Why does Starship need to transfer crew to/from Orion to land humans on the moon?

Question

In the new NASA Artemis program, Starship needs to transfer the crew to/from Orion. Why is this even needed?

I thought that the Starship design allows it to travel directly from Earth to the Moon without all this complexity.

Answer 1

In the new NASA Artemis program, Starship needs to transfer crew to/from Orion. Why is this even needed?

Because that is what NASA required for solicitation NNH19ZCQ001K_APPENDIX-H-HLS. A bidder whose proposal didn't involve transferring crew from Orion (and later, NASA's Gateway) in a Near Rectilinear Halo Orbit to the surface of the Moon and back to that NRHO vehicle would have been noncompliant and would have been rejected.

Whether the broad outline of NASA's contract (and it was broad; the three proposals that won the first phase were very different) makes sense is a different question. To comply with the contract, all three proposals did have five things in common:

• Rendezvous with Orion/Gateway to pick up the human crew,
• Transfer from the Near Rectilinear Halo Orbit used by Orion/Gateway so as to later land on the surface of the Moon,
• Stay on the surface of the Moon (with life support) for a requisite period of time,
• Have some part of the vehicle that takes off from the Moon with the crew inside, and
• Rendezvous with Orion/Gateway to drop off the human crew.

Answer 2

Because that's what NASA asked for.

The mission architecture for Artemis consists of:

• Lunar Gateway, a permanent space station in a Near-Rectilinear Halo Orbit, used as pretty much what the name says: a gateway between Earth and Moon.
• Orion, a crew capsule to transport crew between Earth and Gateway.
• The Space Launch System, a crew-rated superheavy lift vehicle to launch Orion. (It was also originally intended to launch Gateway and other superheavy payloads, but it seems pretty clear that commercial superheavy launchers are much better at that. The main reason for its existence now is that it is crew-rated, while e.g. Falcon Heavy is not.)
• The Human Landing System, a crew vehicle to transport crew between Moon and Gateway (or Orion, as long as Gateway is not operational).

What NASA asked for, is the HLS: a crew vehicle to transport crew between Moon and Gateway (or Orion directly, for the first mission). The fact that SpaceX chose to bid on this contract using a vehicle that can also do things that the contract doesn't require, is a choice SpaceX is free to make. But there is nothing forcing NASA to use those capabilities they didn't ask for.

In fact, there is something forcing NASA to not use those capabilities they didn't ask for, and that's the other competitors for the contract. They would sue NASA to hell and back if NASA now all of a sudden changed the contract in a way that excludes their bids.

Remember, this is only the first phase, for development and demonstration of three flights. There will be more phases, and Dynetics, the National Team, or somebody completely new might want to bid on those phases. It would be illegal to change the requirements after the fact.

So, there are contractual and legal reasons for why NASA cannot simply change the HLS requirements.

There are also contractual and legal reasons why NASA cannot cancel SLS: Boeing has put damage clauses in the contract that essentially mean that NASA has to pay them more money to cancel the contract than to finish it. So, it would be a waste of taxpayers' money to cancel SLS.

In addition, there are political reasons for why it has to be done this way: SLS is very much a Congressional beast. It was designed in Congress for Congress. NASA depends on Congress for funding. Canceling SLS is more or less equivalent to the NASA Administrator marching into the Capitol and taking a shit on the carpet while yelling obscenities at the Congresspeople. (Which ironically wouldn't be the first time this year someone has done that, but I digress.)

However, leaving all these politics and legal maneuvering aside, there is a solid technical reason for keeping SLS and Orion: they are crew-rated. Starship / Super Heavy isn't.

Well, technically, SLS is not crew-rated yet, and SS/SH will be at some point in the future, but at the moment SLS is closer. SLS is based on proven Shuttle designs, Shuttle concepts, and Shuttle hardware. The first 16 engines for the first 4 flights have literally already safely launched crew to space and braught them back several times. SS/SH is doing loads of things that nobody has ever done before, where you even have to first figure out how to crew-rate them.

And a last thing: the Lunar Starship (I would love it if they name it "Moonship"), as proposed, can actually not bring crew back to Earth. At least not all the way to the ground, because it has no landing hardware: no body flaps, no header tanks, no heat shield. So, even though Starship / Super Heavy can do the entire mission on its own (heck, it is big enough that you don't even need a base, it can be the base – and the Gateway), this particular one that SpaceX has proposed cannot.