Lunar Surface Operations
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Crew Safety and Rescue

The current reference mission shows the crew riding in the Ascent Stage, mounted aside the Descent Stage, during descent to the moon. (As I recall, that brilliant idea came from Vik Olliver, who discovered the solution while building up the 3D CAD models; shows you the value of doing that modeling!)

This side-saddle design for the ascent stage means that the crew can abort back to lunar orbit at any time during descent. The "dead man's curve" goes practically to the lunar surface.  That's the point along the trajectory below which the crew won't have time to abort back to lunar orbit before crashing.  For a nominal descent, it does go all the way to the lunar surface -- it's a question of the descent rate, altitude, and the time it takes for the crew to recognize that there's a problem, react to the problem, get the ascent motor spooled up, and detach the Ascent Stage from the landing stack.

The next scenario is where the crew successfully lands, and there's a problem with the Ascent Stage that prevents them from launching from the moon.  We haven't studied that yet, so let's add that to list of fun studies to do.

Further Studies

What does the crew need to survive on the surface for a week?  A month? Several months?  You'll find data on basic human inputs and outputs in the Artemis Data Book; just trim it down to survival mode.  (Forget about washing clothes.)

What are the possible scenarios that would strand the crew on the surface?  Are they reasonable scenarios?  How many failures are required to create this situation?  Are they plausible failure scenarios?  Is there a body of experience from past use of similar systems that would indicate this is likely to happen?  How likely?

If the crew is stranded on the surface, what do we need to do to get them home for each scenario?

I can think of lots of ways to keep the Ascent Stage from lifting off, even after a successful landing.  Meteorites would be the culprit in many cases; but the probabilities of meteorite damage are so incredibly remote that we probably would not design for this case.  Hard landings are another culprit, though perhaps even more unlikely.  System failures are more likely, but these are Criticality One systems, so they will have lots of built-in safety factors.

Would it be more cost-effective to plan for a potential rescue mission and use a lower reliability factor in the design of the Ascent Stage?  If we did that, how would it affect safety during descent, where an unreliable abort system could spell disaster?

We need to study these things, and we need to document the results of the studies in the Artemis Data Book.  Keep that in mind -- if it doesn't end up in the Data Book, the information is essentially lost, buried in an ever-growing pile of messages about web domains and other kickshaw.

Lunar Surface Operations

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