Ship to Ship Combat and FTL

[CadetNewb]

It might actually, but let me do the math and see.

Let's assume that Hanako is having the ship floor it at 0.375c (404,719,818 km/h) using its STL drives, but without overboost or somesuch, and is trying to get to a planet that's in the Goldylocks Zone of a star that's like our own sun. For fun, let's assume it's Earth. That means she has to travel 121 AU in from the edge of the system, assuming we're using the Heliopause as the point of no FTL (this would be giving or taking 1 AU depending on where in orbit the planet is at the moment of course). An AU is about 150,000,000 kilometers, and 121 AUs are 18,150,000,000 kilometers. That means that it's going to take 1 day, 20 hours and 48 minutes for Hanako to get to Earth, assuming the Eucharis just arrived in our Solar System. And since the Eucharis has the Combined Field System, it'll be heading in at 0.375c the whole time, making all observers collectively soil themselves since they're unaware it can rapidly decelerate and come to a stop at the last moment. And then Japan would love her the moment she steps off the ship, but that's another matter entirely.

On top of that, there's getting to the system in the first place - assuming that Sol (and Earth) is the same distance from Yamatai as Asura, that's 90ly. Since the Plumeria class has a hyperdrive rated as 1ly per minute, that's 90 minutes. Overall, the travel time for getting to Earth from Yamatai in this scenerio would be 1 Day, 22 hours and 18 minutes.

At the same time, if Hanako were trying to get to one of the outer rim planets like Neptune, and it just happens to be all the way on the other side of the system when she arrives, that's another 30 AU she's got to travel across. That's another 4,500,000,000 kilometers, which will take 11 more hours. In this second scenario, it would be 2 Days, 9 Hours and 18 Minutes I think.

This is all assuming my math is right.

Previously, we've been assuming we appear in the system itself, and outside of the destination's Hill Sphere rather than the system's Heliosphere or something like it, meaning response time was like calling in the National Guard to take care of an errant tank perhaps. I believe that this change wouldn't solve the problems that come out of having such a small travel time from location to the next, but it does help to mitigate it. I think it's a step in the right direction, but I don't know how others would feel about it considering that many have been likely portraying FTL entry into a system differently than this.

 

[Fred]

I kind of wish in-system travel between planets was faster than that, though. Enough to muster up a "Oh no, something else is happening at that other planet GOGOGOGOGO" and you'd get in the vicinity of what's happening fairly quickly. That makes me wonder if higher sublight speeds ought to be looked into (upward to 0.75c?).

There's also how this leaves ships outside of planetary gravity wells for a long time. How are you going to engage in combat with a ship moving at a large fraction of c? Lasers might do it, but missiles and railguns won't (because if ships are supposed to fight using only engine/RCS thrusters, weapon speeds will need to be adjusted accordingly - meaning it'll either be too fast in combat or not fast enough at cruising speeds). I could see a laser-weapon loadout being favorized as ideal interception/overtake weapons on account of "I can fire that on you, and if you stay up a .3c I am going to hit you with your shields down. You don't want that to happen so slow down if you have an inkling of survival instinct". Of course, if graviton beams go at the speed of light, then that replaces the laser as the ideal interception tool. But the need for means of interdiction in such a way also discourage increasing ship sublight speeds... or your lasers/graviton beams won't be able to successfully hit.

That could be ground for nice high-speed chases until you can go to a point where you can fold out. Except... you wouldn't be able to - the fold out point could be hours to days away. Narratively, that seems weak.

It makes me wonder how piracy is going to be done while in-system as well (since that's the only place that can feasibly happen). Considering militaries are unofficially measures as 250 ships per system, it makes it look really infeasible to have any piracy going on near Yamatai. Which might have Wes go on a pro-Yamatai "Yay, my Empire is strong and safe" and the more GM-concerned me going "Crap, not enough vulnerability to have shit happen". Of course, I've always been able to squeeze in a way to make that work, but those usually need to tie in to inside-jobs to compromise security since there's no other narrative choice - Yamatai's defenses are too perfect otherwise. Having a standard of 25 active warships (on patrol) a whole system would leave more gaps to exploit (lots of planets), me thinks.

Meh.

As you might see, I'm more GM narrative oriented. I don't think we need exact science. But I'd like justifiable science fiction excuses that would be consistent across the board for the experience we mean to offer. Combat/orbital speed, in-system cruise and intra-system FTL being set down is one thing, but weapon and sensor ranges will need to be adressed too. For weapons, it's mostly accuracy and delay to impacts that need to be considered; and there's sensors so that we can figure out how soon people can see something to react to it... and then run that data through several star system example so that we're fairly sure that the experience holds up to scrutinery.

Lastly, I'd just like to state that I'm pleasantly pleased that we have a constructive and open discussion on this. I didn't expect this to come out in as cooperative a brainstorm as this presently is.

 

[Arieg]

Fun fact, using its hyperdrive system a Plumeria class starship can cross the disc of the Milky Way Galaxy in 12 weeks, thats 120,000 LY.... dat speed problem we have XD

 

[CadetNewb]

That's frightening Arieg.

Anyways, the higher STL speeds would give us more knuckle clenching moments, but I think it would harm us long term. It's the same issue as our short travel times between systems - if we are able to react too quickly, then nothing can develop, limiting what a GM can do to stir up trouble for the players to face. At the same time though, taking half a day to get to another part of the system creates a different kind of tension. It's the "NONONONONO! I CAN'T GET THERE ON TIME - SHE'S GUNNA DIE!" type. The one that gives frustrated horror where a characters watch something unfold, and are helpless to intervene.

As for combat at large fractions of c, I like how "The Lost Fleet" and some of the harder sci-fi books tend to do it. Ships have to Decelerate to attack speed so that the effects of relativity don't screw over their sensor data, allowing them to fire accurately. Even then, the attack patterns are like elegant slashing or swooping motions. The two opposing forces fly by each other within range of their weapons and only get a few moments to fire before their momentum carries them out of range. They then have to turn around for another run, but if their turn is too aggressive, they'll bleed off too much speed, wasting that kinetic energy and end up slowing down.

At which point it can turn into a nasty knife fight if both sides insist on doing that. Fleets did the same thing, but made use of formations to focus firepower and defend themselves. Opposing fleet commanders had to figure out what 'moves' they wanted their fleet's sub-formations to do to set up what firing angles they had during the contact envelop and try and outsmart their enemy so that they could hit their formation's vulnerable points while keeping themselves safe. The contact envelop for them was just a brief milisecond, but for us in SARP, it's a lot longer considering the guide to maximum effective range of weapons we got. Maybe 5 seconds or more if they're doing attack runs like this at .2c.

I think that how a fight unfolds here would be similar, but with certain distinct differences. It's almost like a whole bunch of different tonnage fighters doing gun runs in firing passes basically.

Energy weapons still have bloom though, even lasers, so their range is medium. Kinetic energy weapons are still very effective and have the most 'punch' thanks to the simply larger amounts of matter involved, but due to their lower projectile velocities in general, are more comparable to shotguns - short range but devastating. Meanwhile, guided munitions like missiles and torpedoes have the most range thanks to their propulsion systems and have the ability to track targets, but are the slowest out of them all and can be shot down.

That's my bet on how fights would work out, because even though the ships are capable of getting into an aggressive, space opera-like 'dogfight', it's basically going 'all in' at that point. Too risky. Hence, the 'boom and zoom' tactics.

 

[Rattenkind]

At the same time, if Hanako were trying to get to one of the outer rim planets like Neptune, and it just happens to be all the way on the other side of the system when she arrives, that's another 30 AU she's got to travel across. That's another 4,500,000,000 kilometers, which will take 11 more hours. In this second scenario, it would be 2 Days, 9 Hours and 18 Minutes I think.

In that case Hanako's astrogator or whoever plotted that course would have screwed up by the numbers and is in for a major dressing-down. Anyone calculating a hyperspace fold should be able to calculate the current position of a known planetary body and leave hyper at the closest possible location. Planets don't exactly move at random.

I actually like the version of the heliosphere as the border for FTL travel. For once it slows down interstellar travel for a ship first has to reach the systems 'hyper limit' to go to FTL thus avoiding the paradox that you could pretty much travel to another star system faster than you could travel half way around the planet you started from.

Further more it gives military operations more depth. Anyone invading a system would have to bare in mind, what his targets are, how to approach them in least time, where the defenders would most likely be positioned and who could get there in time to stop you. And you would have to think about getting back to the 'hyper limit' if things should go south on you.
On the other hand the owner of the system has to think about the deployment of his forces. The main sites to defend, like the main inhabited planet or mining operations in the asteroid belt, are most likely hours or days inside the 'hyper limit' thus forces stationed their take time to get anywhere else, e.g. to reinforce another star system under attack or to defend incoming or leaving freighters. On the other side you can't expose these locations to have you main force at the 'hyper limit' to react quickly, for if a hostile force attacks from the other side of the system you may have not enough force in range to intercept them from causing major damage to your system. And catching them in the end before they can FTL out again is a bitter comfort if they nuked your planet to stone-age before.

And there definitely would be room for piracy, having the pirates just lurk at the least-time-approach-loaction of the 'hyper limit' until an innocent merchant drops out of hyper right there fat, dumb and happy because of cause he doesn't want to add more flight time to his trip than he has to. Or they lurk some along the route from the planet to the 'hyper limit'. Richer star systems like Yamatai may have the military capacity to actually patrol this route but I think most less developed colonies or outposts don't.

Therefor I'm quite in favor of having a 'hyper limit' far enough out to actually have a common flight time of hours and days inside the system. If this stretches the plots to far GM can just easily skip it, but I think it can't hurt to actually emphasize the amount of travel time once in a while.

If the heliosphere is to far out though we may just define the 'hyper limit' independently from the heliosphere or hill sphere of a planet, yet still have it bound to the gravity of the central star. We may just define the 'hyper limit' Sol as one light hour or something like that and the 'hyper limit' changes straightly proportional to the mass of the star. That would set the 'hyper limit' of the Yamatai star system to 1.4 lh, which would still give a Plumeria a flight time of just over three hours to actually reach the planet Yamatai. The outer planets would be outside the hyperlimit though.

Concerning the actual sublight drive systems I would actually favor non-inertialess drive systems, because accelerating instantaneously to a third the speed of light just makes the physics student in me cry in agony. When you travel in space, the maximum velocity (which there would still be if just because you can't reach the speed of light) shouldn't mean much compared to the maximum acceleration you can pull (which might be restricted by either the engine output or the maximum output of your inertia compensator). This would also add the pretty important position of the astrogator aboard a star ship who calculates the course of the ship, because acceleration time equals deceleration time can make things pretty interesting if you screw this up.
But I don't think that that suggestion finds much support here, because it would actually complicate things a lot.

PS:

That means that it's going to take 1 day, 20 hours and 48 minutes for Hanako to get to Earth, assuming the Eucharis just arrived in our Solar System.

But the on board clocks would only show something about 1 day 17 hours 32 minutes. At a third the speed of light the time dilation is already quite noticable.

 

[BionicSamurai]

What happens to inertia when the spacetime directly interacting with your ship is what's accelerating?

 

[Rattenkind]

I guess you mean something like creating a pocket universe around your ship and you accelerate this pocket universe?
I think there wouldn't be any inertia as the ship itself doesn't really move. But I also think this would take the ship out of the normal universe thus making it impossible to interact with it in any way whatsoever. I wouldn't consider this helpful for any RP.

That is if I understood you correctly.

 

[BionicSamurai]

But then FTL would be breaking a few laws.

 

[Rattenkind]

Err... FTL is breaking a few laws. That's why it's science fiction. And my last post was of cause hypothetical.
But my suggestion to use inertia-restricted drives was related to sublight drives not FTL drives.

 

[Fred]

Inertia control isn't going away, but it doesn't mean it has to come free.

That snippet aside... personally, what bothered me the most was the matter of escape. Emerging from hyperspace at the edge of a system to travel for a bit was fine. Travel time to reach destination (planet) also fine. Going to a place, regardless of speed, is generally fine.

Unless it's an emergency.

Or unless it's a pursuit scene, which can go both ways. Either the PC-side is pursuing, or the PCs are actually fleeing. Either way, it's a loooong wait to reach the hyper-limit and be potentially home-free from there.

 

[BionicSamurai]

@Rattenkind - We have a whole faction where most of the characters can do this. It would be easier to deal with predictable inertia of objects in a room.

@Fred - The Plumaria-Class Medium Gunship can manage .375c with sublight engines. At that speed, we're looking at covering the distance from the Earth to the Moon in under 3.5 seconds; leaving Earth's hill sphere would take less then 14 seconds. This does not account for acceleration, but it doesn't mess things too much if you go with a shorter range FTL exclusion zone.

I do agree, however, that a large exclusion zone would be less useful in single plot RP as it typically relies on at least a little adrenaline. The only people who currently get off on 7 - 20 minute wait times are mission flight controllers in Houston and I don't see that many people here being of that type. It's great for larger scale, RTS style play where you're controlling a whole armada; but I haven't seen us do much of that here.

 

[Fred]

.375c is the cruising speed. It does not mean that you can afford to go at that speed all the time.

This applies only to my plot:
My ship has aether plasma thrusters and gravimetric drives. The gravimetric drives are what helps make space 'slipperier' - in effect, my thrusters boast more effective movement compared to restraints of mass and acceleration. If the gravimetric drives go full out, then thruster mobility becomes irrelevant and the ship simply falls in a direction at somewhere around a third of the speed of light.

Fast, yes. Well, potentially very fast. And Earth's Hill Sphere is kinda small too so on that scale it's a large amount of terrain covered. Visually, it's practically warp speed.

But. If your ship is around a planet, it's not to zip around at sublight all the time. And...

When my ship is cruising, the gravimetric drives are functionning for movement, which means their function to provide a graviton-based protective shell (commonly called "barrier" in my plot) is next to nonexistant. Since the ship is moving at that speed, the fold drives are also quiescent - most of the power is off feeding the systems that are doing the actual work - and merely serve to provide the small distorsion field necessary to deflect microparticles and ward off radiation hazards.

My ship is unprotected. If I want my protections up, I have to repurpose my systems. I need the fold drives to have power shunted into their capacitor coils and hold that charge - how long my reserve power lasts will depends on that - I have the fold drives themselves put on hot stand-by "if sensors see a shot coming, deflect it!" and the gravimetric drive is the same way too, readily to generate a field.

There's no way of feasibly hurting a forcefield - it's energy you project out, there's no way to render it at "50% capacity". Power reserves, though, can be finite and that's what I use as a medium of showing protections depleting. Last minute surges of power to erect the protection is well within the means of quantum computers.

So, when my ship is cruising with minimal protections, it is where it is the most vulnerable to the weaponry that can catch up to it - directed energy via lasers, particle beams, or graviton beams (the latter is significant - if you're stuck in a graviton beam, you're interdicted; no FTL for you). So, if you're going to be ready to defend yourself, or attack, either way it involves being dragged down to thruster only. And our ship thruster speeds are probably about equal to the escape velocity required to escape the gravity of planets said ships are supposed to take off from. I haven't a clue for now; the in-my-head mental picture is space orbiter shuttles... but we'll probably be faster (i.e: we need 60 km/s to escape Jupiter's gravity).

* * *

Now, I said a bunch of stuff. Why?

Because I agree that the Earth's Hill Sphere makes for a pretty good sandbox for such a system. A gas giant like Jupiter, though, has a much bigger sandbox. About 53 million kilometers, I think I've read.

A 53 000 000 km radius.

Light speed is about 300 000 km/s, so a third of that is 100 000 km/s. 530 seconds for someone outside Jupiter's Hill Sphere to zip full sublight suicidally towards the gas giant. Nearly 9 minutes. That's actually not so bad until you include combat with the model I raised above.

But then, if you're escaping and reach the exterior of the Hill Sphere, right now you've got a chance to have your fold drive charge up and escape. But if the hyper-limit is actually the heliosphere, there's no "Warp speed now!" quote that's appropriate (Chekov, Star Trek 5). You're still stuck somehow limping out of the system at the "nnnnngh"-worthy slow speed of a third of the speed of light.

Apparently, if the fold drive stops at the periphery of the star system, it mostly means that something about the transposition-phenomenon involve doesn't like messing around with solar winds. So, it's the thing in between leaving an hill sphere and reaching the edge of the system which seems like the tricky point. I know we could say "we'd just fold slower" but then travelling from point A to B in fold makes the distinction irrelevant: fold is teleportation. There's no interception possible in the meantime. If you want strategically meaningful travel, it needs to be linear.

Normally, that void could be filled by CDD. But if we are actually going to sincerely rethink how FTL works, I thought we could also cover how Wes wanted Hyperspace Fold to be the only means of FTL Yamatai used. If Fold stops at the Hill Sphere, that works. If Fold stops at the edge of the system, it doesn't.

So far, the only thing I can come up with is how the sublight drive could supercharge to three-fourth of lightspeed. But that still drags out a pursuit scene. But Earth is 121 AU away from the Heliosphere. 121 AU is about 8 light minutes. It'd take 16 long hours to leave our solar system that way.

I got nothing more for that at this moment.

 

[CadetNewb]

This looks to be a tough spot.

If FTL is limited by the Heliosphere as Wes said it was, the 'strategic game' is actually in a somewhat ok state, but at the cost of the 'tactical game' that GMs rely on. Meanwhile, if FTL was reliant on individual planetary Hill Spheres, GMs would get to narrate more exciting escapes and pursuits at the cost of making planetary bombardment quick and easy. I know that with Jupiter's hill sphere the approach to impact would be 9 or 10 minutes, but the Hill Sphere for Earth is 1,500,000 km, and going at 100,000 km/s (~0.3c) that's 15 seconds to doomsday.

I know it's been a while since we last discussed this, but am I missing something? Why are we talking about something with a very large Hill Sphere like Jupiter when planets of interest will be more like Earth?

 

[Fred]

Because space has both extremes, and it'd be shortsighted not to account for them both. An habitable world could actually be the moon of a gas giant with a much bigger Hill Sphere.

Also, I don't intend to let projectiles and guided warheads go nearly as fast as a laser beam if most combat ends up having ships fighting while flying at 60 km/s. Railguns and torpedoes will need to have delays to impact that actually works with the ranges we would be dealing with.

 

[Aendri]

An interpretation I've favored in the past is that you can FTL your way OUT of something like hill spheres, but not into one. The general idea being that when you're LEAVING a hill sphere or heliosphere, you can properly account for the things that would give you trouble coming in, since you're leaving them behind, and you can map them with your sensors. It can't be done reliably going IN simply because you don't have that on the spot sensor information. This leaves the possibility of attempting to FTL into the region, with the caveat that you're basically playing russian roulette, and hoping you don't FTL straight into something that will screw you up. This allows for plot stuff, like crash jumping back into a system that's under attack, knowing you're running the risk of not making it, but knowing you definitely won't make it in time if you don't. Think the Battle of Manticore from the Honorverse series, where they made the chancy jump to land inside the normally interdicted range, and got lucky with most of the ships surviving the jump. This explains the usual avoidance of jumping into spheres, gives people a good excuse to not spend forever leaving, and keeps both a strategic and tactical element there.

 

[CadetNewb]

That's actually a very good idea that I hadn't thought about. Would jumps out of a system also take random amounts of additional time due to 'calibrations' too? That'd give GMs a lot of good room to work with.

 

[Aendri]

Yeah. Like I said, it's based on you actually taking the sensor readings actively to accommodate them. Takes a bit longer to plot that normal, but it allows for speedier exits from the area. Presumably you'd have to remain much closer to stationary as well, otherwise the readings would be changing, as well. Potential big benefits, but it would be risky in combat.

 

[CadetNewb]

What do you think of this @Wes ?

 

[BionicSamurai]

I did not factor in habitable moons, there is that issue. Aendri's compromise does sound plausible.

Honestly, the reason I'm interested in this aspect is that it will also guide how I fix star systems when I get to the work stage.

 

[Nashoba]

Well, we could have a primary sphere for around the star say something like 2-3 AU's from the star. That would cover interior systems using our solar system that would mean from Mars in you are stuck with FTL And then Gas giants by their size would have their own considerably smaller spheres. It would allow for in system FTL in the space between.