I'm trying to hammer the different rule systems into a coherent whole that preserves the feel of original Traveller. One issue is the rules for fuel consumption between vehicle design fusion power plants and ship design plants doesn't jive. So, without some hand-waving, I'm trying to bend them into alignment. Some notes for me while I work:
If we're going to stick with the Striker tables, which seem to be the basis of Megatraveller and TNE, then a standard factor 1, 1 energy point ship powerplant is ~250 megawatts and consumes 375 liters of liquid hydrogen fuel per hour. A displacement ton (dTon) of fuel would last 36 hours. Bending the scale efficiency rule to affect fuel consumption as well as power output gives us 108 hours. If we do away with the super consumption of jump drive fuel, but need regular power plant fuel for a jump, then for an approximately seven day jump, we need 4.7 dTons of fuel per parsec range, per 100 dTons of hull size. Since the CT rule was 10 dTons and my house rule was 5, that comes pretty close and we could round that to 5 to take into account tank insulation, pumps and plumbing, etc.
Hostile, 2300AD and The Expanse all use fusion reactors that consume almost no fuel but need massive amounts of reaction mass for maneuvering. Hostile says 1 dTon of fuel per 100 dTon of hull gives 24 "burns" at one G. If a burn is one 15 minute combat round's worth of thrust, that gives us six hours of thrust, which I feel is close to some calculations I have made previously based on 1000 metric tons of thrust rating. The HePlaR drive is 12.5 kiloliters per hour, which is 0.93 dtons per hour, so it is much higher. A straight fusion rocket from Striker would give 1000 metric tons of thrust and consume 0.18 dTons of fuel per hour, so a full dTon of fuel is five hours.
So, let's look at some stock CT ships and see how their fuel reserves work under the new system. We will go with no jump fuel, 5 dtons of fuel is 7 days power plant fuel/one jump, and one dTon is five hours of 1000 tons thrust.
The standard Type S Scout/Courier has 22 dTons of fuel. At Jump-2, she consumes 10 dtons of fuel, leaving her with 12. She can throttle her 500MW plant down to half and get a week's worth of operation on 5 dTons of fuel, leaving 7 for reaction mass. At her nominal 2G thrust, that gives her 17.5 hours of powered flight. That's pitiful compared to CT or The Expanse. In CT she would have 30 days of endurance on 2 dTons of fuel. If we go with the minimal fuel fusion reactors, she has relatively unlimited power plant endurance, but now she has 20 tons of reaction mass or 50 hours of 2G thrust or only 1.06 AU range at constant thrust. 100 hours at one G is 2.12 AU.
The reaction mass calculations are "power neutral", in other words, they don't need electrical power from the plant, just reaction mass. I did think about powered thrusters. One gram of reaction mass accelerated at 1/3 lightspeed gives ten metric tons of thrust. 100 grams at 1/3 C is 1000 tons of thrust. 100 grams a second is 5.14 kiloliters of liquid hydrogen an hour or 2.62 hours per dTon. Not an improvement, plus needing an unknown amount of power from the plant. If we could accelerate the reaction mass to 0.9 C, that gives us 7 hours, not a whole lot better. Hmmm, but that's liquid hydrogen. What about… water? That's what we use in The Expanse. You would need separate tankage for the two fuels, but that's no big deal. That becomes 37.5 hours of 1000 metric tons of thrust per dTon of reaction mass at 1/3 C acceleration. But how much power? Using the mass driver rules for power per projectile is not workable. If magnetically accelerating plasma was 100 times more efficient than moving a solid projectile, then 100 grams accelerated to 1/3 C is approx 72 megawatts. A factor 1/250MW plant would provide enough power for over 3000 tons of thrust. If we drop the ionized plasma efficiency to about 29 times more efficient to reduce our handwaving, then a 250MW plant would provide 1000 tons of thrust for our Scout and running her plant at full would give us 2Gs of acceleration roughly.
Now, we make a two parsec jump and consume 10 dtons of L-hyd fuel. 10 more gives us 5 days at level 2 power or 10 days at level 1. Two tons of water reaction mass gives us 75 hours of acceleration at one G or 1.19 AU of powered flight. If we went with a "minimal fuel" style reactor, we would have two dTons of liquid hydrogen for the plant and 20 tons of water reaction mass. That gives us 750 hours at one G for 119.4 AU or 375 hours at 2 G for 59.7 AU.
But that super maneuver range assumes a minimal fuel reactor, where the scout's standard 22 dtons becomes 2 dtons of reactor fuel and 20 tons of water reaction mass for a "Travellerized" Epstein drive. But… 20 tons of liquid hydrogen would feed a Striker system fusion rocket for 100 hours at 1000 tons thrust or 50 hours for 2000 tons. That gives our scout 2.12 AU range at 100 hours of 1G or 1.06 AU at 50 hours of 2G. Looking at my last modified Scout design, if I cut her back to the stock four staterooms instead of six, that gives me 28 tons of reaction mass for 140 hours/4.16 AU at one G or 70 hours/2.08AU at two Gs.
Also, all of our flight times have been on constant thrust. If my power plant (and life support) is basically unlimited, I could use a burn and coast route instead. Twenty hours at 2G would be 1,440 kilometers per second. A ten AU trip would take about 12 days, and we would still have 30 hours of 2G burn in reserve. Of course, in regular Traveller, we could do a microjump and get there in seven days without burning any reaction mass.
But back to the reduced fuel fusion reactors. Now do we make the fusion reactors in tanks minimal fuel as well? And the fusion rocket is based on the Striker power plant rules. GAAA, I've overturned the rule I was trying to make consistent as a basis for everything else! Well, the fusion rocket is a ROCKET; it needs reaction mass so that stays. The tank reactors can be minimal fuel which still needs some fuel to keep the reaction running, or maybe they aren't. Probably minimal fuel all around.
So, Jump drives no longer need excessive fuel, powerplants run on minimal fuel (one dTon per EP/250MW gives at least a month, small plants consume 1.8 liters per MW per day) and maneuver drives consume one dTon of fuel every five hours per 1000 tons of thrust, but no power from the reactor.
But wait! I forgot about scale efficiency! In Striker, large powerplants are more efficient. By the the time you get up to a one dTon or more ship power plant, it is three times as powerful per cubic meter. But it seems fuel consumption is based on the modifed output, not the base. If scale efficiency applied to fuel consumption as well, then one dTon of fuel would last 108 hours for the plant and 15 hours of 1000 tons thrust. My modified scout could have 15 days/360 hours of 1 G thrust and 27 days of plant operation. Jump still just requires plant power. A two parsec jump would use two weeks of plant fuel leaving 13 days of plant operation and 15 days of thrust, so we could rebalance that.
Hmm. 1.5 dTons of fuel per parsec jumped. Scout uses 3 dtons per Jump 2. Two jumps would burn 6 dTons, leaving 24, giving 36 days of plant ops and 10 days of one G thrust. Or she could make 8 jumps (!) And 13.5 days of plant ops and almost 2 days of one G thrust. Is that too much now?
Yes it is. Okay, let's take a step back. Power plants are not minimal fuel, but are scale efficient for power output and fuel consumption. One dTon gives 108 hours/4.5 days for a 250MW/1 EP plant. Fusion rockets are also both power and fuel scale efficient, one dTon gives 1000 tons of thrust for 15 hours now. The scout with 30 tons of fuel has 67.5 days of low power and 112.5 hours of 2G thrust. That still lets her jump too much. She uses 3 dtons of fuel per week long 2 parsec jump. We need to cut the range. So enter some handwaving. Jump consumes fuel at three times the normal rate (extra coolant, whatever). Our scout can make two jumps, burning 18 dTons of fuel. 12 tons of fuel left split 50/50 gives 27 days of low output power and 45 hours of 2G thrust or 90 of 1G thrust. She could jump three times and have 4.5 days of normal space power and 30 hours of 1G thrust.
I have a redesigned Type R 400 dTon Subsidized Merchant. She carries 48 dTons of fuel. Two Jump-1s burn 36 dTons of fuel, leaving her 12 for plant and reaction mass. Split 4/8 gives her 108 hours/4.5 days on her plant and 30 hours of 1G thrust. Since safe jump distance is about 7 hours or less travel time, she has plenty of reserve. She can take off, fly to the jump point, jump, land, move cargo, take off, fly to the jump point, jump and land again with a little over 3 dTons of fuel in reserve. The scout has a lot more normal space range because she is meant to travel around insystem to explore.
I don't have any revised military ships, but we can look at a stock design's fuel load. A 400 dTon Patrol Cruiser has 160 dTons of fuel for Jump 3 and is supposed to pull 4Gs. She is unarmored, so we will assume a gross mass of 4,000 tons. She will burn 54 dTons per Jump 3, two jumps is 108. Low power is 4 dTons every 4.5 days, 4G thrust is 16 dTons every 15 hours, but on routine patrols she would cruise at less. With 42 dTons and cruising at low power, she could cruise at 1G for 4.5 days and have 10 dTons in reserve for 9.3 hours of "pursuit" mode 4G thrust. However, operationally, she would refuel after each jump to have maximum fuel available for extended insystem patrols and in case battle damage ruptures fuel tanks. Refueling after jump would raise her insystem fuel to 96 dTons while keeping enough fuel to make a Jump-3.
Jump fuel: 4.5 dTons/parsec/100 dTons of hull
Plant fuel: 1 dTon per EP/250MW gives 4.5 days
Thruster fuel: 1 dTon per 1000 tons of thrust last 15 hours
Lucifer class DE, estimated 6,000 tons, 400 dTons. 204 dTons of fuel
Two Jump-4: 144 dTons of fuel, leaving 60 tons fuel. 12 for plant gives 13.5 days at minimal power. 48 for thrusters at 1G gives 120 hours. Or about 30 hours at 4G.
