On Sat, 26 Nov 2016 22:26:35 -0500, Rob Davenport <xxxxxx@gmail.com> wrote: >So a J-6 ship could "double back" cheaply? Jump out 1pc (40 hours, 12 >fuel) and jump back (another 40 hours 12 fuel) - 80 hours total, much >faster than normal (300 hours). Could be useful to get out of a jam >and come back on scene after 80 hours of repairs, rest, healing, to >"try again". Yes - but remember that when you built that ship, you paid for the full jump-6 capability, which means that the drive is large. You also have to pay for the extra fuel capacity. As an example, let's take a Marava hull (hull rate 200) and refit it for a J6 drive but max distance J2 (it will be able to do out-and-back J1 without refueling): Using the CE SRD for reference (because I have it handy), in a Marava hull (hull rate 200), you'd have a 35-dton drive (Drive Code F for J6) instead of a 15-dton drive (Drive Code B for J2). Right there, you're losing 20 tons of cargo capacity, per jump. Remember that the fuel usage is percent of hull rate, not dtons of fuel. For a Marava hull with a standard J2 drive, you need to allocate 20% to fuel, or 40 dtons. To do the J2 with the J6 drive, you need to allocate 24% to fuel, or 48 dtons. That represents an additional loss of 8 tons of cargo capacity, per jump. So, your modded Marava has only 54 dtons of cargo capacity, vs the 82 of a 'stock' Marava. That's going to play hell with the commercial viability, whether you use Ken Pick's Commercial Efficiency Rating to calculate it, or work up the financial profile the way I did. For military ships, the loss of mission space may be considered worthwhile, especially if your enemy doesn't know you have this drive. I don't think you'll see this among independent traders, and even large-corporation rosters are unlikely to have a large proportion of ships with uprated drives. >On Sat, Nov 26, 2016 at 6:58 PM, Jeff Zeitlin <xxxxxx@freelancetraveller.com> wrote: >>Depending on the reaction here, I may work this up into a full >>alternate-tech article for Freelance Traveller, much like I did with >>the Lyman Drive >>(http://www.freelancetraveller.com/features/rules/tech/lymanjd.html, >>reprinted from 2002 in the April 2013 issue). >> >>The core of the idea: A Jump-n drive can (usually) do Jump-m (m<n) in >>less time than it takes to do a Jump-n. However, it takes more fuel to >>do so than it would take a Jump-m drive, and the time required to do >>multiple jumps, even if there is zero delay between emergence from one >>jump and entry into the next, is greater than the single jump would >>be. >> >>A first cut at numbers: >> >>Assume that N is the rated jump capability of the drive, and that it >>uses fuel according to the standard rules (e.g., for CT, 10% of hull >>rate * N). Then, for a Jump M where M is strictly less than N,... >> >> Fuel usage = M/(N-1) times the standard fuel usage. >> >>Time: 168 hours is annoying to work with - it just happens to match up >>nicely with "a week". Let's tweak that: A basic jump isn't "a week", >>though it's generally treated as such on the calendar; it's 150 hours. >>Given that Jump N takes 150 hours, for a Jump M, where M is strictly >>less than N,... >> >> Time required for jump = M/(N-1) times 200 hours. >> >>In tabular form: >> >>Fuel (% of hull rate) >> >>Drive Jump 6 Jump 5 Jump 4 Jump 3 Jump 2 Jump 1 >>J6 Drive 60 60 48 36 24 12 >>J5 Drive -- 50 50 38 25 13 >>J4 Drive -- -- 40 40 27 13 >>J3 Drive -- -- -- 30 30 15 >>J2 Drive -- -- -- -- 20 20 >>J1 Drive -- -- -- -- -- 10 >> >> >>Time (hours) >> >>Drive Jump 6 Jump 5 Jump 4 Jump 3 Jump 2 Jump 1 >>J6 Drive 150 200 160 120 80 40 >>J5 Drive --- 150 200 150 100 50 >>J4 Drive --- --- 150 200 133 67 >>J3 Drive --- --- --- 150 200 100 >>J2 Drive --- --- --- --- 150 200 >>J1 Drive --- --- --- --- --- 150 >> >>Note that using a Jump N drive for Jump N-1 is really not something >>you want to do unless it's unavoidable; it takes *longer* without >>saving you any fuel. Also, the drive that uses the _least_ fuel for >>jump N is the Jump N drive - but at the cost of being the >>second-slowest. >> >>Comments/Discussion?
