“Ah, jeez, Jeff, I didn't need to hear that!”
“Guy was dead in an instant. I bet he had no idea what hit him. Spin the throttle, whack, end of story.”
“Speaking of end, Jeff, we better start getting into that checklist. Unless your subconscious is prodding you.”
“Not yet. But I have a feeling. Let's think about the throttle controls on the engines.”
***
The problem was lurking in the throttle control programming. Under certain circumstances, Jeff would not be able to turn off the mass flow to the engine. He reported it to the Commanders.
“Our engines work by pumping LOX through the core of the thorium reactor, where all the heat is generated. The liquid transforms to supercritical oxygen, which is pushed to the combustion chamber where it meets liquid hydrogen, also in a supercritical state from cooling the engine bell. They combust, and fling water plasma out the back. I have discovered a flaw in the programming controlling the valving for the LOX. We need to implement this code change, or else we risk a stuck-open LOX valve, which will exhaust our supplies through the thorium core, and quite probably eat through the LOX pipe, causing an explosion.”
“Good God, man! I suppose we have to do it now.”
“The circumstances under which this is likely to happen will almost certainly not occur in the next six hours, but I would rather be sure. I kept thinking about an incident I had with a broomstick, and I realized that a stuck-open throttle would be our death.”
“What are you going to change?”
Jeff walked him through lines of code. “So, you see, given these limits on tank pressure and the logic for sensor interconnection, if we were hit with an electrical disturbance for any reason—bad ground, solar flare, whatever—the system will assume that the tank is overpressured and open the LOX valve until the sensors drop. But they won't drop, and the valve stays open forever.”
“Bad.”
“Double-plus ungood,” said Jeff. “So, we institute a time-limit on the valve opening and shut it again, and mark the situation as critical while keeping the valve under manual control, relying on the pressure relief valve to act if we don't.”
“Got it. What does Scott say?”
“Total approval—logged into your console.”
“I see it,” said Commander Smithson. “Concur, Mike?”
“I concur with the fix. Implement it, please, before the flyby.”
“Thank you, Commanders.”
***
With the glitch fixed, and no further prodding from his subconscious, Jeff enjoyed the flyby. They were skimming mere kilometers above the top of the Martian atmosphere. Scott was staring at the thermocouples dotting the skin of both spacecraft like a hawk.
The engines were firing steadily, so the crew experienced a mild sensation of up and down. Everyone had a job. Jeff monitored the health of everything but the reactor, that was Duane's job. Scott watched the skin temperatures, Benjamin was staring at the various navigation instruments. Harel down in Life Sciences didn't really have much to do once the hydroponics were secured, but he was monitoring the consumables like LOX and water. Mickey was monitoring the radio and photophone, and Ragesh kept up a running log of data on the voicelink to the Moon in case the datalink got lost.
The muted roar of the engines would go on for about an hour, forcing the Mars Expedition out of the ecliptic on a course to intercept the comet that McCrary had targeted. Mars's orbit was within two degrees of the same plane, whereas the comet was flying some thirty degrees above the ecliptic. Mickey remembered asking Benjamin about the maneuver.
“So why do we have to fire the engines right at the closest approach? Always thought that was the most critical time—why mess it up with a thrust maneuver?”
“When you fire the engine at closest approach, you actually get better propulsion out of the engine than you could on a test stand. The math is pretty easy...”
Mickey held up his hand. “Don't need it. You're our guy, and if something happens to you, we just thaw out Tomas on the Burroughs or Federico on the Bradbury and give them the problem.”
Benjamin looked crestfallen. Mickey took pity on him. “Look, Ben, you're going to start using funny looking letters like those blocky E's or those stretched out S's, and my neurons just go bonkers. Best not to try. I know you're totally into this. How about this, I try to get you enthused about how to detect circular polarization in a radio wave. Sound like fun?”
“Not really. I don't even know what that means.”
“There you are. To each his own. By the way, what's that called again?”
“The Oberth Effect.”
“I promise to check it out in the 'pedia, okay? If I want more, I know where to go.”
He did check it out, and asked Benjamin some insightful questions about it, but absolutely refused to look at any equations.
***
“F plus fifteen minutes, thirteen seconds. We should be starting to get fade from the Moon.”
Mickey listened to the warbling tone being projected from the Moon. They were recording their reception of the analog signal for later rebroadcast back to the Moon when the Burroughs/Bradbury came out from behind the planet after rounding it. The patterns of fading in the signal should give the scientists stuck on the Moon something to chew on—new telemetry about the Martian atmosphere.
“Nothing yet. Wait! I've got fade,” Mickey reported. “Down another thirty decibels. Aaaand...that's it. Contact lost. You can stop anytime now, Ragesh.”
Ragesh sighed and took a swig of water. “Funny, you can talk with a buddy for an hour and never have a problem. Get stuck behind a microphone for the same length of time, and you get all kinds of weird symptoms—dry mouth, choking. What's up with that?”
Mickey chuckled over the intercom. “No idea. Another fifteen minutes or so, and we can get up and move around again.”
***
By common consent, the Commanders agreed to keep the ships together for a full week after flyby, just in case something had come unglued during the maneuver. There was minor damage—mostly some things that weren't tied down being shaken loose from where they were located. The worst accident was a hydroponics drip feed hose working its way out from a fitting. They lost perhaps a cup of nutrient fluid before it was discovered and fixed.
Benjamin was the only one who wasn't taking things easy. The engines were shut down, and their course was fixed by the immutable laws of physics. But he was furiously working on the navigation problem. The closer they were to Mars, the easier they could fix any mistakes.
The Moon came out from behind Mars within a second of its predicted time, and the crew greeted the receipt of the warbling tone from around the dark side of the planet with relief. They were back in touch with the Moon. They used the photophone as a kind of radar; the round-trip time, combined with the coordinates from the laser mount, served the same functions as a radar did. The fly-by was successful to the limits of their instrumentation. The Mars Expedition would arrive at the comet within five months, and with less than fifty kilometers in possible error.
The party that night was quite raucous.
The Long Dark
Enroute to Comet C/2082 D4 (PanSTARRS), May 2 2083, 1300 GMT
Two weeks after the fly-by, the crews of the Expedition again strung the ships in an array, but this time, it was two complete ships rather than splitting them into four pieces.
“I never liked that,” said Jeff. “I understand the argument that it made the rotating array more stable, but I just hated the vulnerability of not having any way to maneuver out here.”
The Commanders agreed with him, and they used the bolo arrangement. The iron ring, which figured so prominently in the previous array, was still required as the framework for the Mitt. Attaching the ships to it, though, would create unacceptably high forces on the ring. Instead, the tethering cables were strung through the sixth-points of the ring—every sixty degrees around the circumference—leaving the
ones directly in line between the ships unstrung. This loaded the ring a bit more uniformly.
The rotational speed was lower, since the engine sections were hanging further back, and thus, under greater centripetal force. Exercise equipment was dismounted from the living section and remounted in the lower decks. All crew had to spend at least three hours per day in the lower decks, where the centripetal force was about one-half that of Earth’s gravity, instead of hanging around the Command Deck, where the gravity was more like the Moon.
Life settled down. If any of the crew were upset about not setting foot on Mars, they kept it to themselves. After all, they were after much more important victories.
***
“I think I've got it,” reported Benjamin one afternoon at lunch. “At least, it's still got a little bit of a coma.”
“Tell McCrary,” said Commander Standish. “I'm sure they're running a pool on what day we'd find the damned thing.”
The Expedition was closing on C/2082 D4 (PanSTARRS), or as everyone called it, 'Eighty-two'. The comet was either a fairly recent one or the long-boiled remnant of a much larger comet. It was approximately a hundred meters in length, and about half that in diameter. It resembled nothing so much as an upsized fifty-five-gallon drum, slowly tumbling through space. It was pockmarked and somewhat graveled, with faint jets shooting out through small fissures on its surface.
“Now what?” was the common thought as they drew ever closer to the enigmatic object. Comets had been probed before, but they would be the first humans to set foot on one. If they landed, which might not happen.
The Commanders edged up to the object, and transmitted video back to the Collins. About six hours later, they began receiving the first of a bewildering array of documents, advice, and requests for more information from Collins techs who obviously didn't have enough work on the Moon to keep them busy.
“We're only twelve people, McCrary, give us a break!” said Roger at one point.
“Well, go through your roster, and wake up a few more,” he said. “I know you're going to tell me that you can't handle the increased load on the life support system, but I think you’re wrong. I've been looking over the original Mission profile, and I think they designed in some extra capacity. For instance, when you would have landed the ships on Mars and started waking up people, there would be a time between the initial landing and the occupancy of the underground bunkers where the entire company's life support is derived from the ships' systems.”
“True. It was always meant as a temporary measure. For instance, we were not allowed to wake up anyone until the extra hydroponics trays started producing. A young plant can't suck up as much carbon dioxide as a fully grown one, so they must have been drawing down the adsorbers.” Smithson rubbed his chin. “I can't see where another couple of bodies would badly overstress our systems.”
“Remember what you want to do—capture the comet. That's why we sent you that hunk of carbon. You can make fiber-reinforced mylar out of it, just like we have. Wrap the comet in that, and take it along with you to the next asteroid.”
“As easy as that,” said Roger. “Look, McCrary, it might seem easy to you. You're not looking at something the size of a parking garage tumbling around a couple of hundred meters off your bow.”
The ships rested in the lee of the comet—far enough away not to be affected by anything the tumbling body might throw off. A couple of stray pebbles flung off the comet could wreak havoc if they stuck something both delicate and irreplaceable. Meanwhile, the rest of the crew, in teams of two, reviewed the automated systematic sky survey that the computers on both ships were cranking out.
In this, the fact that the Burroughs and Bradbury were spinning around each other was a net positive. It meant that the telescopes could slowly traverse in the x-axis and rotation of the array would allow them to cover the entire sky. It also meant they had a stereo baseline—the distance between the two ships. It was useless for parallax measurement of any object beyond about Saturn, but since they were looking for asteroids inside the orbit of Jupiter, it was ideal.
The computers ground through the observations, operating the star-spotting telescopes in precise alignment with each other. Whenever there was a candidate that seemed to fit the parameters, the computers would display the coordinates, and ping the observing team. They would then try to figure out if it warranted further investigation.
In the beginning, there was really no way to disqualify any given contact, so they had to look at all of the possible contacts. For this, they had to activate special cameras in the tails of each spacecraft. Normally, they were there merely to watch the engine bells of the engines for problems. Now, however, they represented the furthest distance between two identical sensors. The observing team set up the coordinates, and waited for the computer to signal that the cameras were ready. The observing team had to ensure each camera was pointed at the same object—difficult to do sometimes when you were looking for a dim white dot amongst a field of white dots.
When everything was ready, the computer took an image, then locked one camera and replicated the angle on the camera mounts to the other camera. It then measured just how far it had to turn the second camera inward to make its image coincide with the other camera's image. This gave it a true parallax, and from there it was a simple matter of trigonometry to determine the distance to the object.
McCrary suggested that they limit their search to anything within twenty million kilometers. Further out than that, and they would miss the launch window back to Earth. There was some good-natured grumbling since nobody believed that there was an asteroid of the shape, size, and composition they needed: roughly five hundred meters long, about one hundred fifty meters in diameter, and made of iron-nickel.
McCrary laughed gently. “Oh, there will be plenty of rocks, but you'll want the iron one. And I'll bet you find it within the month.”
***
One month was a long time when all they had to do for entertainment was watch a hypnotizing tumble of dirty-white shooting out shiny gas from all over its skin. Everyone hated observations at first, then it became a game. Who would find the Sorcerer's Stone? The betting had gotten rather heated, so much so that the Commanders were compelled to lock up the wagers, lest there be theft.
Ding went the computer, while on the monitor, a line of coordinates glowed. RA 12h32m56.336s, DEC -03h04m22.333s.
“Looks okay,” said Mickey. He and Harel were the OTs for this watch. “Set her up?”
“Sure. Not too far, coordinate-wise, from the last one,” he said.
“Uh-oh, that might not be good,” said Mickey. “That would mean they might be companions, and that means no hootch.”
“I don't think they sampled that last one correctly,” said Harel. “You can't just blast one spot. It's like trying to figure out what Earth is made from by looking at one pixel of a photo from the Moon. I think they just happened to hit an ice patch on that one. It was way too dark to be an iceball. Ready.”
“Verified. Now, for parallax.” He punched the button, and watched, fascinated, as the computer took the two images, one from each sensor, and overlaid one atop the other until they matched. The computer was able to do it faster than any human, but it still looked spooky to watch on the monitor. When one image perfectly matched the other, Mickey pushed the solution button, and the computer immediately displayed the distance to the object: seven million kilometers——practically next door!
“Close one, too. I'm gonna call Benjamin and warm up the laser,” said Harel.
Mickey shrugged. Harel always seemed to think that every target was the real deal. The distance measurement did do one thing—it demonstrated that this asteroid was not related to the previous one they observed.
“We got a firing solution,” said Harel. “Got the main scope and diffraction grating in place. Punch that sucker.”
From a high mount above the Command Deck, a long-range communications laser stirred to life. It swung in its mount
and laced an invisible line of ultraviolet light towards the computer's coordinates. A thin drumming filled the observation deck—Harel's hands were tapping the table.
“Twenty-five seconds, one way, Harel. Chill out.”
“Yeah, but I'm thinking of the hootch,” said Harel. “Fifteen seconds left.”
“Better not do a countdown. I'm sick of them,” said Mickey. A light blinked on his console, and three files filled in at the bottom of the computer console. Mickey opened the first. “I see a strong iron line. Oh, that one's got to be nickel. No sodium, good. No other heavies. Don't get your hopes up, let me look at the others.”
The second and third confirmed the first one. They had uncovered a nickel-iron asteroid a mere seven million km away.
Harel was not amused when Standish informed him that the hootch wasn't coming his way until after they tested the body out.
***
“As far as I can tell, it's exactly what we want, at least chemically,” said Duane, who was also a fairly good jackleg chemist. He had created the reference spectrograms that all of the observing teams used. “It's a nice high percentage of nickel-iron, but I can't tell you the size worth a damn.”
“Yeah. But we can infer it from the reflected light, can't we?” asked Standish. “Didn't that spectrogram give you an idea of what else was in there? It's not a pure cylinder of shiny metal out there.”
“The things we want—iron and nickel—are there, but there's also some silicon, oxygen, and aluminum in there, too. It's safe to say that we're looking at a hunk of metal with some stony debris on it. That's about all I can tell you from here.”
“We should have ordered up a telescope from McCrary,” groused Standish. “Benjamin, how's its orbit?”
“I'm starting to wonder when the joker shows up. We're slowly converging—Eighty-two here and our targets are going to draw closer to each other over the next ten months before they start moving away from each other. Closest approach, five million km, give or take. Practically kissing.”
Dead Men Flying Page 10
