Capital Class Ships - How many Engines do they need?

Discussion in 'General Discussion' started by KNIGHTOF #DRAMA, Aug 27, 2016.

  1. KNIGHTOF #DRAMA

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    So a friend and I spent the last two days making our own dream capital ship, the thing is pretty massive, it has 8332 blocks with a total weight of 32.2kt. We removed all thrusters except the rear ones and have been stacking more and more of them on the rear, we started at about 8.9m/s and are now going about 15m/s.

    This is what the ship currently looks like:
    [​IMG]

    http://steamcommunity.com/sharedfiles/filedetails/?id=752705128

    Empyrion - Galactic Survival
    A Screenshot of Empyrion - Galactic Survival
    By: KNIGHTOF #DRAMA



    We have plenty of RCS's, can easily manuever the ship around, but can't seem to get any real forward momentum going, is there something we're missing, or do we need to just keep adding thrusters thanks to the weight (With the best thruster in the game adding about 0.3 m/s per thruster).
     
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  2. mid endian

    mid endian Commander

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    to help give yourselves an estimate, take a blueprint of your current CV and drop it into a creative map, then do some testing with thrust for power and hovering on planets. that should help you in the server you're on.
     
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  3. Frigidman

    Frigidman Rear Admiral

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    32 kt ? That it???

    With that image, and how many large and normal thrusters you have, that thing should be hitting top speed in 1 second. Maybe you have too many thrusters and its warping time backwards and going in reverse?
     
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  4. Slam Jones

    Slam Jones Rear Admiral

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    That's your problem right there. Unless you have thrusters for every direction, your CV will act quite oddly.
     
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  5. KNIGHTOF #DRAMA

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    The problem actually turned out to be that the starter block was facing the wrong way, so I had to rebuild the entire thing from scratch. Even changing the direction of the block after it has been set down didn't do anything, hopefully the developers add a proper way to change craft facing after the starter block has been placed in the future, to avoid this happening.
     
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  6. Booyaah

    Booyaah Captain

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    Yeah always pay attention to the direction the nose of the ship is facing on the map before you start arbitrarily decide which end to make front and back. However I srsly wish they would add something like a symmetry plane for a ship's directional orientation where you could explicitly tell it which plane is front/back etc. I had a 'sideways' facing ship I think the first time I built one.
     
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  7. Frigidman

    Frigidman Rear Admiral

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    I think every builder here has gone through this trial and tribulation.

    Congrats, you are now part of the gang!
     
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  8. medicineman

    medicineman Captain

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    This is an old bug. It really should be noted in the start block descriptions at this point.
     
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  9. sloejack

    sloejack Ensign

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    Glad to hear you figured out the backwards starter block thing, though to add to your original question of "how many engines do I need" there is a formula that generally works in Empyrion for determining the # of thusters you need at a given facing though it does require some dynamic adjustments for every engine you add since you are also adding weight.

    Lets say you want an acceleration of 10 with a 1000 ton (t) CV. To solve for the amount of Force required to move the Mass of your ship at an acceleration of 10.

    ex. 10 = F / 1000t

    To move a 10 ton CV with an acceleration of 10, you would need a Force of 10,000kN (10MN) by that example.

    ASSUMPTIONS:
    Empyrion Acceleration math seems to assume a gravity of 1.0 in space and planet gravity when operating planet side.
    Force for CV engines is displayed in MN (Mega Newtons [1MN = 1000kN])

    In the real world the formula to determine thrust is represented T = F / (M *G) [Thrust, Force, Mass, Gravity]

    To determine what is needed to achieve a specific acceleration we can simplify that into the following formula assuming gravity = 1.0:
    Target Acceleration * t = kN required

    Lets take a couple of examples to finish fleshing this out in case you're still not sure how to answer the question.
    Lets say we have a barebones CV,
    Barebones CV (CV Core, T1 Fuel Tank, T1 RCS, T1 Large Generator, and a Cockpit) = 107t

    A Directional Thruster weighs 16t (It says it only weighs 2t when you examine it in the control panel but it lies, CV thrusters weigh 8x more than shown) and has a force of 8MN. Adding one of these to the bare bones CV brings the total weight to 123t. 8MN == 8000 kN and so our calculation looks like this:

    Acceleration = 8000 / 123 = 65 (65.04 but the display doesn't share fractions).
    So on our bare bones CV this gives us an acceleration of 65 (in one direction).

    Let's say I add 6 directional thrusters to our barebones CV one for each direction of movement. The engines alone weigh 96t (16t * 6) and the rest of our craft is 107t giving us a grand total of 203t. So for a given direction I have 8000kN of force / 203t and so my acceleration dropped to 39 m/s^2 just from adding the additional 5 engines.

    If I wanted to maintain my acceleration of 65 in ALL directions I would have to add a lot more engines because now it's an weight and force arms race.

    In this case I am guessing (a somewhat educated guess) that I would need to add 4 directional thrusters to each facing (24 thrusters * 16t = 384t) with would make my CV weigh 491t total (384t + 107t).
    The force of 4 directional thrusters on a side is 32MN or 32000kN.

    Acceleration = 32000 / 491 = 65 (65.17)

    But no one wants to fly a bare bones CV around and we want to try and answer your question from before, about how many engines you would need.

    You never actually said how fast you wanted it to be able accelerate in a given direction but I'll give you some ideas around the amount of force required to move that much tonnage around and you can figure it out for yourself based in what you actually want.

    Some Assumptions:
    You're CV weighs 32,200t without thrusters.

    Here are some baseline numbers for Force and Weight of CV engines:
    Directional Thruster - 8MN, 16t
    Normal Thruster - 20MN, 24t
    Armored Thruster - 15MN, 40t
    Slanted Thruster - 18MN, 32t
    Large Thruster - 200MN, 176t
    XL Thruster - 800MN, 600t1

    If I want to accelerate a 32200t CV at a rate of 1 m/s^2 then I need a force of 32,200kN or 32.2MN
    4 Directional Thrusters would give me 32MN of force which is pretty close, but remember they would also add 64t of weight which would bring my CV up to a 32264t weight. At this point though an additional 64t of weight doesn't mean much and so an acceleration of .99 will still like register as a 1 m/s^2. However, if I want to move 1 m/s^2 in all directions now we're talking about adding 384t and now our CV weights 32584t which gives us an acceleration of .98 which may still be enough to display 1 m/s^2 with rounding.

    Since an acceleration of 1 m/s^2 makes angels weep lets try something more realistic like an acceleration of 10 at least.

    10 * 32200 = 322000kN (322MN) for one facing. So, on sheer CV weight alone 2 Large Thrusters more than gets it done for one facing.
    Add an additiona 352t of weight for two large thrusters and now we're looking at 32552t. The 400MN Force / 32552t = an acceleration of 12.28. But again that's just for one facing... if I want to be able to move at least 10 m/s^2 in all directions I think we can stick with 2 large thrusters at each facing which takes the 352t * 6 and puts us at 2112t + 32200t from the cv for a total weight of 34312t.

    10 * 34312 = 343,120 which is < the 400,000 force being produced by our engines and so with an 11.65 acceleration we've hit our goal. Since the equivalent Normal Thrusters (200MN) would weight 240t instead of 176 you might be able to shed some weight and go 1L + some combonation of Normal thrusters (7 or 8 per side) to achieve 10m/s^2 but if I'm not trying for something asthetic I'd rather be flying than figure that out.

    To the EXTREME:
    If you wanted to do something ridiculous like an acceleration of 100 m/s^2 on each facing you would need something akin to 3,220,000kN or 3220MN just to move the CV. With 4 XL Thrusters that would give a Force of 3200MN add a weight of 2400t for a total tonnage of 34600 which is a little heavy to achieve 100m/s^2 in just one direction. If you added 2 Lrg Thrusters for 352t of weigh to gain 400MN of Force you would have 3600MN force for 34952t of weight. 3600000 / 34952 = 103 in one direction. Now you're really moving.

    Remember that the fastest achievable acceleration in space is 100 m/s^2. To get 100 m/s^2 on all directions the math gets a little hard because it's not like you can just do the same thing on each side (4XL Thrusters on each sides come up short with the weight change). 7 XL Thrusters on each side almost gets you there. 32200 base weight plus 25200 thruster weight gives you 57400t being pushed by 5600MN.

    We're going to need a little more so if add 2 Lrg Thrusters to each side that gives us an additional 2112t of weight in exchange for an additional 400MN of force on a given facing. So now we're pushing 59512t of CV with 6000MN of force. We've hit our magic number with 6000000 / 59512 = 100.8m/s^2.

    Not sure if this was helpful or just mental drivel but have fun flying in either case. :)
     
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  10. Jazz Eon

    Jazz Eon Ensign

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    I did this - here is a Fix that works to change the way the ship faces...
     
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  11. ravien_ff

    ravien_ff Rear Admiral

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    This thread is 3 years old, though the solution does work. :D
     
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