Highguard 2.0 - Railgun Barbette

[Condottiere]

Minimum size of thrusters is half a tonne, at least going by given efficiencies.

 

[-Daniel-]

Minimum size of thrusters is half a tonne, at least going by given efficiencies.

So the minimum weight a rail gun round with a seeker head could be is just over half a ton? That seems kind of silly to me.

 

[phavoc]

Minimum size of thrusters is half a tonne, at least going by given efficiencies.

Something moving the speed of a railgun round isn't going to be able to do much maneuvering before it hits it's target. It's speed is a factor, it's very small size is a factor, and the relative amount of energy required to make a useful vector change is going to be (probably) beyond what it's capable of carrying (reaction-wise).

It doesn't need a full-sized thruster. And you can make them far smaller (just compressed gas would be fine).

 

[wbnc]

causing a lateral vector change does not require a starship grav thruster. even something as weak as the systems used by a grav belt could provide enough thrust to make slight changes in the trajectory of a projectile. we aren't talking about turning it around and heading the opposite direction a few degrees of movement would be all that was needed.

 

[Jeraa]

Minimum size of thrusters is half a tonne, at least going by given efficiencies.

How do you figure that? Minimum ship size is 10 tons. The rating-1 maneuver drive takes up 1% of the ship. 1% of 10 tons is 0.1 tons. A rating-0 drive would be half that (0.05 tons).

I'm not seeing anything in High Guard 2e that says there is a minimum size of half a ton.

Edit: Unless you are still using 1e High Guard, in which case the smallest small craft drive is 0.5 tons. But this is specifically a 2e High Guard question (read the title), so whatever 1e says doesn't matter.

 

[Condottiere]

1. Schrodinger's Cat is at it again, like with firmpoints and seventy tonne smallcraft; it was clarified that officially the smallest drive is a tonne (presumably at given performance), but the Pebble drive is from an official Mongoose Second High Guard spaceship, and weighs in at half a tonne.

2. There are likely minimum sizes for thrusters (and fusion reactors) which might depend on technological level (outside that achieved with advanced manufacturing), but High Guard doesn't seem to cover that.

3. How big is a railgun bullet? Can you fit in steering and sensors?

4. How fast is a railgun bullet? Can the sensors detect anything at that speed, and have time to make flight corrections?

5. Now a mass driver ball bearing probably can be guided; it's certainly big and slow enough.

 

[AnotherDilbert]

... it was clarified that officially the smallest drive is a tonne ...

It was? Where?

The Launch uses a 0,2 dT M-drive.

(Tonne is English for metric ton [1000 kg], and should not be used for displacement ton?)

 

[wbnc]

1. Schrodinger's Cat is at it again, like with firmpoints and seventy tonne smallcraft; it was clarified that officially the smallest drive is a tonne (presumably at given performance), but the Pebble drive is from an official Mongoose Second High Guard spaceship, and weighs in at half a tonne.

2. There are likely minimum sizes for thrusters (and fusion reactors) which might depend on technological level (outside that achieved with advanced manufacturing), but High Guard doesn't seem to cover that.

3. How big is a railgun bullet? Can you fit in steering and sensors?

4. How fast is a railgun bullet? Can the sensors detect anything at that speed, and have time to make flight corrections?

5. Now a mass driver ball bearing probably can be guided; it's certainly big and slow enough.

3: this is probably dependant on the design of the rail gun. my take is that you are dealing with a mass around 15-50 Kg, at around 40-50K Kph. ( the velocity a missile maintains as determined by looking at flight time to target at distance range band) that would result in damage several orders of magnitude higher than a 120mm Rhinemetal gun firing a high velocity (1750 m/s) round of the same size . prototype railguns double that velocity at current TL.

A standard railgun would be firing rapidly using lighter rounds instead of one single massive round. or a number of 'tubes' would be firing in sequence from a bay type weapon. The tonnage per attack listed on the charts is made up of a LARGE number of individual rounds consumed rather than a single projectile.

4: the velocity of 40K Kph is fast enough to allow a railgun round to impact on targets at close to short ranges in a single turn. it can hit a target at medium range in 1.5 to 2 turns. At those velocities, reaction times would be short, but the object would be slow enough for a computer to have time to process the data and react. if the round is already pointed at a target when fired, all it has to do is adjust for "drift" which means you are talking about creating lateral acceleration not countering or adjusting initial velocity. Moving a 25-50Kg object around is not hard at all. It requires little force. since a grav belt can move a 100Kg person a similar sized unit could manage a 15=50Kg penetrator. several guided weapons use small rockets mounted along their flanks to generate lateral thrust for course correction already.

Since flight times are in the 3-5 minute range a guided railgun round would not need to make course corrections in milliseconds to hit it's target which would require considerably more powerful flight control system.

one advantage to using an "electric" drive such as gravitic based system in the design would be that you could encase the entire system in a solid block of silica, or synthetic sapphire ( which is basically an aluminum crystal). That would allow ou to insert the heavy penetrator into the core of the monolithic sabot that contains power supply, electronics and flight control thrusters. then place a plug of nickel iron at the rear. the railgun propels the nickel-iron forward and it carries the round along with it.

And yes synthetic sapphire would have the structural strength to withstand the acceleration forces It is also Fairly cheap to produce. they are already producing synthetic sapphire screens for smartphones at around 10-15 dollars a piece..with costs projected to drop radically as they begin mass production. BY TL-12 the ability to "print" circuitry and other systems into the material should be available.

 

[AnotherDilbert]

3: this is probably dependant on the design of the rail gun. my take is that you are dealing with a mass around 15-50 Kg, at around 40-50K Kph. ( the velocity a missile maintains as determined by looking at flight time to target at distance range band) that would result in damage several orders of magnitude higher than a 120mm Rhinemetal gun firing a high velocity (1750 m/s) round of the same size . prototype railguns double that velocity at current TL.

40 000 km/h or about 10 000 m/s is a bit slow in space combat, probably slower than the spacecraft you are shooting at. A ship accelerating at 9 G or 90 m/s² will have a speed of 360 s × 90 m/s² = 32400 m/s after a single round.

At 10 km/s it would take 1000 / 10 ≈ 100 s to reach a stationary target. A manoeuvring target could have moved d = at²/s ≈ 90 × 100² / 2 ≈ 450 km away from it's projected course by then. The projectile would have to be able to manoeuvre just as much as the target to have a reasonable chance to hit it, and then the projectile would basically be a short range missile. No conventional rocket will allow that much ∆v, but M-drives obviously will.

 

[wbnc]

3: this is probably dependant on the design of the rail gun. my take is that you are dealing with a mass around 15-50 Kg, at around 40-50K Kph. ( the velocity a missile maintains as determined by looking at flight time to target at distance range band) that would result in damage several orders of magnitude higher than a 120mm Rhinemetal gun firing a high velocity (1750 m/s) round of the same size . prototype railguns double that velocity at current TL.

40 000 km/h or about 10 000 m/s is a bit slow in space combat, probably slower than the spacecraft you are shooting at. A ship accelerating at 9 G or 90 m/s² will have a speed of 360 s × 90 m/s² = 32400 m/s after a single round.

At 10 km/s it would take 1000 / 10 ≈ 100 s to reach a stationary target. A manoeuvring target could have moved d = at²/s ≈ 90 × 100² / 2 ≈ 450 km away from it's projected course by then. The projectile would have to be able to manoeuvre just as much as the target to have a reasonable chance to hit it, and then the projectile would basically be a short range missile. No conventional rocket will allow that much ∆v, but M-drives obviously will.

Missiles move from distant range to impact in an hour so they are "only" moving at 50,000 Kph... while you can go much faster if you like that brings a whole lot of problems if you are trying to maneuver as a group.

As for using reaction drives as vector control...why? if you have gravitics that are potent enough why not use them. a vehicle/robot grade gravitic unit is perfectly fine for controlling the flight of a 15-50kg mass.

 

[AnotherDilbert]

Missiles move from distant range to impact in an hour so they are "only" moving at 50,000 Kph... while you can go much faster if you like that brings a whole lot of problems if you are trying to maneuver as a group.

To cover 300 000 km in an hour you need an average speed of 300 000 km/h. Since you start with insignificant speed and accelerate the whole way the end speed would be about 600 000 km/h.

If you accelerate fully ( a = 10 G ≈ 100 m/s² ) the whole way a missile would travel d = 300 000 km in t = SQRT( 2 × d / a ) ≈ 2450 s with a terminal speed of 2450 s × 100 m/s² = 245000 m/s or 882000 km/h.

As for using reaction drives as vector control...why? if you have gravitics that are potent enough why not use them. a vehicle/robot grade gravitic unit is perfectly fine for controlling the flight of a 15-50kg mass.

Reaction drives are cheaper, not insignificant when you fire a lot of ammunition. Most editions have had minimum sizes for M-drives. Anti-grav such as grav-belts only works well in strong gravity fields, not deep space.

 

[Jeraa]

Reaction drives are cheaper, not insignificant when you fire a lot of ammunition. Most editions have had minimum sizes for M-drives. Anti-grav such as grav-belts only works well in strong gravity fields, not deep space.

Mongoose Traveller 2e is not most editions. There is no listed (or implied) minimum size for M-drives, and no mention (or even implying) that anti-grav only works in gravity fields. Other editions of Traveller might have, but we aren't talking about those so they don't really matter.

As for costs:

While we don't know just how large a railgun round is (1e had them at 20/ton), we do know they are fired in tons/attack. That probably includes various autoloaders and other machinery to load the rounds into the railgun, but we'll just ignore that for now.

Based on the ship design rules, a M-drive takes up 1% of the hull per drive rating, and costs MCr2 per ton of drive. That means (roughly speaking) one ton of railgun projectiles would require a total of 0.01 tons of M-drives per rating, at a cost of MCr0.02 (Cr20,000) per drive rating per ton of projectiles. Railgun ammunition costs Cr15,000 per ton, so you are more than doubling the cost just for a drive rating of 1.

A reaction drive requires 2% of the hull per rating, but only costs MCr0.2 per ton of drive. One ton of projectiles would need a total of 0.02 tons of reaction drives per rating, at a cost of only MCr0.004 (Cr4,000) per drive rating per ton of projectiles.

 

[AnotherDilbert]

Mongoose Traveller 2e is not most editions. There is no listed (or implied) minimum size for M-drives, and no mention (or even implying) that anti-grav only works in gravity fields.

No, but we cannot build an M-drive smaller than 0,05 dT in MgT2. The M-drive disadvantages in HG corresponds to simpler grav drives in MT. Grav vehicles can reach orbit, but nothing is stated about reaching moons or other planets. The limitations from earlier editions can possibly still be used, even if MgT2 is not detailed enough to reiterate them.

Based on the ship design rules, a M-drive takes up 1% of the hull per drive rating, and costs MCr2 per ton of drive. That means (roughly speaking) one ton of railgun projectiles would require a total of 0.01 tons of M-drives per rating, at a cost of MCr0.02 (Cr20,000) per drive rating per ton of projectiles. Railgun ammunition costs Cr15,000 per ton, so you are more than doubling the cost just for a drive rating of 1.

We also need a power source, a battery will do.

 

[Jeraa]

We also need a power source, a battery will do.

True. A M-drive uses 10% of the ships hull volume multiplied by the drive rating in power points. For 1 ton of projectiles, that is 0.1 Power per drive rating.

High Efficiency Batteries produce 40 Power for MCr0.1. We need only 0.1 Power which costs 1/400th that, or Cr250 per drive rating. That would only allow 1 round of Thrust, so multiply that by the number of times you want the projectile to maneuver.

 

[wbnc]

Missiles move from distant range to impact in an hour so they are "only" moving at 50,000 Kph... while you can go much faster if you like that brings a whole lot of problems if you are trying to maneuver as a group.

To cover 300 000 km in an hour you need an average speed of 300 000 km/h. Since you start with insignificant speed and accelerate the whole way the end speed would be about 600 000 km/h.

If you accelerate fully ( a = 10 G ≈ 100 m/s² ) the whole way a missile would travel d = 300 000 km in t = SQRT( 2 × d / a ) ≈ 2450 s with a terminal speed of 2450 s × 100 m/s² = 245000 m/s or 882000 km/h.

As for using reaction drives as vector control...why? if you have gravitics that are potent enough why not use them. a vehicle/robot grade gravitic unit is perfectly fine for controlling the flight of a 15-50kg mass.

Reaction drives are cheaper, not insignificant when you fire a lot of ammunition. Most editions have had minimum sizes for M-drives. Anti-grav such as grav-belts only works well in strong gravity fields, not deep space.

Combat does not occur at those ranges. At 50,000km, sensor detail is NONE for radar and lidar, and on minimal for thermal. You can tell something artificial is there but not much else. to be able to tell what you are shooting at you would have to close to 50,000Km just to get a basic outline of the target. beyond that range your firing at heat blobs. even if you have all the extra sensor systems available you cant gt a decent idea of the tactical situation at 300,000Km

if a ship is screaming toward the enemy at full burn it is irrevocably committed to close range engagement with no idea of the exact composition of the enemy force.

 

[Jeraa]

Combat does not occur at those ranges. At 50,000km, sensor detail is NONE for radar and lidar, and on minimal for thermal. You can tell something artificial is there but not much else. to be able to tell what you are shooting at you would have to close to 50,000Km just to get a basic outline of the target. beyond that range your firing at heat blobs. even if you have all the extra sensor systems available you cant gt a decent idea of the tactical situation at 300,000Km

if a ship is screaming toward the enemy at full burn it is irrevocably committed to close range engagement with no idea of the exact composition of the enemy force.

Forward observers (like small craft on recon duty) can tell you what is going on. Missiles, which have their own targeting system and don't use the ships, would get a better picture of the target as they got closer. Combat can occur at those distances, but is limited to missile engagements (other weapons don't have the range).

The rules even state the difficulty of that kind of combat:

Note that while missile salvos can be fired at Distant ranges, the attacking ship must have detected its target before they can be launched. Given the limited information that can be gained from sensors at this range, friendly fire incidents may be common among Travellers who are too trigger happy with their missiles.

 

[wbnc]

Combat does not occur at those ranges. At 50,000km, sensor detail is NONE for radar and lidar, and on minimal for thermal. You can tell something artificial is there but not much else. to be able to tell what you are shooting at you would have to close to 50,000Km just to get a basic outline of the target. beyond that range your firing at heat blobs. even if you have all the extra sensor systems available you cant gt a decent idea of the tactical situation at 300,000Km

if a ship is screaming toward the enemy at full burn it is irrevocably committed to close range engagement with no idea of the exact composition of the enemy force.

Forward observers (like small craft on recon duty) can tell you what is going on. Missiles, which have their own targeting system and don't use the ships, would get a better picture of the target as they got closer. Combat can occur at those distances, but is limited to missile engagements (other weapons don't have the range).

The rules even state the difficulty of that kind of combat:

Note that while missile salvos can be fired at Distant ranges, the attacking ship must have detected its target before they can be launched. Given the limited information that can be gained from sensors at this range, friendly fire incidents may be common among Travellers who are too trigger happy with their missiles.

The way I have always imagined the sequence of events if that local defenders pick up the EM Spike of multiple jump drives, then planetary/orbital detection stations pick up the artificial thermal and EM signatures of the enemy intruding vessels. Hours go by as the defensive vessels sort themselves out and set up a defensive array to meet the intruders near likely high value targets along the intruders flight path.

Scouts, fighters and drones sortie to gather data on the intruders using their very high acceleration to get within sensor range and find out exactly what the opposing force is comprised of. Both sides will be dong a lot of scouting as they try to piece together the information needed to formulate an attack/defense plan.

some amount of raiding and harassment strikes would definitely take place as fast SDBs and strike craft probe the lines on both sides. or try to destroy or severely damage exposed units before they can form up and get into battle order.

Once the aggressor commits to an attack the defender makes final adjustments and then a waiting game takes place as te range decreases .. the aggressor might try t plow through an enemy battlegroup but the need to have as much maneuver ability as possible so they aren't going to come screaming at full burn unless they are on an active attack run to get as close as feasible to drop off ordnance fire a few salvos and then veer off to avoid getting torn apart by close range fire.

Unless the tactic being used is specifically one that requires a blitzkrieg o the enemy they are going to move like Heavyweight boxers cautiously and deliberately trying to gain some sort of advantage, then Start swinging. a few long range sniping attacks with missiles, strikes by fighters and attack boats, then if the commanders of both sides feel it's the right time to engage heavily they wil move in and slug it out with their heavy weapons and spinal mounts.

If one commander feels he needs to maintain range then a running fight may occur. well outside the range of any Planetary guns/missile if the aggressor has anything to say about it. No one wants to fight planetary guns and mobile defenses at the same time if it can be avoided.

it may be weeks or moths before any significant reinforcements can arrive from nearby systems to assist the defenders. It would take at least two weeks for a relief force to show up, one week for the scout/courier to reach a neighboring system if it is within jump range, and another for the relief force to jump into the system...and that's assuming a suitable force is within jump range, and ready to go at a moments notice.

Of course other scenarios are plausible it really depends on the capabilities of the vessels involved, and the strategy favored by the commanders of both forces.

 

[AnotherDilbert]

I mostly agree with you, apart from:

Combat does not occur at those ranges. At 50,000km, sensor detail is NONE for radar and lidar, and on minimal for thermal. You can tell something artificial is there but not much else. to be able to tell what you are shooting at you would have to close to 50,000Km just to get a basic outline of the target. beyond that range your firing at heat blobs. even if you have all the extra sensor systems available you cant gt a decent idea of the tactical situation at 300,000Km

In wartime a missile-heavy fleet will launch on an approaching unidentified fleet at extreme range. It can't afford to let a beam fleet to get into firing range.


If large empires fight the campaigns are likely to be large, much larger than a single system. The aggressor is likely to be in a hurry to get to crush this system and get to the next.

 

[AnotherDilbert]

High Efficiency Batteries produce 40 Power for MCr0.1. We need only 0.1 Power which costs 1/400th that, or Cr250 per drive rating. That would only allow 1 round of Thrust, so multiply that by the number of times you want the projectile to maneuver.

Thank you, that basically means the cost is negligible compared to the drives.

 

[wbnc]

I mostly agree with you, apart from:

Combat does not occur at those ranges. At 50,000km, sensor detail is NONE for radar and lidar, and on minimal for thermal. You can tell something artificial is there but not much else. to be able to tell what you are shooting at you would have to close to 50,000Km just to get a basic outline of the target. beyond that range your firing at heat blobs. even if you have all the extra sensor systems available you cant gt a decent idea of the tactical situation at 300,000Km

In wartime a missile-heavy fleet will launch on an approaching unidentified fleet at extreme range. It can't afford to let a beam fleet to get into firing range.


If large empires fight the campaigns are likely to be large, much larger than a single system. The aggressor is likely to be in a hurry to get to crush this system and get to the next.

That is one of many potential tactics. Blitzkrieg. but it has inherent vulnerabilities.