Newtonian Aurora

[Steve Walmsley (OP)]

Another quick update:

When you leave planetary orbit (or if you launch missiles), your ships (missiles) will have the same momentum as the planet or moon from which they are departing. If their destination lies in the opposite direction they will have to overcome that starting momentum first.  To aid in decision making, you can optionally display information about each system body on the system map. The four values are:

OS: Orbital Speed. This is the speed at which a body moves along its orbit, relative to its parent body, and this value will never change during the game.

MS: Maximum Speed. This is the maximum speed a body will move through space, based on its own orbital speed plus the combined speeds of its hierachy of parent bodies. For example, if a moon moving at 30 km/s is orbiting a planet moving at 10 km/s, which in turn is orbiting a star that is moving at 6 km/s, at one point in its orbit the moon will be moving through space (relative to the system primary) at 46 km/s. The maximum possible speed of the body will remain constant during the game

HD: Heading. The current heading of the system body relative to the system primary. If this is a planet orbiting the primary, its heading will always be equal to its bearing from the star + 90 degrees. However, a moon orbiting that planet will have a heading that combines the vectors of its own movement and that of the parent body. The heading will change as a planet or moon orbits.

AS: Actual Speed. The actual speed of the body through space on its current heading, relative to the system primary. For a planet orbiting the primary, this will not change. For a moon orbiting that planet, its speed will increase as its moves in the same general direction as the planet and then decrease as its moves in the opposite direction. For a moon orbiting a planet, orbiting a star that is orbiting another star, the actual speed will vary considerably during the game.

These factors are affected by whether orbital movement in general is turned on and also if asteroid orbital movement is turned on. Even if asteroid orbital movement is turned off and the orbital speed of an asteroid is therefore zero, an asteroid may have a non-zero max speed if orbiting a non-primary star. In that case, heading will change during the game and potentially actual speed as well (if the parent star is orbiting a second star that is in turn orbiting the primary.

Below is a screenshot of the inner moons of a gas giant. The gas giant is orbiting the primary star and is currently on a heading of 181 at an orbital speed of 5.4 km/s. Those moons on the left are moving in the opposite direction to their parent so their actual speeds are lower than their orbital speeds. Moons on the right are overtaking their parent as therefore have actual speeds greater than their orbital speeds. The current heading and actual speeds of system bodies could have significant impacts on play, especially in multiple-star systems.



Steve

[chrislocke2000]

Cripes Steve, I thought learning to fly was a reasonably challenging past time for me but I can see now taking on NA is going to be far more of strain for the old grey cells!

[bean]

Are you forgetting that ship speeds are on the order of a thousand km per second or so?
Even plasma is not particularly healthy, with armour at 100s of MJ and shells starting at GJ all the way up to TJ ranges. 

A projectile vapourizing on your whipple shield is like a nuke going off right next to you.  And we all know what happens when one does that. 

No, I'm not.  I'm assuming that armor has a role at all, because if it doesn't, then we're into one-shot, and I thought it was agreed that that was not fun. 
Steve really should bump the armor or lower ship velocity.  Either way, the physical shape of the projectile will be important. 

[procyon]

Cripes Steve, I thought learning to fly was a reasonably challenging past time for me but I can see now taking on NA is going to be far more of strain for the old grey cells!

Yeah, I don't see this as a game for the faint of heart.  You won't turn it on and be ruling the galaxy in an hour or so.  I'm guessing I'll be lucky to figure out how to do anything at all in the first hours/day/week....

The ships are only considered spherical for calculating active sensor cross sections and armor mass. Looking at the sample ships seems to indicate the descriptive length is 3.5x the spherical radius. For realistic railguns, it doesn't help.

When I pointed out that a theoretically optimal railgun shell is under uniform field acceleration, I first calculated how long the rails would have to be if the force was concentrated at one end. I guessed aluminum would be a good material since it is a good conductor with a high strength/weight ratio. Say, 400 MPa strength and 3000 kg/m3 density for a short, squat, 1kg cylindrical shell 50% longer than it is wide. If accelerated by a uniform pressure force on one end (one of the worst case situations) this round should withstand 138,000 Gs. However, even at that acceleration to reach 69 km/s the shell would need 50 ms and 1,760m long rails.

I spent maybe 10 seconds worrying at this length, before remembering that the sorium fuel has 10,000x the energy output of our nuclear missile warheads. Then I shrugged, tossed the math figuratively out the window, and declared that the Newtonian Aurora rail-guns appeared to be nearly theoretically optimal in design. Maybe the railguns are nearly optimal, maybe the shells use T-N materials themselves for better performance. It doesn't really matter either way. Newtonian aurora is operating a half step beyond what is theoretical possible. So what if a 100x acceleration increase is needed to make the rails fit inside a ship: compared to other game aspects a 100x improvement in material choice and/or field distribution over a suboptimal design with modern materials isn't much of a stretch.
It doesn't have to be an instantaneous change in acceleration. A ramp-up time to full acceleration is going to be essential to limit jerk and at least partial intrinsic to overcoming rail inductance. Ideally the ramp up time ought to be small compared to time spent accelerating, but a 1% ramp-up time (say 5e-6s) should be sufficiently small to avoid impacting final velocity. By comparison, the time required for light to cross the rail width is 2.2e-10s. I don't think light-speed tidal lag will be an issue.
Ok... quantum mechanics and sub-atomic physics is beyond me, but this doesn't seem quite right. Railguns are applied electromagnetics, so it should only be the electrons, and maybe protons, that get accelerated. Binding forces then allow us to assume it the individual charged atoms getting accelerated. This seems similar to ion thrusters, which accelerate individual charged attoms to nearly the same speeds over much shorter distances. I guess particle stripping might be a concern at realy high accelerations, but I'm uncertain if even newtonian aurora railguns are accelerating that fast.

I pretty much decided the same thing on the math.  If folks try to point out something patently false I have a bad habit of trying to correct their view.  But for this game, it really shouldn't make so much difference.  So long as we don't blatantly violate reality I am ok with it.

On the thought of railgun slugs, getting a rod to hit with the proper orientation is pretty remote - but shouldn't matter.  If your close enough to guarantee orientation, you are dead too.  But on how the damage is applied, I will accept whatever Steve codes.  With the energy we will see, it won't make much difference unless it can pass through without a detonation.  Otherwise the energy will just be too much.  A rod hitting the whipple shield sideways just means that the ball of plasma that destroys your ship occurred a meter of so earlier than it would have if it had hit the hull.  

Same with defenses and such.

The slug might be a solid object that is somehow engineered to survive launch.  It might be a pure field that has an associated mass that is what the launcher is firing.  It might be a field to contain the plasma created by launching the slug.  Regardless, it will be a projectile moving at a certain velocity that will impart its energy to the target if it connects.  If you see it as a solid slug, that is ok.  If I see it as a field, not a problem.  The effect in the game will be the same for all intents and purposes.  Discussing how it works is fun, but not Steve's issue.  In the end it just needs to be a projectile that is tracked and damages a target.

Same with the sandcaster.  Tungsten dust, silica sand, table salt spilled in the galley, doesn't actually matter to the game.  Fun to discuss the details, but for Steve it should just boil down to how fast it can intercept an inbound and how effective it will be.  As your tech increases, it should get more effective.  Whether better saturation, better interception accuracy, whatever it is wouldn't actually matter - just that it stops inbounds more effectively.

I love the discussions, but I don't want this to slow Steve down.  

[jseah]

No, I'm not.  I'm assuming that armor has a role at all, because if it doesn't, then we're into one-shot, and I thought it was agreed that that was not fun. 
Steve really should bump the armor or lower ship velocity.  Either way, the physical shape of the projectile will be important. 

Regarding discussions as to whether ships should be slower or new propulsion systems should be used, or kinetic weapons should work differently, etc.

For the first version of Newtonian Aurora, I am going to try and make things feel as realistic as possible, unless the math problems are just too horrible. This means the possibility of one shot kills.

Looks like it's going to be that way for first version at least. 

Although I feel the need to mention that railgun damage depends on closing velocity and hence sometimes it will be useless (stern chase) and sometimes one-shot-kill (head-to-head fly by). 

[bean]

Looks like it's going to be that way for first version at least. 

Although I feel the need to mention that railgun damage depends on closing velocity and hence sometimes it will be useless (stern chase) and sometimes one-shot-kill (head-to-head fly by). 

I can't speak for anyone else, but I'd far rather be hit by something blunt that explodes on the outside, then by something pointy that goes in.  At the very least, the energy is spread over more armor area. 

On the thought of railgun slugs, getting a rod to hit with the proper orientation is pretty remote - but shouldn't matter.

It's called a guidance system. 

[UnLimiTeD]

I quite honestly don't care how several hundred gigajoule are spread over a spaceship, there won't by one left afterwards no matter what.

[bean]

I quite honestly don't care how several hundred gigajoule are spread over a spaceship, there won't by one left afterwards no matter what.

That depends on several things.  For one thing (and this is poorly simulated by current Aurora, btw) hits will often pour on a lot of overkill.  It may only take 100 MJ functionally destroy a system, but in death, the system might well absorb another 900.  Another is that we're assuming a lot of advances, including materials science.  With good enough armor, you could survive that sort of pounding. 

[jseah]

It may only take 100 MJ functionally destroy a system, but in death, the system might well absorb another 900. 

This is a pretty good point.  Since most systems are TN materials, we could increase the damage absorption of components to gigajoule range. 

Would mean that systems need a way of tracking damage received and have a "disabled" threshold and a "destroyed" threshold.  Destroyed systems would probably need a shipyard to fix while disabled could be fixed with maintenance supplies. 

[Sloshmonger]

Will there be any automatic logic to say "Hey, if you wait 5 days to launch, you can get there faster and/or expend less fuel?"

I know I'm looking forward to scheduling low-deltaV launch windows for cargo runs on the Earth-Mars route.

[PTTG]

If nothing else, it'd be nice to have a "delay until forecasted fuel consumption for next order is below 50% capacity"

[TheDeadlyShoe]

I dunno, I think it'll be interesting how peoples howitzers-at-ten-paces warship designs evolve.   We might see ridiculous thrust ratios for generating misses.  I don't know if that discussion about having structural ratings on ships wrt acceleration went anywhere in terms of Steve's design- it might be where all the design tonnage you used to put into armor goes

Let's not forget the RP possibilities. A multi-faction Earth game imposes many political limitations on warship design and objectives. Heavily armored orbital stations or warships designed to win orbital control in WW3, since it might start at a hair trigger. Ships designed to sit in the outer system and commit relativistic strikes on signal - solar MAD. RP'd treaties which prohibit same relativistic strikes.

I wonder... If railgun projectiles are actually tracked, as it were, could you put a parasite warship in between you and the cloud to eat the impact?  Perhaps hangar space = armor :]

[procyon]

I wonder... If railgun projectiles are actually tracked, as it were, could you put a parasite warship in between you and the cloud to eat the impact?  Perhaps hangar space = armor :]

That is my plan for defenses for planets/facilities.

A small crowd of fighters with railguns/light nukes.
Disperse to destroy interceptible munitions.

Have interpose to stop leakers/uninterceptable.

[jseah]

I must admit I didn't think of that.  Then its a race to see whether interceptors are more expensive than munitions + fuel needed to get it there. 

[Panopticon]

Or, see if you can get interceptors moving fast enough directly away from the railgun munitions to reduce the damage to nothing.