Free The Martian by Andy Weir Page B

takes eighteen months for the MAV to make its fuel, so it’s the first thing NASA sends along. Sending it forty-eight months early gives it plenty of extra time in case fuel reactions go slower than expected. But much more importantly, it means a precision soft landing can be done remotely by a pilot in orbit. Direct remote operation from Houston isn’t an option; they’re anywhere from four to twenty light-minutes away.
    Ares 4’s MAV spent eleven months getting to Mars. It left before us and got here around the same time we did. As expected, Martinez landed it beautifully. It was one of the last things we did before piling into our MDV and heading to the surface. Ahh, the good old days, when I had a crew with me.
    I’m lucky. Thirty-two hundred km isn’t that bad. It could have been up to 10,000 km away. And because I’m on the flattest part of Mars, the first 650 kilometers is nice, smooth terrain (Yay Acidalia Planitia!) but the rest of it is nasty, rugged, crater-pocked hell.
    Obviously, I’ll have to use a rover. And guess what? They weren’t designed for massive overland journeys.
    This is going to be a research effort, with a bunch of experimentation. I’ll have to become my own little NASA, figuring out how to explore far from the Hab. The good news is I have lots of time to figure it out. Almost four years.
    Some stuff is obvious. I’ll need to use a rover. It’ll take a long time, so I’ll need to bring supplies. I’ll need to recharge en route, and rovers don’t have solar cells, so I’ll need to steal some from the Hab’s solar farm. During the trip I’ll need to breathe, eat, and drink.
    Lucky for me, the tech specs for everything are right here in the computer.
    I’ll need to trick out a rover. Basically it’ll have to be a mobile Hab. I’ll pick Rover 2 as my target. We have a certain bond, after I spent two days in it during the Great Hydrogen Scare of Sol 37.
    There’s too much shit to think about all at once. So for now, I’ll just think about power.
    Our mission had a 10-kilometer operational radius. Knowing we wouldn’t take straight-line paths, NASA designed the rovers to go 35 kilometers on a full charge. That presumes flat, reasonable terrain. Each rover has a 9000-watt-hour battery.
    Step one is to loot Rover 1’s battery and install it in Rover 2. Ta-daa! I just doubled my full-charge range.
    There’s just one complication. Heating.
    Part of the battery power goes to heating the rover. Mars is really cold. Normally, we were expected to do all EVAs in under five hours. But I’ll be living in it twenty-four and a half hours a day. According to the specs, the heating equipment soaks up 400 watts. Keeping it on would eat up 9800 watt hours per day. Over half my power supply, every day!
    But I do have a free source of heat: me. A couple million years of evolution gave me “warm-blooded” technology. I can just turn off the heater and wear layers. The rover has good insulation, too. It’ll have to be enough; I need every bit of power.
    According to my boring math, moving the rover eats 200 watt hours of juice to go 1 kilometer, so using the full 18,000 watt hours for motion (minus a negligible amount for computer, life support, etc.) gets me 90 kilometers of travel. Now we’re talkin’.
    I’ll never
actually
get 90 kilometers on a single charge. I’ll have hills to deal with, and rough terrain, sand, etc. But it’s a good ballpark. It tells me that it would take
at least
35 days of travel to get to Ares 4. It’ll probably be more like 50. But that’s plausible, at least.
    At the rover’s blazing 25 kph top speed, it’ll take me three and a half hours before I run the battery down. I can drive in twilight, and save the sunny part of the day for charging. This time of year I get about thirteen hours of light. How many solar cells will I have to pilfer from the Hab’s farm?
    Thanks to the fine taxpayers of America, I have over 100 square meters of the most expensive