“- the Cycler concept will gain great advantage over direct round-trip transfer from Earth-to-Moon because of the ability of the Cycler to be made very large, in affordable increments, and thereby provide radiation protection for astronauts in transit, propellant depot capability (ultimately cryogenics), and reusable life-support facilities. It was pointed out that
the two-Cycler system recommended here is particularly amenable to incremental growth and efficiency because of the ability of the two Cyclers to rendezvous with each other and join, if desired, into a larger station while a third Cycler takes the now empty place of one of the first
two.”

I am completely lost in terms of understanding the math in this paper and for all I know it is some clever April fools joke. Or….Dr. Rendezvous may have actually had a hand in it and it is in fact a way to build a semi-permanent superhighway-in-cislunar-space between the Earth and the Moon.

With this kind of Cycler a small capsule can be used and the personnel make the two week journey (sorry I thought it was only a week) in a large cislunar transfer vehicle that need not expend large amounts of propellants or aero-brake.
You and Mr. Lavoie might want to review the paper.

It would be interesting to have available an update at that level of the effects of the proposed increased commercial participation (if it ever materializes) on costs and schedules.

Presumably either money would be saved or the schedule could be compressed.

If manned, this base will provide the currently unavailable data on what the actual effects of prolonged exposure to 1/6g gravity is. Until we have this data we do not know how much gravity is required for humans to thrive. We know ~0g is too low and 1g is sufficient. What about 0.95g? 0.5g? 0.1g?

It is premature to exclude all natural bodies. Especially since we likely will need to setup a base on one (the moon) to get the resources to build the orbital structures.

Unlike science, in engineering there is not one correct answer but a continuum of possible answers with advantages/disadvantages to each. The trick is to pick the “best one” (always continuous) then stick with it.

My reservations about various other orbital propellant depot proposals has always been that they assumed the depots to be free, while assuming large costs for developments of HLV’s.

The Spudis/Lavoie proposal is the first and only study (with which I am familiar) to make a good faith effort to cost the orbital propellant depot system it proposes.

What about Lunar Cyclers? Using Cyclers a small capsule can intercept near Earth and a week later the crew can transfer to a Lander that intercepts near the Moon. Only a small capsule is needed and a small lander for the intercepts and return to Earth and the Moon.

The Cyclers can also be heavily shielded against radiation while capsules and Landers cannot. The week long transit would thus entail far less dosing.

I strongly believe Gerard K. O’Neill stepped outside the discussion loop and did the major “rethink” by going after colonization as the ultimate aim of all space activities. One reason I so strongly dislike NewSpace is the complete reverse of O’Neill’s concepts by proposing Mars as a second home for humankind. This was one of the first problems addressed by O’Neill when his group ruled out any natural bodies on the basis of human biology (the requirement for 1G).

“First, we need to understand and articulate true choices so people can understand and evaluate the different approaches and requirements.”

A couple years ago I wrote about “The Parker-Dyson-Spudis continuum” which starts with radiation, continues with the only system capable of pushing a massive cosmic-ray-water-shield around the solar system, and finishes with the only place to acquire that water. The public does not understand dosing and debilitation, the rocket equation, or how absolutely necessary the Moon is if we are to expand off-world. One way to articulate this is the infographic I frequently refer to which shows the energy required to escape the lunar gravity well as 23 times less than Earth.

“Second, we need to develop architectural approaches that fit the requirements for fiscal and political “sustainability.”

The only architecture that mattes is a state sponsored program of Super Heavy Lift Vehicle launches with the goal of creating a cislunar infrastructure. LEO and Mars are dead ends.

And third, in terms of leadership, we have Bridenstine. Which is the only good thing that has happened for a very long time.

The Blue Moon Lander concept fascinates me and I wonder if the solution might be found in this vehicle by making it the “universal space tug” by having it dock with whatever needs to be boosted somewhere. Along with this tug would be hydrogen (or possibly methane) and oxygen cells that could be added and removed as needed.

Develop Cislunar Space Next

Develop Cislunar Space Brochure

Powerpoint version of Lavoie and Spudis (2016)

If you actually read the 2016 paper, you will see that science is a very minor part of it — it mostly deals with engineering and national space policy.