Travel Formulas (probable errata)

[DonM]

In CT Book 2 (page 10), there are three formulas used to determine interplanetary travel times, distances and acceleration.

T= 2*sqr(D/A)
D=AT^2/4
A=4D/T^2

Now, a modified version of this appears in Referee's Companion (page 23), where the one formula is shown as:

T=sqr(D/A/32.4)

However, the "Computing Travel Times" mentions three formulas, but only the one appears. Is that one correct, or should the three formulas from CT be brought back. If that one is correct, what are the other two formulas?

This paragraph also mentions two graphs; are these the "In-System Travel Times" table (page 21) and the "System Travel" map (page 22)?

 

[aramis]

Should be the three from CT.

 

[Timmy]

Travel time formulas

T=sqr(D/A/32.4) appears to be wrong

T= 2*sqr(D/A), D=AT^2/4 and A=4D/T^2 should be rearrangements of the same formula, but the first should be T=2*sqrt(D/A). Only one of the three rearrangements needs to be included and could well be T=sqrt(4*D/A).

 

[OjnoTheRed]

We do need the three formulae, but bear in mind that BOTH the CT and MT formulae are correct. They use different units. CT uses scientific units, whereas MT uses more everyday units. I am reminded of Joss Whedon's quip about Firefly ships all moving at "the speed of plot". I think the MT units more reflect the interests of moving the story forward in Traveller (in any ruleset).

We can derive the other two formulae needed by re-arranging the formula that is given. I'm posting this from my mobile, if someone doesn't beat me to it, I'll post my solutions when I get a chance.

 

[DonM]

I eagerly await your solutions

 

[OjnoTheRed]

OK, the other two formulae for MegaTraveller are:

D = 32.4 * T^2 * A

A = (D / T^2) * 32.4

Where * is the multiplication symbol, and ^ means "raised to the power of".

Keeping in mind that in Classic Traveller, the formulae measure time in seconds, acceleration in m/s^2, and distance in meters. In MegaTraveller, time is measured in hours, acceleration in Gs (appx. 10 m/s/s), and distance in thousands of kilometres.

Thus, in the formula above, if you know the amount of flight time you have, and the acceleration at your disposal, you can work out how much distance you can cover. Useful if you want to flee and work out just how far away you can get with your ship in a given amount of time (e.g. star is about to go nova).

Alternatively, if you know the distance you have to cover and the time that you have, you can work out what acceleration you need to get there. Useful if you have ships to select from and absolutely, positively, have to be there in a certain timeframe (e.g. "overnight").