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Davy Crockett (nuclear device)

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M28/M29 Davy Crockett
A Davy Crockett at the Aberdeen Proving Ground, Maryland, 1961
TypeNuclear recoilless gun
Place of originUnited States
Service history
Used byUS
WarsCold War
Production history
Variants
  • M28
  • M29
Specifications
Mass
  • M28 108.5 pounds (49.2 kg), unloaded[1]
  • M29 316 pounds (143 kg), unloaded[1]
Crew5
Elevation5-800 mils (0.3 - 45 degrees)[1]
Effective firing range
  • M28 1.25 miles (2.01 km)
  • M29 2.5 miles (4.0 km)

The M-28 or M-29 Davy Crockett Weapon System was the tactical nuclear recoilless gun (smoothbore) for firing the M-388 nuclear projectile that was deployed by the United States during the Cold War. It was one of the smallest nuclear weapon systems ever built, with a yield between 10 and 20 tons TNT equivalent (40–80 gigajoules). It is named after American folk hero, soldier, and congressman Davy Crockett.

History

The Davy Crockett recoilless spigot gun was developed in the late 1950s for use against Soviet and North Korean armor and troops in case war broke out in Europe or the Korean peninsula. Davy Crockett Sections were assigned to United States Army Europe and Eighth United States Army armor and mechanized and non-mechanized infantry battalions. During alerts to the Inner German border in the Fulda Gap the Davy Crocketts accompanied their battalions. All V Corps (including 3rd Armored Division) combat maneuver battalions had preassigned positions in the Fulda Gap. These were known as GDP (General Defense Plan) positions. The Davy Crockett sections were included in these defensive deployment plans. In addition to the Davy Crocketts (e.g., assigned to the 3rd Armored Division), V Corps had nuclear artillery rounds and Atomic Demolition Mines, and these were also targeted on the Fulda Gap. On the Korean peninsula, units assigned the Davy Crockett weapons primarily planned to use the passes that funneled armor as killing grounds, creating temporarily deadly radioactive zones roadblocked by destroyed tanks and other vehicles.

M388 Nuclear Round

Annotated photograph of a training-dummy version of the M388 nuclear round[2]

The M388 round used a version of the Mk-54 nuclear warhead, a very small sub-kiloton fission device. The Mk-54 weighed about 51 pounds (23 kg), with a yield equivalent to somewhere between 10 and 20 tons of TNT—close to the minimum practical size for a fission warhead,[Note 1] and comparable in yield to the largest conventional bombs developed at the time.[Note 2]

Controls on the projectile included a two-position, height-of-burst switch, which could be set to near-ground or medium-height detonation; a safety switch with 'safe' and 'arm' positions; and a time setting dial that allowed a time delay between 1 and 50 seconds before the fuze armed. If the time delay was greater than the time-of-flight, the weapon would hit the ground before it armed and not detonate. The time dial also had a 'safe' setting, and so acted as a second safety switch.[3]

The complete round weighed 76 pounds (34 kg). It was 31 inches (79 cm) long with a diameter of 11 inches (28 cm) at its widest point; a subcaliber piston at the back of the shell was inserted into the launcher's barrel for firing.[4] The M-388 atomic projectile was mounted on the barrel-inserted spigot via bayonet slots. Once the propellant was discharged the spigot became the launching piston for the M-388 atomic projectile: this was necessary because the fission round could not be subject to high acceleration and the spigot/piston, acting as a "pusher tube", facilitated this.[5]

Practice Rounds

The M390 practice round was outwardly similar the nuclear round and was designed to be a ballistic match to it. It contained 16 pounds (7.3 kg) of Composition B high explosive that was detonated by an electrical switch on impact with the ground. The practice round had a significant destructive effect in its own right and was intended to be used in combat in an emergency situation. A further type of dummy training round, the M421, was completely inert and not intended to be fired.[6]

Launcher

Propellent charge is loaded
Launch piston is inserted
The M-388 nuclear round is attached to the launch piston
Loading a Davy Crockett M29 Launcher[7]

The M-388 could be launched from either of two launchers known as the Davy Crockett Weapon System(s): the 4.7-inch (120 mm) M28, with a range of about 1.25 miles (2.01 km), or the 6.1-inch (150 mm) M29, with a range of 2.5 miles (4.0 km). Both weapons fired the same projectile, propelled using a separate cartridge. The smaller M28 used a 11-pound (5.0 kg) explosive cartridge to launch the warhead. The larger M29 used an 11-pound or a 19-pound (8.6 kg) propellant charge, depending on the desired range.[8] The launcher systems were muzzleloading weapons. As they were intended for a very low rate of fire a breechloading mechanism was unnecessary.[5]

The weapon was fired remotely using a mechanically-operated detonator at the end of 22 metres (72 ft) of detonating cord that led to the propellant charge.[9] The M-388 warhead was attached to a titanium piston that was inserted into the launcher tube. This was blown out of the tube by the detonating propellent and separated from the nuclear projectile after a few meters of flight, falling to the ground several hundred meters in front of the weapon while the projectile continued to the target.[10]

Davy Crockett launchers were either mounted on a tripod launcher transported by an M113 armored personnel carriers, or they were carried by a Jeep (the M-38, and later the M-151). The Jeep was equipped with an attached launcher for the M28 or the M29, as required, whereas the Davy Crockett carried by an armored personnel carrier was set up in the field on a tripod away from the carrier. Weapons assigned to infantry units were carried in M113s, those allocated to airborne units were carried on Jeeps.[11]

The Davy Crocketts were operated by a five-man crew, the squad consisting of a Commander, Gunner, Assistant Gunner, Loader and Computer. It was possible to break the smaller M28 weapon into five loads that could be carried by the crew.[12] Operating the M28 or M29 versions of the weapon with a three-man crew was also possible.[13]

In the 3rd Armored Division in Germany in the 1960s many Davy Crockett Sections (all of which were in the Heavy Mortar Platoons, in Headquarters Companies of Infantry or Armor Maneuver Battalions) received what became a mix of M28 & M29 launchers [e.g., one of each per D/C section]. Eventually, the M28s were replaced by M29s, so that both the armored personnel carriers and the Jeeps carried the M29.

Effects

The weapon's Mushroom cloud, July 17, 1962
In 2008
The Little Feller I nuclear test site

Both recoilless guns proved to have poor accuracy in testing, so the shell's greatest effect would have been its extreme radiation hazard. The M-388 would produce an almost instantly lethal radiation dosage (in excess of 10,000 rem, 100 Sv) within 500 feet (150 m), and a probably fatal dose (around 600 rem, 6 Sv) within a quarter mile (400 m).[14] The weapon did not have an abort function; if fired, the warhead would explode.[15]

The warhead was tested on July 7, 1962 in the Little Feller II weapons effects test shot, and again in an actual firing of the Davy Crockett from a distance of 1.7 miles (2.7 km) in the Little Feller I test shot on July 17. This was the last atmospheric test detonation at the Nevada Test Site.

Production of the Davy Crockett began following the 15 August 1958 (at) Picatinny Arsenal approval of the design, with a total of 2,100 being made. The weapon was tested between 1962 and 1968 at the Pohakuloa Training Area on Hawaiʻi island, with 714 M101 spotter rounds (not live warheads) that contained depleted uranium.[16][17] The weapon was deployed with US Army forces from 1961 to 1971. It was removed from US Army Europe (in West Germany) in August 1967.[18]

The 55th and 56th Infantry Platoons, attached to the Division Artillery of the US 82nd Airborne Division, were the last units equipped with the M-29 Davy Crockett weapons system. These two units were parachute deployed and, with a ½ ton truck per section (three per platoon), were fully air droppable. The units were deactivated in mid-1968.

Proposed German military use

One of the most fervent supporters of the Davy Crockett was West Germany's defense minister Franz Josef Strauss, in the late 1950s and early 1960s. Strauss promoted the idea of equipping German brigades with the nuclear weapon, to be supplied by the US, arguing that this would allow German troops to become a much more effective factor in NATO's defense of Germany against a potential Soviet invasion. He argued that a single Davy Crockett could replace 40–50 salvos of a whole divisional artillery park – allowing the funds and troops normally needed for this artillery to be invested into further troops, or not having to be spent at all. US NATO commanders strongly opposed Strauss's ideas, as they would have made the use of tactical nuclear weapons almost mandatory in case of war, further reducing the ability of NATO to defend itself without resorting to atomic weapons.[19]

Museum examples

A Davy Crockett casing preserved in the United States Army Ordnance Museum

The following museums have a Davy Crockett casing in their collection:

Notes

  1. ^ The theoretical minimum critical mass for 233U is close to 16 kg. (nuclearweaponarchive.org, euronuclear.org).
  2. ^ Grand Slam (1943) had a yield of 6.5 tons; T-12 Cloudmaker (1944) was designed for a yield of 11 tons. The largest yield for a conventional bomb reported as of 2017 was that of the Russian ATBIP (2007), at 44 tons.

References

Citations
  1. ^ a b c The Davy Crockett Weapons System (1961), pp.5-7
  2. ^ The Davy Crockett Weapons System (1961), p.37
  3. ^ The Davy Crockett Weapons System (1961), pp.42-43
  4. ^ "Characteristics of all US nuclear weapons designs", USA weapons, Nuclear weapon archive, retrieved October 20, 2006.
  5. ^ a b Engineering Design Handbook Recoilless Rifle Weapons Systems (PDF). Alexandria, VA: US Army Materiel Command. 15 January 1976. pp. 1–32.
  6. ^ The Davy Crockett Weapons System (1961), pp.43-44
  7. ^ The Davy Crockett Weapons System (1961), pp.133-134
  8. ^ The Davy Crockett Weapons System (1961), p.50
  9. ^ The Davy Crockett Weapons System (1961), p.52
  10. ^ The Davy Crockett Weapons System (1961), p.48
  11. ^ The Davy Crockett Weapons System (1961), p.129
  12. ^ The Davy Crockett Weapons System (1961), p.115
  13. ^ The Davy Crockett Weapons System (1961), p.112
  14. ^ "Section 5.6, Mechanisms of Damage and Injury", Nuclear Weapons (FAQ), Nuclear weapon archive, retrieved October 20, 2006.
  15. ^ "Davy Crockett: King of the Atomic Frontier". www.damninteresting.com. Retrieved 2015-07-24.
  16. ^ Miller, Erin (September 1, 2010). "Military says DU at PTA likely harmless: Army reports 'no likely adverse impacts' from spotting rounds". West Hawaii Today. Retrieved September 2, 2010.
  17. ^ "Pohakuloa Training Area Firing Range Baseline Human Health Risk Assessment for Residual Depleted Uranium" (PDF). Cabrera Services Radiological Engineering and Remediation. Hawaii, US: Army. June 2010. Retrieved September 2, 2010.[dead link]
  18. ^ History of the Custody and Deployment of Nuclear Weapons(U): July 1945 through September 1977; "Prepared by Office of the Assistant to the Secretary of Defense (Atomic Energy) February 1978", Page B-7.
  19. ^ "Bedingt abwehrbereit". Der Spiegel (in German). No. 41. DE. 1962.
Bibliography

Further reading

Wikimedia Commons has media related to M388 Davy Crockett.
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