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NASA's Perseverance rover sends stunning images

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Re: NASA's Perseverance rover sends stunning images

#171

Post by serf »

matheusmoreira wrote: post #126
khuey wrote: post #111

Earlier quoted context omitted.

Alpha sources outside the human body are of little health concern. You'd have to break it open and eat the plutonium inside for it to be a serious risk.

> You'd have to break it open and eat the plutonium inside for it to be a serious risk. Yes. Sounds like something a child would do.

aside from the fact that 'breaking open a refrigerator' doesn't remotely sound like something a child would ever do to me, let's assume the worst and the child somehow opens up a refrigerator.

a conventional fridge has electric motors/pumps , live a/c wiring, and gas under pressure. It's not radiation-spilling-everywhere unsafe, but it's not really safe for the kid, either.

Re: NASA's Perseverance rover sends stunning images

#172

Post by matheusmoreira »

scoopertrooper wrote: post #162
khuey wrote: post #111

Earlier quoted context omitted.

Alpha sources outside the human body are of little health concern. You'd have to break it open and eat the plutonium inside for it to be a serious risk.

How familiar are you with the human species? There have been several notable accidents where humans have cracked open medical machines and decay powered lighthouses to exactly this effect. Imagine if you started whacking plutonium in consumer products!

> There have been several notable accidents where humans have cracked open medical machines and decay powered lighthouses

Indeed.

https://en.wikipedia.org/wiki/Goi%C3%A2nia_accident

A caesium-137 radioactivity source was left behind and eventually stolen. The thieves successfully dismantled it despite sustaining severe injuries in the process, exposing the radioactive material contained in the shielded capsule. They were fascinated by the strange light emitted by it.

Eventually it was sold to a scrapyard. The owner also became fascinated with the blue glow. He brought the thing home to show everyone. He distributed parts of the material to friends and family. Eventually sold it to another scrapyard but not before his brother took some of the beautiful radioactive dust and smeared it on the concrete floor. Where his daughter sat and ate a contaminated sandwich. She also applied he powder on her own body.

The only reason this unfortunate chain of events stopped is the scrapyard owner's wife noticed everyone was getting sick and notified the authorities. She died later along with the girl. Attempts to bury the child also led to a riot. Scrapyard workers also died attempting to extract the lead from the radiation shielding component.

Re: NASA's Perseverance rover sends stunning images

#173

Post by 0xfaded »

waheoo wrote: post #96
khuey wrote: post #81

Earlier quoted context omitted.

The radiation emitted by plutonium 238, which is what's found inside RTGs, is easily shielded by essentially any solid material. The real reason you don't want an RTG powering your fridge is that it costs on the order of one million dollars per watt.

Economies of scale would surely change that though?

I was thinking it would be fun to buy some uranium 238 (you can have up to ~7kg of it without a license). Then I tried ddg'ing what it would cost to dispose of. I couldn't find an answer, so I decided buying uranium wasn't a good idea.

It's hard enough getting rid of an old lead-cell battery.

Re: NASA's Perseverance rover sends stunning images

#174

Post by matheusmoreira »

serf wrote: post #171
matheusmoreira wrote: post #126

Earlier quoted context omitted.

> You'd have to break it open and eat the plutonium inside for it to be a serious risk. Yes. Sounds like something a child would do.

aside from the fact that 'breaking open a refrigerator' doesn't remotely sound like something a child would ever do to me, let's assume the worst and the child somehow opens up a refrigerator. a conventional fridge has electric motors/pumps , live a/c wiring, and gas under pressure. It's not radiation-spilling-everywhere unsafe, but it's not really safe for the kid, either.

That refrigerator is discarded. It ends up in a scrapyard. Someone comes, sees the shielded capsule containing radioactive material and harvests the lead. The remains are eventually sold to someone else and it ends up in that person's home where children are likely to become fascinated by it or even eat it.

Everyone who went near this thing is likely to become ill at the very least.

Re: NASA's Perseverance rover sends stunning images

#175

Post by ChuckMcM »

ttul wrote: post #166
ChuckMcM wrote: post #75

Earlier quoted context omitted.

Not a nuclear engineer, but we covered this in my third semester of physics at University. The short answer is there isn't any engineering reason why you can't do this. The "real" reason is that there is liability here that nobody knows how to deal with. If the unit became damaged and its shielding failed it could sit there and kill people who came near it for years (for example). I got to talk to one of the engineer…

Plus the 90kW of waste heat would keep you very warm.

So true, of course if I lived in a place where it snowed I would put water pipes under the sidewalks and driveway and recirculate water through them and a heat exchanger near the reactor. Voila, no more shoveling snow!

Re: NASA's Perseverance rover sends stunning images

#176

Post by yread »

khuey wrote: post #81
AnimalMuppet wrote: post #54

Earlier quoted context omitted.

What's powering Voyager is a plutonium pile. Pretty sure you don't want that in your fridge. 10 billion miles from me? Sure, knock yourself out. 10 feet from me? No way.

The radiation emitted by plutonium 238, which is what's found inside RTGs, is easily shielded by essentially any solid material. The real reason you don't want an RTG powering your fridge is that it costs on the order of one million dollars per watt.

Plutonium is also highly (chemically) toxic.

Re: NASA's Perseverance rover sends stunning images

#177

Post by imhoguy »

khuey wrote: post #81
AnimalMuppet wrote: post #54

Earlier quoted context omitted.

What's powering Voyager is a plutonium pile. Pretty sure you don't want that in your fridge. 10 billion miles from me? Sure, knock yourself out. 10 feet from me? No way.

The radiation emitted by plutonium 238, which is what's found inside RTGs, is easily shielded by essentially any solid material. The real reason you don't want an RTG powering your fridge is that it costs on the order of one million dollars per watt.

And recycling en masse would be nightmare. We got anough hassle with R* gases.

Re: NASA's Perseverance rover sends stunning images

#178

Post by dmix »

antmldr wrote: post #123
gtm1260 wrote: post #87

Stupid question maybe but like is there a reason the picture quality seems worse than a decent dslr photo? I'm so curious what that photo would look like, taken with an everyday camera, without the bizarre 'scientific' look of these shots.

Scott Manley recently did a pretty good ELI5 on the topic: https://www.youtube.com/watch?v=Wah1DbFVFiY

It takes 15min but this plus the comment section on CMOS (can’t link directly) is excellent. The other comment about being made a decade ago is also relevant and accurate. They will certainly be better next time with evolutions in camera tech thanks to smartphones.

TLDR worth a listen

Re: NASA's Perseverance rover sends stunning images

#179

Post by asaddhamani »

akg_67 wrote: post #168
whatever1 wrote: post #155

Anyone has insights on how data in such volumes can be transferred from Mars to Earth in the absence of a direct link? Do the intermediate nodes have gigabytes of available storage to emit data to the next available node once it becomes visible ?

Reddit had AMA with engineers from this mission, IIRC last week. They provided good info on different aspects including how they were able to get video over low bandwith connection, including various mission site link for more info. You might want to check out AMA for your question. Edit: added following links This Q&A about storage https://www.reddit.com/r/IAmA/comments/lpzbzo/were_scientist... These Q&A about data…

Do you have a link to this AMA?

Re: NASA's Perseverance rover sends stunning images

#180

Post by adrianN »

khuey wrote: post #111
matheusmoreira wrote: post #109

Earlier quoted context omitted.

> easily shielded by essentially any solid material If that shield fails for any reason, including tampering, you're looking at the radiological contamination and likely deaths of everyone nearby at the very least.

Alpha sources outside the human body are of little health concern. You'd have to break it open and eat the plutonium inside for it to be a serious risk.

Plutonium dust is very dangerous and you don't want to be around the decay products either. Plutonium also likes to catch fire.
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