maximum velocity on manuver drive

[Enoki]

I don't know if this has been asked or explained before but in CT / MT no value is given. What is the maximum attainable velocity on a maneuver drive relative to C? Obviously, a ship on just manuver drive cannot attain the speed of light or exceed it but, how close can it come? .5C? .1C? Does it vary or is this a constant too?

 

[abomination]

In practical terms I'd imagine the limit would be determined by the amount of fuel you could carry.

No idea what that figure would be.

 

[steventirey1985]

Like abomination said, it would be limited by available fuel, either for the reaction drive, or the power plant if the maneuver drive is reactionless.

If enough fuel is available, you could just keep accelerating indefinetly, eventually reaching light speed. In short, there is no maximum as long as you have fuel.

 

[far-trader]

Of course for those who like their game a little harder (physics wise) you can put the limit (simplistically) at one of:

1 week of travel (1/2 week of acceleration) as this is generally the furthest anyone will travel under maneuver drives in a system.

4 weeks of travel (2 weeks of acceleration) as this is the standard fuel load for the maneuver/power plant.

There are hints in CT that mass is a factor for ship design, and if that is so then e=mc² must hold and your performance will degrade since your hull gets heavier the faster you go. So if you want even harder science you could do the calculations treating for mtons (per CT 1dton = 1000kg as a simplified average). Or in other rule versions use the calculated mtons and thrust tons.

The main problem with going with the unlimited except by fuel route is you can pretty easily carry enough fuel to exceed the speed of light iirc. Which is not realistic and introduces all the time dilation issues into a game that has never touched on them. And historically (in game) there are non-jump colony ships that are obviously very much slower than light speed. I once went looking for the examples to find their distance and time to work out the max velocity but couldn't find enough info. Maybe someone else has had better luck compiling it. That would be the best in game information.

Another problem with very high velocity is collision with even very small particles. Again, for simplicity, one could take the 1/2 week or 2 week accelerations noted above as being limits imposed by the ability of the ship to withstand such collisions and exceeding those speeds would mean damage or destruction of the ship in any such collision (which will happen eventually, and often enough to be an issue, though not necessarily often enough to dissuade players it should be enough to dissuade their characters).

 

[Dragoner]

Given unlimited acceleration, a ship could reach near C, but never quite reach it.

 

[far-trader]

In the CT universe of "adding vectors" it will not only reach but exceed C, and pdq to boot at 6G, eventually even multiples of C (though I don't really want to think of the relativity effects of actual multiple C velocity)

...or am I forgetting something obvious again?

 

[steventirey1985]

If we're talking realism, then no, a ship can't reach the speed of light. But there is nothing in the rules of the game that prevents a ship reaching or exceeding the speed of light if they had the resources (fuel) to do so.

And in a game that has some people teleporting long distances with just a thought, or devices to rip holes in space to send a craft across light years in a week, I have no problem with ships (eventually) reaching light speed with maneuver drives.

 

[Dragoner]

I try to keep some realism, jump can be explained through false vacuum, nucleation, worm holes, at least somewhat; psionics not so much.

IMO vectors work until you reach near C, but you can never reach it.

 

[Enoki]

I was just checking. So, limiting them to roughly .1C normally would be fine and putting an upper maximum of around .5C is where I will draw the lines.

 

[Dragoner]

you could go to .9 C theoretically, but I haven't done the math on a traveller starship to see what would take to get it there. I usually just extrapolate the book 2 travel times.

 

[dean]

Trillion Credit Squadron has a nice little blurb on the colonization of the Island Clusters sector, including some timelines on the original slow sub light colony ships.

 

[far-trader]

I don't think I had TCS when I was looking for info. I'm gonna go goof off with that for a bit and see what I can come up with there Thanks for the lead dean!

 

[far-trader]

OK, some very quick, very loose numbers.

From CT TCS:

New Home launches a STL colony ship to Colchis in 4788 that arrives in 4814.

Distance is 2 parsecs, duration is 26 years.

Best guess calculations in round figures put it as a 0.04G reaction drive under continuous thrust with mid point turnover. Top speed at the turnover is just over 0.5C (who said 0.5C? give that sophont a cookie!)

Based on the original Terran ship designs (asteroid ships) and an earlier thought that armour might allow a higher total speed vs impact risks how does this sound:

Let's take a TL8 baseline (pre jump drive) and a basic Planetoid, so our armour is 11. Using that I'd maybe go with the following table:

Armour Factor   “Safe” Velocity

  0                0.00 NOTE 1
  1                0.05
  2                0.10
  3                0.15
  4                0.20
  5                0.25
  6                0.30
  7                0.35
  8                0.40
  9                0.45
 10                0.50
 11                0.55
 12                0.60
 13                0.65
 14                0.70 NOTE 2

Where armour factor may include planetoid buffering but the maximum is TL8 before STL is superceded by jump drives.

Where "Safe" is a relative term (risk assessment vs speed) and presuming interstellar space where the risk is lowest is also the highest speed. The "Safe" speed is for interstellar space, not intersystem space.

Velocity is of course stated in fractions of C

NOTE 1 - Unarmoured ships are restricted to very low velocity such that they do not make good STL ships. My earlier notes on maximum velocity based on standard fuel or travel times should apply.

NOTE 2 - An arbitrary maximum partly to avoid very near C issues, though I really don't see high TL worlds doing any of this. Realistically STL craft will peak out at TL8 and be replaced by jump drives upon reaching TL9.

I'm not sure how well this relates to the 2000+ years for the original colony ships travelling from Terra/Sol to Islands/Rift. I haven't even looked at the range of that yet and might not bother

 

[The Oz]

...sigh....

I have done calculations on the maximum safe speed for TRAVELLER starships, using the numbers provided in STRIKER for converting explosion strengths (measured in kg of TNT) into penetration values.

Look here Max Safe Speed for Traveller Starships to see how I did the calculations.

 

[Icosahedron]

I like your rationale, Oz - a man after my own heart. I never figured all that out, but having glanced through your calculations, I may have discovered an error...

You state that a ship at 1G will reach 0.167ish of c in around 14 hours. That jarred with my recollection of my own Book 2 calculations from years ago, so I plugged in a few numbers.

Using plain newtonian figures for constant acceleration, v=u+at, with u=0, so v=at.
rearranging, t=v/a, and taking a=10, we get
t=v/10.

v= 0.1c = 3x10^7, so v/10 = 3x10^6 seconds
3 million seconds is 34.72 days, not 14 hours.
So most Book 2 journeys don't create problems with dust or relativity.

Unless I've made a mistake - it's 5am here, so that's quite possible.

FT - I doubt if the ark ships would do constant acc with a halfway turnaround. That's ok for short journeys, but the fuel use would be prohibitive IMO. I'd suspect a 1G drive firing for a few days, then a long coast, and a few days decel in-system at the destination would be more likely - just my 2Cr.

 

[far-trader]

FT - I doubt if the ark ships would do constant acc with a halfway turnaround. That's ok for short journeys, but the fuel use would be prohibitive IMO. I'd suspect a 1G drive firing for a few days, then a long coast, and a few days decel in-system at the destination would be more likely - just my 2Cr.

Well, iirc (but it's been a while) the (reality) numbers actually favour constant low acceleration over faster brief acceleration and coasting, both in terms of energy (fuel) and time, for long interstellar STL voyages. Numbers which may well go out the window with Traveller's rules though

 

[mike wightman]

Dan you took the easy way out.

Use the atlas of the Imperium and count the hexes from Terra to the islands cluster.

Convert to light years and calculate average speed needed to travel the distance in the time given.

Alternatively ask me - cos I did all this to calculate the speed of STL colony ships for the spica project a few years back.

 

[Icosahedron]

Well, iirc (but it's been a while) the (reality) numbers actually favour constant low acceleration over faster brief acceleration and coasting, both in terms of energy (fuel) and time, for long interstellar STL voyages. Numbers which may well go out the window with Traveller's rules though

Hmm. You could be right IRL, I haven't worked it out. When I made MTU canon - too many years ago (OMG, that was before I even learned the maths to work it out - don't do that to me, FT) - I did it with CT rules using integer drive numbers...