launch lists at about \$62 million US, a launch for the Air Force costs almost \$100 million. Why? Because of additional paperwork that the Air Force requires. I.e. They spend almost \$40 million on paperwork! That is an amazing amount of paper.

Of course it is the cost of employee time to fill out, and process the paper, and the additional tasks it implies. Which should terrify you at how much work it must be to generate \$40 million worth of paperwork.

$\endgroup$
3
  • 3
    $\begingroup$ On the point about paperwork - applies to the aviation industry, so no surprise it would be equally so for the space industry. To help ensure that an aircraft is safe for flight, in order to be installed on an aircraft, every part must come with evidence of its fitness for use. That means traceability to its point of manufacture and proof of all necessary and appropriate inspection and/or testing. That's an expensive paper trail. $\endgroup$
    – Anthony X
    Commented Feb 11, 2018 at 16:14
  • 6
    $\begingroup$ There is also the matter of production volumes. Despite their complexity and the staggering amount of technology built into them, cars, computers, and cellphones these days are relatively inexpensive commodity items because they are manufactured in huge volumes. Aircraft, despite being "production" items are build in far smaller quantity, so development costs have to be amortized over far fewer units, making each unit sold more expensive. Rockets are made in even smaller quantities and have to be engineered and tested to higher standards. $\endgroup$
    – Anthony X
    Commented Feb 11, 2018 at 16:19
  • 1
    $\begingroup$ Similarly to what @AnthonyX is saying, QC costs are amortized also. If you want to test your fuel to make sure it meets spec, you only need to test each tanker car of it. A large volume of fuel covered by one set of tests. $\endgroup$ Commented Oct 31, 2023 at 15:25
14
$\begingroup$

Making fuels is a matter of relatively cheap bulk liquid processing from relatively cheap feed-stock. Yes RP-1 is more expensive than JET-A because more processing is needed and it's more specialized but it is still bulk liquid processing.

LOX is even cheaper because the feedstock is atmospheric air, there are just the processing costs.

Making aerospace components involves expensive processing of exotic materials. This processing often happens in low volume so there are relatively few economies of scale. The creation of a machined component often results in well over half of the material used ending up as scrap. For metallic components the scrap can be recycled of course but it still costs a bunch of money to take scrap and turn it back into usable material.

For comparison, 747 apparently costs somewhere around \$350,000,000 while a full fuel load for one is more like \$100,000. So the cost of a full tank of fuel being much smaller than the cost of the vehicle is hardly unique to space rockets.

The difference is that a 747 can be used tens of thousands of times. So over its lifetime the fuel costs more than the plane. Rockets on the other hand are typically only used once and when they can be reused refurbishment costs are a concern.

$\endgroup$
4
  • $\begingroup$ Fuel is only one part of the propellants, oxygen is needed too. But for production of liquid oxygen you don't need to buy raw materials, the air is for free. The liquid oxygen plant needs a lot of electrical energy. But when the air is liquified and sepearated by fractional distillation, the remaining liquid nitrogen and the noble gases like argon, neon and krypton could be sold. $\endgroup$
    – Uwe
    Commented Feb 10, 2018 at 21:50
  • $\begingroup$ Regarding your recent edit addition, I would think that scrap metal waste resulting from the manufacturing of custom components would fall more into the same category as fuel, i.e. there is a cost but relatively small in comparison to all of the bigger costs of building and launching a rocket. Not disagreeing and I could very well be wrong, but it might help to quantify how scrap metal costs is a standout compared to the other costs involved. And perhaps quantify exotic material costs if possible. Again not questioning, I know SpaceX has been dealing with skyrocketing (no pun) niobium prices. $\endgroup$ Commented Oct 30, 2023 at 17:43
  • $\begingroup$ Even in the case of metals, what a scrap merchant will pay you for your scrap is likely to be much lower than what you paid to acquire the material in the first place. $\endgroup$ Commented Oct 30, 2023 at 17:46
  • $\begingroup$ PeterGreen - no disagreement I'm just pointing out that I was reading it as if exotic materials used is above nearly every other cost of building and launching a rocket, even though I'm guessing that is not what you meant. I am guessing that your comparison in that regards is related just to material costs, i.e. exotic materials including losses from scrap exceeds the cost of rocket propellant. But then the total cost of a 747 is mentioned so I got a little lost in the comparisons. But I realize now that the 747 comparison shifted your answer to a separate point about total cost vs fuel cost. $\endgroup$ Commented Oct 30, 2023 at 18:08
4
$\begingroup$

What is cheaper: buying a new car every time or refilling the tank? Also it depends on the fuel: oxygen is pretty cheap compared to hydrogen (about 20 times more expensive). This is one of the reason that BFR is going to use methane and oxygen as fuel- they are both very cheap (also the abundance of carbon dioxide which is straightforward to convert to methane on Mars).

$\endgroup$
2
  • 2
    $\begingroup$ Methane is not abundant on Mars. It is present in trace amounts in the atmosphere and some venting from underground was detected. The idea is that it can be quite easily produced on Mars. With that caveat, you're right: ISRU (use of locally sourced propellant) is key to exploration of Mars. Because of the tyranny of rocket equation, it is very challenging to fly Earth-sourced propellant to Mars, meaning that any large rockets taking off from Mars will burn Martian propellant. Thus use of methane in BFR. $\endgroup$ Commented Feb 10, 2018 at 20:40
  • $\begingroup$ @LesserHedgehog You are correct sir. I edited in a correction. $\endgroup$
    – geoffc
    Commented Feb 11, 2018 at 0:24
2
$\begingroup$

A point that other answers have not covered: there aren't any better-yet-more-expensive fuels that don't have huge disadvantages. A chemical rocket engine is a fairly simple machine in principle (the details can get complicated) and the things you most want in a fuel/oxidiser combination for space launches are:

  • Lots of energy released in the combustion.
  • Low molecular weight of the combustion products.

Liquid hydrogen and liquid oxygen have the best performance in theory, but liquid hydrogen has very low density, making the tanks for it heavier. RP-1 or liquid methane give you much better tank weights, and you end up with a more effective rocket. Liquid fluorine might give you more energy than oxygen, but the safety problems would be horrible.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.