On 2017-10-04 22:53, Tim wrote:
> On Thu, Oct 05, 2017 at 05:20:51AM +0000, xxxxxx@comcast.net wrote:
>> The Computing Travel Time formula on p. 60 matches the GDW 0213 MT
>> Imperial Encyclopedia's Travel Times To Orbit p. 92 that a ship with
>> a 1G drive taking off from a size 8 world takes 38 minutes.
>
> That seems excessive.  If the ship can reach orbit at all, it's
> unlikely to take more than 15-20 minutes to do so.  I wonder what
> assumptions they used to get 38 minutes?

The travel time formulas provided assume you are travelling from point A
to B, starting and ending at the same velocity.  In other words
accelerating away from A to the point midway between, turning around
then decelerating the rest of the way to B.

It happens that, using that formula, if you want to travel 12800km (one
size 8 planetary diameter) using a 1g drive it takes 38 minutes.

So I'm inferring the table is using one planetary diameter as the
orbital height and has one flying straight up to end up at rest relative
to the planet's centre (so not actually in orbit), and ignoring the
effects of gravity.  The times are probably good enough for game
purposes, but I wouldn't read too much into the table about the
underlying technology assumptions being used.

BTW, in the absence of CG, it takes around 13 minutes after you've left
atmo to accelerate up to the velocity required for a low earth orbit.
With CG (assuming it cancels 99% of gravity) it would take 1.3 minutes.

--
Edward Swatschek
xxxxxx@bitslayer.net