So let's look at current ideal, best-case recharge rates. With eleven good hours of recharge time in a sol, if we use them all we're guaranteed of a full battery. But my math says there's very little margin. If we lose more than half an hour of prime recharge time, we don't start the next day on a full battery.
I say eleven hours, but that's not precisely true. There's almost twelve hours of good charging daylight each day. The problem is, I use an hour of it each day for driving, in addition to the pre-dawn drive. If I reconnect the solar cells and drive with constant recharging, I get about 3.6 pirate-ninjas in that hour, or about enough power for three and a half kilometers more. The less efficient charging right at dawn would probably stretch that to four, which requires maybe an extra nine minutes of driving. Push it any farther, and it becomes unsustainable.
I can't throw more solar panels at this. We only have six spares, and anyway with the saddlebags and roof storage already accounted for there's no place to put them.
Maybe Starlight Glimmer could stick those solar power catchers she made for the cave farm on top of the panels. Not the same ones, of course. The solar panels are lightweight and can't stand to have a big fucking slab of quartz sitting on top. But maybe a thin layer of glass...
Maybe I see a way out of this. Yeah. Time to talk to the man with the plan... or the unicorn with the horn... or something.
Author's Notes:
The exact efficiency curve of electric motors depends much on the motor and its power rating. It's not far off a horizontal line, but that's only after the first twenty percent or so. An electric motor moving less than twenty percent of its rated load, according to my reading, really is shit for efficiency.
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Sol 419
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AMICITAS FLIGHT THREE — MISSION DAY 426
ARES III SOL 419
"Glass pyramids."
"Yeah. Bubbles would be better, because they'd be more resistant against breaking after a serious jolt, but that's pretty much it."
"Eighty-four glass pyramids."
"No, just fifty-six. If we put them on the solar panels we carry on the rover, they won't stack anymore, and we won't be able to carry them."
"All right. Fifty-six glass pyramids. On top of the ship. Which no longer has a safe place to stand on top of it, if it ever had one, because it's covered with solar panels."
"Starlight, I get the feeling you're less than enthusiastic about my little brainstorm," Mark said.
Starlight rolled her eyes. "Whatever gave you that idea?"
"Look, it's this or take a lot longer to get to the Mav," Mark said. "Like nine days longer if absolutely nothing goes wrong. Unless you can think of some other way to juice up the solar panels? Or maybe I could dismantle the wheels on the nose gear, remove their motors, and rig some sort of bicycle so we could take turns manually charging the batteries?"
Starlight shook her head. "Where do you get these ideas?" she asked.
"I dunno," Mark said. "Where did you get yours? The cave farm is almost entirely your baby, you know."
Starlight's head continued shaking. "There's a little shop in the crater behind the Hab," she said with mixed sarcasm and disgust. "Can't miss it. Big sign saying `DISCOUNT BAD IDEAS.' Fireball has a gold card membership, and I put the shop owner's kid through college."
Mark chuckled. "I think my jokes may be rubbing off on you a bit."
"No, seriously, Mark," Starlight Glimmer said, setting her hooves on the worktable, "I don't have original ideas. Not good ones. I know a ton of spells because I was an obsessed little filly who wanted to bend the world to her wishes. Every time I think of something myself, it goes wrong."
"Not true," Mark said.
"Transmuting rocks to ballistic cherries."
"You could probably do it now."
"The perchlorate spell."
"Which we use for salt mining. God, I don't know what we'd do without that."
"The methane spell."
"That one was my idea, remember?" Mark smiled. "Look, I'm not letting you off the hook. Most of the time if I come up with an idea, I have to come to you for implementation, right? But you came up with the translation spell that got us talking at first. You sealed the cave for the first time without asking for help from home. The lighting crystals were all you. Using the rainbow crystals to circulate water and add heat to the cave— all you. I couldn't have done any of that by myself. If it was left to me, we'd still be playing Pictionary."
Starlight looked at the whiteboard currently in the Hab. It had been drawn on and erased until the residue had made it less a white and more a darkish grey. "That'd be a neat trick," she said.
"Look, I'm sorry I'm always imposing on you," Mark said. "Believe me, I'd love to learn magic. I'd need a wand or something like in Harry Potter, but even if I could just make colored lights like you do-"
"Mark, we have wands that make light. They're called flashlights. You have them too." She sighed. "Look, take it from a recovering magic addict. Magic isn't everything. It's a tool just like anything else, and it can be dangerous if used irresponsibly."
"I'd still love to learn."
Starlight sighed again. "If you visit Pony-land, we'll see what can be done, okay?" She lit up her horn— it took a lot from her reserves, with the plants gone from the Hab— and made a line-picture in light above the work table. "Why a pyramid?" she asked.
"Surface area and angles," Mark said. "Imagine each square meter as four right triangles with the hypotenuse being a side of the square. 45-45-90 isosceles triangles, right? Each of them is a quarter square meter in area. Now imagine four 60-60-60 triangles instead— equilateral triangles, all of the sides being one meter long. Do the math, and each of those is a bit more than two-fifths of a square meter in area. More surface area. And since it stands up above the panel, you end up able to catch even a bit of light from lower angles. Add your light-gathering spell, and you get... well, I don't know how much you get, but more than we're getting now."
"Huh." Starlight thought about this for a moment, then banished the cantrip. She couldn't hold it much longer anyway. "You don't want bubbles," she said. "They might be more sturdy, but they'd be lenses concentrating all the light on a single point. Bad idea, don't you think?"
Mark blinked. "Oh. Yeah, you're right. I'd forgotten about that."
"I think I can cobble together something from a couple of mirror spells— not like Granny Weatherwax's sister did, perfectly safe stuff. Instead of being a relay like in the cave, I could have the glass just refract any light that hits it straight down onto the panel. There might still be some hot spots, but nothing that would melt the panel."
"Okay, I can see it."
"The problem is, these things will have to be thin to save weight," Starlight continued. "And they'll have to rest only on the panel frame, so they don't damage the cells. These are going to get broken a lot, Mark."
"Can you fix them?"
"I can't patch them. If they crack, good-bye enchantment. No, I'd have to replace any broken dome. That means bringing along raw material for repairs. A couple of big blocks of the clearest quartz we can find. I might be able to recycle broken domes into new ones, but I think we'd better add half a ton of quartz to the load."
Mark groaned. "You know we're trying to move faster, not slower, right?"
"If you think we're going to find a second gem cave on the trip-"
"No, no, I get you," Mark said, waving a hand in defeat. "When can we begin?"
"I need a place where I can stand and look down on the rover from not too far away," Starlight said. "That means a gully with steep sides somewhere. Site Epsilon's sides aren't steep enough."
"Okay. Get the crystal you need tomorrow, installation the next sol, Sirius 7C after that?"
"Sounds good."
Author's Notes:
I'm not fond at all with how this turned out, but the important thing is this: I wrote this last night, after I posted yesterday's chapter.
And I just finished writing another chapter.
I have a chapter in the buffer.
Which is good, because AnimeFEST in Dallas this weekend runs from Friday through Monday.
By the way, I haven't mentioned this before, but about a month ago I had a realization as I was about to drop off into sleep.
All this time I've described the mana batteries as having two posts each, like a car battery, only magical. But that night I realized: wait a minute, magic is NOT a polar energy! Once you expend the power, nothing cycles back to the battery! There's no need for a loop circuit! The batteries should have only ONE post!
But I didn't feel like changing every mention of battery posts at that point in the story— even less so, now. So magic batteries have two posts, Because Reasons. Tra-la.
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Sols 423-424
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MISSION LOG — SOL 423
Seventy-one point seven five kilometers!
AND, this time, a full fucking tank of pirate-ninjas long before sunset!
We are celebrating, and honestly this time. I've broken open two of the meal packs and divided up bits here and there to give us all at least one flavor that isn't alfatato.
(God, that's a horrible thought; a genetically engineered spud that tastes like hay, or a bean that grows taters on the stalk. I hope I never live to see it. Of course, somebody will read this and think, "What a neat idea! And I'm sure Mark Watney will be honored to see the product of his genius in person!" Well, future reader, let me be clear: if you do make it, keep that shit the fuck away from me unless you want to wear it. I like to think of myself as a gentle and nonviolent person, but I have my breaking point, and that will be it. Fair warning.)
Okay, to explain the solution: hothouse roofs.
It's a little more complicated than that, but not much.
On Sol 421 we went to the cave. Cherry drafted Spitfire to help her tend to the farm, including all the just sprouted new potato plants. The rest of us went and harvested the best remaining big chunks of rock crystal. These had to be absolutely clear, so sunlight could pass through. It wasn't easy, since we already used the best crystals in the cave for the jumbo booster batteries, but eventually Starlight said she could use extra magic to alter the shape of the quartz to fit what we need.
Which she did next. We made thirty rather thick slices of crystal and laid them out in a large open spot at the back of the farm. (We only need twenty-eight, but spares.) A bit of magic later, Starlight had the thick chunks of crystal turned to really thin sheets, one meter wide by two meters long each. They'll just barely fit through the cave airlock this way, but we had to do it here, because of the next step in the process.
The problem with crystal is, it can actually be more fragile than glass in certain ways. Cracks in glass propagate slowly, because the molecular structure is irregular. The whole definition of crystal is that it has a very regular structure, so if a crack finds one of its lines of cleavage, it'll zip right down it, and all you have left is shards. And that's a major concern, because these are thin sheets of crystal glass that will have to deal with every bump and jolt along the way, plus a daily temperature swing of between sixty and seventy degrees Celsius from hot to cold and back.
So we decided to add a lamination layer to our crystal panels to make them more resistant to breaking— and to make it easier to replace them when we have to.
That was Dragonfly's job. She wasn't happy about it, but she didn't need much persuading. She cooked up a clear form of goop in her guts and spread it with surprising evenness across each of the slabs— surprising because the process involved projectile spitting the stuff from a few meters away, then wrapping the overflow around the edges of the slabs. She then nibbled off the excess gunk to recycle it.
Seriously, changelings are adorable, but they're also gross as hell.
Anyway, we didn't take the slices out to the rover immediately. There was no point in exposing them to the aforementioned temperature extremes until they were installed. And installation would require a bit of preparation. Besides, the laminate needed some time to cure properly.
Yesterday we took the full Whinnybago out almost to Site Epsilon. There we found a spot in the gully nearest to the mountain where someone standing on top of the bank could almost look straight down at the trailer. We then went to the cave, loaded the panels onto the roof (we'd removed the saddlebags for this operation) and carefully drove the things to the trailer. We then went back and fetched eight magic batteries, because what came next was going to take a lot of juice.
The frames of the solar panels are not designed to be opened up, at all, ever. In fact, they're designed to hold together despite tremendous stresses, because they have to ride a resupply mission that launches at accelerations no human could tolerate and then land on Mars in a giant tumbler with air bags and everything. But there is a little lip sticking up from the surface of the actual panels, so that when they're stacked you don't actually have the panels rubbing against each other. That's what we had to work with— that and a lot of pony magic.
Fireball and I spent nearly two hours and six batteries standing on thin air with nothing between us and broken everything except the willpower of a unicorn. We "stood" on either side of each panel as, one by one, the laminated crystal sheets were levitated down to us so we could carefully and precisely seat them in the lip of the frame. Thankfully, they were a perfect fit. We were very careful, both for the sheets and for the integrity of our spacesuit gloves. But the thick layer of clear laminate around the edges protected us. We got through all twenty-eight without a hitch.
Then Starlight put us back on solid ground so she could finish the job. She snugged up the lips of all twenty-eight panels to hold the new panels firmly in place, using the wrapped-around laminate as a sort of rubber gasket. And then she stretched the crystal. She didn't make two big meter-square pyramids per panel, as I'd suggested. She had a better idea. She made a bunch of little pyramids— fifty of them, twenty centimeters on a side, per panel, with rounded and reinforced edges and peaks. As she pointed out, the smaller each pyramid is, the less distance the sides will wobble on each bump, and the less likely they are to crack or break. It's a damn good idea, and I give her full credit for having it.
