Reasons To ARM Wrestle – Item 8

Providing the beginnings of a lunar gateway.
It turns out that getting to and from lunar DRO, and to the lunar surface from a lunar DRO, isn’t massively different from getting to and from Earth-moon L1 or L2. The orbital dynamics are a bit more complex but the propellant and travel times are relatively similar. And some lunar DROs can be long-term stable without active station-keeping. If we were ready to go straight to the moon, L1 or L2 might be slightly preferable to a lunar DRO as a location for a lunar gateway, but if we did something like ARM, with the habitat module, you’d already have a de facto start to a lunar gateway — one that likely would be set up (by NASA or follow-on efforts) with ISRU hardware and include at least rudimentary rocket fuel storage and handling capabilities.
For those unaware of Distant Retrograde Orbits (DRO) they are, simply put,orbits that are placed at a significant distance altitude from the body they orbit, and at a direction of travel opposite of that parent body. They are typically very stable orbits, and ARM Option B intends to use a Lunar DRO (LDRO)* to capture the retrieved asteroid boulder around the moon for the later crewed rendezvous.
I will have to give Goff the benefit of the doubt on this, as I don’t have a grasp of the differences between the orbital dynamics of LDRO and Lagrange points. That said, I suppose if the differences really aren’t that great and the logistics likewise not much different, I could certainly see an opportunity to bootstrap an early gateway capability. The real challenge here is to convince mission planners to include the gateway capability into the ARM plan. I don’t know that it is something we can sort of just scab on later, or at least doing so without pre-planning for it is likely to cost more.
*I have also seen the term Selenian DRO (SDRO) used, I am not sure yet what the most common convention for this term actually is. Time will tell.

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