Re: [FT]SML question

David Rodemaker wrote:

> > > This also asumes there is no limit how deep into the gravity well
of the
> > > star you can actually use the FTL drive. If you cannot use a
> > FTL within a
> > > certain limit of the star, a whole new tactic opens up relating
> > to attacking
> > > a fleet as it travels in system (or being able to see what is
> > coming towards
> > > you and running before you`re killed <G>).
> >
> > It cannot be that restrictive a limit, or some things become
> > difficult. Thrust 2
> > must be practical for a merchant (the sample cargo ships all have
> > thrust 2), so
> > the time to get far enough out of the star's gravity well (and
> > back in, on the
> > return trip)can not be an overly significant amount of the total
> > trip time.	If
> > it takes several weeks to get to the jump threshold (at thrust 2)
> > and only a few
> > days to get to the destination star, it would be unusual to see a
> > cargo ship
> > with less than thrust 10.  The capital cost, and loss of cargo space
is
> > unimportant, it gets to the jump threshold in only a twenty-fifth
> > of the time,
> > and could make two (or more) trips before the slower, cheaper
> > vessel (with more
> > cargo space) gets to the first jump.
>
> It depends upon the profitability more than the turnaround time.
Otherwise
> everything would ship via Concord and Hydroplane <g>

The Concord and Ekranoplane (Huge wing-in-ground-effect aircraft that
pretends
to be a ship) are plagued by the fact that the ratio of their speed to
cost is
more expensive than conventional aircraft and ships.  Hydrofoils are not
used to
ship cargo because large cargo ships draw a lot of water already, and
there is
no space beneath them for the foils in most ports; it takes a lot of
power to
get a large ship foil born (even though the power requirements drop
precipitously, once the hull is out of the water); finally, the hull
must be
strong enough to be lifted out of the water by the hydrofoil struts. 
You cannot
simply add more struts, or the total drag eventually becomes almost as
bad as
the hull being still in the water.

If the jump threshold is approximately the orbit of Jupiter, and each
point of
thrust is one g [and we simplify things by ignoring the Sun's gravity
and
angular momentum], the time for a thrust 2 ship to get to the jump
threshold
from Earth's orbit is approximately 3 days, 8.5 hours (is that all?). 
The
thrust ten ship turns out not to have that great an advantage, it still
takes 36
hours, so it only kicks ass on short runs.  However, the further you
have to go
to the jump threshold, the better the thrust 10 cargo ship works.  It
turns out
that travel time only decreases with the root of the constant
acceleration, not
the square, as I mistakenly thought.

>
>
> However you could also move to the old Traveler model and have a safe
jump
> limit (past 100 diameters) and the dangerous inner ring (10-100
diameters)
> and the "only if you want to die" (within 10 diameters) model. I tend
to
> like this one somewhat.
>