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Offline Steve Walmsley

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Newtonian Aurora
« on: August 29, 2011, 09:00:45 AM »
I know I have been absent for a couple of weeks. Partially work-related but partially because I have been playing around with a variant of Aurora, which I will probably call Aurora FTL. This isn't a change to the main game, but an optional alternative that should be available in a few months, spare time permitting. The two major differences will be a Newtonian flight model and FTL instead of jump points. The latter is partially forced by the former because speeding up and slowing down at each jump point on long journeys would use so much fuel it would render it unplayable. I am working on the Newtonian element at the moment, which is a huge change to many parts of Aurora, and then I will move on to the new universe model. This is really an experiment because I am still not convinced that a newtonian game is playable but it's something I thought about many times and it has been suggested on here a lot. I decided that I may as well give it a go because if I don't I will always wonder if it was possible :). As a taster of the final game, here is a summary of the current changes to engine design and ship design in Aurora FTL.

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 has a rating of 2 MN per HS, so an unmodified size 5 engine would produce 10 MN of thrust.

Base Fuel Efficiency: This is similar to the old Fuel Efficiency, although it is now modified by other factors in engine design. The Base Fuel Efficiency is critical though and will be more important than in the past. It starts at 20 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 Power x Fuel Efficiency. So an Engine with 10 power and a fuel efficiency of 12 would consume 120 litres of fuel per hour at full burn.

Engine Size: You can now select the size of engine from 1 HS to 50 HS. Larger engines are more fuel efficient so Fuel Efficiency is modified by 1 - (EngineHS / 100). In simpler terms, each HS of engine reduces fuel efficiency by 1%, so a size 10 engine reduces Base Fuel Efficiency by 10% and a size 25 engine reduces it by 25%.

Thermal Reduction: As before, this reduces the thermal signature of engines, which is equivalent to 10x thrust in MN.

Engine Power / Fuel Efficiency Modifiers: There are two new tech lines to research, called Max Engine Power Modifier and Min Engine Power Modifier. These establish the range within which you can change engine thrust from that provided by the base engine technology. Increasing thrust has a significant effect on fuel efficiency and decreasing thrust can provide huge savings in fuel efficiency. Power can be increased by up to 300% of normal and decreased to 10% of normal if you have the prerequsite 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 power modifier percentage is accompanied by a fuel efficiency modifier, based on the formula Fuel Efficiency Modifier = (10 ^ Engine Power Modifier) / 10.

For example if you choose to increase Engine Power to 125% of normal. The Fuel Modifier would be (10 ^ 1.25)/10 = 1.7783, so for a power increase of 25% fuel use would increase by 78%. This is shown on the dropdown as "Engine Power Modifier 1.25. Fuel Modifier 1.78". For an engine with 200% of normal thrust, the fuel modifier is 10x. This is the equivalent of a FAC engine in Aurora, except now you can have different size engines and you can have more than 1 per ship.

Here is the design summary for an engine of 5HS, using Internal Confinement Fusion technology, with a 25% increase in thrust, base fuel efficiency of 8 and no thermal reduction.

Internal Confinement Fusion Drive
Power Output: 12.5 MN     Exp Chance: 12     Fuel Efficiency: 13.5151    Thermal Signature: 125
Base Acceleration: 50 mp/s (5.1G)
Fuel Use at Full Burn: 168.9388 litres per hour
Engine Size: 5 HS    Engine HTK: 2
Cost: 62    Crew: 8
Materials Required: 15.5x Duranium  46.5x Gallicite
Development Cost for Project: 620RP

The Fuel Efficiency is calculated as base 8, x0.95 for engine size, x1.7783 for engine power modifier, which equals 13.5151. Fuel use in litres per hour is therefore 12.5 MN x 13.5151 = 168.9388. As that single engine alone would use up a 1 HS fuel tank in a little over 12 days, you can already see that fuel tanks are going to be a lot bigger in Aurora FTL. Based on testing so far, fuel is going to be 10-20% of hull mass for warships. A lot less for freighters as you can build some very fuel efficient engines as well.

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 below. Exp Chance is based on 10% of the engine power modifier, rounded down.

Now lets look at an engine designed around fuel efficiency rather than thrust. This is an engine of 25HS, using Internal Confinement Fusion technology, with a 70% decrease in thrust, base fuel efficiency of 8 and no thermal reduction.

Commercial Internal Confinement Fusion Drive
Power Output: 15 MN     Exp Chance: 3     Fuel Efficiency: 1.197    Thermal Signature: 150
Base Acceleration: 12 mp/s (1.22G)
Fuel Use at Full Burn: 17.955 litres per hour
Engine Size: 25 HS    Engine HTK: 12
Cost: 75    Crew: 2
Materials Required: 18.75x Duranium  56.25x Gallicite
Development Cost for Project: 750RP

The Fuel Efficiency is calculated as base 8, x0.75 for engine size, x0.1995 for engine power modifier, which equals 1.197. Fuel use in litres per hour is therefore 15 MN x 13.5151 = 17.955. So this engine produces more thrust than the above one and only uses a tenth of the fuel. However, it is 5x 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 accounting for 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 efficiency 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)

Ship design

The ship below is a Daring class area defence cruiser from my NATO vs Soviet Union campaign, converted to use the new engine mechanics.

Daring class Area Defence Cruiser    6,873 tons standard     10,700 tons full load     682 Crew     1643.6 BP
Armour 5-43     Shields 0-0     Sensors 1/1/0/0     Damage Control Rating 6     PPV 15
Maint Life 4.98 Years     MSP 576    AFR 152%    IFR 2.1%    1YR 39    5YR 580    Max Repair 252 MSP
Active Signature 214    Thermal Signature 1500    EM Signature 1680/0
Magazine 831   

Newtonian Magnetic Confinement Fusion Drive (12)    Total Power 150 MN    Fuel Use 1200 litres per hour   Exp 5%
Full Load Acceleration  14.02 mp/s (1.43G)    Hourly Acceleration 50.47 km/s    Daily Acceleration 1211.22 km/s
Standard Acceleration  21.83 mp/s (2.23G)    Hourly Acceleration 78.57 km/s    Daily Acceleration 1885.77 km/s
Fuel Capacity 1,750,000 Litres    Full Burn Duration 60.8 days    Delta-V Budget (Full Load) 80,366 km/s

Mk5 Guided Missile Launching System (15)    Missile Size 1    Rate of Fire 10
SN/SPG-31 Anti-Missile Fire Control (3)     Range 35.3m km    Resolution 1

SN/SPN-27 Navigation Sensor (1)     GPS 1680     Range 30.4m km    Resolution 60
SN/SPS-30 Missile Detection Sensor (1)     GPS 252     Range 35.3m km    Resolution 1

The key changes are as follows:

Standard vs Full Load: The standard mass of the ship is without any fuel, cargo, ordnance, colonists or parasites. Full load obviously assumes everything that could be loaded is loaded. In Aurora FTL, the current mass of the ship is tracked very carefully, so as you use fuel or fire missiles, the mass of the ship will be slightly reduced and your maximum acceleration rate will increase. The full load is also the volume of the ship, which will be used for FTL purposes. Volume is not affected by current mass and will always be equal to the full load mass.

No Maximum Speed: Maximum speed has been removed from the summary. Ships no longer have a maximum speed as it is based on acceleration rates and available fuel. In Aurora a ship had to continue using fuel to maintain velocity. In Aurora FTL, once you have velocity you can turn off the engines and you will continue at the same speed. However, you will need to use the engines to slow down again.

Active, Thermal, EM Signatures: These now have their own line on the summary. Many players didn't know what the old abbreviations meant and space on the top line was an issue with the additional of the standard load tonnage.

Engine Line: The engine line now shows the total thrust of the engines, compared to the old individual power rating from Aurora. Fuel use is the combined fuel use for all engines, in this case 1200 litres per hour. Bear in mind that most ships will likely spend a considerable amount of movement time with engines off. They can accelerate to a desired velocity, disengage engines and then engage the engines again to decelerate when required.

Full Load Acceleration: The 14.02 mp/s (1.43G)  section indicates that at full load, this ship has an acceleration rate of just over fourteen meters per second, which is equivalent to 1.43G for the crew. In an hour the ship can accelerate to a fifty kilometers per second and in a day to 1200 km/s. Bear in mind it will take just as long to decelerate. This utterly changes the tactical situation from Aurora. For example, if you charge into an unknown system you cannot simply reverse course if you detect an alien ship. You will have to either decelerate first and then reverse course, maybe increase speed and try to charge past, or attempt to change course, which is going to be extremely difficult unless you are going relatively slowly in comparison to your acceleration rate. I haven't done the final course change calculations yet but I can already see that you are probably going to have a pick a destination very carefully.

I haven't decided yet what to do with regard to gravity but I am leaning toward technobabble which states the existing trans-newtonian materials from Aurora are anti-grav materials in Aurora FTL, allowing you to build ships with an anti-gravity field. This solves the gravity issue not just in playability terms, as otherwise a lot of early ships wouldn't be able to leave Earth :), but also in performance terms as otherwise I would have to be checking the gravitational effect on every ship for every significant body in the system on every sub-pulse. Yuck! The disadvantage of ignoring gravity is that you can't do maneuvers to pick up speed from planets, although I can probably build something into the technobabble along those lines (switching off the anti-grav, etc). I will also probably add aerobraking maneuvers as well. Still a lot of work, which is why it will be months before anyone see this.

Standard Acceleration: This provides the same as above, with the assumption the ship is not carrying anything and is using its last dregs of fuel. This line and the one above provide a range of acceleration rates between which the ship will be operating. On the Ship window, the Ship summary substitutes this line with Current Acceleration, with the values based on the current ship mass.

Fuel Capacity: The first section is as before, with the total fuel capacity. This will likely be far greater in Aurora FTL than in Aurora. Next is the Full Burn Duration, which is the total time the ship could run its engines at full power using the total fuel capacity. Finally, the Delta-V Budget. There is no such thing as range based on fuel in Aurora FTL because you have effectively unlimited range. Instead you have a Delta-V budget, which is the total amount of velocity change you can achieve with your current fuel. The Daring has a Delta-V Budget of approximately 80,000 km/s, which means it could accelerate to 40,000 km/s and then decelerate down to zero, or it could accelerate to 4000 km/s and back to zero ten times, or carry out any combination of acceleration and deceleration that adds up to 80,000 km/s. This budget is calculated using a minute by minute calculation of the full burn duration, taking into account the slowly decreasing mass of fuel over the 60.8 day period.

Delta-V is the key value when looking at the ship design and the use to which you intend to put it. A system defence ship which is intended to fly toward an intruder, engage it and return home to its fuel source will only need enough fuel to accelerate to a desired speed, decelerate to zero and then carry out the reverse in order to return home. The outward leg will presumably require a longer period of acceleration as velocity is more important. A Delta-V budget of 15,000 km/s would allow an acceleration to 5000 km/s, the same deceleration to zero and then a return home leg with an acceleration to 2500 km/s. A long range geological survey ship would probably accelerate and decelerate many times. It will need a very fuel efficient engine and a very large delta-V budget.

As a further example, here is an early game freighter. This ship is designed with much more fuel efficient engines. The Delta-V budget is 30,000 km/s as that is deemed sufficient to carry out four accelerations and decelerations with an final intended speed of around 3000 km/s, while still allowing some reserve. This is because the FTL system in Aurora FTL, which I will go into in a future post, will often result in you entering your destination system with the wrong heading. It may be possible to correct course if the deviation is minor, or it may be necessary to decelerate to rest and accelerate again.

Atlas class Freighter    8,350 tons standard     34,100 tons full load     26 Crew     528.6 BP
Armour 1-93     Shields 0-0     Sensors 1/1/0/0     Damage Control Rating 1     PPV 0
MSP 10    Max Repair 50 MSP
Active Signature 682    Thermal Signature 400    EM Signature 0/0
Cargo 25000   

Commercial Ion Engine (4)    Total Power 40 MN    Fuel Use 105.5 litres per hour   Exp 4%
Full Load Acceleration  1.17 mp/s (0.12G)    Hourly Acceleration 4.22 km/s    Daily Acceleration 101.35 km/s
Standard Acceleration  4.79 mp/s (0.49G)    Hourly Acceleration 17.25 km/s    Daily Acceleration 413.89 km/s
Fuel Capacity 750,000 Litres    Full Burn Duration 296.2 days    Delta-V Budget (Full Load) 30,362 km/s

I realise this alternative Aurora will not be for everyone and it will be a niche area of a niche game :). Tactical planning is going to be critical, combat will be totally different, expansion will be slow and there will be a little more micromanagment than Aurora, although I will try and reduce that as much as possible. For example, in the fleet orders window you can include a maximum speed in an order so a fleet will accelerate to that speed, then switch off engines. Engines will be re-engaged when the fleet decides it needs to start slowing down. I'll post updates as I add new features and probably some mini-AARs from testing. I am not promising a release date :) as it depends on outside factors but hopefully there will be something before Xmas.

Steve
 

Offline James Patten

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Re: Newtonian Aurora
« Reply #1 on: August 29, 2011, 09:08:58 AM »
Tactical planning is going to be critical, combat will be totally different, expansion will be slow and there will be a little more micromanagment than Aurora, although I will try and reduce that as much as possible. For example, in the fleet orders window you can include a maximum speed in an order so a fleet will accelerate to that speed, then switch off engines. Engines will be re-engaged when the fleet decides it needs to start slowing down.

Sounds pretty neat.

I hope that the AI will give you the option of a direct-most route, a fuel conservation route, and so forth.  Additionally I hope that the computer will know when to start decelerating, because if I do it I will invariably overshoot or undershoot.

Will gravity slingshots be available?
 

Offline Dutchling

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Re: Newtonian Aurora
« Reply #2 on: August 29, 2011, 09:15:11 AM »
Sounds awesome!
I assume missiles will be totally overhauled too? As they have virtually unlimited range now too.
 

Offline deoved

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Re: Newtonian Aurora
« Reply #3 on: August 29, 2011, 11:06:16 AM »
Does this mean that transnewtonian elements will be removed and replaced by something more scientific like umm... Helium2 as fuel source, not Sorium?
 

Offline Steve Walmsley

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Re: Newtonian Aurora
« Reply #4 on: August 29, 2011, 11:47:40 AM »
Sounds awesome!
I assume missiles will be totally overhauled too? As they have virtually unlimited range now too.

Yes, missiles will be changed to use the new rules too. Interception of ships will be a lot harder though because missiles won't have as much maneuverability. I think two stage missiles with a high-G second stage might be useful. I may also have to look at laser heads for missiles, or proximity detonations. Missile targeting will have to use the probable location of the enemy ship at the time the missile is due to arrive, rather than the enemy ship's location at the time of firing.

Steve
 

Offline Steve Walmsley

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Re: Newtonian Aurora
« Reply #5 on: August 29, 2011, 11:49:03 AM »
Does this mean that transnewtonian elements will be removed and replaced by something more scientific like umm... Helium2 as fuel source, not Sorium?

Probably not, at least in the short term. I am going to leave as much of normal Aurora in place as I possibly can, given the amount of work the changes already planned will require. They won't be called transnewtonian elements though  - more likely anti-gravity elements :)

Steve
 

Offline Steve Walmsley

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Re: Newtonian Aurora
« Reply #6 on: August 29, 2011, 12:06:23 PM »
Will gravity slingshots be available?

Some form of gravity slingshot will be available, allowing spacecraft to increase/decrease speed and change direction by passing very close to planets/moon, etc. I need to take a detailed look at the math before coming up with a simplified Aurora FTL version. I think in reality this will also work with lagrange points, so that could be used in the game too (http://en.wikipedia.org/wiki/Interplanetary_Transport_Network)

Steve
 

Offline Napoleon XIX

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Re: Newtonian Aurora
« Reply #7 on: August 29, 2011, 02:15:57 PM »
This looks as if it'll be a great idea. Thank you very much.
 

Offline Echo35

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Re: Newtonian Aurora
« Reply #8 on: August 29, 2011, 06:55:07 PM »
What if you made jump points at gravity wells (Say, near a planet)? Then ships could slow down enough to transit without sucking away fuel.
". . . and that is why Sir Issac Newton is the deadliest son of a b*#ch in space!"
 

Offline Thiosk

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Re: Newtonian Aurora
« Reply #9 on: August 29, 2011, 07:17:33 PM »
why stop to get through a jump point?  If jumping preserved momentum, thats an interesting approach for combat.  

Makes invasions somewhat interesting, an alien species could come roaring through the jumppoint at high speed but have their engines off--no thermal sig-- then just coast all the way to the inner planets and when suddenly they flip on the shields and actives and engines and fling missiles in every direction.  

Also, ships already moving at 10km/s make defending jump points trickier-- the enemy ships will emerge and start moving fast, so beam ships won't be able to sit there and pave blinded ships as effectively.

(of course i guess we get FTL rather than Jump Points)


Side note: while I'm always interested in new expansions to aurora, this is one that at first glance I do not feel likely to use, being that i'm more interested in economics and combat than newtonian physics.
« Last Edit: August 29, 2011, 10:08:08 PM by Thiosk »
 

Offline ollobrains

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Re: Newtonian Aurora
« Reply #10 on: August 30, 2011, 01:02:10 AM »
good idea look forward to it
 

Offline Panopticon

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Re: Newtonian Aurora
« Reply #11 on: August 30, 2011, 01:34:45 AM »
Could have a lot of fun with box launcher armed ships in this, or really an situation where you can shoot your magazines dry quickly and then use your now much lighter ships higher accel to escape defenders that are fully loaded.

Missile fighters should see some good advantages.
 

Offline shadenight123

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Re: Newtonian Aurora
« Reply #12 on: August 30, 2011, 02:41:27 AM »
for the engines part which directly influence also missiles...it's like that mass effect quotation, were there are two soldiers outside of the capital and their sergeant is speaking to them:
"you know, in space there is no gravity. So something which moves will move on forever"
"yessir!"
"so, you do not shoot by the eye, because otherwise, somewhere, sometime, someone is going to receive a nasty fifty ton surprise of a hit"
"yessir!"
"AND THIS IS WHY YOU WAIT FOR THE SENSORS TO GIVE YOU THE ALL CLEAR!"
"yessir"
people die all the time, it's not a problem.
it is if you're sending them to die.
i'm not. they just need to learn to be better.
at NOT BREATHING ON MARS!?
they need NOT TO CARE!
my blog (updated 17/12/2011) (updated every saturday):
http://shadenight123.blogspot.com/
 

Offline waresky

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Re: Newtonian Aurora
« Reply #13 on: August 30, 2011, 05:37:52 AM »
for the engines part which directly influence also missiles...it's like that mass effect quotation, were there are two soldiers outside of the capital and their sergeant is speaking to them:
"you know, in space there is no gravity. So something which moves will move on forever"
"yessir!"
"so, you do not shoot by the eye, because otherwise, somewhere, sometime, someone is going to receive a nasty fifty ton surprise of a hit"
"yessir!"
"AND THIS IS WHY YOU WAIT FOR THE SENSORS TO GIVE YOU THE ALL CLEAR!"
"yessir"

^_^
 

Offline waresky

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Re: Newtonian Aurora
« Reply #14 on: August 30, 2011, 05:38:55 AM »
...Aaaand..

O.M.G..Steve.

Awesome idea..

Damn..,i send u : Good Work mate!!!!
 

 

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