Massive Martian dust storm endangers NASA rover • Hacker News Board

Re: Massive Martian dust storm endangers NASA rover

#51

Post by yongjik » Fri, Jun 15, 2018, 8:00 PM UTC

nitrogen wrote: post #45

namibj wrote: post #43

Earlier quoted context omitted.

I still wouldn't want that much U-235 in a critical configuration in my home. If something goes wrong, I'm not a superfund site, I'm the reason why someone started WW3/why my neighbourhood is no more.

Why would it explode? Don't you need high purity and high compression with perfect timing for that? Wouldn't it just get really hot in a reactor design?

Frankly I'd be more worried about "passive heat pipes filled with liquid sodium" (read: "pipes filled with substance that transmutes water to fire"). Not in my backyard.

Re: Massive Martian dust storm endangers NASA rover

#52

Post by elihu » Fri, Jun 15, 2018, 9:10 PM UTC

zaarn wrote: post #34

elihu wrote: post #15

Earlier quoted context omitted.

The article doesn't say what the exact power drop is, but it appears to have been at least 75%: > Within days, Opportunity saw sunlight dimming as atmospheric opacity — a measure of how much dust is in the air — soared. The rover’s energy production dropped by half over the course of 2 days, and then half again in a single day, Callas said during a media briefing on 13 June. Aside from nuclear, some reasonable mitiga…

Overprovisioning probably won't help. The power drop isn't 75% it's nearly 100%. The last image transmitted is pitch black only the camera's sensor introducing some noise during the long exposure to be visible. The mitigation is either "lots of batteries" or "have a (nuclear) generator and power down" because solar will not produce anything under the currently present conditions. (Well not "nothing", it's generating…

Yeah, that's a good point; I saw that later in another comment that illumination on the ground was almost nothing.

I guess burning rocket fuel for electricity/heat is probably the most practical mitigation. I expect it would be tremendously inefficient, but better than freezing due to a once-a-decade dust storm.

Lots of batteries or nuclear could also work if it's available.

Re: Massive Martian dust storm endangers NASA rover

#53

Post by azernik » Fri, Jun 15, 2018, 9:29 PM UTC

nitrogen wrote: post #45

namibj wrote: post #43

Earlier quoted context omitted.

I still wouldn't want that much U-235 in a critical configuration in my home. If something goes wrong, I'm not a superfund site, I'm the reason why someone started WW3/why my neighbourhood is no more.

Why would it explode? Don't you need high purity and high compression with perfect timing for that? Wouldn't it just get really hot in a reactor design?

In order to get a full-yield nuclear detonation, yes, but even a "fizzle" still has the power of a good-size conventional bomb.

Re: Massive Martian dust storm endangers NASA rover

#54

Post by namibj » Sat, Jun 16, 2018, 8:55 PM UTC

nitrogen wrote: post #45

namibj wrote: post #43

Earlier quoted context omitted.

I still wouldn't want that much U-235 in a critical configuration in my home. If something goes wrong, I'm not a superfund site, I'm the reason why someone started WW3/why my neighbourhood is no more.

Why would it explode? Don't you need high purity and high compression with perfect timing for that? Wouldn't it just get really hot in a reactor design?

A criticality event is _bad_. If you are near it, you get cancer. And there are many ways a small nuclear reactor can malfunction without that much yield, and still ruin my neighbourhood. I have to agree, the crater is the worst case.