SpaceX BFR 150 Top Target should be Moon Colonization

A guest post by Joseph Friedlander

Elon Musk’s new 150 ton payload class rocket, IF usable as described by Brian Wang in various posts here on Next Big Future,

Spacex BFR construction will start in 4 to 6 months.
would have bigger than Saturn V payloads plus the magic of reusuability. How reusable is of course the trick, but in the optimal case that Brian has written about, to quote Brian:

at $7 million the SpaceX BFR launch 150 tons would have less than a $50 per pound launch cost…

…can take 150 tons from Earth to the moon by using orbital refueling. Each reusable Spacex BFR could make 50 trips to and from the moon each year to get to 7500 tons delivered to the moon.

…Aggressive use of SpaceX reusable launch, focused robotics automation development could achieve the critical mass of moon-based industry within 2 years after the reusable Spacex BFR is fully operational. The planned date is about 2022 for the SpaceX BFR. So 40,000+ tons of lunar industry and robotics manufacturing could be available by 2024….

By 2025, there could be a fleet of 100 BFR. Each could be flying 10-50 times per year if there the market for launches can be grown with $40-200 per pound launch costs.

…The USA could triple that production and buy a separate fleet of 200 SpaceX BFR. If each cost $200 million, then it would cost $40 billion. This would be less than the planned spend for the Space Launch System which would have one or two flights per year. The USA could fly each BFR 50 times and get 10,000 launches per year. For $7 million each flight that would be $70 billion per year to operate at maximum capacity.

Friedlander here again. Let’s run through those numbers. If it takes 2 missions (a launch and an orbital refueling) then $14 million per lunar delivery mission (150 tons up and down to the moon.) 2 launches a year delivers 150 tons up and down to the Moon. (5000 pairs of launches would deliver 750000 tons to the lunar surface although that is hardly the only potential destination) By contrast, Antarctica probably gets 50,000 tons a year in logistics for the US bases alone (most of that is fuel).

This is huge. The Saturn V done as a cargo lander could deliver 17 tons down plus probably another 9 tons as a dry stage (Skylab sized living space pressure vessel plus scrap metal). But $400 million then dollars (probably over $2 billion today, using that figure as the dividend) to deliver 17 tons leads to $117,000 a kilogram– $117 million dollars a ton to the lunar surface!

(The CSM and LM (Command/Service module and Lunar Module) stack was around 45 tons net in translunar injection from the Saturn V, but the 16 or so ton LM would land and its primary payload was actually the 4 tons plus of fuel-laden LM upper stage to return 2 men and a fraction of a ton of moon rocks to lunar orbit. So unless you were planning to stay on the moon the manned missions could bring shockingly little NET payload to the lunar surface. For example, using the LM TRUCK concept a rover could be landed (not the little flown 2 man open foldout rover but) a real enclosed long endurance rover – this would have been landed for about say 4 tons net down to stay on a landed converted LM stage. This would require dedicated engineering and a dedicated Saturn V mission for 2 flown Saturn V missions per lunar landing. This never happened, obviously! Only 13 Saturn Vs ever flown, 6 successful landings, only 3 J series missions with the (small) lunar rover build into a hex of the LM bottom stage.

But the 150 tons of LANDED cargo with the new Space X design, assuming $14 million per launch plus refueling tanker, yields a far more favorable $93 a kilo– ($93,000 a ton to the lunar surface!) That is 1258 times cheaper (remember not even counting all the engineering you didn’t have to do to create landers, etc) and that factor of a thousand is comparable to the difference between an advanced nuclear transport such as described in this (highly) speculative article of mine –but Elon Musk may be doing it for real and without risk of radioactive accidents!

$117 million a delivered ton to the lunar surface means nothing is happening. $93,000 a ton delivered to the lunar surface means extensive colonization.

You can do business at that rate. Various studies have ID’d for example the $100 a kilo range as the dividing line between bootable space power satellites and uneconomical designs. You can imagine a triangular trade developing between the Lunar colonies, the Martian surface and then the Martian colonies colonizing Phobos and Deimos the Martian Moons (referred to as PhD) and from there building solar power satellites that are powered by their own ion engines back to Earth orbit so they can give financial return by power sales to their backers.

Why the Moon as the booting place for this vision rather than Mars?

Because the synodic period for a trip to Mars is about 1 week open for a launch window (making some assumptions) every 2 years. Then the ship is out of action (committed) for a minimum (making more assumptions) for 270 days for a Hohmann transfer plus 450 for the Martian launch window to open.

So you have say a $500 million asset (the upper stage colony ship) drawing interest for 2 years which at 6% interest is a chunk of change (the time value of money) –picking a figure out of the air, say $60 million. That is $400 a kilo in interest charges alone for any Martian payload.

It makes far more sense then to build up a lunar surface colony, build a dedicated lander colony ship (prebuilt base) and launch it to Mars during the once in two years launch window. That way you are not paying the bank to rent a transport and arriving to work and rent, you are prebuying your Martian house.

Viking lander style retro rocket delta V after aerobraking is under a kilometer a second so retro fuel is a manageable proportion of the structure and leaves big empty tanks suitable for future space and water storage in your new Martian base.

And if you (survivably) land, you need not fear losing the risk of the return journey because there is none to go wrong. (Whereas Space X will be tapping their foot waiting for that $500 million lander to return so they can refurbish it—IF it survives.) If however the upper stage is needed to shuttle between the Martian surface colonies and the Phobos and Deimos colonies that is an entirely different story, because you get a far faster flight and amortization rate. You are paying a one-time charge to transport a needed shuttle to the Martian colony system. On Mars, the Space X upper stage is a SSTO –single stage to orbit vehicle. And it carries even more payload to orbit each time it flies because of the lower Martian gravity and the 3.5 km/sec orbital speed. Delta V between Phobos and Deimos is 747 m/sec. In three years it might make many hundred flights carrying a noticeable fraction of a million tons of cargo back and forth.

Back to the Moon:

Recently the Marius Hills skylight has been discovered on the Moon, detailed at this page here.

The SELENE Terrain Camera (TC) and Multi-band Imager (MI) may have identified a 65 meter diameter skylight (or hole) that penetrates a lava tube. The depth of that hole has been estimated to be 80 to 88 meters and the width of the lava tube has been estimated to be wider than a few hundred meters. (quoting from the above link)

The length is not listed but even only a few hundred meters x a few hundred meters is a good size heat moderated (say –4 F ) heat sinked environment with a good prebuilt radiation and meteorite shield. From geometry arguments alone (there are very few few hundred meter wide rivers of lava only a few hundred meters long) we can guess a lava tube around 200 times longer. Say 240 meters wide by up to 50 km long. Sound crazy long? But Wikipedia reports:

Kazumura Cave is a lava tube and has been surveyed at 40.7 miles (65.5 km) long and 3,614 feet (1,102 m) deep making it the longest and deepest lava tube in the world

And remember the lunar lava tubes should be much bigger in cross section. So a few square kilometers of shielded space. (You would probably want to have separate structures connected by pressurized passages but the key thing is you do not need to worry about solar flares (which can kill you on the lunar surface or in orbit) and you don’t need to worry about your thin plastic tank getting degraded by solar UV and holed by meteorites—in other words, it is safe space to boot up and industrial base in with a built in heat sink. It is safe space to inflate a big balloon hangar to do shirtsleeves shipyard construction in with local lunar materials and fuels. Then bring it to the skylight, put up blast shields (and capture vents to try to catch exhaust gas) and take off –or better yet, transport it to an electromagnetic launcher and save delta-v that way.

Possibly more on this Moon Mars PhD triangular trade strategy in articles to come.