Vehicle of the Week: Manta and Moray Attack SubmarinesAll proposed fan variants should go in the Workshop thread.Author's Note: Since we're venturing into murky waters here, you may want to look over the various special rules for submarines in Total Warfare. Underwater movement rules are on page 57, underwater LOS on page 108, and underwater weapon ranges for standard rules play on page 107. Finally, the hull breach rules are on page 121.BattleTech has typically been a land combat game with occasional forays into the air. Nearly from the beginning, though, there have been a few tentative pokes at sailing the stormy seas, a bit of dabbling with the Monitor, getting the feet wet with the Neptune. More recently, the support vehicle rules have allowed a proliferation of blue water craft and the mobile structure rules got their toy boat with the Wyrm submersible fortress published in Jihad Hot Spots: Terra. The Wyrm was mentioned to have a parasite complement of supporting Manta fast attack and Moray heavy attack submarines; comments by Welshman during the Wyrm's special feature article indicated that the numbers in JHS: Terra were halved by accident, leaving it with eight Mantas and four Morays at the end of the day and dashing my hopes for Alacorn "mobile deck guns".
That isn't where their story began, though, merely where we found the book opened to; neither vehicle sprang forth from the mind of Cameron St. Jamais. Instead, both date back to the Star League as a specialized defensive asset. The pair were jointly designed by the Royal Nelson Memorial Shipwrights of Portsmouth (their primary facility is at Portsmouth Harbour in Hampshire, England, site of HMNB Portsmouth today) and Sungdong-STX Shipbuilding for service in the SLDF's Combined Armor, Air, Naval regiments. Extensively used throughout the Terran Hegemony, their numbers were heavily reduced in battle with Amaris and the two designs were rendered nearly extinct off of Terra in the Succession Wars. (Given the advanced technology present on each, I suspect that those remaining were heavily downgraded if not outright stripped for parts, but we don't have the stats for those designs. A few notional stabs at the subject have been posted in the Workshop thread.)
The Manta is the smaller, faster hull. Reputedly derived from catamaran surface hulls, the 50 ton Manta was intended to be able to rapidly respond to threats across a wide engagement area and the powerful GM 320-rated extra-light fusion engine drives it to 119 kph, a little over 64 knots, making it somewhat faster than the estimated speeds of many modern anti-ship torpedoes in a sprint. Despite the use of the best engine available, it was still 17.5 tons, over a third of the ship's tonnage, and limited space for the three-man crew and the weapons systems. Nine tons of ferro-fibrous armor was arranged 52/39/31. The weapons load is a bit light for a vehicle this size but between the speed and the need for diving equipment, I'm not complaining. A Selltext Aqua extended-range large laser points forward along with a Sea Harvester Six Pack short-range torpedo launcher. The lack of CASE is not something I'm ever especially fond of but here, with the relatively limited ammo duration, it
probably isn't a large problem. As TRO3085S notes, this is a vehicle designed for slashing attacks, using the ERLL to open someone's armor and then putting a spread of torpedoes into it. I suggest operating them in packs much like the Kriegsmarine did with U-boats in World War II. The Republic of the Sphere designed a support Manta with an LRT 15 and twin ERMLs to supplement the original design. Keep in mind when considering this change that the IS ERLL's range is only 3/9/12 underwater, while the ERML's is 3/5/8.
Sungdong was a large, widespread manufacturer involved in the construction of a number of different submarine designs over the centuries. Their 140 ton Morays are nearly three times the size of the smaller Mantas, though a 390-rated Electro-Motive XL Fusion engine keeps it moving at 54 kph. Their ten man crews are kept safe by 18 tons of armor arranged 75/66/60/55 with CASE added. The design is liberally equipped with torpedo launchers and intended to support the smaller fast attack submarines, letting them drive the enemy before the Moray for handling by the sort of firepower that makes assault 'Mechs just a bit nervous. The turret, equipped with a Sea Devastator 10 Rack Long-Range and Sea Harvester Six Pack Short-Range torpedo launcher along with two medium lasers (standards in the Star League era, ERMLs on the new Word and Republic Morays), is only the start of your problems. The forward hull supports two massive Sea Devastator 20 Rack LRTs fed by three tons of ammunition for a combined 18 round endurance, with another Sea Harvester SRT 6 backing them up. The stern is protected with a second LRT 10 and the final SRT 6. Between them, the LRTs split 36 rounds while the SRTs have no less than 60 between them. Personally, I'd probably have allocated the ammunition load a bit differently but considering the lower speed of the Moray, the number of times it can keep the forward LRTs on some opponents may justify the lower endurance.
Tactics for something like this are just a bit hard to envision because of the dearth of naval hardware at our disposal. The Manta and Moray are at the top of their respective niches. Indeed, the Manta has no known canon challengers but the mix of capabilities looks solid. More or less, I'd suggest operating it like you would a hovercraft with similar armament in open terrain, slashing in at someone and then sprinting out of the engagement zone to turn around and present your bow once more. The SRTs are going to be useful for forcing multiple breach checks, the fastest way to get rid of an opponent underwater. The Moray is more like an overgrown Rhino and I encourage you to point it at the enemy and bury him in torpedo hits. Keep in mind that with the recent proliferation of sealed tanks and underwater combat 'Mechs, we're starting to see more use for this sort of design, but as specialists, the Manta and Moray have a distinct edge against intruders into the depths.
Attacking them is difficult and best done with other torpedo-armed units. Consult the table on page 107 of TW for why., but Engaging the Manta with IS pulse lasers is an exercise in extreme frustration thanks to the 1/3 reduction in range. Clan pulse lasers have more luck but then they usually do. The best response is to use your own submarines but the in a pinch, 'Mechs with the right sort of armament (energy weapons) can defend themselves, as can amphibious vehicles. Your job is made easier by the fact that any unit underwater has to roll 2d6 when the unit takes damage to a location, and on a 10 or greater, the location's integrity is lost; this happens automatically when all the armor is gone. That's an instant kill on a vehicle but a little bad luck can cripple or kill a 'Mech, so don't get cocky.
Image Reference The Manta is
here, while the Moray
lairs here.