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NASA's Perseverance rover sends stunning images

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Re: NASA's Perseverance rover sends stunning images

#211

Post by sgt »

idlewords wrote: post #200
marshmallow_12 wrote: post #52

Earlier quoted context omitted.

a glowing green sandwich covered in red sand. But seriously, this stuff is powering those voyager probes 40 years later. Which makes me ask: why do we have to send there technologies 10 billion miles away to make them work? Why can't my fridge be powered this way?

The Russians tried powering a bunch of remote stuff with plutonium batteries during the Soviet era. It did not end well, and cleaning those up has been an ordeal. Pu-238 was also used in pacemakers. The basic problem is just that plutonium is toxic as hell.

No no.. My grandfather from Irkutsk oblast had plutonium heart, and he live to long ripe age of 45! Almost unheard of in Soviet union.

Re: NASA's Perseverance rover sends stunning images

#212

Post by Cthulhu_ »

reilly3000 wrote: post #208
Balgair wrote: post #113

Earlier quoted context omitted.

Generally, these cameras are many years out of date. They don't load up the rovers with the latest gear from today, but with the latest gear from when the design review process was closed. I don't know when that was for Perseverance, but it would not surprise me if that was a decade ago. The cameras are also not specifically designed for image capture, but for scientific study. In that they take images at a wider ran…

Yep, that’s the same reason why it runs on a PowerPC750 chip. They cost $200k+ for under 200Mhz on a 150-250 nm process, but can withstand up to 1,000,000 rads of radiation and function within extreme temperature ranges for decades. They have been proven to work in the harshest environments on prior missions, and the risk of an unproven processor is giant; a CPU failure could jeopardize the mission just as much as a…

Especially since hardware is generally designed for speed and performance instead of reliability. Didn't NASA use a lot of 486es for a long time for this same reason?

But yeah. It's not a problem if a CPU gets buggy or dies in a datacenter with 10K similar ones, because of redundancy and a completely different approach to software workloads nowadays. I mean a lot of production systems barely even care what CPU they run on.

And ~200 Mhz is still powerful enough for a LOT of applications.

Re: NASA's Perseverance rover sends stunning images

#213

Post by Johnny555 »

marshmallow_12 wrote: post #52
11thEarlOfMar wrote: post #44

Stupid question, but where is Perseverance's energy source? Answer: Plutonium It powers a Multi-Mission Radioisotope Thermoelectric Generator. The plutonium decays at a few % per year, so that means it should be able to bring Elon a sandwich when he lands. https://mars.nasa.gov/mars2020/spacecraft/rover/electrical-p...

a glowing green sandwich covered in red sand. But seriously, this stuff is powering those voyager probes 40 years later. Which makes me ask: why do we have to send there technologies 10 billion miles away to make them work? Why can't my fridge be powered this way?

Why can't my fridge be powered this way

The MMRTG is a cylinder 25" in diameter and 26" high, it's going to seriously impact space in your 'fridge. Plus it weighs nearly 100 lbs.

It outputs around 100W of power, which might be enough for a small refrigerator, but it also emits around 2000W of thermal energy, so your kitchen's going to get a little warm (probably a good thing in the winter, not so much in summer).

Though probably the biggest drawback is the cost -- the MMRTG costs around $100M to manufacture. The US Department of Energy makes the plutonium for it.

Re: NASA's Perseverance rover sends stunning images

#214

Post by wiz21c »

reilly3000 wrote: post #208
Balgair wrote: post #113

Earlier quoted context omitted.

Generally, these cameras are many years out of date. They don't load up the rovers with the latest gear from today, but with the latest gear from when the design review process was closed. I don't know when that was for Perseverance, but it would not surprise me if that was a decade ago. The cameras are also not specifically designed for image capture, but for scientific study. In that they take images at a wider ran…

Yep, that’s the same reason why it runs on a PowerPC750 chip. They cost $200k+ for under 200Mhz on a 150-250 nm process, but can withstand up to 1,000,000 rads of radiation and function within extreme temperature ranges for decades. They have been proven to work in the harshest environments on prior missions, and the risk of an unproven processor is giant; a CPU failure could jeopardize the mission just as much as a…

Could you explain why such a processor is 1000x more expensive than a non-rugged one ? I mean, considering the future of earth, I'd certainly welcome a processor that could withstand a lifespan of decades (including the harsh "I'm going to unsolder it to put it in another device" environment).

Re: NASA's Perseverance rover sends stunning images

#215

Post by Alghranokk »

watersb wrote: post #104
perardi wrote: post #95

Earlier quoted context omitted.

People are probably going to answer “safety”. But it’s also hideously expensive. Plutonium is, apparently, one of the safer ways to build these things, because it is easy to shield, and the power density is good. But plutonium, as it’s not naturally occurring, is stratospherically expensive. https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...

The first nuclear bombs cost billions of dollars each. I wish I could say that’s a good thing. But no, after the first of them, nuclear weapons seem to have justified their own existence, no matter the cost. I would rather see remaining weapons material repurposed as deep-space power sources. If that were to solve problems. Anyhow, Perseverance makes me happy.

> I would rather see remaining weapons material repurposed as deep-space power sources. If that were to solve problems.

Unfortunately this is not possible, nuclear weapons make use of pu-239, which has properties that does not make it a useable RTG fuel.

Re: NASA's Perseverance rover sends stunning images

#216

Post by junon »

btilly wrote: post #84
junon wrote: post #70

Earlier quoted context omitted.

Do you have an answer that isn't speculation or something you concluded from a breezy stroll over to Wikipedia? Stop mocking questions. It solves nothing.

Each Mars Rover uses 5 kilograms of plutonium 238. (Plutonium 239 is the one that is used in nuclear bombs.) Per https://www.wired.com/story/nasas-mars-rover-will-be-powered... we currently have a lab dedicated to producing it, and it makes 3.5 pounds per year. Per https://www.npr.org/2011/11/08/141931325/the-plutonium-probl... the cost of getting the lab restarted was a bit shy of $100 million. And once running full…

Thanks for the info, interesting.

Though FWIW I was more commenting on the mocking of a legitimate question. Not everyone has the same background as everyone else. There are no stupid questions.

Re: NASA's Perseverance rover sends stunning images

#217

Post by maaaaattttt »

mojomark wrote: post #99

What are the "dark spot anomalies" that appear to be floating in the air in some images (1, 2)? Dust on the camera lens? I've never looked at any rover images so I assume someone knows. Also, whay are the images fairly low resolution compared to a phones camera. Does it have to do with image data transmission error? Finally (then I'll shut up), when do we get to see the stereo images? I want to see these on my Vive.…

My wild guess would be dust on the lens. Quickly looking at related images shows black spots present at the same locations relatively to the image's frame.

Re: NASA's Perseverance rover sends stunning images

#218

Post by antientropic »

ddingus wrote: post #85
nitrogen wrote: post #74

Earlier quoted context omitted.

AKA "Not In My Back Yard." So the question stands and extends to include this: "why not?"

Risk? That is my basic opposition. Happy to be flexible on energy in almost every way. Cost, type, uptime... But error with nuclear tech tends to endure for a very long time. Fukushima will be raising ocean radiation for a long time, just one example. These are many lifetime events. Some minor, or recoverable, some profound. Given we can reasonably run the fridge on solar, and other tech, that risk does not seem to m…

> Fukushima will be raising ocean radiation for a long time, just one example.

Will it? The ocean is very, very big. Contaminated water from Fukushima is a literal drop in a bucket.

Re: NASA's Perseverance rover sends stunning images

#219

Post by ben_w »

wiz21c wrote: post #214
reilly3000 wrote: post #208

Earlier quoted context omitted.

Yep, that’s the same reason why it runs on a PowerPC750 chip. They cost $200k+ for under 200Mhz on a 150-250 nm process, but can withstand up to 1,000,000 rads of radiation and function within extreme temperature ranges for decades. They have been proven to work in the harshest environments on prior missions, and the risk of an unproven processor is giant; a CPU failure could jeopardize the mission just as much as a…

Could you explain why such a processor is 1000x more expensive than a non-rugged one ? I mean, considering the future of earth, I'd certainly welcome a processor that could withstand a lifespan of decades (including the harsh "I'm going to unsolder it to put it in another device" environment).

From this list, I assume the isotopic purity is the biggest contribution to the price, though I expect relative lack of mass production doesn’t help: https://en.m.wikipedia.org/wiki/Radiation_hardening

Re: NASA's Perseverance rover sends stunning images

#220

Post by TeMPOraL »

wiz21c wrote: post #214
reilly3000 wrote: post #208

Earlier quoted context omitted.

Yep, that’s the same reason why it runs on a PowerPC750 chip. They cost $200k+ for under 200Mhz on a 150-250 nm process, but can withstand up to 1,000,000 rads of radiation and function within extreme temperature ranges for decades. They have been proven to work in the harshest environments on prior missions, and the risk of an unproven processor is giant; a CPU failure could jeopardize the mission just as much as a…

Could you explain why such a processor is 1000x more expensive than a non-rugged one ? I mean, considering the future of earth, I'd certainly welcome a processor that could withstand a lifespan of decades (including the harsh "I'm going to unsolder it to put it in another device" environment).

Part of it is low demand, so you don't benefit from economies of scale. Also the customers buying this type of equipment are able to bear such costs. They aren't gonna haggle over $100k on a critical component to a $3B mission.
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