The nuclear yields of the large majority of USA nuclear weapons remain classified even when the warheads were retired and dismantled decades ago and even when releasing the information would seem to pose no plausibly articulated threated to USA national security. This practice is symptomatic and expressive of over-classification of nuclear weapons information in the USA. As as form of governmentality, these practices undermine prospects for an informed citizenry and for democratic governance of USA nuclear weapons. The primary purpose of this post is to demonstrate that the most likely yield of the W54 Davy Crockett nuclear projectile was 20tonnes (20t). Future posts, amongst other things, will examine the sociocultural ripple effects of nuclear secrecy (information management, as I call it).
Asking the Right People but Getting the Wrong Answers
The W54 Davy Crockett W54 Davy Crockett nuclear bazooka round was removed from the USA stockpile in 1971.2 It was a relatively lightweight and lower yield nuclear projectile designed for use by infantry against nearby targets of opportunity.3 The signage for the Davy Crockett exhibit at the Nuclear Museum in immediately below as is my transcription and offers an overview of the immediately relevant weapon characteristics:
“The Davy Crockett was a bazooka-type missile with a W54 warhead. The W54 was the lowest yield nuclear warhead ever deployed by the U.S. The Davy Crockett could be mounted on a jeep or a three-person team could carry it. The weapon system used a spin-stabilized, unguided rocket fired from a recoilless gun. Two types were made—a 120-millimeter with a range between 1,000 and 6,500 feet and a 155-mm with a range between 1,000 and 12,000 feet. The Davy Crocket also fired a conventional high-explosive round for use as an anti-tank weapon. The Davy Crockett brought nuclear capability to the infantry. It fired a powerful nuclear shell with an acceptable danger of radiation to the troops.
Specifications
Length……………… 30 inches
Diameter………….. 11 inches
Weight…………….. 76 pounds
Stockpiled……….. 1960-1971
Yield……………….. Tons“4
Without knowing the yield of the Davy Crockett, it is clearly impossible to judge the exhibit’s statement that the Davy Crockett “fired a powerful nuclear shell with acceptable danger of radiation to the troops.”
In 2019, I submitted a declassification proposal for the yield of the Davy Crockett to the Formerly Restricted Data Declassification Working Group. The response (screenshot below) concluded that “The FRD DWG carefully considered your declassification proposal and determined that the precise yields of the W54 warhead…cannot be declassified at this time. However, the yield of the warhead is in the sub-kiloton range.”5
Determining the Yield of the Davy Crockett
I assess with high confidence that it is highly likely the W54 Davy Crockett had a nominal yield of 20tonnes (20T). My argument is based on comparing nuclear test planning documents (released to me through the Freedom of Information Act) with modeling using Nukemap6 as well as on primary source documentation7. Nuclear yields are provided in terms of (metric) tonnes of TNT (trinitrotoluene, the explosive ingredient in dynamite) yield. That is, a nuclear weapon with a yield of 1 kilotonne (kt) has an energy output equivalent to 1,000 tonnes of TNT.
Using the Freedom of Information Act, I requested and received the Little Feller I, Test Group Director’s Concept (18 June 1962) report that provides an overview of the plan for the Little Feller I explosive nuclear test.8 Conducted on July 17, 1962, Robert F. Kennedy attended the test detonation as can be seen in video of the test: https://www.youtube.com/watch?v=xHiihPD7bLM
The Group Director’s Concept report gives a set of predicted air blast overpressures from detonating a Davy Crockett nuclear projectile at 40 feet above ground. I used Alex Wellerstein’s Nukemap to estimate the ranges of blast overpressures that a 20 tonne nuclear detonation at 40ft above ground level would produce.9
Below I have provided a chart that compares the blast effect ranges from the Little Feller I Concept Report and modeling from NUKEMAP for nuclear detonations of 20t and 10t. Unquestionably, the 20t model on NUKEMAP most closely matches the values given as expected in the Little Feller I Concept Report.
Comparison of Expected Blast Overpressures for Little Feller I Test to NUKEMAP Modelling for 20 and 10 tonnes of Explosive Yield
| Blast PSI overpressure | Test Plans Prediction | 20t Yield | 10t Yield |
| 100 | 95ft | 95ft | 76ft |
| 10 | 275ft | 295ft | 239ft |
| 1 | 1,100ft | 1,158ft | 945 |
Further drawing on NUKEMAP to predict the range of various intensities of radiation output of the Davy Crockett at 20t of yield, we get the following:
Radiation Dosage by Distance: 20tonne Davy Crockett using NUKEMAP
| REMs | Distance | Effects |
| 1,000 | 1,165ft | rapidly fatal; initially incapacitating |
| 600 | 1,339ft | fatal w/o medical treatment |
| 500 | 1,400ft | approx 50% fatal even w/medical treatment |
| 300 | 1,594ft | some fatalities, sickness likely |
| 200 | 1,772ft | few fatalities, increased cancer risk |
| 100 | 2,067ft | sickness possible & increased cancer risk |
The delivery ranges of the Davy Crockett systems are reported as 1,000 to 6,500 feet for the 120mm system and 1,000 to 13,000 feet for the 155mm system. In other words, at the lower ranges of delivery, a Davy Crockett crew without protection (eg, in a trench or behind shielding) could fatally irradiate themselves. Some vehicle mounted versions of Davy Crockett were apparently deployed with a 6-pack of nuclear shells. Firing multiple nuclear shells could have resulted in numerous and accumulating exposures. In the actual event of battlefield nuclear war in Europe, however, it seems unlikely that Davy Crockett crews would survive long enough to die from their own weapons.
Endnotes
- Wellerstein, Alex (2012). “King of the Wild Frontier. Restricted Data. Blog. https://blog.nuclearsecrecy.com/2012/07/20/king-of-the-wild-frontier/ ↩︎
- National Museum of Nuclear Science and History [NMNSH] (2023). “Davy Crockett.” Exhibit Text. Photographed September 10, 2023. ” ↩︎
- Department of the Army (1967). Davy Crockett Weapon Systems. FM 23-20. Washington D.C., page 40. Available here: https://osf.io/5msyn. ↩︎
- NMNSH (2023), “Davy Crockett.” ↩︎
- Formerly Restricted Data Working Group [FRDWG] (2019). “Declassification Proposal.” Letter to Martin Pfeiffer. ↩︎
- www.nukemap.com ↩︎
- US Army Corps of Engineers [USACE] (2007). Archive Search Report on the Use of Cartridge, 20mm Spotting M101 for Davy Crockett Light Weapon M28, Schofield Barracks and Associated Training Areas Islands of Oahu and Hawaii. Final Report. St. Louis District. page 140, available here: https://osf.io/rc5u9 ↩︎
- Defense Atomic Support Agency [DASA] (1962). Little Feller I: Test Group Director’s Concept. Extract Version. Washington D.C., https://osf.io/fuqcm ↩︎
- A permanent link to these settings is: Permanent link to these settings:
https://nuclearsecrecy.com/nukemap/?&kt=0.02&lat=38.8946925&lng=-77.0218993&hob_opt=2&hob_psi=5&hob_ft=40&psi=1,100,10&rem=&therm=2&zm=15.987791054183658 ↩︎
Works Cited
Defense Atomic Support Agency [DASA] (1962). Little Feller I: Test Group Director’s Concept. Extract Version. Washington D.C., https://osf.io/fuqcm
Department of the Army (1967). Davy Crockett Weapon Systems. FM 23-20. Washington D.C. https://osf.io/5msyn
Formerly Restricted Data Working Group [FRDWG] (2019). “Declassification Proposal.” Letter to Martin Pfeiffer.
National Museum of Nuclear Science and History [NMNSH] (2023). “Davy Crockett.” Exhibit Text.
Photographed September 10, 2023.
US Army Corps of Engineers [USACE] (2007). Archive Search Report on the Use of Cartridge, 20mm Spotting M101 for Davy Crockett Light Weapon M28, Schofield Barracks and Associated Training Areas Islands of Oahu and Hawaii. Final Report. St. Louis District. https://osf.io/rc5u9
Deus Ex Atomica: Anthropology and The Bomb 