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For GW Johnson re Artemis II Space Tug concept....
The Interim Upper Stage is cryogenic .... it is intended to be used immediately after the first stage falls away, and I'll bet the mission plan calls for nearly continuous use until fuel is exhausted, at which point the Orion capsule and service module would be on their way.
The Space Tug concept would require Interim Upper 'Stage to hold onto it's cryogenic propellants for several days, so it can be used to decelerate as the vehicle approaches Earth.
The threat of boil off can can be addressed with sun shades, but those are not part of the current mission plan.
(th)
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For GW Johnson re Starship as possible Space Tug for Artemis II
https://www.google.com/url?sa=i&url=htt … AdAAAAABAE
If the link above works, it will show a side view of the funnel shaped adapter that is needed to allow use of the 5 meter diameter Interim Second Stage.
The Space Tug will need the same adapter to dock with the Interim Second Stage, adapted for the Starship diameter.
(th)
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Could be a simple bar truss. The Russians did a lot of those. Bars shipped up as bundles in payload bays, then snapped together in space by means of appropriate snap joints.
But you still need a way to refuel the Interim Upper Stage (IUS) on-orbit, before it departs to send the cluster to the moon. Why? Bigger cluster. It needs more dV than it has left after reaching LEO, in order to put an Orion/service module (and maybe a small lander) into low lunar polar orbit. The service module can get Orion back onto the trip home, from that low lunar orbit, but it cannot get both into and back out of low lunar orbit. It is too small.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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GW Johnson notified me by email that an article about Space Tugs is now available at his exrocketman blog site:
https://exrocketman.blogspot.com/
NewMars members should have no difficulty following the presentation.
(th)
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