On Fri, Jun 20, 2014 at 05:13:36PM -0700, Evyn MacDude wrote:
> How much does it change the game if you use Jump range as
> maximum speed?

It sounds like you're thinking of a "hyperdrive"-like system, where
the ship travel FTL for arbitrary periods of time.  Presumably still
using fuel at the same rate, about 10% volume per parsec.

In one respect, it makes a huge difference: getting around between
planets in a system is now trivial.  A week per parsec can now be
thought of as little as 3 seconds per AU.  Travel in a star system
becomes effectively just the sum of its 100D limits.

A lesser one is that jump-1 and jump-2 ships become pretty much
obsolete.  A J3 or J4 ship can now travel mains hitting quite a lot
more planets per year with not much greater running expenses.  In my
look at it some time ago, using local<->Imperial Credit rules so that
higher TL planets have more valuable currency, J5 drives weren't
generally worthwhile due to their increased TL requirement.

A third is that the volume devoted to fuel is substantially decreased
even for long-range trade.  In the standard rules, a J4 drives is
pointless without 40% fuel.  In "hyperdrive" rules, a J4 ship can
easily get away with lesser fuel tankage along any route where it can
top up every 1 or 2 parsecs.  For infrequent longer hops it can draw
fuel from bladders in the cargo hold.

What's more, it is now always feasible to store water or other
hydrogen-dense compounds, and extract the H2 en route.  Such compounds
can hold up to twice as much hydrogen per unit volume as LH2 does.  So
the 10% volume per parsec becomes 5% per parsec + a trivial cost and
volume for a purifier, which you should just build into the cost of a
jump drive and say they run on water/ammonia/hydrocarbon/whatever.

The outcome from that is that there is basically no need to reserve
large fractions of the ship purely for fuel tankage.  A typical
freighter now travels at 3 or 4 parsecs per week, stops every parsec
or two for fuel, and typically starts each hop with only about 10-15%
of its volume in fuel.

Since the typical intersystem time is now substantially less than a
week, travelling to planetary surfaces for trade and fuel becomes
comparatively much more expensive compared with docking at a farport
outside the 100D limit.  Some starships may have hefty maneuver drives
and streamlining, but for most it would be an irrelevancy that adds
nothing but expense.  The general rule would be that starships travel
between 100D limits, and cheaper spacecraft inside those limits.

Military fleet tactics and strategy would change immeasureably, but
perhaps that's a subject for another post.

- Tim