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A. T. Mahan

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  1. A. T. Mahan

    Competition Suggestions

    I'll let the PT Boat/FAC competition stew for a while -- I'm not as into designing heavy tanks, so I'm probably going to let Moo be the draftsman for it. Also, I wrote up the contest entry and flavor text over the course of about five hours, in one sitting. If I have time tonight I'll write up a modern USN one on my google drive.
  2. A. T. Mahan

    Competition Suggestions

    Backstory: The Confederal Republics of Greater New York, Connecticut, Massachusetts Bay, New Jersey, Rhode Island, and the Providence Plantations is the major power in the Northeastern region of the former-US. A Federal Republic consisting of the States of Long Island, New York, Vermont, New Hampshire, Connecticut, Rhode Island and the Providence Plantations, Massachusetts Bay, Cape Cod, and the Southern Unincorporated Territories, encompassing most of prewar Pennsylvania, New Jersey, and Ohio. Founded by the survivors of the war in New York City shortly after the war, it is one of the most stable political entities in the region. High literacy and education rates, the survival of large caches of prewar information, the relative lack of damage from the war outside New York City, Boston, and parts of Philadelphia have allowed the region to become a manufacturing powerhouse. The existence of several major pre-war manufacturing sites in CRS territory, including the Philadelphia, Portsmouth, and Brooklyn Naval Shipyards, General Dynamics-Electric Boat (Which was spared from destruction by a dud 475-kiloton warhead), Bath Ironworks, Watervliet Arsenal, the Sikorsky and General Electric plants, and several major research facilities has brought the CRS to approximately the technical level of the early to mid-1950s US, although they are farther along in some specific areas -- gas turbine technology, electronic computers, high strength fibers, and high-strength ceramics being particularly noteworthy examples. The economy of the CRS is predominantly focused on trade, aviation, and shipbuilding. Possessing two of the largest deepwater harbors on earth (New York and Boston harbors), the Republican States' merchant marine is the largest in the world, and there is regular trade with Western and Mediterranean Europe, Africa, southern Asia, and the Antipodes. As a corollary to this, they maintain a large and capable navy, predominantly based on updated and modified Second World War designs. The states of New York, Long Island and Connecticut are particularly influential in aviation, with nearly 50% of total North American aircraft production divided between Long Island, the Buffalo metropolitan area, and various locations in southern Connecticut. This has provided the Navy with substantial advantages in naval aviation, with the first CRS aircraft carrier, CRSS Kitty Hawk, a modification of the Ranger design of 1925, completed in 2218. Currently, the backbone of the fleet are the three ships of the CV-5 class (Bethpage, Azores, and Buzzard's Bay) and the first four ships of the CV-9 class (Newark, Troy, Schenectady, and Ithaca), (derived from design SCB-125A), with more under construction. Additional naval air forces include maritime patrol aircraft, predominantly B-17 and B-24 derivatives, antisubmarine warfare aircraft derived from the Lockheed Constellation, and several executive transports. Year: 2243 The Navy of the Confederal Republics of Greater New York, Connecticut, Massachusetts Bay, New Jersey, Rhode Island, and the Providence Plantations request proposals for a Patrol-Torpedo Boat. The Chief of Naval Operations, having determined that our current force structure (Detailed in Appendix A) is insufficient to protect our international trade at sea, in the Great Lakes, on the various rivers of the North American continent, and to defend the seacoast, has determined that there is a doctrinal need for such craft. The proposals will be evaluated against two benchmark Government designs — SCB-92F and SCB-238Q. These will be presented with the beginning of the contest. (December 7, 2018) The specifications are as follows: Displacement: Not more than 75 tons at combat weight. This is non-negotiable and a hard limit. Any design with a combat weight, defined as the vessel with full complement of crew, armaments, ammunition, fuel, oil, food, potable water, and a 100lb/man allotment for personal effects, in excess of 150,000lb will be disregarded. This limit is due to restrictions on transport capacity for transoceanic shipment. Speed: Threshold: 43.5 knots sprint, 39 knots sustained at combat weight, 45 knots at light ship. Objective: 45 knots sprint, 43.5 knots sustained, at combat weight 48 knots light ship. Complement: Threshold: Not more than three officers and 14 enlisted. Objective: Not more than two officers and nine enlisted. Potable water: Threshold: Not less than 150 USCS gallons (1,320lb) Objective: Not less than 200 gallons (1,750 lb) Range: Threshold: Not less than 250 nautical miles at 35 knots, not less than 500 nautical miles at 15 knots, at combat weight. Objective: Not less than 350 nautical miles at 35 knots, not less than 750 nautical miles at 20 knots at combat weight. Engines: Threshold: Not less than two or more than four engines. Not less than two nor more than four propellers. Machinery spaces must have both an AFFF blanket system and handheld extinguisher bottles of sufficient size and type. Fuel tanks must be self sealing and must not have any wiring run through them. The vessel must be able to conduct underway replenishment Draft: Threshold: Not more than six feet, six inches, including screws. Objective: Not more than five feet, one inch including screws. Turning circle: Threshold: Not more than 435 yards. Objective: Not more than 350 yards Fittings: All fittings are to be corrosion resistant, and of the standard Navy type. All cleats will be of the Herreshoff double-taper type. Accommodations: Sufficient sleeping quarters for the crew are mandatory. There must be escape lighting in berthing spaces sufficient to guide the crew topside in total darkness or smoke. Sufficient ventilation to accommodate the smoking of tobacco below decks is required. Sufficient galley space is mandatory, including an electric cooktop and oven, preparations surfaces. Sufficient storage to secure all cooking implements while underway is required. Food storage: Threshold: Food storage sufficient for five days. Objective: Refrigerated storage for seven days. There shall be provisions for personal retention lanyard and harness systems to prevent loss of crew in adverse sea states. Provision shall be provided for storage of individual small arms of the Crew, including 1x M1994/18 5.56mm carbine for each man and officer, 1x Colt Government .45 automatic or Browning Hi Power 9mm automatic pistol for each officer, and sufficient supplies of ammunition (210 rounds per carbine, 100 rounds per pistol per day of supplies) for each. Communications fit: Threshold: 1x blinker light, 1x standard type 50W VHF secure TBS radiotelephone (the exact set will be provided, AV/VRC-12 equivalent with VINSON), LORAN radio navigation system. Objective: 2x blinker light, 2x standard type VHF secure TBS radiotelephone, 1x secure LF/MF/HF radio set (Units will be provided), LORAN radio navigation system. Sensor fit: Threshold: 2x acoustic depth sounder (bow and stern), 1x manually operated optical rangefinder, 2x 30” arc searchlights. Objective: 1x AN/SPS-5 surface search radar (S-band Raytheon SG), 1x optical rangefinder, Provision for a towed array sonar system and sonobuoys Searchlights for all major caliber gun mounts. The vessel must comply with all peacetime navigational lighting regulations. Torpedo armament will be provided by the Naval Torpedo Station, Newport. It will consist of not less than two nor more than four torpedoes of one of the following types: 21” Mark 16 MOD 2 (USN Mark 16 torpedo with wake-homing head built off a Mark 35 seeker). 4,000lb, 11,000yd range at 46.2 knots, 746lb HBX-3 (Re=1.75) 22.4” Mark 25 (New-productio USN Mark 25 torpedo) 2,400lb, 2500yd range at 40 knots, 725lb HBX-3 (Re=1.75) Other armament: Threshold: Not less than: 1x 37mm automatic gun (100 rounds) 2x twin .50 Browning machine guns (2,000 rounds) 2x 20mm machine guns (2,000 rounds) 2x depth charge racks at stern (6 500lb depth charges) Mounts for no less than 10 5” HV or AS rockets (storage for three sets of reloads) Objective: Not less than 1x automatic gun not smaller than 40mm bore and not larger than 3” bore (250 rounds) 1x automatic gun not smaller than 35mm bore and not larger than 38mm bore, (250 rounds) Not less than two 20mm machine guns (2000 rounds) Not less than two twin .50 machine gun mounts (2,000 rounds) Mounts for not less than twenty 5” rockets (storage for five sets of reloads) Seaworthiness: Threshold: The vessel must be capable of making extended (1,000nm) redeployments on its own hull. It must be capable of conducting combat operations to minimum standards with a skilled crew to Sea State III, must not be damaged by 24 hours at Sea State IV and must survive Sea State V. Objective: The vessel must be capable of making 2,000 nautical mile redeployments on its own hull. It must be capable of conducting combat operators to minimum standards to Sea State IV, must not be damaged by 24 hours at Sea State V, and survive Sea State VI. Wing-in-ground-effect craft will not be considered, as they are aircraft. Guidance and Opinions: The Navy greatly prefers supercharged gasoline engines to diesel-cycle engines, and is interested in gas turbine propulsion. The Navy does not consider steam turbines suitable for motor torpedo boats. The Navy prefers that the vessels be less than 25 feet in beam to permit road transport by truck and trailer. The Navy prefers nonmetallic construction for small craft, as degaussing is expensive and aluminum corrodes very rapidly. The Navy is interested in fully submerged hydrofoils, but current experimentation has shown that either exceptional skill on the part of the helmsman or a computer system beyond the state of the art is required. If a control method is forthcoming, the Navy would be very interested. The Surface Warfare Officer community would prefer the vessel to have splinter and machine gun bullet protection and an enclosed bridge. They also would very much like a reduced radar cross section, as the probable enemy has developed rudimentary radar systems. The Underwater Demolition Team boat crews would prefer the vessel have mufflers or otherwise be quiet, and ask if accommodations could be made for transporting a couple rubber dinghies and a free space for a ladder somewhere along the gunwale. The Office of Advanced Technical Development would like to know if you could design the vessel for but not with something fairly fragile aft of midships, about 16’ wide, 18’ long, 14’ tall, and 26,000lb, and if you could design a mainmast capable of supporting a 3,000lb radar system. The Navy would like stabilized main gun mounts with power traverse and a holographic weapon sight, but they are not required.
  3. A. T. Mahan

    Competition: Tank Design 2239

    I would like to clarify that the Pacific Car and Foundry Company has not tried to bribe any of the judges. We spent the bribe money on bonuses since we got the submission done in five days
  4. A. T. Mahan

    Competition: Tank Design 2239

    @LoooSeR The autoloader mechanism is a slightly resized version of the aircraft mounted version of the Molins Auto Loader Mark III. The only noteworthy changes were a slight lengthening of the magazine and action to accommodate the 57x480mm cartridge, from the original 57x441mm cartridge. It operates most similarly to a long recoil small arm, with the semiautomatic vertically sliding breechblock falling at the rearmost extent of the recoil stroke, with ejection of the spent case occurring during counterrecoil. The new cartridge is fed into the action by a springloaded arm tripped by the passage of the breech near the end of the of the counterrecoil stroke, and the breechblock is actuated by the rim of the cartridge when the case is fully seated. Upon firing, the loading arm is recocked by the force of the recoil stroke, and the cycle begins again. The loading arm is visible in an intermediate position on this QF 6pdr Type M Mark I with Auto Loader Mark III Initial loading is accomplished by either manually cocking the loading arm, opening the breech, and inserting a case as in a manually loaded gun, or by cocking the loading arm, opening the breech, and actuating the loading sear override handle, which triggers the loading arm. The magazine is loaded manually, one round at a time, by inserting the nose of the projectile and rim of the cartridge case into their respective feedways in the magazine. The ammunition feedways in the magazine are visible in this image of a 6pdr Type M Mark I with Auto Loader Mark III on a test mount Loading is primarily intended to be accomplished by the commander, as the 24-round magazine provides substantial capacity compared to, for example, the eight rounds of the Bofors 40mm automatic guns or the 16 rounds of the 57mm AZP S-60. Furthermore, as the gun is primarily intended for use against armored ground targets and has a relatively mediocre HE shell due to the very high muzzle velocity and thus thick shell walls, ammunition expenditure should be comparatively limited. It is also worth considering that the gun will likely not be fired in bursts, but in semiautomatic fire, where the automatic loader and 24 round magazine would reduce engagement times dramatically when compared to, for example, a manually loaded gun of similar performance.
  5. A. T. Mahan

    Competition Suggestions

    I'm working on an idea for a contest, a contemporary fast attack craft for the USN, probably to be posted in mid-late december. I'm probably going to leave the requirements fairly open-ended, but it'll need to fit within a given budget and meet the appropriate dimensional, weight, and performance specifications -- I will also do my best to point people in the appropriate direction for helping to determine seaworthiness and performance if that's needed. I'm hoping this would be an interesting challenge, and one that is accessible to more people than a full-on warship design. I'll also be cooking up an un-scored entry as a baseline/template. Does that sound ok?
  6. A. T. Mahan

    Competition: Tank Design 2239

    Flavor text: Excerpts from Snapshots: The Combat Record of the Medium Tank M4 As Told by The Crews That Fought Them, 2289, Renton University Press: MG David Mcneil, CRA (Ret). Chief of CRA Armored Force from 2278 to 2282, MG Mcneil was the only Chief of the Armored Force to have begun his military career as an enlisted soldier. He also was a member of the 1st Sqdn (Tank), 1st Armored Brigade’s “First Class”, the first tank unit to be transitioned to the Medium Tank M4. Known for his highly aggressive leadership style and personal bravery, Mcneil has the dubious distinction of having bailed out of a Medium M4 from every hatch and every crew position. He has 38.875 tank kills and a further 47 probable kills, and has received eight Purple Heart medals. A renowned polymath, Mcneil holds advanced degrees in mechanical engineering and history, and currently splits his time between teaching military science at the Cascadian Military Academy and consulting with several defense contractors. On first encountering the Medium M4: Up until that point, we had been using the Medium M3, a fairly serviceable, if dated design by the late ‘30s. At that point, I was a fresh-faced nineteen year old private first-class, and while we knew our M3s weren’t quite the firebreathing impenetrable powerhouses that some of the more sensational papers made them out to be, we were damn proud of them and we thought they were pretty hot stuff. I remember the day that we were first introduced to the Medium M4. Our Squadron was loaded into a convoy of deuce-and-a-halfs and we were driven to the Renton Locomotive plant. Once we got there and had been shepherded to a set of bleachers outside this big field, our CO, Mike Anderson, a man who I then hated but would come to respect more than anyone except perhaps God and my mother, stood in front of us, and explained why we were there -- the Government had decided we were to get a new tank, they’d bought one, and they had chosen us to be the lab-rats for the field trials and IOC. He then called us to attention, turned on his heel, and waved to a guy by the corner of a nearby building, and we heard it for the first time. We all knew what a tank starting up sounded like -- you had the whine of the solenoid, the coughing and then roar of the engine as it spun and caught, and then a rumble as it settled down to idle. This was different -- all we heard was a quiet whine, which built to a sort of whistle. Of course, we’d all heard about jet engines, and seen video of the old pre-war Abrams, and some of us even read Aviation Week and knew that PacAero was working on turboprop and turbojet aircraft, but we figured that a tank turbine was a technical impossibility in the late 2230s. The first thing we saw was the gun, which is one of the better ways to spot an M4 Medium. The damn thing is so long that it’s hard not to miss it, but we saw this gigantic barrel coming around the corner and one of my very good friends, Tony Anglio, whispered to me something like “This has to be some kind of joke, that gun’s bigger than our friggin tank!”. Then, the hull just sort-of floated into view. The double-acting torsion bars and massive shock absorbers on the M4 gave it a very distinctly floaty ride, since they were designed for a substantially heavier vehicle than the already-heavy M4. The thing that really struck all of us, I think, was how quiet the damn thing was, despite its large size. That said, the M4 was just a mean looking bastard. The M3 Medium was almost cute in its very traditional construction, and well-proportioned lines, while the M4 looked strange in comparison. We wouldn’t find out until later exactly why it had all the tiles and the fairly flat armor, at the time we figured it was steel, and a lot of it. The M4 was always full of surprises. Once we saw it and got used to the sound, we figured, well, okay, it’s going to be pretty slow -- it’s got all that thick armor and that great big gun, and it’s fairly small. As if on cue, when it got right in front of the bleachers, the driver hit the gas and the damn thing took off! We would come to appreciate the amount of time and effort the Renton boys had put into the vehicle, and the lengths they had taken to finally give Cascadian tankers a technological edge over our Californian enemies. On actually fighting the M4 Medium The thing to keep in mind about the M4 -- and I mean the M4, not the M4A1 or A2, because each of those was almost a different tank in how heavily they upgraded them -- is that even for all its advancements, it was still a product of the era. Yes, it had a very advanced gun-laying system and two-axis stabilization, but they were fairly slow, and a lot of the better gunners got very adept at using the reticle to range the target. The automatic rangefinder still took a good four seconds of steadily tracking a target with an unbroken sight picture, not an easy feat in combat, and the mechanism really wasn’t technically mature, but it worked enough of the time to be a suitable stand-in for the laser rangefinders that replaced it. Oh, and the damn thing would stop working whenever the Contact explosive reactive armor tiles near the rangefinder blisters went off -- half the time we either took them off or replaced them with a chunk of solid steel, just so that we didn’t have to recalibrate the rangefinder. They never really fixed that, either. At first, the M4 had hands-down the best armor in the world -- unsurprising, since it was more or less an unabashed copy of the HAP-1 package off the Prewar M1A1HA Abrams. It was easy to get lulled into a false sense of security by the ERA and the composite armor, and forget that the thickest the hull got was only three inches. It was quite common for the detonation of the ERA tiles to dent and bend the ¾” outer shell of the tank, especially the RAT tiles on the bow -- when they went off, it was something like 16 pounds of Composition B throwing a 12-pound steel plate into the hull. On the Battle of Yreka, the combat debut of the M4 Medium The gun and mobility on the M4 were exemplary. When we first hit the battlefield it gave those Calif[ornian]s a shock, let me tell you. I remember the first combat action we took. We were dug in on a ridgeline, had a line of sight out, damn must have been four kilometers or more. We’d just had our breakfast and buttoned up when they hit us. That was the first time I’d been under the “VT” shells. Proximity fuse, you see. All the fun of tree bursts without the trees. Then they laid in smoke. So thick you couldn’t hardly see the end of the gun barrel out the periscope. Played hell with the automatic rangefinders, not that they worked much anyway. Somehow we made it work. With a battalion of Califoria’s finest coming at a company of Cascadian Regulars, there’s not much of a choice anyhow. We held fire on ell-tee’s orders until a thousand meters. Then the whole platoon let go in one volley. They must have thought the gates of hell opened on ‘em or something. They had us three-to-one, but our position, armor and gun made it closer to even money. All I remember is Charlie, the TC, his fire commands. ‘Gunner tank 800 meters front AP fire’ then ‘Identified on the way’ and then ‘gunner new target 750m front’ and so on like that. I was in my own little world, y’know? I think we got four or five that day. And I thought to myself, this is it, the perfect tank. 1. LCOL Mark Ishmael Karol Edward Anderson was killed in action in March, 2243 defending Klamath Falls. He was posthumously awarded the Washington Cross with Valor Device for his actions. 2. SSgt. Tony Anglio, CRA (Ret.) served with distinction against both Mormon and Californian forces from the mid-2230s into the 2250s. He retired in 2265 after 24 years of service, primarily in the Armored Force. 3. The M4A1 incorporated an improved engine, revised and upgraded armor packages, and a refined, 55-caliber gun. The M4A2, the “Digital Four” (earning crude nicknames like Fister and Shocker), incorporated a fully electronic fire control computer and a laser rangefinder, new stabilizers, even heavier armor, electro-optical sighting systems, a new gas turbine and transmission, thermal imagers, and a version of the pre-war Watervliet M256 120mm 44-caliber gun. The current M4A3 brings the tank to its fourth gun, the M360A1 120mm 52-caliber smoothbore, it’s third engine, sixth armor package, and incorporates an active protection system and greatly improved laser rangefinder. 4. B Coy, 1/1 Tanks dug in on the ridgeline between old CA route 263 and US I-5 about two miles north of Yreka, CA on the night of March 22, 2240. A Coy. was arrayed to the north, slightly further up I-5, and C Coy. and the Dragoon Battalion of 1st Tanks occupied Yreka itself, with B-1/1 and 2bn of the 4th (Olympia) Infantry Bde. preparing for an assault on Siskiyou County Airport the next morning. Shortly before the jump-off time, the Californian 1st Battalion, 3rd Guards Heavy Tank Regiment, of the elite 8th Guards Shock Air Force Parachute-Tank Division Kamala Harris (An homage to a semi-mythological early 21st century politician revered by the Californians) launched a spoiling attack consisting of eighty two Mark Six heavy tanks and fifty two half-track infantry carriers, supported by significant tube artillery. This represented ten percent of the Californian inventory of Mark Six heavy tanks at the time. In a battle that firmly established the fearsome reputation of both LCol. M.I.K.E. Anderson and the M4 Medium, as well as the extreme ideological indoctrination of the Communist Guards-divisions, B Coy, 1/1 Tanks blunted and stopped the Californian attack, then began a vicious counterattack that included LCol. Anderson’s tank being disabled by infantry attack whilst he lead a headlong pursuit of the retreating enemy, after which he is rumored to have fought off an element of the Communist forces with a pistol and saber. 5. MG Charles M. Dietz, CRA (Ret) was one of three crewman in Barely Legal (M4 S/N 10052, now preserved at the Cascadian Military Museum, Renton) who attained the rank of Major General (including MG McNeil and MG Dana R. Carter, CRA (Ret). The loader, Sergei I. Danilov, reached the rank of Colonel before his death at the hands of Deseret agents during his tenure as commander, 4th Armored Cavalry Bde. He was killed during a running gunbattle in the streets of Pocatello, Idaho Territory, in 2265. His assassination was a great loss, as he was working on writing an operational maneuver doctrine based on pre-war Soviet and American work.
  7. A. T. Mahan

    Competition: Tank Design 2239

    FINAL SUBMISSION 120MM GUN TANK T44 Renton Shipbuilding and Locomotive Works A Pacific Car and Foundry Company The 120mm Gun Tank T44, designed primarily by the Renton Shipbuilding and Locomotive division of Pacific Car and Foundry, is a fully-tracked armored fighting vehicle armed with a 120mm smoothbore gun. Research and exploratory investigation determined that there were a number of designs and concepts with great potential to leverage and improve the combat effect of the vehicle. The most promising hull that PACAR-RSL located was the M47 Patton -- the combination of castings and weldments of high-quality steel was well within the production capabilities of our facility, and the vehicle weight of 90000lbs would be able to be reduced sufficiently to meet the required weight limit. Noting that the vehicle weight specified in the contract (90,000lb) does not specify whether it is the unloaded or loaded weight, the Program Manager determined that it specified the unloaded weight. In any event, PACAR-RSL has several proposed variants (and has produced prototypes of them) that meet varying weight goals. Structure: The original M47’s structure is highly dated. While PACAR-RSL has substantial experience with high-quality castings of the scale required, and while PACAR produced M26 Pershing 90mm gun medium tanks in 1944 and 1945 (and retains sufficient quantities of the technical data package to resume production of mildly improved versions of those tanks if the Government would so desire), castings are not compatible with the composite armor techniques that PACAR and our subcontractors have developed based on combat-proven prewar efforts. As a shipbuilding concern, PACAR-RSL possesses substantial experience producing high-quality weldments of extremely high grade steels, and many of our welders are certified to weld armor steels. This trained and capable workforce allowed our design team to rework the monocoque (armor-as-structure) hull and turret of the M47 to suit both the HAP-1 derived armor package and to lighten the vehicle. This resulted in an allowable armor weight of nearly 10,000lb for the hull, sufficient to utilize the HAP-1 armor on a recontoured lower frontal hull. The hull itself is constructed of welded 1.0” to 1.5” (+/- 0.05”) high strength steel plate, The turret is of a completely new, all-welded design heavily inspired by the pre-war Abrams design, as far as general shape is concerned. Protection: Central to our design is the incorporation of highly advanced composite armors to reduce the threat of shaped-charge warheads. Pre-war literature indicated that these antitank munitions were most concerning for designers of the so-called first and second generation of main battle tanks, due to their light weight and relatively high penetrative ability, and Cascadian control of the only large supplies of depleted uranium and tungsten in the region result in a greatly reduced threat from long-rod fin-stabilized discarding sabot kinetic penetrators. In cooperation with the Pacific Aero Products Company of Seattle, we have spent considerable time and effort developing ceramic and other composite armor technologies, and believe that we have managed to develop an armor package similar in concept to the BRL-1 and HAP-1 armor packages used on various models of early model pre-war M1 Abrams tanks. Our testing has determined that the armor package we have chosen for the vehicle is substantially lighter and more protective than rolled homogeneous steel or cast steel armor, although it is bulkier and substantially more expensive. The armor utilizes combinations of three types of Non-Explosive Reactive Armor (NERA) packages, the Type I array of three thin parallel sandwiches of 5083-H32/elastomer/5083-H32 mounted on large pre-compressed coil springs, the Type II array of layered ceramic/5083-H32/elastomer/5083-H32 sandwich plates mounted at an angle such that an incoming projectile from within 15 degrees of horizontal must penetrate a minimum of four panels, and the Type IIIA/B composite array. We utilize two different composite arrays. The Type IIIA, used on the turret face, consists of a layer of ceramic tiles, a fiberglass-reinforced polymer backer, a layer of elastomer, a layer of depleted uranium, a fiberglass-reinforced polymer backer, a layer of high hardness armor steel, and the hull structure. The Type IIIB, used on the turret sides and lower glacis plate, is the same as that on the turret face, except the depleted uranium is replaced with high hardness steel. This reduces protection against kinetic energy penetrators, but greatly reduces weight, as high hardness steel is 60% lighter than depleted uranium, and the protection is still very good. We have been particularly focused on Carborundum (Silicon Carbide) as the ceramic used in the armor, although experiments have determined that Boron Carbide offers more protection, but is substantially more difficult to manufacture and work with. While large quantities of B4C exist at the Hanford Site in the form of neutron dampers and shielding, and control rods, they would require substantial effort to form into a usable armor material and at this time the yield rate on B4C tiles of the appropriate size is low to the point of total impracticality - at best, we have determined that current technology will produce no more than 5% of a given batch of tiles that meets QA/QC. We have therefore determined that the most weight and efficient armor scheme would be to more-or-less duplicate the HAP-1 armor construction, substituting Silicon Carbide for Boron Carbide where appropriate, and utilizing the supplies of depleted uranium available at the Hanford Site (estimated to be 2,380 tons, appropriate for approximately 750 vehicles based on current projections of 6000lb of DU per vehicle) would provide substantial kinetic protection at the cost of increased weight. Our armor concept, admittedly very heavily inspired by that of the early M1 Abrams designs, provides significant protection for its weight, especially considering the smaller protected volume and reduced level of protection chosen. The turret faces are intended to provide protection equivalent to 20-25 inches of rolled homogeneous steel, but are some 70% lighter. We would note that the Cascadian Government should seek to acquire access to greater supplies of uranium for use in this and other defence programs, and note that research indicates four thousand tons of dry-cask stored spent nuclear fuel each in the former Illinois, former Pennsylvania, and former South Carolina regions and between 3,000 and 4,000 tons each in California, former Alabama, Florida, New York, and Georgia regions. While most of these areas are over a thousand miles away, if Cascadia can secure access to these supplies, they represent approximately 32,500 tons of highly enriched uranium, which would be invaluable for reprocessing into depleted uranium for tank armors, or Special Materials for use in other programs. PACAR-RSL has been making inquiries through traditional trade channels as to the feasibility of cross-country transportation of these materials, but government support would aid the endeavour greatly. It is worth mentioning that this armor design package more-or-less requires the production of a gaseous-diffusion uranium enrichment cascade and the production of weapons-grade uranium. This could be expected to produce 16.9 tons of U-235, enough for over two thousand 25-kiloton nuclear devices. Further protection comes from the incorporation of Contact and Rat, explosive reactive armours derived from the Soviet Kontakt-family tiles. Similar except for size and shape, these require no outside initiation, being a box with two steel plates sandwiching a piece of explosive. Contact is used primarily on the turret face, bow, hull, and turret sides, while Rat, derived from the curved tile of the pre-war US Army M19 ARAT tile, is used only on the hull and turret sides as an up-armor kit. Each Contact tile is 12” wide, 6” tall, and weighs 12.5lb. Each Rat tile weighs approximately 40lb, is 20” tall, 15” wide, and mounted on a hinged bracket that allows them to be angled vertical, or angled about 15 degrees down. This reduces the danger to supporting infantry posed by the tile’s detonation. The 238 Contact and 47 Rat tiles able to be mounted on the vehicle only add a maximum of 4,900lb including mounting hardware while providing greatly increased protection. Contact explosive reactive armor tile (12"x6", 12.5lb) Rat explosive reactive armor tile (15"x20", 40lb) The armor layout is as follows: Turret Turret face: 0.75” HHS face armor, Type I array, Type II array, Type IIIA array, 1” RHA structure 16" RHAe kinetic, 30" RHAe chemical 14 tiles per side of Contact, 28 total Contact tiles provide 14" RHAe against single-stage HEAT threats, ~4" RHAe against full-caliber kinetic threats. Turret side: 0.75” HHS face, Type I array, Type II array, Type IIIB array, 0.75” RHA structure 12" RHAe kinetic, 27" RHAe chemical 11 tiles Contact and 7 RAT tiles per side, 22 Contact and 14 RAT tiles. RAT tiles provide 18" RHAe against single stage HEAT warheads, 20" RHAe against full-caliber kinetic threats, and decrease the efficacy of subcaliber kinetic threats by 15%. This is due to the greater thickness of steel in the tile. Turret rear: 2.25” HHS over 0.75” RHA 3.5" RHAe Turret roof: 1.0” HHS 1.2" RHAe 28 Contact tiles Hull Upper glacis plate: 3” HHS plate sloped at 80 degrees from vertical (17” LOS) 20" RHAe line of sight 44 Contact tiles Lower glacis plate: 0.75” HHS plate, Type I array, Type II array, Type IIIB array, 1” HHS hull 12.5" RHAe kinetic, 27.5" RHAe chemical 5 tiles Rat Hull Side: 2.25” HHS over 0.75” RHA 3.5" RHAe Up-armor side-skirts consisting of a Type I array 5" RHAe kinetic, 11" RHAe chemical 70 tiles Contact per side plus 28 tiles of RAT Hull rear: 2.0” RHA Hull bottom: 0.75” HHS 0.9" RHAe Hull roof: 0.75” HHS 0.9" RHAe Firepower: Other work with the Pacific Aero Products Company focused on the development of improved ammunition designs. PACAR-RSL leveraged PAPC’s advanced aerodynamic analytical techniques to aid in the development of improved fin-stabilized smoothbore ammunition. Research on prewar technologies demonstrated a number of programs conducted by the prewar US Army that incorporated smoothbore guns, and industrial analysis has determined that a maximum chamber-pressure of 55,000psi is within current capabilities, and based on research trends in metallurgy, a chamber pressure of 75,000psi should be achievable within five years, and 100,000psi in ten years. While this will result in a lengthened gun compared to prewar designs (The M256 120mm gun was only a 44-caliber gun), a 50-caliber 120mm gun with a tube weight of not more than 2,900lb and an all-up weight of not more than 4,400lb is entirely viable. We have developed a gun, the 120mm Gun T123E7, that produces a muzzle energy of 4,300 ft-ton with a 50lb armor-piercing capped, ballistic capped projectile (MV = 3,500ft/sec, 50lb shot M358). We estimate that this will drive a 22lb Hanfordite (U-238) penetrator at approximately 4,500ft/sec, giving the capability to defeat greater than 25” of rolled homogenous steel at 2,000 yards, and greatly simplifying the design of the ballistic computer. It uses a vertically sliding breechblock reverse-engineered at great length from surviving examples of the Watervliet Arsenal-produced M256 120mm gun. While the current metallurgy and QA/QC is not sufficient to produce breech blocks capable of the 135,000psi of M256, we believe that with advances in electronically controlled machining, it is feasible. We are planning an exploratory expedition to the Watervleit Arsenal area to gain what prewar technical data we can, particularly on the M256 and M360 guns. Gun, Smoothbore, 120mm T123E7 (120x570R, L/60) T123E7 is a 60-caliber 120-mm smoothbore gun with a vertically sliding breechblock, hydropneumatic recoil mechanism, and chrome-lined bore. It has a fume extractor to reduce the rate of propellant gas ingress into the turret, and a thermal sleeve to stabilize the temperature along the bore and reduce bore irregularities due to thermal expansion. It fires 120x570mm fixed ammunition using a cellulose-fiber combustible cartridge case with a metal base cap, reducing the weight of the cartridge case by some 30lb compared to a brass case (107lb for brass case M358 APC-T vs ~55lb for T494 APFSDS-T). Decreased AP projectile weight due to the usage of armor-piercing fin-stabilized discarding sabot ammunition further reduces the weight of the armor-piercing projectile by nearly half, from 50lb to 26lb. 120mm Ammunition: (L to R) XM441 HEAT-FS (35lb projectile, 3500ft/s MV, M358E1 APC-T (50lb projectile, 3,500ft/s MV), XM442 APFSDS-T (22lb penetrator, 4,400ft/s MV), and a 120mmx575R case Additional projectiles, such as HEP-FS-T and HE-FRAG-FS-T are under development, as are training projectiles. The gun and mount are electrically driven in train and elevation via a geared drive and proportionally controlled motors derived from a mixture of naval fire control equipment and aircraft gun turrets. This had an added benefit of easing the development of an analog two-axis gun stabilization system. The fire control system is electromechanical and analog-electronic, and consists of four components: the T92D gunner’s articulated periscope, the T19 automatic stereoscopic rangefinder, the electrical gun drive, and the T14 gun computer. The gun computer is a miniaturized transistorized electromechanical and analog-electronic computer that incorporates ambient temperature, range as measured from the stereoscopic rangefinder, and the average rate of traverse of the gun over the past one to three seconds to apply lead, cant and Coriolis correction, and superelevation, and align the gun to the sights. When the firing switch is depressed, a set of microswitches delays completion of the firing circuit until the sights are properly aligned, aiding in firing on the move or from a short halt. The gunner’s articulated periscope is a combination 1x-3x variable power unity sight and 3-20x magnified sight, with coated lenses, reticle illumination, and incorporating image intensifying night vision equipment. The image intensifying system is mounted at the end of the optical train, allowing the gunner to use the full magnification range even in reduced lighting conditions. The T19 rangefinder is mounted across the width of the turret and is a 108” base stereoscopic rangefinder equipped with an electro-optical automatic ranging mechanism. Using the following equations, from Material Testing Procedure 3-2-702 (US Army Test and Evaluation Command, Common Engineering Test Procedure for Optical Rangefinders, 20 Apr. 1966, Aberdeen, Maryland), we calculate the T19 rangefinder has a mechanical accuracy of [x] meters. For a base length B of 2.769m, a range R1 of 2,000m [math goes here] The rangefinder can be used by the commander in the manual mode to either produce a more accurate ranging solution and in the event of automatic ranging mechanism failure. Both the commander and gunner can use the rangefinder, although as the fire control system is designed around and as-yet unproduced laser rangefinder, the primary control of automatic rangefinding is on the gunner's controls. The T14 gun computer can also accept manual input of range information via a dial, in 100-yard increments. The automatic mechanism is derived from Leika’s work in camera autofocus mechanisms, and is based on a small array of lead (II) sulfide photosensors similar to those used in early-model AIM-9 Sidewinder air-to-air missiles and a very simple electrical circuit. Early testing has determined that it can resolve ranges with a similar accuracy as a human operator in ⅓-½ the time, depending on the skill of the human operator. The turret and rangefinding system is also designed for-but-not-with a laser rangefinder, which would replace the optical rangefinder and improve gun depression from 12 degrees to 14 degrees. A laser rangefinder similar to the prewar AN/VVG-2 (Ruby, 694.3nm, 50mJ pulse, 125J maximum output) as used in the M60A3 would reduce the ranging time to 1.5 seconds and reduce the typical ranging error from several hundred yards to tens of yards. The ranging time is currently the largest component of the firing sequence, as the design of the T14 gun computer requires it to constantly update the firing solution for all inputs except range and lead, and lead correction is applied more-or-less instantaneously upon depression of the gunner's automatic ranging switch. The T123E7 120mm smoothbore gun is provided with 56 rounds of ammunition in a blow-out protected bustle rack and twenty-four rounds in supplementary ammunition racks to either side of the loader, a total of 80 rounds. There is a 7.62mm M240 machine gun mounted coaxially to the main gun, with 8,000 rounds of 7.62x51mm (2,000 ready). There is a 7.62mm M240 machine gun provided for the loader mounted in a race-ring mount around his hatch with 2,000 rounds of 7.62x51mm (200 ready) There is a .50 M2 machine gun provided for the commander on a ring mount around the commander’s cupola with 2,000 rounds of .50 ammunition (100 ready) Provision is made for the storage of the crew’s individual weapons and field equipment, including four rifles and ammunition. Mobility: T44 uses a torsion-bar suspension, with six individually sprung road-wheels per track connected to double-acting bar-in-tube springs providing substantially improved suspension travel to the original single-acting suspension. There are two powertrains currently proposed. The first, a prewar design Continental AVDS-1790-5B is a known quantity, an extremely reliable and widely used turbosupercharged diesel V-12 producing 810 horsepower at 2,400RPM. This, in combination with the CD-875-2 four-speed automatic transmission produces a maximum speed of 35 miles an hour on road, and the improved double-acting torsion bar suspension provides an increased rough-terrain speed of approximately 12 miles per hour, compared to nine miles an hour for the Medium Tank M4. This gives the vehicle a combat range of approximately 430 miles with 310 gallons of Diesel fuel. The second powertrain is derived from prewar work on gas turbines. It is a simple, reliable gas turbine of 65” length and 25” diameter that, due to manufacturing limitations, only produces about 1,000 horsepower. Similar prewar designs produced approximately 1,500 horsepower in ground use and 1,800 horsepower in aviation use, but due to manufacturing limitations and for safety reasons, the turbine is limited to 1,200hp SHP emergency power for ten minutes, and 1,000 horsepower maximum. This drives a CD-1100-4F2 crossdrive automatic six-speed transmission (four forward, two reverse), resulting in a maximum road speed of 48 miles per hour and a rough-terrain speed of 22 miles per hour, although crew comfort is a significant concern and shock absorption is an issue at such speeds. This engine, with the associated APU, gives the vehicle a combat range of approximately 375 miles, although with greater speed than the AVDS-1790. The strategic mobility of the T44 tank is provided by the vehicle’s high speed and substantial reliability. Rail transport of the T44 requires removing the side-skirts and side explosive reactive armor tiles, requiring one hour per vehicle plus a wrecker capable of lifting 1,300lb. Alternatively, the vehicle can be road-marched in combat condition. In summary, the T44 medium tank meets all of the required design specifications: It is 90,000lb unloaded, and 128,000lb at combat weight. The fenders fold up to ensure a 129” maximum width (otherwise 135” width) The upper frontal plate is 3” thick sloped at 80 degrees from vertical, giving an effective line of sight thickness of 17” The side armor is 3” thick The power to weight ratio is at worst 16hp/ton (loaded, 810hp engine) and at best 19.6hp/ton The tank has a crew of four: Driver, TC, gunner, and commander. The primary armament, 120mm gun T123E7, is capable of firing both antiarmor and high explosive projectiles. 9ft 8” tall 120mm Gun Tank T44 specifications: Empty weight: 94,000lb Operating empty weight: 109,250lb Combat weight: 128,000lb Height: 116" Width: 168.639 inches Length: 233.5" (hull), 415.5" overall, gun forward. Ground clearance: 21" at combat weight, less at OEW. Engine: Pseudo-Lycoming T53, 750lb/1,000shp APU: Two-stroke 25 horsepower Yamaha outboard powerhead Transmission: CD-1100-4F2. Four speeds forward, two reverse. Automatic crossdrive transmission. Engine and transmission are a powerpack. Track: Modified T158 track, cut down to 23" wide. Suspension: 74" long bar-in-tube double acting torsion bars, friction snubbers on the first two and last two pairs of road wheels each side (duals on the first road wheel), shock absorbers on the first, second, fifth, and sixth road wheels each side. Three return rollers each side. A total of 16" of compression and 8" of rebound at combat weight results in 24" of total suspension travel. Fuel capacity: 325 gallons Range: ~150-200 miles Armor weight budget: Weight budget
  8. A. T. Mahan

    Competition: Tank Design 2239

    FINAL SUBMISSION: LIGHT TANK 57mm Gun Full Tracked Light Tank M48A4E4 “Koskiusko” NorthStar Tractor, a subsidiary of Pacific Car and Foundry Description: The M48A4E4 is a lightweight, fully tracked, Petrol-powered armored reconnaissance vehicle. It can operate on or off road at high speed over rough terrain in reconnaissance, pursuit, flanking, harassing, target acquisition, deep raiding, air-mobile and other combat roles. It is also air-transportable. Armament consists of a 57mm automatic cannon T33 mounted in a 360 degree rotating turret, capable of firing APHEBC, HVAP, APDS, HE, CAN, and APFSDS rounds; one 106mm Recoilless Rifle M40 mounted in an elevation adjustable mount on the left turret exterior, capable of firing HEAT, HE, APERS, and HEP shells; a caliber .50 Browning mounted on the commander’s hatch for air defense; and a battery of 8 smoke dischargers, mounted turret rear firing forwards over the turret. When directed to develop a light tank according to the Cascadian RFP, NorthStar Tractor decided to use the same tried and true design philosophy which has borne success in the agricultural sector. Where novel gadgetry may amaze and provide incredible paper performance for other submissions, NorthStar Tractor has taken a less foolhardy approach. Wherever possible proven designs, techniques and technologies are applied, often in novel ways or combinations, to achieve the requirements set forth. This is not to imply luddite tendencies. Novel technology is used when it is the best solution, as judged against the teething problems and expense it would incur. The end product is a vehicle which enters service without the teething problems associated with a more novelty focused approach. NST selected the Pre-War Buick 76mm Gun Motor Carriage M18 “Hellcat” as a starting point. Its combination of light weight, high speed, and excellent war record, as well as being significantly under the weight and size requirements, gave the Firm’s engineers the safety margin necessary to freely experiment with design possibilities. Chassis: From the core M18 “Hellcat” chassis has come the general configuration and design of the hull. Some modification has been made, however. The vehicle was experimentally equipped with various engines. These variants are known as the M48, M48A1, M48A2, M48A3, and M48A4 respectively. Designation Engine M48 R975 M48A1 Diesel M48A2 Gas Turbine M48A3 Hybrid-Electric faildrive M48A4 Ford GAA On all variants the Assistant Driver’s position has been wholly deleted and replaced by a Self-Sealing fuel tank, which yields an additional 190 liters of petrol. The suspension and tracks remain the same as on the original M18 GMC, save the torsion bars are of the double acting tube-in-bar design, rather than single. It is the design team’s feeling that armor on a light tank is generally of little and less value. Given the stated threat profile listed in the RFP, and the doctrinal role of the light tank, the M48 has been designed with speed and situational awareness as it’s armor. The steel and aluminum construction of the M48 allows it to withstand small arms fire and shell splinters. To attain a meaningful level of protection against the threats profiled would compromise the mobility which forms the core of the M48. That said, developments in Explosive Reactive Armor (ERA) are being watched very closely, and pending the success of the PACAR-RSL “Contact” system in trials, it will be investigated as a potential way to mitigate the threat of light anti-tank weapons. The production M48A4 will be fitted for but not with the “Contact” armor system. As suits a light tank, the ammunition load and stores capacity should enable the crew to operate independent of resupply for some days. For this purpose the M48 is equipped with Kettle, Electric, Hot Water, M32 with Percolator, Coffee, M30, able to prepare hot beverages and reheat rations. Firepower: Developed from a fusion of pre-war Soviet and British designs, the 57mm Automatic Gun T33 provides ample anti-armor firepower for the scout role. Upgrades to the T33 gun are underway, utilizing technologies developed for the T44 program to develop both APDS and APFSDS shells for greater penetration. The peculiarities of the magazine system preclude quickly changing the ammunition type, and the 57mm O-271U HE shell was historically lackluster. To offset this, and provide additional close-medium range firepower, M40 106mm Recoilless Rifles are mounted in an elevation adjustable mount on the left side of the turret. For local air defense a Caliber .50 is mounted on a ring above the commander’s hatch. Optional armor kits are in development for this position. The turret of the M18 was deemed insufficient and removed. While it possessed admirable characteristics, it was not designed around the role intended for the M48. That said, the vehicle is backwards compatible, and the M18’s gun and turret can be produced and mounted should the customer desire. The M48 is equipped with the T36 Turret, either the T36E1, armed with the T32E3 gun, or the T36E2, armed with the T33 gun. The T32E3 consists of the 57mm/L50 Anti-Tank Gun M1 design in 57x440mm caliber, mated to the Molins Mk.III Automatic Loader. The T33 is a 57mm/L70 barrel chambered in 57x480mm mated to a modified version of the Molins design. A cyclic rate of fire of 50-60 rounds/minute is possible, with a 24 round fixed magazine. Additional ammunition is carried in the hull. Mounted on the left side of the turret is either the T63 weapons system consisting of two mated 106mm M40 recoilless rifles and a M8C Caliber .50BAT spotting rifle or T64 weapons system consisting of a single rifle and spotting rifle. The main ammunition for these weapons will be the M581 APERS round with 9.89kg of flechettes, the M344A1 HEAT-FS shell with >400mm of RHA penetration and an effective range of approximately 1300m, or the M346A1 HEP-T shell with a 3.5kg burst charge. Armament Variants T32E3 (L50) T33 (L70) T63 (2x106) M48A4E1 M48A4E2 T64 (1x106) M48A4E3 M48A4E4 All variants can mount a Caliber .50 machinegun on the roof pintle. The gunner is equipped with a primary 6x periscopic gunsight, along with a unity panoramic. Rangefinding is stadiometric, with both a 1,5 and 2,7m stadia. The commander is equipped with a traversing binocular periscopic 1.2-4x sight. This unit has two push-button controls, one to stabilize the periscope in azimuth independent of the turret, and one to slew the turret to the commanders sight azimuth. This provides a moderate hunter-killer capacity. The turret bustle contains the radio equipment. A command/FAC/FIST-V design with improved radios is in development as well. Training of the turret is accomplished by an electric system, allowing traverse of up to 30 degrees/s. Elevation is also electric, from -10/+20 degrees. The gun is stabilized in traverse and elevation using a system derived from the RSLW T44 project. Additional stowage is provided for personal weapons and equipment, pioneer tools, camouflage netting, and miscellaneous items. Armor: The M48 is, practically speaking, armored solely against small arms and artillery fragments. It meets the required specifications of the RFP in terms of armor. Upgrade packages are available, mounting “Contact” or “RAT” Explosive-Reactive-Armor tiles or composite armor packages, however these significantly increase the weight of the vehicle, and compromise its excellent mobility. In house testing at NorthStar Tractor determined that the best combination of reliability, cost, and battle-effectiveness was the M48A4 with engine based on the Pre-War Ford GAA V-8, and generally unmodified transmission. The program manager selected the E2 armament subsystem for proposal. The M48A4E2 meets the specifications of the RFP: The combat weight of 19,000 kg is 6 tons below specification (17% underweight) The width, c. 113”, is under the c.130” limit The upper glacis and frontal turret armor are 1” thick, not including add-on packages The 12.7mm side armor is 2.7mm above specification The power:weight ratio (500hp : 19,000kg) of 23.87 hp/t is approximately 198% of the Power:Weight requirement The 3 man crew is 50% of the requirement The primary armament, 57mm Automatic Gun T33, can fire both HE and AP shot and shell, while the 106mm M40 can fire HEAT, HEP, HE, and APERS. 57mm Gun Full Tracked Light Tank M48A4E2 GENERAL CHARACTERISTICS Crew: 3 (Driver, Gunner, Commander) Length: 6.6m (gun forward), 5.28m (hull) Width: 2.87m Height: 2.6 m Ground Clearance: 0.36m Turret Ring Diameter (inside): 69 in Weight, nominal empty: 18,000 kg Weight, full load: 19,000 kg Power to Weight Ratio (gross): 21 hp/t at 19,000kg Ground Pressure: .885kg/cm^2 empty weight (zero ground penetration) PROTECTION Hull armor: Upper glacis - 12.7mm steel + 12.7mm Aluminum Lower glacis - 12.7mm steel Side / Rear - 12.7mm steel Turret armor: Front Face 25.4mm steel Sides and Rear 12.7mm steel ARMAMENT Primary: 57x480mm L/70 Automatic Gun T33 Traverse: Electric, 360 degrees Traverse Rate (max): 30 d/s, 12 seconds/360 degrees Elevation: Electric with manual backup, +20/-10 degrees Elevation Rate: 15 d/s Firing Rate (cyclic): 55 rounds/min Stabilizer: Vertical and Horizontal Secondary: (2x) 106mm M40 Recoilless Rifle, Slaved to gun, mounted on turret side. (1x) .50 caliber M2 machine gun, Ring mount for commander Provision for (3) Cascadian Republic Submachine Gun, Cal. 9x19mm, M56 or equivalent AMMUNITION 72 rounds 57x480mmR (APHE, APCBC, HVAP, APCR, HE-FRAG, CANN, APFSDS-T) 6 rounds 105x607mmR [106mm Recoilless] (HEAT, HE-P, HE, APERS) 800 rounds 12.7x99mm Optics Gunner's 6x Primary Telescopic Sight Gunner's 1-4x Auxiliary Periscopic Unity Sight Built in Stadiametric Rangefinder Commander 1.2-4x Periscopic stabilized sight Vision Devices: Driver: Periscopes (3), Provision for I2 or IR NV systems Commander: Binoculars Gunner: Gunner's Primary Sight, Gunner's Auxiliary Sight POWERPLANT Ford GAA, 500hp @2600RPM
  9. A. T. Mahan

    Competition: Tank Design 2239

    I'd like until midnight EST to get the final submission posts done for my two.
  10. A. T. Mahan

    Competition: Tank Design 2239

    120MM GUN TANK T44 Renton Shipbuilding and Locomotive Works A Pacific Car and Foundry Company The 120mm Gun Tank T44, designed primarily by the Renton Shipbuilding and Locomotive division of Pacific Car and Foundry, is a fully-tracked armored fighting vehicle armed with a 120mm smoothbore gun. Research and exploratory investigation determined that there were a number of designs and concepts with great potential to leverage and improve the combat effect of the vehicle. The most promising hull that PACAR-RSL located was the M47 Patton -- the combination of castings and weldments of high-quality steel was well within the production capabilities of our facility, and the vehicle weight of 90000lbs would be able to be reduced sufficiently to meet the required weight limit. Noting that the vehicle weight specified in the contract (90,000lb) does not specify whether it is the unloaded or loaded weight, the Program Manager determined that it specified the unloaded weight. In any event, PACAR-RSL has several proposed variants (and has produced prototypes of them) that meet varying weight goals. Structure: The original M47’s structure is highly dated. While PACAR-RSL has substantial experience with high-quality castings of the scale required, and while PACAR produced M26 Pershing 90mm gun medium tanks in 1944 and 1945 (and retains sufficient quantities of the technical data package to resume production of mildly improved versions of those tanks if the Government would so desire), castings are not compatible with the composite armor techniques that PACAR and our subcontractors have developed based on combat-proven prewar efforts. As a shipbuilding concern, PACAR-RSL possesses substantial experience producing high-quality weldments of extremely high grade steels, and many of our welders are certified to weld armor steels. This trained and capable workforce allowed our design team to rework the monocoque (armor-as-structure) hull and turret of the M47 to suit both the HAP-1 derived armor package and to lighten the vehicle. This resulted in an allowable armor weight of nearly 10,000lb for the hull, sufficient to utilize the HAP-1 armor on a recontoured lower frontal hull. The hull itself is constructed of welded 1.0” to 1.5” (+/- 0.05”) high strength steel plate, The turret is of a completely new, all-welded design heavily inspired by the pre-war Abrams design, as far as general shape is concerned. Protection: Central to our design is the incorporation of highly advanced composite armors to reduce the threat of shaped-charge warheads. Pre-war literature indicated that these antitank munitions were most concerning for designers of the so-called first and second generation of main battle tanks, due to their light weight and relatively high penetrative ability, and Cascadian control of the only large supplies of depleted uranium and tungsten in the region result in a greatly reduced threat from long-rod fin-stabilized discarding sabot kinetic penetrators. In cooperation with the Pacific Aero Products Company of Seattle, we have spent considerable time and effort developing ceramic and other composite armor technologies, and believe that we have managed to develop an armor package similar in concept to the BRL-1 and HAP-1 armor packages used on various models of early model pre-war M1 Abrams tanks. Our testing has determined that the armor package we have chosen for the vehicle is substantially lighter and more protective than rolled homogeneous steel or cast steel armor, although it is bulkier and substantially more expensive. The armor utilizes combinations of three types of Non-Explosive Reactive Armor (NERA) packages, the Type I array of three thin parallel sandwiches of 5083-H32/elastomer/5083-H32 mounted on large pre-compressed coil springs, the Type II array of layered ceramic/5083-H32/elastomer/5083-H32 sandwich plates mounted at an angle such that an incoming projectile from within 15 degrees of horizontal must penetrate a minimum of four panels, and the Type IIIA/B composite array. We utilize two different composite arrays. The Type IIIA, used on the turret face, consists of a layer of ceramic tiles, a fiberglass-reinforced polymer backer, a layer of elastomer, a layer of depleted uranium, a fiberglass-reinforced polymer backer, a layer of high hardness armor steel, and the hull structure. The Type IIIB, used on the turret sides and lower glacis plate, is the same as that on the turret face, except the depleted uranium is replaced with high hardness steel. This reduces protection against kinetic energy penetrators, but greatly reduces weight, as high hardness steel is 60% lighter than depleted uranium, and the protection is still very good. We have been particularly focused on Carborundum (Silicon Carbide) as the ceramic used in the armor, although experiments have determined that Boron Carbide offers more protection, but is substantially more difficult to manufacture and work with. While large quantities of B4C exist at the Hanford Site in the form of neutron dampers and shielding, and control rods, they would require substantial effort to form into a usable armor material and at this time the yield rate on B4C tiles of the appropriate size is low to the point of total impracticality - at best, we have determined that current technology will produce no more than 5% of a given batch of tiles that meets QA/QC. We have therefore determined that the most weight and efficient armor scheme would be to more-or-less duplicate the HAP-1 armor construction, substituting Silicon Carbide for Boron Carbide where appropriate, and utilizing the supplies of depleted uranium available at the Hanford Site (estimated to be 2,380 tons, appropriate for approximately 750 vehicles based on current projections of 6000lb of DU per vehicle) would provide substantial kinetic protection at the cost of increased weight. Our armor concept, admittedly very heavily inspired by that of the early M1 Abrams designs, provides significant protection for its weight, especially considering the smaller protected volume and reduced level of protection chosen. The turret faces are intended to provide protection equivalent to 20-25 inches of rolled homogeneous steel, but are some 70% lighter. We would note that the Cascadian Government should seek to acquire access to greater supplies of uranium for use in this and other defence programs, and note that research indicates four thousand tons of dry-cask stored spent nuclear fuel each in the former Illinois, former Pennsylvania, and former South Carolina regions and between 3,000 and 4,000 tons each in California, former Alabama, Florida, New York, and Georgia regions. While most of these areas are over a thousand miles away, if Cascadia can secure access to these supplies, they represent approximately 32,500 tons of highly enriched uranium, which would be invaluable for reprocessing into depleted uranium for tank armors, or Special Materials for use in other programs. PACAR-RSL has been making inquiries through traditional trade channels as to the feasibility of cross-country transportation of these materials, but government support would aid the endeavour greatly. It is worth mentioning that this armor design package more-or-less requires the production of a gaseous-diffusion uranium enrichment cascade and the production of weapons-grade uranium. This could be expected to produce 16.9 tons of U-235, enough for over two thousand 25-kiloton nuclear devices. Further protection comes from the incorporation of Contact and Rat, explosive reactive armours derived from the Soviet Kontakt-family tiles. Similar except for size and shape, these require no outside initiation, being a box with two steel plates sandwiching a piece of explosive. Contact is used primarily on the turret face, bow, hull, and turret sides, while Rat, derived from the curved tile of the pre-war US Army M19 ARAT tile, is used only on the hull and turret sides as an up-armor kit. Each Contact tile is 12” wide, 6” tall, and weighs 12.5lb. Each Rat tile weighs approximately 40lb, is 20” tall, 15” wide, and mounted on a hinged bracket that allows them to be angled vertical, or angled about 15 degrees down. This reduces the danger to supporting infantry posed by the tile’s detonation. The 238 Contact and 47 Rat tiles able to be mounted on the vehicle only add a maximum of 4,900lb including mounting hardware while providing greatly increased protection. Contact explosive reactive armor tile (12"x6", 12.5lb) Rat explosive reactive armor tile (15"x20", 40lb) The armor layout is as follows: Turret Turret face: 0.75” HHS face armor, Type I array, Type II array, Type IIIA array, 1” RHA structure 16" RHAe kinetic, 30" RHAe chemical 14 tiles per side of Contact, 28 total Contact tiles provide 14" RHAe against single-stage HEAT threats, ~4" RHAe against full-caliber kinetic threats. Turret side: 0.75” HHS face, Type I array, Type II array, Type IIIB array, 0.75” RHA structure 12" RHAe kinetic, 27" RHAe chemical 11 tiles Contact and 7 RAT tiles per side, 22 Contact and 14 RAT tiles. RAT tiles provide 18" RHAe against single stage HEAT warheads, 20" RHAe against full-caliber kinetic threats, and decrease the efficacy of subcaliber kinetic threats by 15%. This is due to the greater thickness of steel in the tile. Turret rear: 2.25” HHS over 0.75” RHA 3.5" RHAe Turret roof: 1.0” HHS 1.2" RHAe 28 Contact tiles Hull Upper glacis plate: 3” HHS plate sloped at 80 degrees from vertical (17” LOS) 20" RHAe line of sight 44 Contact tiles Lower glacis plate: 0.75” HHS plate, Type I array, Type II array, Type IIIB array, 1” HHS hull 12.5" RHAe kinetic, 27.5" RHAe chemical 5 tiles Rat Hull Side: 2.25” HHS over 0.75” RHA 3.5" RHAe Up-armor side-skirts consisting of a Type I array 5" RHAe kinetic, 11" RHAe chemical 70 tiles Contact per side plus 28 tiles of RAT Hull rear: 2.0” RHA Hull bottom: 0.75” HHS 0.9" RHAe Hull roof: 0.75” HHS 0.9" RHAe Firepower: Other work with the Pacific Aero Products Company focused on the development of improved ammunition designs. PACAR-RSL leveraged PAPC’s advanced aerodynamic analytical techniques to aid in the development of improved fin-stabilized smoothbore ammunition. Research on prewar technologies demonstrated a number of programs conducted by the prewar US Army that incorporated smoothbore guns, and industrial analysis has determined that a maximum chamber-pressure of 55,000psi is within current capabilities, and based on research trends in metallurgy, a chamber pressure of 75,000psi should be achievable within five years, and 100,000psi in ten years. While this will result in a lengthened gun compared to prewar designs (The M256 120mm gun was only a 44-caliber gun), a 50-caliber 120mm gun with a tube weight of not more than 2,900lb and an all-up weight of not more than 4,400lb is entirely viable. We have developed a gun, the 120mm Gun T123E7, that produces a muzzle energy of 4,300 ft-ton with a 50lb armor-piercing capped, ballistic capped projectile (MV = 3,500ft/sec, 50lb shot M358). We estimate that this will drive a 22lb Hanfordite (U-238) penetrator at approximately 4,500ft/sec, giving the capability to defeat greater than 25” of rolled homogenous steel at 2,000 yards, and greatly simplifying the design of the ballistic computer. It uses a vertically sliding breechblock reverse-engineered at great length from surviving examples of the Watervliet Arsenal-produced M256 120mm gun. While the current metallurgy and QA/QC is not sufficient to produce breech blocks capable of the 135,000psi of M256, we believe that with advances in electronically controlled machining, it is feasible. We are planning an exploratory expedition to the Watervleit Arsenal area to gain what prewar technical data we can, particularly on the M256 and M360 guns. Gun, Smoothbore, 120mm T123E7 (120x570R, L/60) T123E7 is a 60-caliber 120-mm smoothbore gun with a vertically sliding breechblock, hydropneumatic recoil mechanism, and chrome-lined bore. It has a fume extractor to reduce the rate of propellant gas ingress into the turret, and a thermal sleeve to stabilize the temperature along the bore and reduce bore irregularities due to thermal expansion. It fires 120x570mm fixed ammunition using a cellulose-fiber combustible cartridge case with a metal base cap, reducing the weight of the cartridge case by some 30lb compared to a brass case (107lb for brass case M358 APC-T vs ~55lb for T494 APFSDS-T). Decreased AP projectile weight due to the usage of armor-piercing fin-stabilized discarding sabot ammunition further reduces the weight of the armor-piercing projectile by nearly half, from 50lb to 26lb. 120mm XM442 Armor-Piercing Fin-Stabilized Discarding Sabot, Tracer (22lb Oralloy penetrator, 4,400ft/s MV) Additional projectiles, such as HEP-FS-T, HE-FRAG-FS-T and HEAT-FS-T are under development, as are training projectiles. 120mm M358E1 APCBC-FS-T (50lb projectile, 3,500ft/s MV) The gun and mount are electrically driven in train and elevation via a geared drive and proportionally controlled motors derived from a mixture of naval fire control equipment and aircraft gun turrets. This had an added benefit of easing the development of an analog two-axis gun stabilization system. The fire control system is electromechanical and analog-electronic, and consists of four components: the T92D gunner’s articulated periscope, the T19 automatic stereoscopic rangefinder, the electrical gun drive, and the T14 gun computer. The gun computer is a miniaturized transistorized electromechanical and analog-electronic computer that incorporates ambient temperature, range as measured from the stereoscopic rangefinder, and the average rate of traverse of the gun over the past one to three seconds to apply lead, cant and Coriolis correction, and superelevation, and align the gun to the sights. When the firing switch is depressed, a set of microswitches delays completion of the firing circuit until the sights are properly aligned, aiding in firing on the move or from a short halt. The gunner’s articulated periscope is a combination 1x-3x variable power unity sight and 3-20x magnified sight, with coated lenses, reticle illumination, and incorporating image intensifying night vision equipment. The image intensifying system is mounted at the end of the optical train, allowing the gunner to use the full magnification range even in reduced lighting conditions. The T19 rangefinder is mounted across the width of the turret and is a 108” base stereoscopic rangefinder equipped with an electro-optical automatic ranging mechanism. Using the following equations, from Material Testing Procedure 3-2-702 (US Army Test and Evaluation Command, Common Engineering Test Procedure for Optical Rangefinders, 20 Apr. 1966, Aberdeen, Maryland), we calculate the T19 rangefinder has a mechanical accuracy of [x] meters. For a base length B of 2.769m, a range R1 of 2,000m [math goes here] The rangefinder can be used by the commander in the manual mode to either produce a more accurate ranging solution and in the event of automatic ranging mechanism failure. Both the commander and gunner can use the rangefinder, although as the fire control system is designed around and as-yet unproduced laser rangefinder, the primary control of automatic rangefinding is on the gunner's controls. The T14 gun computer can also accept manual input of range information via a dial, in 100-yard increments. The automatic mechanism is derived from Leika’s work in camera autofocus mechanisms, and is based on a small array of lead (II) sulfide photosensors similar to those used in early-model AIM-9 Sidewinder air-to-air missiles and a very simple electrical circuit. Early testing has determined that it can resolve ranges with a similar accuracy as a human operator in ⅓-½ the time, depending on the skill of the human operator. The turret and rangefinding system is also designed for-but-not-with a laser rangefinder, which would replace the optical rangefinder and improve gun depression from 12 degrees to 14 degrees. A laser rangefinder similar to the prewar AN/VVG-2 (Ruby, 694.3nm, 50mJ pulse, 125J maximum output) as used in the M60A3 would reduce the ranging time to 1.5 seconds and reduce the typical ranging error from several hundred yards to tens of yards. The ranging time is currently the largest component of the firing sequence, as the design of the T14 gun computer requires it to constantly update the firing solution for all inputs except range and lead, and lead correction is applied more-or-less instantaneously upon depression of the gunner's automatic ranging switch. The T123E7 120mm smoothbore gun is provided with 56 rounds of ammunition in a blow-out protected bustle rack and twenty-four rounds in supplementary ammunition racks to either side of the loader, a total of 80 rounds. There is a 7.62mm M240 machine gun mounted coaxially to the main gun, with 8,000 rounds of 7.62x51mm (2,000 ready). There is a 7.62mm M240 machine gun provided for the loader mounted in a race-ring mount around his hatch with 2,000 rounds of 7.62x51mm (200 ready) There is a .50 M2 machine gun provided for the commander on a ring mount around the commander’s cupola with 2,000 rounds of .50 ammunition (100 ready) Provision is made for the storage of the crew’s individual weapons and field equipment, including four 5.56mm rifles and ammunition. Mobility: T44 uses a torsion-bar suspension, with six individually sprung road-wheels per track connected to double-acting bar-in-tube springs providing substantially improved suspension travel to the original single-acting suspension. There are two powertrains currently proposed. The first, a prewar design Continental AVDS-1790-5B is a known quantity, an extremely reliable and widely used turbosupercharged diesel V-12 producing 810 horsepower at 2,400RPM. This, in combination with the CD-875-2 four-speed automatic transmission produces a maximum speed of 35 miles an hour on road, and the improved double-acting torsion bar suspension provides an increased rough-terrain speed of approximately 12 miles per hour, compared to nine miles an hour for the Medium Tank M4. This gives the vehicle a combat range of approximately 430 miles with 310 gallons of Diesel fuel. The second powertrain is derived from prewar work on gas turbines. It is a simple, reliable gas turbine of 65” length and 25” diameter that, due to manufacturing limitations, only produces about 1,000 horsepower. Similar prewar designs produced approximately 1,500 horsepower in ground use and 1,800 horsepower in aviation use, but due to manufacturing limitations and for safety reasons, the turbine is limited to 1,200hp SHP emergency power for ten minutes, and 1,000 horsepower maximum. This drives a CD-1100-4F2 crossdrive automatic six-speed transmission (four forward, two reverse), resulting in a maximum road speed of 48 miles per hour and a rough-terrain speed of 22 miles per hour, although crew comfort is a significant concern and shock absorption is an issue at such speeds. This engine, with the associated APU, gives the vehicle a combat range of approximately 375 miles, although with greater speed than the AVDS-1790. The strategic mobility of the T44 tank is provided by the vehicle’s high speed and substantial reliability. Rail transport of the T44 requires removing the side-skirts and side explosive reactive armor tiles, requiring one hour per vehicle plus a wrecker capable of lifting 1,300lb. Alternatively, the vehicle can be road-marched in combat condition. In summary, the T44 medium tank meets all of the required design specifications: It is 90,000lb unloaded, and 128,000lb at combat weight. The fenders fold up to ensure a 129” maximum width (otherwise 135” width) The upper frontal plate is 3” thick sloped at 80 degrees from vertical, giving an effective line of sight thickness of 17” The side armor is 3” thick The power to weight ratio is at worst 16hp/ton (loaded, 810hp engine) and at best 19.6hp/ton The tank has a crew of four: Driver, TC, gunner, and commander. The primary armament, 120mm gun T123E7, is capable of firing both antiarmor and high explosive projectiles. 9ft 8” tall 120mm Gun Tank T44 specifications: Empty weight: 94,000lb Operating empty weight: 109,250lb Combat weight: 128,000lb Height: 116" Width: 168.639 inches Length: 233.5" (hull), 415.5" overall, gun forward. Ground clearance: 21" at combat weight, less at OEW. Engine: Pseudo-Lycoming T53, 750lb/1,000shp APU: Two-stroke 25 horsepower Yamaha outboard powerhead Transmission: CD-1100-4F2. Four speeds forward, two reverse. Automatic crossdrive transmission. Engine and transmission are a powerpack. Track: Modified T158 track, cut down to 23" wide. Suspension: 74" long bar-in-tube double acting torsion bars, friction snubbers on the first two and last two pairs of road wheels each side (duals on the first road wheel), shock absorbers on the first, second, fifth, and sixth road wheels each side. Three return rollers each side. A total of 16" of compression and 8" of rebound at combat weight results in 24" of total suspension travel. Fuel capacity: 325 gallons Range: ~150-200 miles Armor weight budget: Weight budget
  11. A. T. Mahan

    Competition: Tank Design 2239

    @Sturgeon having it due Wednesday would be great!
  12. A. T. Mahan

    Competition: Tank Design 2239

    Hey! I'm working on a medium tank design right now -- I might have to hand draft it rather than doing it up in NX since I can't find a good model to work off of and I'm not going to try to design a tank in NX from scratch with my courseload right now, but it's going to be good. Here's a very rough draft, lacking graphics because I'm going to make those tomorrow: The 120mm Gun Tank T44, designed primarily by the Renton Shipbuilding and Locomotive division of Pacific Car and Foundry, is a fully-tracked armored fighting vehicle armed with a 120mm smoothbore gun. Research and exploratory investigation determined that there were a number of designs and concepts with great potential to leverage and improve the combat effect of the vehicle. The most promising hull that PACAR-RSL located was the M47 Patton -- the combination of castings and weldments of high-quality steel was well within the production capabilities of our facility, and the vehicle weight of 93000lbs would be able to be reduced sufficiently to meet the required weight limit. Noting that the vehicle weight specified in the contract (90,000lb) does not specify whether it is the unloaded or loaded weight, the Program Manager determined that it specified the unloaded weight. In any event, PACAR-RSL has several proposed variants (and has produced prototypes of them) that meet varying weight goals. Structure: The original M47’s structure is highly dated. While PACAR-RSL has substantial experience with high-quality castings of the scale required, and while PACAR produced M26 Pershing 90mm gun medium tanks in 1944 and 1945 (and retains sufficient quantities of the technical data package to resume production of mildly improved versions of those tanks if the Government would so desire), castings are not compatible with the composite armor techniques that PACAR and our subcontractors have developed based on combat-proven prewar efforts. As a shipbuilding concern, PACAR-RSL possesses substantial experience producing high-quality weldments of extremely high grade steels, and many of our welders are certified to weld armor steels. This trained and capable workforce allowed our design team to rework the monocoque (armor-as-structure) hull and turret of the M47 to suit both the HAP-1 derived armor package and to lighten the vehicle. This resulted in an allowable armor weight of nearly 10,000lb for the hull, sufficient to utilize the HAP-1 armor on a recontoured lower frontal hull. The hull itself is constructed of welded 1.0” to 1.5” (+/- 0.05”) high strength steel plate, The turret is of a completely new, all-welded design heavily inspired by the pre-war Abrams design, as far as general shape is concerned. Protection: Central to our design is the incorporation of highly advanced composite armors to reduce the threat of shaped-charge warheads. Pre-war literature indicated that these antitank munitions were most concerning for designers of the so-called first and second generation of main battle tanks, due to their light weight and relatively high penetrative ability, and Cascadian control of the only large supplies of depleted uranium and tungsten in the region result in a greatly reduced threat from long-rod fin-stabilized discarding sabot kinetic penetrators. In cooperation with the Pacific Aero Products Company of Seattle, we have spent considerable time and effort developing ceramic and other composite armor technologies, and believe that we have managed to develop an armor package similar in concept, but less protective, than the BRL-1 armor used on early model pre-war M1 Abrams tanks. Our testing has determined that the armor package we have chosen for the vehicle is substantially lighter and more protective than rolled homogeneous steel or cast steel armor, although it is bulkier and substantially more expensive. We have been particularly focused on Carborundum (Silicon Carbide) as the ceramic used in the armor, although experiments have determined that Boron Carbide offers more protection, but is substantially more difficult to manufacture and work with. While large quantities of B4C exist at the Hanford Site in the form of neutron dampers and shielding, and control rods, they would require substantial effort to form into a usable armor material and at this time the yield rate on B4C tiles of the appropriate size is low to the point of total impracticality - at best, we have determined that current technology will produce no more than 5% of a given batch of tiles that meets QA/QC. We have therefore determined that the most weight and efficient armor scheme would be to more-or-less duplicate the HAP-1 armor construction, substituting Silicon Carbide for Boron Carbide where appropriate, and utilizing the supplies of depleted uranium available at the Hanford Site (estimated to be 2,380 tons, appropriate for approximately 750 vehicles based on current projections of 6000lb of DU per vehicle) would provide substantial kinetic protection at the cost of increased weight. Our armor concept, admittedly very heavily inspired by that of the early M1 Abrams designs, provides significant protection for its weight, especially considering the smaller protected volume and reduced level of protection chosen. The turret faces are intended to provide protection equivalent to 20-25 inches of rolled homogeneous steel, but are some 70% lighter. We would note that the Cascadian Government should seek to acquire access to greater supplies of uranium for use in this and other defence programs, and note that research indicates four thousand tons of dry-cask stored spent nuclear fuel each in the former Illinois, former Pennsylvania, and former South Carolina regions and between 3,000 and 4,000 tons each in California, former Alabama, Florida, New York, and Georgia regions. While most of these areas are over a thousand miles away, if Cascadia can secure access to these supplies, they represent approximately 32,500 tons of highly enriched uranium, which would be invaluable for reprocessing into depleted uranium for tank armors, or Special Materials for use in other programs. PACAR-RSL has been making inquiries through traditional trade channels as to the feasibility of cross-country transportation of these materials, but government support would aid the endeavour greatly. It is worth mentioning that this armor design package more-or-less requires the production of a gaseous-diffusion uranium enrichment cascade and the production of weapons-grade uranium. This could be expected to produce 16.9 tons of U-235, enough for over two thousand 25-kiloton nuclear devices. Further protection comes from the incorporation of Contact, an explosive reactive armor derived from the Soviet Kontakt-5 tiles. These require no outside initiation, being a box with two steel plates sandwiching a piece of explosive, and the 150 tiles used on the vehicle only add 1,900lb including mounting hardware while providing greatly increased protection. Firepower: Other work with the Pacific Aero Products Company focused on the development of improved ammunition designs. PACAR-RSL leveraged PAPC’s advanced aerodynamic analytical techniques to aid in the development of improved fin-stabilized smoothbore ammunition. Research on prewar technologies demonstrated a number of programs conducted by the prewar US Army that incorporated smoothbore guns, and industrial analysis has determined that a maximum chamber-pressure of 55,000psi is within current capabilities, and based on research trends in metallurgy, a chamber pressure of 75,000psi should be achievable within five years, and 100,000psi in ten years. While this will result in a lengthened gun compared to prewar designs (The M256 120mm gun was only a 44-caliber gun), a 50-caliber 120mm gun with a tube weight of not more than 2,900lb and an all-up weight of not more than 4,400lb is entirely viable. We have developed a gun, the 120mm Gun T123E7, that produces a muzzle energy of 4,300 ft-ton with a 50lb armor-piercing capped, ballistic capped projectile (MV = 3,500ft/sec, 50lb shot M358). We estimate that this will drive a 22lb Hanfordite (U-238) penetrator at approximately 4,500ft/sec, giving the capability to defeat greater than 25” of rolled homogenous steel at 2,000 yards, and greatly simplifying the design of the ballistic computer. It uses a vertically sliding breechblock reverse-engineered at great length from surviving examples of the Watervliet Arsenal-produced M256 120mm gun. While the current metallurgy and QA/QC is not sufficient to produce breech blocks capable of the 135,000psi of M256, we believe that with advances in electronically controlled machining, it is feasible. We are planning an exploratory expedition to the Watervleit Arsenal area to gain what prewar technical data we can, particularly on the M256 and M360 guns. T123E7 is a 52-caliber 120-mm smoothbore gun with a vertically sliding breechblock, hydropneumatic recoil mechanism, and chrome-lined bore. It fires 120x570mm fixed ammunition using a cellulose-fiber combustible cartridge case with a metal base cap, reducing the weight of the cartridge case by some 30lb compared to a brass case (107lb for brass case M358 APC-T vs ~55lb for T494 APFSDS-T). Decreased AP projectile weight due to the usage of armor-piercing fin-stabilized discarding sabot ammunition further reduces the weight of the armor-piercing projectile by nearly half, from 50lb to 26lb. Additional projectiles, such as HEP-FS-T, HE-FRAG-FT-T and HEAT-FS-T are under development, as are training projectiles. The gun and mount are electrically driven in train and elevation via a geared drive and proportionally controlled motors derived from a mixture of naval fire control equipment and enlarged aircraft gun turrets. This has an added benefit of easing the development of an analog two-axis gun stabilization system. The fire control system is electromechanical and analog-electronic, and consists of [x] components: the gunner’s articulated periscope, the commander’s stereoscopic rangefinder, the electrical gun drive, and the gun computer. The gun computer is a miniaturized transistorized electromechanical/analog-electronic computer that incorporates ambient temperature, range as measured from the stereoscopic rangefinder, and the average rate of traverse of the gun over the past one to three seconds to apply lead, cant correction, and superelevation, and align the gun to the sights. When the firing switch is depressed, a set of microswitches waits to close the firing circuit until the sights are properly aligned, aiding in firing on the move or from a short halt. The gunner’s articulated periscope is a combination 1x-3x unity sight and 3-20x magnified sight, with coated lenses, reticle illumination, and compatibility with infra-red image intensifying night vision equipment. The rangefinder is mounted across the width of the turret. There is a 7.62mm M240 machine gun mounted coaxially to the main gun, with 8,000 rounds of 7.62x51mm (2,000 ready). There is a 7.62mm M240 machine gun provided for the loader mounted in a race-ring mount around his hatch with 2,000 rounds of 7.62x51mm (200 ready) There is a .50 M2 machine gun provided for the commander on a ring mount around the commander’s cupola with 2,000 rounds of .50 ammunition (100 ready) Provision is made for the storage of the crew’s individual weapons and field equipment, including four 5.56mm rifles and ammunition. Mobility: T44 uses a torsion-bar suspension, with six individually sprung road-wheels per track connected to double-acting bar-in-tube springs providing substantially improved suspension travel to the original single-acting suspension. There are two powertrains currently proposed. The first, a prewar design Continental AVDS-1790-5B is a known quantity, an extremely reliable and widely used turbosupercharged diesel V-12 producing 810 horsepower at 2,400RPM. This, in combination with the CD-875-2 four-speed automatic transmission produces a maximum speed of 35 miles an hour on road, and the improved double-acting torsion bar suspension provides an increased rough-terrain speed of approximately 12 miles per hour, compared to nine miles an hour for the Medium Tank M4. This gives the vehicle a combat range of approximately 125 miles. The second powertrain is derived from prewar work on gas turbines. It is a simple, reliable gas turbine of 65” length and 25” diameter that, due to manufacturing limitations, only produces about 1,000 horsepower. Similar prewar designs produced approximately 1,500 horsepower in ground use and 1,800 horsepower in aviation use, but due to manufacturing limitations and for safety reasons, the turbine is limited to 1,200hp SHP emergency power for ten minutes, and 1,000 horsepower maximum. This drives a CD-1250-1 crossdrive automatic five-speed transmission, resulting in a maximum road speed of 48 miles per hour and a rough-terrain speed of 22 miles per hour, although crew comfort is a significant concern and shock absorption is an issue at such speeds. This engine, with the associated APU, gives the vehicle a combat range of approximately 150 miles, as the reduced engine dimensions allowing increased fuel capacity. In summary, the T44 medium tank meets all of the required design specifications: It is 90,000lb unloaded The fenders fold up to ensure a 129” maximum width (otherwise 135” width) The upper frontal plate is 3” thick sloped at 80 degrees from vertical, giving an effective line of sight thickness of 17” The side armor is 3” thick The power to weight ratio is at worst 16hp/ton (loaded, 810hp engine) and at best 19.6hp/ton The tank has a crew of four: Driver, TC, gunner, and commander. The primary armament, 120mm gun T123E7, is capable of firing both antiarmor and high explosive projectiles.
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