Rail Gun for Space weapon?

[pendragonman]

Suppose we want to add rail guns to available armaments.

If one wants to add it to Star (Space) weaponry, what stats? How much damage does it do? What is the range? Are there different sizes for different ship scales?

Should it be limited to planetary range? Strictly a "surface" or Near Planetary Orbit weapon? If a "surface" weapon, what is the personal damage scale?

And another thing, how do you scale a ship weapon like a ship's laser to a personal PC/NPC hit/damage roll?

 

[McPerth]

See that most those questions are version dependent...

Suppose we want to add rail guns to available armaments.

If one wants to add it to Star (Space) weaponry, what stats? How much damage does it do? What is the range? Are there different sizes for different ship scales?

Should it be limited to planetary range? Strictly a "surface" or Near Planetary Orbit weapon? If a "surface" weapon, what is the personal damage scale?

IIRC someone told here than in MgT:TCS they are represented. but I don't onw it, so I don0't know exactly how they are rated.

And another thing, how do you scale a ship weapon like a ship's laser to a personal PC/NPC hit/damage roll?

MT has its equivalences, and MgT modiifes damage by a factor of 50. If I understood well what otehrs have told, Striker has them too. IDK about other verions, but, in genenral, one way or another, the meaning is personal weaponry is ineffective or nearly so against starships, while a starship weapon against a personnel or vehicular scale means a kill.

 

[kilemall]

I have em in CT:HG as 1:1 replacements for PAs, 2 surface damages instead of 1 surface and 1 radioactive.

 

[Xerxeskingofking]

See that most those questions are version dependent...



IIRC someone told here than in MgT:TCS they are represented. but I don't onw it, so I don0't know exactly how they are rated.



MT has its equivalences, and MgT modiifes damage by a factor of 50. If I understood well what otehrs have told, Striker has them too. IDK about other verions, but, in genenral, one way or another, the meaning is personal weaponry is ineffective or nearly so against starships, while a starship weapon against a personnel or vehicular scale means a kill.

that would be me that told you, although only Spinal railguns are in TCS, the other sizes are in high guard. in the 2nd edition, they have moved all of them into HG2e.

in MgT, they appear in 3 rough sizes: Barbette, Bay and Spinal. railguns behave slightly differently at all three levels.

a defining characteristic of railguns in MgT was short range. barbettes and bays had a max range of Short, while the spinal mounts can reach out to Medium.

barbettes were dropped form MgTe2, but in 1e they were a 3d6 weapon, with 20 shots/ton for ammo.

bay weapons were a whole battery of railguns mounted in Parallel which have an autofire ability, unique among starship weapons in MgT . damage is still 3d6 a hit, with ammo still 20/ton (though 2e moves to counting ammo in "attacks" instead)

spinal mounts get a armour penetration ability that lets them ignore a certain number of armour points when they hit. generally smaller and cheaper, with a lower TL than particle and meason weapons, they are completive with particle spinals, but after tl12 and the introduction of mesons, they fall behind.

in short the railguns in MgT are best used in a close range brawl, where they can swamp a target with hits (which are not subject to point defence, either)


edit:

the above is true for ship to ship weapons. their is a separate "ortillary" type bay weapon intended for ground support. its described as "a single hit form a ortillary railgun is like a tactical nuclear strike". They suffer heavy penalties when trying to target a spaceship. damage is 12d6 in 1e, and in 2e is 2DD ("Destructive" dice, which are multiplied by 10)

as mentioned, when translating between starship and personal scale, damage is multiplied by 50 (so the 2e ortillary gun does 2d6 x10, then x50, or in other words, it does 1,000-6,000 damage)

 

[infojunky]

See that most those questions are version dependent...

Yes, Yes they are. In my current iteration of Mayday-centric rules I have included them. I am using 100 second turns with 1,000 km hex. They have worse range DM than pulse lasers.

Beam laser have a DM of -1 per hex
Pulse lasers have a DM of -2 per hex
Rail Guns have a DM of -3 per hex.

What I haven't figured out yet is how many ready rounds on the mount, Nore ammo weight, though I am tempted to go with half the weight of a missile or Sand.

Also Note this current set of rules is centered on a engagement envelope of Geostationary orbit, i.e. around where most High Ports live and other related orbital junk....

 

[AnotherDilbert]

as mentioned, when translating between starship and personal scale, damage is multiplied by 50 (so the 2e ortillary gun does 2d6 x10, then x50, or in other words, it does 1,000-6,000 damage)

In MgT2 the scale between personal/vehicle damage and spacecraft damage is 1:10.

The 100 dT Ortillery bay does 2D × 10 space damage or 2D × 10 × 10 personal damage.

 

[nobby-w]

[ . . . ]
If I understood well what otehrs have told, Striker has them too.
[ . . . ]

Striker has mass drivers (coil guns) but doesn't discuss rail guns by name. However, there's no reason why you couldn't adapt mass drivers to support rail guns, as I did at one point. With Striker, mass drivers had range, penetration modifiers, size modifiers and so forth based on the velocity. Velocity could be one of Mortar, Low Velocity (howitzer), medium velocity, high velocity or hyper velocity. Power consumption was also based on rate of fire.

You could add a couple of bands after hyper velocity (assumed to be ~1500-2000m/sec), for example:

• 3k - Roughly mach 10, +12 KEAP penetration
• 5k - Roughly mach 15, +15 KEAP penetration

Rail guns might come in hyper velocity, 3k or 5k. Below that coil guns can be used without needing to worry about wear on the rails, so there's no point in building rail guns. The other advantage of mass drivers over rail guns is that they would have higher possible rates of fire, which would still make them better indirect fire weapons.

As an aside, Striker used to somewhat under-rate the power of KEAP rounds over TL6,¹ so you may wish to add a re-balance of these.

¹ I have heard it suggested that this was because Striker was based on a WWII game that GDW had just done, so the performance of CPR guns was based on WWII stats without enough thought put into high-tech CPR rounds. However, this is apocryphal.

 

[AnotherDilbert]

A railgun would be a very short range weapon against manoeuvring target.

If we accelerate the rounds to 1000 km/s they would take 10 s to reach a target at 10000 km range. In that time even a 1G target will have moved up to 500 m in a random direction. In other words you will not hit an evading target.

A 10 g rifle bullet would have muzzle energy of 0.01 × 1000000² / 2 ≈ 5 GJ, almost 1000 times a current 120 mm tank gun.

To fire one such round every 10 seconds would take at least 500 MW or 2 EP.

So roughly: A railgun would have very short range, use large amounts of power, and use a negligible amount of ammunition.

 

[kilemall]

I'm assuming a starship level railgun in a bay or spinal is NOT a striker mass driver, rather small bits firing at near-c, precisely because of the range/target maneuver issue.

Boom table shows what is possible-

http://www.projectrho.com/public_html/rocket/usefultables.php#id--The_Boom_Table

http://www.projectrho.com/public_html/rocket/spacegunexotic.php#id--Relativistic_Weapons

 

[McPerth]

A railgun would be a very short range weapon against manoeuvring target.

If we accelerate the rounds to 1000 km/s they would take 10 s to reach a target at 10000 km range. In that time even a 1G target will have moved up to 500 m in a random direction. In other words you will not hit an evading target.

A 10 g rifle bullet would have muzzle energy of 0.01 × 1000000² / 2 ≈ 5 GJ, almost 1000 times a current 120 mm tank gun.

To fire one such round every 10 seconds would take at least 500 MW or 2 EP.

So roughly: A railgun would have very short range, use large amounts of power, and use a negligible amount of ammunition.

See that my mention of Striker was answering to his question about how to scale ship's weapons to personal level, not to the rail guns specifically...

Unfortunately, in MT the energy accrued by an object with gravitics is not always in accordance with the power used :CoW:. See this thread as an example...

 

[pendragonman]

A railgun would be a very short range weapon against manoeuvring target.

If we accelerate the rounds to 1000 km/s they would take 10 s to reach a target at 10000 km range. In that time even a 1G target will have moved up to 500 m in a random direction. In other words you will not hit an evading target.

A 10 g rifle bullet would have muzzle energy of 0.01 × 1000000² / 2 ≈ 5 GJ, almost 1000 times a current 120 mm tank gun.

To fire one such round every 10 seconds would take at least 500 MW or 2 EP.

So roughly: A railgun would have very short range, use large amounts of power, and use a negligible amount of ammunition.

Do you mean 10 grams? The way I read it is 10 gravities.

 

[AnotherDilbert]

Accelerating something to 0.5c in a 10 m accelerator would take about 10 / (300000000/4) ≈ 133 ns and subject the round to 150000000 / 133×10⁻⁹ ≈ 10¹⁵ m/s² or 100 000 000 000 000 G. No material will withstand that, the round would be vaporised.

A 1 mg mass accelerated to 0.5c would have an energy of a little over 0.001 × 150000000² / 2 ≈ 11 TJ or roughly 30 ktTNT. Handling that energy in 133 ns would mean an energy flow of 11 TJ / 133 ns ≈ 10²⁰ W = 100 EW. No ship-sized power handling equipment would be able to withstand that, so the weapon would probably be vaporised too.

Accelerating even a grain of sand to near-relativistic speeds in a bay-sized weapon is pure magic.

 

[AnotherDilbert]

Do you mean 10 grams? The way I read it is 10 gravities.

Yes, I meant 10 gram.

Since I am used to SI units I didn't even see the ambiguity.

 

[aramis]

Accelerating even a grain of sand to near-relativistic speeds in a bay-sized weapon is pure magic.

Traveller has (per TNE & T4) gravitic focusing of lasers at TL14.

A bay-sized weapon at 200G can get about 1334m/s (it's 445m x 2m diameter). put that over the traveller C of 300,000,000m/s, you get 4 microC... 4.44e-6 C
At 400 G we can push that to 1886.

The energy input should be astonishingly high, tho'...

Why 200G? Because that's what I recall being stated as the minimum to make a laser bend notably in the distance that fits inside a turret can. I didn't do that math.

 

[AnotherDilbert]

Unfortunately, in MT the energy accrued by an object with gravitics is not always in accordance with the power used :CoW:. See this thread as an example...

I agree, that is an old problem. It can trivially be demonstrated in at least CT, MT, and TNE.

But I think it is only technically true for thrusters and grav modules (or the vehicle that contains them), which is somewhat consistent with the technological description. If we further assume that thrusters and grav modules interacts with the local gravity field and hence exchange momentum and kinetic energy with nearby masses, such as celestial bodies, we can even pretend that some sort of physics remains intact.

I don't think that is a factor for any accelerated object.

 

[AnotherDilbert]

Traveller has (per TNE & T4) gravitic focusing of lasers at TL14.

A bay-sized weapon at 200G can get about 1334m/s (it's 445m x 2m diameter). put that over the traveller C of 300,000,000m/s, you get 4 microC... 4.44e-6 C

I'm not sure I understand you correctly, but 445 m is a rather large spinal mount.

Each bay has a single long dimension and two shorter dimensions. The long dimension, in meters, is found by taking the bay's volume in cubic meters, extracting the cube root, multiplying by 1.4, and rounding to the nearest whole number.

long length = 1.4 × 1400^1/3 ≈ 16 m.

A constant 200 G in a 16 m accelerator would take us to 253 m/s in 0.1265 s. That is way too little to make a railgun.

 

[infojunky]

This topic always bemuses me. So much effort to limit and write out Railguns, while not a blink about Plasma and fusion weapons. Not to mention Meson weapons.

One of the biggest problems with these sorts of discussion is the Nebulous set of assumptions each person brings to the table.

My assumptions are a 1,000 km range increment, that direct fire weapons are firing throughout the turn.

 

[aramis]

I'm not sure I understand you correctly, but 445 m is a rather large spinal mount.

long length = 1.4 × 1400^1/3 ≈ 16 m.

A constant 200 G in a 16 m accelerator would take us to 253 m/s in 0.1265 s. That is way too little to make a railgun.

It's 1400 cubic meters - the same volume as a 100Td bay...

Many times, SSU designers use bays as spinals. Me included.

And MANY of us don't use a 1.4x1x1 box profile ratio for ships...

 

[pendragonman]

If it helps, my interest is to try to make Trav designs of the ships used in Chuck Gannon's Caine Riorden series.

I could be misremembering, but I can recall orbital fire, planetary fire, but no true long range deep space fire.

 

[AnotherDilbert]

It's 1400 cubic meters - the same volume as a 100Td bay...

Many times, SSU designers use bays as spinals. Me included.

And MANY of us don't use a 1.4x1x1 box profile ratio for ships...

You can of course do as you like, but 445 m is a rather large ship.