An Alternate Approach To Jump Drives In Ship Design

[Vargas]

I was noodling around with how to change Jump drives without impacting already established designs, (concentrating on CT's design sequences), so that they didn't require vast amounts of fuel. (And the problems which go along with somehow using up that much hydrogen on a Jump). My off the head solution was to reverse the tonnage figures used for the drive itself and the Jump fuel. For example, a scout ship would now have 20 dtons worth of drives and carry N dtons of fuel. (N being however big the design sequence says for J-2 drives for a 100 dton ship, I don't remember off the top of my head). And those 20 dtons of J-Drive don't need to be all heavy machinery but could be made up in part of plasma chambers or some other form of handwavium tech so that the scout doesn't wind up being far more massive.

My question is: What does this do to the basic assumptions behind the game and the Imperium setting? I guess rifts would now be far less daunting but what else?

 

[Scott Martin]

Part of this will depend on whether this changes the price of the drives... If the price is unchanged, then ships get significantly cheaper to operate (lower fuel costs) while if they cost the same per dTon, then most ships (probably even the Fat Trader) stop being profitable to operate, since a ship that's 10% jump drive (for Jump-1) gets a *lot* more expensive.

You'll also have to mangle the (LBB2) "Standard" hulls, since nothing with a jump drive will fit in the engineering spaces of the existing "standard" hulls.

Drop tanks basically go away, since they're really irrelevant, and designs like the Gazelle become impossible (since it would need to be 50% drive, and impossible to mitigate with a drop tank... "Drop Drives" or big strap-on units maybe?)

Scott Martin

 

[atpollard]

[FYI: the jump fuel becomes 1 percent of the ship, plus 1 percent per jump number - 3 dTons on a 100 dTon Jump-2 scout ship. The Jump Drive becomes 10 percent of the ship per jump number - 20 dTons on a 100 dTon Jump-2 scout ship.]

Accurate deck plans become a little harder since the fuel was a big user of all those odd shaped spaces.

 

[Spinward Scout]

You could always half the tonnage for both drive and fuel at each increasing Tech Level, keeping the current Jump Tech at the Jump-1 tonnage. Minimum of 1 ton per Jump Level. That gives you a 10 ton Jump-6 drive and a 1 ton Jump-1 drive at TL-15 for a 100 ton ship (if I'm doing the math right in my head). Leaves much more room for Fuel.

Spinward Scout

 

[aramis]

There was a rule on that for some items, SS, but I can't recall where it was.

ISTR 10% per TL; it was one of those "throwaway references" somewhere in CT, but I'm unable to recall where, and it was implied to be for personal gear.... And 10% per TL is a far sight less disuptive...

 

[atpollard]

There was a rule on that for some items, SS, but I can't recall where it was.

ISTR 10% per TL; it was one of those "throwaway references" somewhere in CT, but I'm unable to recall where, and it was implied to be for personal gear.... And 10% per TL is a far sight less disuptive...

The Ironmongery section of Mercenary (Book 4) had this:

In general, prices will tend to drop by 5-15% at each tech level after the level of introduction of an item, with examples of the item sold at the regular base price generally incorporating improvements or representing deluxe models. Most items of a military nature can, on worlds with a population level of 9+, be purchased in quantity at a discount. While discounts vary from world to world, a general average provides discounts of 20%. 40% and 60% at volume. Small arms and support weapons must be purchased in lots of 20 (a case) to receive the 20% discount, lots of 100 to receive the 40% discount and lots of 1000 to receive the 60% discount. Vehicles must be purchased in lots of 10 to receive the 20% discount, lots of 50 to receive the 40% discount, and lots of 100 to receive the 60% discount. Ammunition must be purchaed in lots of 500 units (clips, drums, cases, etc.) to receive the 20% discount, lots of 1000 units to receive the 40% discount, and lots of 10000 units to receive the 60% discount.

 

[Vargas]

Part of this will depend on whether this changes the price of the drives... If the price is unchanged, then ships get significantly cheaper to operate (lower fuel costs) . . .

Yes, the intent was that there'd be no difference in cost. With lesser fuel costs, traders become more economical to operate, which will lessen the push to adventure to make up the difference but overall that might not be a deal breaker.

And yes, the Book 2 division between engineering and non-engineering space would have to change/go away.

 

[Sifu Blackirish]

That tickles my mind a little...
I wanted to do something simple that would really show the difference between, say, a TL-10 and TL-12 jump drive or power plant. What I did was actually reverse the percentages so that 'primitive' drives are much more fuel hungry and larger than a higher tech counterpart.
It does create difficulties at first...60% fuel for a factor-1 drive, but things get much better at higher tech levels. How about a TL-13.5 ship that does factor 4.5 with only 25% fuel?
The only real difficulty is that I had to create a drive potential chart for EACH tech level.

 

[jwdh71]

IMTU (noncanonical) I simply changed the percentages used for fuel, i.e. instead of 10% per jump number, I changed it to 1%, and instead of 4 weeks of fuel, it was 40 weeks. This enabled me to use canon designs, as they would have 10 jumps worth of fuel at full jump number, which made them perfect for my own universe. It allowed me to not have a population in each system, allowing me to spread out the populated systems, and allow "bad" systems to be empty.

 

[Peter Schutze]

In my universe (more 2300AD than CT) I dont really use tech levels

Instead each major component has a available year and efficiency gain (per decade) modifier .... ie fission powerplants are available from 1960 and use x t per MW with a 0.5% modifier so by 2150 they get 9.5% smaller

no reason you couldnt do something similar with TL and major systems .... a TL15 J1 drive being say 5% smaller than the TL10 one ..... can see problems though trying to justify this for big drives unless you accept the idea that Jump range gain by TL isnt really the drive itself but the software etc

 

[Mithras]

Is it not feasible to increase fuel costs. Demand that jump drives require metallic hydrogen (the kind of stuff found at the deepest crushing levels of Jupiter's atmosphere). It is stored using gravity bottles under amazing pressures. This is now our new definition of 'refined', which means turned from skimmed hydrogen into metallic hydrogen. Perhaps it is a very expensive procedure requiring a proper starport, orbital processing station, or dedicated naval processor/tanker craft.

 

[aramis]

I was noodling around with how to change Jump drives without impacting already established designs, (concentrating on CT's design sequences), so that they didn't require vast amounts of fuel. (And the problems which go along with somehow using up that much hydrogen on a Jump). My off the head solution was to reverse the tonnage figures used for the drive itself and the Jump fuel. For example, a scout ship would now have 20 dtons worth of drives and carry N dtons of fuel. (N being however big the design sequence says for J-2 drives for a 100 dton ship, I don't remember off the top of my head). And those 20 dtons of J-Drive don't need to be all heavy machinery but could be made up in part of plasma chambers or some other form of handwavium tech so that the scout doesn't wind up being far more massive.

My question is: What does this do to the basic assumptions behind the game and the Imperium setting? I guess rifts would now be far less daunting but what else?

Assuming the standard paradigm of (Jn+1)% drive and (Jn x10)% fuel are being swapped

After pondering this, I see several issues.

1. it changes the relationship of jump drives to engineering crew OR it changes engineering crew
2. it changes the costs of fuel downward by a factor of 5 (for J1) to 8.5 (for J6);
3. it allows MUCH cheaper multiple jump designs. Note that a 2J4 can cross the rift; under standard rates that's 5% drive, 80% fuel; under your idea, that's 40% drive, 10% fuel, and thus still viable economically. Further, it makes a 3J6 ship possible: 60% drive, 21% fuel
4. it makes jump drives either much tougher per ton than other drives OR it makes jump drives massive damage sinks, depending upon which ruleset you use and how you track damage therein

Fuel is the #2 cost for merchants
Using the stock TTB Type A...
77250 Type A payment, halved for per jump
15000 fuel
08000 Crew LS
07500 Salaries (half month)
01686 AM share (1/22 of AM)


which moves 82 tons cargo, and 6 warm passengers.

A Book 5 swap will be cost effective at TL13+
MD +1 Td, -MCr2
JD -11 Td, +MCr1
PP1-9 -1Td +MCr8
PP1-D -3Td +MCr0
PP1-F -5Td -MCr8
Fuel -8Td +MCr0
At TL 9, therefore, cost goes up MCr7, and thus MP goes to Cr183333.33
91667 MP half
11000 fuel
08000 Crew LS
07500 Salaries (half month)
02004 AM share
but cargo goes up by 19 tons (MD -1, JD+11, PP-1, PPFuel -8) while cost per month goes up just under KCr15.

TL 13, Bk5 it drops again MCr 36.08
75167 Type A payment, halved for per jump
11000 fuel
08000 Crew LS
07500 Salaries (half month)
01640 AM share (1/22 of AM)
and has 21 tons cargo above base, for 103 tons

Now, using your suggestion on a Bk2 Type A, that reduces Jfuel to 15Td...
77250 Type A payment, halved for per jump
12500 fuel
08000 Crew LS
07500 Salaries (half month)
01686 AM share (1/22 of AM)

But on a Bk5-TL9, changing to 4 tons moves it to #4, plus the 2 tons PP
91667 MP half
08000 Crew LS
07500 Salaries (half month)
03000 fuel
02004 AM share

and at TL13
75167 Type A payment, halved for per jump
08000 Crew LS
07500 Salaries (half month)
03000 fuel
01640 AM share (1/22 of AM)
and has 21 tons cargo above base, for 103 tons


Really, if you're going to play with fuel, simply reducing by half and saying imperial regs require round trip fuel will have a much more stable effect.

Whilst at it, since bulk LS & food recharges are under Cr190/week (Best of JTAS 1, asteroid mining article), changing good quality LS to Cr500 per person per jump can be justified.