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Comment Re:The movie was good because the book was short. (Score 1) 224

If you want to keep "doing the math" and if you want to be called "hard sci fi", you need to do the math right. You can't say that because you've got 50 liters of oxygen that you're going to get 100 liters of water because O2 + 2 H2 = 2 H2O. Yet Weir does exactly that, over and over and over again, mixing up moles, liters, and kilograms. One of dozens of categories of huge fundamental science mistakes that he keeps repeating.

Comment Re: Ban ALL NUKES NOW (Score 2) 127

No. Getting acute radiation sickness is HARD. You have to really work to get it, even in cases of nuclear contamination. The first acute radiation sickness symptoms happen at around 1 Sievert. For comparison, the US lifetime irradiation limit for nuclear power plant workers is 0.2 Sv and two of the most irradiated worker in Fukushima received around that dose (though localized near their ankles) - and this is still 5 times less than the low threshold for acute effects.

Comment Re:Hmmmm (Score 1) 799

Well, this is what you get when you have a project run by rock star developers.

Now it would be better if people were more mature in their communications, but the bottom line is that (a) they're smarter than almost everyone else they know, (b) they know their work better than anyone else and care deeply about it, and (c) they get results. Under the circumstances have no reason to act like grown ups. They're not only rock stars, they're still churning out hits.

It's no wonder that they take the attitude "the world has to take me uncensored, and if anyone doesn't like that then it's their problem." It's a perfectly understandable attitude, but it's not an admirable one. Trying tact first won't necessarily make you more successful, especially if you're a rock star. But it won't make you less successful either; after all if tact fails the option of publicly humiliating someone by showing how much stupider they are than you is still open. What it will make you is a better person.

Comment Re:The movie was good because the book was short. (Score 1) 224

I'm sorry, I missed out where "accuracy" and "popularity" became interchangeable terms. I was responding to a post talking about the book's amazing scientific accuracy, when in reality it's a veritable MST3K of glaring science errors on almost every page. Or at least glaring to anyone who knows anything about the scientific fields involved.

At least with "soft" sci-fi where they don't try to explain how everything works you only get hit over the head with science problems whenever they describe a situation that's literally impossible. With bad pseudo-hard-sci-fi you get hit over the head with it again and again.

Comment Re:Are and storms that fierce on Mars? (Score 1) 112

First, 1KW light output is if you want Earth's equatorial sunlight, which is far more than plants need - they saturate their input at far less than that.

Yes, one has to incorporate a "capacity factor" to account for angles, night and clouds. Something like 15% would be typical for potato-growing regions. But at the same time, when light is coming from LED lighting, you have to account for stray lighting (light that's not hitting your grow area) and efficiencies at generating PAR, which are 20-30% for proper grow lights, lower for normal room lights (as the phosphor wastes part of the light energy to make it a comfortable white rather than a painful pink). The two issues roughly cancel themselves out. You need in the ballpark of 1kW per square meter of electricity input to match normal potato growing conditions.

I arrived at 500W (input) of LEDs to produce the needed output for 1m^2

For 24-7 lighting, that's 50% of my above, but let's go with it.

, and about 2.5m^2 of solar panels to power them up.

Not even close. Your solar array too has a capacity factor - in the ballpark of 15% if fixed, maybe 35% or so if tracking. Then you have your panel efficiencies. The best large scale commercial panels are 22-23% efficiency. You might get 30%-ish if you used absurdly-crazy-expensive spectrolab cells. Then factor in dust constantly settling on the panels - say 25% loss even with regular cleaning. And Mars's solar constant is only 588W/m^2 *in space*. Earth's is about 1kW/m^2 *on the surface*, 1,4kW in space.

As in the book, 500W for lights per square meter would take 67 square meters of panels per square meter of crops. The best possible situation would take 10,5 square meters of panels per square meter of crops.

Note this is using your 500W figure, which is being kind to you. Double the required panel area to reach mine.

yep, 1m^2 per spotlight, 12 per rover (per movie)

Pure nonsense. 6kW of power consumption for LED lights on a rover? Um, no. Never. Period. That's patently absurd, you'd burn through your power supply in a heartbeat. That's the sort of power you'd use to run a drive motor on a rover on Mars - if you wanted it to drive at speeding-on-the-highway speeds at that. The Lunar Rover motor was only 0,1kW.

  How the heck would you even cool a 500W LED spotlight (let alone 1kW, let alone 12 of them) in the near-vacuum atmosphere of Mars? The heat sinks would be massive. LEDs can't run hot, they have to be kept close to room temperature. I have some 600W grow lights. They have a 15kg heat sink and a half a dozen fans on each of them. And you can't practically just cool things with fans on Mars. And they're not like "spotlights", they're about half a meter by half a meter behind the glass panel, and have to be to keep the LEDs far enough apart. It's the reason why LED headlights for cars are a brand new thing, it's very hard to cram many LEDs into a small space without them overheating. A typical modern LED headlight is only about 15W; I was being generous and assuming bright 30W lights.

I wish you were here so I could show you what a 600W LED grow light looks like. It's blinding. The whole world looks pink for a while afterward. And they're massive, heavy things. To put it another way: 600W LED is equivalent to about 5000W incandescent.

I wonder how much could be saved by adapting growth density. Say, he could light up all the saplings with 2-3 lights, but as plants grow, they need more space. So instead of one massive harvest, to make it so that the grown plants take half the available light, grown in 3/4 half of the remainder, half-grown half of the remainder of that, and so on.

The optimal growth method is having 100% of your area lit up at all times, with leaves intercepting 100% of the light. Which can be approximated using a reflective grow tent, thick ground coverage, and harvesting wherever the leaf density starts getting enough that plants are shading themselves out.

But before you start thinking about all sorts of "clever" ways one could try to exchange human labour for increased yields, you have to understand how terrible an unventilated improvized grow environment with "whatever happens to be around" as your growth medium is. You don't have experience with this so can be forgiven for not understanding, but it's incredibly easy for one little screwup that nobody ever could have seen coming (except someone who's done it before you) to come in and wipe everything out in no time flat. I can't begin to tell you how many plants I've lost over the years, in waves, from how many different means. Here's one little one for you to google: ethylene gas. That one got me many years ago when I got "clever" and decided to reduce my greenhouse heating costs by better sealing all of the cracks. Inexplicable temperature spikes when I wasn't around were my bane about a year ago (that one took a *long* time to figure out, I'd just walk in and find half my plants dead - it turned out to be due to how open or closed a door to an adjacent room was). A month ago it was the hygroscopic nature of my fertilizer having soaked up enough humidity that it became too mobile and got released too fast after being added to the soil and thus burned my plants. I could lists literally dozens of these sorts of things. Indoor growth environments suck for plants. They're not evolved to it. With perfect management and unlimited access to raw materials and hardware from Earth, you can get plants to grow well, but it takes process refining, it takes encountering screwups and trying again.

Alternatively, how lethal would space radiation be to potatoes? An extra "tunnel" from transparent plastic, where mature plants would use direct sunlight.

This is actually more practical. There was an experiment scheduled to fly on the Mars 2020 Rover, the Mars Plant Experiment (MPX), to test exactly this (although not with potatoes). It didn't get selected. The jury is still out, so this is a place one could forgive artistic license.

Another option one could have written into the book would be to have a very large "hab with a view", aka, covered in windows for natural lighting. Still, the light levels there (esp. after going through multi-layer plastic) would be really painfully low for the plants. A way to compensate would be for Weir to have designed the solar power farm to be operated by heliostat reflectors. In such a case, he could steal heliostats from the farm and beam light directly into the hab. This would avoid all of the stages of loss involved in conversion of light to electricity and back to light, giving over an order of magnitude more energy imparted. With enough light beamed in laterally, one could have them up on shelves, several high, minimizing the necessary floor space.

But regardless of where the light comes from, however, there's another problem: tens of kilowatts of energy imparted into the habitat, there's no way whatsoever that whatever cooling system was designed into the habitat would be able to handle it (whether passive radiation or active). The situation is worse coming from lights, as you're also dumping the waste heat into the habitat (several times the light energy), but it's pretty terrible in either regard. But regardless, Weir could probably have hand-waved it away with stripping insulation off of the hab - it'd just have to be a very large hab to have enough surface area.

Could have, would have, should have. But as it stands, it's 2-3 orders of magnitude off. Which is head-bangingly bad to anyone who knows anything about growing plants indoors. It's like what it would be like to you (assuming you know how to program) if someone wrote a book with a programmer main character and went into detail about him "programming", and it was absolutely nothing like programming. Something like "He put on his headset and opened up the for-loop. 'Oh, here's the bug!' he said, watching it crawl past him as he drew his debugging pistol. ZAP!!! 'That'll fix this if-function! Now I just need a few more K and the variables should start to process.' " Think of how painful it'd be to read a book that went on for pages and pages like that. And then everyone talked about how much of a "hard science" book it was with "realistic depictions of programming". That's the boat I'm in whenever these threads come up :

Comment Re:Are and storms that fierce on Mars? (Score 1) 112

You cut short the rant. The full rant is:

Well shit.

I came up with a solution, but remember when I burned rocket fuel in the Hab? This’ll be more dangerous.

No, it would in no way, shape or form be. NASA technicians mess assembling probes and rovers do so without any special radiation precautions, just precautions against burning themselves. NASA technicians do not burn toxic hydrazine inside enclosed spaces that they're breathing that they can't ventilate.

I’m going to use the RTG.

The RTG (Radioisotope Thermoelectric Generator) is a big box of Plutonium. But not the kind used in nuclear bombs. No, no. This Plutonium is way more dangerous!

Completely false. It's far less dangerous.

Plutonium-238 is an incredibly unstable isotope.

It's an incredibly predictable isotope, with really only one meaningful decay branch, and that branch being to another element that decays in the same manner, just slower. The half life is certainly short compared to, say, U238, but there are countless isotopes with shorter half lives than it. Its rate of spontaneous fission are low, as are its fission cross section. This is hyperbole at best, completely false at worst.

It’s so radioactive that it will get red hot all by itself.

And? If he thinks something with an 88 year half life is terrible, he should see how elements with half-lives measured in days or hours are. Note that it only gets "red hot" when stored as a large enough lump inside an insulated container. The heat output on a typical RPG is similar to that of a blow drier or small portable space heater.

As you can imagine, a material that can literally fry an egg with radiation is kind of dangerous.

No, it is not, except for burning you. His freaking out about alpha radiation is totally ungrounded.

The RTG houses the Plutonium, catches the radiation in the form of heat

It "catches" it in the way your outer layer of dead skin, a sheet of tissue paper, or several inches of air would also catch it. Almost anything stops alpha.

, and turns it in to electricity. It’s not a reactor. The radiation can’t be increased or decreased. It’s a purely natural process happening at the atomic level.

As long ago as the 1960’s, NASA’s been using RTGs to power unmanned probes. It has lots of advantages over solar power. It’s not affected by storms; it works day or night; it’s entirely internal, so you don’t need delicate solar cells all over your probe.

No, but you need a giant cooling system and more complicated thermal management. And he seems to be talking about RTG-powered spacecraft, but then talks about "storms" and "day or night" which only applies to rovers, so I'm not sure exactly which he's thinking of.

But they never used large RTGs on manned missions until The Ares Program.

Why not?

Because 238Pu is produced in quantities of only a couple kg per year costing many tens of millions of dollars per kilogram. It is a manufactured product, not a waste product, and consequently incredibly expensive. If one wants more power than can be provided from an RTG, the next step up is a small nuclear reactor, not a larger RTG.

It should be pretty fucking obvious why not! They didn’t want to put astronauts next to a glowing hot ball of radioactive death!

No, you're a moron.

I'm exaggerating a little.

No, you're writing complete nonsense. External alpha radiation is completely harmless.

The Plutonium is inside a bunch of pellets, each one sealed and insulated to prevent radiation leakage even if the outer container is breached. So for the Ares Program, they took the risk.

They are not "sealed to prevent radiation leakage". They're sealed to prevent plutonium dioxide leakage. The radiation is harmless. And on that front....

RTGs are designed to withstand (and have withstood) unshielded reentry. They don't just break. Even if you had a bare chunk of 238Pu sitting in front of you, it would not be harmful. It's stored as plutonium oxide, which already being oxidized, does not burn. It is incredibly water stable. It doesn't even melt until it hits 2400C. It fractures into large chunks, not dust. It's so stable that even the vast majority of a bare pellet is estimated to be able to survive reentry without vaporizing.

This should not be interpreted as meaning that all alpha emitters are harmless. Polonium metal, for example, is extremely dangerous. It has a far shorter half life and a low vaporization point, causing it to self vaporizes when it decays. It also forms readily soluble compounds. Between these two factors, it's easy to get into the body. Inside the body, unlike from the outside, it's incredibly damaging to tissue. But none of this applies to bulk 238PuO2.

An Ares mission is all about the MAV. It’s the single most important component. It’s one of the few systems that can’t be replaced or worked around. It’s the only component that causes a complete mission scrub if it’s not working.

Solar cells are great in the short-term, and they’re good for the long-term if you have humans around to clean them. But the MAV sits alone for years quietly making fuel, then just kind of hangs out until its crew arrives. Even doing nothing, it needs power, so NASA can monitor it remotely and run self checks.

Meanwhile, the Opportunity rover is still roving on Mars after years of working on a very simplistic solar power system. But anyway...

The prospect of scrubbing a mission because a solar cell got dirty was unacceptable. They needed a more reliable source of power. So the MAV comes equipped with an RTG. It has 2.6kg of Plutonium-238, which makes almost 1500 Watts of heat. It can turn that in to 100 Watts of electricity. The MAV runs on that until the crew arrive.

Huh? Weren't you just minutes ago talking about large RTGs? MMRTG uses 4kg. GPHS-RTG uses 7,8kg. 2,6kg is nothing.

RTGs absolutely have been used on manned missions. In fact, they were used on the prototypical manned mission to other worlds, the Apollo program - Apollo 12 through 17 each had an RTG Each containing, may I add, 3,8kg of 238Pu.

100 Watts isn’t enough to keep the heater going, but I don’t care about the electrical output. I want the heat. A 1500 Watt heater is so warm I’ll have to tear insulation out of the rover to keep it from getting too hot.

As soon as the rovers were un-stowed and activated, Commander Lewis had the joy of disposing of the RTG. She detached it from the MAV, drove 4 km away, and buried it.

Nobody would ever do that.

However safe it may be, it's still a radioactive core and NASA didn't want it too close to their astronauts.

One again, more idiotic freaking out about "radiation". It's alpha, Weir. It has no penetrative ability. Visible light has orders of magnitude more ability to penetrate than alpha. For god's sake, here's astronauts fiddling with an RTG on the moon. 3 is the RTG, 1 is the fuel cask, being held by a tool to handle it without burning themselves. That's how "freaked out" NASA gets about having RTGs around, that they'll have a guy in a clumsy spacesuit assemble one right beside their return craft.

Skipping him heading off to find it....0

Commander Lewis had buried it atop a small hill. She probably wanted to make sure everyone could see the flag, and it worked great! Except instead of avoiding it, I bee-lined to it and dug it up. Not exactly what she was going for.

It’s a large cylinder with heat-sinks all around it. I could feel the warmth it gave off even through my suit’s gloves. That’s really disconcerting. Especially when you know the root cause of the heat is radiation.

More stupid "radiation" freakout.

Seriously, how can you read this tripe without wanting to hit your head against a wall? How can you call a novel that has this sort of nonsense and does almost every single chemistry equation wrong "hard science fiction"? Does anything that spouts pseudoscientific BS qualify as "hard science fiction" these days?

Theory is gray, but the golden tree of life is green. -- Goethe