On Fri, May 08, 2020 at 04:29:49PM -0700, Vareck Bostrom wrote:
>
> ============================================================
>

> I'm not sure why Traveller ships would ever be "in orbit", they can
> just station keep at any particular point but that leads to the
> question of why not just land to rendezvous with the air/raft. If
> the ships were in orbit then the air/raft would have to accelerate
> to the ~8 km/sec orbital velocity to meet the ship and would then be
> in orbit itself anyway.

This all depends on how anti-gravity works IYTU, (In Your Traveller
Universe). The particulars fall here: does the anti-gravity device
consume energy to keep the ship in position or not. If it consumes
energy the reason for using orbit is obvious. If it doesn't consume
energy, there are still reasons to use orbit assuming that the device
can fail or has an off switch. The list had a discussion about this in the
past. I think we were asking if ships with Contra-Grav would have
bother to have landing struts. At the end of the day, again, it
depends on the magic of anti grav.

>
> It's difficult to shake the feeling that the traveller setting
> really doesn't understand any of this, a ship is either in space or
> on the surface of a planet despite the vague attempt at vector
> movement rules at one point.
>

CT doesn't mention how anti-grav works in any detail and that was
probably the smartest move. Other versions of Traveller go into more
detail. The downside to this approach is that it opens the door to
smart-a** players to figure out which physics rules can be broken.

I took the "Do ships have landing struts" discussion to a friend who's
a Physics professor at the University of Buffalo. He understands
General Relativity and Quantum mechanics where I don't go much past
Newtonian physics and Special Relativity. There were a few relevant
themes in our conversation:

* According to current physics, anti-gravity is impossible so this
  entire conversation is really moot;

* But, good Science Fiction is a lot harder without anti-gravity
  because you lose the *"shirtsleeve environment"* that we're all used
  to;

* The side that argued that the energy consumption is zero is
  technically correct since the energy cost is m*g*(delta-h) and
  delta-h is zero;

* There's also merit to the argument that anti-grav uses energy.  The
  idea is that your landing strut assembly is storing energy like a
  spring. E.g. your landing struts change shape as they support more
  and more of the craft on the ground and you could actually measure
  that change in shape as you loaded more and more mass into the cargo
  hold of the ship.

At the end of the day I think that my friend said since it's
impossible, yet necessary, you handle it the way you want to. That's
your job as Referee right. But if you want to be a good story teller,
be consistent.

I do not go with the H.G. Wellsian Cavorite mechanism of anti-gravity
IMTU. I find it easier to be consistent in a universe where
anti-gravity motors consume fuel when they are working. Thus ships
at 200km above the surface of a size 8 world stay in orbit case the
power to their G drives go out.

I would add that the concept of ships hovering at low orbital heights
such that they are reachable by grav vehicles is valuable and a
potential way for a non-streamlined ship to offload cargo to the
surface on a world with no high-port facility. This also provides a
solution to the "I can ride my air/raft to low orbit by the rules but
how do I get into my ship?" If you can remote control the ship then
move it to a parking place and just rendezvous with it by air/raft.

Finally, people don't have have much inertial mass so if you could get
to 150km above the Earth, you wouldn't need much energy or time to
reach orbital velocity.

--
Chris

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