Author Topic: Help with engine design  (Read 1945 times)

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Offline Rich.h

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Help with engine design
« on: November 16, 2014, 05:19:18 AM »
Hoping someone can help out here an issue I always have when designing ships. I generally get confused about the order in which I design a ship, do I decide what size I want it to be, then how fast I want it and, and finally make an engine based on math for the requirements. Or make an engine based on speed/efficiency then use it for hulls. Often I find myself simply making an engine (let's say a big one), I will make it as efficient as I can for a good power rating ratio. Then I end up shoehorning it into various hull designs.

I feel this is likely leaving me with huge gaps of design efficiency and probably not a good method. Is there some sort of rule folks use such as a hull design will have x% of it's total size given over to engines? I know if i bust out the calculator and some blank sheets I could go through the design process to get this nailed down, however I don't really want to go into quite that much depth. I am hoping there is a simple guideline that can be followed to give designs that have reasonable statistics with out too much head scratching, what are other users methods for this?
 

Offline Paul M

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Re: Help with engine design
« Reply #1 on: November 16, 2014, 06:52:31 AM »
This may or may not help.

First I decide based on my mission what size of ship I will build.  This is limited by the size of my space yards but also by cost and other considerations.
Second I design the engines I will use over all my ships.  A standard engine is easier to use in designs, is less expensive to get out of R&D as well.
Third I design the ship and give for a military ship about 20-25% to engines.
Fourth I iterate around until things look good.

I don't worry about optimizations, my main goal is to get a ship that can fulfill my mission requirements.
 

Offline Prince of Space

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Re: Help with engine design
« Reply #2 on: November 16, 2014, 09:05:23 AM »
The ship design process is really an iterative one: design a ship, find flaws, adjust the design, find more flaws...

I like to design a mission package first, since it doesn't matter if I get the engine to fuel ratio right if i can't get enough missile launchers and fire controls to the battle. Then, I've found that the mission package is generally about 40% of the total tonnage, so I estimate the total tonnage and allocate engines and fuel using a spreadsheet like the one posted here:

http://aurora2.pentarch.org/index.php/topic,5482.msg56842.html#msg56842

That gets me most of the way, but it still takes some tweaking. It doesn't work as well for ships with very long or very short deployment times, or that need to fit within a given tonnage restriction, such as fighters or any other ship that fits within a hangar.
 

Offline Jorgen_CAB

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Re: Help with engine design
« Reply #3 on: November 16, 2014, 06:44:49 PM »
I mostly consider any system I need to design based on current need and what I expect from a ship, the fleet or enemy capability. One of the most important thing to consider is almost always RnD time and resources for each component you want to use in your fleet. For that reason engines tend to get standardized. I would often have two types of military engines (if you don't count fighter/FAC engines), one for smaller ships and one for larger capital ships, it is possible to go for one smaller engine if fuel efficiency is less of a concern to you.

After this whether you are interested in fuel efficiency or raw power in an engine design is all up to your fleet doctrines. Fuel efficient engine also have the upside of being cheap to research while powerful engines are the opposite.

The larger an engine is the more expensive and inflexible they are in ship designs but give your ships better fuel economy.

Once all this figuring is done you need to decide what type of ship it is your going to build... what is its mission, what speed do you desire and what size will the ship have to be able to fulfill that mission?
If you have an engine and you know the speed you could calculate the size such engines could support for that particular speed you want.
 

Offline alex_brunius

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Re: Help with engine design
« Reply #4 on: November 17, 2014, 06:11:56 AM »
one for smaller ships and one for larger capital ships, it is possible to go for one smaller engine if fuel efficiency is less of a concern to you.

I usually design 3 engines as a basis for all my ship designs.

One efficient size 5 engine (250ton) for GEO/GRAV and other long range exploraiton scout/ambulance. ( not always needed every engine level and cheap to research anyways).
One high power mod size 10 engine (500ton) for smaller Military ships that need to go fast and don't need range, (FAC/Destroyers/Cruisers)
One medium efficient size 50 engine (2500ton) for Capital ships that get a few systems range and may need extra fuel to launch parasites.

This gives me a good and flexible setup to use for most ships. For example if I am designing a 8000 ton Cruiser I may opt for the a single big engine if I need range/efficiency or go for up to 6-8 size 10 engines for a beam Cruiser that need high speed.
 

Offline 83athom

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Re: Help with engine design
« Reply #5 on: November 17, 2014, 07:10:46 AM »
I always do a 0.5EP, a 0.75EP, and a 1.0EP of the sizes 5, 25, and 50 for engines for any purpose, as well as a 1.0EP, 1.5EP, 2.0EP, and 3.0EP size 1 engines for any types of fighters I would need.
Give a man a fire and he's warm for a day, but set fire to him and he's warm for the rest of his life.
 

Offline Rich.h

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Re: Help with engine design
« Reply #6 on: November 23, 2014, 06:14:08 AM »
The ship design process is really an iterative one: design a ship, find flaws, adjust the design, find more flaws...

I like to design a mission package first, since it doesn't matter if I get the engine to fuel ratio right if i can't get enough missile launchers and fire controls to the battle. Then, I've found that the mission package is generally about 40% of the total tonnage, so I estimate the total tonnage and allocate engines and fuel using a spreadsheet like the one posted here:

http://aurora2.pentarch.org/index.php/topic,5482.msg56842.html#msg56842

That gets me most of the way, but it still takes some tweaking. It doesn't work as well for ships with very long or very short deployment times, or that need to fit within a given tonnage restriction, such as fighters or any other ship that fits within a hangar.

Not sure if I am doing something wrong or if there is an error in this spreadsheet but the results are not coming out correctly when put into practice, here is an example.

I tell the sheet I want a 50k ship to do 8k speed with the following specs. (this is for multiple engines)

Engine tech - Internal confinement 32EP/HS
Fuel consumption 0.25 per hour
Total ship size - 50,000 tons
Desired speed - 8000km/s
Desired range - 150b/km

This then tells me I need the following.

2x 50-HS engines with Power Modifier x0.8, plus 38.18 HS of fuel, totaling 6909 tons of engine and fuel space.                              

However when I put this in a 50k ship the results are vastly inferior to the desired ones, here is a quick copy of a design I had with some extra rubbish thrown in to get to the exact 50k mark.

Quote
Typhoon - Copy class Command Carrier    50,000 tons     1049 Crew     9200.4001 BP      TCS 1000  TH 2560  EM 0
2560 km/s     Armour 6-120     Shields 0-0     Sensors 288/288/0/0     Damage Control Rating 107     PPV 199.4
Maint Life 1.95 Years     MSP 5405    AFR 425%    IFR 5.9%    1YR 1868    5YR 28025    Max Repair 576 MSP
Intended Deployment Time: 12 months    Flight Crew Berths 1   
Flag Bridge    Hangar Deck Capacity 10000 tons     Magazine 3699   

1280 EP Inertial Fusion Drive (2)    Power 1280    Fuel Use 7.16%    Signature 1280    Exp 8%
Fuel Capacity 2,000,000 Litres    Range 100.6 billion km   (454 days at full power)

Donlan Heavy Industries 25cm Far Ultraviolet Laser (1)    Range 144,000km     TS: 8000 km/s     Power 16-8     RM 5    ROF 10        16 16 16 16 16 13 11 10 8 8
Quad Mcguyer & Briano Gauss Cannon R40k - F4/5 Turret (4x16)    Range 40,000km     TS: 20000 km/s     Power 0-0     RM 4    ROF 5        1 1 1 1 0 0 0 0 0 0
Mcguyer & Briano Phalanx CIWS (4x8)    Range 1000 km     TS: 32000 km/s     ROF 5       Base 50% To Hit
Sadberry Foundation Fire Control R72k-T40k (FTR) (2)    Max Range: 144,000 km   TS: 40000 km/s     93 86 79 72 65 58 51 44 37 31

Mcguyer & Briano Size 12 Missile Launcher (3)    Missile Size 12    Rate of Fire 75
Size 5 Anti-ship Missile S30 - W16 - R14 (164)  Speed: 30,700 km/s   End: 7.9m    Range: 14.5m km   WH: 16    Size: 5    TH: 225/135/67

Sadberry Foundation Active Search Sensor MR5000 - 259m (1)     GPS 14400     Range 259.2m km    Resolution 100
Sadberry Foundation Thermal Sensor TH288 (1)     Sensitivity 288     Detect Sig Strength 1000:  288m km
Sadberry Foundation EM Detection Sensor EM288 (1)     Sensitivity 288     Detect Sig Strength 1000:  288m km

ECM 30

Missile to hit chances are vs targets moving at 3000 km/s, 5000 km/s and 10,000 km/s

This design is classed as a Military Vessel for maintenance purposes

As you can see neither the speed nor range is matching up to what the sheet is saying using the engine design suggested and slightly more fuel than was suggested. Have I made an error somewhere in understanding how this sheet works?
 

Offline GreatTuna

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Re: Help with engine design
« Reply #7 on: November 23, 2014, 06:39:01 AM »
This is because you chose Internal confinement engines, not Inertial.


 

Offline Rich.h

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Re: Help with engine design
« Reply #8 on: November 23, 2014, 06:55:05 AM »
Oops that is a typo on my part, I am indeed using both inertial tech for the sheet and my actual engine design. I have noticed a couple of other issues too, while the total EP on the sheet is correct other parts are not. The sheet says that using this tech I will have a total EP of 2560 for 2 x 50HS at 0.8 power, this is correct as the in game design shows these engines as having 1280EP each. However the sheet shows a fuel use of 366.36l/ph, when using the actual design screen this engine at this tech, with 0.25 consumption comes in at 91.65l/ph so 183.3l/ph for the two engines?

I am curious though why this sheet seems to think that a total engine output of 2560EP will push a ship of 50k tons to a speed of 8000km/s, even if I forget all about the range I cannot seem to get the design screen to manage anywhere near this speed. This is what makes me wonder if there is an issue with this sheet design or if I have totally misunderstood how to use it correctly?
 

Offline GreatTuna

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Re: Help with engine design
« Reply #9 on: November 23, 2014, 07:34:37 AM »
I get it now.
The sheet has wrong "fuel consumption" formula.
It is

Fuel Consumed/Hour (L) = Engine Power Provided * Number of Engines * Fuel per EPH

The issue here is that Engine Power Provided already includes number of engines and so, overall fuel consumption is drastically increased compared to real consumption if amount of engines is bigger than 1 (2x for 2 engines, 10x for 10 engines, etc.)

And now,
Code: [Select]
5x 50-HS engines with Power Modifier x1, plus 104,18 HS of fuel, totaling 17709 tons of engine and fuel space.It requires two times less space than it required before.

As for the "2560EP instead of 8000EP" issue, I guess it's because the sheet thinks the mass of the ship is 16kton, at least because the optimum is calculated for this mass.
 

Offline Vandermeer

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Re: Help with engine design
« Reply #10 on: November 23, 2014, 08:50:23 AM »
@Rich.h: The sheet there doesn't really seem to work, and is cut out far too simply for such a complex problem anyway. There are too many variables for this to fall into one single linear equation. If you like you can text out this one that I made a couple months ago: http://aurora2.pentarch.org/index.php/topic,7314.0.html
It is more complex and probably difficult to get around at the beginning. However, there is much to consider, so there is really no way to make it much slimmer for a true optimization to happen.
As a quick tutorial, you either put in a total propulsion mass in the field on top left.(..that is the tonnage you plan to dedicate for engine+fuel combined. E.g., if you plan 40% mission components on a 7kt destroyer + 30% crew/armor/engineering, then your propulsion would be 2100kt obviously. tinkering the number a bit up and down, and seeing what happens leads to true optimization though)
If you don't plan so fixed with your propulsion system, and look out for a specific range, then the alternate "engine mass" method mode would work. For that you should leave the top left field empty and instead fill the one to the right of it with what you plan only as engine mass (so no fuel included). You can then look into the range bands at the end of the page to see what amount of fuel would get you how far at the speed you desire. This mode is good to get an overview of which speeds are reasonable at your tech grade, before doing the real math. The calculations down there are heuristic and rushed however, so there is about a 5% error margin in true range. As far as I remember I could not repeat the costly equation from above here 40 times without excel exploding.
playing Aurora as swarm fleet: Zen Nomadic Hive Fantasy
 

Offline Jorgen_CAB

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Re: Help with engine design
« Reply #11 on: January 10, 2018, 05:23:17 PM »
I would like to add one important thing I have looked at and that is the use of very large engines at low to mid tier tech levels.

It actually is far more research efficient to put research into more fuel efficient engines then developing size 50 military engines (especially if above x1 power multiple) at every level.

Size 50 military engines also put more strain on such thing as needing more engineering sections and as a result crew and living space for dealing with the maintenance cycle and supplies to be able to perform battlefield repair on a damaged engine.
« Last Edit: January 10, 2018, 05:25:49 PM by Jorgen_CAB »
 

Offline vorpal+5

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Re: Help with engine design
« Reply #12 on: January 15, 2018, 10:15:10 AM »
Given the meager reduction in fuel usage from size, I only build small or semi small engines, as others said, it costs less RP, less maintenance, the granularity is more practical, etc.

Slow ship: 20% of size for me, fast 40% ...
 

 

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