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The Maretian

by Kris Overstreet

Chapter 110: Sol 194

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“Venk, have you got a minute?”

Venkat looked up from his notepad, where he’d been doodling numbers, graphs, and rough diagrams of the MAV. “Of course, Annie,” he said. “What’s wrong?”

Annie stepped into his office, shutting the door behind her. “What makes you think anything’s wrong?”

“Well, for starters you’ve just said two almost grammatically correct sentences in a row in private without any profanity,” Venkat said. “Also, you usually greet me with a demand of some kind or a complaint about how tough your job is. That plus your tone of voice tells me you have tremendously bad news for me, or else you want a special favor.”

“Fucking Sherlock Holmes,” Annie muttered. “Yeah, you’re right. I want a special favor. There’s a reporter who’s done me favors in the past, and she wants a one-on-one interview with the alien captain, Cherry Berry. I want to know when we can get her a day on the Pathfinder chat.”

Venkat dropped his pen. “Annie, do you have any idea what you’re asking?” he said. “Lightspeed lag is well over twenty minutes now. And that’s not counting typing time on both ends. Total bandwidth is well under a kilobit per second. We’d have to push everything aside for that, and your reporter might get ten, eleven questions and answers, tops. Can’t she settle for email and follow-ups?”

“She says she wants a live interview,” Annie grumbled. “I know the problems, Venk, I see the time-stamps on the chat. But this is Berenice MacReady at the Times of London. She’s practically our biggest cheerleader in Europe. Do I need to remind you about all the ESA funding that’s going into the rescue effort? Because Bernie reminded me, Venk. Gave me chapter and fucking verse on it. And she’s done her best to sell our spin on every aspect of this thing, so we owe her big.”

Venkat sighed, leaning back in his chair and considering the logistics. “If we do this, every other news source is going to demand interviews, too,” he said. “Can you deal with that?”

“I’ve been dealing with it for weeks,” Annie said firmly.

“NASA can’t be seen to play favorites,” Venkat continued. “That means the only way we don’t get a black eye from this is if we arrange things so that Cherry requests the interview. You’ll have to make that happen, in secret.”

“Doable.”

“Your friend will have to be on-site either here or at JPL,” Venkat said. “Considering the chaos in Pasadena right now, here would be better. And she’ll have to be here for days until we hit a day with no urgent business. Is she good with that?”

“She’s already part of the press pool here,” Annie said. “She lives in a microsuite hotel down in Texas City. It won’t be a problem.”

“And impress upon her,” Venkat added, “that her time is extremely limited. The first two hours of a day is ours for daily business. She gets nine hours after that, if we don’t need to break in for some kind of emergency. So she’d better get what she needs as quickly as possible, because she won’t get a second chance.”

“I’ll tell her.”

Venkat sighed. “Then set it up,” he said. “And you and she both owe me big time, Annie.”

“Put it on the tab,” Annie replied, utterly without shame or gratitude. She glanced down at the desk and saw Venkat’s scribbles. “What’s this all about?” she asked.

“Drinks-napkin guesstimates,” Venkat said. “Trying to get some idea of how much good it would do to bolt the pony rocket engines onto the landing stage of a MAV.”

“Isn’t that JPL’s job?”

“Yes, but it gnaws at me,” Venkat said. “And it’ll be a couple months before JPL gets serious about it. Their hands are full with Sleipnir right now. So I’m working the numbers for my own satisfaction.”

“How do they work out?” Annie asked. “It seems to me it’d make things worse instead of better. For years you’ve had me explain to reporters how important it was to keep the MDV and MAV as lightweight as possible to save fuel.’

“How much do you know about thrust-weight ratios?”

“If thrust to weight is about one, you hover. If it’s more than one, you fly. If it’s less than one, you either stay on the pad or you crash.” Annie shrugged. “After that it’s egghead territory, and I get lost.”

“Okay.” Venkat pulled out a fresh sheet of paper and began drawing. “The MAV landing stage has a thrust-weight ratio-“ he labeled this TWR- “-of 1.2 in Martian gravity. That’s very little, but it’s all it needs to slow the MAV from about one hundred meters per second to a safe soft landing in under three minutes.”

“Why not more power? Bigger engines? More fuel?”

“The more weight we put on the craft to start with, the more fuel we need to launch it from Earth, and the harder it is to soft-land on Mars,” Venkat said. “That trade-off, by the way, is why the MDV landing is the single greatest point of danger for Ares astronauts. Once an MDV enters atmosphere, there’s no abort scenario. It’s land or die. Building it to include an abort mode back to orbit would make it as big as the MAV.

“But I’m getting away from the MAV. The MAV runs on hydrazine using a catalytic grill to make it hypergolic. The thrusters on the MDV use the same fuel. Between the residue in the Ares IV MAV and the Ares III MDV, we might get one minute of flight out of that stage. In theory that’s bonus acceleration, an early boost to orbit.”

“You say in theory,” Annie replied. “Obviously not in real life. Why?”

“In Mars gravity, a TWR of 1.2 means only 0.76 meters per second of acceleration every second. That means, after one minute, the whole ship would only be going about forty-five meters per second. Coming down that's OK because the MAV uses parachutes and aerobraking to go from orbital velocity down to below 100 meters per second, and the rockets can take it from there.

“But Mark and friends need to get to something like six kilometers per second, and while forty-five meters per second is nice in theory, it's suicidal in practice, given the time required for staging. At the end of one minute, the rocket would just barely be even with the rim of Schiaparelli Crater. In less than ten seconds it would begin falling, and twenty second after that it would hit the ground again. The MAV pilot would have to manually light the first ascent stage engines and release the launch clamps connecting it to the landing stage without a bobble or a hitch, or else they die. Or, if they do it slowly but well, they end up using more fuel in the first stage than if they’d just launched normally.

“So, long story short, re-using the descent stage alone doesn’t buy us enough speed or altitude to be worth the danger to the crew. But if we add the alien ship’s main engines to the mix, the math changes.”

“How so?” Annie asked. “More weight, right?”

“Yes, more weight,” Venkat agreed, “but a hell of a lot more thrust. Our ballpark estimate is that those three engines at full throttle could hover forty-five tons of weight on Mars. That means they produce forty-five Martian tons of thrust, for a TWR of one. But if they’re just lifting themselves, that TWR is a lot better.”

Annie shook her head. “You’ve lost me.”

Venkat tapped his chin with his pen. “Okay, forget the MAV and the ponies for the moment,” he said. “Let me tell you of the thrilling adventures of Captain Buck Watney in his faithful potato-powered spaceship.”

Annie smirked. “Thunderspuds are go?”

Venkat smirked back. “Something like that. Thunderspud 1 weighs fifty-two tons at launch, and its first stage produces sixty-two and a half tons of thrust, for a TWR of about 1.2. But he’s in a hurry, so he needs some boosters to get to space quicker.”

Annie nodded. “Okay, I see that. Kind of like the space shuttle or Falcon Heavy?”

“Exactly. But let’s say a certain ex-president sells Buck Watney a couple of boosters with his name on them.” Venkat drew a couple of missiles next to a more conventional sci-fi rocket shape. “Let's say each of these weighs five tons and produces four tons of thrust, for a TWR of four to five- less than one. What that means is that, launched alone, these so-called rockets wouldn't even leave the pad until half of more of their fuel was expended.

“Strapping two of those onto Thunderspud 1 produces a craft that weighs sixty-two tons and produces seventy point five tons of thrust at liftoff, for a TWR of 1.137.”

“Which is less than 1.2,” Annie nodded. “Congratulations, Watney's just wasted the Space Orphans and Widows Fund in order to fluff an ex-president’s ego.”

“Right. And Buck Watney is upstanding, honest, and not an idiot,” Venkat said, “so he doesn’t do that. Instead he chooses the Rainbow Mustang Sparkly Necklace System. The system weighs seven and a half tons, but produces a whopping forty tons of thrust. Now that’s a different story! Wrap one of these around Thunderspud 1 and you get a ship that weighs 59.5 tons and produces one hundred two and a half tons of thrust at liftoff, for a TWR ratio of about…” Venkat pulled a calculator over and did the math. “…1.72.”

“Which is lots more than 1.2, right?” Annie asked. “Buck Watney must really be moving.”

“Not that much,” Venkat admitted. “To give you an idea, the Saturn V and the Space Shuttle both launched at about 1.5 TWR. But fuel consumption lightens the load, so both vehicles had a peak TWR of about 3. We launch unmanned vessels at a peak TWR of 15 or even higher because, unlike people, probes don't get broken ribs and internal bleeding due to high G loads.

“But getting back to reality,” Venkat said, “those numbers I gave you didn’t come from nowhere. The MAV with landing stage is fifty-two tons, including fuel. On Mars it has a TWR of 1.2. And the pony rockets- the Rainbow Mustang Sparkly Necklace System- weighs four and a half tons, plus about three more tons for the batteries needed to power them all for about a minute. On Mars they can lift about forty-five tons. And one minute of acceleration at 1.72 TWR on Mars comes up to about three meters per second of acceleration. At the end of that minute, the MAV would be going roughly two hundred meters per second at an altitude of almost six kilometers- a safe speed and height to cut loose the landing stage, light the first ascent stage, and really begin moving.”

“Okay, I’m up with you now,” Annie said. “But why not add more batteries or more fuel?”

“For one thing, the ponies only have materials on hand for about a hundred batteries maximum,” Venkat said. “Beyond that they’d have to make the frames, controls and connections from scratch. For another, we’re not one hundred percent sure they can make more hydrazine, and the landing stage engines aren’t compatible with any other fuel they might be able to mix from materials on-site.

“But the biggest reason is weight,” Venkat said. “We can’t extend the pony engines to run for the full burn time of the first ascent stage. That’s just not an option. And we don’t have a safe, non-destructive way of detaching those engines when they burn out. There’s a chance the parts would collide with the engines after release and wreck the ship. So if we put them anyplace other than the descent stage, they’d be dead weight for at least one minute of the ascent. And we can’t afford any dead weight at all on this launch.

“So, if we can find a way of doing it safely, we’re going to attach the pony engines to the landing stage, burn it for a minute, and drop it all and let it crash back to Mars.” Venkat sighed. “It’s a horrible waste, but unless we can figure out a way to replace some of the upper stage engines with the pony engines, it’s the most efficient way to use them.”

“Huh,” Annie said.

“Beyond this, Bruce will tackle the other end of the equation,” Venkat continued. “That means ditching everything Mark and friends can live without to make the ship lighter. Any weight we can strip from the MAV will increase its TWR and make all the engines more efficient. That’s where our real hope for rescuing them lies- that and the Sparkle Drive.” He shook his head and added, “Gods, I hope we don’t need to use it.”

“Huh,” Annie repeated.

“Did I lose you again, Annie?”

“No, no,” Annie said, smirking. “I’m just wondering how Watney will react when I tell him we’re changing the MAV’s name to Thunderspud 1.

“What?” Venkat glared at Annie. “No. No no, no no no. You are not going to-“

“See you later, Venk,” Annie said, “I have a press conference in seven minutes.”

“Don’t you dare tell him, Annie, I mean it!” Venkat snapped. “Do you hear me? You get back here!”


On Mars, inside the crystal cave extending under Site Epsilon, the temperature warmed.

The alfalfa plants, extending only a foot or so above the surface, delved several meters below, deep below the cultured topsoil painstakingly developed by the castaways and into almost virgin Martian soil, pushing and prying against the gradually melting permafrost. The roots brought with them bacteria from the upper soil levels, mostly beneficial, but a few less so.

The newly reinforced, airtight silicon dioxide and regolith-concrete walls of the cave acted as a superior heat insulator, allowing the heat produced by the solar lighting system, the water heating pipes, and the space heater to remain in the cave. The heat warmed the air, warmed the plants, and gradually warmed the soil, to depths none of the castaways were aware existed.

The castaways thought the lava tube was symmetrical, sloping down as it approached its source at the center of the ancient dead volcano. They were wrong. The dust and soil that had blown in from the surface sloped down, but the rock beneath it sloped up as you reached the rear of the cave. Put another way, the dirt near the entrance was deeper, far deeper, than the vast open area above.

And in its depths, below the plain water ice permafrost, there were more ancient deposits, of water and of other things that welled up from the depths rather than down from the shallow layers of Martian sand and rock.

Trapped in those deposits, where they had remained for uncounted millions of years, were pockets of methane hydrate, ice that contained large amounts of methane in its crystalline lattice.

The alfalfa roots reached down, bringing warmth and bacteria to the depths.

The first of the methane pockets began to thaw.

Tiny trickles of methane gas began, very slowly, to permeate up through the root system, displacing the oxygen in the soil. Beneficial bacteria began to die off.

Less beneficial bacteria tasted the methane and found it good.

They were fruitful, and multiplied.

Author's Notes:

This is about as close as I'm going to get to putting current politics into this story.

Anyway, yeah, the pony engines going on the descent stage isn't a done deal yet, but it seems like the best option for 'em at the moment. This chapter was originally going to be an explanation of why throwing the pony engines on the MAV at all made sense, in response to a comment to the previous chapter, but I spent so much time on the answer that I said, "screw it, this becomes today's chapter."

As for the other thing... we know Mars periodically lets loose with small releases of methane gas. The combination of trace water vapor and oxygen in the atmosphere plus unshielded ultraviolet radiation means methane doesn't stick around long, and that means that Mars's trace of atmospheric methane has to be continually replaced from somewhere. One theory for where it's coming from is deep subterranean pockets of ancient Martian bacteria, struggling to survive after their original biome died out, releasing methane. Another theory- more probable- is that the methane is bound up in permafrost hydrate/clathrate deposits, which thaw or sublimate every once in a while as they're exposed to the surface. Curiosity's on that case, but we haven't got a definitive answer yet.

But it's probable enough, for purposes of this story, for me to stick that time bomb in the cave.

The sound you hear is the Galactic Ghoul laughing.

EDIT: Venkat's forgot something in his number-crunching. I'm leaving the error in to be caught by Bruce Ng much later in the story.

Next Chapter: Sol 195 Estimated time remaining: 18 Hours, 39 Minutes
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