*rant* You want space ship battles you should have went with a video game or something, you may have wasted your money, so give your books to an actual role player. Maybe you should have read the book more before you bought it. */rant* Yeah, I'm being an ass here, my apologies. I just hate it when I hear people whining over the little details like this. Like Arena mentioned, Space combat in a "hard" sci fi universe is impossibly boring with a few intense moments where you may or may not be vaporized in a moment of bad luck. Even the small details like "catching up" to another ship in a realistic manner would be difficult at best. EP, much like Burning Empires uses ships as plot devices and setting more than anything. You want to make it more exciting, and toss out the Hard SF stuff, then improvise and have the players make a few piloting rolls, and a few gunnery rolls too and go from there. Easy.

It has no default space combat. However, the system is simple enough to cobble something together if you want. Maybe just create ships as characters and scale up the current combat rules? If you are looking for a more tactical model, no, EP is pretty far from what you want (but those systems are also usually extremely ungainly and math-heavy). Unless you love math as much as I do, I honestly would recommend finding a computer simulation. You really can't get around it otherwise.

I hope I didn't scare you with that post. I would love to develop this field more. One thing that I think is worth thinking about is the ships between the Fighter and Destroyer. The Destroyer is a monster (the *engine* is a particle beam weapon that can dig through miles of rock!), but it is also heavy, expensive and vulnerable - just what I would expect the Jovian Junta to build. If my analysis is right, the real advantage will go to ships that are more like carriers of lots of little assets. They sweep in, deposit clouds of weapon buses, sensors, decoys and fighters, then keep out of the way from the real battle. I see them as "high bandwidth frigates" or agile carriers. They might be very lightly armoured, hoping the damage just goes straight through than spread. Another big problem is hiding course adjustments - they are visible across the solar system, and there are too many eyes. I wonder if there is an advantage in "stealth drives" that push by expelling really cool and heavy propellant (e.g. using a railgun)? I doubt they can be made to work, but that would allow surprise appearances on someone's doorstep.

Wow, that was a lot of work! It's really good stuff. I've got some comments and suggestions, mostly formatting or grammar. First, it looks to me that you are using LaTeX, yes? What document class are you using? It looks like Book with two-column mode on. I'd suggest either switching to something with wider margins like Article or using only one column. -Page 7. You say "this table" but don't have a reference, what table is it referring to? -P.7. Your leading quotes are in the wrong direction. TeX recognizes ' as trailing quotes and ` as leading quotes. -P.9. I thought there was a way to make a section take up the full width of a two column article, but I can't find it right now. This problem would also be solved by switching to one column. -P.9. You have the word "sublight" where I think you mean "sunlight". -P.10. I think Albedo is the first term you use that isn't pretty obvious, perhaps define it? -Figures 1&2. These are unclear, but I figure you know that. You could adjust the width of the figures so you get more space for them. -Neutrino positional detection. I'm pretty sure they can do position, Kameokande was able to pin point the supernova 1987b when it showed up. When the neutrios interact in the water tank detectors like Kameokande they produce a ring of Cherinkov Radiation at a 45 degree angle to the path of the neutrino, so they can use that to point the neutrino. I'll have to ask my friend who does neutrino astrophysics. -P.19. I think you meant Evap where you have Eeap. -P.22. Your section on "multi-barrel" railguns mentions sleeves out of nowhere, what are they and why are they important? Finally I'd like to offer two more ideas for munitions. I know that GURPS Transhuman space really likes X-Ray Lasers that are pumped by nuclear bombs, I've never been all that clear on how they work but I think they are a real thing. Second is a subset of the particle beam weapons. With a laser intensity on the order of 10^20 W/m^2 incident on a gold foil you can make a beam of electrons with >1MeV energy. With some tricky target shape you can get a pretty decent divergence angle, so this might be useful for beam weapons. Though I don't know quite how it scales. That stuff is cutting edge physics for Fast Ignition Fusion, and infact my current research field. So who know's if it's viable. I hope you'll take my comments constructively. I really like your work and look forward to seeing it as it progresses. P.S. While I don't have personal experience with Fantasy Fligth's Rogue Trader I'm informed that it has a good system for allocating work to all players in Starship Combat, so that might be something to look into. Warhammer though does laugh in the face of the laws of physics.

Keep in mind, Aremanteraraous probably has more letters behind his name than you find above a kindergarten chalk board. I believe he works in neurophysicsnanoastrobionomy. More seriously, this is a HUGE help as a writer. Sure, you don't want all of these formulas on the game table, but you want the rules you operate to be based off of them (or at least aware of them). What he's done is given us guidelines so we can create consistent ships that operate in a consistent manner in a consistent universe. Sure, it may not be the table you play your game on, but it is the concrete foundation that holds up the house for your table to fit inside.

Here is something I literally dreamed up tonight, a space battle system for EP as a card game. Still not quite finished (we need to figure out the cost of the cards, I am definitely unsure about how to balance the ships) and obviously not playtested. But I think it has promise - it abstracts some of the logic I see in space warfare. It might of course annoy us who like to keep a 'pure' d100 dynamics but I think the cards make sense to keep track of all the little devices. Ship battle Each player has a hand of cards corresponding to their assets: weapons, sensors, decoys and one or more spaceships. Each side has a number of points to spend on building their hands. There is a general discard pile and a destroyed pile that is emptied into it after each round. A fixed number of turns, determined by the relative velocity, are played. The player with the longest range or best strategy begins. Turn order: 1. On their turn, each player places a number of sensor and weapons cards face up in front of them. It can be any number of the cards on the hand. 2. A number of sensor cards equal to the number of cards discarded to the destroy pile in the previous round are tapped (turned 90 degrees); they cannot help targeting. 3. Each working sensor allows hitting one different target. If there are fewer sensors than weapons then some of the weapons must attack the same target. 4. Each attacking weapon must either attack a card lying face up on the table, or a randomly chosen card in the hand of the player. Most cards are immediately put into the destroyed pile; the exception is the spaceships (see below). A weapon that has been used this turn is tapped. 5. After the attacks have been handled the player returns the sensor cards to the hand. Weapon cards will remain face up on the table (except for one-use weapons) and are returned to untapped when it is the player’s turn again. Winning: The winner is the side that retains spaceships while the other lacks them. If both or neither have ships, then the side with the most card points wins. Ship defense: If a ship is attacked in step 5, then it can defend itself. For each railgun and missile attack (but not laser attacks) it can use one of the point defences on its card as well as untapped weapons cards on the table. Weapon cards from the hand can also be placed on the table and used immediately. For each defending weapon roll one dice; on a 1 against a railgun projectile and 1 and 2 against a missile the incoming attack is stopped. If it gets through the ship is either destroyed or damaged (as per the card). All used weapons except for ship point defences are tapped. The ship card is now face up on the table and can be used as a weapon. Ship cards Fighter Point defense: 3 Weapon: 2 railguns Destroyed by one hit. Destroyer Point defense: 6 Weapon: 2 railguns, 2 lasers After each hit, put a marker on the ship. Destroyed after three hits. Weapons cards Laser array Railgun One-shot laser (put in destroyed pile after use) Missile bus (When placed on table, it turns into N missile cards. Bus remains and can be turned into one missile before being immediately discarded) Missile (put in destroyed pile after use) (types: Kinetic, Nuclear, AM, Nano) Blinder (when activated, acts as N extra destroyed objects for blinding enemy sensors. Put in destroyed pile after use) Sensor cards Sensor device Active sensor (when used it cannot be returned to the hand and must remain on table) Decoy cards Decoy Chaff (if chaff is hit, it is not discarded) Action cards (these cards can be bought like other assets but are kept in a separate pile) Dodge (Play when ship is being attacked. Acts as 3 point defenses, even against laser. Discard after use) Armor/repair (Play after a ship is hit. Reduce the number of damage tokens placed on ship by one. Discard after use) Triangulation (Play before targeting. Tap three sensors. Reveal a random card from the opponent’s hand and put it face up on the table. Discard this card after use.) Stealth (Play at any time. Return a face up card to the hand) Dead angle (Play when one of your cards is rageted. A particular weapon cannot target that target and must select another. Discard after use)

nezumi.hebereke wrote:

Keep in mind, Aremanteraraous probably has more letters behind his name than you find above a kindergarten chalk board. I believe he works in neurophysicsnanoastrobionomy. More seriously, this is a HUGE help as a writer. Sure, you don't want all of these formulas on the game table, but you want the rules you operate to be based off of them (or at least aware of them). What he's done is given us guidelines so we can create consistent ships that operate in a consistent manner in a consistent universe. Sure, it may not be the table you play your game on, but it is the concrete foundation that holds up the house for your table to fit inside.

neurophysicsnanoastrobionomy! hahaha. You forgot Xeno. Seriously, I wasn't saying what arena wrote was awful or anything, quite the opposite, I was only trying to point out how difficult it would be for "the average reader" (Whatever that means) to pick up and use effectively. I agree, reading that gave me a slew of ideas, I especially like that he included using the drive as a weapon (Very "Prefect").

While I like the idea of your starship combat game, I've got one very specific worry. It seems it works well for only 2 players, one for each faction. I've got four players in my group and I'd really like to see them all involved. Sure they could all have spaceships, but as the number of combatants rises so does the number of attacks and debris. If everyone destroys one item on their first turn then on turn 2 everyone needs 5 or more sensors to see anything. Realistically I understand that mechanic, but for enjoyment of the game I'm not so sure. Also, it's sort of unreasonable for my group of four to run around in four ships when they only have one pilot. EDIT: I light of Arenamontanus last post on turn by turn blinding. What about simultaneous turn resolution? Instead of placing everything you want to do face up on the table, both players do it face down. They then proceed left to right, flipping over their cards and resolving them. Each card could have a "reaction" or "tracking" speed number, which determines which gets resolved first. For instance Adam and Betty are playing, the first turn they each place down three cards. Once they are both done placing they each flip over, starting with their leftmost card. First Card) Adam has a Sensor Sweep with at a speed of 2 and Betty shows a Sensor Drone with speed of 1. Since there are no attacks speed doesn't matter. The sensor drone is stronger, but slower. Second Card) Adam shows a Missile Barrage of speed 2 and Betty shows a set of Point Defence Lasers of speed 5. So Betty deploys her PLDs first, so then they can be spent to intercept the Missiles. Had Adam used Beams the PDLs would have stuck around until used, they form a deterrent vs. using intercept-able weapons. Third Card) Both players show Phased Array Lasers on Speed 3, so both get resolved. They each attack their opponents sensors, but since they resolve on the same speed the destruction doesn't happen until after they have been able to shoot. I've got a couple other ideas to offer. Perhaps all non destroyed cards get returned to the players hand after the turn? Just because you have missiles doesn't mean you want to fire them every turn, especially if the opponent has Point Defences? Maybe your time would be better spent using Damage Control? Which brings me to my last idea, Ships and Command and Control. Maybe ships should be played face up? So that the opponents knows what they are facing. If any of you have played Mansions of Madness it's got a good mechanic where all obvious stats are printed on the top of the monster cards and secret ones hidden on the bottom, and players are only allowed to look at the bottom once they've injured the monster. Perhaps the way to look at the bottom is a detailed Sensor Sweep on the enemy ship? Finally I think con-straining the number of cards placed on a turn might be a good idea. It's a way to stop players from simply playing everything on the first turn. Each ship would get a C&C stat, and each card would have a cost, representing the amount of things a ship crew and their computers can do in an interval of time. If a Destroyer has a C&C of 3 and Sensor Sweep costs 1, Missiles cost 1, and PDL's cost 1 then the player could do all of those turn one. But if Phased Array Lasers cost 2 then they have to choose. It would also be a way to balance lasers. Wow, that edit ended up being much longer than I hand anticipated. I'm just throwing ideas out there. I think this could be a very fun and fast little game.

I'm not even sure I like the idea of a card game... no that's not correct. The Idea of a separate (card) game involving EP ships combat sounds awesome! Not too sure how this could be used as a in game role playing supplemental, you're probably right anyway, not enough d100 action going on. Are there any other RPGs out there that use the d100 mechanic and have fairly good ship to ship combat rules? Something like Elric or Stormbringers ship to ship could be ported easily enough. Just thinking out loud here mind you.

Arenamontanus wrote:

But it might make for a better card game....

That definitely was the angle I was heading towards. But above everything else is the multiplayer problem for me. I think I'll be snagging my friend's copy of Rogue Trader, it's d100 and is entirely based around having a party that are the Important People on a starship that's somewhere in the frigate range. I'll let you guys know what I think of it, but I've played the Deathwatch and Dark Heresy versions of the game and quite enjoy them. Arena should correct me, but I think that DeltaV is a combination of max speed and total fuel. If you want to arrive at a planet you need to accelerate to movement speed, cruise, and then stop yourself. So if I've got 10 units of DeltaV I can't use more than 5 to accelerate, otherwise I won't be able to stop. Also if you use that method then you don't have any margin for error or maneuvering.

Max speed is a meaningless concept in space travel short of relativistic effects and fuel constraints (unless debris detection and collision avoidance or something similar is an issue of course) Delta v is the effort needed to change from one trajectory to another. It is also used loosely as a spaceship's total capacity for trajectory change, ie its total fuel (though changes in total mass as reaction mass is used complicates things a bit), or conversely about how much fuel is needed for a long range flight. When used in the context of a limited time frame, what matters is the spaceship's max acceleration, as this determines how much delta v it can produce in the given time.

nezumi.hebereke wrote:

Should delta-v be considered equivalent to the maximum speed (for the purpose of back-of-the-envelope calculations)?

More or less. If I understand JSnead's intentions right, normally you launch using about a third to a half of the delta-v budget (but you will also have an orbital speed from the body you left: Earth moves at about 30 km/s), and then use about equal amount to slow down, leaving maybe a third to 25% for emergencies or battle course corrections. So you can go faster if you do slingshots, Oberth manoeuvres and gamble on somebody catching you with a tug-ship at your final destination, but it is often a bad idea.

Quote:

What are the calculations for electrical power based off of? Is this just for the engine, or does it include things like life support? I assume these are the maximum for a momentary draw, not for the lifetime of the power plant, correct?

You mean the engine power? They are based on the energy needed to produce the kinetic energy of the reaction mass at the stated exhaust velocity. It is not really electric energy in most cases, mainly heat (and then there is at least an equal amount of waste heat you need to just get rid of). The energy needed for powering life support is far, far smaller - I have a loose guess in the sensors section for about a kilowatt per person at the minimum.

Quote:

Is there a quick method to calculating the wattage requirements for things like railguns?

To launch a mass m projectile at velocity v, you need 0.5mv^2 J of energy. The railgun has efficiency 10% or so, so a first guess is E=5*m*v^2 J. So if you launch 1 kg projectiles at 10 km/s (slow), you need 5*10^8 J. A fast projectile at 100 km/s needs 5*10^10 J. That gets released in one burst, but if you have P watts of power and slowly charge up capacitors to shoot, then you can shoot P/E times per second. The Destroyer, if it could use 600 GW power, could shoot 1200 slow projectiles per second or 12 fast ones (but it would likely burn out the railguns since a sizeable fraction of the energy - those other 90% - would heat them). I suspect at most (handwave) 10% of the total energy can be used to power railguns and lasers, since they require a much trickier cooling system than the drive.

From Andromeda D- Zero [url]http://www.megavideo.com/?v=MX1WL35B[/url]

Okay, so the calculations for power in your paper are just for power for maximum acceleration. How did you originally derive the specific impulse? edit: I'm looking for a shorthand way to figure out the maximum fuel available to a ship. I know you've already calculated that, to get the delta-v/acceleration/power calculations, but I'm concerned I may be going about deriving it incorrectly.

So the specific impulse numbers are all gotten from somewhere else, not derived. That's sort of good to know. Are they listed somewhere? I didn't see an Isp column in any of the charts. As for the fuel aspect, I'm hoping to handwave it as much as possible. Fuel has zero 'weight', but a heavier type of fuel requires more fuel 'points' to accelerate, and has a lower maximum amount. Are all of your delta-v numbers also from Jsnead/the book, or are they somehow derived statistics?

Arenamontanus wrote:

OK, I give in: here is the current state of my writeup on the physics of EP space combat. http://www.aleph.se/EclipsePhase/EP%20naval%20strategy.pdf

Very interesting stuff. On railgun damage, I'm not sure Newton's penetration approximation apply. At these high velocities you can't just stop a railgun slug. The kinetic energy in a 10 km/s projectile is enough to heat up around 70 times its own mass of metal to boiling point, so when it impacts something it is either going deeper than it its own length ("breaking" Newton's penetration approximation) or more likely it'll vaporize itself and what it impacts with and generate a massive explosion from the overpressure. Even a 100kg slug at 10 km/s gives a 1 kiloton explosion, about 1/15th of the Hiroshima nuclear bomb. I won't pretend to understand exactly what does happen, but Newton's approximation doesn't apply here.

It seems reasonable that any mass in the path of a big rail gun slug gets turned into a rapidly exanding ball of plasma, which would make the best armor strategy no armor - you just have to deal with the hole and hope the kinetic energy bleed explosion isn't too bad. But then attackers would start loading their railguns with slugs that broke up into a great number of flechettes, ensuring many hits and as much kinetic energy bleed as possible. Launching disks flat end first could be a good idea also - if you could somehow get a proper spread, a stack of them, like coins in a shotgun, could work too. Which again changes armor preference...

Ratchet2012 wrote:

^_^ InsidiousAlgorythm your trolling! !!LOL TROLL!!

*Yawn* I said what I had to say to you, and this is all you could come back with? Get back to me when you have something intelligent to say.

Regarding a double shot as a whipple shield weakness - make sure to spin the shield.

There's some neat work on realistic space combat that's been done by Blue Max Studios:

http://bluemaxstudio.blogspot.ca/2011/10/space-combat-in-black-desert-ac...

I think a lot of it crosses over to EP very well. Especially the Detection, Determination, Preparation phases. The only thing that might be different is the manoeuvring and engagement, since EP has far more powerful propulsion and weapons technology.

Crazy Tom wrote:

There's some neat work on realistic space combat that's been done by Blue Max Studios: http://bluemaxstudio.blogspot.ca/2011/10/space-combat-in-black-desert-ac... I think a lot of it crosses over to EP very well. Especially the Detection, Determination, Preparation phases. The only thing that might be different is the manoeuvring and engagement, since EP has far more powerful propulsion and weapons technology.

I think this is the correct link: http://bluemaxstudios.blogspot.com/2011/10/space-combat-in-black-desert-...

I would recommend focusing on atmospheric combat as the primary medium rather than ship to ship combat. Bonus points for the fact this might work even in the uppermost atmosphere where some satellites and space elevators may exist (I'm not positive on how true that is so please correct me if I'm mistaken). Don't get me wrong, I understand the allure of awesome Star Wars style space battles but those were heavily inspired by aerial battles during World War II rather than the hard sci-fi style Eclipse Phase goes for. So if you want that style of fight you may as well go with the source material and have future jets chasing each other through surreal planetary environments. I myself am not an expert in hard sci-fi with only a passing understanding with how space battles would go down in more grounded settings but I have heard that The Expanse got a lot of it right so you could use that as an inspiration. Or if nothing else it offers a more realistic take on space combat than Star Wars, so even if you make your setting a big softer you aren't clashing as strikingly with the themes of the setting as a Star Wars style space battle would. And in all fairness things like the Pandora Gates and Exurgent Virus offer some liberties for a bit of softness here and there as long as you're careful with it and are mindful of the atmosphere and theme of the setting.