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At present it looks increasingly likely SpaceX will complete their Starship based Human Landing System before the Boeing led Space Launch System is ready to commence lunar operations. SLS has a cost plus contract which incentivizes slow working in order to maximize profits whereas the HLS contract is milestone based, which encourages fast development to minimize outlay and maximize return. Already we can see some divergence between these two projects, Ars technica consistently reports the SLS maiden flight, called Artemis 1, will delay into summer something recently confirmed by NASA’s Office of Inspector General, compared to SpaceX who are straining at the bit to launch multiple Starships, as soon as they receive FAA approval.
In the past NASA could regulate the pace of development by limiting the number of work orders issued to contractors, however, SpaceX are largely funding Starship development themself so racing to achieve milestones in the shortest time possible. So far NASA seem happy to accommodate the accelerated pace at SpaceX, considering they paid for 5 development milestones they didn’t oversee, while the HLS award was being challenged by Dynetics and Blue Origin.
So let’s wind the clock forward five years or so, when HLS has successfully demonstrated its first lunar landing and SLS is likely a half decade or more from primetime. Realistically NASA will want to use this new moon landing capability asap, but won’t wait for SLS if there’s a viable alternative. A similar situation occurred with the Commercial Crew Program, after SpaceX completed their Crew Dragon spacecraft years in advance of the Boeing Starliner, NASA decided to use SpaceX exclusively for flights to the ISS instead of waiting for Boeing to catch up.
http://www.reddit.com/r/spacex/comments/scctht/what_happens_if_starship_hls_is_ready_before_sls/
