Guardians of the Galactic Sentinel 1: The Deimos Artifact by Phillip Nolte Page B

which is impossible, by the way -- it would take you about eight minutes to cover that distance. At just under 0.2 c, you need five times as long to cover the same distance. That's around forty minutes."
    "That makes sense," said Zack.
    "Most inhabited star systems have a diameter between 60 and 90 AU which means the transition time to cross an entire system is something between 40 and 60 hours on sublight drive. What's more important to us is the distance between the inhabited planets and the hyperjump zones. That averages somewhere between 20 and 30 AU which makes the travel time somewhere around twelve to twenty-four hours, depending on the system you're in. Throw in a couple of hours on the reaction drives at either end because you can't go into sublight when you're close to a gravity well, and we're talking the better part of a day to a day and a half to reach the hyperzone from the inhabited regions of most systems."
    By now Zack's head was reeling, but he plunged on with one more question, "Why can't we just use the reaction drives?"
    "Good question," she replied. Apparently it was good enough that she had to think about her answer for a few moments. Finally she said, "Even though the best reaction drives can deliver about 5 G of acceleration, way more than enough to get you up to the speeds necessary for interplanetary travel, it still takes weeks to reach 0.2 c. Not only that, the amount of reaction mass you'd need is...beyond comprehension. Once you've accumulated all that velocity, you need an equal amount of time and reaction mass to slow yourself back down if you're going to accomplish anything at the other end of your journey.
    By the way, because of these same limitations, we have to be really careful to limit how much velocity we generate with our own reaction drives or we won't have enough reaction mass remaining at the other end to speed up or slow down enough to match velocities with our destination."
    "I see why Cliff wanted to top off the reaction fluid!" said Zack.
    "You can never have too much reaction mass," said Beth.
    "So the sublight drive gives you the speed without the reaction mass penalty?"
    "That's absolutely right, Zack. Again, don't ask me how it works, but we come out of sublight at the same relative velocity we had when we went in."
    "That's enough for today," said Zack, shaking his head as if to clear it, "Thanks for making the attempt."
    "No problem," said Beth, returning to her instruments. Over the next several minutes she made a few minor adjustments to her control board before calling down to engineering. "Engineering?"
    "Yes, Ma'am?"
    "Is everything ready down there for sublight transition?"
    "Everythin's go, Cap'n"
    Beth flipped up a red cover protecting a large red toggle on her control console, "Switching to sublight in three...two...one...now!" At the end of the countdown, she flipped the big red switch.
    Zack felt a gentle flip-flop in his stomach but little else as the ship made the transition to sublight space. He could feel a barely detectable thrumming vibration in the ship that hadn’t been there before and he could hear a subtle hiss that seemed to come from the outside of the ship.
    Beth was busy at her console for the next five minutes or so and Zack watched her without speaking. Finally, she pressed a large button on her console. Afterwards, she arched her back and rolled her head to work out some of the cramps from all the sitting she'd been doing.
    "The next several hours should be pretty quiet," she said, swiveling her chair to face him. "If I'm smart, I'll get some rest before we get to the jump zone." She caught Zack's eye, "I'd feel a lot more comfortable if you kept an eye on the bridge while I try to get some sleep, Zack."
    "But...I haven't a clue what to do."
    "It's okay. Just sit over here in the pilot's chair and if you see any red lights or hear any alarms go off, come and grab me. I'll be in my quarters."
    "I guess I can do that."
    "Good. Later then?" Beth