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Old 09-07-2016, 10:38 AM   #1
kreios
 
Join Date: Jul 2013
Default Building a Fun Spacecraft Combat Paradigm

I have, for quite some time, looked at building a (comparatively hard) setting which includes combat between spacecraft. Naturally, I want to use the Spaceships rules.

Conventional wisdom is that this results in eggshells armed with sledgehammers, missiles dominating everything, and engagements being either inconclusive (enough point defense) or deadly (not enough point defense). This is - obviously - a situation I want to avoid.

In doing so, there are a few parameters of my analysis:

- I'm not using the basic space combat system.
- I'm wildly varying between time scale and hex/range depending on my analysis.
- I'm looking at probabilities, not skill rolls. That means I'm going to use roll vs 10 as 50% missiles intercepted, for example.
- I'm assuming the existence of skill-12 targeting programs, which do the actual weapon firing. That means one computer-gunner per weapon.
- I'm looking at TL10, with only the reactionless drive being superscience. Used features are Exposed Radiators, Accelerator Tube Limits (SS7:22), Slower Industrial Systems (SS7:23), and the Telescoping Robot Arm feature (SS8:9)
- I have not yet decided which stardrive to use; my current favourite would be a jump drive which can jump from most places except lower than about GEO; and one jump being at most half a lightyear, requiring realignment. It is instantaneous, though.

I am also thinking about using Armour as Dice (Pyramid 3/34:32). Using this, nanocomposite armour looks like this (slightly simplified to remove most die adds):

Code:
SM          +5      +6      +7      +8      +9      +10     +11     +12     +13     +14     +15
Armour      2d      3d      5d      7d      10d     15d     20d     30d     40d     60d     90d





Missiles

Damage
The smallest missile that fits on a spacecraft is the 16cm missile, which weights 67kg (about 150lbs). It can mount a nuclear warhead for 4dx1,000 burn etc plus a linked 3dx1,000 ex damage, or a conventional warhead for 6dx4 (2) collision or the same without armour-piercing when firing for proximity detonation. It can also be equipped with an X-ray laser warhead (SS8:9), for a range of 300/1,000 miles, RoF of 8, and 10d(5) damage.
I'm restricting myself to this missile since it has the highest firing rate, and can still mount a 25kt nuclear warhead. Should it prove too small, I'm going to upgrade.

Nuclear Warhead
The nuclear weapon itself suffices to destroy everything up to SM+15 on a direct hit. An SM+15 spacecraft has dHP of 1,000; devoting all six systems in a location to nanocomposite gives it an US dDR of 1,800. The burn damage will bring it down to at least -1,200HP/-1.2xHP (up to -22xHP best case, meaning total vapourization); including the explosion the spacecraft ends up at -2.4xHP. This means two rolls against HT to avoid destruction, plus the component loss. In summary, a nuclear missile hitting means certain death for even the most over-engineered block of armour floating in space. Using armour as dice doesn't change that.

It looks differently when looking at nuclear proximity detonations. This decreases damage by a factor of 100. Suddenly, our SM+15 spacecraft is able to easily survive even a worst-case proximity detonation. Yay!
However, how does it look like for a more reasonable-sized spacecraft? Immunity to nuclear proximity detonations is guaranteed at 240dDR, which is five systems at SM+10, four at SM+11, three at SM+12, two at SM+13 and one at SM+15. It is sufficient to reduce a SM+5 spacecraft with two nanocomposite systems to -1xHP; it's also pretty effective against radiators. Note that a nuclear blast might also damage spacecraft in the same 10-mile hex, though a 25kT warhead will never roll high enough to do so, except for missiles.
Using armour as dice, we need to withstand 40d dDmg. This can be achieved at one system at SM+13, two at SM+11, three at SM+10 and five at SM+9.

What if we use more power? A 10 megaton nuclear warhead - at $1M per pop - fits only the biggest, 52cm, missiles. It does 9dx10,000 burn plus a linked 6dx20,000 ex. Of course, it'll still destroy everything on a contact detonation. On a proximity detonation, it does 8dx100/6dx200. That's much higher than the 25kT damage, and only an SM+15 fully-armoured section will be able to avoid damage - if the damage roll is minimal. On average, it's going to be 4,200 dDmg; meaning it's roughly as powerful as a 25kT contact detonated warhead. Using armour as dice, that's 900d to withstand, where even a fully-armoured SM+15 section only gives you 540.

Summary: You get hit directly by a nuclear warhead, and you're dead. If it's powerful enough, even a proximity detonation will kill you.


Kinetic Damage
Our 16cm missile has a dDmg of 6dx4 (2), which is multiplied by velocity. It has, according to SS3:36, 5G acceleration and 10mps dV. Actual analysis is difficult, since we don't know the closing speed at firing time. However, we can look at speeds needed to destroy certain craft.
A heavily-armoured SM+10 (3 armour systems in the section) craft has a dDR of 150, and dHP of 150. Meaning that, to ensure it's reduced to -1xHP, our 16cm missile has to travel at 15mps; to do so on average, 5mps. This seems doable. Using armour as dice, it has to inflict at least 45d damage to penetrate, which is equivalent to slightly more than 2mps; it has to travel at 14mps to ensure destruction.
Against the most heavily-armoured spacecraft (SM+15, 6 armour systems) with 1,000dHP and 1,800 DR, it has to travel at most 120mps and on average 35mps. That's much more difficult - but keep in mind that it would still allow the missile launcher of a fighter to easily kill a Class V starport. Using armour as dice, it has to travel at most 105mps.

Using proximity detonation slightly increases the required speed, but since multiple hits are generated, it might be worth it.

Summary: Being hit by a kinetic missile means that you're dead.

X-Ray laser warheads
The X-Ray laser warhead is interesting in that its damage does not scale with the missile's diameter; only RoF does. Our 16cm missile does 10d(5) d-damage, and has an RoF of 8. This 10d(5) gives it a penetration of 50 to 300dDR; a heavily-armoured SM+10 spacecraft (3 armour sections; 150dDR, 150dHP) will lose 5dHP on an average roll, and risk losing up to 30dHP. This might be repeated up to eight times per missile. With armour as dice, our SM+10 spacecraft takes just 1d of damage per hit, for an average of 3.5dDmg. This does not really scale with the missile size, however.
Why would you ever use it? Well, because it's ranged, with a range of 300/1,000 miles. That is kind of huge - it decreases time for point defense to hit, and decreases hit chance. Firing from 29 10-mile hexes away gives them a range modifier of -2, compared to one of +12 (!) for point defense.
It should also allow you to hit the centre or rear of a spacecraft by letting the missile pass the other spacecraft and then attack. This increases time spent in the point defense envelope, but might decrease armour.

Summary: Being hit by an x-ray laser warhead is definitely survivable, but you are going to take damage.


Summarizing all of the different missile types available, it seems as if the x-ray laser warhead is close to what I'd want: Hitting with one doesn't instantly obliterate every single target.
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hard sci-fi, spaceship, spaceship battles, spaceships

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