Typical Travel Times [B02p10]

[ShapeShifter]

For any astrophysicists, or NASA engineers on the boards:

Are the equations given in Book 2 remotely accurate/plausible in the real-world, or are they convenient fictions for gaming purposes only?

I've written an Excel sheet with the equations, and the travel times seem very brief given the distances I feed into the equation.

E.g.: If I'm zooming through space at 6 G's and have to go 50,000,000 miles (8.046720E+10 meters), my spreadsheet tells me it'll only take 20 hours, 20 minutes and 43 seconds. Am I doing this correctly???

Ex. no. 2:

If I travel at 6 G's over a distance of 1 LY (9.460730E+15 meters) it will only take 10.38 months. Correct?

 

[mike wightman]

Yes they are accurate - no they are not plausible

 

[BlackBat242]

Ex. no. 2:

If I travel at 6 G's over a distance of 1 LY (9.460730E+15 meters) it will only take 10.38 months. Correct?

Except your ship has only 1 month's maneuver fuel*... which significantly reduces the amount of time you can be under 6G acceleration/deceleration... and that whole "can't go faster than the speed of light in normal space" thing kinda gets in the way also.

*normal design... add in the jump fuel being used for the maneuver drives as well, and figure out how many hours acceleration/deceleration you get (half/half)... then figure your top speed. I bet you spend quite a few years coasting to cross that 1LY!

 

[Gadrin]

I believe in CT most ships have ~30 days standard rations. So you'd probably accel to 6Gs go into cold sleep and hope you have the power to last to the other end of the trip, awake, turn around at mid-point to decelerate, go back to sleep, wake and come out near the destination.

GURPS Traveller has fusion PPs that last for decades if not longer, so if the low berths work, it might be plausible, hopefully no breakdowns. CT has plenty of "berths work for decades" and the Zhodani sleep for a decade on their Core Expeditions.

Not sure of the fuel consumption in CT for maneuver. I had thought it said "unlimited" but I might be taking that out of context.

It might work, with no breakdowns...at least in theory.


>

 

[tbeard1999]

For any astrophysicists, or NASA engineers on the boards:

Are the equations given in Book 2 remotely accurate/plausible in the real-world, or are they convenient fictions for gaming purposes only?

I've written an Excel sheet with the equations, and the travel times seem very brief given the distances I feed into the equation.

E.g.: If I'm zooming through space at 6 G's and have to go 50,000,000 miles (8.046720E+10 meters), my spreadsheet tells me it'll only take 20 hours, 20 minutes and 43 seconds. Am I doing this correctly???

Ex. no. 2:

If I travel at 6 G's over a distance of 1 LY (9.460730E+15 meters) it will only take 10.38 months. Correct?

The formulae given are accurate, but remember that they envision accelerating to midpoint, then decelerating.

So, if calculating straight line distance, you'd double the result on the table. (I.e., a ship that accelerates at 1-G for 633 seconds will travel about twice the distance indicated on the chart (2000km instead of 1000km). But a 1-G ship that accelerates to mid point for 316.5 secs, then decelerates for 316.5 secs will about the distance indicated on the table (1000 km).

 

[aramis]

Yes they are accurate - no they are not plausible

TO clarify this cryptic comment...

Mike means that yes, thosw are the real formulae...

But NASA doesn't use them since NASA missions don't have enough fuel for more than (usually) 20G-hours, and often less, and usually are at 3+ Gs. (Deep space 1, by my rough guess, got nearly 100GHours... over 9 months.... and about 0.005G)

 

[mike wightman]

Sorry I should have elaborated on that answer earlier.

The formulae and tables given in CT for tranel times are based off newton's laws of movement and the equations derived - so they are physically accurate.

What they don't do is take into account orbital velocity, escape velocity, relative motion of planets around the system etc. - all things that NASA does have to take into account.

As has been mentioned the really implausable bit about Traveler ships is their high acceleration number and length of time they can maintain this acceleration - a 1G ship is travelling awfully fast if it accelerates constantly at 10 metres per sec per sec for 15 days.

 

[aramis]

For comparison, a 1G Traveller ship with 28 days endurance has 24*28*1=592 G-hours of ΔV...

The only thing that NASA has done that even comes close is the DS1 mission...

And a Traveller 6G ship is pushing 4750 G-Hours...

 

[mike wightman]

Which makes acceleration to close to the speed of light a "real" possibility in Traveller. There are canon examples of STL ships travelling at very high fractional c velocities.

 

[The Oz]

Which makes acceleration to close to the speed of light a "real" possibility in Traveller. There are canon examples of STL ships travelling at very high fractional c velocities.

But there is a "speed limit" of sorts in Traveller; the ability of the ships to withstand impact with space dust and debris at high fractions of c. I did some calculations on this (using STRIKER as the guide) and found that unarmored Traveller starships are limited to a fairly low velocity (compared to c) by dust impacts.

I reported on this earlier here on COTI, a search through the archives should find it.

 

[mike wightman]

All you have to do is armour the bow of your STL ship

Somewhere I calculated the average velocity of the STL ships in the Islands Cluster Trillion Credit Squadron, and in the Imperium board game ships can traverse interstellar space using their maneuver drives.

 

[flykiller]

But there is a "speed limit" of sorts in Traveller; the ability of the ships to withstand impact with space dust and debris at high fractions of c.

would this work?

The Argo

 

[pendragonman]

Please don't make me try to count them on the layouts...

How many low births? How many personnel could be carried?

In other words, could this be used as a sublight colonial transport?

 

[flykiller]

How many low births?

uh, all of them. but the argo has 16 low berths and 14 cabins. it's meant to be an exploratory vessel, but depending on supply rules there may be enough room in the cargo bays for quite a few low berths.

by the way, the argo link is fritzed right now, I'll fix it as soon as aol lets me back on.

 

[The Oz]

All you have to do is armour the bow of your STL ship

Somewhere I calculated the average velocity of the STL ships in the Islands Cluster Trillion Credit Squadron, and in the Imperium board game ships can traverse interstellar space using their maneuver drives.

Oh, yes; I'm not saying that Traveller ships (given enough maneuver fuel) can't reach relativistic speeds. I'm just saying that there's another limit besides their fuel tanks.

According to my calculations, an unarmored Traveller ship can reach a maximum safe speed of 0.167% of lightspeed, while a factor-1 armor ship can safely handle 2.26% of c. Put factor-15 armor on your ship and your safe speed reaches just about 60% of c.

 

[ShapeShifter]

Thanks for the input!
I don't have a background in the hard sciences like physics, so I suppose the equations are just to be accepted as they are for game-purposes with a wink and a nod and a healthy dose of RPG handwavium.

However, if I were to model a more realistic subluminal travel scenario, I'd have to go back to college and read Dr. Hawking's A Brief History of the Traveller Universe. :rofl:

 

[tbeard1999]

Oh, yes; I'm not saying that Traveller ships (given enough maneuver fuel) can't reach relativistic speeds. I'm just saying that there's another limit besides their fuel tanks.

According to my calculations, an unarmored Traveller ship can reach a maximum safe speed of 0.167% of lightspeed, while a factor-1 armor ship can safely handle 2.26% of c. Put factor-15 armor on your ship and your safe speed reaches just about 60% of c.

The first edition of LBB1 implied that there was a limit of around 288 turns of full acceleration (pg6). Each turn in the first edition was ten minutes, so this worked out to 48 total hours of acceleration. This language was deleted from the second printing of LBB1. If it still applies, then a 6-G ship could reach about 9% of lightspeed (half that if the ship intended to be able to stop). However, this limit was framed as a *fuel* limit, so it's reasonable to assume that the ship could approach lightspeed if it carried enough power plant fuel.

Determining the danger for micrometeorite impacts is highly speculative, because (a) the damage varies proportionally with mass size, (b) we don't know the frequency of such impacts, and (b) we don't actually know what happens when objects strike one another at near relativistic speeds. However, a 1 gram object struck at .75C would have the energy of a tactical nuclear weapon--11 kilotons. At .9C, 29 kilotons. At .99C, 132 kilotons.

For any number of reasons, I prefer there to be a very low "speed limit" in normal space. Getting obliterated by space dust is as good a reason as any.

Note that the implications of my statements above make a universe with truly reactionless drives *very* different (and far scarier) than the OTU. A scoutship with a mass of (say) 500 metric tons traveling at .99C would contain kinetic energy comparable to a 66 million megaton nuclear weapon. This is thousands of times more than the combined nuclear arsenals of the Earth today. The impact of such a ship would annihilate all life on Earth.

No sane government would allow private starship ownership in such a universe.

So there must be a speed limit for Traveller drives.

 

[aramis]

Under MT, while a bit high, I limited it to 0.5PSL per AV. it was simple, if not realistic. Excess was PSL-(AV/2) radiation hits per day, with factor equalling the hits per day.

Just a house rule... only applied once

 

[far-trader]

All you have to do is armour the bow of your STL ship

And the aft if you want to survive the deceleration part