Limiting size of Jump capable ships

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Wil Mireu
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Re: Limiting size of Jump capable ships

Postby Wil Mireu » Thu May 01, 2014 12:26 am

phavoc wrote:Missiles are actually kind of under-whelming against true naval combatants. Combine your nuclear damper with decent armor and you can shrug off missile attacks. Without an ablative affect you can wander into a firefight and just thumb your meson cannons against a missile-armed attacker.
Missiles will still tear ships apart just from their kinetic impact effects - armour doesn't grant immunity from that.
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Re: Limiting size of Jump capable ships

Postby sideranautae » Thu May 01, 2014 1:04 am

Wil Mireu wrote:
phavoc wrote:Missiles are actually kind of under-whelming against true naval combatants. Combine your nuclear damper with decent armor and you can shrug off missile attacks. Without an ablative affect you can wander into a firefight and just thumb your meson cannons against a missile-armed attacker.
Missiles will still tear ships apart just from their kinetic impact effects - armour doesn't grant immunity from that.
All depends on how much armor vs. how much K.E. A ship that accelerates for days at 6G's (velocity?) and is hitting micrometers (x mass?) and is not damaged (with no armor rating) will have a certain ability to shrug off kinetic impact effects. NOW, add an armor rating on top of that... I'll do the calculations before I'm done with my rule set so I can determine other items. Namely k.e. weapon effects from vehicle and man portable stuff on ships.
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Wil Mireu
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Re: Limiting size of Jump capable ships

Postby Wil Mireu » Thu May 01, 2014 1:08 am

sideranautae wrote:All depends on how much armor vs. how much K.E. A ship that accelerates for days at 6G's (velocity?) and is hitting micrometers (x mass?) and is not damaged (with no armor rating) will have a certain ability to shrug off kinetic impact effects.
Keep in mind that this is one of the many aspects of Traveller is a complete and utter fantasy. That said, it's only likely to be an issue in orbit around a planet where there's more chance of running into a stray paint fleck or leftover bolt.

Then again, mass and fuel aren't a factor in Traveller ship design or movement anyway, so you may as well make up whatever you want given that two of the primary things that serve to limit ship design aren't actually a factor in the entire process. ;)
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Re: Limiting size of Jump capable ships

Postby sideranautae » Thu May 01, 2014 1:19 am

Wil Mireu wrote:
sideranautae wrote:All depends on how much armor vs. how much K.E. A ship that accelerates for days at 6G's (velocity?) and is hitting micrometers (x mass?) and is not damaged (with no armor rating) will have a certain ability to shrug off kinetic impact effects.
Wil Mireu wrote:Keep in mind that this is one of the many aspects of Traveller is a complete and utter fantasy. That said, it's only likely to be an issue in orbit around a planet where there's more chance of running into a stray paint fleck or leftover bolt.
Well, the velocity is there in the game. It's built in. You will run into space dust (<gram) anywhere in the solar system. To remain internally consistent, the hulls have to be that tough. Jump drive is also fantasy in Trav but can't be ignored either.
Wil Mireu wrote:Then again, mass and fuel aren't a factor in Traveller ship design or movement anyway, so you may as well make up whatever you want given that two of the primary things that serve to limit ship design aren't actually a factor in the entire process. ;)
Yes, in Trav it is a de facto condition that has to be acknowledged. To ignore how the game operates vis-a-vis space travel is to cause all manner of in-game inconsistencies. So, the best thing to do is look at how the rules say things operate and extrapolate what MUST be reality therefore. Whether it is FLT travel, reactionless thrusters, auto-docs, anagathics, etc.

So, I have to delve into the strong nuclear force. Hello Uni-molecular™ hulls. :)
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Re: Limiting size of Jump capable ships

Postby Tom Kalbfus » Thu May 01, 2014 2:37 am

High velocities would favor larger starships. the bigger the starship the more armor it can carry. A starship's cross section and vulnerability to micro meteors is a function of the square of its diameter, but volume is a cubic function of it, thus room for thicker armor.
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Re: Limiting size of Jump capable ships

Postby sideranautae » Thu May 01, 2014 2:55 am

Tom Kalbfus wrote:High velocities would favor larger starships. the bigger the starship the more armor it can carry.
Doesn't matter in MGT. Unarmored hulls can withstand it.
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Re: Limiting size of Jump capable ships

Postby Condottiere » Thu May 01, 2014 7:10 am

If you tied in speed with structural strength, biased in favour of smaller hulls, you'd add a new dynamic in ship design.
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Re: Limiting size of Jump capable ships

Postby Tom Kalbfus » Thu May 01, 2014 12:57 pm

Thicker walls block cosmic rays and meteors better than thin ones.
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Re: Limiting size of Jump capable ships

Postby Meanderer » Sat Jun 07, 2014 1:12 am

Missiles are actually kind of under-whelming against true naval combatants.
I thought some of the ideas in the Mongoose versions were brilliant and should have been in Traveller all along.

Other ideas here could be built in to a table.

Consider the most famous capital ship - the Lightning Class cruisers. Equipped with squadrons of small fighter armed with lasers that can't do much on the combat tables against other capital ships, and a low maneuver rating which made them seem like sitting ducks. The fighters were called Ramparts (interesting, because a rampart is a defensive construction) and the primary ship armament (other than the big spinal mount) were lots of missile bays.

Mongoose improvement - torpedoes.
Amazing. Missiles large enough to do damage to capital ships, capable of being launched from small craft. Suddenly a wave of heavy fighters can be a threat to a large battleship and having a swarm of fighters to screen the ship becomes necessary, particularly if you can only maneuver at 2G. The Solomani response to nuclear dampers (set off the nuke outside of the area of effect of the damper and channel the explosion into a massive x-ray/gamma-ray laser which is not suppressed by the damper.

Missing: effect of velocity difference. The true power of the Lightning Class as a fleet intruder was in its high jump number. Using Jump 2 or 3, a Lightning Class ship could jump into the outer part of a star system many light minutes away from major targets (maybe 30 light minutes). Enemy ships in the system would have fleet chatter, transponders, etc as well as light and other emissions. This light and emissions will be reaching the Lightning Class where it jumped in from the moment it arrives (just minutes (or hours) out of date) so the Lightning Class can evaluate targets and make a decision whether to attack before the enemy will have detected it (the enemy will detect it on the same lightspeed lag but starting from when it arrived. If you are 30 light minutes from the emergence point you will detect the light reflecting off the Lightning Cruiser and its emissions 30 minutes later).

If the enemy defenses aren't too close or strong, the Lightning Class cruiser accellerates towards the enemy planet. It has only 2G accelleration but for what it plans you don't need a lot of accelleration. It has decent hull armour and goes for a velocity of 5,000 kilometers per second. This takes about 70 hours to reach but the Cruiser has the time. Over this time weapons are prepped, the jump drive is cleared, and a course is plotted. Having only used a portion of its jump fuel it doesn't need to refuel to jump out again. This isn't a surprise attack. This is a kinetic raid. The fighters move ahead of the cruiser to intercept missiles ahead. It has enough ability to maneuvera t 2G that there is no guarantee of a missile interception unless you launch very close to its path and it can fire off missiles and torpedoes ahead at these targets. The fighters are tasked solely with intercepting missiles that may harm the cruiser. It's velocity renders energy weapons moot. The longest range projeced energy weapons go out to 50,000 km. At 5,000 km/second the cruiser crosses this range in about 20 seconds (a 100,000 km spread for the enemy ship to shoot you coming and going). That's much less than a combat turn. If you can get in a position for a shot you only get one chance and probably at significant penalty.

At 5,000 km/second it can cross the 100 diameter limit on an earth sized world in about 8 minutes. That is, again, less than one 15 minute combat round. The Lightning Cruiser has the advantage of monitoring enemy movements and avoiding any dangerous interceptions. A fleet accellerating out at high speed will have to be wary of the Lightning Cruiser's massive missile armament and will be heading in the wrong direction to intercept and follow. It takes a lot of time to match position and course with a fast moving ship and the Lightning Cruiser can jump away as fast as it can land its fighters. It may hold off on launching fighters until it is near an interception to retain the option of a quick escape jump - and may not even need to launch fighters at all. If a fleet is moving against it, it can launch volleys of missiles and jump away.

Devastating. But what if the enemy fleet is approaching at 5,000 km per second too. That would effectively have each missile hitting at 10,000 km per second. You don't need a warhead at that point. 10 kg of iron at this speed will hit with a kinetic energy equivalent of several atomic bombs and no nuclear damper will save you. [addendum: I researched this. A 10kg chunk of iron hitting at effectively 10,000 km/s would have the kinetic energy equivalent of 239 kilotons of TNT. Not a fusion bomb equivalent, but about 15 times the energy of the bomb that destroyed Hiroshima. If it is a missile launched at a planet at 5,000 km/s the energy goes down to almost 60 kilotons or 3-4 atomic bombs]. Missiles can be launched at the planet and left on their course while the Cruiser can jump away. Enemy ships can maneuver out of the way but planets can't. The missile could be launched from a ship at high velocity and use that velocity to get to its target, saving its thrust for pre-programmed evasive maneuvering near its target. Some evasive maneuvering along with extreme velocity would make the missiles very hard to intercept.
Of course the penalties to hit any ship at such a velocity will be enourmous. Bringing energy weapons to bear precisely where the target will be is hard, and this will apply to missiles too. But the penalties to hit with missiles will be large too because the missile cannot maneuver around to try for another intercept. At this velocity it would take hours to decellerate and come back to where the target was.

Basic application of science to what the Traveller rules describe (ships able to accellerate at 2G, 4G even 6G continuously for days, and a 50,000 km range limit for ship's weapons). But the implications can really change the nature of war in the Traveller universe. Logic says that missile velocity must be a factor. But how to make this work?

Also, this makes mass drivers (railguns) an effective weapon even at very high tech levels. Ships that tend to make high velocity raids through enemy systems (the fleet intruder role) may be armed with railguns to use their velocity more effectively.
Last edited by Meanderer on Tue Jun 17, 2014 6:12 pm, edited 1 time in total.
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Re: Limiting size of Jump capable ships

Postby Condottiere » Sat Jun 07, 2014 3:37 am

Stealth torpedoes and drones, courtesy of HMS Weber.
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Re: Limiting size of Jump capable ships

Postby sideranautae » Tue Jun 17, 2014 5:23 pm

I was thinking that maybe 20 ktons was too small of a limit on Jump capable ships. But after reviewing the stats on the Enterprise from TOS I found that it was only a bit over 14 ktons (190,000 metric tons, aka cubic meters).
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Re: Limiting size of Jump capable ships

Postby Meanderer » Tue Jun 17, 2014 6:21 pm

Limits on size of ships has a sort of historical precedent. The naval arms race in Europe led to development of heavily armed and armored battleships that (if I recall correctly) had limited operational range. They remained close to their home ports or could be used in attacks on other European powers directly, but could not be easily sent to the colonies.

Smaller cruisers and gunboats were built to protect colonies, raid colonies and commerce of enemies (in times of war).

A limit on jump vessel size would limit the usefulness of battleships. If the limit is 20 kilotons then any ship built over that size would be a system defense vessel without the massive fuel tanks needed for a starship. A 40,000 ton super-cruiser would be able to outclass any 20,000 ton starship attacking the system and likely be able to engage and destroy multiple starships.

At that rate there would appear little purpose in building a 100,000 ton battleship.

Of course the size differential could be equalized by the attacking vessel arriving in at a significant velocity and using this for an advantage in combat (see above comments on missiles).

It changes the nature of attack and defense significantly.
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Re: Limiting size of Jump capable ships

Postby sideranautae » Tue Jun 17, 2014 6:27 pm

Meanderer wrote:A limit on jump vessel size would limit the usefulness of battleships. If the limit is 20 kilotons then any ship built over that size would be a system defense vessel without the massive fuel tanks needed for a starship. A 40,000 ton super-cruiser would be able to outclass any 20,000 ton starship attacking the system and likely be able to engage and destroy multiple starships.

At that rate there would appear little purpose in building a 100,000 ton battleship.

Of course the size differential could be equalized by the attacking vessel arriving in at a significant velocity and using this for an advantage in combat (see above comments on missiles).

It changes the nature of attack and defense significantly.
This would be a natural limit (natural physical law). I agree on all your points above. Since I don't allow inertia to cross between N-space & J-space it changes even more. It would appear to make interstellar invasion more difficult, all else being equal.

I am also tweaking Jump so it will be harder to defend an area as striking deeper will be possible.
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Re: Limiting size of Jump capable ships

Postby locarno24 » Wed Jun 18, 2014 9:43 am

As long as you're at 10,000 dTons (destroyer/light cruiser in 3I terms), you're quite capable of packing spinal weaponry (the only real game-changer that capital ships have at their disposal), so you're not losing much tactically.

Being able to have 20,000 dTon monitors based on buffered planetoids that you can't shoot through jump hands an advantage to a defender capable of fielding them - because once you get into capital ship combat with barrage fire, ships tend to fight at full effect until destroyed unless they take hits from spinal weapons.

That said, very few places will want to build a cruiser-scale defence craft that doesn't go anywhere (strategically), so it's probably not going to matter for anything other than your sector capitals and major naval bases.

The fact that your fleet is mostly built around destroyers and lighter ships with the odd light cruiser does affect warfare a bit - the big issue with smaller ships is that you can't have everything; putting in Jump-5 capability on a ship (the usual requirement to qualify for the 'Strike' designation) occupies a minimum of 60% of the ship with jump drive, power plant and sufficient fuel. That means that any strike-capable ship (or frontier destroyer, rift destroyer or any of a half-dozen other designations) is going to be somewhat underwhelming in a fight and not able to engage hard military targets, because either it's significantly short on armour, sublight acceleration or firepower for its displacement.

Granted, the same is true for strike battleships in the current rules, but the thing is that a 100 KdTon battleship, even if it's hampered by limitations, is still a potent enough unit to handily hoof a SDB squadron in the pods.

Yes, all right, you could field a squadron of strike destroyers, or a whole flotilla, but they're going to take proportionally worse casualties due to the compromises - the size limitations, for example, start to impact your ability to carry spinal weapons.


That, in turn, is going to push battles to be more fights "at the battle line", limiting a fleet's ability to strike deep into enemy territory.


Meanderer:
1) note that a combat round is 6 minutes in MGT
2) Bomb-pumped laser torpedoes are nasty, but should logically then be partially degradeable via sandcaster fire.
3) The major problem of the AHL cruiser is this: yes, you could jump out and perform a 'fast fly-by' of the system, but what are you intending to achieve? If your target is anything but 'static' - i.e. carpet-bombardment of the planet itself, the same targeting problems apply to you too.
4) Any counter-fire will have the same velocity advantage against the AHL - kinetic energy doesn't care if the additional impact is due to you closing on it at 5,000 km/s or the other way around; the mutual total closing velocity is all that matters.
Understand that I'm not advocating violence.
I'm just saying that it's highly effective and I strongly recommend using it.
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Re: Limiting size of Jump capable ships

Postby sideranautae » Wed Jun 18, 2014 12:42 pm

locarno24 wrote:As long as you're at 10,000 dTons (destroyer/light cruiser in 3I terms), you're quite capable of packing spinal weaponry (the only real game-changer that capital ships have at their disposal), so you're not losing much tactically.
Ah, okay. So 20 Kt isn't THAT bad.
locarno24 wrote:Being able to have 20,000 dTon monitors based on buffered planetoids that you can't shoot through jump hands an advantage to a defender capable of fielding them - because once you get into capital ship combat with barrage fire, ships tend to fight at full effect until destroyed unless they take hits from spinal weapons.
There's no limit to non-jump ships. Well, no rule limit anyway.
locarno24 wrote:That said, very few places will want to build a cruiser-scale defence craft that doesn't go anywhere (strategically), so it's probably not going to matter for anything other than your sector capitals and major naval bases.
Yes, logical not to waste Cr on stuff that can't also project power.
locarno24 wrote:The fact that your fleet is mostly built around destroyers and lighter ships with the odd light cruiser does affect warfare a bit - the big issue with smaller ships is that you can't have everything; putting in Jump-5 capability on a ship (the usual requirement to qualify for the 'Strike' designation) occupies a minimum of 60% of the ship with jump drive, power plant and sufficient fuel.


I changes the J fuel to 5%. I also decoupled the PP from the JD. JD has its own power.
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Re: Limiting size of Jump capable ships

Postby Meanderer » Wed Jun 18, 2014 6:38 pm

Meanderer:
1) note that a combat round is 6 minutes in MGT
2) Bomb-pumped laser torpedoes are nasty, but should logically then be partially degradeable via sandcaster fire.
3) The major problem of the AHL cruiser is this: yes, you could jump out and perform a 'fast fly-by' of the system, but what are you intending to achieve? If your target is anything but 'static' - i.e. carpet-bombardment of the planet itself, the same targeting problems apply to you too.
4) Any counter-fire will have the same velocity advantage against the AHL - kinetic energy doesn't care if the additional impact is due to you closing on it at 5,000 km/s or the other way around; the mutual total closing velocity is all that matters.
I stand corrected on the combat round length. Too used to the old Classic traveler rules I guess.

That said, your points about how the space combat rules stand because the space combat rules are horrible at factoring in kinetic energy. Lasers and particle accelerators aren't much affected by how fast a ship is going. Missiles and railguns are. And while missiles only have limited burn time, they can use velocity imparted by the launching vessel to get to the target (ie. Missiles start with the same heading and speed as the launching vessel). So if you are heading towards an enemy force that is moving to intercept you, you can launch a full spread of missiles that continue to travel with your vessel, launch another, and then when you launch a third you get them all accelerating on an attack vector against those enemies. High velocity combat requires some planning ahead but at these velocities the relative impact of acceleration is limited. In 3 turns (18 minutes) a 6G destroyer will be able to change it's speed by about 21 km/s. If you are coming in at 500 km/s you will be able to plan fairly well where that enemy destroyer will be able to intercept you, and when. The AHL can also plan if it needs to launch its fighters. It can launch missiles of its own, but won't be on precisely a head-on vector and both forces will be maneuvering. There should be substantial penalties for the velocity and maybe more penalties for the destroyer choosing an attack vector that limits its exposure to the massive missile volley from the AHL. Maybe they pass through with no effect. A hit with a 10kg mass will be 600 tons of TNT. I wonder how many spinal mounts equal that power. But you have to hit directly and missiles that miss won't be able to turn around and try again.

I think the AHL is fairly survivable in such engagements, though it would avoid them as much as possible.

So what can you achieve if engagements with enemy forces are generally so inconsequential?

Well, fleets run on supply lines. Replacement munitions, food, parts. The AHL is extremely useful as a raider. Destroy orbital stations and you cut down on a planet's ability to refuel fleets in orbit as well as impacting trade in general. If you destroy or significantly damage naval bases on an enemy fleet's supply lines - how much will this impact the movement and fighting ability of the enemy fleet? In the old GDW game "The Fifth Frontier War" each side gets replacement points they can use to restore damaged squadrons and bring armies back up to full strength. Hitting the naval bases that are supporting a fleet should destroy some of those "replacement points". And that still doesn't touch on the value of these stations as major trade hubs that the planet will desperately want to have after the war. These are strategic targets that must be defended.

You don't build a ship with half it's volume made of fuel tanks to stand in the line of battle and trade blows. You build it as a threat to your enemies and to bleed off the enemy's fleet strength accordingly.

Vessels kept near the main planet to defend against raiding fleet intruders (1) cannot be also positioned further out to keep enemy fleets from refueling at the local gas giant and (2) can't be parsecs away with your fleet.

One squadron of Jump 5 fleet intruders may significantly threaten a number of key industrial worlds. Sent out on a raid it would be commanded by an admiral who is able to use its mobility effectively (since it is almost or as fast as the enemy high-jump scout/courier vessels, it can travel as fast as information on its location and faster than the enemy can shift defensive forces around to respond to it. And most major powers can build vessels like the AHL. These ships are TL14. The Zhodani have their own equivalents.

So if you need a couple of squadrons to defend the orbital facilities this means that a half dozen key worlds will need to station the equivalent of 12 squadrons to defend against that one fleet intruder squadron. It has already taken more than its weight of enemy vessels out of the battle without firing a shot. Now reconfigure them to launch dead-weight kinetic spears from a velocity much higher. At 5000 km/s a 50 ton kinetic spear will have TNT energy equivalent of 298 megatons. Why can't a 60,000 ton cruiser be configured to carry and launch a few of these weapons? How many would there be in a cruiser squadron? And if the speed is 10,000 km/s the equivalency becomes about 1.2 gigatons of TNT (half the USA's entire nuclear arsenal for each spear) . These are strategic weapons of mass destruction. Can you see them coming? Maybe if you can detect and target them with nuclear missiles you can save the planet, but you need to hit each one individually (and a conventional missile hit probably would not be enough). Just a few get through and the impacts will cause massive surface damage (the spears would be made of dense hard material - hull metal - and will not burn up in the fraction of a second they penetrate the atmosphere) and bring on the effect described as a nuclear winter.

How do you defend against such an attack? Easy. It needs to build up that attack vector before it jumps and it needs to jump from within two parsecs to have enough fuel to jump back out after lining up its attack run (there is no slowing down to refuel at a gas giant when you jump in hot at 5000 km/s or more). So you station squadrons at all worlds within two parsecs of the major world you are defending and voila the fleet intruder's can be kept back unless they can defeat those squadrons. But again you may need to maintain these defensive squadrons at each refueling point at those neighboring worlds so you may need 3 or 4 squadrons to keep that AHL squadron from using the system as a staging area. In the Spinward Marches, the Regina system has 8 systems within 2 parsecs range that have gas giants. So if you dedicate even just two squadrons to each and another four to Regina you have 20 squadrons tied down to defend one major world, and 80% of them are kept outside that major system so they aren't available to defend it if a major fleet comes to attack the Regina system. And that is just Regina. Other worlds would need defending too.

And every major world will have its government and population clamoring for this defense. Strategically the navy may want to say no, and choose to concentrate forces in fleets they will take on the offensive (because trying to defend is a losing game). But the navy won't be the ones to make that decision just as they don't get to set tax rates and approve their own budgets. Politically it may not be possible to hold on to worlds if you aren't going to make an effort to defend them. They would have to be allowed a larger portion of their GDP to spend on system defense - reducing Imperial taxes accordingly which essentially starves the navy of funds to build/maintain those fleets.

Welcome to the depressing world of strategic missile defense - where the force needed to keep your enemy out of range far exceeds the force you are defending against.

Actually, thinking about this some more it explains a lot about the frontier wars in the Third Imperium setting. You get limited wars without use of the WMDs that can largely wipe out a planet's population because there would be an agreement at some point not to use such weapons and even in times of war neither side wants to provoke the other into using them. So you have relatively small local conflicts where a few worlds may change hands as a result of the war but neither side gets into a total war situation against the other. Neither side would field a force large enough to be percieved as an existential threat on the other (no fleets large and powerful enough to drive on to Core or Zhdant).

I think such a treaty/understanding would prohibit use of the 50 ton kinetic spears I referred to above but would it extend to the smaller lower-velocity projectiles? Would any deliberate targeting of civilian infrastructure be prohibited, but still leaving 500 km/s attacks on orbital naval stations?

The most effective defense against nuclear weapons has always been the threat that the other side will use theirs in response. I think this would come into play with kinetic weapons past a certain point.
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Re: Limiting size of Jump capable ships

Postby sideranautae » Wed Jun 18, 2014 6:46 pm

Meanderer wrote: The most effective defense against nuclear weapons has always been the threat that the other side will use theirs in response. I think this would come into play with kinetic weapons past a certain point.
Not really. KE weapons are too easy to defend against. That has already been laid out from a physics standpoint with no credible counter argument.

Also, non jump capable defenders on a cost & tonnage basis will slaughter Jump capable raiders.
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Re: Limiting size of Jump capable ships

Postby Meanderer » Wed Jun 18, 2014 9:08 pm

Space is big. You have to see the target coming and be able to calculate its speed, vector and location with great precision.

a 50 ton kinetic torpedo made of material twice as dense as steel would be about 3 cubic m in size and have zero emissions. You would have to have its velocity and vector exact to do an intercept and even then you need to deflect its vector enough to make it miss the planet. Do this far enough out in the system and a conventional missile could do the job. Do it too close and it doesn't work. If you can make a starship stealthy it should be easier to do this with a solid chunk of metal. Sure it will show up on a densitometer but they don't have long enough range for this.

Let's say you intercept it with a conventional missile travelling at 500 km/s with a 10kg warhead the effective energy may slow it down 7 km/s or push it off course by an equivalent vector. If you do this more than 4.5 million km out that may be enough to make it miss the planet. If you crack it in two remember that aerodynamics is not important. Reduce it to pieces the size of gravel and that is still 300 megatons of gravel hitting the planet. I think you need a nuke hitting it if you intercept it with something launched from planetary orbit.
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Re: Limiting size of Jump capable ships

Postby Meanderer » Wed Jun 18, 2014 9:12 pm

sideranautae wrote
Since I don't allow inertia to cross between N-space & J-space it changes even more. It would appear to make interstellar invasion more difficult, all else being equal.

I am also tweaking Jump so it will be harder to defend an area as striking deeper will be possible.
I changes the J fuel to 5%. I also decoupled the PP from the JD. JD has its own power.
There has to be some mechanism to preserve inertia in vessels jumping or you have a ship jumping into our solar system at a velocity of zero meters per second watching the entire solar system moving away from it at about 220 km/s. Our sun has this velocity as it orbits our galactic core along with the other stars in our spiral arm. Or this may just mean that ships jumping in need to accelerate to match speed with the solar system as part of getting on a vector to achieve orbit at a destination planet. Accelerating up to 220 km/second will take a tramp merchant ship 6 hours at 1G. It is do-able. But this still leaves systems open to a weaker kinetic attack by jumping in the path of the planet at zero velocity while it is moving towards you.

I always treated the motion of the spiral arm as effectively zero as star systems in the arm would have similar orbital velocity so you just don't factor in that velocity and vector. You could build the same thing by assuming local jumpspace is moving (since planets and stars seem to project a presence into jumpspace based on their size maybe they are also imparting a velocity on local jumpspace). This means you don't actually hit zero inertia so much as match velocity and vector with a calculated velocity/vector of local jumpspace (with a possibility of misjump and/or damage if you aren't on the right vector when you jump). So you emerge from jump with a velocity around 220 km/second which would be close to standing still relative to the movement of the local star. Just have to catch up with a planet travelling around 30 km/s.

Your proposals have some very interesting implications.

Reducing the size of fuel means that virtually every military vessel designed to be on the attack will have a jump capability at the maximum allowed by its tech level.

At 25-30% fuel requirement, why not give that 10,000 ton attack cruiser jump 5 or 6. Fleets start to move faster relative to the speed of communication so if a fleet can keep refuelling and jumping fast enough it can hit a target system within a few days of word arriving that the war is started. More surprise attacks and a greater need to maintain more forces in battle readiness and deeper into your territory. Getting a Zhodani fleet from Zhodani space to Rhylanor on a direct route is an exercise in planning. The fleet is stuck at jump 3 and you need to have systems ready for refuelling. If you have a lot of tankers and have an advance force stationing tankers along the route (assuming you can defend this lifeline as you go) you can get that fleet to Rhylanor in about 10 jumps (10 weeks according to the rules for The Fifth Frontier War; but I think fleet logistics and need for scouting information would require turns in that game to more correctly represent 2-3 weeks - so half a year to get from Cronor to Rhylanor. The Imperium would be getting reinforcements before that fleet can arrive. But if that fleet can go Jump 5 the logistics become much simpler. Plotting jumps from their naval base at Quar, the Zhodani could reach Rhylanor in just 4 jumps with a jump 5 fleet , potentially arriving before any reinforcements arrive and that would be considered a deep penetration attack on the Imperium's border. Defenders can theoretically use their own high jump capacity to get ahead of the enemy fleet and block their path, but the limits on FTL communication come into play. The first jump into Imperial space along the route I plotted was a low tech mining system - Dinom. By the time word reached Regina that the Zhodani were there they would already be jumping off to Pirema. Maybe if there is a fleet in Regina that can move on a moment's notice they might jump and catch the Zhodani there. Assuming that Jump 6 military scout/couriers are not held back by fleet logistics and can quickly do a gas giant skim and jump again (or communicate to another courier in system if the system has a naval base, which jumps immediately) this means that word might reach Rhylanor 2-3 weeks after the invasion while that Zhodani fleet would arrive 4-5 weeks after the invasion starts. Not a lot of time to call for reinforcements and repair particularly when the Imperium doesn't know where that fleet at Dinom is going (Dinom is an excellent place to launch an attack on Regina from.

It actually gets harder to defend because you will have less ability to predict where the enemy is (delay in FTL communication all news arriving from starships is old) and even less to predict where they are going.

This turns the problems defending against fleet intruders and turns it into a general defensive problem as you can't get sufficient warning to concentrate forces. Under current rules, military scout/couriers may travel at Jump 5 or 6, while fleets are typically constrained to jumps 2-4. But if fleets are travelling at the same rough speeds I don't see how a defense can be coordinated. In the example above, the Zhodani fleet at Pirema is within one jump from Rhylanor. But you get only one week's notice that they are there and you don't know if they are going after Rhylanor or the bases at Risek or Macene or Jae Tellona or Icetina or some other world in the area. You have to figure out what you need to hold a specific world and keep those forces there.

And this makes the fleet intruder role even more dangerous. A ship in the fleet intruder role would be given sufficient resources to be able to operate for a few months without fleet support. This will allow it to jump as fast as the military couriers so they can arrive as fast as news arrives. And since they only need 25-30% of their volume as fuel they won't be at much of any disadvantage against defending vessels on a ship to ship basis. They would have 6G drives and full armor. It takes about 24 hours to accelerate to 5,000 km/s from further out in the system and it takes time to get ships moving. And time to build up velocity for an interception vector. The fleet intruders could accelerate, launch WMD kinetic torpedoes and jump out before they can be intercepted. That leaves a mad scramble to intercept the WMDs. And keep in mind that 50 ton kinetic torpedo I mentioned is just a solid piece of metal. If bonded superdense is twice as dense as steel ( I think it is at least this), then a 50 ton torpedo made of this material would be just over 3 cubic meters in size. Perhaps a 16 m long cylinder approximately a half meter in diameter. Zero emissions. Incredible speed. Very small target.

At 2 hours 20 minutes to accelerate up to the more modest 500 km/s attack velocity and the ability to decelerate afterwards in similar time means a kinetic sneak attack on orbital facilities is possible. Imagine an AHL ship with robot fighters programmed to accelerate towards an enemy world and collide with orbital targets. The AHL doesn't even need to accelerate to attack speed. It jumps in about 2.5 million miles out from the enemy world, launches fighters and jumps away. The fighters can be programmed to evade missiles and ships within energy weapon range so they may be difficult to hit and each will hit with the equivalent of 0.8 megatons of TNT.

Very hard to defend against either type of strategic attack. Wouldn't this end up as a cold war where each side would have strategic attack weapons poised to do horrific damage to the enemy and no one dares let even a limited war start? (indirect wars between client states would be a different matter, maybe with each client state kept in line to not use strategic WMDs to avoid escalation of the conflict). Interesting.
Meanderer
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Re: Limiting size of Jump capable ships

Postby Meanderer » Wed Jun 18, 2014 9:36 pm

Also, non jump capable defenders on a cost & tonnage basis will slaughter Jump capable raiders.
If you stand and fight.

A ship jumping in with a reasonable attack vector and velocity wouldn't need very many hours to jump in, make course corrections, launch and jump out. Not much time to send anything to intercept.

If you require zero relative inertia to jump it needs about 3 days to get up to the WMD speed of 5,000 km/s.

If it does this far out in the system (outside Pluto's orbit if attacking Terra) it isn't possible to intercept them with a ship launched from Terra at 6G before they launch the WMDs. Though you can get there before they can slow down again to jump.

Now as for outgunning them we already established difficulty hitting any maneuvering ship with a missile at extreme velocity enough to render it unfeasible. But there are spinal mounts and turret/bay energy weapons that will work. And that fleet intruder squadron that is decelerating is hit by a squadron going at incredible speed such that - they take one shot as they fly by.

The fleet intruders don't need to be able to stand on the line of battle and trade blows. They just need to survive one round of combat (most likely with extra penalties to hit) because one round is all there is. By the time the interception fleet can slow down and vector to intercept again the intruders will jump out. Even a jump 5 ship may mount meson screens and have armor. You need a one shot kill. How often does that happen.

In the vastness of space the effective weapons range of vessels seems like point-blank. What is 50,000 km when you are dealing with a distance of 8 billion km and speeds that cross weapons range in seconds.

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