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]
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