Neither the Hab nor the rovers contain an automatic air pressure release valve. In the unlikely event that an environment becomes overpressurized, the life support systems simply pull air out and stuff it in tanks— the Hab via the atmospheric regulator and water reclaimer, a small air sump tank in the rovers. If that system doesn't work, it's expected that a human being will be on hand to turn valves manually. Thus, according to NASA mission planning, there's no reason to have an automatic pressure release. In fact, there's one strong reason not to have it— it's another hole in the pressure vessel that can fail and cause a breach.
So obviously I didn't have a spare one, and I don't have the carefully calibrated spring required to make an accurate one from scratch. But, as it turns out, the pony ship had such a valve, and Dragonfly has not one but two spares. Dragonfly doesn't know exactly why, except that it might be a fail-safe design, or possibly just recycling off-the-shelf parts for ship components. Both things play a huge role, she says, in pony rocket design.
The automatic pressure release valve is part of a manual system to allow for EVA if the airlocks aren't working properly. If a pony isn't leaning on the valve, it automatically shuts— unless the air pressure is more than 1.2 atmospheres. Dragonfly looked it up in the crumbling remains of the ship's freeze-dried manuals, and that's what the valve's rated for. And that's perfect for my overpressure issues, which I admit might be entirely unfounded, but I want to be sure.
But that got me thinking... Dragonfly's spare pressure valve solves the main problem with using the MAV fuel plant to pump in Martian air from outside. Of course, running it full-time would waste power, not to mention it might risk smothering the plants in the other direction. Plants need to breathe in oxygen at night when they can't photosynthesize.
But... but yeah, I think I see a way to make this work, with no magic involved. Just my tools, some leftover NASA pieces of equipment that were never meant to be put together, and a software patch courtesy of some big brains back on Earth.
Yeah, I think this could really work.
Now the question is, how do I explain my new idea to Starlight without pissing her off for real this time?
Author's Notes:
Written in haste. Almost time to start packing up. Not a disaster, but a lot less profitable than it should have been.
It's nice to find a way to show Mark being Mark. He's taken a back seat to the ponies a lot here, since so many of the solutions require magic of some kind.
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Sol 389
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AMICITAS FLIGHT THREE — MISSION DAY 395
ARES III SOL 389
[09:08] JPL: You want us to do what so the what will what with the what?
[09:36] WATNEY: Okay, maybe I should fill you in a bit more. I plan to take one of the Hab laptops, install the rover control package on it, and plug in Rover 1's discarded atmospheric analyzer. I'll then fix another wire that can run through the cave airlock to the Ares III MAV fuel plant. When CO2 drops below one hundred parts per million in the cave, I want the computer to turn on the fuel plant, which I'm rigging to release CO2 from a storage tank into the cave. When CO2 rises above five hundred ppm, I want the computer to shut off the fuel plant. The ponies have a spare automatic air pressure release valve I can use to prevent air pressure from getting dangerously high inside the cave. This will replace the CO2 provided by the pony air exchange system once we're gone.
[10:03] JPL: Mark, I might mention it's extremely A. M. here in Houston right now. My bed thinks I'm having an affair with a sofa. I don't even want to know what my wife thinks.
[10:12] HERMES: Johanssen here. I can do it. Mark, I'll send you details on where and how to splice a spare USB connector onto the MAV fuel plant control board to make this work. The software patch will take about two hours plus debugging.
[10:23] JPL: Bless you, Beth. Mark, I hope you can be finished with this in equally rapid time. By the way, how's the weather today?
[14:18] WATNEY: Thanks, Johanssen. We all appreciate it. Expect a big pony hug from Commander Berry once we dock with Hermes.
The sky today is overcast, covered in vaguely pink-tinted cirrus clouds. The pink, I assume, means that the atmosphere has run out of condensable water vapor and that the dust is winning again. Hab power systems show solar cells running at about 90% efficiency, which will probably go back to full power once the clouds clear out.
We moved the fuel plant to the cave today and installed an air line through the cave wall. The seal is good. The Hab has one spare air circulation fan in stores; I'm going to install that on the end of the air line to provide some air mixing and circulation in the cave when we're gone. There are plugs in the airlock I can use to route the control wires for the fuel plant, and they check out.
Thanks, guys. Between this and the other work we've done, the cave farm has a fighting chance to still be alive when Ares V or whoever return here. I appreciate the help.
[14:38] HERMES: No problem, Mark. I'm writing the program to activate the analyzer at hourly intervals. You'll need to keep the analyzer away from the CO2 outlet line so it doesn't skew the results. I'll send the program by direct uplink, but it'll take most of a day to download at current bandwidth. Probably day after tomorrow.
[14:44] JPL: This is Dr. Kapoor's bed speaking. Why do you horrible people have to break up a happy home for your selfish, uncaring desires? We were so happy together, once. Can't you just leave us alone?
[14:46] JPL: Again, that was not me. Whoever it was is lucky I've had my third cup of coffee. Bruce, your people continue to tap-dance on the edge of destruction.
[14:48] JPL: Venkat, darling, come home. I've put on your favorite sheets, with the hospital corners you like so much...
[14:50] JPL: And I thought astronauts were the only adrenaline junkies working for NASA...
Author's Notes:
Sorry this is all I have. I have a lot of work to do before leaving Thursday for Amarillo, and I've not been feeling well the last couple of days. If it persists after the trip, I'll call the doctor and try to get an appointment. (I'm not doing it now because it takes weeks to get an appointment, by which time whatever it is might clear up by itself.)
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Sols 392-395
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MISSION LOG — SOL 392
The new air system is up and running in the cave— and just in time.
Johanssen's little program isn't exactly a software patch. It's a separate program that runs in the background most of the time. It does have a test sequence, because Beth Johanssen is not just a nerd but a super-nerd who understands the need to double-check everything, especially in space.
We made all the connections, and the system works great. The fuel plant released carbon dioxide, the pressure valve that keeps the air in the cave from escaping back out through the fuel plant opened up just enough to let the CO2 in, and the plant shut off exactly when the computer told it to.
For a triple-check I took a small oxygen bottle and ran it directly into the atmospheric analyzer. The computer (after seven minutes— running the analyzer non-stop would wear it out in short order) saw the lack of CO2, sent the order, and the fuel plant let loose more CO2. Ten minutes later, with the oxygen cut off, the computer saw the perfectly adequate CO2 levels and shut off the fuel plant again.
So, an almost purely mechanical solution to a problem works without a hitch. We'll need to transfer another of the Hab's hydrogen batteries and a couple of the handful of un-pillaged solar panels to guarantee enough power for all of this, but otherwise it's good to go. Score one for Earth!
And, as I said, just in time. Tomorrow's the final potato harvest. We're not going to keep more than a small number of the spuds. Most of them are going to be re-planted.
That's right, I said re-planted. And moreover, we're going to gradually move the Hab potato plants and the Hab soil (which is getting pretty worn out anyway) to the cave. Why? Because, at least in theory, more life equals more magic. The rainbow crystals Starlight diddled to circulate water will need all the magic we can give them. Also, if the sun crystals don't produce enough heat once the water heating system is shut off, we'll need to make some rainbow crystals with a heating enchantment to make up the difference. Those will need even more magic.
Of course, the tradeoff is less magic in the Hab, which means that any batteries we have there will recharge about half as fast as they have been. But we can't take plants with us to Schiaparelli. Every kilogram above the minimum means more electrical demand from the wheel motors, which means a shorter per-day travel time. The plants, and the soil they grow in, are a luxury we have to do without. So, if we can't take them with us, we might as well put them where they'll do the most long-term good.
With that in mind, when we harvest the cave potatoes tomorrow we'll also dig up the water pipes and rearrange them. Starlight is already arranging it with her people back home to dump a LOT of water as far back in the cave as we can manage. We'll reconnect the pipes to stretch almost all the way through Tangled Hallway, then use the scrap metal trench to get the water back maybe as far as the Orb. The water will seep through the uncultivated dirt floor and sink to the bottom of the sealed chamber. Part of that will become deep permafrost, but most of it will remain liquid, and the plant roots and enchanted water-pumping crystals will be able to cycle it up from there. The pony planet will monitor flow and shut off the valve on their end when we get as much water added to the system as it can take without risking a return of the black ooze, so we can just leave the tap running when we leave.
It's obviously not a perfect solution. Humans have never been able to make a perfectly sealed, self-contained, self-sustaining environment larger than a bottle garden, and absolutely never with alfalfa and/or potatoes and/or trees of any kind. Balanced complex ecosystems get exponentially tougher the larger you make them. But this is the best we can do to set up a system that, without anyone to maintain it, has a fighting chance to survive the six years until the next open slot for an Ares mission. I just hope it's enough.
MISSION LOG — SOL 394
We're about halfway done transplanting the Hab plants and soil. The ripe tubers have been cut and replanted around the edges of the original cave farm, while the plants (along with a number of alfalfa cuttings) have been planted in Lunch Buffet.
The rainbow crystal irrigation system is already beginning to work— at least, the one that runs from the well at the back of the farm chamber up to the front. Starlight has begun a second, smaller line— a pair of lines, really, to bring a bit of water up from below Lunch Buffet's soil and irrigate the plants we're putting there. In the meantime we'll spend our remaining cave time hand-watering those plants to give them a chance to root and survive.
But we'll be doing that using pony space suits. Our half-assed hydrological system has absorbed all the water the main life support box can give. So tomorrow we're going to pull the life support box and re-install it into the pony ship.
I wonder what Ares V or whoever will find in six years' time? Will it be a crumbling, freeze-dried plant graveyard after something rusts or breaks or cracks and lets the air out? Will they find a terrarium where the plants are surviving but half-starved and sickly? Or will they find a wildly growing jungle of alfalfa and potato plants, half-shaded by an enormous tangle of cherry tree branches?
Common sense bets on the first option, but I'm hoping for the last one. We all are. The farm served us well this past year, and now we're giving back what we can to give it a chance to live on.
MISSION LOG — SOL 395
I changed the Morse code rock message today: "SOL 395 — TESTING ROVER MODS, ON TRACK FOR SOL 451 DEPART." Not that I really needed to, since Pathfinder is working and we have the pony radio for when Pathfinder's no longer an option. But it had been over a hundred sols since I updated my rock blog, and it was overdue, and I felt like it.
After that we all got to work loading up the Whinnybago. From now on everything that's going with us gets stored on board. The food is in, along with my tools, all the spare parts we're going to take with us, and whatever personal items we might take with us. We're not loading the magic batteries yet, because we want to put as much charge on them as possible.
Since we're not taking the batteries with us yet, we have to add their equivalent weight in Martian rocks to the rig. That means going around the area around the Hab and the cave farm to gather several tons of rocks to make up the difference. Even Fireball was grumbling about a sore back by the time we got back to the Hab for the evening. It takes a lot of rocks— seriously, a LOT of rocks— to equal the weight of fifteen slices of quartz five feet long each plus all the smaller batteries.
We're going to take tomorrow off— entirely off. We've earned a vacation day. And then we're going to perform the first serious test of the combined Whinnybago— driving around within two kilometers or so of the Hab to see how far it goes on a full electric charge and how well it handles the little canyons that criss-cross this part of Acidalia. If it can't handle these, then there will be major problems getting up onto Arabia Terra, never mind across it.
Anyway, it's game night tonight. I'm anticipating trouble; Dragonfly asked if she could roll up a new character. I wouldn't worry, except that she asked for a template for a Nac Mac Feegle...
MISSION LOG — SOL 395 (2)
About-So-High Angus MacHenderson, the Nac Mac Feegle, got vetoed, and there was much rejoicing (except by Dragonfly).
But I want a copy of the character for future reference... assuming I make D&D a regular thing back on Earth, I'd like a way to express my displeasure if a DM is screwing us over in a Discworld setting...
Author's Notes:
Most of this was written either while waiting on my free wash and detail job at the dealership (which I drove to in a blinding downpour) or while waiting on the oil change. I wish I'd taken the laptop in to the doctor's office, but when I walked in I wasn't expecting to actually get an appointment for today. But they had an appointment for 12 PM, which meant I got to see the doctor at 1:45.
