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Comment by cnlevy | Hacker News Reader

On the contrary, I'm convinced weight can (ab)solve many sins. The JWST's solar shade would have been much less difficult to develop if it wasn't so weight constrained.

> Everything's easy in space until it has to run for three years or more without breaking.

Only 90% reliability ? So let's bring 5 of each, since we're not limited by weight, we get to 99,999%

> there's no good way to analyze air/water for trace volatiles on a spacecraft

How much weights a specialized lab for that ?

> there's no food that stays edible for five years

Its been solved a long time ago: dried and salted food, basically

https://www.atlasobscura.com/articles/ship-food-research-rec...

> Mars mission (by NASA estimates) would need 99%+

There are glaciers on Mars. Its about the only thing they wont have to bring.

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You can bring 100 of something and still be screwed if it turns out to break because of a common cause. You'd think people on this site of all places would understand that reliability engineering is hard.

2. There is no specialized lab for it that works in space. It has to be invented.

3. Astronauts can't survive on ship's biscuit and space MREs. Malnutrition is already a problem on ISS.

4. There are no glaciers between Earth and Mars, and by the way you're not allowed to touch the Martian glaciers because of contamination risk.

On the contrary, the specialized lab for volatiles has been in space for years already on ISS. They bring samples back to prove it works, and it does.

You’re now moving the goalposts from “no food is edible for 5 years” to “MREs don’t count”.

And the trip from Earth to Mars is only like 4 months if you use a BIG ROCKET. :) 4 months without resupply is no huge challenge.

The volatiles analyzer on ISS works against a short list of known compounds. For anything else you just get a generic warning and have to rely on earth labs to figure out what's going on.

You can't subsist on MREs for five years. Here's a cite for you about the space food problem: https://academic.oup.com/jn/article/150/9/2242/5870322

However fast your imaginary rocket goes, you have to wait 26 months for the planets to align so you can use it.

> You can bring 100 of something and still be screwed if it turns out to break because of a common cause.

If it breaks in storage, without been used - yes. If it breaks in use, for reasons related to usage - no.

If your common cause is a 200A electrical fault, no number of spare 100A fuses will help you.

Component level repair is something NASA does actually do on ISS. And Big Rocket allows you to also bring dissimilar redundancy.

No, my point was that even similar redundancy helps. The example of 200A vs. 100A fuse is just an example of something which is not suitable for the problem - like, a tractor on the Moon helps little if you have a broken leg, you need to have medical supplies for that. But with big rocket you could, of course.

Ah, but did you try to put them in parallel? I've heard Apollo-13 crew were in position of necessity to improvise.

Of course its hard, the point that mass margin helps a huge amount is still true. A bigger rocket doesn't provide a solution but it provides a gigantic amount of more solution space and that matters.

Multiple versions and designed to be repairable. Common parts, 3D printers and so on.

We 100% will need to use martian water. Otherwise its impossible to go.

I have never heard of 2) can you provide a link with some information what is actually required?

This paper (Lessons Learned from the Integration of Monitoring Resources in Addressing an ISS Water Quality Anomaly) gives you a good sense of (2), and the resources required to track down mystery volatiles.

https://ntrs.nasa.gov/api/citations/20110012747/downloads/20...

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