The Falcon 9 is ~500 tons of propellant for 25 tons to LEO. An A380 carries ~250 tons of fuel. In the Falcon 9 number the liquid oxygen is included. The RP-1 is a pretty much a cleaner diesel or jet fuel.

The cost is like $1500 to $2000 per ton so like $500 000 to $1 000 000 in fuel costs for a launch.

Fuel costs are still trivial compared to building and operating the rocket and is where huge reductions are possible.

Your argument is obviously wrong. If that were the case, all launch systems would have the same cost per kg, since they all are operating on the same planet with the same gravity.

But in fact, the minimum cost imposed by gravity (the energy needed to get into space) is incredibly low. The minimum fuel cost is a very small fraction of the cost of launching with current launch vehicles. The costs come from expendability and manufacturing and non-fuel operating costs. None of these are dictated by gravity.

There is a cost in mass. Rockets today are essentially a giant fuel tank with a few engines connected to one side and cargo connected to the other side.

Every kg of fuel is a kg of cargo you can’t launch. That’s the cost.

None of that justifies claiming the cost is due to gravity. The problem of getting to space is obviously affected by gravity, but the cost is dictated by other considerations. It's not like "oh well, gravity, we might as well give up because it's not possible to do much better."

> None of that justifies claiming the cost is due to gravity.

It scales a lot with gravity. Compare the cost of a vehicle capable of reaching lunar orbit (e.g. the Eagle), with the cost of getting humans into Earth orbit (e.g. the Mercury-Atlas). And the Eagle carried two people.

Sure, but once you're in space things can become easier, with high Isp engines and in situ propellant production. It's not necessarily all chemical rockets with fuel lifted from Earth.

> None of that justifies claiming the cost is due to gravity.

Where do you suppose the need for so much energy comes from?

Congressional mandates forcing NASA to use Space Shuttle components for the SLS that are de facto non-competitive, single-source requirements assuring contracts to existing Shuttle suppliers is contributing significantly to the costs.

For example, the NASA contract to Aerojet Rocketdyne to manufacture RS-25 engines is costing $146 million per engine. Each SLS launch will toss four of these engines in the ocean for a total cost $580 million. And that's just the engines of the core stage. For the cost of a single engine, they could have instead purchased an entire Falcon Heavy launch, which has two-thirds of the SLS lift capacity (and has to obey the same laws of physics as SLS).

SLS is the price NASA had to pay to get Congress off its back.

Why would the US congress mandate stuff like this?

The more dollars and jobs you can claim you brought to your district during the next election, the better.

This isn't just a NASA thing, a NASA contract is probably pretty small compared to getting a new military base, or keeping one open that the military wants to close.

Because US congress is made up of elected representatives, and each representative is incentivized to do so by the desire for re-election.

Because it benefits them (in kickbacks from contractors, for example) and because they can get away with it.

Having a well functioning space program? Doesn't benefit them much or at all.

Ultimately, it's because voters don't call them on their BS. If you've been a NASA fan, encouraging NASA funding regardless of what it's for, you're part of this problem.

I'm not an US citizen. I can't call out US politicians on anything because I don't have a vote.

It's more that the cost in money doesn't come from the cost in energy.

Why do you think the cost of launch is due to the cost of energy?

Why do they launch from sea level instead of a high elevation?

Mostly because it's nice to have an uninhabited area downrange of the pad.

The benefit of launching from altitude would not be the potential energy, but the lower air pressure and density. The first would enable rocket engines to operate at higher expansion ratio, and the second would reduce aerodynamic forces. The benefit is apparently not large enough to justify the difficulty of operating on a mountain.

The goal of the rocket is to get the payload high enough to be in space AND fast enough to be in orbit. It's the later that takes most of the fuel, IIUC.

Why do you think that would help?

I can imagine two different answers to that and depending on which one you tend to think more there are two different answers to your question.

If you are thinking: space is high up therefore the higher we start the easier we will get there.

The problem with this is that getting into outer space is not that hard, staying there is the hard bit. The international space station orbits about 408km away from the surface of the earth. That is not a long distance. If you would have a car which can travel the same speed a car can usually travel but straight up you could reach that altitude in about 4 hour easy driving.

What is important is what would happen after you reach that elevation and turn off the engine of your car. If you have seen astronauts serenly drifting in space, you might expect that your imaginary car would do the same. But that is not what would happen. You would see that your car starts falling and rapidly!

In fact there is a word for such a flight path. It is called a suborbital space flight. Space flight because it went to space, but “sub” orbital because it lacked something to stay in orbit.

What is that something it lacked? Why do the astronauts float gracefully while your car plumets? The trick is that the astronauts plumet too! They are constantly falling back towards earth, they just go so fast sideways that the earth rolls out from under them. In fact that is what an orbit is. You are falling around the earth with a very high sideways speed.

In essence staying in space equals being in orbit which further equals going very fast.

So now you can see that being high is not the hard bit of staying in space. Flying as fast as a bullet is the hard bit, and of course starting from high won’t help with that.

But! You might think a different thing why launching from a high elevation might help. Maybe you already know that staying in space == going fast. So you are thinking: what hinders us from going fast? The drag of our atmosphere! If we would launch from high there would be less atmosphere around us, thus there would be less drag, thus we wouldn’t waste so much energy to fight it. And you would be right! If you could launch from a high elevation you could spare some energy because there the atmosphere is thinner. But when you run the numbers you see that this is a very small percentage of your total energy expenditure. Mostly because our rockets fly through the dense part of our atmosphere relatively quickly wasting only a little energy to fight drag. Launching from a high elevation would come with it’s own set of challenges of course and wouldn’t help that much relatively.

So depending on which thing you were thinking about you have an answer. Hope it explained the problem better. If you have any more questions about any of the details let me know and I will try my best to explain.

Also sorry for answering this long a seemingly simple question. Would love to answer shorter, but you know it is “rocket science”. ;)

My thought was that the first mile up would be the hardest to get through because of being closest to the Earth's center. And isn't it something like 1% of the distance that they need to reach for "cheap" horizontal acceleration?

> If you could launch from a high elevation you could spare some energy because there the atmosphere is thinner.

Reminds me of Eve on Kerbal Space Program. Gravity so high and atmosphere so thick that I had to use a helicopter contraption to lift the spacecraft to the highest possible altitude in order to get the rocket to even make it to space to say nothing of the absurd delta-V needed to actually inject into orbit.

My guys were stuck on that planet for a long time...

Very interesting! Such a thoughtful and thorough response. Thank you.

they do have air to orbit launches fwiw but musk is not a fan

How is it wrong? Everything I've ever read about the subject says that because of the rocket equation you need massive amounts of fuel to lift up the fuel itself and the payload to get off the ground and into orbit. In order to burn that fuel, you need complex multistage rockets which require expensive materials and precision manufacturing.

Of course it's expensive. Surely if these things were built in space instead engineers would be able to build simpler, cheaper spacecrafts.

Rockets are not expensive because they use lots of fuel. Sit down and actually compute how much propellant is needed, and how much it costs. It's CHEAP, especially if you use LOX + hydrocarbons (as Falcon 9 and Heavy do).

The actual amount of energy needed to reach LEO is about the same as the amount of energy needed to send the same mass to New Zealand from the US by airliner.

The reason launch is expensive is because the launchers were thrown away. SpaceX radically reduced the cost by reusing the first stage multiple times. And there's more juice to be squeezed from that lemon, as the second stage is still being expended.

> The actual amount of energy needed to reach LEO is about the same as the amount of energy needed to send the same mass to New Zealand from the US by airliner.

Yeah but rockets use a lot more fuel mass compared to aircraft whose engines are airbreathing. Rocket engines need to carry their own oxygen in the fuel tanks and are less efficient as a result. Surely fuel costs are no trivial concern.

> The reason launch is expensive is because the launchers were thrown away.

Well I agree that it's stupid to just throw away the rockets into the ocean but I thought NASA just didn't have the capability to reuse them. A comment below says the US congress forced them to reuse old parts which makes no sense to me.

Are you blaming the cost on liquid oxygen? Sorry, but LOX is very cheap. It's the second cheapest industrial liquid, after water (or water containing cheap dissolved substances). The cost of the LOX is small compared to the cost of the fuel that it combusts with.

When people have looked at airbreathing launchers, they quickly discover that the designs optimize to 0% airbreathing, 100% rocket. LOX being so cheap and dense is a big part of that.

Indeed NASA doesn't have the means to reuse them, which makes it sad that NASA is being forced to play to their own incompetence in the SLS program. NASA originally wanted to get back to the moon with commercial launchers.

That's exactly pfdietz's complaint. NASA employs the same types of humans SpaceX does. If reusability was a design constraint they would have solved it like SpaceX did. But they didn't consider it a priority or even a goal to make regular moon travel feasible so they continue throwing away billions with such limited impact.

> they didn't consider it a priority or even a goal to make regular moon travel feasible

That's insane. Isn't it literally their mission to advance spaceflight technology?

I assumed there was a good reason they were not reusing the rockets. Are you seriously telling me it's due to politics and corruption?

NASA was always a public works program, that's one of the reasons LBJ was its biggest high level booster back in the 1960s, it had an explicit mission to uplift the US South. Per the guy who invented the reentry vehicle, the lack of one or more staging space stations along the way for Apollo came from that spending "a billion dollars" more in Texas, call that $10 billion today.

After the end of the Apollo Project, "politics and corruption" were all that was left, as should be obvious from the lethally ridiculous design of the Space Shuttle.

Wow that is disappointing.

> as should be obvious from the lethally ridiculous design of the Space Shuttle

Can you elaborate? Everyone here is calling it stupid but I don't really understand why. I thought it was retired due to expenses, NASA defunding or something like that.

As a general principle, the Space Shuttle program was massively capital constrained, so many trade-offs were made that compromised safety and operating expenses. I suppose the latter helped in limiting the number of flights, but then again half the fleet and their crews were lost.

Perhaps start with what killed two shuttles and their crews? Besides no provisions for escape unlike all other "capsule" based craft, solid rockets are _dangerous_ because you can't turn them off, whereas liquid fuel rockets will effectively turn themselves off in many disaster scenarios.

So for a get me out of here tower escape system a solid rocket makes a lot of sense, see also their use in ejection seats. But mounting some number of them (more than one unless used alone because you need symmetrical thrust) on the sides of your system means they must work perfectly every time.

The reentry heat shield protections which along with the wings etc. came from a requirement the Air Force says they never really wanted or needed, a single polar orbit mission returning to the launch location which thus required a lot of maneuvering in the atmosphere because the Earth turned while it was up there resulted in the infamously fragile tiles and some more refractory stuff for hotter locations (and eventually a bunch of tiles in a cooler location were replaced by something else).

Rear end heat shields are protected during the launch of a capsule, it's all hanging out there with the Shuttle. Change the foam and larger parts of it may break off, hit, and fatally compromise a part of the insulation system.

Now going from personal worry points and speculation:

The Space Shuttle Main Engines (SSMEs) are for institutional reasons extremely high performance and required a rebuild after every mission, so the SLS "throw away half a billion worth of engines every flight" would need to subtract that labor and parts.

That said, they were fired up and the SRBs not lit until it was clear the SSMEs were running fine, that resulted in three legit aborts and two from faulty sensors. Two failures after launch, split between both causes, noting catastrophic or mission endangering. But, still, you have all their complexity and SRBs.

Landing ... well, that's another thing that's more complex or at least different although landing in the sea also has its issues: https://en.wikipedia.org/wiki/Mercury-Redstone_4

It's a hell of a lot more complicated aerodynamic body/system than a cylindrical rocket and capsule system so that work was harder and more error prone. IBM Federal Systems modified a lot of code between the first and second launches, and caught an introduced error that would have released just one SRB. There's a 1984 CACM issue devoted to all this https://dl.acm.org/toc/cacm/1984/27/9 and is now free to read online or download, I highly recommend it. A lot of programmers outside of that world were concerned the code wouldn't be up to snuff, what you'll read in those articles explains how they pulled it off.

And, again, no escape systems. Fly enough times and things go wrong, the Shuttle compounded this by massively increasing complexity for very little gain.

Rocket books are written by scientists, not economists or MBAs. Elon Musk's major innovation with SpaceX was to look at it from a business & economic angle rather than the angle of scientists or millitary industrial complex which thrives on Cost Plus contracts.

It turns out fuel cost rarely exceeds 10% of the cost of launch even with the tyranny of rocket equation. Traditional expendable rockets (including SLS) essentially throw away 90% of the cost of each launch - hence the push by SpaceX to some of the fuel to try and land the first stage.

I initially thought rockets were not reusable because it was literally impossible to reuse them. I thought the launch and reentry damaged them beyond repair. Reentry modules require huge heat shields to protect the craft from being destroyed by atmospheric ablation. How is it possible for these things to launch into high altitudes and not only survive reentry but land safely?

It does sound kind of stupid to just let the engines and stages free fall into the ocean now that you mentioned it. I'm not sure how advanced Musk's rockets are but if they can land safely after being staged then that's an amazing innovation. Why isn't NASA all over this if it's so revolutionary?

They are currently reusing the first stage which is sub orbital - ie. Much slower, less re-entry forces. Still a major economic benefit for overall rocket cost. That said, Starship is planned to land from orbit & be reusable - let's see.

NASA is all over it from what I see - SpaceX has essentially captured virtually all of the commercial launch market and a good chunk of defence and science markets except for hyper specialized requirements or non-US defence launches.

I however don't see how NASA could have developed it given the politics involved with its funding essentially incentives Project thinking over Product thinking - I actually use that as an example when I contrast Project vs Product at work. SpaceX had to blow a couple of dozen rockets AFAIK to get to a stage where they land reliably - doubt NASA could have justified that to the US Congress. NASA's funding incentives encourage a risk averse approach to engineering ever since the very high profile failures in space shuttle and the early Mars missions. Witness how the Mars helicopter was rated for a low single digit of missions and has now completed a few dozens.

> Much slower, less re-entry forces.

I should point out it isn't forces that matter for entry from orbital speed, it's heating.

Spacecraft that require protection from re-entry are going far, far faster than first stages, so slowing them down using atmospheric friction creates a lot of heat. The Falcon first stage gets to about 8,000 kph and reaches over 100 km before it starts coming down, not high or fast enough to create the stresses an orbital re-rentry vehicle sees. The other key to reusability is having enough leftover fuel to land, control surfaces and restartable engines. Restartable engines weren't proven to work until the Gemini program in the mid-1960s, if I remember right; I'm sure the Saturn rockets was well into development by that time and the engineering costs to make major changes the lower stages were too great. Sometimes government gets set upon a course and it's very hard to redirect it; that's why innovators like Space-X are so valuable.

There were quite a few proposals for how to reuse rockets stages - actually you can see more the farther you go.

Certainly it could have been partially due to not yet having enough experience with many real world launches.

But at the same time a lot of the funding was comming from ICBM programs that don't really care for reuse by design & from army and a high profile space race with USSR. That kinda favored the expensive get-it-done fast expensive MVP instead of a more complex reusable solution that could be much cheaper in the long run.

And then the status quo took root & reusable rocket proponens were no longer taken seriously because - what were they thinkig, this is how we have always been doing it!

"And then the status quo took root & reusable rocket proponens were no longer taken seriously because - what were they thinkig, this is how we have always been doing it!"

Disagree as someone who as a kid watched this happen in real time. The Saturn V follow on was always planed to be reusable, with a huge first stage booster that was something of a bigger brother of the stage that would make it to orbit. NASA was starved for capital after Apollo and this resulted in the horribly deadly and very expensive to operate kludge of the eventual Space Shuttle.

It is not wrong, you can reduce the cost but it will never be economical simply due to the gravity well.

> the minimum cost imposed by gravity (the energy needed to get into space) is incredibly low.

This is straight up false.

Well it's technically correct. To get a 100kg object from the surface to a 100km Karman line needs about 30kWh of power. That's the same order of magnitude as travelling 100km sideways in an electric vehicle.

At 20c/kWh it would cost $100 to lift a 2 ton car and 4 occupants into space, or $100 each to get to the c. 400km altitude of the ISS.

Of course to stay in space requires far more energy as you also have to go sideways, fast. Very Fast.

But it's still pretty low. Sticking 1kg into Geostationary Orbit and keeping it there would take about 15kWh. A 2 ton vehicle with 4 passengers at 20c/kWh would be $1500 each.

Of course we lack a practical way of doing this other than with rockets, and thus enter the tyranny of the rocket equation. But the fuel cost is still far lower than the cost of the entire shuttle or apollo system, as shown by the efficiency of SpaceX -- fuel costs of $20/kg to LEO, or $1500 for a typical adult.

You're comparing rocket engines designed to operate in a vacuum to electric vehicles designed to operate on the ground. Rocket engines need a lot more fuel to generate that amount of power.

No, you're comparing the method of applying the energy required, which is painfully inefficient (rockets), to the energy actually required.

But I did touch on that in the last paragraph -- the energy required on a rocket to get into LEO is $20/kg, or $2k/person. It's a tiny amount of the total cost of launch.

Rocket engines are actually extraordinarily efficient. They're the most efficient heat engines we have. More than 90% of the thermal energy produced in the thrust chamber is converted to kinetic energy of the exhaust jet (especially in high expansion ratio engines). The fraction of chemical energy of the propellants of a launch vehicle that ends up in the kinetic energy of the final stage is surprisingly high (well, it was to me, initially.)

They are not efficient at doing their job (moving things upwards), hence we don't use them to get from the bottom of a skyscraper to the top. They have to carry their entire mass of fuel with them.

A large crane is far more efficient at lifting items.

But even if you accept you have to use a rocket, the cost of the fuel is trivial compared with the cost of launch.

Of course they are not efficient for that use case. That use case is not the same as the use case of getting to orbit. When the delta-V involved is similar to the exhaust velocity of the rocket the overall efficiency goes way up.

If you could vary the exhaust velocity of a rocket continuously, so it was equal to the total delta-V so far, the efficiency of converting jet kinetic energy to vehicle energy would be 100%, as the jet would be left stationary in the reference frame of the launcher. (This ignores gravitational potential energy and also that the mass ratio would diverge to infinity at zero velocity, but never mind that.) In practice, using a lower Isp first stage and a higher Isp upper stage partially implements this, and the overall efficiency isn't too bad.

kWH of power and its cost does not translate here, your kWh of power does not have any specific impulse.

Space elevators and Lofstrom loops also do not have Isp (or have very, very poor Isp, if you're treating the Earth as reaction mass...).

kWh is a measure of energy, not power. And specific impulse is only of relevance to rockets, not to the amount of energy required to lift.

The problem in space access isn't an energy problem, it's a method problem.

Nope, you're completely wrong. Do the math. Propellant cost is a tiny fraction of the cost of a launch, even on the partially reusable Falcons.

That fraction is still larger than the economical utilization of space.

Think about how little propellant it takes to move products on Earth. And that's not even counting for the fact that transport vehicles on Earth runs a heavy percentage of its life time while a rocket does not do that. Even Falcons spend most of their time getting ready or recycled and not on an ascend or descend trajectory.

Any real trade will not happen at these gravity tax rates.

> That fraction is still larger than the economical utilization of space.

What does this sentence even MEAN? There are economical uses of space at today's launch costs. There would be even more such uses if launch costs were a few times the cost of propellant, as the cost of air travel is.

I get the feeling you are not thinking clearly on this subject.

If launch cost were few times the cost of propellant, what economic activities become feasible in space?

Sending tourists? Sure, tourists are already up there and it costs even less propellant to drop to the ocean floor but not many people/business seemed to be doing that. Maybe with the exception of oil platforms.

Speaking of which, what oil platform will be of space? Even a floating city in space that is purely afforded by the tourist spending generates no true economic value up there - all of it is being essentially propped up by the ground. What economic incentive are there?

The only way out is to manufacture IN SITU, sourcing from locally or gravitationally less burdensome locations, like the asteroid belt. It takes less deltaV to go to the asteroid belt from LEO than it takes to get to LEO from the ground.

Trust me I've been thinking about this plenty - though probably not to any use.

A tourism analogue could be Antarctica rather than the sea floor.

Antarctica is also an analogue for manned science. Reduce costs enough and it makes sense to put people in space rather than do things remotely. There's a base at the South Pole. The cost to get there would be similar to the cost of getting to LEO, in this few-times-propellant cost scenario. Yet no one talks about automating that base, it just doesn't pencil out.

Lower launch costs will enable much larger satellites to be built, with much larger apertures of antennas and optics, and with higher bandwidth, or with much less focus on expensive mass optimization. We could see satellites in high earth orbit being maintained manually.

At a few tens of dollars per kilogram, space disposal of nuclear waste starts to make sense.

I can recommend Terra Invicta as a very realistic grand strategy game demonstrating it nicely - you will never lift the thousands of tons needed for just a single ship in your fleet to protect the Mother Earth from aggressive extraterrestrial invasion.

But plop a few mining complexes (each couple dozen tons IIRC) on the Moon or near Earth asteroid and the tables turn quite quickly. As now you can build more station from extraterrestrial resources, which mine said resources and it goes from there. :-)

But a 747 needs continued fuel to keep going whereas once on target a spacecraft can use its initial velocity to travel much much further.