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[Alternative FTL Drive] What to use for a hyper-limit?

Kilgs

SOC-14 1K
Baron
I’m trying to figure out an alternative drive for a hybrid game. It functions similar to a stutterwarp in that it requires a gravitational body to recharge in before jumping. But I’m getting stuck on an appropriate hyperlimit and wanted to know what folks thought could serve as acceptable limits. I’m not entirely stuck on the reality of it but just want an ability to look at a stellar mass/radius or planetary body mass/radius/g-rating to mathematically come up with the “limit.”

The technobabble is that it is a variant of the Alcubierre drive where it creates a gravity wave that the vessel ‘surfs’ at speeds greater than (c). The limits to the drive are that it creates a wave that, if it impacts another source of gravity, it mimics a bug on a windshield. So, when jumping into a system, the ship must disperse the wave a certain ‘limit’ or distance before reaching a stellar mass or planetary body.

The drive efficiency and range is based on the mass of the vessel. A smaller ship generates a wave that is smaller, less susceptible to detection, and can reach much greater speeds. A larger ship creates a wave that is much larger and slower but it sustains itself better and can reach greater distances. Technobabble explains this as a trade off between power use/wave creation/and the ability of the vessel to sustain itself within a wave. The wave creates a ‘wake’ that is projected front and back of vessel based on the size of the vessel/distance traveled. It is this forward wave that causes the risk to the vessel when approaching a stellar mass/solar system.

Speeds range from 0.03c per day to 0.6c per day. Range is from 1ly(for small vessels) to about 5.3ly(capital ships).
(I have all that math worked out)

I don’t want the drive to be very functional within a solar system. It can be used for jumps between extreme planetary bodies, provided they do not pass the star, but I prefer sublight within systems. But I can’t figure out, since bodies orbit at different rates, what would be a nice (passably explainable) hyperlimit.

Note that the drive is much more efficient fuel-wise than a J-drive or even the stutterwarp.

100Diameter makes the drive very efficient in-system. Too much so for my taste. I tried using a function of the diameter*surface gravity*distance traveled (as the larger vessel has a much greater sized wave, it would need to stop further out).

Are there any alternative measurements out there that can be easily computed from the stellar measurements or planetary measurements? The less complicated the better since I already have enough math floating around to make my liberal arts degree surrender in tears…

(As an FYI, the setting is built within Astrosynthesis, so I have the ability to plot orbital positions at any given time, mass, radius, gravity, etc. of all bodies).
 
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You're going to have a hard time using gravity as a measure that doesn't end up looking like the 100d rule. You'll have to make it some seriously fractional part of 1g - perhaps...
10^(-[some mass factor]*100)g
so, if your mass factor is 10, the result would be 10 to the negative 1,000th power, resulting in 0.0-999 more 0s-1g being where they have to shut down or go splat.

On a side note, have the drive lose its compensation when this happens, so the ship slams to a stop, but everything inside of it still has momentum. It won't take too long to hose down the forward bulkheads in a small vessel. In a really big ship you might need a few months to get rid of all the gooey spots.
 
Oh, have you incorporated relativistic effects? At .6c, there should be some serious issues with seeing the universe around you - which might include the ability to sense said limit. There might be your solution: you have to slow to <0.05c or something to sense the limit and stop your drive in time. Faster than light would be even worse, obviously.

(Hmmm, it appears you're using "c" as a distance unit instead of a velocity unit. Do you mean 0.6 light year when saying "0.6c per day"? That would take some calculating to know the actual speed.)
 
You're going to have a hard time using gravity as a measure that doesn't end up looking like the 100d rule. You'll have to make it some seriously fractional part of 1g - perhaps...
10^(-[some mass factor]*100)g
so, if your mass factor is 10, the result would be 10 to the negative 1,000th power, resulting in 0.0-999 more 0s-1g being where they have to shut down or go splat.

Actually, the 100D rule doesn't look like gravity itself, but does look like tidal force (which is different but related)

If we take the 100D of earth, (measuring it from center, not surface), that puts the gravity at 1/40000G or 0.000025m/s2. (Because it's 200 radii.)

A smaller world will have a smaller diameter and surface gravity, so the 0.000025G point will be closer still.

But direct gravity also has other issues. Like solar gravitation being much larger. it's surface G's are 27.9, at a diameter of just shy of 1.4million km..; size 869!

SizeGs0.000025 in radii0.0001 in km
10.1577.4661968
20.2510080000
30.4126.492101193.6
40.5141.422113137.6
50.6154.92123936
60.8178.886143108.8
70.9189.737151789.6
81200160000
91.1209.762167809.6
101.3228.036182428.8
869.37527.91056.41845128

Note that the solar limit in such a scheme is about 1/200 of an AU.
 
Actually, the 100D rule doesn't look like gravity itself, but does look like tidal force (which is different but related)

I was thinking in terms of being much too close for what he wanted. Even at a few thousandths of g, you're only out to 100d by your numbers. So, you'll have to make it an exponential setup (to get a goodly distance).
 
Gravitational acceleration is a poor fit. Tidal force works much better, as it falls off with the cube of the distance and raises by mass...
 
Well, that's one of us! :)

So I guess a version of 100d or equivalent is the way to go. I'll come up with something then and just have to test it along the way.

I was hoping to use mass/g of the star but that gets kinda funky since Astro does not calculate surface gravity of stellar bodies. I was hoping there was some other known barrier/border that I could use and easily calculate.
 
Well, I think Aramis was just pointing out that my statement about gravity and the 100d limit was wrong. I still think that if you use it as an exponent (a negative exponent, that is) you can get something that goes out as far as you want. But, it's going to have to be big numbers in that exponent, otherwise you get back to being pretty close to a planet.

What's the resolution on Astro's grav calculations? How many zeros after the decimal will it calculate?
 
Well, that's an issue for stellar bodies. It doesn't calculate any gravity measurements for stars. The planetary mass can display (AFAIK) any number of decimals. I think it defaults to about three decimal places when randomly assigning g.

(And yes, I was just using (c) as a short-cut for FTL.)
 
Have you found Astrosynthesis useful in-game for the players to use to see where they are and what is nearby, or is it mainly a GM's tool?

I have been working (slowly) on translating the Near Star Map from 2300AD into a 2-D Traveller-style hex map. Obviously the 3-D can't be simply squashed down to 2-D, so I am having to move things around, but mainly trying to preserve the relationships of systems that make up the Arms even if I am distorting their real world positions to do that.

OTOH, if I have a good enough 3-D tool to actually use the 3-D NSM data in-game, then I could save myself a lot of work and trouble by just working in 3-D rather than making the 2-D maps.

I've searched and read a few other threads on various other CotI subfora that mentioned Astrosynthesis, and have also read the listing and looked at screenshots at DRiveThru, none seem to really answer my question about use in-game, which I'd like to have a better idea of before laying out $35 to try it myself.
 
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