SpaceX & Iridium NEXT

Cosmic Log – Next stage ignites in the rocket biz.

Alan Boyle, Science Reportage Guru at MSNBC, discusses the new deal between SpaceX and Iridium, the Satellite telephone provider. Great news for SpaceX and hopefully bargain basement rates for space-launch for Iridium. Will be very interesting to follow the progress of both and to see if any other rocket-firms are going to make a move on providing cheaper space access.

Of course my hopes are that SpaceX will both achieve cheaper access to space (CATS) and achieve a (mostly) reusable launcher vehicle (RLV) in the form of the Falcon series. The first stage wasn’t recovered on the first successful orbital mission for Falcon 9, but I believe Musk’s avowed commitment to the concept.

But just how low can the price go? At ~$5,000/kg to orbit the price of space access isn’t cheap, even with SpaceX. As their experience base expands I think Musk & the boys will get closer to $2500-$1000/kg prices, if the demand is there. At such rates the prospect of commercial flights to the Moon arises.

How much would that take? Consider the Falcon 9 Heavy and the Dragon capsule. Fully tanked the Dragon masses 8 tons and the F9H can orbit 32 tons of payload. If we modify the second stage to be both launcher and fuel tank, then I estimate some 34 tons of propellant can be orbitted. Assuming a total mass of ~36 tons for the modified stage that means a total mass of 44 tons and a mass-ratio of (44/10) = 4.4, enough to give the Dragon a delta-vee of 4.97 km/s – more than enough to get to a low orbit around the Moon and back, assuming aerobraking return for the Dragon capsule.

Of course the real questions are: what do we do when we get there? What would it take to actually land? A Bigelow station could potentially be placed in Low Lunar Orbit, but access to the surface requires a delta-vee of 3.6-4.0 km/s. That’s a lot of propellant to be sent up from Earth. If propellant could come up from the Moon, then a landing vehicle could be operated for repeated missions. We know there’s water on the Moon and potentially something to burn. Of course we could use hydrogen from electrolysis, but it has issues due to being a deep cryogen. Liquid oxygen, the quintessential cryogen, is easy by comparison. Rockets can use powdered aluminium and LOX mixed together, which forms a stable semi-solid propellant. We know there’s aluminium on the Moon, but extracting it takes serious energy.

Some inventive rocket engineer will think of something…

Addendum: I forgot to add that powdered aluminium in water makes for a rocket fuel too. However both Al/LOX and Al/H2O produce non-volatile exhaust products that can’t be recycled like water can. Water vapour has the advantage that it will be retrapped in the Moon’s cold-traps, thus a reason to be very careful in our use of those areas. Cryogenic cold this close to the Sun is a hard thing to sustain – having it for “free” on the Moon is nothing to waste.

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