10 thoughts on “The Martian”

  1. I didn’t really expect to like the book much, but was pleasantly surprised. Weir’s comments about scientific accuracy reminded me of an interview with Robert Heinlein I read once: discussing his classic juvenile novel Red Planet, RAH talked about making the book as accurate as was feasible (given the state of knowledge at the time), and, just like Weir’s book, the consistency is crucial to the willing suspension of disbelief good fiction requires. I hope that Ridley Scott doesn’t screw it up too bad, but his recent track record is worrisome.

      1. Selected Heinlein:

        “”Certainly, certainly! I understand basic ballistics, Mister. But why do you reject the other alternative? Why not increase our speed? Why can’t I accelerate directly along my present course if I choose?”

        Libby looked worried. “The Captain may, if he so orders. But it would be an attempt to exceed the speed of light. That has been assumed to be impossible-”

        “That’s exactly what I was driving at: ‘Assumed.’ I’ve always wondered if that assumption was justified. Now seems like a good time to find out.”

        ——

        “Mr. Ortega, admitting that you can’t pass the speed of light,
        what would happen if the Star Rover got up close to the speed of
        light–and then the Captain suddenly stepped the drive up to about six g and held it there?”

        “Why, it would–No, let’s put it this way– See here, kid, don’t
        ask me questions like that. I’m an engineer with hairy ears, not
        a mathematical physicist. Truthfully, I don’t know what would
        happen, but I would sure give a pretty to find out. Maybe we
        would find out what the square root of minus one looks like–from the inside.”

        —
        🙂

  2. Andrew I believe it was, once talked about the thin martian atmosphere acting as a thermal insulator with regard to a green house. Even Affleck would be better in the role than Damon… goofy mug and all.

  3. The point about the effects of the windstorm got raised elsewhere, and I quickly came up with a more plausible way for a windstorm to strand Watney.

    The atmospheric density on the surface of Mars is 0.020 kg/m^3, whereas Earth sea level density is 1.225 kg/m^3. so Mars’ atmosphere is only 1.63 percent as dense as Earth sea level. The pressure is only 0.6 percent as much, but Mars is very cold and the molecular weight is higher (about 44 versus 28.8 g/mole). For the same force you’d divide Mars winds speeds by 7.826 to get an Earth sea-level wind that would give an equivalent force. (7.826 is the square root of the air density ratio of 100/1.63 percent)

    So a 60 mph wind on Mars produces the same force as a 7.8 mph wind on Earth, a 100 mph Martian wind is like a 12.7 mph Earth wind, and to produce effects similar to an Earth thunderstorm (45 mph winds) would take a 350 mph Martian wind. To hit a category 1 hurricane force (74 mph here) would take a Martian wind of 580 mph, but Mach 1 at Mars surface is only 537 mph, so Martian wind would have to go supersonic before it rocks you like a hurricane. So the problem is that the wind storm doesn’t pack much force [i]per area[/i], but I figured out how it could still cause the abort.

    So here goes:

    Storms and Impacts

    As given, the hab was landed years earlier and its packed with the supplies they’ll need. But a lot of those supplies aren’t going to be needed in the hab, they’re going to be needed outside, and as part of moving into the hab the astronauts have to free up internal space by placing some of supplies and monitoring equipment outside in unpressurized pop up tents (to keep sand out). So upon arrival, various pop-tents will be deployed up to a hundred meters away from the hab, and then over the first several days some of the supplies and equipment are gradually moved from the hab to the tents.

    The supply tents aren’t held rigid with pressure because suited astronauts will be frequently entering and leaving them to load up various experiment and sampling packages for the rovers, and an airlock would just get in the way. So they’re basically just super light-weight regular dome-style camping tents held rigid by carbon fiber poles. They’re not anchored because with a maximum effective wind pressure of about 10 mph, the equipment and supplies to be loaded into them are more than sufficient to keep them grounded.

    So, a few days into the mission, just as given, the storm hits, and hits after they’ve deployed all the tents but before they’ve finished moving the equipment into all of them. That creates the tumbleweed from hell, bouncing along at nearly the full 60 mph Martian wind speed before violently colliding with the hab, where the end of one of its poles creates an inconveniently located puncture, before rebounding upward to take out the communications antenna, getting entangled with it before heading out to parts unknown.

    The tumbleweed from hell angle uses a large surface area and low mass structure to convert high-velocity, low-force winds into a sharp, high velocity impact.

    Abort rules

    So, their hab is breached and they’ve lost direct communications. Under any conceivable mission rules that is an abort scenario, so they have to suit up, head to the rovers, and drive to the ascent vehicle. Except for the other mission rule that says they can’t drive the rovers in low or zero visibility. So they have to walk, which is okay because they had to walk from the descent craft to the hab in the first place.

    Unexpected Consequences of Shaving Weight

    To keep the mass of the descent stage down, NASA decided doesn’t need the ability to resupply EVA suits with LOX because the suits will be filled in orbit, and the suits themselves will just pipe into the descent-stage ECS air supply during flight. So upon landing, the EVA suits will be full up and ready for the walk to the hab, and if they land too far from the hab its another abort condition. Even if the descent craft had the ability to refill the EVA suits, if the walk to the hab is further than the one fill-up can get them, subsequent fill ups won’t do any good because they’d walk to their turn-around point, walk back, fill-up, and still couldn’t walk any further away than they did for the first turn-around. If one fill-up can’t get you to the hab, a hundred fill-ups can’t either. So the descent stage can’t refill an EVA suit, only the hab can.

    The hab is designed to refill an EVA suit’s backpack, but to do so requires removing the backpack or suit inside the hab. There’s no point in giving the hab air hoses that plug into a suit (like earlier US spacecraft) because that would just chain everyone to a desk – in a hab – that’s unpressurized and can’t go anywhere. Eventually they’d either run out of air or starve to death. So no external air hose connections in the hab.

    So what happens if the astronauts return from an EVA to a collapsed hab when their backpacks are low on oxygen? Well, for redundancy the hab has two backpacks per astronaut, and those can be quickly swapped out. That covers both equipment shortfalls and the unlikely case that the hab happens to rupture just as astronauts are returning from an extended surface walk, allowing them to swap out backpacks and head back to the descent vehicle, which of course must be within a backpack’s walk of the hab or the astronauts couldn’t have gotten to the hab in the first place.

    These obvious engineering choices have an odd consequence, in that if the hab deflates the astronauts are committed to making their way to the descent vehicle, which can be so far away that they can only make that trip once on the oxygen supply of an EVA backpack. Once they reach the descent vehicle, there’s no way to refill their backpacks so no hab return is possible. If they are forced to leave the hab, they are committed to an ascent. Since the fuel was made in situ, an ascent cannot be followed by a return descent, and Watney is going to be stranded, one way or another, if he’s not on the ascent vehicle.

    Story Options

    There are several, now that we’ve established that if Watney doesn’t get to the ascent vehicle, he will be stranded. But sticking with the story we know, everyone needs to assume Watney died, Impaling him worked when the idea was the fierce Martian winds, but in this workaround those can’t be reinvoked and having a second hole-in-one by a pop-up tent as the crew marches to the ascent vehicle is going to be implausible.

    So you could make Watney the first victim of the tumble-weed from hell, perhaps heading toward it because someone had picked up on the potential disaster based on wind direction. You could have his suit go dead moments before the hab deflates and panic sets in as everyone else scrambles into the suits they just doffed, all having returned from surface exploration. You could also posit that the particular tent was just over a rise and that the suits communicate either through the hab antenna tower or peer-to-peer by line of site, and he was just over a rise, and that in all the commotion of the hab breech the crew didn’t put two and two together, that the antenna was why they lost comms with Watney.

    The loss of Watney’s suit signals could be followed by some tense moments, a failure to see him outside or establish communications with him (he was knocked out by the tent). Due to the previously established engineering choices the crew wouldn’t have reserves to both conduct a search and make it to the ascent vehicle, so there really is no choice given the mission rules. They have to abort without Watney.

    Watney, a short time later, makes it back to a breached hab and commits himself to engineering with duct tape or a patch kit, and later finding out that communications are just gone, and the story proceeds as written. You could also have Watney’s suit comms knocked out by the impact that knocked him out (and he needs to be knocked out so he doesn’t appear over the rise waving his arms).

    But for added dramatic effect, I’d have the commander following the mission rules, because they are the mission rules, until she and the crew get to the lander, primarily to re-establish contact with Earth and use it as a lifeboat, having them all insisting that the need to return to the hab and search for Watney. Then you cut to NASA and discussions that the crew is good for several days in the lander, but that there’s no way that their now-depleted EVA suits can even get them halfway to the hab. You could even have NASA engineers explaining the engineering decisions about the EVA suits to the crew, who hadn’t thought through this one particular scenario before because the logic of not having the lander able to refill an EVA suit made perfect sense when it had been explained to them back on Earth. The crew finds themselves stranded in the ascent vehicle with no option but to go back into orbit, and they still haven’t heard a peep out of Watney. Psychologically, everyone needs to buy in to the idea that Watney is already dead, because there’s not a darn thing they could do about it if he isn’t. As a writer, you could squeeze a lot of juice out of that.

    1. George, you’re spot on about the much reduced dynamic pressure, but the tipover forces are also reduced because of the lighter gravity; i.e., the force (and resultant moment) that a horizontal wind has to impart to a vertical object in order to tip it over is reduced by 2/3rds because Mars surface gravity is only 1/3 of Earth’s. Sliding also becomes a problem because of less frictional force. I haven’t tried to work out how this changes the scenarios, but it is likely to be a significant effect.

    2. That’s a good point. I hadn’t thought of that. I hear NASA has an unused vacuum engine test facility where we do some trial runs with a pop-up tent, perhaps building it 2/3rds lighter than normal. 🙂

      Mulling my premise over a bit more, it would make sense that Watney would be heading right for the tent because it hadn’t been weighed down with supplies yet, and someone, somewhere, figured it would blow away in the storm (causing the loss of one pop-up tent). That creates an opportunity for some dialog about Martian wind speeds and their effects. Then, just as Watney clears a small rise on the way to fix the problem – “Hello tent….” and smack. Technical plot problem solved.

      I’ve still not though of a good reason to put the tent a hundred or so meters away, which I think might be required to give it room to get it up to speed and rolling/bouncing along, but I haven’t done any math on it.

      *looks up random 2 and 3 person dome tents*

      We could assume the tent would weigh four or five pounds and is roughly like a ball 2 meters in diameter. CO2 at -80F has a dynamic viscosity of 1.06e-5 N.s/m^2, a 60 mph wind is 26.8 m/sec, and the air density is 0.020 kg/m^3, so the Reynolds number for the 2 meter tent is around 100,000. A sphere at Re=10^5 has a drag coefficient of about 0.5, so the initial force (F=1/2*Cd*rho*cross sectional area * v^2, which gives 11.3 Newtons (2.53 lbsf).

      *goes and builds a spread sheet with a 0.1 second time step, calculating tent velocity, relative air speed, drag force at that airspeed, acceleration, and total distance covered*

      For a 60 mph wind with a 2 meter diameter tent (cross sectional area of pi) that weighs 5 pounds:

      It hits 20 mph in 2.7 seconds after traveling 14 meters.
      It hits 30 mph in 5.4 seconds after traveling 45 meters.
      It hits 40 mph in 10.7 seconds after traveling 129 meters.
      It hits 50 mph in 30 seconds after traveling a half kilometer (rock drag would probably prevent it getting this fast).

      An 80 mph wind would get a tent to 50 mph in 6.7 seconds and 100 meters.

      This may explain why the rovers haven’t seen any tents on Mars.

  4. Andy needs to stick to his knitting and have someone be stranded on a return-to-the-Moon mission on the far side with all the lunar orbiters knocked out. It should be a challenge to make that plausible, but he won’t have to worry about drama. He can even have Watney be Gilligan again.

  5. I hope he publishes his moon book independently. I want to read it regardless of what the editor told him.

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