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Seeking a Sublight Travel Calculator

A

AlacrityFitzhugh

SOC-4
Has anyone developed a program or somesuch to calculate long distance travel times via slower-than-light propulsion? Preferrably taking into account:
- Distance traveled
- Maximum engine thrust (in Gs)
- Maximum safe velocity (e.g., 0.25c)
- Time dilation effects for the entire journey (i.e., the difference between objective and subjective travel time)

Thanks!
Alacrity
 
You mean interstellar? At 6 G you'd need two weeks' acceleration to reach ~0.25c, covering 43.9 billion km. After that, you coast for 13 years/parsec. At 0.25c you get a time dilation of a few percent, which is insignificant in gameplay (a character will age a few months less than 13 years' transit time).

If the starship is protected against the particle radiation and can hack 0.99c+ it only takes a tenth of a light year or so depending on how mass expansion effects grav tech acceleration. You end up spending far more subjective time in acceleration than in cruising when you get enough nines. For that, the critical factor would likely be fuel.

If you're hopping over to the nearby companion star it may only be a few weeks. Again, time dilation is only significant game-wise at velocities much closer to c. GT:FI apparently limits companions to 400 au, and you won't get above 0.2c at 6G, or .08c at 1G. A companion would have to be several thousand au to reach significant time dilation factors, especially since you flip halfway to decelerate and don't stay near peak velocity for long.
 
Has anyone developed a program or somesuch to calculate long distance travel times via slower-than-light propulsion? Preferrably taking into account:
- Distance traveled
- Maximum engine thrust (in Gs)
- Maximum safe velocity (e.g., 0.25c)
- Time dilation effects for the entire journey (i.e., the difference between objective and subjective travel time)
Click to expand...
using HG2 rules, a one hundred ton scout vessel capable of maneuver 2, with an attached one hundred ton fuel tank and maneuver drive thus reduced to 1, can cross a distance of four light years in five years eight months. acceleration at 1G to maximum speed takes ten months (two tons fuel per month), the mid-journey takes forty-eight months at .84c (one ton fuel per month), and the deceleration takes ten more months (two tons fuel per month), for a total of five years eight months and a fuel usage of eighty-eight tons.

interestingly, lower maneuver drive values cross interstellar distances more quickly than higher maneuver drive values - the larger maneuver drives and power plants displace fuel and thus limit the time of acceleration

thus, jump drives are not necessary for interstellar exploration if the maneuver drives described in traveller are available.

limiting factors may be interstellar debris, air gasket integrity, food, life support, and boredom.
 
Food supply, oft overlooked, would take up a heckuva lotta space.

Now, keep in mind too that "Maximum thrust" and "Maximum sustained thrust" may well be two very different things.

Plus what exactly would define 'maximum safe speed'?

Also, what would you want to track in terms of relativistic dilation? Do you want to know the time it takes the crew? Or the time percieved back home? Or both?
 
The idea is to know how bad a deep space misjump could be. The ship is outfitted with emergency low berths, so food supply won't be an issue.

"Maximum safe speed" is to avoid the fact that the faster you go, the more damaging the interstellar gas and dust become, and the effects of doppler-shifted high-energy radiation. The ship in question wasn't designed for highly-relativistic speeds, so will be limited to some fraction of C that would be considered "safe" from these effects.

Regarding time dilation: Both. However, for speeds below .9c, this becomes pretty minimal.

Regarding thrust: Maximum sustained thrust. The idea is to accelerate to the maximum safe speed, then coast for a long time, then decelerate when needed.

I can probably do all this in a spreadsheet; I was just wondering if someone else had already done the work.
 
Well, I certainly couldn't begin to guess what fraction of the speed of light would be safe. 0.3 or less would be a WAG.

The problem with exceeding about .1 (or is it .3)c is that you start to see the mass effects, IIRC. This starts to affect the actual effect of subsequent thrust applied.

I don't think anyone else has already done this.
 
I did some calculations concerning maximum safe speeds for TRAVELLER starships, starting from the armor ratings in HG, converting them to STRIKER armor ratings, finding the number of demo points needed to breach such an armor, then converting demo points to kilos of TNT, and TNT into joules of energy, and then finding the speed a dust particle would have to be hit at to give that much energy.

What I got was that unarmored TRAVELLER starships can only safely accelerate to about 0.167c before the dust impacts become dangerous. Armored ships can easily reach several percent of lightspeed, and HG factor-15 starships can reach almost 0.60c.
 
Hello.
Silly thought, if you placed a nuclear dampener on the ship and had it turned on you wouldn't need to worry about the radiation.
If you had a heat superconductor on the front of your ship you could use it to generate power, so the faster you go the more power you get.
Another Silly Idea - If you fired an unfocused meson beam if front of your ship would it clear a path through the dust and gas???? - OHHHHH what a lovely antimissile defence system. Just found a use for those meson bays.
Bye.
 
What I got was that unarmored TRAVELLER starships can only safely accelerate to about 0.167c before the dust impacts become dangerous. Armored ships can easily reach several percent of lightspeed, and HG factor-15 starships can reach almost 0.60c.
Click to expand...
given the length of time involved one would have to consider not only dangerous damage, but erosion as well.

just how much interstellar dust and gas is out there?
 
gamma is 1/sqrt(1-ß²) and ß=v/c. Relativistic mass M = gamma·m0 and subjective time is t0/gamma.

. ß . . . . gamma
0.10 . . . . 1.005
0.20 . . . . 1.021
0.30 . . . . 1.048
0.40 . . . . 1.091
0.50 . . . . 1.155
0.60 . . . . 1.250
0.70 . . . . 1.400
0.75 . . . . 1.512
0.80 . . . . 1.667
0.85 . . . . 1.898
.875 . . . . 2.066
.900 . . . . 2.294
.925 . . . . 2.634
.950 . . . . 3.203
.975 . . . . 4.500
.980 . . . . 5.025
.985 . . . . 5.795
.990 . . . . 7.089
.995 . . . . 10.01
.999 . . . . 22.37

For back-of-the-envelope calcs you can ignore relativity. By the time you've accelerated to 0.20c you will have used more fuel than 2% total initial mass, and you engines should still be at initial G rating (unless there's something about grav tech that doesn't work that way, but what do we know).

Let's look at a higher velocity. At 0.60c if you've used 0.25/1.250 = 20% of your total initial mass in fuel, your acceleration is not diminished. With this we can calculate a "break-even" mass percentage for any velocity:

. . . . . . Break-even
. . . . . . Initial Mass
. ß . . . % Fuel Usage
0.60 . . . . 20.0
0.70 . . . . 28.6
0.75 . . . . 33.9
0.80 . . . . 40.0
0.85 . . . . 47.3
.875 . . . . 51.6
.900 . . . . 56.4
.925 . . . . 62.0

If you've planned an interstellar trip and have an enormous external tank, you can probably go as high as 62% initial mass before cutting off thrust. Your initial mass as you begin deceleration will be less than half, so either your fuel usage drops or your effective thrust rises correspondingly and you'll have enough fuel to match velocities with your destination system.

Obviously, in the case of a missed jump you're in for a very long trip at very low speed, and relativity is insignificant.
 
Originally posted by kaladorn:
Care to post a chart of armour rating -> fraction of C?
Click to expand...
By your command.... Oops, wrong universe.


</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">HG Velocity
armor (percent lightspeed)
0 0.1669
1 2.2603
2 3.7944
3 6.0955
4 15.983
5 15.983
6 15.983
7 30.478
8 30.478
9 30.478
10 30.478
11 59.020
12 59.020
13 59.020
14 59.020
15 59.020
16 59.020
17 68.150
18 68.150
19 68.150
20 96.379
21 96.379</pre>[/QUOTE]The reason you get those big blocks where the max speed doesn't change (from HG armor 11 to 16, for instance) is because of the increased granularity of the demo point conversion table in STRIKER at higher armor ratings.

Lionel:

As I understand nuclear dampers, they can only affect the decay of radioactive particles, either by speeding decay up or preventing it.

The "radiation" that a ship near lightspeed encounters is actually the ship hitting particles of spacedust while moving so fast. This "radiation" is not a nuclear phenomenon and could not be stopped or altered by a nuclear damper, if I correctly understand how a nuclear damper is supposed to work in TRAVELLER.

And firing a meson gun ahead of you would probably not clear a path, as any particles you pushed aside with the meson gun blast would be replaced by the high-energy particles of the meson gun blast itself. Which your ship would then run into.
 
Hello Oz.
Ar - arnt dont meson particules go straight through matter with no effect?????.

So dampeners dont work on fussion weapons (no decay). i assumed they stoped any radiation with a "force field" effect,(saturated magnetic field for the energy rad, gravitic band to bend particules away, Yes they dont stop all radiation but they stop most.

Yes the dust would be what the superconductor is for, each impact would convert matter to energy (heat and light and other things).
Thermo couples convert the heat to power.

Sorry i thought meson guns fired a beam of mesons that interacted with normal matter at there decay point and converted the normal matter to energy in a BOOM.

Just a thought if mesons dont interact with normal matter until the decay who would want a meson comunicator (do you realy want mesons decaying next to your head), also how does the coms know where the receiver is to calc the decay delay. More handwavium.
Bye.
 
Hi Speeders !

I strongly would recommend to stay away from going that fast in space

You might know, that I do not like the energy generating acceleration stuff anyway ;)

The dust concentration is a highly random thing. In real life we know about particle distributions by a just couple of satellites analysing impacting materials.
The numbers I have say, that there are 10E-20 kg dust per m3, with a max particle size of 10E-7 to 10E-9 kg.
So, thats only the particle distribution in earths orbit.
Straybow, any more numbers out there ?
There is no doubt, that there may be more or less dust in space depending on the location.
Ok, at least in Traveller we may have survey data dealing with those concentrations. Perhaps IISS has set up "save speed" limits

But, these may still be statistical distributions causing the high velocity trip to be lottery.
What would make me nervous anyway is the inability to maneuver / make course corrections.

IMHO the value of typical ships armour is rather useless against hyper speed micro particles, because of the unpleasant surface energy density.
Its just like a bullet proof vest, which looses efficiency againt low radius pointed projectiles.

Another effect of impacting particles will be a pretty range of X-rays...
Regarding dampers: Didnt MT ruleset tell something about controlled decay on lower rates, rendering fission warheads useless over time ?

Well, at least it all depends on the amount of dust in your way. Thats a kind of undefined variable. So - "clean the path" methods as presented by Lionel would be a great idea.
If there is nothing in flight path - let it go.
If you have no data - good luck


And back to Alacritys very basic question:
If got a set of excel charts doing this work.
But as I know Kaladorn, he is already putting together a web based travel time calculator.
Anyway, its a matter of an hour to put that together in VB (bad?), VB.Net(worse) or Java(ok?).

Best regards,

Mert
 
Lionel:

I expressed myself poorly. TRAVELLER has said that nuclear dampers work by projecting nodes that either enhance or reduce the strong nuclear force. What this means is that enhancing the strong nuclear force prevents atomic nuclei from decaying, which would stop radioactive decay (this is how damper boxes work). This is also how nuclear dampers stop fission warheads (according to FFS); they enhance the strong nuclear force so much that fission can't take place. Weakening the strong nuclear force is how nuclear dampers stop fusion warheads, by reducing the strength so much that you can't "stick" the hydrogen atoms together.

The key point is that the "radiation" a near-lightspeed ship encounters is not produced by the strong nuclear force, but just by the high-speed impact of the ship with the dust particles. As a result, a nuclear damper won't do anything to it.

In other words, a nuclear damper can =prevent= atomic nuclei from emitting radiation, but a nuclear damper cannot do anything to radiation that already exists. For example; if a radioactive atom =outside the range of the nuclear damper= decayed and sent a beta particle racing towards the ship with the damper, the nuclear damper could do nothing to stop that beta particle.

Meson gun particles do pass through normal matter without interacting, yes. But you need to read the description of how they work more closely. When the non-interacting meson gun particles reach their target, those particles decay into particles that =do= interact with normal matter, and it is this energetic decay that is the "explosion" of a meson gun burst. The energy comes from the decay of the meson gun particles, not from conversion of the material of the target. This energy is not all photons either, but includes various subatomic particles, which your speeding ship can then hit.

Now, using a repulsor to "sweep" your intended path might work, depending on just exactly how repulsors are supposed to work.

As for meson communicators, they work by using a small meson screen to cause the incoming meson communicator beam to decay when it enters the recieving meson communicator.
 
Hi !

Back to original request.
I finished that software piece.

Its able to calculate travel times (in-system/
interstellar) and relativistic effects, meaning
departure system ref-frame travel time and ships ref-frame travel time.

If there is still interest, I could offer program, source code or just some formulars


Regards,

Mert
 
Originally posted by TheEngineer:
Its able to calculate travel times (in-system/
interstellar) and relativistic effects, meaning
departure system ref-frame travel time and ships ref-frame travel time.

I **really** need this for a SF project I've been kicking around for years.

If there is still interest, I could offer program, source code or just some formulars


Regards,

Mert
Click to expand...
Yes please - any one of the above - so long as the maths are explained in such a way as to be translatable to a spreadsheet or somesuch by somenone with a BA in English anda good foundation in algebra & geometry. :D
 
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