[Throwawayaerlei]

Thanks for the general info ... have we found any caves on or in the moon?? And the reference, just skimmed it but it appears to be written at a high and thorough level.

But I wasn't clear about my real question: is there a shield planned for the Orion spacecraft to keep astronauts alive during a sufficiently bad solar event on a trip to or from the moon? As I recall the lunar orbiting space station was going to be unmanned but I was wrong or they've changed their minds: https://www.nasa.gov/gateway So they've got to be thinking about this problem, and as the reference notes we'll need for example adequate space weather surveillance which I note we've been emplacing as of late.

I've never checked it out like running the numbers but I've heard for a long time Apollo was timed for a low part of the solar cycle and one reason Nixon cut it short was because delays put those canceled missions into the active part of the cycle.

[robomartin]

> is there a shield planned for the Orion spacecraft

Not sure what they are using in Orion. The general answer is that, yes, there has to be a shield. Historically that has been aluminum. Mass is a huge problem in going to space. Because of this, you can't have the shield you really want.

Over the years we have learned that thick laminated (under heat and pressure) polyethylene is a better space radiation shield than aluminum and at a significant savings in weight.