Fuel Consumption Formula for v6.00

[Steve Walmsley (OP)]

I am still playing around with the figures for fuel consumption. I am happy with the rate of consumption for warships but I think the rate of consumption for commercial vessels is too high. I've looked at different formulae to change fuel use based on the power modifier tech and ended up finding that a simpler formula than the one I use actually works out better.

At the moment the formula for v6.00 is (4 ^ Engine Power Modifier) / 4.

Some examples of power modifier vs fuel use with the above formula

0.25 x0.35
0.50 x0.5
0.75 x0.71
1.00 x1
1.25 x1.41
1.50 x2
2.00 x4
3.00 x16

While the fuel use rates above the 1.00 power modifier are fine, the ones below result in too much fuel use by commercial ships such as freighters and colony ships. So I am considering moving to a formula that simply takes the power boost modifier and applies a power, such as 2 or 2.5 to create the fuel use modifier. For example:

Boost   ^2     ^2.5     ^3
0.25   x0.06   x0.03   x0.02
0.50   x0.25   x0.18   x0.13
0.75   x0.56   x0.49   x0.42
1.00   x1.00   x1.00   x1.00
1.25   x1.56   x1.75   x1.95
1.50   x2.25   x2.76   x3.38
2.00   x4.00   x5.56   x8.00
3.00   x9.00   x15.6   x27.00

Bear in mind the current deployed version of Aurora uses x10 fuel for x2 power (GB engine), x100 fuel for x3 power (fighter engine) and x0.1 fuel for 0.5 power (commercial engine). However, base fuel use is much higher in v6.00. At the moment I think I am going to go for Power Modifier ^2.5 as the formula. However, this leads to a new problem. That is going to drastically reduce missile fuel needs, which are already lower than before (they used to be x10,000 compared to ship engines)

Boost Current ^2.5
4.00   x64      x32
5.00   x256    x56
6.00   x1024   x88

So I think I am going to multiply missile fuel consumption by 5 with technobabble about missiles being solid-fuelled which is less efficient but better for storage, otherwise missile range wouldn't even be a factor in missile design. I'll update the v6.00 thread as I do this but this post is to explain the reasoning behind the decision.

Steve

[Havear]

I've been playing around with more functions trying to get ones that look good, but I'm unfamiliar with the math routines VB6 has. Right now the only thing that seems to come close is sinh(x)-.1752 There were a few others that worked nicely... right until ~5x when it flew into the multi-thousands.

[TheDeadlyShoe]

I like both changes discussed. I was astounded when you mentioned the ASM from Crusade had only 0.2msp fuel.

Won't extreme range missiles still be more than possible just by using lower boost levels?

A lot of second stage possibilities here... *muses*.

[Steve Walmsley (OP)]

I like both changes discussed. I was astounded when you mentioned the ASM from Crusade had only 0.2msp fuel.

Won't extreme range missiles still be more than possible just by using lower boost levels?

A lot of second stage possibilities here... *muses*.

Yes, extreme range is still possible but the missiles will be slower than normal and therefore easier to shoot down. The main reason for the low fuel in the Gladius is that the Imperium had only researched 1.75 max engine power so the missile had only 3.5 engine boost, with correspondingly low fuel consumption. The re-designed missile (using the new rules) now uses twice as much fuel and has half the range. I've also halved the research cost for the higher power modifiers so x2.00 is only 8000 RP. Power mod x2.50 (which is the same as v5.60 missile engine power) is 15000 RP and x3.00 is 30,000 RP.

Gladius Updated
Missile Size: 5 MSP  (0.25 HS)     Warhead: 9    Armour: 0     Manoeuvre Rating: 10
Speed: 21000 km/s    Engine Endurance: 104 minutes   Range: 130.5m km
Thermal Sensor Strength: 0.075    Detect Sig Strength 1000:  75,000 km
Cost Per Missile: 3.6825
Chance to Hit: 1k km/s 210%   3k km/s 70%   5k km/s 42%   10k km/s 21%
Materials Required:    2.25x Tritanium   0.045x Boronide   0.075x Uridium   1.3125x Gallicite   Fuel x1000

Steve

[bean]

I didn't see this thread until after I posted in the other one, but I've thought more about the non-linear power requirement idea, and it solves all of your problems quite well.
If power required per unit speed increases with speed, this means that commercial craft will have lower fuel consumption than military craft almost by definition, as they rarely run around at the same speeds.  Missiles, on the other hand, will need more power, and thus more fuel, for a given speed.
I'm not sure of the exact formula to use yet.  Simple drag equations say velocity squared, but that seems a bit steep.
Another concept borrowed from naval architecture is hull speed.  Simply put, a longer hull has less resistance than a short one for a given speed (all else equal).  Apply that to Aurora with weight instead of length, and suddenly big commercial ships are more efficient, while small missiles are less so.