Should they re-use Starship HLS

 Re-using Starship HLS

The case for:

Starship Human Landing System (HLS) is going to be one of the most ambitious and complex spacecraft ever devised. Easily the largest thing ever sent to interplanetary space or the Moon by Man. The cost of Starship is hotly debated and I am not going to be able to answer it completely accurately here, but I can give a range. Starship HLS is going to be vastly more expensive than Starship and my numbers are going to be necessarily fuzzier. Starship itself uses 6 Raptor engines, widely reported to be about 1.5 million each (though the goal is to reach $250K), over 400 have already been made. That equals $9 million in engines.

Starship is made from Stainless steel and 120 tons of 301 Stainless Steel come to about $1.30 per kg, we can guess that the hull and tanks cost about $200,000 in Steel, obviously the robots and labour add to the cost but I can only go by the material costs. Large Batteries, Electric and Hydraulic Actuators, wiring, Heat Shield tiles, COPV Tanks, etc probably add hundreds of thousands more, but possibly less than a million dollars of materials. If I say a Starship is $20 million in material costs I am probably way overstating it and it may be more like $10 million.

From that Starship HLS will remove, the Flaps and Actuators, the Heat Shield tiles, the Header Tanks. That should make HLS at first quite a bit lighter. Then we need to add Insulation, Landing Gear, possibly tanks for the Landing Engines, Landing Engines, Solar Panels, possibly with vertical (for South Polar landing site) and horizontal deployment (for open space), boil off mitigation (I don't know what yet), Elevator/Crane, Air Locks, Docking Port, Computers and Electronics, Storage, Supplies, Water, Accomodations, Toilet, Shower, Cockpit, Life Support, Radiators (possibly on moon and open space), Power Supply (batteries?), Sensors, Radio and Telemetry. I daresay that will eat a few tons and many more back. Potentially all this will cost millions, possibly hundreds of millions if we look at other space habitats.Let's say it is between 200 and 400 million.

Surely we don't want to throw away such a significant investment after one shortish 6.5 day trip?

The case against:

One of the first problems is the below company does not exist, either in NRHO or in LEO

Without proper cleaning, hair, skin cells, and moisture will feed mold and bacteria which could be dangerous for the health of Astronauts in such a closed environment. A camera and sample containers on Apollo 12 were discovered to have mold on them, Skylab was plagued with it etc. Without gravity and without proper cleaning mold is a very real problem.

Mold Growing in ISS

Feeding in to this is loiter time, Starship HLS already has a long loiter time, 3 months, as part of the Artemis mission, add another 12-18 months for the next Artemis mission and that's an extremely long loiter time for human rated spacecraft. It's a long time sitting around with any left over contaminants growing. I am not sure any other spacecraft has ever loitered that long. It doesn't mean it's impossible but it will require solutions to problems we have not thought of yet.

To be ready for the next Artemis mission, supplies must be restocked, life support refurbished, systems checked and all consumables refilled. Again there are no technicians or engineers in Lunar or Earth orbit to do this.

Packing supplies into Dragon Cargo

One last problem is fuel. Once HLS returns to NRHO to hand off to Orion it will be pretty empty, the trip from LEO to NRHO to land on the Moon and back to NRHO is about 8 kms, that's about Starships limit.

Without the trip out from LEO the trip down to the Moon and back consumes around 4 kms of DeltaV, which is about half a tank, or 600t of propellent, not accounting for residuals or boil off. If every Starship Tanker can ship 150t of fuel then it will take 4 or more tankers to fill up HLS for another mission.

That doesn't sound so bad? However we are not done, we need to multiply each tanker by the need to get to Lunar orbit. For every Starship tanker sent to NRHO, 6 or more tankers must be launched from Earth to fill up that tanker. So 4 or more tankers in Lunar orbit is 24 or more tankers launched from Earth. If you are having trouble following see the infographic below. In some scenarios with boil off and residuals it could mean 36 or more tankers launched.

It's not that this would be mind bendingly expensive, but it would only take 6 launches to get another HLS into Lunar orbit. NASA is paying SpaceX for HLS landers and I don't know if the terms of the contract stipulate a new lander for each mission. But if SpaceX did decide to reuse a HLS they would need to allocate dozens of tankers and resources to doing so. Cleaners, engineers, fuel make it a complex solution with many many moving parts that need to work perfectly.

We can't bring Starship HLS back to Earth to be refurbished as it has no Heat Shield or Flaps, but could we bring it back to LEO? It's possible but Starship would still need 3 kms to get back to LEO. This would still require at least 3 tankers, 18 launches, and you still have all the problems above, but closer to Earth. 

Imagine this in space

Conclusion:

In my opinion SpaceX would need a better reason to try and recertify HLS for another mission. SpaceX has other plans for it's ships and I think HLS is a sideshow to the main events, Starlink and Mars.