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It's about time. Engineering decisions shouldn't be made based of irrational fears of general population. If nuclear power plant is best option for space missio
by sp0ck 9y ago
It's about time. Engineering decisions shouldn't be made based of irrational fears of general population. If nuclear power plant is best option for space mission we should use it.
- mikejb 9y agoI agree. Though we might disagree on where legitimate concerns end and irrational fears start. It is also non-trivial to decide (and argue around) what a 'best option' is without defining a scale of what 'good' and 'bad' would be, and what factors are considered in that scale, and which ones are left out.
- Ntrails 9y agoCan we start by agreeing on whether or not we care about a nuclear reactor going "pop" on mars pre-colonisation? Because, you know, there's a chunk of me that thinks we can be less risk averse in trying to do things on an uninhabited planet. Nuclear meltdown is pretty awful on earth, on Mars I don't see it with the same fear. I also feel like this is not dissimilar from dumping rubbish in the neighbours yard because who cares it's not mine but on a planetary scale. Which seems bad but I want to rationalise it away and say "but this is different".
- kobeya 9y agoThe concern was never about a nuclear reactor having a failure mode on Mars. It was about the rocket carrying the nuke having a failure mode and spewing radioactive fuel over central Florida.
- Symmetry 9y agoBefore a rector is turned on the inside of it isn't particularly radioactive. In order to last from the creation of the solar system to the present day uranium had to decay very slowly when not in a critical mass, specifically U235 has a half life of 700 million years. So it's really the radiation of uranium that you have to worry about if you find yourself in a room with a hunk of it but the toxicity. Still, people made cookware with uranium in the glaze and managed to avoid killing people. Now, as soon as you turn the reactor on you start turning the relatively safe U235 into all sorts of nasty things with half lives that are much, much shorter than 700 million years like strontium 90 with a half life of 30 years. That stuff is indeed horrible and getting it spread over Florida would be a disaster. But the solution is to make sure you don't turn the reactor on until it's safely in orbit. That makes them much safer than the RTGs we've been using to power space probes far away from the sun previously. Because the P238 isn't in a critical mass it has to be a synthetic isotope with a low half life in order to generate enough heat to power a spacecraft when it's outside a reactor and would be quite deadly if you interacted with it without shielding.
- mathw 9y agoSure it's not in critical mass or particularly radioactive, but Plutonium is toxic...
- wbl 9y agoSo is hydrazine and dinitrogen tetroxide is also all kinds of fun. Heavy metal toxicity is manageable.
- DennisP 9y agoNASA's Kilopower design uses enriched uranium fuel, and with such a small reactor it won't be much uranium.
- Symmetry 9y agoI'd expect that part of the reason they use uranium instead of plutonium is exactly to make sure the reactor is safe in the event of a rocket failure.
- mrep 9y agoI expect it to be because there isn't much plutonium left [1]. [1]: http://www.popsci.com/plutonium-238-is-produced-in-america-for-first-time-in-30-years http://www.popsci.com/plutonium-238-is-produced-in-america-f...
- kobeya 9y agoNot saying it was unfounded fear (I'm very pro space nuclear power), just pointing out what the actual contention is. People have an adverse reaction to anything with the word "nuclear" on it, even more so when it is put on top of a half million pounds of propellant and lit with a non-negligible failure rate. The reality though is that failure of the rocket doesn't mean the reactor or fuel is vaporized and thrown to the wind. It's possible to construct the payload fairing to survive sudden, rapid disassembly and crash land intact off the Florida coast for recovery.
- davedx 9y ago> uninhabited planet By humans. By other life-forms is yet to be proven one way or another. There is already discussion of treaties to prevent contamination of any Mars biosphere by human missions there. Also: what about the future? There's no point in sending a nuclear reactor to Mars if a future colonisation mission can't go ahead because the reactor has melted down... Solar irradiance is approximately 50% less than on Earth. PV with high efficiency modules (the same ones they use on satellites) is also viable. I wonder if anyone has run the numbers on the cost of shipping a reactor Vs. the cost of shipping a football field of PV modules there.
- Retric 9y agoIt's solar plus batteries which have been used for rovers for a long time, but simply weigh more and have a relatively short lifespan. Especially when you consider how useful 'waste' heat is on a planet that gets that cold. As to contamination, it's a planet we did not abandon earth when Chernobyl melted down. Worst case nobody goes within 100 miles of it for a few decades. But frankly people are unlikely to go to 99% of Mars anytime soon and can't walk outside without significant protection anyway.
- londons_explore 9y agoInstalling/laying out a football field of modules sounds rather tricky, as does keeping them clean (mars is dusty and windy). I assume the nuclear reactor would be a pretty much "sealed unit" which just needs to get rid of a lot of heat. There is no reliable water/evaporative cooling on mars, nor is the atmosphere thick enough for fans etc. to be effective. Instead it will need huge thermally emissive panels. For them to be effective, they need to be very hot.
- Retric 9y agoDumping heat into the ground is another option. But, generally keeping things warm is going to be a larger issue than keeping things cool unless they are producing crazy amounts of power. Further, the atmosphere might only be 1% of earth's but when the temperate averages -60C you can still use it to passively dump heat without needing vast radiators.
- tiku 9y agoI don't thinnk it was the fear of the general population, because what influence do we have on dangerous endeavors? If the scientist can do it safely, they could just do it. It must have something to with the state of technology and not being able to do it safe until now.
- danpalmer 9y agoI disagree. Nuclear reactors have been very safe for a long time now, but between high profile incidents with old reactors, the link with nuclear weapons, and misinformation, the public perception is that they are unsafe.
- mikejb 9y ago"very safe" might be true (your interpretation of 'very' might vary), but it is a low chance/high price kind of thing. I live in Bavaria, and hunters here still need to take precautions due to Chernobyl, some 31 years later.
- DiThi 9y agoIt's very safe if you don't disable safety systems put in place (like it was explicitly done in Chernobyl to do dangerous experiments, even though they labeled it as "routine tests"). And if you don't ignore many warnings given in the industry (like TEPCO ignoring many recommendations of raising their tsunami protection walls many years before the catastrophe, like other plants closer to the epicenter that were unaffected). So the chance is much lower than people think, if plans have measures to avoid such corruptions. And that's not counting the many safer designs we have nowadays. Many plants today don't even need backup electricity to automatically shut down by themselves.
- mikejb 9y agoI fully agree that newer designs are safer, but ignoring the human factor in the equation is IMO not very reasonable. Without the human factor, driving a car is very safe. That argument is valid, but it doesn't reflect reality.
- simias 9y agoI agree with your sentiment but let's face it, sending humans to Mars is as much PR as it is scientific research (maybe even more). Look how we ended up on the moon in the first place. If NASA wants to get the funding it has to make it as marketable as possible. If there's a big push back from the general population it will be hard to convince the politicians to invest billions in an unpopular project with no short-term dividends.
- krasin 9y agoOn a related note, I very much like the fact that "The Martian" movie uses RTG as a life saving device and the best car climate control ever. It helps with the public perception that it's not that dangerous.
- nkrisc 9y agoGenerally I agree with you, but I don't know if it's wise to promote the unintended use of a device by a fictional character as a last hope in a dire survival situation as the bar for what's "safe". Regardless of whether it's actually safe, showing me it's safe enough to sit near in a situation where one would probably die anyway isn't exactly comforting.
- tehwalrus 9y agoI would say, given the state of politics and the general attitude to the climate and natural resources, our first priority should be colonising another planet. Putting some scientists on Mars for a few years is step 1 in that very important insurance scheme!
- mtgx 9y agoAre the nuclear reactors we're transporting to Mars safe in case of rocket explosion? Because rocket explosions/failures happen way more often than Fukushima type situations.
- valuearb 9y agoYes, it's been much tested. They aren't operational until they make orbit.
- MichaelMoser123 9y agoIrrational fears? What are the chances of the rocket launcher blowing up with the reactor? How would we compute the fallout range as a function of altitude of the blast?
- freehunter 9y agoDo you know how much nuclear material we've launched into space? Hint: a lot.
- DennisP 9y agoIrrational because a uranium fission reactor contains very little radioactivity before you start running it.
- tajen 9y agoPlease at least tape it! A nuclear reactor mounted on a gigantic explosive sounds like a stupid idea once you count this risk, but even if we did it, would it be among the most stupid things we did?
- yongjik 9y agoAccording to Wikipedia, "some granites" contain 10 to 20 ppm of uranium, and the density of granite is about 2.65 g/cm^3. If a rocket contains 10t of pure uranium, that is the same amount of uranium in a cube made of uranium-rich (20 ppm) granite, each side about 57m long. Now imagine how many such cubes would fit inside your favorite mountain.
- gene-h 9y agoSo that's the beauty of it being a nuclear reactor as opposed to an radioisotopic thermoelectric generator. An RTG will be very radioactive at the time of launch, a nuclear reactor need not be. As long as one doesn't start the reactor before launch by removing the fuel rods, it's practically inert. One might even start the reactor only when the probe is confirmed to be on an escape trajectory from Earth to avoid the possibility of contamination.