Aurelius Posted December 8, 2013 Share Posted December 8, 2013 ((OOC Note: Although the first two posts in this fiction are technically discussing the time between the two fictions, Ice Giants officially picks up one year, ten months, and seven days after Cold Jupiter left off.)) ,, My flight from Tyche to the outermost edges of the solar system (as measured by Neptune’s orbit) winds up taking me only 5.8102 x 107 seconds, which OK, yes, that’s a long time, but I think anyone would agree that it’s a significant improvement over 7.0186 x 107 seconds. More than four month’s worth of improvement, in point of fact. Needless to say, my average acceleration has gotten better during my travels. ,, By the time I reach the last few hundred thousand kilometers of the roughly fifteen thousand astronomical units I must cross in order to reach my destination, my average acceleration over the entire length of the journey has reached a whopping 2.651 m/s2, which is only around 27% of one standard gravity. This is still only my average acceleration, however. My actual acceleration by this point is 17.6667 m/s2, which is pretty nearly two full g’s of thrust. There are two reasons for the discrepancy between my actual and my average acceleration. ,, The first reason is that, aside from a few semi-fantastical exceptions that are still not out of the “really neat idea” phase, let alone the design phase, there are no propellants or engines in existence that can maintain constant acceleration, over a scale of years, larger than a very small fraction of a meter per second squared. My own ability to propel myself through space is no exception. At “full burn”, I can maintain constant acceleration for approximately sixty-six hundred seconds at a time before I’m “all out of juice”, so to speak; if I take it easy and go at half-strength or less, the span of time over which I can maintain constant acceleration increases in inverse proportion. ,, Usually I just go full-burn until I’m all worn out, though, because something I’ve gotten even better at than generating thrust or listening for radio signals is regenerating my power levels (or battery charge or whatever it is that keeps us novas going). It generally takes me less than fifteen thousand seconds to regenerate fully, so I can typically manage slightly more than four full-burn sessions per twenty-four hour period. The actual percentage works out to pretty nearly 30% of every day that I can spend at full-burn, which in turn works out to roughly 30% of each week or month or year. And 30% of 17.6667 m/s2 is 5.3001 m/s2, which in turn is my maximum average acceleration. ,, I’m sure it’s readily apparent to anyone, but this is exactly twice the acceleration I quoted above as being my overall average, which brings me to the second reason for the discrepancy between that number and my actual acceleration. I know I’ve covered this before, but it’s worth going over again: in space, once an object is in motion it will remain that way until acted upon by an outside force. What this means in practical terms for me is that, unless I want to crash into another moon while traveling at several kilometers a second (or actually, a whole hell of a lot faster than that, given how long I would’ve been accelerating by this point), I have to start DE-celerating at about the halfway point of my journey. In essence, I must spend the first half of my journey building up speed and the second half shedding it all. The net result, from a mathematical perspective, is that my effective average acceleration over the entirety of my journey can be no faster than one-half of my maximum average acceleration. And one-half of 5.3001 m/s2 is 2.651 m/s2. ,, And there you go: basic astrodynamics. Bet you feel smarter already. ,, Something that really confuses me for a kind a long while is that my trip seems to be taking even less time than it should, even if I account for the steady increase in my average acceleration. The difference isn’t huge – especially not at first – but the discrepancy gets worse over time until I just can’t ignore it. After a while, though, I figure it out: time dilation. ,, By the time I reach the midpoint of my journey and have to turn it around and start shedding speed I’m travelling at fully seventy-six thousand, nine hundred and eighty-seven kilometers per second (that’s just shy of seventy-seven kilometers for every one-thousandth of a second, for those keeping score). A different way to say it is that I’m moving at exactly 25.68% of the speed of light. Of course, my average speed over the entire trip works out to only 12.84% of light speed, but that’s still really fast. Fast enough, in fact, for relativistic time dilation to begin to matter. ,, Overall, the net effect of the relativistic time dilation between my own frame of reference and any stationary observer is about 0.008 seconds per second. That probably doesn’t seem like much, but it starts to add up after fifty-eight million seconds. As a result, to me the entire trip winds up seeming as though it’s taken 5.762 x 107 seconds, rather than the 5.8102 x 107 seconds that it seems like it should have (and that it did take, from the frame of reference of any hypothetical earth-bound observer who might’ve been watching me during my travels). Again, the difference isn’t large, but it’s still strange to think that I’ve effectively moved more than five whole days into the rest of the human race’s future. Link to comment Share on other sites More sharing options...
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