[Spaceships] Designing the best possible fleet on a billion-dollar budget

[weby]

Originally Posted by Michael Thayne

I was sick this weekend, so I was a bit slow to tackle this. Weby, not sure I follow your math for missile costs? A 16cm missile weighs 1/15th of a ton, and missiles costs $1M/ton, so a conventional 16cm missile costs ~$67K. A nuclear warhead adds $50K, so that's $117K per missile. So 2,716 missiles should cost ~$317M. I also don't think you have the cost for the missile launchers right—unless this has been errata'd, SM+4 major batteries cost $100K. (Yes, this breaks the usual rule for pricing SM+4 systems for no apparent reason.)

Yes, the missile prices are calculated as 1million/15+25k each.

But weapon prices are apparently wrong *sigh*

I guess I need to ditch the long range acceleration of the drones and just go with HEDM, was trying to give them some staying power, but it is really not needed in this scenario. So reducing those prices and still need to ditch some more missiles it seems. Will recalculate.

[weby]

Originally Posted by Michael Thayne

Particularly relevant to weby's design: under Wait (Point Defense) on Spaceships p. 53, it says, "You can opt to use only some of your RoF; if so, you may attack again with unused shots against further incoming ballistic attacks before the start of your next turn." That seems to imply there is no penalty for splitting your shots between incoming ballistic attacks. Is anyone aware of any reason to think otherwise? Would be good to be clear on before I try to write up some scripts to automate the resolution of an insane several-hundred-drone battle.

The way we have read it is:
-You can split your fire.
-Split point def fire works as any other split fire: a single salvo fired by one attack maneuver is a single target, multiple salvos are multiple targets thus get a cumulative -2(using beams or guns)/-1(using missiles)

That reading comes from the Spreading Fire page 58:

Note that a salvo of multiple incoming mis-
siles or gun shells launched as a single attack do
not count as a different targets

Emphasis mine.

[weby]

Originally Posted by AlexanderHowl

Honestly, drones are better off using HEDM chemical engines. They are relatively cheap and allow for high thrust. An SM+4 drone could just have one HEDM engine, one control room, three sections of armor, five missile ranks with 16cm nuclear missiles, and ten fuel tanks of HEDM fuel and it is a potent threat (with 2g acceleration, it is capable of reaching of reaching 7 mps delta-v). You could have them on an SM+10 carrier, carry only 80 of them, and have a greater volley of 400 per turn.

The reason to have more drones and larger carrier is to force the enemy force to have a lots of things that can take out the drones themselves in large numbers as they are also usable as missiles. Say 500 of 10 ton drones impacting you at any type of speed tends to be problematic for many types of targets.

So it is not only the missiles that just require any hit even from a minimal point defense drone to destroy, but the fairly well armored drones themselves.

But yes, it seems I need to go with HEDM engines as the AM engines are just too expensive.

Also on salvos: You do not want too large a salvo size as a large salvo will produce less hits by far compared to separate attacks and as the missiles are so expensive you would basically want to fire them one by one anyway on separate attack rolls.

[Michael Thayne]

Originally Posted by AlexanderHowl

I think that 16cm missiles weigh 1/10th of a ton, just like 16cm conventional shells, so 2,716 missiles would cost $271.6M plus $135.8M if they possess 25 kiloton warheads, for a total of $407.4M.

My copy of Spaceships (PDF edition) definitely says 1/15th. Frustratingly, though, Spaceships has been errata'd so much that there's a ton of potential for confusion if someone is using a different version. I think my copy has all the erratas though?

EDIT: I think the 1/15th of a ton weight for missiles may have been an errata on the original print edition?: http://www.sjgames.com/errata/gurps/...ceships_1.html

[weby]

Ok, updated the task force to use HEDM on drones and the price of SM 4 weapons.

The drives and fuel being cheaper actually allowed for more missiles to be carried.

[Michael Thayne]

Originally Posted by weby

The way we have read it is:
-You can split your fire.
-Split point def fire works as any other split fire: a single salvo fired by one attack maneuver is a single target, multiple salvos are multiple targets thus get a cumulative -2(using beams or guns)/-1(using missiles)

That reading comes from the Spreading Fire page 58:

Emphasis mine.

Good catch on the ref. from p. 58.

This actually seems to contradict the point defense rules, though. The section also says, "All targets must be specified before rolling to hit." But with point defense, you might not even know how many more attacks are going to hit this round! Does anyone know if David has ever clarified this?

[Michael Thayne]

A serious using tertiary batteries for point defense vs. hundreds of drones is that the beam weapons rules say a system becomes disabled on a critical failure. So any batter—regardless of type—is limited to stopping about 200 attacks on average. This means that probably any effective fleet is going to have to use drones for point-defense.

It might be useful to have a very basic "bubble carrier" design that can easily be dropped into any fleet. This version, built on an SM+7 hull, carries up to 17 SM+4 drones:

Front Hull
[1-6] Hangar Bays (10 tons each) ($180K)

Central Hull
[1-6] Hangar Bays (10 tons each) ($180K)
[core] Smaller Systems (three at SM+6): one Control Room (C7, comm/sensor 5, one control station); one Habitat; one Cargo Hold (5 tons). ($250K)

Rear Hull
[1] Smaller Systems (three at SM+6): one Fusion Rocket (using hydrogen; provides 0.00167G acceleration); one Fuel Tank (5 tons hydrogen provides 20 mps delta-V); one Cargo Hold. ($1.03M)
[2-5] Hangar Bays (10 tons each) ($150K)
[core] Cargo Hold

Empty cost: $1.79M
Fuel cost: $10K
Crew: one bioroid ($200K)

Coincidentally, the whole package costs exactly $2M.

[AlexanderHowl]

Well, turrets function independently as they each have their own dedicated firing systems, so I prefer them to batteries, even when it comes to primary weaponry. In the case of disabled systems, half the turrets still function. If you want point defense though, two SM+6 weapon pods can attach to the central hull of larger spacecraft and provide point defense through their turrets (two weapon pods with 8 VRF 30 kJ secondary weapons batteries with 10 turrets each are capable of engaging 160 separate targets per turn with RoF 100 each through using AI controls). While they would take the place of 20 SM+4 drones, I think that they would be worth the inconvenience.

[Michael Thayne]

I messaged David about the point-defense rules question, but for now I'm going to take a somewhat unprincipled approach of having no penalty for the first point-defense attack in a turn, a -2 penalty for the second attack (assuming beams), -4 for the third attack, -6 for the fourth attack, and so on.

Under this approach, a gunner with skill-11 might fire 50 shots at the first attack (+6 bonus), 200 shots at the second, 800 shots at the third, and 3200 shots at the fourth, and now you're mostly out of shots of this is a VRF improved turret in 10 minute rounds.

Another rules question that becomes relevant: if multiple gunners are possibly going to fire in point-defense against an attack, do they all have to declare before any dice are rolled? Or can gunner #2 wait until seeing if gunner #1 got the job done? This potentially has a big impact on the number of point-defense gunners you need to defend large, valuable targets, where a 2% chance the target gets hit by a nuke is not acceptable.

Another important factor in determining a fleet's point-defense requirements is ramming. In my experiments, successful defense against ramming is surprisingly difficult. What you don't want is to fire your particle beam at a ramming SM+4 drone, and get 8 hits that average 10 dHP of penetrating damage each, and then the drone makes all its survival rolls (which it has about a 30% chance of doing), so you just barely fail to destroy the drone and your ship takes 200 dHP of damage. That happens a couple times and you're dead.

An expensive but reliable solution is missiles. Otherwise, you want to make really sure your anti-drone beams can reliably inflict 90 dHP of damage. Like really, really sure. You'll either need several guns to destroy each ramming drone, or you'll have to use relatively large anti-drone beams—say a 30MJ particle beam.

[AlexanderHowl]

Unfortunately, the best defense against drones is other drones or missiles, though sufficiently powerful beam weapons can engage drones long before they come close enough to be a facotor. For example, a 100 MJ beam possesses an optimal range of 3,000 miles, meaning that it can shoot a drone for 15 turns before the point defense needs to engage it. Of course, bigger is better.