On Wed, May 06, 2020 at 08:47:34AM -0700, Vareck Bostrom wrote:
>
> ============================================================
>
> T5 states: 
> If a ship has a drive capable of acceleration in Gs greater than world surface
> gravity, it may land or leave using that drive. Wings may increase drive
> acceleration.
>
> If a ship does not have a drive capable of Gs greater than world surface gravity,
> it must instead use Safe Boost or Safe Reentry.
>
> Safe Boost and Safe Reentry in turn for time to orbit of 5 hours x world size. The
> logic behind this isn't further explained that I see. 
>
> [ ..snip.. ]

I'm not sure what T5's Safe Boost and Safe Reentry are but I'll search
for them in the rules later. There are lots of ways to solve this
problem and it's generally much easier than you would think. The
solutions depend largely on how maneuver drives work. Note well that
this hasn't been explained well in any version of Traveller so far as I
can see.

Solutions
---------

1. Contra Grav

   If you assume that maneuver drives are contra grav then a 1G ship
   can effectively negate it's weight in a 1G gravity field and a
   strong man or a small attitude thruster could push it to a height
   where it could use it's drive to achieve orbital velocity. So,
   Contra Grave engines basically handwave the problem away.

2. No Contra Grav

   However much handwavium you need to apply to get maneuver drives to
   work in these universes, at the end of the day, I think that logic
   dictates that a 1G ship cannot take off in a 1G field here via a
   tail-stand. But taking off in a tail-stand isn't required for a 1G
   ship to achieve orbit from the surface of a 1G planet. Imagine a
   vacuum world with 1G, surface gravity, and a friction-less train car
   running on a track that ran around the entire equator. If G is 10
   m/s**2 rather than Earth's 9.8 m/s**2 then the spacecraft/train-car
   combo is "in orbit" at a speed of just over 8km/s because at the
   velocity tangential to the surface of the world the effective G is
   0 m/s**2. The spacecraft/train-car can achieve that speed in about
   13 minutes or 1.3 Book 2 space travel turns. In 1 Book 2 turn the
   same ship would:

   * be moving at 6 km/s;
   * have traversed 1800 km;
   * experience .441 G or 4.41 m/s**2 pull towards the center of the
     planet.

   The point here is that after 1 CT:Book 2 space travel turn thrusting
   laterally in a 1G field, a 1G ship could now leisurely achieve
   orbital height and velocity.

   For ships in a more realistic universe where 1G worlds have
   atmospheres and we don't have handwavium levitated train cars we
   need help, not much help but a bit of help.

   a. Booster rockets/vehicle

      The ship could get a ride into space on or in some vehicle that
      can "tail-stand to orbit"

   b. Air carried launch systems

      A vehicle using wings to generate lift or even a very large
      airship generating lift via buoyancy could carry the spaceship
      to an altitude where the atmosphere is much thinner (30km or more
      on Earth). From there the ships motors can push the ship into
      orbit. Note that this is a balancing act where the ship is going
      to trade some of that altitude for time creating orbital
      velocity. e.g. the ship will be thrusting somewhat laterally and
      somewhat anti-radially to avoid crashing.

   c. Over-boost

      Engines and motors in Traveller don't operate anywhere near like
      their *real world* analogs. In the real world, engines can
      usually be "over-driven" for short periods of time with minimal
      damage outside of slightly increased wear. In the same way, a 1G
      drive in a free trader can be pushed to produce 1.1, maybe 1.2 G
      briefly. Under those circumstances, a 1G free trader could
      achieve orbit of a 1G world by using a few handfuls of turns of
      over-boost. The cost to the ship would probably be that the
      annual overhaul would be that much sooner.

--
--
Chris

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