What is the point of launching EM-1 on DIVH/F9H?

Question

EM-1 was originally a full-up test of the SLS block 1B: Orion, ICPS (a modified 5-meter Delta cryogenic second stage), and the first stage/SRBs.

NASA administrator Bridenstine’s statement on 3/13/2019 suggested they might launch Orion and a fueled ICPS on two separate commercial booster launches. The two then rendezvous in LEO for the EM-1 flight around the moon.

This implies that, without other changes to the SLS program, the manned EM-2 mission would be the inaugural flight of the first stage and SRBs. On the grounds of safety, it is hard to see how the EM-2 plan would be allowed to stand. At the same time, neither of the two commercial boosters under consideration – Delta 4 Heavy (DIVH) and Falcon 9 Heavy (F9H) – are human-rated. SpaceX has previously gone on record to say that they weren’t human-rating F9H, and the DIVH production line is in the process of shutting down. Yet one of those vehicles would need to be human-rated in order to be used for further Orion flights.

So, other than developing and proving out a mission architecture that has waited half a century to be realized, what of the original purpose of EM-1 would be served, leaving what possible path forward for launching humans into deep space?

Answer 1

what of the original purpose of EM-1 would be served...?

It is hard to tell from the NASA administrator's comments in Ars Technica's Here’s why NASA’s administrator made such a bold move Wednesday:

"SLS is struggling to meet its schedule," Bridenstine replied to Wicker's question. "We are now understanding better how difficult this project is, and it’s going to take some additional time. I want to be really clear. I think we as an agency need to stick to our commitment. If we tell you, and others, that we’re going to launch in June of 2020 around the Moon, I think we should launch around the Moon in June of 2020. And I think it can be done. We should consider, as an agency, all options to accomplish that objective."

The only purpose would then to be to demonstrate the principle that commitments should be stuck-to.

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The principles described in Mitchell & Webb - Conspiracy Theories. (after 02:57) however teach us that in order to convince people that you have the capability to go to the Moon in a rocket, the first step is to actually build a real rocket that really has that capability.

NASA's primary mission was to troll Elon Musk on Twitter with images of a rocket capable of sending the Orion capsule to the Moon with people in it, in order to entice him to pull some focus away from a Mars-bound crew-delivering rocket to work on a Moon-bound crew-delivering rocket.

In order to make those tweets believable, NASA has to first build the rocket and demonstrates that it does the job for the trick to work.

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After about 02:00 per this answer "Chris Ferguson, commander of STS-135 and now manager of the Boeing CST-100 program and slated to command its first mission" says:

You know the Space Shuttle’s been with us, it’s been the heart and soul of the human spaceflight program for about 30 years and you know, it’s a little sad to see it go away, but hopefully in the not too distant future you’re going to see a heavy lift vehicle manufactured by our commercial partners, designed by NASA in partnership, and we’re going to go back to the Moon; back to Mars.

So the future is very bright.

Answer 2

Sadly, the point may just be to kick the SLS folks in the butt to be on time and on budget for once, that Senate support of their laziness may be blocked by the administration. Doing the LEO assembly approach has almost too many problems. The most glaring: the SLS mission profile has the core booster imparting enough speed and altitude for the Delta Interim Cryogenic Propulsive Stage to coast to a high eccentric orbit. From there the ICPS would perform the Trans-Lunar Injection burn. From various online discussions, the evidence points to ICPS being unable to do the TLI from LEO. This leaves LEO assembly dead-on-arrival, unless a private company can launch a more powerful substitute for the ICPS. I know of no such rocket stage. For the timeline to work, any proposal must rely on existing main components. If that problem is overcome, another big obstacle is developing on-orbit assembly hardware and software. Earlier successful craft were designed from inception to have this capability.

A proposal NASA did not look for is a single launch of Orion/ICPS on the Falcon Heavy. The SpaceX site gives the maximum load to LEO of 63,800 kg, which is 7000 kg more than that combo. Leaves room for weight of fairings and adaptors. See this pdf https://www.reddit.com/r/SpaceXLounge/comments/b1g6z7/a_private_em1_proposal_falcon_heavy_orion_icps/

It is unlikely FH can deliver Orion/ICPS into the required orbit, repeating the TLI problem. However, there is room in that 7000 kg for a kick-stage, and a specialized FH would have landing leg components, grid fin mechanism, etc, removed. This fully expendable launch would cost more than 2 recoverable launches, but has less cost overall compared to development of on-orbit-assembly. Higher probability of success, since engineering/fitting parts together on the ground - can do ongoing trouble-shooting.

And to your main point: This approach would not be pointless re EM-2 if it were actually used for EM-2. This saves the billion-plus cost of each SLS launch. SpaceX had, prior to this, no interest in human-rating the FH. But NASA has changed the game. SpaceX has a straight path to rating FH, since its core and side boosters are all human-rated F9s. These F9s will have a real track record by the time of the 2022 EM-2 launch. There is certainly time for FH to go through the full review and approval process, and launch a commercial load or two.