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The Real NASA Technologies In 'The Martian'
An anonymous reader writes: On October 2, movie audiences will get to see Ridley Scott's adaptation of Andy Weir's brilliant sci-fi novel The Martian, about a near-future astronaut who gets left for dead on the planet Mars. (Official trailer.) Both book and film are rooted in actual science, and NASA has now posted a list of technologies featured in the movie that either already exist, or are in development. For example, the Mars rover: "On Earth today, NASA is working to prepare for every encounter with the Multi-Mission Space Exploration Vehicle (MMSEV). The MMSEV has been used in NASA's analog mission projects to help solve problems that the agency is aware of and to reveal some that may be hidden. The technologies are developed to be versatile enough to support missions to an asteroid, Mars, its moons and other missions in the future." They also show off their efforts to develop water reclamation, gardens in space, and oxygen recovery.
The basic plan in the book is a variant of Mars Direct https://en.wikipedia.org/wiki/Mars_Direct, which was a proposal for a much cheaper way of getting to Mars than previous proposals. The primary cost savings are in making some resources on site (especially fuel for the return). If you haven't read The Martian you should. The book was excellent. Also, relevant XKCD https://xkcd.com/1536/.
The book was terrible. One an average of at least one god-awful mockery of science per page and the main character "scientist" who writes like an 11-year-old boy and apparently doesn't know a single technical term for anything.
The terrible science wouldn't be so bad if the author didn't keep rubbing it in the reader's face, and I'm not even talking about the "growing potatoes with about 2-3 orders of magnitude too little light while planting them stacked on top of each other like cordwood" aspect. For example, again and again he kept doing the idiot version of chemistry, like:
"Not because of the perfect landing, but because he left so much fuel behind. Hundreds of liters of unused Hydrazine. Each molecule of Hydrazine has four hydrogen atoms in it. So each liter of Hydrazine has enough hydrogen for *two* liters of water"
(Morbo voice: "Stoichiometry does not work that way!")
It's so hard to pick the most terrible example from the book... one that's definitely a contender was the "habitat went up to 64% hydrogen and down to 9% oxygen without him noticing" part ;) Really, the high sqeaky voice didn't tip him off? The unconsciousness wasn't a clue?
Though him freaking out about the RTG was pretty priceless too... really, the whole thing is like a MST3K film in book form. I have trouble taking people seriously when they claim they thought it was a good book.
"99 dead duelists of Dios on the wall. 99 dead duelists of Dios! Take one's ring, pass it around..."
Yes, it's a book for people who don't know science.
Which says nothing about how much volume they take up as liquids. You can only use that approach when dealing with ideal gases maintained at a constant temperature and pressure. The volume of water you get from burning a liter of hydrazine is only about 1,15 liters. Liquid density and number of moles have no inherent linkage. Do you think that if you take a bottle of styrene and polymerize it into polystyrene that it suddenly shrinks down to just a couple percent of its former size?
The author makes this mistake over and over and over again, and it's the sort of thing that would get you a D in high school chemistry.
The potatoes were there to be cooked as thanksgiving dinner, and no, it's not even slightly, remotely possible. Your lights have to replace Earth sunlight. They have him taking Mars sunlight (44% as strong) striking 200 square meters solar panels, which the author describes as "an astounding 10.2% efficiency" with no hint of sarcasm (that's actually a terrible efficiency). The panels aren't sun tracking, so you're looking at a capacity factor of 20%-ish in a sunny location *if* they're kept perfectly clean, which of course the book keeps telling us that they're not. So now these 200 square meters of solar panels are creating an electricity equivalent of the sunlight that hits 1,8 square meters of ground with the sun overhead on Earth. But wait, we're not done! Just assuming that 100% of it goes into powering the lights, you have to then account for the inefficiencies of the lights. The most efficient lighting in the world today are lab-scale LEDs with an EQE of about 30% (note: this is different from luminous efficiency, which is weighted by the frequencies the human eye is sensitive to). If we assume no other losses in the system (very much false), then we have the amount of sun that strikes half a square meter of ground on Earth... to grow 100 square meters of potatoes.
Now, there are some potential improvements there. The lights could be frequencies that plants use more efficiently than broad-spectrum sunlight. And there's the fact that the sun strikes plants at different angles (although they still intercept more than a fixed-angle planar solar panel, it's only simple cosine losses). But if you want to account for things like that, then you need to whack off another 30% or so of the energy for dust, another couple dozen percent for energy used on life support and other habitat functions, another 5-10% for wiring and conversion losses, you need to drop your light efficiencies to a more realistic 10-20%, and so forth. And where's he supposed to get lights tailored to plant growth? The book simply says he uses the habitat's regular room lighting.
It's orders of magnitude off. Which should be obvious to anyone who took even the slightest amount of time to think about what was being proposed. Or has ever seen a greenhouse where plants are grown under light. And speaking of that, he's talking about using normal room lighting to grow plants. The sun hits the surface of the Earth at about 1000W/m^2. Going with 20% efficient LED light bulbs, that means you need 5kW of light bulbs per square meter to match it. Meaning if these were say 30W LED bulbs (very bright for that sort of efficiency), you'd still be having to place 167 of them per square meter to match the sun. Is your room lit up like that?
And heck, I'm only even talking about the lighting here, it's just one of about two dozen different reasons why the entire concept as presented in the book is a complete non-starter, from him doing absolutely nothing to remove the perchlorate salts from the regolith (regolith apparently being a word that this "botanist" doesn't know - although
"99 dead duelists of Dios on the wall. 99 dead duelists of Dios! Take one's ring, pass it around..."