On Sun, Aug 09, 2026 at 10:37:45PM -0400, The Traveller Mailing List wrote:
>
> ============================================================
>
> I'm fairly certain that - with the possible exception of GURPS Traveller - all the various
> Traveller ship construction rules simplified thetr thrust calculations by using ship volume
> rather than mass. So carrying just a bit less than a full hold or full tanks would
> certainly allow a "1-G" ship to lift off from almost any settled world. That's without even
> considering contragravity lift.
>
> Of course, a ship with wings or a lifting body hull shape could also fly up into the upper
> atmosphere of a 1-G world with a standard atmosphere. The gravity woukd be slightly less
> (~0.996-G) there. So a ship that masses 1200 tons on the tarmac masses "only" ~1195 tons at
> 10,000 meters altitude. That small difference might be just enough to let it (eventually)
> achieve orbit, particularly if pushed by a drive that consumes only power rather than
> reaction mass.
>

It's not just the change in the pull of gravity. Also to be considered is using the extra
force you have to thrust tangentially so as to help you achieve orbital speed. That faster
you are moving "parallel" to the surface, the less gravity you have to fight. If some other
technology got your ship to rest velocity 150 km above the surface of the Earth, a velocity
of ~ 7800 m/s parallel to the surface keeps you in orbit. Back of the envelope calculations
say this action would take something on the order of 25 minutes or less assuming the drive
is limited to exactly one Earth gee or 9.8 m/s^2.

--
Chris

      __o          "All I was trying to do was get home from work."
    _`\<,_           -Rosa Parks
___(*)/_(*)____.___o____..___..o...________ooO..._____________________
Christopher Sean Hilton                    [chris/at/vindaloo/dot/com]