Missile design under the new rules

[Scandinavian (OP)]

I've been playing around a bit with the new missile design rules.

The basic missile design problem used to be optimizing to hit rate by varying the relative weight of engine and agility points, given a desired range, missile size and warhead size. With the new missile engine system, this is complicated by the fact that there are now a couple of new (and non-trivial) tradeoffs between engine power, agility and fuel use: A larger engine gives more than proportionally greater speed, because you can step up the power boost or reduce the fuel commitment. Conversely, agility can be traded for fuel, which can then be traded for a power boost (given fixed engagement range).

I'll spare you the two pages of algebra, and jump straight to the conclusions: If I do not constrain the agility and power boost values, the optimal configuration assigns negative agility values for all valid missile parameters. This means that the optimum is an edge case - agility is zero, the power boost is minimized, or the power boost is maximized (because all the functions here are nice, well-behaved, continuously differentiable functions.

A few numerical examples suffice to establish that the relevant edge case is not when power boost is minimized: Missile fuel budgets, for realistic fire control ranges, are comparatively trivial relative to engine sizes, so the gains from trading fuel for engine are naturally limited. Nor is it when Agility is zero, because this gives desired power boosts which are well beyond the top end of the tech tree. Which means that the relevant edge case is the one where engine boost is maximized.

Surprisingly, deriving an exact solution for this edge case turns out to be a non-trivial problem, but since fuel takes up a comparatively small part of any missile that you want to actually hit things, you can probably just use the old equation of [engine size] = [size - payload]/2 + 5*[size]/[agility per MSP], and then manually test whether rounding engine size up or down gives you the superior design.

Please note that the usual caveat applies: This optimizes to hit chances - in shipkillers, you typically want to trade some to hit chance for speed to get through point defense, and in busses, you don't want Agility at all, since they're not supposed to hit anything.

[Nathan_]

I find that if I can fix my desired range, available size, and likely target speed that the math is easy enough, if tedious to determine how much of each is worthwhile. the biggest change is probably that the granularity for engine sizes is fixed in .1 increments. It would probably be best to write a program to just brute force this though.

[tryrar]

What I find helpful when designing missiles under the new system is to design a junk 0.1 engine at max power value, then using that as a guide for the final design of the engine. For instance, designing a size 4 shipkiller, I start at size 1 warhead, .5 fuel, and .5 agility. Then, I size up my engine, and get to adjusting fuel, engine, and agility until I'm happy with what I got(keeping in mind that the final range of the missile is gonna be much greater with a purpose-built engine for the missile, due to larger missile engines being more fuel efficient). The only time when I break this process is designing missile busses, since it would be a max size engine anyways, the only variable is power, trading off wether I want a faster, shorter ranged missile, or a slower, longer ranged missile. Currently, for my Minuteman ISBMs, I'm using a 3x power booster engine, wich gets decent speed while still having a LOT of range, even when carrying 6 of my size 2 Exocets!

[Scandinavian (OP)]

What I find helpful when designing missiles under the new system is to design a junk 0.1 engine at max power value, then using that as a guide for the final design of the engine. For instance, designing a size 4 shipkiller, I start at size 1 warhead, .5 fuel, and .5 agility. Then, I size up my engine, and get to adjusting fuel, engine, and agility until I'm happy with what I got(keeping in mind that the final range of the missile is gonna be much greater with a purpose-built engine for the missile, due to larger missile engines being more fuel efficient). The only time when I break this process is designing missile busses, since it would be a max size engine anyways, the only variable is power, trading off wether I want a faster, shorter ranged missile, or a slower, longer ranged missile. Currently, for my Minuteman ISBMs, I'm using a 3x power booster engine, wich gets decent speed while still having a LOT of range, even when carrying 6 of my size 2 Exocets!

Personally, my algorithm is to figure out what size payload (warhead, sensors and stuff) I want to put in what size missile, and then allocate 1/2 of the free space to engines in an AMM, 3/4 to engine in an anti-FAC missile, and all of it to engine in an ASM, a bus or a sensor drone, and then taking the fuel out of the Agility budget. Under the new missile design rules fuel budgets get comparatively trivial as long as you make decently sized anti-ship missiles, so this is not a bad approximation.

[niflheimr]

I'm actually doing it backwards. I either decide on the speed for the missile , giving me the engine power , then tune the fuel efficiency and fuel amount to whatever range I need , or go with the range and optimize speed.

Once you get some decent tech maneuverability is not an issue anymore - couple of decimals in agility give you 70%+ hit rate against your enemies.

Still have to put the entire engine design in excel - as of now I still use aurora for fuel efficiency calculations.

[Charlie Beeler]

Missile fuel efficiency is fairly easy to plug into a spreadsheet. 

The basic formula is:
engine fuel use in liters per hour = (((eS*eT)*(pM))*(fE*5))*(((eS/5)^(-0.683))*(pM^2.5))

eS = engine size
eT = power points per MSP of engine for engine tech
pM = power modifier percentage
fE = fuel efficiency tech

(((eS*eT)*(pM)) is the power that the engine produces

(fE*5) missile fuel use is based on 5 liters per hour per point of power produced

((eS/5)^(-0.683)) fuel use modifier for engine size.  Steve's documentation stipulates that this should be at an INT() function level, I've pointed out in the v6.00 change topic that this will result in incorrect data.

(pM^2.5)  fuel use modifier for power multiplier.  Keep in mind when Steve mentions say a 200% increase the multiplier is 300% or 3X with the base being 100% or 1X.


With engine size granularity being limited to a single decimal (vs 4 in the previous version) I've found missile design to be simpler when assuming a fixed engine size maxed a the largest size that still allows the desired warhead and then balance agility and fuel for maximize hit probability. 


Keep in mind that because of how the program rounds various calculations the actual msp allocations for adding maneuverability points is not straight forward.

To add 1 maneuver point you need to add agility points equal to the desired missile size.

Most assume that for a single agility point the msp calculation is (1/Agility Tech).  But because of rounding you really only need (1/Agility Tech)/2.  By forcing the result to 4 decimal points you get a result that will round to the next mimics what the program is doing. 

Example:
Assume agility tech is 32 per msp.

Desired maneuver rating is 11 for a size 1 missile.

Without rounding the required msp for a single agility point should be .0313msp.  But because program using rounding this can be reduced to .0157msp and still have a missile maneuver rating of 11.

Now assume a size 4 missile with a maneuver rating of 13.  This needs 12 agility points.  Because of the rounding you only need .3600msp of agility.  If you only assume whole points that would be .3756msp.  .0156 doesn't sound like much, but in missiles under the new fuel rules that can be a significant change in range.

For building a construction sheet I use the expedient of a set reference cell that calculates what a single agility point msp is under the desired tech with the result rounded to 4 decimals.  I also have a second reference cell that divides that value in half and then subtracts .0001 and again forces a rounding to 4 decimals. (the second rounding is actually redundant).  The table rows then determine the agility points required for the desired maneuver rating and multiple by the first reference cell and subtract the second one.  There is still a little wiggle room at the 4th decimal but the results do match the programs results for the same msp expenditures. (at least under v5.6, I haven't verified against v6.0 yet)

[niflheimr]

Ty for the actual formula ,I didn't have the time to hunt for them

[Rokmonkey]

I've noticed something really odd.

With the new rules, it is very difficult to make a fast agile AMM.   Mine tend to go maybe 16000 km/s with a 15% chance to hit at 10k km/s.   Where as I can get a Size 5, warehead strength 4 ASM, going 30k km/s with 100% chance to hit at 3k km/s.   All of these missiles have crazy range too, with a fuel size of 0. 01

Is there some new trick?  I'm a little concerned I am making ASM's that even I can't take down with AMM's.   And if I can make these ASM's, I know the NPR's will have something even better.

[niflheimr]

Missile Size: 1 MSP  (0.05 HS)     Warhead: 1    Armour: 0     Manoeuvre Rating: 19
Speed: 70000 km/s    Engine Endurance: 1 minutes   Range: 4.1m km
Thermal Sensor Strength: 0.0072    Detect Sig Strength 1000:  7,200 km
Cost Per Missile: 1.3118
Chance to Hit: 1k km/s 1330%   3k km/s 437%   5k km/s 266%   10k km/s 133%

0.7 size - 3.5 power engine , .01 fuel , enough warhead for 1 damage.  So you can certainly do it . Tech level is magnetoplasma and 6damage/msp

[Steve Walmsley]

I've noticed something really odd.

With the new rules, it is very difficult to make a fast agile AMM.   Mine tend to go maybe 16000 km/s with a 15% chance to hit at 10k km/s.   Where as I can get a Size 5, warehead strength 4 ASM, going 30k km/s with 100% chance to hit at 3k km/s.   All of these missiles have crazy range too, with a fuel size of 0. 01

Is there some new trick?  I'm a little concerned I am making ASM's that even I can't take down with AMM's.   And if I can make these ASM's, I know the NPR's will have something even better.

What power/efficiency modifier did you use for the missile engine, and how large is the missile engine?

Steve

[Nathan_]

With the earlier techs you can't really get speedy fuel guzzlers, but once you get to 3x power mods(6x for missiles) that changes.

[Charlie Beeler]

What power/efficiency modifier did you use for the missile engine, and how large is the missile engine?

Steve

Steve a side note here.  Because of the missile engines being restricted to single decimal grainularity size 1 missiles will always be slower that larger missiles that have been optimized for speed, they just can't match the msp% can be dedicated to engines.

[Rokmonkey]

What power/efficiency modifier did you use for the missile engine, and how large is the missile engine?

Steve

I started a new campaign off a friends start, he had researched power modifier x3, which is super important I found.   But my previous missile design was:

Code: [Select]

Missile Size: 1 MSP  (0.05 HS)     Warhead: 1    Armour: 0     Manoeuvre Rating: 18
Speed: 16000 km/s    Engine Endurance: 17 minutes   Range: 16.5m km
Cost Per Missile: 0.6036
Chance to Hit: 1k km/s 288%   3k km/s 90%   5k km/s 57.6%   10k km/s 28.8%
Materials Required:    0.25x Tritanium   0.3536x Gallicite   Fuel x25

Development Cost for Project: 60RP

Warhead: 0. 25
Fuel Capacity: 0. 01
Agility: 0. 24

Engine: 0. 8EP Magneto-Plasma,  x2 EP modifier, size 0. 5MSP

Not AS bad as I remember.

[Rabid_Cog]

Not fast enough. ASM's go upwards of 20k with ion tech and reach 100m easily.

[niflheimr]

Power multiplier should be researched to at least 2.5 (5x in missiles) as soon as possible if you want to use the ordinance. Without it you will have slow , slow, slow missiles.