Deep Site Meson Guns in Invasion:Earth

[pzmcgwire]

Are there any canon write-ups of deep-site Mesons guns?

The only one I can find is in GDW's Invasion Earth game where Deep Site Meson guns appear to be lumped into the Solomani's Planetary Defense Units.

The Solomani have a number of immobile and mobile Planetary Defense Units that can bombard surface targets and engage spacecraft in orbit.

There are no hidden placement rules so all of these are placed in known locations with the Starports and the Urban areas being the location of the immobile PDU Corps and Divisions respectively.

There are a smaller number of mobile planetary defense regiments.

These are the only planet-bound units that can engage spacecraft and other surface units through bombardment, so I think these must include Meson Guns.

Surface attacks are limited to 3 hex ranges, which appears low. Meson Guns are typically able to fire to orbital range, so should be able to target any location on Earth, especially since Meson Guns do not need to worry about intervening terrain.

It could be a targeting issue with units not being locatable in ground clutter, but if the same units can engage units in orbit

Are Meson Guns not represented accurately in Invasion Earth?

Are there any canon writeups using FFS or Striker detailing a deep-site Meson Gun?

 

[Garnfellow]

The MegaTraveller COACC Handbook is probably the single best source for information on deep meson gun sites, though references are scattered throughout MT and TNE. Here are the most relevant details I can put my hands on:

On many worlds with Average Stellar (TL11) + technology, COACC personnel crew deep meson gun planetary defense installations far beneath the planetary surface (COACC 8).

The most common form of active [planetary] defense in the deep meson gun site. A deep meson gun is a meson gun of ship ordnance size buried in a deep underground chamber. As a planet itself is transparent to the meson beam, the meson gun can fire at any target desired, while the site itself is effectively impossible to locate. Only when the gun site's surface sensors and target acquisition devices have been destroyed or captured can the gun be silenced. This generally requires the use of ground troops or extensive planetary bombardment. (World Builder’s Handbook 96).

Ship-size meson guns buried in deep underground pits are major planetary defensive weapons. They may be fired out to Planetary range (50,000 kilometers), and since the planet is effectively transparent to them, they may fire at any angle toward any target desired from their pit. Deep meson guns are effectively impossible to silence. The only way to knock out these weapons is to locate and destroy their target acquisition and fire control sensors. This is a major mission for jump troop commando raids.

Meson gun combat between planetary deep gun pits and nearby starships is conducted exactly as space-to-space combat with one exception -- only sensor hits have any effect on the deep meson gun site. However, large portions of countryside and urban areas are reduced to rubble by meson gun fire. These effects may be optionally applied by the referee (COACC 73).

Arrival Vengeance has a brief description of a meson gun site on Kamurinmur (2224 Gushemege), and Vampire Fleets has a map of a planetary defense installation on Promise (Diaspora 2827). Long story short, you can use the statistics of a ship-based meson gun if you needed to resolve something in game.

 

[pzmcgwire]

Thanks for those references.

I ran the numbers from TNE's FFS. It looks like a ground-based Meson gun with an extreme range of 500,000 kilometers needs an effective tunnel length of 62.5 meters or an actual tunnel length of ~ 52 meters.

Promise a tech level 14 world had at least two deep site meson guns as described in Vampire Fleets.

How many and what size meson gun installations would a larger and more densely populated (e.g. valuable) high tech world like Terra have?

 

[Proneutron]

Only when the gun site's surface sensors and target acquisition devices have been destroyed or captured can the gun be silenced.

Obviously untrue as a ship mounted meson gun can destroy it. Densitometer can pinpoint the location underground.

 

[whartung]

It should be noted that a deep meson site is effectively a buried starship, with no armor, no j-drive (that would be Bad), no m-drive.

It doesn't necessarily need a dedicated power plant (it could be power from "the grid").

But it needs fire control, a sensor suite, 24 hour crew accommodations, etc. I dunno if they'd bother putting a meson screen on one or not.

Consider a typical high powered meson gun is about 100M long, and you end up burying, roughly, a 38000 dTon starship in the ground, since you need a HUGE sphere (like an observatory, only buried).

FF&S has details on building the mount and tunneling out the chamber.

I'm surprised that FF&S doesn't seem to mention the blast radius of the gun. Striker used to talk about this, and even Striker II makes no mention of the area of vulnerability.

In space, this is less of an issue. But on land, it's a big deal.

 

[Condottiere]

Planetary Defence: Hulls and Deep Site Meson Weapon Systems

1. I'm kinda inclined to believe that it's a triple hulled sphere.

2. The two extra hulls are required to move the meson gun on two axis required to aim at any particular target.

3. In theory, you could just hollow out a cave and use the hamster cage mechanism, again multiplied by two, but the fundamental rule in High Guard to prevent multiple instances of spinal mounts in the same hull assumes that spinal mounts have to be anchored in the hull, to compensate for recoil.

 

[Proneutron]

but the fundamental rule in High Guard to prevent multiple instances of spinal mounts in the same hull assumes that spinal mounts have to be anchored in the hull, to compensate for recoil.[/I]

Mesons are almost massless that that wouldn't be the reason..

 

[whartung]

So, using rough numbers.

Using the Striker GWP numbers, and a 2% military budget (being in the Marches) for Regina (700M people, TL-12), that's a budget of 358BCr.

Striker divvys that up 60/40 between the Navy and Army, but makes them split planetary defenses.

TL-12 (which is not the finest in terms of Meson performance) can build up to a K gun.

A K gun costs 10,000MCr. A power plant for that gun runs 9,000MCr. 19MCr total, just for machinery. Toss in an 5,000MCr to dig the hole and such. Call it an even 25,000MCr.

A ship mounting the K gun, with OUT a jump drive, but M6, A6, Computer 9, is 40K tons, and runs 64,000MCr. So, it's about 2:1 deep mounts vs space ships.

A J3 capable ship runs about 85K tons, and runs 115,000MCr, so we're at 4:1 mounts to ships.

But Regina has a Navy budget for 1 of those ships.

So, it could build 1 starship, or 4 deep mounts.

Also, since there's, a 10% maintenance fee, Regina, in theory, could maintain 40 deep mounts. This, is a formidable target. I would not want to be on the receiving end of 40 "unstoppable" K Guns in a turn.

Of course, why these wouldn't be TL 15 guns with TL 15 supplies is a different problem. (You'd think the Imperial Navy would like to keep Regina around...)

Now we're talking about 10,000MCr for an N gun mount. 100 N guns...*gulp*

Anyway, just to give a hand wavy perspective as to the costs of these sites in contrast to mobile units.

 

[Garnfellow]

Carlobrand had an earlier post thinking through this question:

http://www.travellerrpg.com/CotI/Discuss/showpost.php?p=398455&postcount=87


Here was another poster's attempt at estimating the number of sites:

http://www.travellerrpg.com/CotI/Discuss/showpost.php?p=55892&postcount=92

He got to 24 sites for Terra.

 

[pzmcgwire]

GURPS Starports and I:E

> He got to 24 sites for Terra.

Thanks. GURPS Starports states a Class V Naval Base (Sector fleet base) would have 25+ deep meson sites, while a Class IV Naval Base (Subsector fleet base) would have 1-2 deep meson sites.

That seems consistent. The previous analysis looked at Invasion: Earth and assumed about a squadron equivalent (8 spinal mount equivalents) at each of the 3 corps level Planetary Defense Units whose bombardment rating of 9 is easily twice as big as any Imperial squadron in the game.

The way I:Earth models Planetary Defense Units by giving them an attack against bombarding naval squadrons, land units, or units in close orbit during the bombardment phase and then also an attack against any landing units in the subsequent landing phase of a turn.

So it seems Imperial Marines would not want to trying landing close (within 3 land hexes (3600km) to a site defended by an active Planetary Defense corps.

 

[AnotherDilbert]

But Regina has a Navy budget for 1 of those ships.

So, it could build 1 starship, or 4 deep mounts.

And if you build the ship, the Imperium will thank you for your contribution to the colonial fleet and jump it to the front. I.e. it will not be available when you need it.

The deep meson gun will stay put.

A J3 capable ship runs about 85K tons, and runs 115,000MCr, so we're at 4:1 mounts to ships.

Much, much worse... You can't build a good battleship at TL-12, e.g.:

BB-R1366F4-441106-348K3-0    MCr 205 151     180 000 Dton
bearing     E   1 EE11Z                        Crew=2 359
batteries   L   1 LL11Z                             TL=12
                  Cargo=429 Fuel=66345 EP=12345 Agility=6

Dual Occupancy                                      430   205 151
                                     USP    #      Dton      Cost
Hull, Streamlined   Custom             R        180 000          
Configuration       Needle/Wedge       1                   21 600
Scoops              Streamlined                               180
Armour              4                  4         18 000    12 600
                                                                 
Jump Drive                             3    1     7 200    28 800
Manoeuvre D                            6    1    30 600    15 300
Power Plant                            6    1    37 035   111 105
Fuel, #J, #weeks    J-3, 4 weeks            3    66 345          
Purifier                                    1     1 990        11
                                                                 
Bridge                                      1     3 600       900
Computer            m/6fib             F    1        14        83
                                                                 
Staterooms                                  4        16         2
Staterooms, Half                         2355     4 710       589
                                                                 
Cargo                                               430          
                                                                 
Spinal              Meson K            K    1     8 000    10 000
Bay                 Particle, 100 t    8    1       100        36
Bay                 Repulsor, 100 t    6    1       100        11
Triple Turret 2/bat Missile            3  820     1 640     3 690    1640 turrets organised into 820 batteries.
Triple Turret       Beam               3   20        20        60
Single Turret       Fusion             4   20        40        40
Triple Turret       Sand               4   20        20        15
                                                                 
Nuclear Damper                         1    1        50        50
Meson Screen                           1    1        90        80
                                                                 
Nominal Cost        MCr 205 151,36       Sum:       430   205 151
Class Cost          MCr  43 081,79      Valid        ≥0        ≥0
Ship Cost           MCr 164 121,09

GCr 200 and it is nearly unarmoured...

In the end a TL-14 Zho cruiser will kill that BB without breaking a sweat.

 

[whartung]

So it seems Imperial Marines would not want to trying landing close (within 3 land hexes (3600km) to a site defended by an active Planetary Defense corps.

The beauty of a deep meson site is that they're built and managed by AT&T -- reach out and touch someone. You simply need to get a forward observer out to the enemy units anywhere on the planet. That it getting easier and easier every day.

Much, much worse... You can't build a good battleship at TL-12, e.g.:
In the end a TL-14 Zho cruiser will kill that BB without breaking a sweat.

Yea, I never suggested it was a good ship, it was a Meson tube with a jump drive.

TL-12 isn't a good place for meson tech anyway, and this just opens that whole "why isn't all the military tech at TL-15 anyway" can of worms.

Of course, the other debate is whether the meson sites are worth it compared to high volume missile swarms. Missiles are pretty cheap, sending out 100-200 missiles at a time can make for a busy day for an invading fleet.

 

[Condottiere]

Overheads.

Infrastructure, recruiting, retention, pensions, veteran health care.

Military industrial complex inefficiency, pork barrelling, kickbacks, golden parachutes.

 

[AnotherDilbert]

Of course, the other debate is whether the meson sites are worth it compared to high volume missile swarms. Missiles are pretty cheap, sending out 100-200 missiles at a time can make for a busy day for an invading fleet.

Only spinals can kill ships. Missiles can only temporarily inconvenience enemy ships, unless they are completely unarmoured.

A few (hundred) missiles will mostly not hit or bounce on dampers, especially against a technologically superior foe.

Missiles have to be launched from the surface, whereas mesons can be buried. Mesons are more difficult to destroy.

Deep meson spinals are scary...

 

[Proneutron]

Simple solution; if your invasion fleet is close enough for planetary mesons to hit you they already lost. You can overwhelm planetary defenses with nuc missile swarms from stand off range. So, you will be offering surrender terms if they want their planet to remain habitable.

 

[Condottiere]

That was the argument for the Royal Navy and coastal defence.

It has to be like an onion.

Layered.

 

[vegas]

It strikes me that a key weakness of deep meson sites is immobility and hence easy targeting if you know where they are.

How hard is it learn their locations? These are huge installations and design and building them out is going to involve a huge engineering effort. There will be ongoing staffing and maintenance. There are so many opportunities for human or physical intelligence to get the locations and a psionic enemy which is uniquely enabled to exploit those weaknesses and years of time available to do it.

Of course, as Proneutron suggests, if you are going to glass the planet it doesn't matter. Otherwise, if you want to occupy the target, you do the work.

 

[Grav_Moped]

It strikes me that a key weakness of deep meson sites is immobility and hence easy targeting if you know where they are.

How hard is it learn their locations? These are huge installations and design and building them out is going to involve a huge engineering effort. There will be ongoing staffing and maintenance. There are so many opportunities for human or physical intelligence to get the locations and a psionic enemy which is uniquely enabled to exploit those weaknesses and years of time available to do it.

Of course, as Proneutron suggests, if you are going to glass the planet it doesn't matter. Otherwise, if you want to occupy the target, you do the work.

Immobility is relative. Strip the weapons system down to the gun, a 1G maneuver drive, and a power plant and fuel, and run it in an underground "racetrack" tunnel. Use grav-control magic to spoof densiometers, place decoy power plants to spoof neutrino sensors. Meson shield part or all of the "track".

Build multiple decoy racetracks, consider using them as alternate sites too if you can sneak the weapons systems around (they do have their own grav drives, and you can disguise them as spherical-hulled ships at the very least).

This is about the highest security priority a world would have.

And if you can plausibly hide system defense boats in oceans, why not meson monitors?

 

[vegas]

I have thought about the subway solution too, but then it doesn't need to be "deep", it needs to be long and complex. Anyway, that isn't how canon presents them.

Underwater monitors seem the way to go to me, assuming you have an ocean.

 

[Garnfellow]

The MGT Solomani module also has a good discussion of meson gun defenses, and touches on the submarine concept:

Solomani planetary defence installations built since the Solomani Rim War have begun to install deep underground geothermal core taps feeding high-energy capacitor arrays (similar to those used in jump drives). These power sources eliminate the neutrino signature of the meson gun but are less powerful and more expensive to construct than fusion reactors. The need to recharge the capacitors limits this emergency rate of fire to one shot every few hours or requires the use of smaller installation equivalent to bay-size weapons. This limits the ability of the meson gun as a factor in a fast-moving space battle but significantly complicates matters for planetary sieges and ongoing invasions.

A related development used on a few TL13-14 Solomani worlds with deep oceans is the space defence submarine. This is a large nuclear submarine with a single bay weapon-sized meson gun installation, which patrols in the deep ocean or under a planetary ice cap. Although firepower is limited, mobile meson gun subs are harder to track with neutrino sensors than static installations. Engaging them may require sending grav armour or starships to operate underwater (111).