Freelance Traveller

 by Alex Goodwin

The Problem

A major source of complaints in ship designs for Traveller, when using any of the standard rule sets, is the necessity for allocating major portions of hull space for fuel storage. At the same time, the reduced cargo capacity and increased cost of fuel makes most starships economically marginal at best, and impossible at worst. Given the description of purchasing a ship in the standard rules, it could be considered strange that most far and free traders aren't 'skips' (evading repossession for nonpayment).

Jeff Zeitlin proposed one method of alleviating the above problem (the Lyman Jump drive), and I will propose another in this article.

The Proposal

Densifying fuel storage (sounds a bit dumb, but that's what NASA et al call it) means what it sounds - increasing the density of the hydrogen fuel that Traveller ships guzzle by the shipload.

This has one of two results:

1. For the same mass of fuel stored, less volume (and thus less fuel tankage) is required.
2. For the same volume of fuel stored, more fuel can be carried.

So what does this mean in my Traveller universe?

Simple. Ships either become more profitable, less loss-making, longer-ranged, or some mix thereof.

(see Propulsion Systems from Takeoff to High Speed Flight, American Institute of Aeronautics and Astronautics, 1990, for the maximum density increase.)

This goes one of two ways:

Same mass, less volume:

• Divide tank volume by density multiplier, rounding odd spaces up, and record the number of spaces freed up.
• Multiply original, undivided tank cost by density multiplier.
• Empty tank mass remains unchanged (extra insulation and cooling systems, plus a preheat system or routing fuel feed through a source of heat, to reliquify the fuel before feeding into the drive reactor, account for this.)

Same volume, more mass:

• Tank volume remains unchanged.
• Multiply original, undivided tank cost by the square of the density multiplier.
• Multiply empty tank mass by density multiplier.

Note: To really make densified tankage work, a modified refining unit (capable of both refining and densifying fuel, which Jeff Zeitlin has christened a slurryfiner), also needs to be installed, giving the ship both active (cooling the stored fuel) and passive (don't hesitate, insulate) ways of keeping the slush fuel as slush. The slurryfiner is treated under option 2 above - volume occupied unchanged, mass of the original refining unit multiplied by density multiplier and cost of the original unit multiplied by square of density multiplier.

Economics

On their own, dense tanks would appear to automatically improve the viability of whatever ship they are installed/retrofitted in, with the improvement increasing with TTL of the tanks.

Unexamined assumptions have tripped up people great and small throughout history, so we'll take a look-see, noting that for maximum independence of movement and compatibility with existing fueling equipment, a similarly modified refining module is also installed.

For an example, I will use the Empress Marava-class Far Trader from GURPS Traveller p 135, and note that GTL 10 roughly equals TTL12.

Numbers pertinent to this examination:

Fuel tankage: 40 tons in 40 spaces.
Jump capacity: 2
Crew Requirements: 6 (uses 6 staterooms of 10 in design)
Revenue tonnage: 48 tons cargo + 16 tons of staterooms (4 staterooms@4 tons each) + 1.5 tons of low berths (3 low berths@0.5 tons) says 65.5 revenue tons.
Sticker price: 36.8 MCr
Base CER: 65.5 * 2 / 36.8 = 3.56

The Marava has to speculate a fair bit to pay her way at the moment.

We'll examine how the Marava's numbers change as the TTL of dense tankage and the attached fuel processor do.

TTL 10

New fuel tankage: 40 / 1.05 = 39 spaces (39 dtons)
Revenue space gained: 1 dton
Net space gain: 0 dton (remember that fuel processor?)
New revenue tonnage: 65.5 dton
Fuel tank cost increase: 40 * 0.16 * 0.05 = 320 Kcr
Fuel processor cost: 0.85 Mcr * 1.05^2 = 937 Kcr
Net price increase: 1257 Kcr / 1.257 Mcr
New price: 38.057 Mcr
New CER: 65.5 * 2 / 38.057 = 3.44

Clearly not a worthwhile refit. The extra cost results in no net gain, and lowers the Cost Efficiency Ratio.

TTL 11

New fuel tankage: 40 / 1.08 = 38 spaces (38 dtons)
Revenue space gained: 2 dton
Net space gain: 1 dton
New revenue tonnage: 66.5 dton
Fuel tank cost increase: 40 * 0.16 * 0.08 = 512 Kcr
Fuel processor cost: 0.85 Mcr * 1.08^2 = 991 Kcr
Net price increase: 1503 Kcr/1.503 Mcr
New price: 38.303 Mcr
New CER: 66.5 * 2 / 38.303 = 3.47

Still a net loss, though just barely better than the TTL10 refit.  The extra ton of revenue space could come in handy.

TTL 12

New fuel tankage: 40 / 1.11 = 37 spaces (37 dtons)
Revenue space gained: 3 dton
Net space gain: 2 dton
New revenue tonnage: 67.5 dton
Fuel tank cost increase: 40 * 0.16 * 0.11 = 704 Kcr
Fuel processor cost: 0.85 Mcr * 1.11^2 = 1047 Kcr
Net price increase: 1751 Kcr/ 1.751 Mcr
New price: 38.551 Mcr
New CER: 67.5 * 2 / 38.551 = 3.50

Still a net loss, even with the additional 2 tons of revenue space.  Getting closer to the original CER, though.

TTL 13

New fuel tankage: 40 / 1.14 = 36 spaces (36 dtons)
Revenue space gained: 4 dton
Net space gain: 3 dton
New revenue tonnage: 68.5 dton
Fuel tank cost increase: 40 * 0.16 * 0.14 = 896 Kcr
Fuel processor cost: 0.85 Mcr * 1.14^2 = 1105 Kcr
Net price increase: 2001 Kcr/2.001 Mcr
New price: 38.801 Mcr
New CER: 68.5 * 2 / 38.801 = 3.53

The gain in revenue from the extra tonnage is just barely keeping ahead of the increased cost.  Even at TTL13, this is a money-losing retrofit.

TTL 14

New fuel tankage: 40 / 1.17 = 35 spaces (35 dtons)
Revenue space gained: 5 dton
Net space gain: 4 dton
New revenue tonnage: 69.5 dton
Fuel tank cost increase: 40 * 0.16 * 0.17 = 1088 Kcr
Fuel processor cost: 0.85 Mcr * 1.17^2 = 1164 Kcr
Net price increase: 2252 Kcr/2.252 Mcr
New price: 39.052
New CER: 69.5 * 2 / 39.052 = 3.56

Finally, the break-even point.

TTL 15

New fuel tankage: 40 / 1.20 = 34 spaces
Revenue space gained: 6 dton
Net space gain: 5 dton
New revenue tonnage: 70.5 dton
Fuel tank cost increase: 40 * 0.16 * 0.20 = 1280 Kcr
Fuel processor cost: 0.85 Mcr * 1.20^2 = 1224 Kcr
Net price increase: 2504 Kcr/2.504 Mcr
New price: 39.304 Mcr
New CER: 70.5 * 2 / 39.304 = 3.59

From here on, we can expect to see further small, incremental increases in profitability.

Applying the same to an Akkigish class subbie merchant gives

(remembering the Akkigish has 178 revenue tons, 40 fuel spaces, jump 1, and a 47.4 Mcr price tag, TTL 12 and base CER 3.75)

Not a refit for this class of ship.