Eleven Refuelings for Complete SpaceX Lunar Mission

Marcus House has worked with several people to use detailed calculations to model the first SpaceX lunar missions. NASA has funded the development of a lunar Starship.

There are propellant calculations by Aeneas.

They have determined it will take about seven refueling missions to fully fuel a lunar Starship in Earth orbit. This would then have the fuel to go to the moon, land on the moon and take off from the moon to return astronauts.

Four more refuelings would be needed to give the Starship enough fuel to re-land on the moon from lunar orbit.

They designed a stripped down refueling tanker Starship that would be able to bring 170 tons of fuel to Earth orbit each time they were launched.

SOURCES – Marcus House
Written By Brian Wang, Nextbigfuture.com

79 thoughts on “Eleven Refuelings for Complete SpaceX Lunar Mission”

  1. That's an additional dedicated starship launch. Of course in this blogger world bought from Elon Musk, that is only an extra $2M.

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  2. Well yes, if they send the passengers up on the first launch and then wait for another 7, they'd better be on a near daily basis or better.

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  3. Turns out water and C and even N are more avail than dreamt even recently. So, the question is how cheap will it be, compared to from asteroids? BIS sez skip Moon go directly to Bennu. The amounts are astronomical. The first smidgen of (non sunlight) material collected and used in Space will be the historic start of an economy that does not deplete Earth resources, and will soon add to them.

    "Earth-based radar measurements were used to identify the areas that are
    in permanent shadow and hence have the potential to harbour lunar ice:
    Estimates of the total extent of shadowed areas poleward of 87.5 degrees
    latitude are 1,030 and 2,550 square kilometres (400 and 980 sq mi) for
    the north and south poles, respectively.[23]
    Subsequent computer simulations encompassing additional terrain
    suggested that an area up to 14,000 square kilometres (5,400 sq mi)
    might be in permanent shadow.[24]" -WIKI

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  4. "The privatization of space has been a program disaster"

    Surely the private efforts are the only thing keeping it from complete collapse.

    That's like saying

    "having lifeboats on the Titanic was a disaster"

    The problem was NOT ENOUGH lifeboats, not having lifeboats at all.

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  5. They haven't done it with the booster yet, and it may take some time to work it out, just like it did with falcon 9 booster landings. They might have to do tear downs and re-designs if they start having problems with reflights. Could take a few years I would think. Or they might get it right super fast.

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  6. "SpaceX can reach the ISS, and that's about it."

    So he can go further than NASA? As far as Russia?

    "I can see why even the we-can't-do-anything-because-we've-lost-all-core-competence"

    NASA's core competency is picking PPT fonts. Don't believe me? Why don't you research when NASA will develop a reusable rocket?

    "The privatization of space has been a program disaster"

    Yeah we have reuse, regular launches and soon fully reusable rockets larger than Saturn V. Private space hasn't been a program disaster so much as an embarrassment to NASA's decades old model that was precisely calibrated not maximize kg to LEO but kg of pork to congressional districts.

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  7. Thus the problem. We don't. All we actually know is that we want to live in free Space, O'Neill haz the plan. 1 g everywhere desired, except on wrong planets.

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  8. $250 million for 100 metric tons.

    $2.5 million per metric ton is actually not that bad. That's $2500 per kg to THE MOON. We would need fewer launches if somebody gets LUNOX style ISRU to supply oxidizer and if we set up higher ISP (VASIMR style) tugs to take the bulk goods to the moon.

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  9. Colonizing Mars would be the best thing to happen to any Martian bacteria in the las hundred million years.

    All of a sudden you get warmth, water, etc.

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  10. Hah. You don't need 2200t. That is far too much. You can do it with less than a third of that and better still. Chemical only.

    The rocket equation, using the numbers in the image, and allowing for four different refueling orbit-locations, allows you to do it with 668 tons of fuel, including return to LEO orbit with 5 tons of rocks (you can do more payload, but I calculated 5tons return in my scenario based on what a commercial capsule of a competitor, having been thrown a bone by NASA, could return to Earth).

    As an example, to increase DV with 1km/s at 380ISP you need only 68 tons of methalox for a 220mton vehicle. To get to the moon LLO you need 4.04km/s.

    Aeneas is almost there, he should just get a little bit more creative with where he puts his refueling tankers. I used four, but the numbers get better with more. Yes you have to pre-stage the tankers but the reduction in propellant per mission is ginormous, even when prestaging on purely chemical prop. Prestaged tankers can be used as sensor platforms. In cislunar there are lots of payloads which offer a reasonable ROI while onboard a tanker in its specific orbit.

    Here I did not calculate the fuel to prestage the tankers, but the numbers are benign if you remember to daisy chain the fuel transfers. And of course, it gets far better if you prestage the tankers using ion propulsion at >2500ISP, which space tug developers would recommend; but that is a calculation for another day.

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  11. I question whether the Mars Starship will be stock, either. At least the landing legs will probably be upgraded. It will also need systems to allow for storage of cryogenic fuels for on the order of half a year or more, something the regular Starship doesn't need.

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  12. If memory serves, it only takes 3 or 4 refuelings to fill a Lunar Starship enough for it to get two astronauts plus 850 kg of cargo to the Lunar surface. The 11 refuellings are for taking 100 tons, which would take about 100 missions of the National Team lander (assuming an astronaut weighs 70kg, two plus 850 kg cargo equals 990 kg on the surface) to do.

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  13. Yes, but it is unthinkable mostly because every launch is a half-a-billion-dollars affair. If every Starship launch costs twenty million dollars, then twelve launches is still a quarter of a billion, which is about how much a single Vulcan-Centaur launch costs.

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  14. It's a matter of conservation of engineering resources. I realize engineers aren't actually fungible, but Musk, for all that he's a billionaire, actually does have finite resources to deploy. 

    And he's kind of bet the farm on Starship, he has to get it working, quick, or he's in big trouble. His Starlink roll out schedule actually depends on the cargo capacity of the Starship becoming available quickly, and he's obligated to meet that schedule as part of the FCC license.

    So he literally can not afford to divert resources from getting Starship working. It must be accomplished ASAP.

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  15. Starting today, would building an oxygen extraction system (roving collectors, processor, storage and solar panels), be harder than building the lunar Starship from where SpaceX is at today? Deployment and operation could be directed from Earth – no need to keep crew there as it operates, or rely on advanced robotic intelligence.

    Note that quite a bit of development has already been done on collecting regolith (simulant) and transferring it. The processing doesn't need any exotic chemistry. Purifying extracted oxygen (free of lunar dust for example) seems likely to be the biggest challenge.

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  16. Note that you don't need to refuel the lunar ship 7 or 11 times – you can leave a single tanker in orbit and fuel it multiple times, then do a single transfer to the lunar ship. That does cost you an extra tanker, but if there is risk to the (presumably more valuable) lunar ship, this approach might be worthwhile. There could also be redundant fuel ports.

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  17. 11 refuelings is insanely dangerous and inefficient. Because America has incredibly and foolishly tied its space program to a single 50-year old overworked man, it can't admit that it no longer actually has a manned space program, it has a manned NEO program only.
    Every other space company is a joke for manned space flight; Blue Origin and Virgin Galactic can't even offer to reach actual space at 62 miles above sea level, or can only do so for 2-3 minutes for multi-millionaires.
    SpaceX can reach the ISS, and that's about it. The privatization of space has been a program disaster, giving us the totally predictable rise of billionaire joyrides, useless for any sort of human advancement into space for living and working.
    11 refuelings is asking for orbital explosions, malfunctions, or even strandings. One refueling…maybe could be justified to get out of Earth's gravity well without having to lug so much fuel to get to Mars, though you'd then need a fully fueled rocket with almost as much fuel for the return trip.
    I can see why even the we-can't-do-anything-because-we've-lost-all-core-competence SLS is kept limping along, to hedge against the absurd key man risk that is Musk.

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  18. I think that on Earth orbit, if your ship is high reflective to light and ultraviolet, it will cool easily. Only the Sun is really hot, so it's not so complicated to balance the temperature.
    Although to sustain liquid oxygen cryogenic temperatures are needed, (under -120º Celsius), so an active cooling is needed, powered by solar energy.
    Because the mass cooled are high, I guess radiators will be needed to balance the exterior temperature of the fuel depot.
    But nothing extreme.

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  19. Well… Mostly expected, because this is the regular ratio between fuel and cargo. Around ten, although they can reduce to seven.

    This is ok at first, because stimulate the reusing. One only mission to Moon represents a lot of launches.

    But on long term, it's better less launches. Because the fuel/cargo ratio is always similar, the solution is the difference on size between refueling ship and transport ship.

    Here comes the SuperHeavy "plus". This ship doesn't need to be man rated, like human support, extra shielding and all this things at first because it is only a refueling ship.

    A UltraHeavy with 4x cargo capacity of a SuperHeavy it could refuel a Moon/Mars mission in two or three flies only.
    Even it's possible a first load in LEO but a next refuel on high elliptic orbit. On Earth yet (so fast return for the refueling ship, just days), but a lot more delta-v combined for the Starship because most of the energy to leave Earth influence is already spent & refueled.
    (This architecture has only sense beyond Earth influence, like Mars. It has little sense for Moon missions)

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  20. Moon has Carbon! See my comment below to DP. But also, we want to live in free Space, not on planets. Certainly not with wrong gravity. Micr0g is a necessity!

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  21. What if *success* means getting the "fueling stations", more than *waiting for* a human presence on the Moon-then-Mars, "early missions"? Fuel etc for building Space Solar etc "enough demand" is a much larger project than Mars, will need more people just to tend the robots. Which do we want? Mars lifeboat or Earth salvation? Time to think! Is the surface of a planet the right place?

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  22. Do we have any evidence to suggest that waiting for 1 SLS will not take much longer than waiting for 7 + 1 SpaceX launches?

    Because so far, the evidence suggests SpaceX would be there and back in the time it takes SLS to update their powerpoint slides to show the plan for the new mission.

    And that's allowing for the fact that SpaceX will take twice as long as their initial time table.

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  23. Yeah, but Oxygen is nearly 50% of just about every rock and dust particle you see. Grab material at random and start extracting.

    Hydrogen requires you to go and find the "ice" deposits, which have been found, but you have to go to isolated locations. "ice" in scare quotes because it's more like frozen mud.

    And there is no useful amounts of carbon found so far, so that limits you to hydrogen, which is harder to handle and store than methane or other hydrocarbons (though, clearly, it can be handled and has been for over half a century).

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  24. Well the target cost (to Spacex, not customer) for Starship orbital launches is $2,000,000. So $22 million to refuel. They could be off by an order of magnitude and it would still be an order of magnitude cheaper than SLS.

    And that gets you a vastly bigger lander than anything Blue Origin or Dynetics has to offer.

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  25. I'm suggesting a bare bones, one shot fuel tanker. A flying tank, basically. Doesn't need landing legs, because it's never landing.

    The lunar landing Starship can't be that bare bones, because it does need landing legs, probably better ones than the regular Starship given that it's landing on an unimproved surface.

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  26. Except live-able gravity which is most important. At least Mars has about 1/3 of our planet compatibility. It makes a huge difference for long term space faring people.

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  27. Not that difficult in theory. As Einstein once said, “In theory, theory and practice are the same. In practice, they are not.”

    In interplanetary space, sure, just throw a sun shield or two between you and the Sun, and your fuel will stay cryogenic. So will your batteries, motors, and electronics, not so good. You probably need to add a solar panel and electric heaters for everything that you can't afford to have that cold.

    In orbit around the Earth? You've got this room temperature object radiating IR and reflecting sunlight, at angles that vary as you orbit. Two sun shields, maybe, moving independently? And that panel and heaters.

    And in either case active temperature control, as you don't want your propellant or oxidizer freezing solid on you. Methane freezes at 91K, oxygen boils at 90K. You actually have to either pressurize your Oxygen to significantly over atmospheric, or maintain them at different temperatures! Well, the Starship IS rated to 6 bar, so you can run them both at the same temperature, I guess. But the engines actually expect both to arrive at just above their freezing points, SpaceX does that to enhance the fuel density.

    Seriously, it actually does need to be tested out in practice.

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  28. It has its own resources, but it's not the same. It has mere traces of an atmosphere (so no aerobraking), less gravity, debris can be launched to ridiculous distances, electrostatic effects of dust can do nasty things to your habitats and machinery, two weeks days and nights, it has no significant sources of carbon, etc.

    It's nearer, true, but it's a whole different problem compared to Mars, except for the launch requirement and transit parts, which can share some of the hardware.

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  29. When you have ISRU fuel is where Starship really shines.

    Otherwise it would take longer and be more complex to get a mission ready. 11 launches plus the crewed one are nothing to sneeze at.

    For a government program, such number of launches for a single mission is simply unthinkable. But Musk isn't thinking as a public space agency. He wants and open two way road into interplanetary space.

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  30. The lunar Starship already doesn't have flaps and you can't drop the landing legs or hot gas thrusters. If they go with an expendable booster (I mean for lunar variant launches) they can drop the giant steel grid fins. Maybe also drop some COPV and barrel stringers? In addition to using all the fuel instead of saving it for the boostback and landing burn.

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  31. Launches are only cheap once you have established reliable reuse. If it takes them a few years to work that out, they may not be ready in time.

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  32. With so many fuelings I don't see any clear advantage to the SpaceX solution. It may not be any cheaper to get to the moon with 11 fuelings, the wait time is going to be incredibly long and the risk for the fueling port to be damaged probably high. There is an advantage for missions that require big loads, but they are not be the majority. Like the case usually being Space X is going to be offering a solution with advantages and disadvantages like other solutions.

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  33. I think it would be better to go to the moon using two Dragon Heavy. One to launch a descent/ascent lunar vehicle. And the other to launch a Dragon capsule and a stage to leave earth's orbit and enter lunar orbit and to leave lunar orbit.

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  34. Not that difficult. Shield the sunward side. And radiate heat from the shaded side. Space is just a big vacuum bottle.

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  35. That's a lot of refueling. The lunar regolith can yield oxygen and metal particles as fuel. Solar power can be used to extract O2 from the regolith. The processed regolith can then be compressed and used in a hybrid rocket. O2 is 80% in mass of the propellant need. The O2 and the processed regolith can also be launched into lunar orbit and even sent to earth's orbit. You don't need lunar water to make rocket propellant.

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  36. Staking out the interstellar infrastructure market.
    Musk will be tycoonest of all. I sure hope he is benevolent.

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  37. So why spend all this money and resource to go to the moon where weve been before. Sure it's close, but the sphere has very little gravity and cannot support anything. Mars is a much more worth while enterprise. We should be practicing how to deliver equipment to a chosen spot on Mars instead of something like the moon. If I were only in charge of NASA. SLS GONE Starlink GONE. Moon Trips GONE. Mars Full steam ahead. Start spending $$ where we "Humans" can get ahead. Remove politicians from these decisions.

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  38. This is where crew or robot comes into play. We cannot wait for robotic precursor to get stuff ready and then go ourselves. So we have not done it for over four decades. We were not even going to the Moon at all, for Mars mission, until Bridenstein. Now, the O'Neill/Bezos/BIS robot people recommend using the Moon only to provide L points. NASA/Musk crew seems to still be Mars Direct/First/Only with practice on Moon. Nothing further for Moon. Not even fuel. OK . . . ? So NASA/Bezos/O'Neill is robots on Moon, plus additional crew module as separate thing. Bezos is not stalling on the robot lander part. Now, the crew in lunar orbit servicing robots soundz good.

    https://www.bis-space.com/membership/jbis/2019/JBIS-v72-no09-September-October-2019%20-%20Subscription%20Copy.pdf

    edit: "blue origin established perhaps the best space resource team in the industry almost overnight."

    https://www.rayradar.com/2021/07/28/blue-origin-jarvis-project-exposure-is-committed-to-building-reusable-rockets-against-spacex/

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  39. So here's an ignorant question from an ignorant person. How hard is it to keep a very large quantity of liquid methane and oxygen at the proper temperature for a long time (months at least) while in orbit around the earth? Being baked by the sun very few hours, onboard systems generating heat, etc. You will need solar power but that's inevitably going to absorb heat too. You can radiate heat into space but you need to be careful not to expose the radiators to the sun. Is this a special challenge or was this problem solved way back in the Skylab days? Sincerely curious….

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  40. Fully expending the booster doesn't actually gain you much payload to orbit. Practically none, actually.

    You'd gain a bit more by fully expending the upper stage, just leaving it in orbit, and occasionally bringing down a cargo load of dismounted engines. Doing that would allow everything related to reentry and landing to be stripped off the 2nd stage, and you'd no longer have to hold back enough fuel for the return trip, so the amount of fuel brought to orbit would substantially increase. The upper stage would be reduced to just a big fuel tank and a demountable engine set.

    Doing it that way would make some sense if you had a use in orbit for the empty tanks, like building a large space station. Probably doesn't make sense if you're just leaving them in orbit without any intended use.

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  41. Sure, for early flights it doesn't make sense, but for the long term it makes great sense. It's not a solution for the first missions, it's a solution for eventually making travel between the Earth and the Moon routine.

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  42. Need some fueling stations in appropriate orbits around Earth and the Moon. But they would require routine tanker missions like fuel deliveries to gas stations on Earth, which requires quite a bit of equipment, infrastructure and enough demand to make it worthwhile. No problem, that just means it will take time.

    Meanwhile, for early missions we'll just have to do it the hard way.

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  43. You have to ask, when does the mission take place, in that scenario? Development of the oxygen extraction equipment takes time, and the mission can't launch until it's available.

    Then, how long does it take that equipment to generate and store enough oxygen? Probably longer than you want your crew on the Moon, so it has to be robotically deployed, and the manned mission wait on the oxygen accumulating.

    I'd guess a serious push could have us back on the Moon by 2030, using this approach. If we really worked hard at it.

    And, how many refueling missions could you pay for, using the money it would take to develop that equipment?

    NASA is all about adding unnecessary steps to missions, (When they send somebody out for lunch, they first build a base camp in the McD's parking lot.) but they're not patient enough to take this approach. Nor is Congress.

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  44. They ought to take an approach similar to the fuel production on Mars. The first landing delivers a system to extract oxygen from rocks and liquify it. That's about 2/3rds of the fuel mass for lift-off to lunar orbit, and around 30% lower mass to lunar surface, cutting out 2 of seven refuelings on all subsequent missions.
    Then use some of that mass savings to land extra methane, and use that to launch extra oxygen to lunar orbit, so that less oxygen needs to be delivered from Earth to land the Starship again.

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  45. What if they fully expend the booster for the lunar ship? Maybe that would save some trips? It would be cool if they developed the 18 meter diameter version for tanker launches.

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