Frozen Orbit

by Patrick Chiles

  SURGE IN ELECTRICAL JUNCTION 6B. PRIMARY AND SECONDARY REGULATOR MODULES AFFECTED.

  And that didn’t trigger an automatic shutdown? And how’d he miss the surge in the electrical bus? Must have been lost in the noise when he brought Daisy out of hibernation. This was why they’d always had a room full of engineers back in Houston watching every move: Some things happened too fast for a busy astronaut to notice until he was dead. It was a great concept until you were a solid light-hour from home.

  He stabbed at the on-screen menu, diving deeper into the propulsion system. There it was, in the trace file: The electrical bus was protected by the same shielding that prevented Jupiter’s radiation belt from frying them in their seats. They couldn’t manage that same level of protection around the drive, though. The engine bells by nature had to be out in the open. The control software must have compensated by rolling back to the next highest power setting.

  Could the same thing happen to the others?

  QUERY: Source of 6B surge.

  SOURCE UNVERIFIED. SIGNIFICANT PROBABILITY OF INTERACTION WITH JOVIAN MAGNETIC FIELD. CONTROL SOFTWARE COMMANDED P74 SAFETY PROTOCOL.

  As suspected, a “Program 74” fail-safe. He never knew if their control logic had any solid theory behind it or if they were just stuck in the “if this, then that” thinking from the Apollo and Shuttle days. Either way, Magellan’s current orientation presented engine three’s side of the spacecraft toward the brunt of Jupiter’s magnetic field and the high-energy particles it bombarded them with. Engine three had taken one for the team.

  “Jack?” Roy again, looking for answers. His entire exchange with the AI had taken maybe ten seconds, an interminable interlude in spaceflight. One more look at the timing . . .

  The injector/compressor stage was off by a good 0.3 hertz now. Jack grimaced, dreading what had to come next. “We stay in cruise mode or shut down engine three.” Either way they lost an awful lot of thrust.

  For her part, Noelle had wasted no time transitioning into her contingency role, a typically anodyne label for what was their emergency-action manager. She stabbed at a selector which switched her monitors over to the emergency checklists. As the screens flashed over to an attention-getting series of crimson menus, she prepared to talk them through contingencies just as Mission Control would have if they weren’t over a full light-hour away. Now that her flight station was configured, she grabbed an old-fashioned binder of mission rules from a cubby beside it and tore the book open to a tab labeled “Jupiter Gravity Assist.” Most of their options were pages trimmed with red hash marks: Mission-abort scenarios.

  “Engine shutdown,” she recited with practiced calm, one eye on the event clock above her console. This wasn’t going to be like turning an airplane, or even following the free return trajectories that lunar expeditions had been bound to. Any changes to their direction and accumulated velocity, even if measured in seconds, held considerable consequences: It would determine whether they remained at Jupiter, headed back to Earth, or were flung farther out into the solar system.

  IF BEFORE incremental ΔV 20,000 m/s . . . she scrolled down through all of the secondary considerations for the bottom line: “abort to orbit,” meaning they’d shut down the good engine to achieve orbit and execute the “Extended Jupiter Mission Scenario.” It was too late for that, even if she’d secretly hoped for it.

  IF AFTER incremental Δ V 20,000 m/s . . . abort to Earth, which at this velocity would keep them out here almost as long as if going to Pluto. But it also had the added effect of looping them around the other side of the Sun to fly by Saturn before bending their orbit back Earthward. Not a terrible deal.

  “Noelle?” Roy asked sharply. He’d almost said “Bubba.”

  “Stand by,” she snapped, then: “Sorry, love.”

  “Been with you too long for hard feelings,” he said, “but we’ve gotta decide what to do right quick.”

  She flipped back to the first page. Were there any options that didn’t involve giving up? How many times had they simmed this exact scenario? “Jack,” she asked, “how long can we run the other engines at maximum rated thrust?” An understated way of asking for emergency power.

  “How long you need?”

  She tugged at her lip as she studied the possibilities. Trajectory planning was not her specialty and this was too critical for the rules of thumb she’d relied on to get through astronaut training. “Traci?”

  The pilot was way ahead of her. “Looking at it.” She and Roy hadn’t even considered aborting, not even for the chance to see Saturn up close. They were all bound by the same irresistible, if unacknowledged, impulse to make it to the end of the mystery that had been dropped on them right before launch. “Call it two minutes at max power. Jack, back me up on our state vector.”

  “We can do that. What time stamp are you using?” he shot back.

  “Shutdown, so T-plus eighty. Solar reference frame, J2000,” she said, somewhat unnecessarily. They all knew which reference decade to use out of the Astronautical Almanac, but couldn’t afford to screw this up. While they were leveraging Jupiter’s mass to add velocity, more important was the direction change it would give them for free. Their final destination lay below the ecliptic, that invisible flat plane all the major planets inhabit within a few degrees of each other. Besides its extreme distance, being inclined seventeen degrees to the solar system’s equator made Pluto that much harder to reach. Plane changes were expensive in terms of reaction mass, so using Jupiter’s gravity as a free booster to match orbits with Pluto demanded that they get this right.

  They had about three minutes to find out.

  Jack scribbled furiously on a tablet and compared his own estimates to the computer’s. The trick to an Oberth maneuver wasn’t in stealing some of the planet’s velocity so much as it was taking advantage of the potential energy its gravity imparted on their exhaust mass. The closer they got, the stronger the gravity and the larger the multiplier. At twenty thousand kilometers above its cloud tops Jupiter offered quite a multiplier, but it was as close as the flight planners had dared. “Okay, I got it . . . wait!” That couldn’t be right. Why didn’t the computer agree with him? “No, I don’t.”

  “What’s wrong?” Roy shot back. Their numbers had to agree, and soon, or it would be a long orbit back to Earth.

  “Try these,” Jack said, throwing his velocity and position figures up on their displays. “I forgot to correct for the date. It’s not 2000.”

  “Hasn’t been for a while now.” Did Roy actually sound amused?

  A quick beat, then: “Okay, I concur,” Traci said, eyeing their velocity against a plot of their choices. “It puts us near the edge of the curve, but it works.”

  “Mine too,” Roy chipped in. He took a breath. “And what’s the computer say?”

  “Guidance platform agrees with all three,” Noelle said as she went back down the mission rules’ decision tree. They were playing this one close. “Now what, love?”

  “Much as I’d enjoy a jaunt by Saturn, we’ve got some unfinished business ahead. Agreed?”

  “Agreed,” Jack and Traci said more or less in harmony. Noelle held up a finger to cool their heels as she flipped to the “Pluto Orbit Insertion” tab. She wasn’t sending them anywhere without first making absolutely certain that there was a plan for getting back home with one engine out. Which there was, she just needed to see it again in something other than a simulated emergency.

  “Agreed,” Noelle sighed, satisfied that they had in fact worked out a way to get home with a third of their drive system cooked.

  “Two minutes,” Noelle announced. There was another curse from up front as Roy punched up a different display, this one a maze of ellipses and parabolas. He was scrolling through different scenarios for an orbit back to Earth. One open-ended hyperbola remained, a lower-energy trajectory on to Pluto. Jack called up the same display and shot a glance toward Noelle, who had done the same. “You thinking what I’m thinking?”

 
“Aller de la fièvre.”

  Jack smiled inwardly despite the tension. “Go fever” sounded so much nicer in French. “That’s over a year.”

  “Not if we can lower our periapsis and pick up more delta-v.”

  “And more friction drag, too,” he reminded her. “The tradeoff isn’t worth it.”

  “I wouldn’t be so sure. Our trajectory is based on the atmospheric models we had at the time, no?”

  “No . . . I mean, yes. Yes. So what?”

  The gleam in her eyes said it all. “That was two years ago. We have much better data now.” She swept a hand across one of her screens, which then duplicated itself on Roy and Traci’s display. “We can lower our periapsis by at least ten thousand kilometers.”

  “What?” Jack sputtered. “Your data can’t be that good.”

  “I believe it is,” she said with a nod toward their screens. “The LIDAR returns are quite encouraging. Pressure and density values in the troposphere are significantly lower than the models predicted for the Southern Temperate Zone.”

  “And the stratosphere?” If density and pressure were bottoming out at lower than expected altitudes, they could be looking at atmospheric effects similar to a frigid day on Earth. Granted, it was on an absurdly exaggerated scale since Jupiter was just about all atmosphere.

  “As I said, we can safely tighten our radius by a good ten thousand kilometers.”

  Traci had been projecting a new path while Noelle and Jack argued over planetary atmospherics. “That’ll let us pick up some lost delta-v, but not all of it. We’re still adding weeks to the trip. How far can we stretch our consumables?”

  Jack held up a finger to stall them while typing commands into the tiny keyboard with his free hand: QUERY: Minimum crew caloric requirements—assume 120 day mission extension. That should be simple enough for Daisy to find. There was a calculation matrix for it somewhere in their mission plans. “Water, yes. The reclamation plant’s efficient enough to keep us going for years. I’m worried about food.”

  “One minute,” Noelle warned.

  minimum caloric requirements can be met with existing rations. optimal if the experimental hydroponic garden is utilized. Daisy presented another option relying on the two medical trauma pods down in sickbay, something Jack wasn’t ready to offer just yet. Going into hibernation to stretch their food supply could wait.

  “We can do this. Who here has a green thumb?”

  “The hydroponic module?” Roy asked. “I’ll leave that part to my better half.”

  “It’s mostly edibles,” Noelle said. “A few herbs for variety, but we can replace those with soybeans and peanuts for our protein intake.”

  In a display of strength not just against gravity but of will, Roy turned in his seat to stare down his wife. “Babe, I need your no-BS read on this. Can you make that garden grow? Because what has to come next won’t be fun.”

  Noelle checked the countdown clock: thirty seconds. She looked up to meet his gaze. “Yes. Let’s go to Pluto.”

  Magellan’s present position in space had been worked out to exhaustion months before and was based on a certain number of weeks of constant acceleration at a certain value of g along a painstakingly crafted set of vectors. And that was all about to be literally turned on its head.

  In order to lower their altitude above Jupiter for maximum advantage from its mass, they would have to undo some of that vector. Unlike flying an airplane, they couldn’t just push the nose over a few degrees and level off. They had to lower their orbit by losing enough velocity for the planet’s gravity to strengthen its grip, and the only way to do that was to flip Magellan tail-first and burn against their direction of travel long enough to cancel some of that momentum. Done right, they’d still end up gaining more velocity on the other side than they would have otherwise.

  If done wrong? No one had time to bother with that.

  Roy and Traci had responded to Noelle’s assent with a flurry of movement as they reconfigured the guidance platform. “Give me a target,” Roy barked. He had very little time to get all hundred-plus meters of spacecraft turned around and had to know where the nose needed to end up.

  “Coming up,” Traci said with a look over her shoulder at Jack, who by now had stopped caring what Roy thought of his reliance on their AI. They weren’t going to figure this out on their own and Houston wouldn’t know until it was too late. “You got a vector for me?”

  A glowing crosshairs icon superimposed itself on the pilot’s eight ball nav director just as the hard numbers lit up on the multifunction display between them. “There’s your target,” Jack said, confirming it with the AI as he hurried through a series of automated cues for securing the plasma generators and isolating their powerful capacitors from the electrical bus. “Reactors and field generators are back in standby. You’re go for shutdown.”

  “Shutdown,” Roy ordered, and Traci smartly chopped the throttle levers. The weak gravity disappeared as thrust fell to zero, followed by a slight roll starboard as the guidance flywheels compensated for the off-axis forces. The neon-green target hovering in the eight ball shifted with it as Roy carefully wrapped his meaty hands around the controls. “Going manual.”

  With the storm shutters still buttoned up, the only sensation that they were turning around was the disorienting motion of Roy pirouetting Magellan about its pitch axis fifty meters behind them. Gravity returned in the opposite direction, “eyeballs out,” as the big ship swapped ends like a centrifuge.

  Jack marveled at how someone with such ham hocks at the ends of his arms could fly with such finesse. He followed the pilot’s actions with intent, his eyes darting between their master display and the AI’s continuing scrutiny of it on his personal screen. “Talk to me, Daisy,” he whispered, ready to intervene if things took a turn for the disastrous but with no idea how he might go about it: Jump from his seat and tackle Roy? Override and shut down his flight station? Beg “pretty please?”

  overcorrecting, Daisy reported on-screen. pitch exceedence imminent.

  The words caught in Jack’s throat just as he felt a cool hand grip his own. He looked over to find Noelle silently urging him to relax. She nodded at his armrest monitor, where Daisy kept its running commentary, then gave him a quick shake of her head. Trust him.

  There was a sharp change in g-forces. Jack exhaled and looked back at his screen just as he felt the familiar stomach lurch from the sudden absence of gravity.

  pitch rate within tolerance. intercept next maneuver node at relative y=0.00, x=0.00, z=0.00.

  Whoa. Jack whistled. Roy had just hit all balls while hand-flying a hundred-meter-long spacecraft at over half a million kilometers an hour. Noelle loosened her grip and gave him a playful swat.

  “Told you,” she said confidently, as her face went slack with relief.

  Owen’s phone started going crazy just as he was pulling off of NASA Road 1 and into Johnson Space Center, the leftover glow from a peaceful night home with his family evaporating with the morning mist.

  It was exasperating how many people were still dependent on text messages. If it’s that important, then call me—it’s that little telephone icon next to my name in your contacts folder. Today, it was probably best that he had time to digest the mission management team’s frantic texts instead of a panicked voice over the phone because what he was reading sounded absolutely nuts.

  Owen resisted the urge to storm into the FCR demanding to know just what those rocket jockeys thought they were doing up there, instead calmly striding up to his desk behind the flight director. A simple arched eyebrow did the rest. Flight motioned for his assistant to take over and waved Owen into the privacy of the observer’s gallery.

  “They lost one of the mains just after starting the PC-3 burn. Looks like some transients crossing the southern magnetosheath chuffed number three and the control logic couldn’t keep up. When the guidance package saw that, it commanded a rollback to idle.”

  Owen looked past him toward the big wall
screens at the far end of the room. “Doesn’t look like they’re sticking with the script, does it?”

  Flight didn’t know whether to laugh or swear like the sailor he’d once been. “They’re improvising. Improvised. Whatever they’re doing, it’s too late for us to intervene. But Roy just turned the ship around and started a braking burn.”

  “No statement of intent? He just did it?”

  “They had some help from Daisy.”

  Owen did a double take. Knowing Roy, things must have gotten pretty heated up there. “So what’s your call from here?”

  “Remaining engines burned full power at retrograde. That lowered their periapsis to the bottom of the error band.”

  Setting themselves up to snag a not-inconsequential amount of delta-v in the process, Owen realized, if they didn’t snag atmosphere at the same time. “So they’re letting Jupiter make up for the lost engine. Will that be enough?”

  “It’ll get them through Phase Two, but it may not be enough to keep on schedule. The FIDO and NAV backrooms are trying to figure out what this all looks like a year from now. Judging by Daisy’s search crosstabs, they’re counting on supplementing their diets from the hydroponic garden.”

  Owen could only shake his head, recalling some of Rhyzov’s stories from the old days in Russia. What was it about being that far out that turned normally cautious astros into insane risk-takers?

  After two minutes, just as planned, Magellan’s remaining engines finished their high-thrust burn at the precise moment the curve of their trajectory had bent to match the predictions on screen. The plots flashed through changes as the guidance computers caught up to their new reality. Just as predicted, fresh curves reappeared along with a flood of new parameters on what they’d already started calling the “scenic route.”

  “So there’s one down,” Roy said. “Stand by, I’m going to rotate us back to prograde.” Immediately they felt the ship start pitching back around nose-first.