Comment by robomartin | Hacker News Reader

Comment by robomartin | Hacker News Reader

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> I was promised a path to Mars with boots on the Moon two years ago.

We did some work on a camera system for the Artemis project. It will hopefully make it to the moon's surface by the third mission. Also worked on spacecraft going to the ISS.

I don't think people --including most engineers-- have a good grasp of just how difficult it is to make anything going to space, much less anything that involves people.

The simplest statement I can make is:

Everything is trying to kill you and your hardware 100% of the time.

Leave the protection of the magnetosphere and things get much worse.

Designing safe and reliable systems to go to the Moon or Mars is complex and hard to nail down to a schedule. This isn't like a software startup where you can deliver half a product and iterate (or even execute a full pivot) over time. You have to get it right or things fail in spectacular ways and people die.

Imagine having to deliver your Social Media, online commerce or SaaS product with a full 100% working set of required features, non-trivial failure tolerance and uptime guarantee, or (to be dramatic) your entire family dies. A bit out there? Not so sure.

"Everything is trying to kill you and your hardware 100% of the time.

I was appalled when I learned about LEO atomic oxygen.

"Leave the protection of the magnetosphere and things get much worse."

Anything in the Orion to deal with the latter for the not rad hard humans? Or is this another Apollo Program timed with the solar cycle (which due to delays cut the latter short)?

> Anything in the Orion to deal with the latter for the not rad hard humans?

Well, GCR's (Galactic Cosmic Rays) will go through just-about anything. I think I remember an experiment that measured penetration in water to over half a mile (800 meters). As such, all you can do is manage exposure...you are not going to stop them. On the moon one of the ideas is to pile-up regolith (moon dirt) to create better protection. Without that you would need to transport more material out there than might be possible.

I am not aware of what long-term plans might look like today. I guess is that the ideal habitat will likely take the form of repurposing the rocket to become living quarters and bury it under as much regolith as it might be able to support. Of course, that implies suitable construction equipment to be available. I doubt astronauts are going to shovel the stuff at that scale.

In terms of electronics, you try to keep things powered down to the extent possible. Circuits can self-destruct very quickly if powered-up. An unpowered circuit is less likely to suffer the same kind of damage.

Beyond that, critical systems are typically designed to a fault-tolerance (FT) level. A single fault tolerant system can have one failure and still operate within mission parameters. You could have 2FT systems that will run after two failure. Because mass is important in going to space, FT doesn't necessarily fully duplicate a system (for example, triplicate copies of a system to be able to survive two failures). These days deeper analysis is possible and enhanced fault tolerance can be applied to selected functional units. At the end of the day, the most important thing is to test, test, test.

NASA has a lot of publicly-available resources about this and more. Chapter 3 of this one has an overview of protection from space radiation:

https://www.nasa.gov/sites/default/files/atoms/files/sf_radi...

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.

> 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.

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