SpaceX going it alone to harvest water

[InterestedEngineer]

A question on the 100m/sec burn from EM-L1 to mars. Can it be run in reverse to bring a returning mars ship to L1 with ~100m/sec burn? That would be another trade space to look at. With carbon or CO2, lunar water can make methane. Earth needs to get rid of CO2 but it's also dirt cheap on Mars.

Well, you have to run the ENTIRE thing, including oberth burn, in reverse.

If arrival velocity from Mars is 12-14km/sec, then you'll have to do a 1.1 - 3.1 km/sec burn at perapsis to put you on a trajectory for L1-EM, then an L1-EM insertion burn (the latter being pretty small).

Come to think of it, you might be able to aerobrake that small of a deltaV at pretty high altitude and skip back out to space and on to L1.   It'd be a pretty low risk maneuver (after some practice).

And then there's the timing issue - the moon has to be in the right location.  Which affects both directions.  I really haven't done an analysis of how much deltaV it would take to rotate the egress/ingress trajectory from the nominal periapses burn trajectory.  Which if it takes too much deltaV, means your launch windows to extra-earth locations only happens a few days per month.  (this is a great use for KSP btw, you just slide things around and take notes).

I'm curious why though - why would one refuel on the way back from Mars at L1-EM?  Maybe if EDL is truly limited to 8km/sec (I doubt it), you'd refuel so that you could do a pre-EDL rocket braking.  But multiple aerobrake passes probably make more sense and are less of a scheduling headache with regards to the moon.

Perhaps in an emergency it might make sense (as in "we somehow lost too many tiles in deep space and can't repair it" - how often would that happen?  Probably never).

[OTV Booster]

A question on the 100m/sec burn from EM-L1 to mars. Can it be run in reverse to bring a returning mars ship to L1 with ~100m/sec burn? That would be another trade space to look at. With carbon or CO2, lunar water can make methane. Earth needs to get rid of CO2 but it's also dirt cheap on Mars.

Well, you have to run the ENTIRE thing, including oberth burn, in reverse.

If arrival velocity from Mars is 12-14km/sec, then you'll have to do a 1.1 - 3.1 km/sec burn at perapsis to put you on a trajectory for L1-EM, then an L1-EM insertion burn (the latter being pretty small).

Come to think of it, you might be able to aerobrake that small of a deltaV at pretty high altitude and skip back out to space and on to L1.   It'd be a pretty low risk maneuver (after some practice).

And then there's the timing issue - the moon has to be in the right location.  Which affects both directions.  I really haven't done an analysis of how much deltaV it would take to rotate the egress/ingress trajectory from the nominal periapses burn trajectory.  Which if it takes too much deltaV, means your launch windows to extra-earth locations only happens a few days per month.  (this is a great use for KSP btw, you just slide things around and take notes).

I'm curious why though - why would one refuel on the way back from Mars at L1-EM?  Maybe if EDL is truly limited to 8km/sec (I doubt it), you'd refuel so that you could do a pre-EDL rocket braking.  But multiple aerobrake passes probably make more sense and are less of a scheduling headache with regards to the moon.

Perhaps in an emergency it might make sense (as in "we somehow lost too many tiles in deep space and can't repair it" - how often would that happen?  Probably never).

IF (a big if) lunar water works out for propellant production, EM-L1 has advantages over the lunar surface for electrolysis. Good thermal environment, 24/7 PV output and a usable HEEO refueling location. Methane production doesn't work without carbon or preferably CO2. AIUI, the moon is carbon poor. That leaves Earth and Mars.


An argument for earth sourcing is disposal of sequestered CO2. Economic arguments for and against have so many assumptions as to be useless. It's more an exercise in physics and "what if."


The economics of Mars sourcing is just as tenuous. The main benefit is a backhaul load and getting ships back into service. Deadhead is a killer in the transportation industry. What's the point of building reusable rockets if you don't reuse them? There's only so much you can do with thin stainless plate.

[Twark_Main]

All you get is bragging rights

Oh, so only the same reason people amass fortunes and raise armies? Okay then. 

[Vultur]

answering some of the "moon fuel to L1" questions I raised.

It's about 2.7km/sec from lunar surface to EM-L1 halo orbit.   Since the exhaust velocity of a starship is 3.6km/sec that makes it about half the fuel you have to burn from lunar surface to get it to the fuel keeping station at EM-L1.

Now, it's a trivial < 100m/sec burn to de-orbit to an elliptical earth grazing orbit for an Oberth burn, so that's basically rounding error.  That's the huge advantage of a Lagrange point for parking fuel depots.

So the EM-L1 point is a great place to put fuel depots, whether the fuel is from the moon or the earth.  You can get starships to solar escape speeds quite easily.  Mars transits are less than 100 days and this includes a braking burn at Mars to slow down enough for aerobraking to still work.

Now, it's about 3.2km/sec to get fuel from LEO to EML1.   That's about 65% of the fuel used.

If it costs us in the long run $10/kg to get fuel to LEO, it thus will cost us $28/kg to get it to EML1.

So whatever the Moon's LOX production costs are, they'd better be less than 28/2 = $14/kg or it'll never be economically viable.  Probably less than $10/kg to pay for the development cost.

On Earth LOX is about $0.1/kg so the production costs on earth are rounding error.

Think we can get production costs for LOX on the moon to less than $10/kg?

If tanker can deliver 250t of propellant to LEO at $10/kg that's a launch cost of $2.5m. Is that reasonable? In what time frame?

Depends on what kind of cost.

Marginal cost of launching an additional tanker flight, IMO quite possible fairly soon after full rapid/low maintenance reuse is achieved.

Total cost, including amortization of everything including development costs and pad hardware, that's much harder and would require extremely high flight rates.

[OTV Booster]

answering some of the "moon fuel to L1" questions I raised.

It's about 2.7km/sec from lunar surface to EM-L1 halo orbit.   Since the exhaust velocity of a starship is 3.6km/sec that makes it about half the fuel you have to burn from lunar surface to get it to the fuel keeping station at EM-L1.

Now, it's a trivial < 100m/sec burn to de-orbit to an elliptical earth grazing orbit for an Oberth burn, so that's basically rounding error.  That's the huge advantage of a Lagrange point for parking fuel depots.

So the EM-L1 point is a great place to put fuel depots, whether the fuel is from the moon or the earth.  You can get starships to solar escape speeds quite easily.  Mars transits are less than 100 days and this includes a braking burn at Mars to slow down enough for aerobraking to still work.

Now, it's about 3.2km/sec to get fuel from LEO to EML1.   That's about 65% of the fuel used.

If it costs us in the long run $10/kg to get fuel to LEO, it thus will cost us $28/kg to get it to EML1.

So whatever the Moon's LOX production costs are, they'd better be less than 28/2 = $14/kg or it'll never be economically viable.  Probably less than $10/kg to pay for the development cost.

On Earth LOX is about $0.1/kg so the production costs on earth are rounding error.

Think we can get production costs for LOX on the moon to less than $10/kg?

If tanker can deliver 250t of propellant to LEO at $10/kg that's a launch cost of $2.5m. Is that reasonable? In what time frame?

Depends on what kind of cost.

Marginal cost of launching an additional tanker flight, IMO quite possible fairly soon after full rapid/low maintenance reuse is achieved.

Total cost, including amortization of everything including development costs and pad hardware, that's much harder and would require extremely high flight rates.

Yeah, anything other than marginal costs are tricky.


What is a boosters lifetime? F9 experience points towards a long lifetime. And I'd guess lower lifetime refurb costs with non coking engines. Maybe more important, what is the IRS useful lifetime for calculating depreciation?


What is a ships lifetime? A whole different question. It's got a rougher job and there is only the Shuttle as a guide. Personally, I don't expect turnaround to drop below a week, and maybe several weeks, any time this decade. But then, lunar water mining is a next decade issue so maybe the cost comparison has a rough alignment.


The subject of amortized flight rate, with rapid reuse or not, is another guesstimate but I'm somewhat bullish here. Polishing off the initial Starlinks and begin replacing the older ones could be anywhere from 100 to 150 launches per year. A biannual mars effort with more ships each time, DOD launches and servicing space stations. It all adds up. Even with competent competitors there will be a lot of business.

[Vultur]

What is a ships lifetime? A whole different question. It's got a rougher job and there is only the Shuttle as a guide. Personally, I don't expect turnaround to drop below a week, and maybe several weeks, any time this decade. But then, lunar water mining is a next decade issue so maybe the cost comparison has a rough alignment.

Exactly, none of this is super near term.

The question IMO is whether there is any point where it is cost effective to invest in lunar propellant manufacturing rather than scaling up/making cheaper Earth launch.

[rsdavis9]

What is a ships lifetime? A whole different question. It's got a rougher job and there is only the Shuttle as a guide. Personally, I don't expect turnaround to drop below a week, and maybe several weeks, any time this decade. But then, lunar water mining is a next decade issue so maybe the cost comparison has a rough alignment.

Exactly, none of this is super near term.

The question IMO is whether there is any point where it is cost effective to invest in lunar propellant manufacturing rather than scaling up/making cheaper Earth launch.

My guess for anything near earth and maybe beyond the cheapest will be earth for propellant.

Maybe you could argue water and co2 from earth and then in orbit with solar power to process into LOX and LCH4 because somehow power is cheaper in orbit?

[InterestedEngineer]

What is a ships lifetime? A whole different question. It's got a rougher job and there is only the Shuttle as a guide. Personally, I don't expect turnaround to drop below a week, and maybe several weeks, any time this decade. But then, lunar water mining is a next decade issue so maybe the cost comparison has a rough alignment.

Exactly, none of this is super near term.

The question IMO is whether there is any point where it is cost effective to invest in lunar propellant manufacturing rather than scaling up/making cheaper Earth launch.

My guess for anything near earth and maybe beyond the cheapest will be earth for propellant.

Maybe you could argue water and co2 from earth and then in orbit with solar power to process into LOX and LCH4 because somehow power is cheaper in orbit?

transporting CO2 makes no sense - most of the mass is O2.  You might as well convert it to LOX and LCH4 right here on earth.  And then launch it to LEO so we can travel to the moon and other planets.

Oh yeah, that's the plan of record...

[rsdavis9]

What is a ships lifetime? A whole different question. It's got a rougher job and there is only the Shuttle as a guide. Personally, I don't expect turnaround to drop below a week, and maybe several weeks, any time this decade. But then, lunar water mining is a next decade issue so maybe the cost comparison has a rough alignment.

Exactly, none of this is super near term.

The question IMO is whether there is any point where it is cost effective to invest in lunar propellant manufacturing rather than scaling up/making cheaper Earth launch.

My guess for anything near earth and maybe beyond the cheapest will be earth for propellant.

Maybe you could argue water and co2 from earth and then in orbit with solar power to process into LOX and LCH4 because somehow power is cheaper in orbit?

transporting CO2 makes no sense - most of the mass is O2.  You might as well convert it to LOX and LCH4 right here on earth.  And then launch it to LEO so we can travel to the moon and other planets.

Oh yeah, that's the plan of record...

If power is cheaper in orbit then converting h20 to h2 and o2 is cheaper in space. Then react h2 and co2 to produce the methane.

Not clear that power will be cheaper in orbit.

[Vultur]

Also, if cost effectiveness is your goal you wouldn't make methane and LOX from water and CO2 on Earth. Both are already available. Musk mentioned it way back when, but that's for environmental reasons not cost effectiveness reasons.

[OTV Booster]

What is a ships lifetime? A whole different question. It's got a rougher job and there is only the Shuttle as a guide. Personally, I don't expect turnaround to drop below a week, and maybe several weeks, any time this decade. But then, lunar water mining is a next decade issue so maybe the cost comparison has a rough alignment.

Exactly, none of this is super near term.

The question IMO is whether there is any point where it is cost effective to invest in lunar propellant manufacturing rather than scaling up/making cheaper Earth launch.

Transportation costs will drop but will eventually bottom out. The earlier speculation of $10/kg to LEO is probably near the bottom for chemical rockets. Procedures and infrastructure can be cleaned up a bit but these will be small incremental price drops.


One conclusion drawn from 15 years in trucking is that all forms of transportation share common business concerns. And a biggie is deadhead (empty miles). It's all expense and no income. Almost all loads have some. Drop one load then deadhead to the next. Where it hurts is when there is no backhaul.


A way of dealing with no backhaul is taking a load that would otherwise be unacceptably poor paying. A good example is delivering to Miami then grabbing a max gross weight load of beer up to Jacksonville that barely pays for the fuel it consumes. Note: Except during citrus harvest, Florida is a freight poor environment.


Beer is inexpensive by weight and transportation might be as much as 25% of its retail price so the shipper is sensitive to shipping costs. Propellant is exactly that type of load. If it is produced in a freight rich environment (earth) it will be competing for lift with higher dollar freight that is less sensitive to shipping costs.


OTOH, lunar propellant can accept somewhat higher production costs because it fills a backhaul niche. Ships on the moon-earth run can run on lunar propellant and even carry extra to L1 for topping off ships on the earth-moon run. Using the beer hauling model, if the freight costs cover the cost of the fuel consumed to move the load the shipper might not be ahead of the game but they will be less far behind.


If the propellant is flung directly to L1 the total FOB L1 costs (total delivered cost at L1) are even lower and might justify toping up returning freighters for aerobraking to LEO to top off LEO depots.


This model in its full blown form is for the 2040's or later. It expects a mature space transport infrastructure, not one in development. It will not arrive full blown. Step by step. Inch by inch. And it assumes useful quantities of water. It will most likely start with local propellant use for earth return and expand in response to market forces impossible to predict this far out. I can see the canvas. I can see the palette. I do not know what the picture will be.


If Musk is seriously noodling a 50 year mars plan ISTM that investing in lunar propellant production, unless definitively shown to be impractical, is at least as good an investment/venture as the Boring Company.

[Vultur]

What is a ships lifetime? A whole different question. It's got a rougher job and there is only the Shuttle as a guide. Personally, I don't expect turnaround to drop below a week, and maybe several weeks, any time this decade. But then, lunar water mining is a next decade issue so maybe the cost comparison has a rough alignment.

Exactly, none of this is super near term.

The question IMO is whether there is any point where it is cost effective to invest in lunar propellant manufacturing rather than scaling up/making cheaper Earth launch.

Transportation costs will drop but will eventually bottom out. The earlier speculation of $10/kg to LEO is probably near the bottom for chemical rockets. Procedures and infrastructure can be cleaned up a bit but these will be small incremental price drops.

Sure. The question is whether lunar propellant can be made that cheaply. That depends on things we don't really yet know, like the practicality of mining ice from lunar craters (which depends on the nature of the ice - big sheets of nearly pure ice under fairly distinct regolith layers? frozen mud?) and the maintenance costs of equipment working in that environment.

OTOH, lunar propellant can accept somewhat higher production costs because it fills a backhaul niche.

Only if you have a lot of ships going to and returning from the Moon for some other reason. If Moon activity is otherwise limited to science and small bases for geopolitical flag showing, the volume won't be there.

So this only works if there's already large scale activity on the Moon for some other reason; lunar propellant can't be itself the justification for large scale activity on the Moon.

[OTV Booster]

What is a ships lifetime? A whole different question. It's got a rougher job and there is only the Shuttle as a guide. Personally, I don't expect turnaround to drop below a week, and maybe several weeks, any time this decade. But then, lunar water mining is a next decade issue so maybe the cost comparison has a rough alignment.

Exactly, none of this is super near term.

The question IMO is whether there is any point where it is cost effective to invest in lunar propellant manufacturing rather than scaling up/making cheaper Earth launch.

Transportation costs will drop but will eventually bottom out. The earlier speculation of $10/kg to LEO is probably near the bottom for chemical rockets. Procedures and infrastructure can be cleaned up a bit but these will be small incremental price drops.

Sure. The question is whether lunar propellant can be made that cheaply. That depends on things we don't really yet know, like the practicality of mining ice from lunar craters (which depends on the nature of the ice - big sheets of nearly pure ice under fairly distinct regolith layers? frozen mud?) and the maintenance costs of equipment working in that environment.

OTOH, lunar propellant can accept somewhat higher production costs because it fills a backhaul niche.

Only if you have a lot of ships going to and returning from the Moon for some other reason. If Moon activity is otherwise limited to science and small bases for geopolitical flag showing, the volume won't be there.

So this only works if there's already large scale activity on the Moon for some other reason; lunar propellant can't be itself the justification for large scale activity on the Moon.

IMO the mining will be the expensive part, not the purification. There is vacuum and a wicked temperature differential immediately available. We're talking about water, not rare earths.

Mining in the lunar environment will not be easy but the techniques needed to make it work will be extensions of general purpose techniques needed elsewhere on the moon, not something totally new.

What would be the activities that would generate traffic to the moon? It all starts in proving that your national member is bigger than the other guys, and even when that fades into the background it never quite goes away.

Then there is research. A far side radio telescope would be great. Fill in as many blanks here as you wish.

Tourism. It's trite but true. Ever since reading Heinlein's "The Moon is a Harsh Mistress" I've wanted to strap on wings in 1/6g and 6bar pressure. I am not alone.

Exploration. This is the biggie. It's a matter of the human spirit and intertwines with resource development. Are there useful quantities of He3? Will we develop the technology (on earth or moon) to take advantage of it? Are there near pure silicon deposits or rare earths?

By its very nature exploration gives no guarantee that you will find that which you covet. On the flip side chances are high that the unexpected will be found, sometimes pushing economic development in totally unexpected directions.

If we don't explore we won't know what we're missing.

Possibly China's greatest failure was in breaking up their 15th century trading fleets, destroying the records and banning further fleets. There is some controversial evidence that they had reached the Americas. Either way, by turning inward they lost any chance of grabbing a piece of the economic engine that drove Europe for 350-400 years.

If we go to the moon strictly as a pissing contest then huddle down in a continuously occupied but otherwise useless base, we've missed the point.[/quote]

[TrevorMonty]

Certainly the use of chair lifts on the moon will help astronauts in and out of the deep craters.

I just scratch my head with mining equipment such as backhoes and dump trucks.  Search equipment to identify the wet rocks.  Plus the necessary facilities along a mining route.

Don't need to do any material moving to extract top few feet of ice. Just cover area heat and capture vaporised water. Move on and repeat.  No need to drive in and out of craters when hoppers can fly machines in and water out. DV needed to hop 10kms is very low.

[redneck]

Possibly China's greatest failure was in breaking up their 15th century trading fleets, destroying the records and banning further fleets. There is some controversial evidence that they had reached the Americas. Either way, by turning inward they lost any chance of grabbing a piece of the economic engine that drove Europe for 350-400 years.

If we go to the moon strictly as a pissing contest then huddle down in a continuously occupied but otherwise useless base, we've missed the point.

I read the 1421 book on China reaching America. If it happened somewhat close to the way that author suggests, Then China could have had substantial colonies on the American continents starting a century ahead of the Europeans. The question, similar to the Lunar question, is whether it would have been beneficial to the parent country.  I think probably, but not certain.

[meekGee]

Possibly China's greatest failure was in breaking up their 15th century trading fleets, destroying the records and banning further fleets. There is some controversial evidence that they had reached the Americas. Either way, by turning inward they lost any chance of grabbing a piece of the economic engine that drove Europe for 350-400 years.

If we go to the moon strictly as a pissing contest then huddle down in a continuously occupied but otherwise useless base, we've missed the point.

I read the 1421 book on China reaching America. If it happened somewhat close to the way that author suggests, Then China could have had substantial colonies on the American continents starting a century ahead of the Europeans. The question, similar to the Lunar question, is whether it would have been beneficial to the parent country.  I think probably, but not certain.

If we're doing geopolitics, it's a good observation that China didn't lose the race 400 years ago because it allowed the Westerners to steal its technology.

China lost it all because it went stupid and destroyed its own science and technology.

[redneck]

Possibly China's greatest failure was in breaking up their 15th century trading fleets, destroying the records and banning further fleets. There is some controversial evidence that they had reached the Americas. Either way, by turning inward they lost any chance of grabbing a piece of the economic engine that drove Europe for 350-400 years.

If we go to the moon strictly as a pissing contest then huddle down in a continuously occupied but otherwise useless base, we've missed the point.

I read the 1421 book on China reaching America. If it happened somewhat close to the way that author suggests, Then China could have had substantial colonies on the American continents starting a century ahead of the Europeans. The question, similar to the Lunar question, is whether it would have been beneficial to the parent country.  I think probably, but not certain.

If we're doing geopolitics, it's a good observation that China didn't lose the race 400 years ago because it allowed the Westerners to steal its technology.

China lost it all because it went stupid and destroyed its own science and technology.

What makes me nervous is that it could happen here. Going stupid at large even with many brilliant and motivated individuals trying to move forward. That Musk is considered such an anomaly should be a warning sign. The pushback against so many possibilities concerns me as stagnation is possible with similar results as you point out.

Whether it's Mandarins or NIMBYs or pork or antibusiness,  the edge can be lost. I'd be willing to say that the US edge has been dulled already. Not gone, but not what it could be.

[OTV Booster]

Possibly China's greatest failure was in breaking up their 15th century trading fleets, destroying the records and banning further fleets. There is some controversial evidence that they had reached the Americas. Either way, by turning inward they lost any chance of grabbing a piece of the economic engine that drove Europe for 350-400 years.

If we go to the moon strictly as a pissing contest then huddle down in a continuously occupied but otherwise useless base, we've missed the point.

I read the 1421 book on China reaching America. If it happened somewhat close to the way that author suggests, Then China could have had substantial colonies on the American continents starting a century ahead of the Europeans. The question, similar to the Lunar question, is whether it would have been beneficial to the parent country.  I think probably, but not certain.

Looking on the Atlantic side, one of the first paying loads from N. America was timber, especially the mast sized trees, to build more ships.


China faced deforestation too but I'm unsure of the dates. At some point China also faced a silver shortage. Silver was their US$ equivalent. How can a civilization discover two new resource rich continents and it not be an economic boon? The only way I can think of is to play ostrich, head in sand.


That said, I seriously doubt the moon would give any significant payback until the 2040s. Development won't be even so some things will pay off early, some late. If lunar water has anything near economical output I'd expect it to be one of the early ones.


We've had endless discussions about the number of tanker flights and depot repositionings the different lander refueling strategies call for. Get rid of SLS/Orion and go with all SpaceX hardware and it doesn't get better. By the '40s SS will most likely be certified for crewed EDL and propellant ISRU ready to shift into production.


Focusing strictly on lunar surface refueling,  can anybody make an educated guesstimate on the number of tanker loads saved per crewed mission and how much lunar propellant it would take to do it? Because the earth sourced tankers/depots need to accumulate from others before staging higher the lunar production will be less than the total it displaces. Maybe a lot less.

[OTV Booster]

Possibly China's greatest failure was in breaking up their 15th century trading fleets, destroying the records and banning further fleets. There is some controversial evidence that they had reached the Americas. Either way, by turning inward they lost any chance of grabbing a piece of the economic engine that drove Europe for 350-400 years.

If we go to the moon strictly as a pissing contest then huddle down in a continuously occupied but otherwise useless base, we've missed the point.

I read the 1421 book on China reaching America. If it happened somewhat close to the way that author suggests, Then China could have had substantial colonies on the American continents starting a century ahead of the Europeans. The question, similar to the Lunar question, is whether it would have been beneficial to the parent country.  I think probably, but not certain.

If we're doing geopolitics, it's a good observation that China didn't lose the race 400 years ago because it allowed the Westerners to steal its technology.

China lost it all because it went stupid and destroyed its own science and technology.

You been reading the national news lately?

[redneck]

Possibly China's greatest failure was in breaking up their 15th century trading fleets, destroying the records and banning further fleets. There is some controversial evidence that they had reached the Americas. Either way, by turning inward they lost any chance of grabbing a piece of the economic engine that drove Europe for 350-400 years.

If we go to the moon strictly as a pissing contest then huddle down in a continuously occupied but otherwise useless base, we've missed the point.

I read the 1421 book on China reaching America. If it happened somewhat close to the way that author suggests, Then China could have had substantial colonies on the American continents starting a century ahead of the Europeans. The question, similar to the Lunar question, is whether it would have been beneficial to the parent country.  I think probably, but not certain.

If we're doing geopolitics, it's a good observation that China didn't lose the race 400 years ago because it allowed the Westerners to steal its technology.

China lost it all because it went stupid and destroyed its own science and technology.

You been reading the national news lately?

Your point being that concern is warranted?#1 Or that we shouldn't worry about anything?#2  My thought is #1, and there are others that see #2 as the correct vision.