When the chime went off for the third time, Rifka realized that she was blowing through her scheduled time to go for her run.

  “Off!” She told the chime. She rolled her shoulders to try to relax. “I’ll get to you later.” She told the computer. Her stomach felt irritated. “That’s what a I get for breaking the schedule.”

  She coded the auto-tracking program to record and locate the new vessel, and hopped out of her chair.

  “Right! Time for a run.”

  From when Rifka was small, the scientists insisted that Rifka exercise. But, LM-25 allowed her to do more than resistance training. She could run all over, instead of a just a treadmill. Even with the flickering unsteady lights in the old mine tunnels, she never took running off her daily schedule.

  She returned to her wardrobe to change into her running gear. Rifka’s running suit had the same auto-fit feature as the pressurized coverall, but it didn’t have the reinforced plates. It also came with its own high impact form-fit helmet with digital display and microprocessor. It wouldn’t do to get caught away from an air supply and pressure suit if something bad happened.

  LM-25 may have had welded steel girders and rocky carved walls, but it wasn’t Earth. A vacuum had no sympathy. Most of the station had been buried less than 10 meters from the surface, and who knew exactly how close some of the mine shafts came to venting air. The Company that built it seemed fairly careless with worker safety.

  After getting outfitted, Rifka pulled up her tunnel explorer map onto the helmets display. Laying out a course, she set off through the machine-cut mining tunnels.

  She started her run the usual way, a three minute light jog to warm up, before she started the difficult part. Flash Sprints. As she leaned around the tunnel’s corners, picking up speed, she set the map to record distance and speed.

  Rifka felt for the bio-liminal engine next to her heart. She would describe it as a warm spot under her right breast. Like squeezing a muscle, Rifka used it for a flash-sprint. She hopped into the air, and the bubble formed just beyond her body. For a moment the flickering light held steady as time outside her body creased to exist. Rifka’s flash-sprint landed her six meters further down the tunnel.

  The liminal engine had been one of humankind’s great achievements. But, perhaps even a greater achievement was the bio-liminal engine, which allowed Rifka and other bioengineered humans to create their own liminal reality bubbles. With the bio-liminal engine—and when she wore the a sealed suit like her running suit—Rifka became a small space-traversing vehicle all by herself.

  To the outside perspective, Rifka left one spot and then arrived at the second spot in an instant. To Rifka, she floated between the two points over the course of two heartbeats, the bubble moving her through the space without her physically having any momentum at all.

  After she landed, Rifka laughed. “I love flying.”

  Rifka knew that it wasn’t flying, exactly, but she moved from one place to the next without touching the ground. So, Rifka reasoned, a flash sprint was as nearly as good as flying.

  Rifka considered her longest recorded flash-sprint to be 22.7 meters. The float had felt like 4 seconds. To the observer cameras, she appeared in both the starting point and the ending point so quickly, her image appeared in both places for .8 nanoseconds. It was all a part of a birthday gift to herself. That day, she tested her bio-liminal drive to exhaustion.

  This tale has been unlawfully lifted from Royal Road. If you spot it on Amazon, please report it.

  To conduct that test—deep in LM-25—Rifka found a long straight stretch of uninterrupted tunnel.

  She’d also tried flying in the normal sense, using the liminal engine to warp gravity and literally float, but actual flying took too much out of her. Even a six meter flash-jump raised her heart-rate up to 133 bpm, and made her crave another nutri-bar.

  Trying to fly resulted in blacking out. She could never sustain the engine for long enough to create the high velocity momentum to fly. Erasmus insisted that she spend the next day in bed. It completely disrupted her regimen. After, she decided that she would limit herself to practicing small jumps instead.

  Rifka didn’t know why distance would matter, but Erasmus guessed that moving that much space-time just took too much energy. Or, they guessed that her engine lacked efficiency. One of those two. The big space vessels moved a hundred lightyears in a blink of an eye. The passengers didn’t even sense time passing. Rifka reasoned that she misunderstood something about her engine. In the meantime, she would practice.

  The liminal engine had less strenuous uses.

  Rifka kept jogging, getting ready to use the liminal engine in a different way. Space-time also set the shape of gravity. So, as Rifka rounded the next corner, she started a wall run to change direction instead of just turning. Speeding up, she jumped up onto the wall and ran five steps completely at a right angle to the corridor’s floor.

  For normal humans, engineers had set the gravity in LM-15 using gravity plates. With gravity plates, they created “down” using a similar technology as the liminal drive. There was nothing wrong with zero-g, but humans evolved in gravity and they—and Rifka—found that working on your feet was better than letting physics take its course.

  Rifka, however, could shift that artificial gravity with her bio-liminal drive. Orienting down toward the soles of her shoes, she could do all sorts of acrobatics, provided she kept her reoriented gravity brief.

  Rifka finished her wall run and flipped off the wall.

  But, Rifka didn’t just practice with the bio-liminal drive. She also practiced her actual physical fitness. She landed into a proper physical sprint.

  The running suit had a biometric readout on the HUD. After her sprint, the helmet estimated she reached a brief nine meters/sec speed over her ten meter sprinting distance.

  This came at a cost; her heart rate leaped up to 156 BPM. She felt her heart pounding in her chest. The bio-liminal engine burned a little, but it felt stretched, not painfully broken.

  Relaxing, Rifka dropped into a normal sort of 5.7 meters/sec. She felt sweaty, but the running suit ramped its internal temperature controls and vented the excess heat using the micro temp-inverters built into its skin.

  “You’re doing a great job.” She encouraged the running suit. “We’ll take our time for a bit, and then do it again.” The suit didn’t have a verbal interface, so it didn’t say anything. Rifka felt sure that the suit felt encouraged.

  Fifteen minutes later, Rifka had returned to her living habitat, showered, and put her miners’ coveralls back on. Back on the schedule, she took ten minutes to eat her midday nutrient bar and drink a hydration solution. She checked her estimated calories, and decided that a second bar would probably be best. While she munched on it—the wrapper called it “crunchy” flavor—she reviewed her schedule.

  After 12:00, Rifka included three hours of virtual lecture saved in the station’s education suite—a statistics class combined with an introduction to ploy-probabilistic spacial mechanics. At 15:00, she had two hours of course reading for her classes, then half an hour to check her experiments, a 15-minute dinner, and then an hour of recreational biomech design work. She opened the schedule’s input window, and removed her recreational biomech design period.

  She replaced it with “track vessel.” She wanted to resolve the mystery of the new vessel and its strange arrival in the system. An hour would be enough, and then Rifka could get extra sleep in exchange for foolishly waking so early. After all, Rifka had almost all the data she would need to identify the ship.