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VB6 Aurora > Newtonian Aurora
Newtonian Aurora - Rules
Steve Walmsley:
I am going to use this topic to post rules as they are created. This will provide players with an easy reference point. I'll sticky and lock the topic so please post any questions and/or comment in the main threads. I'll try to keep these posts updated as rules change due to ongoing development.
Steve Walmsley:
Engines
The concept of Military Engine, Commercial Engine, Fighter Engine, etc has been removed and Hyper Drives have been removed. The five elements of engine design are now:
Engine Technology: As before, except the base values are different and those values are expressed in Meganewtons of thrust per HS of engine. One Meganewton (MN) is equal to the amount of net force required to accelerate a mass of one ton at a rate of one kilometre per second squared. For example, the Internal Confinement Fusion Drive technology has a rating of 60 Kilonewtons per ton, so an unmodified 250 ton engine (The same size as the standard Aurora military engine) would produce 15 MN of thrust.
Fuel Consumption per MN per Hour: This is similar in concept to the old Fuel Efficiency, although it is now modified by other factors in engine design. Fuel Consumption is critical though and will be far more important than in the past. The initial consumption rate starts at 200 litres per MN per hour and additional technology levels will lower that figure. An Engine is rated in the number of litres of fuel per hour it consumes. This amount is derived from Engine Thrust in MN x Fuel Consumption per MN per Hour. So an Engine with 15 MN of thrust and a Fuel Consumption per MN per Hour of 150 would consume 2250 litres of fuel per hour at full burn.
Engine Size: You can now select the size of engine from 50 tons to 2500 tons. Larger engines are more fuel efficient so fuel consumption is reduced by 1% for every 50 tons of engine. For example, a 500 ton engine reduces fuel consumption by 10% and a 1250 ton engine reduces it by 25%.
Thermal Reduction: As before, this reduces the thermal signature of engines, which is equivalent to 10x thrust in MN.
Thrust / Fuel Consumption Modifiers: There are two new tech lines to research, called Max Engine Thrust Modifier and Min Engine Thrust Modifier. These establish the range within which you can change engine thrust from that provided by the base engine technology. Increasing thrust increases fuel consumption per MN and decreasing thrust can provide significant savings in fuel consumption. Thrust can be increased by up to 300% of normal and decreased to 10% of normal if you have the prerequisite techs. The dropdown on the design window will have options from the minimum possible to the maximum possible in 5% increments. So 40%, 45%, 50%, 55% ...... 180%, 185%, etc. Each engine thrust modifier percentage is accompanied by a fuel consumption modifier, based on the formula Fuel Consumption Modifier = (4 ^ Engine Thrust Modifier) / 4.
For example, assume you choose to increase Engine Thrust to 50% greater than normal. The Fuel Consumption would be (4 ^ 1.5)/4 = 2, so for a thrust increase of 50%, the fuel consumption per MN would increase by 100%. Bear in mind that if the engine thrust has increased by 50% and the fuel consumption per MN has increased by 100%, then the overall fuel consumption for the engine is 3x higher than before. This is shown on the dropdown as "Engine Thrust +50%. Fuel Consumption per MN +100%".
If you had an engine with Engine Thrust +100%. Fuel Consumption per MN +300%, you would have something similar to the FAC engine in Aurora, except now you can have different size engines and you can have more than one per ship.
Here is the design summary for an engine of 250 tons (5 HS in Standard Aurora), using Magneto-plasma Drive technology, with a 25% increase in thrust and no thermal reduction.
Magneto-plasma Drive
Thrust: 12.5 MN Base Fuel Consumption per MN: 188.1 litres per hour
Base Acceleration: 50 mp/s (5.1G)
Fuel Use at Full Burn: 2351 litres per hour
Engine Size: 250 Tons Engine HTK: 2
Thermal Signature: 125 Exp Chance: 12
Cost: 62.5 Crew: 8
Materials Required: 15.625x Duranium 46.875x Gallicite
Development Cost for Project: 625RP
Because of the thrust modifier the fuel consumption per MN is increased by 41% and due to the size of the engine the fuel consumption per MN is decreased by 5%.
The Fuel Consumption per MN per Hour is calculated as the base racial technology of 140 litres per hour, x0.95 for engine size, x1.4142 for the 25% engine thrust modifier, which equals 188.1. Fuel use in litres per hour is therefore 12.5 MN x 188.1 = 2351. As that single engine alone would use up a 50 ton (1 HS in standard Aurora) fuel tank in a little over 21 hours, you can already see that fuel tanks are going to be a lot bigger in Newtonian Aurora.
The base acceleration is for the engine accelerating itself with no accounting for where the fuel is coming from. While this is obviously never achievable in practice, it provides a way to rate engines against each other. 50 mp/s is an acceleration of fifty meters per second squared. The 5.1G is the force a passenger on the engine would feel. This subject is covered more realistically in the ship design section. Explosion Chance is based on 10% of the engine thrust percentage, rounded down.
Now lets look at an engine designed with fuel consumption as a priority. This is an engine of 1250 tons (25 HS in Standard Aurora), using Magneto-plasma technology, with an 80% decrease in thrust and no thermal reduction.
Commercial Magneto-plasma Drive
Thrust: 10 MN Base Fuel Consumption per MN: 34.6 litres per hour
Base Acceleration: 8 mp/s (0.82G)
Fuel Use at Full Burn: 346 litres per hour
Engine Size: 1250 Tons Engine HTK: 12
Thermal Signature: 100 Exp Chance: 2
Cost: 50 Crew: 1
Materials Required: 12.5x Duranium 37.5x Gallicite
Development Cost for Project: 500RP
The Fuel Consumption per MN per Hour is calculated as the base racial technology of 140 litres per hour, x0.75 for engine size, x0.3299 for the -80% engine thrust modifier, which equals 34.6. Fuel use in litres per hour is therefore 10 MN x 34.6 = 346. So while this engine produces eighty percent of the thrust of the previous engine, the total fuel consumption is eighty-five percent less. However, it is five times larger so the base acceleration is much lower. Even so, you will actually get more Delta-V for the same fuel from this engine than the one above - it will just take longer to do it. More on Delta-V in the ship design section.
Note that there is no detail on exhaust velocity in the engine design. This is a key element in the design of real rocket engines. It has a huge effect on fuel efficiency and will affect the acceleration provided by the engine once the speed of the rocket approaches that of the engine's exhaust velocity. However, I have to draw a line somewhere between realism and fun and in the case of exhaust velocity I decided that having a simpler fuel consumption rating for the engine that could easily be understood by players would be preferable to players having to understand Tsiolkovsky's rocket equation and associated material. I think the current mechanics of engine design allow for a lot of freedom, and provide the players with the feel of a Newtonian game without having to get into serious math.
(http://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation)
Steve
Steve Walmsley:
Missile Engines
The four elements of missile engine design are described below.
Engine Technology: Exactly as ship-based engines. However, the base value of thrust is doubled on the basis that missile engines have no radiation shielding or maintenance access requirements. Thrust is rated in Meganewtons. For example, the Magneto-plasma Drive has a rating of 40 KN per Ton, so a missile engine of 1 ton would provide 40 KN x 2 (missile thrust modifier) or 0.08 MN.
Engine Size: Missile engines can be from 0.1 tons to 5 tons in 0.1 ton increments.
Fuel Consumption per MN per Hour: As with ship engines, the fuel consumption of a missile engine is based on Engine Thrust in MN x Fuel Consumption per MN per Hour. So an Engine with 0.08 MN of thrust and a Fuel Consumption per MN per Hour of 150 would consume 12 litres of fuel per hour at full burn.
Thrust / Fuel Consumption Modifiers: Sorium-based missile engines use the same principle as ship engines and use the same tech lines (Max Engine Thrust Modifier and Min Engine Thrust Modifier). However, the upper end of the range is doubled for missile engines. So if the Max Engine Thrust tech is 175%, missile engines can use up to 350%, again with the rationale that these are designed for single use, unmanned craft and therefore have significantly different engineering requirements. As with ship-based engines, increasing thrust has a significant effect on fuel efficiency and decreasing thrust can provide huge savings in fuel efficiency. As the missile modifier is double that of ships, thrust can be increased by up to 600% of normal and decreased to 10% of normal if you have the prerequisite techs. The dropdown on the design window has options from the minimum possible to the maximum possible in 5% increments. So 40%, 45%, 50%, 55% ...... 180%, 185%, etc. Each engine thrust modifier percentage is accompanied by a fuel consumption modifier, based on the formula Fuel Efficiency Modifier = (4 ^ Engine Thrust Modifier) / 4. So a missile with a +200% engine thrust modifier would have a +1500% fuel consumption modifier.
Unlike ship engines, you have the option to use chemical-based rocket engine technology. In this case, the chemical-based technology has its own fuel consumption which is not modified by the Racial base fuel consumption or the Engine Thrust / Fuel Consumption modifier. The engine thrust of chemical technology cannot be modified either. Available as starting technologies are the LOX/LH2 Rocket Engine, which has a fuel consumption of 800,000 and a base engine thrust of 700 KN per ton, and the LOX/RP-1 Rocket Engine which has a fuel consumption of 1,100,000 and a base engine thrust of 900 KN per ton (including the x2 thrust modifier for missiles). There is also an Advanced LPX/RP-1 Engine with a thrust of 1400 KN which can be developed. Actually this was developed by the Soviet Union as the NK-33 but the US didn't develop equivalent tech. In a multi-nation start this could be SM-assigned to Russia. As you can imagine, Chemical engines need a LOT of fuel. Those figures are based on converting modern day rocket engines to Aurora fuel efficiencies and demonstrate how incredibly fuel efficient Sorium-based engines are.
As I have figured out how to convert modern-day rockets in Aurora numbers, there is an option to enter modern-day rocket engines into Aurora and use them as part of missile design. You have to enter name, thrust in Meganewtons, mass of the engine and specific impulse (Isp). Aurora uses the specific impulse to derive the fuel efficiency, which is 367,099,200 / Isp. That number is derived from the formula to convert Isp into thrust-specific fuel consumption (TSFC), which is 101972/Isp. TFSC is used today to calculate fuel consumption per unit of thrust. This is nominally grams per Kilonewton second, but is equally correct for kilograms per Meganewton second or litres per Meganewton second. As Newtonian Aurora hourly fuel consumption is based on engine thrust (in Meganewtons) x fuel consumption, then TFSC multiplied by 3600 is equal to Aurora fuel consumption. Converting in the opposite direction means that (101972 x 3600)/ISP = Aurora fuel consumption.
For example, if you enter the Space Shuttle Main Engine (SSME), which has thrust of 2.18 MN, mass of 3.177 tons and Isp of 453 in vacuum, Aurora uses the name, mass and thrust directly and converts the Isp into a fuel efficiency of 810,373.7. Using that SSME in a missile design shows a fuel consumption rate of 490.73 litres per second. The TFSC of the real SSME is 225, which multipled by the 2.18 MN thrust equal a consumption of 490.73 litres per second. So you can use real rocket engines with real rates of fuel consumption. Of course this is still massively simplified from real world considerations but it will provide the right flavour for the game. It also will be hard to achieve anything major with modern day engine technology but you can try :). As the fuel for chemical rockets will be far more accessible than Sorium, it will be considered to be easily made by ordnance factories and not tracked in terms of cost or storage. Obviously once it is in the missile, the chemical fuel will be tracked.
Anyway back to Sorium-based engines. Here are four two ton missile engine designs using Magneto-plasma engine technology and a base fuel consumption of 140. The first uses Engine Thrust Modifier x1, Fuel Modifier x1.
Fuel Efficient 160 KN Missile Engine
Thrust: 0.16 MN Base Fuel Consumption per MN: 140 litres per hour
Base Acceleration: 80 mp/s (8.16G) Per Min: 4.8 km/s Per Hour: 288 km/s
Fuel Use at Full Burn: 22.4 litres per hour
Engine Mass: 2 tons Cost: 0.8 Thermal Signature: 1.6
Materials Required: 0.2x Tritanium 0.6x Gallicite
Development Cost for Project: 80RP
Note that while this is more powerful in terms of thrust-weight ratio than a ship-based engine and doesn't use much fuel. It would take an hour to accelerate itself to 288 km/s and that assumes no fuel mass. Shown below are three designs using engine thrust modifiers of x2, x3 and x3.5 respectively. (3.5x requires the max engine boost 175% tech, which is 8000 RP). Note the acceleration rate increases but the fuel consumption goes up very quickly indeed.
320 KN Missile Engine
Thrust: 0.32 MN Base Fuel Consumption per MN: 560 litres per hour
Base Acceleration: 160 mp/s (16.32G) Per Min: 9.6 km/s Per Hour: 576 km/s
Fuel Use at Full Burn: 179.2 litres per hour
Engine Mass: 2 tons Cost: 1.6 Thermal Signature: 3.2
Materials Required: 0.4x Tritanium 1.2x Gallicite
Development Cost for Project: 160RP
480 KN Missile Engine
Thrust: 0.48 MN Base Fuel Consumption per MN: 2240 litres per hour
Base Acceleration: 240 mp/s (24.47G) Per Min: 14.4 km/s Per Hour: 864 km/s
Fuel Use at Full Burn: 1075.2 litres per hour
Engine Mass: 2 tons Cost: 2.4 Thermal Signature: 4.8
Materials Required: 0.6x Tritanium 1.8x Gallicite
Development Cost for Project: 240RP
560 KN Missile Engine
Thrust: 0.56 MN Base Fuel Consumption per MN: 4480 litres per hour
Base Acceleration: 280 mp/s (28.55G) Per Min: 16.8 km/s Per Hour: 1008 km/s
Fuel Use at Full Burn: 2508.8 litres per hour
Engine Mass: 2 tons Cost: 2.8 Thermal Signature: 5.6
Materials Required: 0.7x Tritanium 2.1x Gallicite
Development Cost for Project: 280RP
Finally, here is a 2 ton LOX/LH2 rocket engine, similar in technology to the space shuttle main engine - note the fuel use is shown per minute, not per hour. Also bear in mind all the acceleration figures are for the engine alone with no fuel mass and no payload.
1400 KN Missile Engine
Thrust: 1.4 MN Base Fuel Consumption per MN: 800,000 litres per hour
Base Acceleration: 700 mp/s (71G) Per Min: 42 km/s Per Hour: 2,520 km/s
Fuel Use at Full Burn: 18,667 litres per minute
Engine Mass: 2 tons Cost: 0.7 Thermal Signature: 14
Materials Required: 0.175x Tritanium 0.525x Gallicite
Development Cost for Project: 70RP
As you can see from the above designs, once you add fuel and payload, getting a missile up to an appreciable speed is going to take some time and there would be little point firing missiles at a fast moving ship if the missiles can't even match its speed for several hours. On the other hand, missiles fired from three or four billion kilometres away will be going pretty fast when they reach their target. Also bear in mind that missiles will be able to switch off the engines mid-flight once they reach a pre-designated speed and use any remaining fuel for course corrections so they have an effectively unlimited range - just as they would in reality. Finally, the missile is going to have an initial speed and heading equal to that of the launching ship so firing at pursuers is going to be tricky. Missile combat is going to require a lot of planning and will depend a lot more on targeting and course correction than missile range.
Steve
Steve Walmsley:
FTL Drive
FTL Drive Efficiency: This serves the same function as jump drive efficiency, except it starts at efficiency 4 rather than 3 and each level is half the cost in research terms. For example, efficiency 6 is 8000 RP instead of 15,000 RP. In Newtonian Aurora you won't be able to use a gate to get between systems so non-FTL-capable ships can only be moved between systems via squadron jump or in hangar bays. Therefore FTL drives will probably be a lot more common than jump drives in standard Aurora.
Max FTL Squadron Size: The same as standard Aurora, except that squadrons will travel through hyperspace together rather than through jump points. There will only be squadron jumps as there are no jump points to hold open. Creating drives that can jump multiple ships is easier though as the base drive can handle four ships and the research costs are half as much as before.
Hyperspace Dimension: The hyperspace dimension through which the ship or squadron will travel. Higher dimensions bring real space locations closer together and increase effective speed. Each dimension is rated for the speed multiplier it provides. The Alpha Dimension is 2500x speed, the Beta Dimension is 5000x, Gamma is 7500x, etc.
Base Size: The base size of the FTL drive. This is comparable to the size of a military jump drive in standard Aurora, although there is no distinction between military and commercial drives in Newtonian Aurora. Unlike Standard Aurora, larger drives are less expensive in terms of build points per ton.
The cost of an FTL Drive is equal to (Sqrt(FTL Drive Size) * Sqrt(FTL Speed Multiplier) * Sqrt(FTL Squadron Size)) / 50
FTL Travel
Travel between different star systems is only possible using an FTL drive (although you never know - sub-light generation ships might make an appearance at some point). Stars have a hyper limit, inside which it is not possible to activate an FTL drive. This limit is equal to primary star mass squared, multiplied by three billion kilometres. For Sol, this is about the orbit of Uranus. In order to reach another star system, the FTL-capable ship or fleet has to align itself with the destination system. This can be done using the new "FTL Align and Jump" order. Until the ship is on an exact course for the destination it will be unable to jump. Aurora will automatically make course corrections (using any available DeltaV) in order to align while this order is in effect. You will are able to optionally specify a minimum jump speed so the ship will not enter FTL until it reaches the desired speed. Otherwise, the minimum jump speed is 200 km/s.
At this point, you will lose contact with the ship and be unable to communicate until it reaches its destination system, which may be a period of weeks or months. If a full gravitational survey of the destination has been carried out, the ship will arrive with approximately the same speed at which it entered hyperspace, on a bearing from the primary within six degrees of the direct course from the start system and at a range from the primary between 100% and 110% of the hyper limit radius. If the destination system has not been surveyed at all, the location of arrival could be anywhere in a toroid, between 100% and 170% of the hyper limit distance, on any bearing from the star. The heading of the ship will still be directly away from the start system so you could end up on a course perpendicular to your destination, or even beyond it and heading away. A partial survey of the destination will result in a scenario somewhere between the two extremes. A lack of survey information could also result in the ship arriving slower or faster than expected, although within 30% of departure speed, and correspondingly earlier or later than expected. Because the ship is out of contact, you will be unable to determine the likely arrival point ahead of its arrival.
This uncertainty will make assaults on unsurveyed systems 'interesting' to manage. As well as the obvious issue of coordinating multiple squadrons, it will be a lot harder to pull out of an assault if things are not going well. To return to their starting system, ships will have to slow to zero and then begin accelerating along a reciprocal course. Another option may be to escape to another system that is on an easier escape course, fuel permitting. One other result of the above is that there will be far more 'spreading out' of civilian traffic rather than the current situation where ships tend to travel in large groups.
The speed at which interstellar travel takes places is equal to the speed at which you enter hyperspace multiplied by the speed multiplier of the FTL Drive. For example, if a ship using an FTL drive with a 10,000x speed multiplier entered hyper at 1600 km/s, its effective speed would be 10,000 x 1600 km/s, which is about 53x light speed. A journey to Alpha Centauri would therefore take about a month and a journey of ten light years would require about ten weeks. Ships cannot accelerate or decelerate within hyperspace so the decision is whether to expend fuel and time to reach a high speed before entering hyperspace, or to enter at lower speed, saving fuel but extending journey time.
A few examples, using generally level 4 tech, which is FTL Drive Efficiency 8, Minimum Drive Size 500 tons, Speed Multiplier 10,000 and Squadron Sizes up to 7. The crew requirement is based on sqrt(Size)
Survey Ship Drive
Max Ship Size: 4,000 tons Max Squadron Size: 4 FTL Speed Multiplier: 10,000x
Jump Engine Size: 500 tons Efficiency: 8 Jump Engine HTK: 2
Cost: 89 Crew: 22
Materials Required: 17.8x Duranium 71.2x Sorium
Development Cost for Project: 890RP
Destroyer Drive
Max Ship Size: 8,000 tons Max Squadron Size: 4 FTL Speed Multiplier: 10,000x
Jump Engine Size: 1,000 tons Efficiency: 8 Jump Engine HTK: 4
Cost: 126 Crew: 32
Materials Required: 25.2x Duranium 100.8x Sorium
Development Cost for Project: 1260RP
The next two examples are the same size drive but with squadron sizes of four and seven respectively
Cruiser Drive
Max Ship Size: 16,000 tons Max Squadron Size: 4 FTL Speed Multiplier: 10,000x
Jump Engine Size: 2,000 tons Efficiency: 8 Jump Engine HTK: 8
Cost: 179 Crew: 45
Materials Required: 35.8x Duranium 143.2x Sorium
Development Cost for Project: 1790RP
Command Cruiser Drive
Max Ship Size: 16,000 tons Max Squadron Size: 7 FTL Speed Multiplier: 10,000x
Jump Engine Size: 2,600 tons Efficiency: 8 Jump Engine HTK: 10
Cost: 270 Crew: 51
Materials Required: 54x Duranium 216x Sorium
Development Cost for Project: 2700RP
Next is a drive for a colony ship plus the same size drive with the minimum speed multiplier. The latter would probably only be worth it for journeys that involved relatively long in-system time and short FTL trips.
Colony Ship Drive
Max Ship Size: 20,000 tons Max Squadron Size: 4 FTL Speed Multiplier: 10,000x
Jump Engine Size: 2,500 tons Efficiency: 8 Jump Engine HTK: 10
Cost: 200 Crew: 50
Materials Required: 40x Duranium 160x Sorium
Development Cost for Project: 2000RP
Slow Colony Ship Drive
Max Ship Size: 20,000 tons Max Squadron Size: 4 FTL Speed Multiplier: 2,500x
Jump Engine Size: 2,500 tons Efficiency: 8 Jump Engine HTK: 10
Cost: 100 Crew: 50
Materials Required: 20x Duranium 80x Sorium
Development Cost for Project: 1000RP
Now progressively larger drives.
Battleship or Freighter Drive
Max Ship Size: 40,000 tons Max Squadron Size: 4 FTL Speed Multiplier: 10,000x
Jump Engine Size: 5,000 tons Efficiency: 8 Jump Engine HTK: 20
Cost: 283 Crew: 71
Materials Required: 56.6x Duranium 226.4x Sorium
Development Cost for Project: 2830RP
Large Freighter Drive
Max Ship Size: 80,000 tons Max Squadron Size: 4 FTL Speed Multiplier: 10,000x
Jump Engine Size: 10,000 tons Efficiency: 8 Jump Engine HTK: 40
Cost: 400 Crew: 100
Materials Required: 80x Duranium 320x Sorium
Development Cost for Project: 4000RP
Huge Freighter Drive
Max Ship Size: 160,000 tons Max Squadron Size: 4 FTL Speed Multiplier: 10,000x
Jump Engine Size: 20,000 tons Efficiency: 8 Jump Engine HTK: 80
Cost: 566 Crew: 141
Materials Required: 113.2x Duranium 452.8x Sorium
Development Cost for Project: 5660RP
The wat in which the cost of FTL drives is calculated will support the concept that really large freighters and colony ships will be more economical, whereas in Standard Aurora the advantage of building ultra-large commercial ships isn't very great. Commercial ships will generally become more expensive but this is a very different game with longer timescales for the building up of distant colonies so I don't think that is a significant problem.
Steve
Steve Walmsley:
Railguns
Railgun Maximum MJ Per Ton: The muzzle energy in Megajoules (MJ) of the railgun is based on its size in tons (not HS as I am moving away from HS in Newtonian Aurora) multiplied by this number. So a 200 ton railgun with an MJ per Ton of 12, would have a muzzle energy of 2400 MJ. Damage in Newtonian Aurora will be calculated based on the MJ output of a weapon. For comparison, the recently tested US Navy railgun has a muzzle energy of 33 MJ. This is a tech line starting at 5 MJ per ton.
Railgun Energy Conversion Rate: The efficiency with which the railgun transfers energy stored in homopolar generators (HPG). If this was 35% for example, the 2400 MJ railgun would require 6857 MJ of energy to fire. This is a tech line starting at 25%
Railgun vs. Projectile Maximum Mass Ratio: This is the ratio of the total railgun mass compared to the mass of the projectile. The kinetic energy of each shot is based on the muzzle velocity squared multiplied by half the mass of the projectile (real physics - not my formula). This means that greater velocity is more important than larger projectiles. Also, greater velocity makes fire control easier. So, the question becomes why not spend your muzzle energy on smaller, faster projectiles? Because with a smaller 'calibre' the actual rails become longer and narrower and there is a limit to the aspect ratio between 'calibre' and rail length. As Aurora doesn't really consider how 'long' something is, that design consideration is handled by this parameter. You can exceed the mass ratio if you wish (and therefore increase muzzle velocity) but your energy conversion rate is reduced by maximum mass ratio/actual mass ratio. I'll show an example of this later on. This tech line starts at a mass ratio of 100,000, which is a 1 kg projectile for a 100 ton railgun.
Railgun Heat Dissipation Rate: When a railgun fires, it generates a huge amount of heat. The parameter covers how rapidly the railgun cools down to the point at which another shot can be fired. It is based on the surface area of the railgun, which is based on its mass. The value of the parameter is how much MJ/s per square meter will be dissipated per second (assuming 1 ton = 1 cubic metre). Smaller railguns will have a greater surface area vs volume than larger railguns so they will cooldown a little faster. For example, if this parameter was 0.6 MJ/s and the railgun was 200 tons and 2400 MJ, the surface area would be 165.4, the dissipation rate would be 99.24 MJ per second and the total cooldown period would be 2400/99.24 = 24.18 seconds, rounded to 24 seconds. You can increase rate of fire by either researching this tech line, or you can also reduce the MJ per Ton parameter to create a less powerful but faster firing railgun. For example, changing it from 12 to 5, would create a 1000 MJ railgun that fired every 10 seconds (albeit at about 2/3rds of the muzzle velocity).
Railgun Size: The size of the railgun in tons
Projectile Mass in Kilograms: The size of the projectile, starting at 1 kilogram with 0.1 kg increments to 5 kg and then 0.5 kg increments. When you hit the mass ratio limit described above, if you wish to create a more powerful railgun while retaining as much energy efficiency as you can, then increasing the size of the projectile becomes the best option. However, if muzzle velocity is deemed more important than energy efficiency then increasing mass ratio would be more effective. The following examples assume MJ per Ton of 12, a 200k mass ratio, a conversion rate of 35% and a heat dissipation rate of 0.6 MJ per m2.
Below is a 200 ton railgun with a 1 kg projectile. This makes full use of the maximum mass ratio of 200k. Note that Vendarite is now the required material for kinetic energy weapons (also, the existing research field of missiles and kinetic weapons has been split into two separate fields). The railgun has a Muzzle Velocity of 69,282 m/s (69.3 km/s), which is the maximum that can be achieved with the available technology without sacrificing energy efficiency. While this doesn't seem to be a very high velocity compared to standard Aurora, bear in mind most ships at a similar tech level would require several hours of acceleration to reach this speed from a standing start and if they are moving faster, their own speed may (depending on the ship's heading) increase the relative speed of the projectile and increase its damage.
2400 MJ Railgun
Muzzle Energy: 2400 MJ Muzzle Velocity 69,282 m/s Cooldown Period: 24 seconds
Power Requirement per shot: 6,857 MJ Energy Efficiency: 35%
Mass Ratio: 200k Energy Efficiency Penalty: 0%
Railgun Size: 200 tons Surface Area: 165.4 Projectile Mass: 1 kg
Cost: 24 Crew: 20 HTK: 2
Materials Required: 24x Vendarite
Development Cost for Project: 240RP
Now lets look at two options for doubling the size of the railgun to 400 tons. The first has the same 1kg projectile size and the second has a 2kg projectile. Both will inflict the same damage and both take 30 seconds to cooldown, because their surface area to volume ratio has decreased. The former has increased the muzzle velocity to almost 100 km/s but at the expense of reducing energy efficiency to 17.5% and therefore requiring 27,429 MJ per shot. The second has the same 70 km/s muzzle velocity as the 200 ton version and requires 13,714 MJ per shot. BTW, you may be thinking why bother with a 400 ton 4800 MJ railgun and instead have two 200 ton 2400 MJ railguns. I'll explain that when I describe the new shield generators.
4800 MJ Railgun - 1kg
Muzzle Energy: 4800 MJ Muzzle Velocity 97,979 m/s Cooldown Period: 30 seconds
Power Requirement per shot: 27,429 MJ Energy Efficiency: 17.5%
Mass Ratio: 400k Energy Efficiency Penalty: 100%
Railgun Size: 400 tons Surface Area: 262.5 Projectile Mass: 1 kg
Cost: 48 Crew: 40 HTK: 4
Materials Required: 48x Vendarite
Development Cost for Project: 480RP
4800 MJ Railgun - 2kg
Muzzle Energy: 4800 MJ Muzzle Velocity 69,282 m/s Cooldown Period: 30 seconds
Power Requirement per shot: 13,714 MJ Energy Efficiency: 35%
Mass Ratio: 200k Energy Efficiency Penalty: 0%
Railgun Size: 400 tons Surface Area: 262.5 Projectile Mass: 2 kg
Cost: 48 Crew: 40 HTK: 4
Materials Required: 48x Vendarite
Development Cost for Project: 480RP
Here is a third option using a 1.5kg projectile, which is a compromise between the other two. Bear in mind these are just the options for two different sizes at one tech level. You will be able to create a lot of different designs, of different sizes, even at just one technology level. With multiple tech lines involved, there are many possibilities for railgun design.
4800 MJ Railgun - 1.5kg
Muzzle Energy: 4800 MJ Muzzle Velocity 80,000 m/s Cooldown Period: 30 seconds
Power Requirement per shot: 18,240 MJ Energy Efficiency: 26.32%
Mass Ratio: 266k Energy Efficiency Penalty: 33%
Railgun Size: 400 tons Surface Area: 262.5 Projectile Mass: 1.5 kg
Cost: 48 Crew: 40 HTK: 4
Materials Required: 48x Vendarite
Development Cost for Project: 480RP
Fire control for railguns isn't finalised yet but I will likely be tracking each projectile as if it were a missile with no manoeuvring ability and checking if it intersects the same space as the target (or anything else that gets in the way) at the same time.
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