More Dakka [Spaceships]

[AlexanderHowl]

Improved is only an option for beam weapons, and it likely represents improvements in energy efficient. It might be possible to use ETC guns at TL9, and they would likely increase minimum velocity to 1.5 mps for double the cost (which is not a bad deal). For TL8 though, 2cm is too small for ETC improvements, as they would likely require a minimum of 8cm.

One thing to consider is that the 2cm guns in Spaceships fire guided munitions that have a 300 miles range, so it is not like insurgents would even see the helicopter as it is firing on them (though it would need some information about what it was firing on). Since the 2cm munitions are traveling at 1 mps, they can actually fire on suborbital trajectories, allowing them to reach anywhere within 300 km of the helicopter. A lot of TL8 combat already occurs beyond the horizon, so this would just allow attack helicopters the ability.

As for $10M a pop, I think that a lot of militaries would consider it cheap at twice the price because it would represent an overall improvement in capabilities. With three defensive ECM, their enemies would suffer a -6 to hit them (-3 if their enemies have tactical arrays). While slower than jets, they have a lot more endurance, as they are only limited by their life support. Of course, they would need a support vehicle if you wanted them forward deployed.

[Ulzgoroth]

Originally Posted by AlexanderHowl

Improved is only an option for beam weapons, and it likely represents improvements in energy efficient. It might be possible to use ETC guns at TL9, and they would likely increase minimum velocity to 1.5 mps for double the cost (which is not a bad deal). For TL8 though, 2cm is too small for ETC improvements, as they would likely require a minimum of 8cm.

One thing to consider is that the 2cm guns in Spaceships fire guided munitions that have a 300 miles range, so it is not like insurgents would even see the helicopter as it is firing on them (though it would need some information about what it was firing on). Since the 2cm munitions are traveling at 1 mps, they can actually fire on suborbital trajectories, allowing them to reach anywhere within 300 km of the helicopter. A lot of TL8 combat already occurs beyond the horizon, so this would just allow attack helicopters the ability.

As for $10M a pop, I think that a lot of militaries would consider it cheap at twice the price because it would represent an overall improvement in capabilities. With three defensive ECM, their enemies would suffer a -6 to hit them (-3 if their enemies have tactical arrays). While slower than jets, they have a lot more endurance, as they are only limited by their life support. Of course, they would need a support vehicle if you wanted them forward deployed.

Where are you getting 300 km from?

Fired from low altitudes in Earth atmosphere, I very much doubt that 20mm rounds are capable of achieving either sub-orbital flight or 300 mile (or kilometer) range on 1 mps muzzle velocity.

Certainly you could fire them over the horizon, but that's also a demonstrated possibility with TL6 HMGs...and not a particularly useful technique for a flying bullet hose. If you want an indirect fire support vehicle you don't need such an expensive platform. And you do want a larger caliber and exploding warheads for that kind of thing, because your chances of directly hitting personnel that way is not so good.

Ammo runs 2M g$ per load, but admittedly that's not terribly pricey for 20 tons of aircraft munitions.

[AlexanderHowl]

The delta-v for reaching 100 km altitude is 1.4 km/s (~0.9 mps), which technically allows for a ballistic range of ~1,000 km (I am assuming that the accurate range is 100 mile/300 mile, which is the C-range of conventional guns). The munitions of the conventional guns in Spaceships are guided, so they allow for superior accuracy. For example, there is no range penalty, just the base -10 accuracy penalty for 2cm guns, so the attack helicopter can accurately attack APCs from 100 miles away at a +5 to hit (assuming a SM+4 APC, a +4 from a proximity attack, and a +7 from an RoF 100).

If the dakka seems excessive, just upgrade the weapon batteries from secondary to major, which improves the caliber to 3cm for VRF guns. With 2,000 rounds per turret, that allows for 20 rounds of combat per turret, more than enough to tear through an infantry company at a safe stand off distance over the horizon. Since each successful hit deals 4d d-damage, that will tear through the majority of APCs without any trouble.

[Ulzgoroth]

Originally Posted by AlexanderHowl

The delta-v for reaching 100 km altitude is 1.4 km/s (~0.9 mps), which technically allows for a ballistic range of ~1,000 km (I am assuming that the accurate range is 100 mile/300 mile, which is the C-range of conventional guns).

Air resistance is a thing. For a small projectile starting near sea level, it's a very important thing.

Originally Posted by AlexanderHowl

The munitions of the conventional guns in Spaceships are guided, so they allow for superior accuracy. For example, there is no range penalty, just the base -10 accuracy penalty for 2cm guns, so the attack helicopter can accurately attack APCs from 100 miles away at a +5 to hit (assuming a SM+4 APC, a +4 from a proximity attack, and a +7 from an RoF 100).

How are you guiding any of them to targets you can't see, though?

Originally Posted by AlexanderHowl

If the dakka seems excessive, just upgrade the weapon batteries from secondary to major, which improves the caliber to 3cm for VRF guns. With 2,000 rounds per turret, that allows for 20 rounds of combat per turret, more than enough to tear through an infantry company at a safe stand off distance over the horizon. Since each successful hit deals 4d d-damage, that will tear through the majority of APCs without any trouble.

As multiple posters have observed, you seem to be impressed by the ability to demolish a large number of soft exposed targets and that is something that existing weapon systems are more than adequate for on the limited occasions where such a target environment is presented.

[Rupert]

Originally Posted by AlexanderHowl

Improved is only an option for beam weapons, and it likely represents improvements in energy efficient.

SS p.58 says otherwise.

Beam or gun RoF is doubled for “improved” beam or gun weapons.

[AlexanderHowl]

I do not think that something with DR 100 is necessarily a 'soft' target. As for the guidance, it would be a matter of programming in the trajectory and depending on the guidance mechanisms of the shell. In 2020, we can design very small guidance systems, so it would not be impossible to give a 2cm round homing capabilities.

The purpose of any lethal weapon system is to kill the maximum amount of enemy combatants for the minimum amount of cost. Of course, the USA tends to forget this, so the average cost to kill an enemy combatant tends to be between $1 million to $100 million per enemy killed (the former is the Vietnam War when adjusted for inflation while the latter is the Iraq War). A $10 million weapon system that can efficiently and effectively kill enemy combatants is not necessarily a bad choice, especially when it can do so outside of standard SAM range.

A possible redesign would to be instead have two 3cm VRF gun turrets, two 6cm RF gun turrets, and four 12cm gun turrets. Missiles are not cost effective because they have anything less than Long range, which tends to be anything in an atmosphere of a terrestrial planet, so I prefer conventional guns. A 12cm shell does an average of 63 d-damage to a target, which is more than enough to cripple or destroy a main battle tank from above.

[AlexanderHowl]

Originally Posted by Rupert

SS p.58 says otherwise.

Which is contradicted on p. 28, under the descriptions of the weapons, as it is only listed as an option for beam weapons.

[Rupert]

Originally Posted by AlexanderHowl

Which is contradicted on p. 28, under the descriptions of the weapons, as it is only listed as an option for beam weapons.

A positive statement that it's an option vs no mention seems to me to go on favour of the positive statement.

Originally Posted by AlexanderHowl

I do not think that something with DR 100 is necessarily a 'soft' target. As for the guidance, it would be a matter of programming in the trajectory and depending on the guidance mechanisms of the shell. In 2020, we can design very small guidance systems, so it would not be impossible to give a 2cm round homing capabilities.

The purpose of any lethal weapon system is to kill the maximum amount of enemy combatants for the minimum amount of cost. Of course, the USA tends to forget this, so the average cost to kill an enemy combatant tends to be between $1 million to $100 million per enemy killed (the former is the Vietnam War when adjusted for inflation while the latter is the Iraq War). A $10 million weapon system that can efficiently and effectively kill enemy combatants is not necessarily a bad choice, especially when it can do so outside of standard SAM range.

A possible redesign would to be instead have two 3cm VRF gun turrets, two 6cm RF gun turrets, and four 12cm gun turrets. Missiles are not cost effective because they have anything less than Long range, which tends to be anything in an atmosphere of a terrestrial planet, so I prefer conventional guns. A 12cm shell does an average of 63 d-damage to a target, which is more than enough to cripple or destroy a main battle tank from above.

DR100, while not 'soft' once you're talking vehicles in a military setting is not 'hard' either - it will stop small arms, but not AP rounds from cannons or even the lightest of modern anti-tank weapons. Heck, it won't even stop WWII-era 14.5mm anti-tank rifles.

This is a problem for the proposed helicopter, BTW - it has no meaningful armour, is large (HT gives a T-72 MBT as SM+4), and relatively easy to detect (it's flying, not hiding on the ground). That means, as ground vehicles can mount guns just as strong as it can, that it's dead meat. If you're using it for indirect fire from over the horizon, called in by someone closer, well it's competing with rocket launchers on the back of trucks when it comes to area attacks, and precision guided shells from artillery and guided glide bombs and missiles from aircraft/drones for point-targets. I don't see it as a particularly compelling alternative to these.

If you insist on using SS rules for ground combat, consider that as a flying object it's 'in plain sight' (though you might get to claim 'camouflage') and 'against deep space', while the ground targets are neither. That means it's detected 10000 to 500000 times as far away (i.e. as soon as it's over the horizon to any enemy sensor).

[AlexanderHowl]

Most advanced militaries have satellite surveillance, so it is relatively easy to see targets on the ground, especially 'hot' targets like vehicles. Since missiles do much less damage at closer than Long range than guns at TL7-TL8, it is necessary to use guns rather than missiles. Now, the dynamics change when the enemy takes out the satellites, which is likely the first thing that an enemy with comparable capabilities will do.

Of course, you can toss out the helicopter idea and go full fission air-ram (FAM). Using 4 FAM and winged, you can have 1.6g acceleration and a velocity of 2,500 mph at TL8. At that point, you can get anywhere in the world in less than six hours (you are also increase the velocity of your shells from 1 mps to 1.7 mps, which increases 12cm damage to 6d×5). Keep doing staffing runs at Mach 3.0 until you run out of ammo and then fly back.

[DaosusLeghki]

This may work in GURPS Spaceships, but not in real life. I think the problem is that you're assuming that:

1. a 20mm projectile will fly 100-300 km in atmosphere,
2. while guided,
3. to a target that has been identified, and
4. do meaningful damage.


To address the assumptions in order:

1. this is not possible for light munitions like 20mm in atmosphere. It might be possible for a hypervelocity sabot round in that diameter, but 1 mps is a little over half what might be normally considered "hypervelocity." Of course, if the munition keeps generating thrust, it's possible, but then it's a guided missile and not a gun. At the end of travel, there will not be enough energy to do serious damage. Keep in mind, 16 in naval guns tend to have ranges of 30-35 miles.

2. Any guidance electronics and mechanisms detract from the usable payload. At 20mm, this is quite small already.

3. Destroying targets is not really a problem in modern military contexts. Identifying them is the problem. Usually, you identify it with an infantry sweep nearby. The infantry come under attack and call in a strike on the target. Usually it is artillery or an air strike because near misses with smaller munitions are not that dangerous.

4. 20mm is a very light round as far as these things go. Only a direct hit (or very near miss for unarmored infantry) will do any serious damage. Note that the Bradley uses a 25mm autocannon, and it's intended only as an infantry support vehicle.

As others have noted, if you're trying to shoot far in atmosphere, it is usually better to be sitting still. That way, you can have more armor, a more stable firing platform, and your operational costs are lower.