SpaceX going it alone to harvest water

[OTV Booster]

This is an outgrowth of https://forum.nasaspaceflight.com/index.php?topic=50806.msg2738114#msg2738114
where harvesting water for propellant struck me as reason enough for SpaceX to continue their lunar endeavors even if they were cut from the Artemis program. ISTM the issue was far enough removed from the discussions intent that it warranted its own discussion.

The topic says it all. Is a lunar mission in SpaceX's long term interest? Does it further their Mars aspirations?

[InterestedEngineer]

This is an outgrowth of https://forum.nasaspaceflight.com/index.php?topic=50806.msg2738114#msg2738114
where harvesting water for propellant struck me as reason enough for SpaceX to continue their lunar endeavors even if they were cut from the Artemis program. ISTM the issue was far enough removed from the discussions intent that it warranted its own discussion.

The topic says it all. Is a lunar mission in SpaceX's long term interest? Does it further their Mars aspirations?

Make it make economic sense.

At $20/kg to LEO for O2 (which is $4M/launch, so a plausible estimate in the long run), would it make sense to mine O2 on the moon and somehow get it into LEO where the primary expenditure would be?

I doubt it.

If there are 1000 flights that need 1000t of LOX per year (mix of Mars and Moon and outer planet destinations) that's 1M tons of LOX in LEO per year which is a cost of $20B/year.

You'd have to not only be able to set up a mine for about 3x the yearly cost (6 year amortization), or $60B, you'd have to deliver LOX to LEO for about $10/kg to match that 6 year amortization.

The deltaV from lunar polar surface to LEO is 5.7km/sec.   that's a mass ratio of 5 for a Raptor style engine.  I note this is about 60% of the deltaV to come from earth surface.  Are you then saving anything?   

Where is the carbon and hydrogen going to come from to get that LOX into LEO?

The current cost of LOX is $0.25 per kg on Earth.  If it's 10x that on the moon and you have to expend 5x that to get it to LEO then it's now $12.5/kg, which makes no economic sense.

It'll be far cheaper to optimize the cost to LEO to get to $10/kg than to implement the very complex process of getting LOX from the surface of the moon to LEO.

Not to mention that anything coming from Luna can effectively be turned into a weapon against Earth since it's almost all downhill.  (An entire book was written on this topic).

The only way LOX production makes sense on the Moon is to directly support a Moon colony, in an identical manner to the proposals for Mars - and mostly for "going home".

[InterestedEngineer]

it'd be cheaper to find a comet that you can capture around Earth and mine it in the orbit which you wish to expend it.

[Vultur]

Moon stuff may be useful for SpaceX's ambitions, if those include "be overall dominant in the space industry".

I don't think it's useful for Mars, specifically, though. Lunar propellant is probably not useful for anything except leaving the Moon - it's probably a bit of a catch-22. (If launch costs are expensive, there's not a large enough market in space to justify setting up the lunar propellant infrastructure. If launch costs are cheap, you can launch propellant from Earth cheaply.)

Until you are approaching the theoretical/physical limits* it's probably more useful to spend the huge amount it'd cost to build the lunar propellant infrastructure on improving your Earth launch costs instead - since you can use that system to launch things other than propellant, too. Also, reducing launch costs is a natural result of optimizing your existing launch system, while the Moon propellant stuff is totally separate

*Which are probably absurdly low. With a very large number of reuses of a large (Starship - scale) vehicle, manufacturing cost per kg is amortized down to nearly nothing. e.g. 1000 flights of a 100,000kg to orbit vehicle... 100,000,000 kg over the lifetime of the vehicle. If the vehicle costs $200M then the vehicle's part of the launch cost is just $2/kg. Propellant cost is not much either if you use cheap fuels like methane/LOx.

[meekGee]

Yup there's no point where Lunar propellant makes sense outside of leaving Luna, and even that's a maybe.

In order to build a Lunar mining base you need SH/SS running full time, and when that happens Earth-sourced propellant will gain even more of an advantage, since once you take away transportation cost, obviously the sourcing itself is a lot cheaper on Earth.

[volker2020]

This is an outgrowth of https://forum.nasaspaceflight.com/index.php?topic=50806.msg2738114#msg2738114
where harvesting water for propellant struck me as reason enough for SpaceX to continue their lunar endeavors even if they were cut from the Artemis program. ISTM the issue was far enough removed from the discussions intent that it warranted its own discussion.

The topic says it all. Is a lunar mission in SpaceX's long term interest? Does it further their Mars aspirations?

Make it make economic sense.

...

The deltaV from lunar polar surface to LEO is 5.7km/sec.   that's a mass ratio of 5 for a Raptor style engine.  I note this is about 60% of the deltaV to come from earth surface.  Are you then saving anything?   

...

While I am inclined to agree about the economics, that at least this point makes no sense, I find a flaw in your argumentation. If you would produce O² on the moon, you would not send it to LEO but more likely send it on a much higher energy rich parking orbit, gaining deltaV in the process and make it much more financial viable. The ratio does change quite a bit.

[meekGee]

This is an outgrowth of https://forum.nasaspaceflight.com/index.php?topic=50806.msg2738114#msg2738114
where harvesting water for propellant struck me as reason enough for SpaceX to continue their lunar endeavors even if they were cut from the Artemis program. ISTM the issue was far enough removed from the discussions intent that it warranted its own discussion.

The topic says it all. Is a lunar mission in SpaceX's long term interest? Does it further their Mars aspirations?

Make it make economic sense.

...

The deltaV from lunar polar surface to LEO is 5.7km/sec.   that's a mass ratio of 5 for a Raptor style engine.  I note this is about 60% of the deltaV to come from earth surface.  Are you then saving anything?   

...

While I am inclined to agree about the economics, that at least this point makes no sense, I find a flaw in your argumentation. If you would produce O² on the moon, you would not send it to LEO but more likely send it on a much higher energy rich parking orbit, gaining deltaV in the process and make it much more financial viable. The ratio does change quite a bit.

True.

But consider that sourcing o2 on earth is free.
Sourcing it on the moon is very difficult.

That's true not only for the O2 you're taking to orbit, but also for the O2 you use to launch it, and the O2 you use to land the empties back.

And yes, rail gun, sure.  So the power to build and operate the rail gun.  And the power to mine the rocks and extract thw oxygen.

And meanwhile earth launch costs approach propellant costs, the bulk of which is O2, which literally grows on trees down here.

If (IF) there's an inflection point, it lies sooo far in the future that you can't discount high ISP drives anymore.

[TrevorMonty]

To benefit from lunar propellant really need hydrolox  US. For SpaceX just not an option.

Blue have design their LV architecture with moon as target hence choice of hydrolox for US, lander and transporter vehicle.

What would be of benefit for Mars transport is extracting O2 or water from Demios or Phobos.
Having some fuel in orbit would make return trip to earth easier.

[redneck]

I don't see SpaceX getting into the Lunar water business at scale. I do see some entrepreneur developing a cost effective extraction method at some point that changes the trades. I don't see Lunar materials making sense in LEO. High Lunar orbit as a provisioning stop on the way elsewhere seems more likely, eventually.

It is not only the cost of Earth launch to LEO with a mature industry. It is also the hassle and pushback from those that dislike spaceflight/Musk/progress/freedom/The US/name it. There are already those that think spaceflight will doom the planet with damage to the atmosphere. It being nearly impossible to reason people out of a position they weren't reasoned into in the first place.

[OTV Booster]

The broad sweep of a concept is in some posts that I plan to bring over later today. In the meantime I'm working on a phone and quoting is beyond painful.

A fast summary:

Yes, it makes absolutely no sense to use lunar propellant ISRU for mars transit in the short term. The mining will have to start small as the techniques are learned and the number of mars bound ships will be too few to justify a massive R&D program.

As production ramps up use the water for moon-earth return and maybe powering lunar facilities and ground transport during the two weeks of dark. As output grows so will the mars fleet.

Some assumptions about mars traffic. The first mission will have two crewed ships of 12 each. Each 12 crew will need three cargo ships. That's eight ships. Further assume that each ship will need three tanker loads for 24 tankers. There will probably also be a depot or two until Mars ISRU is up and running but that is so speculative we should not add it in but need to take note that the propellant needs will most likely be higher for early missions.

Assume the number of crew doubles each synod and the packing density increase 50% until it there are 100 people per ship and ultimately the musk goal of 1000 ships full of people is reached. If the crew/cargo ratio holds steady that's 9333 ships going to mars each synod requiring 25,000 28,000 tanker loads. The numbers are beyond soft but they get the magnitude of the problem across.

The target would indeed be a higher energy orbit than LEO. L1 suggests itself. Rather than crack the water on the moon, send it to L1 for cracking. The thermal environment is benign for cryo and PV gets uninterrupted solar access except during an occasional equinox. Ship sequestered CO2 up from earth. Think of launch cost as a disposal fee.

A lunar rail gun came to mind but Robobeat suggested a sling. Velocity would be low at L1 and a plane change to a halo orbit inexpensive. A sling launch calls for a counter mass to be slung in the opposite direction, which raised a question in my mind of the possibility of a twofer. One direct from the pole and one over far side with some additional boost needed.

Musk Mars transit numbers are probably akin to Must time projections but the number will still be high. At minimum the natural gas quantities needed will be market distorting.

Long long term, even lunar water may not be enough but we can revisit the question in 50 years and discuss Jovian scoop ships.


Edit: corrected a number.

[TrevorMonty]

 There are already those that think spaceflight will doom the planet with damage to the atmosphere. It being nearly impossible to reason people out of a position they weren't reasoned into in the first place.

Damage to upper atmosphere from spaceflight is quite realistic fear.especially when launching 100s of SHLVs every year. Its big unknown that needs to be monitored.

[OTV Booster]

The logistics of connecting a LOX supply line to a lander on the lunar or Martian surface isn’t practical.

Why?

[crandles57]

Probably a silly question, but from low lunar orbit, can you do a Earth gravity assist to help with getting to a trans mars injection orbit?

Probably even sillier, is there a size of comet that is light enough to be able to slowly steer into and maintain a mars cycler obit perhaps with huge solar sails (that also reduce solar induced melting). Could this also be big enough to be able to build a base on it, 'land' and refuel hydrolox rockets during the journey? Does all the ice disappear too quickly?

Useful radiation protection and propellant supply or just way too big a task for centuries?

[InterestedEngineer]

Probably a silly question, but from low lunar orbit, can you do a Earth gravity assist to help with getting to a trans mars injection orbit?

not a gravity assist, but an oberth burn.  Gravity assist is when you entire from outside earth's Sphere of Influence.  Problem is your cargo is coming from Earth and all that deltaV you took to get to the moon you could have used to go to Mars directly (it's really not that much different, in fact lunar surface is MORE deltaV than Mars surface).

If you wanted to get to Mars REALLY FAST you want to refuel in an elliptical orbit.  So from Luna you are braking a whole bunch of LOX to go from circular to elliptical.

If you could somehow use a magnetic or slingshot launch to get directly from Moon to elliptical orbit with Earth you could set up a way station for refueling.  Problem is the fuel is scattered along that elliptical orbit, you want it concentrated so you can rendezvous with it.

Go play KSP for a while you'll get an intuition for these orbital mechanics.

Probably even sillier, is there a size of comet that is light enough to be able to slowly steer into and maintain a mars cycler obit perhaps with huge solar sails (that also reduce solar induced melting). Could this also be big enough to be able to build a base on it, 'land' and refuel hydrolox rockets during the journey? Does all the ice disappear too quickly?

Useful radiation protection and propellant supply or just way too big a task for centuries?

That's not a bad idea really.   But getting the comet into a high earth orbit might be easier.   It doesn't need to be hydrolox, you can use Raptors - comets have plenty of carbon and water.   This would be a fun topic in the Advanced Topics section.

[Mythundare]

To benefit from lunar propellant really need hydrolox  US. For SpaceX just not an option.

I mean, at a 3.6:1 fuel ratio, oxygen is still 78% of the fuel mass for methalox. You don't need to be producing methane for it to be useful. It should enable the HLS to go LEO -> lunar surface -> LEO propulsively (refuelling with methane and oxygen in LEO, and only oxygen on the lunar surface).

Or LEO -> lunar surface -> earth surface, with the heat shield. That would interfere with the mid-ship landing engines, but in a scenario where you have the infrastructure to harvest oxygen you can probably build a basic pad. Actually... in such a scenario the HLS would be so light when landing that it would have to hoverslam pretty hard when landing. So it might need a dedicated landing engine anyways. If I did my math correctly

[TrevorMonty]

To benefit from lunar propellant really need hydrolox  US. For SpaceX just not an option.

I mean, at a 3.6:1 fuel ratio, oxygen is still 78% of the fuel mass for methalox. You don't need to be producing methane for it to be useful. It should enable the HLS to go LEO -> lunar surface -> LEO propulsively (refuelling with methane and oxygen in LEO, and only oxygen on the lunar surface).

Or LEO -> lunar surface -> earth surface, with the heat shield. That would interfere with the mid-ship landing engines, but in a scenario where you have the infrastructure to harvest oxygen you can probably build a basic pad. Actually... in such a scenario the HLS would be so light when landing that it would have to hoverslam pretty hard when landing. So it might need a dedicated landing engine anyways. If I did my math correctly

You will be hauling methane in and out of lunar gravity well. For every 3.6mt of O you burn to lift payload O off lunar surface will need to deliver 1mt of methane to surface. Lot of effort for very little reward. May as well design a hydrolox powered tanker then it can land empty.

[spacenut]

Does the moon even have enough water to seriously mine for rocket fuel? 

Lox I can see due to oxygen being in the soil, but water would be needed for a lunar colony for human use, not broken down into hydrolox rocket fuel.  Break down the soil for rocks and use what water the moon has for the colony as water will be a precious commodity on the moon.  Hydrogen or methane can be brought from earth for rocket fuel, and maybe lox made on the moon since oxygen is has more mass as a liquid than hydrogen or methane. 

[OTV Booster]

The logistics of connecting a LOX supply line to a lander on the lunar or Martian surface isn’t practical.

Why?

Pick your poison:
1) ground transportation to lander on the surface
2) flight transportation of Lox to lander on the ground
3) landing adjacent to a propellant station
4) landing on a launch tower that connects with LOX

It’s a chicken and egg problem.  You cannot land on the moon/Mars until you have enough propellant to return.

Your last paragraph is absolutely true - for the first flight and for subsequent flights until propellant ISRU is in place. When that happens it is no longer true. Then the method of getting propellant to the ship is a matter of engineering/economics/convenience.

[OTV Booster]

Does the moon even have enough water to seriously mine for rocket fuel? 

Lox I can see due to oxygen being in the soil, but water would be needed for a lunar colony for human use, not broken down into hydrolox rocket fuel.  Break down the soil for rocks and use what water the moon has for the colony as water will be a precious commodity on the moon.  Hydrogen or methane can be brought from earth for rocket fuel, and maybe lox made on the moon since oxygen is has more mass as a liquid than hydrogen or methane.

How much and in what concentration are the big questions.


Opinion: basic survival use: hydration, cooking and hygiene, will use but not consume water. Losses will come from air lock cycling residuals and leaks. Industrial processes and products will be a mixed bag and rocket propellant will be total loss.


AIUI hydrogen from solar wind is available in surface rocks, and of course O (and OH?) Don't know about carbon or concentrations. Getting water precursors from rocks would take more infrastructure and energy than raw water but it's not impossible.


Economics is a funny thing. It's sensitive to circumstances. Raw water in time of little infrastructure has more *immediate* value than holding it back for speculative future use. Very short sighted but very human.


With the implicit but unproven assumption that we are going to the moon to stay, it makes a type of sense to use the cheap water now to enable the infrastructure that can harvest the expensive water tomorrow.

[TrevorMonty]

Does the moon even have enough water to seriously mine for rocket fuel? 

Lox I can see due to oxygen being in the soil, but water would be needed for a lunar colony for human use, not broken down into hydrolox rocket fuel.  Break down the soil for rocks and use what water the moon has for the colony as water will be a precious commodity on the moon.  Hydrogen or methane can be brought from earth for rocket fuel, and maybe lox made on the moon since oxygen is has more mass as a liquid than hydrogen or methane.

How much and in what concentration are the big questions.


Opinion: basic survival use: hydration, cooking and hygiene, will use but not consume water. Losses will come from air lock cycling residuals and leaks. Industrial processes and products will be a mixed bag and rocket propellant will be total loss.


AIUI hydrogen from solar wind is available in surface rocks, and of course O (and OH?) Don't know about carbon or concentrations. Getting water precursors from rocks would take more infrastructure and energy than raw water but it's not impossible.


Economics is a funny thing. It's sensitive to circumstances. Raw water in time of little infrastructure has more *immediate* value than holding it back for speculative future use. Very short sighted but very human.


With the implicit but unproven assumption that we are going to the moon to stay, it makes a type of sense to use the cheap water now to enable the infrastructure that can harvest the expensive water tomorrow.

Once there is supply infrastructure in place using Lunar water/fuel means there is ready market for Asteriod water. Its lot easier to great a business case for Asteriod mining when there is existing market for mined resources. ie mt of H2O delivered to EML1 is worth $$mt.