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Old 08-17-2018, 10:19 PM   #1
Varyon
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Default Working out some Superscience Space Drives

So, I've been working on the star systems and "aliens" of my space opera setting, and I'm currently taking a look at the superscience spaceship drives. I already know how I want them to behave in combat - they roughly function like WWII fighters (for the fighters, obviously) or naval vessels (for the capital ships), to the extent of even having roughly comparable accelerations and top speeds. When not locked in combat, however, they need to travel faster - a lot faster. I want to scale things so that, theoretically, a capital ship with 3 drives would take 1 month to go from the center of the system (ignoring the fact there's a freaking star there, hence the "theoretically" bit) to the helioshock (termination shock, where the solar winds slows down to subsonic speeds), as the helioshock is where they can transition to hyperspace. I also want the drives to function as pseudovelocity boost drives. That's all fine and good... except it means such a ship needs to average around 3 AU per day (the helioshock is 90 AU from the star). That gets them from the setting's Earth-equivalent to the system's primary asteroid belt in well under a day, when I'd rather prefer such a journey take around a week.

A completely nonsensical - but easy to implement - solution is to set some arbitrary cutoff point (say, the snow line at 5.1 AU). Closer to the star than said cutoff point, speed is drastically reduced, to something like 0.3 AU/day or so. Beyond said cutoff point, you see a marked boost, allowing you to get to the helioshock within the requisite month - in the case of the 5.1 AU cutoff and the 0.3 AU/day speed within it, you need something like 6.6 AU/day beyond the cutoff line to make the one-month deadline.

A bit better solution, at least in my mind, is to have the boost drives slow down as you get closer to the star, with the easiest to implement being a linear progression - calculating speed (in AU/day) is a function of distance (in AU) - x - that looks something like f(x)=0.06x+0.15. This is more difficult to implement, but when simply traveling from one orbit to another, isn't too terrible. The problem, of course, is that you don't always want to wait until the point when your destination is (after accounting for travel time) a straight line away from the star, so actual travel times and routes are going to be rather complicated.

An idea to make that last option work is to allow vessels to travel along a planet's orbit around the star at an incredible rate, such that you'd basically travel like that at the start or end of the trip until you reach the point you want, and just go in a straight line away from/toward the star otherwise. I'm thinking maybe 10x the normal speed (I was actually considering higher, but then ships with more than 3 engines might be able to go faster than light by my equation, and I'd rather avoid that outside of hyperspace).

However, what unforeseen consequences might such a scheme have? At 10x speed, you can do a full circuit of your current orbit in a bit over 3 days (EDIT: This is looking at the orbit at 1.11 AU, the further away you get the longer a full circuit takes). Does this prevent any particular type of adventure type... or cause any others? Should I limit this to be within a planet's (or asteroid belt's) orbit around its sun - so with my aetheric stars, you'd only be able to get the speed boost at 0.25, 0.41, 0.67, 1.11, 1.84, 3, 5, 8.25, 13.6, 22.45, and 37 AU? Note this would let me go to something like 30x normal speed (full circuit in a little over a day) without breaking the light barrier.
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Last edited by Varyon; 08-17-2018 at 10:34 PM.
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Old 08-17-2018, 11:07 PM   #2
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Default Re: Working out some Superscience Space Drives

Would using the rubber sheet description of gravity help?
The deeper into a gravity well you get the more efficient a drive is (fairly standard so far). The difference is due to technobabble there is a super efficient path that follows contour lines of the same depth around a gravity well. Which may or may not be only accessible from the smaller gravity well of an orbiting body.
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Old 08-18-2018, 12:39 AM   #3
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Default Re: Working out some Superscience Space Drives

You might also want to go with a tidal-force-limited boost drive, on the principle that tidal forces are unique to actual gravity and completely absent from the likes of spin gravity and acceleration gravity. Where gravity falls off with the inverse square of distance, today forces fall off much more quickly, with the inverse cube of distance. Since Jupiter has about a thousand Earth-Masses and Sol has about a thousand Jupiter Masses, their respective today force ranges will be ten and a hundred times Earth's today force range: that is, you'll feel the same tidal forces roughly ten times as far from Jupiter or a hundred times as far from Sol as the distance from Earth that you'd experience the same tidal forces. Conversely, an object with a millionth of Earth's mass produces comparable tidal forces at a hundredth of the distance; so even starships are likely to produce significant tidal forces.

The nature of the limit could be a matter of speed (the more tidal forces there are, the less of a boost you get), or it could be an engineering issue (the amount of tidal forces the boost drive's systems can cope with depends on how well they're engineered, resulting in boost drives being rated for how close they can get to large masses and still operate).
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Old 08-18-2018, 06:43 AM   #4
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Default Re: Working out some Superscience Space Drives

I actually already have the explanation for the drives. They interact with hyperspace, and the systems humans have colonized have a solar wind that also has a complicated interaction with hyperspace (the stars are called "aetheric stars" due to their interaction with the hyperspatial medium, which is called aether). Within such solar wind, the drives are able to function in a pseudovelocity boost mode (outside of it, they are just reaction drives with unrealistically-high delta-v's). However, while boost drives are taking advantage of this interaction, the denser the solar wind (that is, the closer you are to the star), the more the high concentration of particles interferes with the operation of the drive (indeed, in atmosphere they are unable to function in boost mode). As an aside, the solar wind loses much of its aetheric quality when it passes the helioshock, so boost drives are much slower between that and the heliopause.

The ability to move around the star at a higher velocity has shakier reasoning, but gets better if we indeed do restrict it to the bands where the planets are. This isn't because the planets are carving out a channel - it actually works the other way around, in that such bands are naturally occurring channels where you can get into orbit quite readily, and the planets (and asteroid belts) formed there due to such interactions (all matter has some weak interaction with hyperspace). This also explains why every single aetheric star has the same orbital bands. Seeing as each band is located 1.65x the distance from the orbit of the next closest band, this means you could have a final spaceship-only orbit at 61.15 AU.

What I'm really looking for in this thread is if the superfast orbits would cause adventuring problems I'm not currently seeing - or even adventure seeds.
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Old 08-18-2018, 11:18 AM   #5
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Default Re: Working out some Superscience Space Drives

An example of a potential issue is piracy, which I want to have (two notable factions in the setting - the "alien" malakim and the human Caliphate - make heavy use of it, and of course there are independent pirates as well). A ship in boost doesn't have very good sensors, but is itself easily detectable. Additionally, it's very easy to interdict a boosting ship, provided you can get close enough, forcing it (and your own ships) to go much slower (each drive on a capital ship gives it Move 1/10, each drive on a fighter gives it Move 10/50 - and yes, those are in yards/second). Allowing the increased lateral movement anywhere would make it very difficult to intercept a ship traveling away from the sun (as they can boost to the side faster than you can), but very easy to intercept one traveling toward the sun. It would also make it much easier to patrol a system against piracy, however, as each patrolling vessel can exploit the increased lateral movement to cover a much wider swath of space.

This is actually why I thought up restricting lateral movement to only when within one of the star's stable orbits (the ones that can have planets; is there a better term for this?). In this way, patrols would mostly be restricted to such orbits, boosting outward when there's a sign of trouble but probably not being able to respond in time. The pirates could also hang out in such orbits, disguising themselves in some way (I'm thinking the asteroid belts are very popular for pirates), lateral boosting (I should probably come up with a better phrase for this, it's something the Harpyians are going to have an easy phrase for) to a good point for an intercept course when they see a juicy target and before any local patrols catch on, then making a mad (but slower) dash outward to actually intercept the vessel. The vessel, meanwhile, if it manages to detect the incoming ship(s), will need to determine if it's better off trying to turn around and get back into an orbit it can use for lateral boosting to escape, trying to outmaneuver and bypass or even fight off the pirates, or simply surrendering some of its cargo in exchange for passage.
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Old 08-18-2018, 03:24 PM   #6
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Default Re: Working out some Superscience Space Drives

0.3 AU per day is fast, over 300 miles per second, so it does not majorly inconvenience a society unless the hyperspace shadow is much further than 5.1 AU. Anything moving that fast is impossible to target with any ballistic attack unless it also possesses a boost drive, as the target is just moving too fast, meaning that your attacks are beam weapons or boost equipped missiles.
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Old 08-18-2018, 07:36 PM   #7
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Default Re: Working out some Superscience Space Drives

Quote:
Originally Posted by AlexanderHowl View Post
0.3 AU per day is fast, over 300 miles per second, so it does not majorly inconvenience a society unless the hyperspace shadow is much further than 5.1 AU.
As noted in the original post, the point at which one can transition to (and from, although I don't think I explicitly stated that) is the helioshock, which is 90 AU from the star. That is, of course, quite a good deal further than 5.1 AU out (5.1 AU was the arbitrary point chosen to change over in the two-speed system, but I'd rather prefer a system where speed increases constantly the further you get from the star).

Quote:
Originally Posted by AlexanderHowl View Post
Anything moving that fast is impossible to target with any ballistic attack unless it also possesses a boost drive, as the target is just moving too fast, meaning that your attacks are beam weapons or boost equipped missiles.
Combat in the Harpyia setting is primarily with superscience blasters (a bit more akin to plasma weapons than particle accelerators), which have slow projectiles with short ranges (at least for space). Combat is not done at the boost drive speeds, in no small part because having boost drives that aren't explicitly cooperating with each other within a certain range interdicts the boost aspect, slowing things down to much slower speeds (the K-N drives used by capital ships get performance roughly comparable to WWII-era battleships, while the aether drives used by fighters get performance roughly comparable to WWII-era airplanes). Think of it as fast-moving counters on a very large map, and when two counters meet, things zoom in for some dogfighting.
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Old 08-18-2018, 08:08 PM   #8
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Default Re: Working out some Superscience Space Drives

A calculation for speed of the square root of distance from star in AU and ten divided by 3 might give you the speed range you want.

That would go from .33 AU/day at 1 AU gradually increasing as you go out. I'm getting 6 days to about 3 AU.

You'd be going at about 3.16 AU per day at 90 AU.

I'd fid the system a little too complex to work with really but it might be the speed ranges you want.
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Old 08-19-2018, 06:53 AM   #9
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Default Re: Working out some Superscience Space Drives

Quote:
Originally Posted by Fred Brackin View Post
A calculation for speed of the square root of distance from star in AU and ten divided by 3 might give you the speed range you want.

That would go from .33 AU/day at 1 AU gradually increasing as you go out. I'm getting 6 days to about 3 AU.

You'd be going at about 3.16 AU per day at 90 AU.

I'd fid the system a little too complex to work with really but it might be the speed ranges you want.
A square root - or even quadratic - relationship might be more sensible given the technobabble of how it works, but a linear equation is much easier to work with, particularly if the lateral boost option means the fastest way to travel is going directly toward or directly away from the sun. This basically means you would calculate the speed of the halfway point of the trip, and use that as the average velocity to determine actual travel time.

Honestly, if I go with the "orbital highways" lateral boost option, it might not be horrible to just give the areas between each orbit a constant velocity, albeit a different one for each void (getting faster as you get further from the star). This would replace the calculation with a table lookup.
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