For the RFI I do not see a way to lower SLS cost were it would be a valuable asset to the launch fleet for crewed BLEO exploration. What I do see is ULA's ( half owned by Boeing ) Vulcan with it's advanced upper stage ACES that can provide NASA the flexible path forward for Air Force, commercial, NASA robotic , and crewed BLEO missions. The Vulcan is such that it has a job of launching day to day payloads unlike SLS that is scaled to large payloads only for it's per launch cost. Vulcan with ACES ( US, tanker, and depot version ) can also deliver the crewed deep space missions. So one launch vehicle with one yearly fixed overhead instead of two with payloads already for the Vulcan. The SLS still has lack of support for missions. Were Vulcan already would have payloads and can be used by commercial for their possible BLEO enterprise such as the moon.The Vulcan with 8m fairing would be capable of delivering most SLS payloads, Orion included, to LEO. Where ACES could refuel and deliver payload to its final destination.
What I see as a possibility is to change some of the SLS contracts to Vulcan. Such as the ATK solids for SLS to the new solids for Vulcan. Doing so could help get Vulcan with ACES launching sooner. The sooner it is certified for DoD launches the sooner the Altas V and the more costly Delta IVH can be retired. The Vulcan would use American made engines unlike the Atlas V helping the over all American economy that helps fund NASA. By canceling the SLS by a phase out over 6 to 18 months can help in finding new jobs for the people that would not be switched to the Vulcan by the sub contractors. Also gives time to save some of the infrastructure that might be used later on in other projects.
As NASA crewed BLEO is for exploration and not colonizing ( that is for commercial ). Vulcan ACES is supported by other launches and can be ready for NASA BLEO launches without yearly fixed cost to NASA like the SLS has. NASA could then invest the funding on the payloads needed for crewed BLEO exploration. This also can help when transitioning from one administration to another as they may change to destination. Hove ever the launch system stays the same, as so can the EDS ( ACES US ) and other hardware as it uses the same launcher.
While ULA could provide fuel launches, the likes of Blue and SpaceX could do cheaper. Plus scheduling can be tighter, once fuel is launch, Vulcan can launch a day or more later.
There is no requirement for NASA to own or develop fuel depots, let ULA provide their own solution.
This is clearly a plan built for ULA and its parents with an excessive amount of LV capacity. Go figure.
It implies that ULA be included in every BEO mission along with SLS (LV apartheid) in direct contrast to NASA plans for a LV independent architecture with the goal of reuse to economically explore. History has shown that same approach with Shuttle and NASA has no say to reduce costs, advance concepts, nor explore. Recall: Congress cast aside depot centric in 2004, after failing to achieve anything related to the 1958 NASA Act for decades
How best to follow up on decades of stagnation: HLV+depots: oxymoron
Par for the course and quite hypocritical.
IF the USG pays for the development, then USG sets the requirements as well. 'Set the requirements and get out of the way' (follow the 1958 Act link above for more details, esp Charters) does not allow for technology advancement nor need changes nor the best interests of the nation. Many issues, but fundamentally: does the awardee retain exclusive rights and for how long. It is further complicated by ITAR. Vulcan v0 however with solids needs a redesign to provide more potential for reuse and lower costs
but this focus is lost when the USG loses control. ("Hey there is no market for reuse") yet they want depots...triple edge sword.
ULA or any company has been 'free' to provide a tanker and refillable stage (it clearly is not a depot, just a transfer stage pretending to be a depot, as the trades are quite interesting
) for quite some time without USG funding and they can set the requirements for their 'markets'. Not reducing launch costs was not the agenda for Congress nor companies, but with a dearth of payloads, is in the interest of most of the taxpayers--the exception is if you are a taxpayer with a job supported by the decades long approach.
Another issue with the ULA tanker approach is Using propellant for power at $1,000 to $10,000 /kg -- if you are a LV provider, then you should jump all over this option
as its likely best to move the propellant with EP.
So lets get started on that LV independent architecture
based on reuse with common configurations for Class A to D payloads to provide demonstrated reliability.