Mk4

Design of the Mk4 was started with the formation of the Los Alamos Laboratory Z-Division August 2, 1945._3.1With development delayed by weapons testing in the Marshal islands taking place with operation CROSSROADS and SANDSTONE, the Mk4 entered the stockpile in March of 1949._{3.1, 5.1}

The Mk4 with its original steel case weighed roughly 10,900lbs. This casing was designed to protect the weapon from shrapnel and flak, however, the military decided to forego this feature in favor of a lighter assembly for increased range of the aircraft._2.1 With a riveted or welded aluminum ballistic case both being feasible in preliminary tests, the riveted casing was selected for future use with the Mk4 (eventually becoming the Mk6), however both the riveted and welded cases were produced to save time in early production._2.2

Center of gravity is 43.43″±0.25″ from the nose. Its general shape is that of a modified “C-class” airship; it has a 29″ diameter flat nose and a 33″ diameter at the rear. The tail fins are the double-wedge type having a 5°44′ including angle at the leading edge and a 25°44′ angle at the rear of the fin. The surface of the bomb is free of noticeable protrusions, and provides read access from the rear of the bomb bay since it does not incorporate shrouds or drag plates._6.2

The equipment required for handling, assembling, and testing the Mk4 Mod 0 FM is divided into Types 1, 1A, 2, 3, and 4 in such a manner that all necessary bomb operations can be efficiently performed. Types 1 and 1A, 2, 3, and 4 have been given contracting names, i.e., “kits”, “lots”, “groups”, and “sets”, respectively._6.4

1. Type 1 – Field Equipment – Kits; Type 1 equipment is divided into kits which contain the tools and equipment required by assembly teams for field assembly and field testing of the bomb and minor maintenance of test equipment. These kits are the following:
   1. Cartridge Test Kit – 40A: The Cartridge Test Kit contains all test equipment, tools and auxiliary equipment required for the complete testing of the fuzing and firing components of the bomb. The major items in this kit are a Flight Test Box, Delta Timer, Peak-Reading Voltmeter, Archie Test Panel, Baro-Switch Tester, Junction Box Tester, Flight Circuit Tester, High Potential Tester, Unit Tester, Meter Calibrator, and Cartridge Dolly._6.4
   2. Battery Kit – 40C: The Battery Kit contains sufficient equipment to prepare batteries for nine bombs per day with one spare battery clamp for each bomb or for twelve bombs per day without spares. If a greater number of batteries is needed additional kits will be required._6.5
   3. Field Mechanical Kit – 40F: This kit contains the necessary equipment to enable two assembly operations to be carried on simultaneously. Major items in this kit are a Portable Frame Assembly, Wishbone trailer, Split-Band Dolly and Spreader, Vacuum Pump and Lift Cup, Sphere Support, Portable Work Table, and Detonator Circuit Ohmmeter._6.5
   4. Test Equipment Repair Kit – 40Q: This kit contains tools and equipment necessary for field repair and calibration of test equipment._6.5
   5. Nuclear Kit – 40S: The Nuclear Kit includes tools and equipment for monitoring the nuclear material and for all nuclear work involved in the preparation for an insertion of the capsule into the bomb._6.5
2. Type 2 – Operational Equipment – Lots; Type 2 equipment is divided into lots which contain equipment of a special nature required for dispersal, transport, delivery, and testing during the delivery of atomic bombs. The lots are as follows:_6.5
   1. Lot 40 I: (at the time this report was written, the contents had not been definitely defined) but it will contain items such as a dispersal cradle for supporting the bomb prior to loading into the strike aircraft, and a Flight Test Bomb which is installed in the strike aircraft for flight check of the bomb._6.6
   2. Lot 40 T: (This lot is still classified Secret)_6.6
3. Type 3 – Base Equipment – Groups; Type 3 equipment is divided into groups which contain tools and equipment required at bases for major disassembly, long-term surveillance, and major maintenance. Base equipment will not be used for field assemblies. The various groups are the following: Group K: Canning; Group R: Nuclear; Group U: Instrument Repair; Group V: Electrical; and Group N: Mechanical_6.6
4. Type 4 – AFSWP Support – Sets; Type 4 equipment is divided into sets which contain items of support equipment for the military field organization such as material for shelter, power, disaster cleanup , and expendable stock. It will be the responsibility of the using forces to determine and procure most of the items in these sets. The various sets are the following: Set J: Expendable Stock; Set L: Heavy Tool; Set W: Disaster; Set X: Salvage; Set Y: Building; and Set Z: Power._6.6

The Snark missile used a Mk4 warhead_4.1

Had a reported drag coefficient of 0.54 with ballistic shell_1.1

128″ long and 60″ in diameter, weighing 10,900lbs±240lbs_3.2

Completely assembled unit weighed 10,866lbs_6.1