by Glenn Damato
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The Oxirotor, as Paige dubs it, consists of sixteen subassemblies separately printed and clipped together. This will take several hours, so I upload the spec and get everyone started. If anything needs to be tweaked, we can re-print only the altered parts. People will stay sane if they can assemble something real. They need hope in the form of something they can touch.
We run a pair of six-gauge cables from the power panel to the centrifuge mount. The hydrogen vent line is a five millimeter hose leading to the threaded connection at the end of the Sabatier tank manifold, and from there the vacuum of space.
Things look good until Shuko shows me a red GNC message:
TG0037 PENDING MIDCOURSE
PROPELLANT DEFICIT
“We’ll deal with it later,” I tell him. “One disaster at a time is enough.”
The subassemblies fit together to form a fat, drum-shaped cylinder just over a meter wide and a meter tall. The water tanks are removable, so they can be filled from the hygiene pit. Fukai oxygen generators have built-in demineralizers so they can take potable water and deionize it before it hits the electrolysis membranes. When the last component is in place, Alison and Mikki wrap an aluminum mesh around the exterior—a barrier to keep us from knocking into spinning parts.
At thirty revolutions per minute, the Oxirotor sings a pleasing thump thump thump song. I can’t take my eyes off it. Ryder cuts the power and stops the rotation with his hand. He switches the oxygen generators on. “We’ll let it spin until the water tanks are empty. That should take about two hours.”
Vijay announces the Oxirotor aboard Resolute is ready for operation.
“Make sure your vent is open at the manifold,” Ryder tells him. “Otherwise the generators will shut down due to hydrogen backpressure. I apologize for the lack of instrumentation.”
“My friend,” says Vijay. “if this works, and I believe it will, as far as I am concerned none of you will never again need to apologize for any transgression as long as you live.”
“Ours is spinning,” reports Tess. “No idea if it’s doing anything.”
Ryder tells us, “The O2 generators feel around half an Earth gravity. They should work.”
The thump thump thump is hypnotic. Time rushes by in a half-awake daze, but we can’t wait a full two hours. Ryder stops the rotation and peers at the tiny pressure gauge. For a few seconds he says nothing and I almost kick him.
“Nine and a half bar!” he yells. “Hear that? Nine and a half bar! How much is that in mass?”
Paige smiles, a new look for her. “We sized the cylinder to be a sixth of the volume of the reserve bank. Twenty bar is full, two days for one person. We got a day’s worth, around eight-tenths of a kilo.”
“Hear that?” Ryder shouts into the com. “Almost a kilo of oxygen in one hour and seven minutes. It needs to run only six hours a day to keep us breathing!”
Can one Oxirotor put out enough for thirty people to breathe? No, but close. My flight suit is soaked with sweat. And I have to pee.
Paige is in a chatty mood and she finds a way to bring Jürgen into our victory. “Jürgen did the right thing by staying out of the way. He’s a geologist, a long-term planner, a poetic idealist. He knew we didn’t need inspiration. He had confidence in us. He wisely let the engineers solve the problem our own way and without distraction. He’s a perfect leader.”
“Yeah, perfect,” I answer. Nothing more, not tonight. Too exhausted.
Ryder points a shaky finger at the warning panel.
A new line, in cherry red.
TG0040 MIDCOURSE CORRECTION
TERMINATED DUE TO
PROPELLANT DEFICIT
TWENTY-EIGHT
First, sleep. No sense trying to resolve the latest guidance system error with a whacked brain. Ryder claims to be too hyped to sleep, so he babysits the Oxirotor. He plans to run it until the water tanks need refills and then discharge the new oxygen into the reserve bank. Nice to see him hyped about something other than spaceball or Alison’s body.
When I wake, the oxygen reserve shows one hundred and three percent, technically overpressurized. Ryder lets out a huge yawn. “Next time there won’t be any room to discharge it.” We decide to spin it periodically to maintain the correct partial pressure.
How serious is the “midcourse correction terminated” message? The GNC displays our arrival time, a good sign. It can wait until we eat. Hungry! Is this breakfast or lunch? The menu wisely offers selections suitable for both.
Shuko’s back in pursuit. He presses his whole leg against mine, softly, sneakily, using his foot as a hook around my calf as he must have seen Alison do with Ryder. I pull away. Can he at least show some originality?
“You were outstanding last night,” he whispers. “An ingenious solution. I still can’t believe it works so well.”
“Didn’t design it, didn’t build it,” I mumble, harshness unjustified.
I avoid eye contact, but he doesn’t care. “Without you, I don’t even want to think about what could have happened yesterday.”
“Thank you, Shuko. Sorry I barked at you.” Annoying and clumsy aren’t crimes. Even if they should be.
Tess is smiling for once. “Captain Morita will now address us.”
Paige waves her spoon. “Please please please be quiet!”
“In six days we’ll be home,” Jürgen tells us. His sturdy voice fills the control center and spreads a sense of strength. “Our greatest adventures and discoveries will soon begin. Yesterday we surmounted the most daunting challenge we’ve ever faced. Everyone played a role toward our success, but I want to take a moment to recognize four individuals, four quick-thinking engineers who conceived the . . . what did you name it, Paige?”
“Oxirotor!” Paige cries. “The Oxirotor!”
“I want to recognize Paige Weber for envisioning the centrifuge solution,” Jürgen continues over a rising swell of applause. “And Ryder Lawson and Mikki Tischler for designing the Oxirotor, and Senuri Kumar for coordinating assembly and testing.”
Cheers erupt from the com. Ryder glances at me, then Jürgen’s vid. Shuko pushes away from the table and flips backwards toward the hygiene pit. Mikki stares at Jürgen, no longer chewing, her face empty of emotion.
Jürgen. Cabrón!
Is he maybe saving it for last? Of course not. No mention at all.
“We’ll be facing even greater challenges,” Jürgen goes on. “Yesterday we displayed the sort of invincible spirit—”
“Wait!”
All heads snap to Mikki. “Are you fucking kidding me?”
I touch her wrist. “Mick, leave it.”
“You!” She thrusts a trembling finger at Jürgen. “Where the hell were you?”
Jürgen closes his mouth and frowns.
She’s not done. Not even close. “Eric! Eric, you son of a bitch. Thanks to you, I thought I would die. Or watch my friends die.”
A tiny voice replies, “You have no basis to blame me.”
Mikki grabs my collar. “This person! We made it because of this person! You had half of us dead. You were sure of it!”
Paige folds her arms. “Jürgen said everyone played a role.”
Mikki twists away from the table and assumes her rolled-into-a-ball float position. I wait for Jürgen to respond, but the vid from Independence is empty except for someone’s leg.
My turn. “Yesterday we had a scare.” For a moment the words won’t come until I listen to the vent fans. “What did we learn? First, keep calm. I was so terrified I couldn’t think. Reminds me of taking math and science entrance exams when I was thirteen. Just tell yourself, work out the problem. Think of nothing but the problem.” For some reason I look to Ryder. “Second, we need each other. Each of us can provide a piece of the solution. Everyone is essential in their own way.”
What else? The fans drone on.
Eric says, “Want to know what I learned? I should have kept managing the OGS temps like I did the first three weeks
. It was working well enough. But people got nervous and threw fits over the shutdowns. Whose fault was that, Cristina? Who was I trying to please by going to the low-flow parallel mode that eventually burned out the seals? I learned to listen to my own engineering judgment and not surrender to the emotional opinions of people who lack that judgment.”
Norberto calls out, “The shutdowns were getting closer together! No one forced you to change anything.”
I have more. “The first step in solving a problem is to recognize that it exists. We have a new problem to work. Look at your nav. Propellant deficit. A hundred and seventy seconds of thruster propellant remain. Why doesn’t the GNC think that’s enough to do course corrections? What are we going to do about it?”
Darien responds. I don’t know him well. He looks and sounds too young to be here. “Me and Eric looked at the parameters last night. The correction estimates become more accurate as we approach Mars. Yesterday it started thinking we might need more delta-V to adjust our trajectory. We need to hit the atmosphere within a narrow entry corridor. The aerobraking has to be exact. If the angle or the timing is off, we’ll either burn up or fail to shed enough velocity and fly past the planet.”
Ryder asks, “Didn’t we start with a five percent surplus?”
Eric still sounds as if he blames me. “We ate up the margin because the GNC ran the initial ten-hour boost against biased position inputs. The first and second corrections were a lot bigger than planned. Plus, we launched seven days early, which makes our trajectory a bit longer.”
“But we fixed the bias,” Alison says. “So why didn’t the system set us on the correct trajectory?”
“It did set us on the correct trajectory,” Darien tells her. “But due to inherent precision limits and gravitational perturbations, it can’t set us on a perfect trajectory. That’s why we need several midcourse corrections. Picture it like a boat influenced by winds and currents. Even if you point the boat in the right direction, in order to arrive precisely at the dock you need to correct with the rudder to counteract all the natural forces affecting your course. Our trajectory is curved by the sun’s gravity, but we’re also influenced by the weaker gravitational fields of every planet, every moon, every asteroid. The total effect is impossible to calculate in advance so we have to position-check and correct as we go.”
Mikki uncoils herself. “Why is this so hard? Automated spacecraft have been landing on Mars since nineteen seventy-six.”
I know the answer. “Margin of error. We’re moving about six times faster than the old probes and our landing mass is a hundred times heavier. And our trajectory has to be more precise for the aerobraking to work.”
Eric reports, “Darien and I came up with a solution. It won’t be easy, and the sooner we get started the better. We abandon one spacecraft and transfer the remaining propellant to the other four. The other craft each take one or two extra people. The propellant is argon, an inert gas. Since the pressure is under a thousand kp we can do a simple hose transfer.”
I have to point out the obvious. “Land with only four spacecraft? We’ll have twenty-five percent less of everything.”
“Design safety margin,” says Darien. “One spacecraft can actually support up to thirty-six.”
Ryder turns to Eric. “Correct me if I’m wrong. It’s not really more propellant we need. We need more velocity change.”
“Well, yeah, but the thrusters use propellant to change velocity.”
Darian’s eyes light up. “I get it! Reduce our mass, greater velocity change with the same amount of propellant.”
Eric shakes his head. “We’d have to lose tons.”
“Not necessarily,” Darien tells him. “These deficit messages just showed up yesterday. Twenty-four hours ago, the GNC thought we had enough propellant. The difference between the predicted and plotted velocity vectors can’t be very large. It might only be a few meters per second.”
I try to keep my tone non-confrontational. “Eric, do you agree the propellant deficit is probably small? Could we wipe out that deficit by losing some mass?”
“I don’t know, Cristina. I do know the propellant transfer would work for certain. Darien believes your idea is theoretically possible. But what mass can we give up?”
The answer is water. The designers supplied the TMI with three hundred liters for the OGS to electrolisize. About one hundred and eighty liters remain, plus forty-five liters of electrolyte inside the units themselves.
“I can vent it through the relief valves,” says Eric. “Assuming none of it freezes in the lines, that lightens each spacecraft by around two hundred and twenty kilos.”
I ask, “How much can we spare from the regular tanks, the potable water?”
That turns heads. Paige twists her mouth. “Our drinking and washing water?”
“It’s recycled by eighty percent, so a little goes a long way.”
Paige screws up her face. “What do you mean, recycled?”
“Haven’t you been learning the systems? There’s a reverse osmosis unit that purifies urine and a condenser that pulls moisture from the air. All that goes back into the supply.”
She covers her eyes. Ryder strokes her hair. “Where did you think it went after it’s sucked down the tube?”
Math time. “We started with four eighty-liter tanks. We’re down to a hundred and seventy-five, pretty low because the Oxirotor has been using some of it. We’ll need to electrolyze another thirty-five. If we don’t wash for the next six days and we find drinkable water after landing, we can dump at least half of what we got.”
Shuko tells us, “Lowering the cabin temp will reduce perspiration and body odor.”
“Wonderful,” Mikki mumbles. “We get there filthy and freezing.”
But we get there.
Darien and I work out the specifics. Each spacecraft will keep one hundred liters of water in case finding ice at the landing site proves tougher than anticipated. No clothing or medical supplies will be sacrificed. Food? The hygiene pit is surrounded by stainless steel tanks containing four tons of oils, powders, pastes, and pellets—nutrient stock for the food printer. Anonymous decision: every gram of nourishment will be kept.
Liberty can afford to jettison 295 liters of water. I put the GNC into simulation mode and deduct that mass from the stored value. Numbers flash—the final verdict is green:
PENDING MIDCOURSE TRAJECTORY CORRECTION
14:20:00 PCT 55 TAURUS 53
ESTIMATED DURATION 00:01:56
“Darien’s right,” I announce. “A little goes a long way.”
Eric runs the necessary commands. Water vents and bursts into vapor outside the windows. The cloud instantly freezes into thousands of swirling ice crystals sparkling in the sunlight. Paige and I press our faces against the cool glass and enjoy the enchanting sight. Is a snow storm something like this? The crystals from the other spacecraft quickly cross the kilometer distance and fill the blackness with countless sparks.
Paige says, “They look more like stars than stars.”
The GNC flashes red:
TC0932 PLATFORM ALIGNMENT FAILED
What the hell did we just do?
Eric announces, “The ice crystals confuse the tracker. It can’t find the nav stars.”
We wait. The swarming sparklers gradually dissipate. Sometime after midnight Norberto and Darien manually guide Liberty’s tracker to Deneb, a navigation star separated from Mars by roughly ninety degrees of arc. This lets the GNC use both Deneb and the center of Mars’s disk to precisely orient the spacecraft. A minute later the GNC shines green:
ALLIGNMENT COMPLETE
00:39:43 PCT 56 Taurus 53
It rapidly sets up for a course correction. “I’m just gonna point my feet this way and hold on,” Ryder says as he rotates his body. The thrusters fire and the wall separating the control center from the equipment bay becomes a floor. The weak acceleration, just five percent Earth gravity, sets everything spinning and swimming—and Mars gravity will be
eight times stronger.
Ryder twirls Alison on his left arm. Her body sweeps sideways and momentum sends them both gliding and giggling across the compartment.
A touch on the elbow—qué demonios! Shuko, with a stern frown. He wants to dance? I give two head shakes. “Dizzy enough as it is!”
Bad answer! Does he now believe if not for the dizziness, we would have twirled together?
The GNC calls, “Thrusters off,” and the floor drops away.
ETA PROTONILUS MENSEA PM1
09:27:00 PCT 3 GEMINI 54
Paige and Alison cheer and Ryder slaps me across the shoulders. Almost a punch, but somehow good—infinitely superior to a flimsy elbow grab.
Eric’s voice is drowsy. “We’re set for another correction on two Gemini. And with that, I bid everyone good night.”
Alison turns to Ryder. “I don’t get this Taurus Gemini thing. It means the month, but we have twelve months in the Mars calendar, so why can’t it just be December, January, like regular months?”
Ryder releases yet another lion yawn. “The number of days per month are completely different from Earth, and the big orbital eccentricity means the month lengths vary a lot. Today is fifty-six Taurus, the last day of Taurus, the last day of the year.”
Shuko says, “If tonight is the new year, there should be a celebration.”
I launch myself into the hygiene pit before anyone else can beat me.
TWENTY-NINE
It isn’t exactly a celebration, but at least everyone agrees to gather in their respective spacecraft control centers at 23:30 to await the beginning of Year 54.
The expected Jürgen speech doesn’t come. Instead, Senuri speaks the two magic words guaranteed to get everyone’s attention: Discovery Team.
“The first survey expedition will be on seven Gemini, four days after landing,” she says. Her tone is crisp and convincing, the voice of someone accustomed to being in charge—but it lacks charm. “Jürgen and I will select two people to accompany us. This first trip runs less than twenty kilometers so we avoid potentially hazardous terrain—”
