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RACER IV was a component of some of the first

hydrogen bombs made by the United States during the 1950s. The RACER was developed in 1953 at Los Alamos National Laboratory


It was named after the snake of the same name as it was customary for Los Alamos to name primary devices after snakes and insects.[1]: 163 


RACER was the second fusion-boosted fission device type incorporating the principles tested first with the BOOSTER in the

Snapper Dog in 1952). It was initially intended to be the first stage for all but two (the SHRIMP and ZOMBIE devices) of the devices tested in the Castle series. The shots intended to make use of it were Romeo (RUNT device), Union (ALARM CLOCK device), and Yankee (JUGHEAD, later RUNT II devices), which tested weapon systems aiming to ensure emergency capability, as well as shots Koon (MORGENSTERN device) and Echo (RAMROD device) which were to test more exotic "next generation" systems.[2]: 196 : 236  Its reliability issues ruled it out as a primary in the emergency capability devices, whose proper operation was imperative.[2]: 101  Nevertheless, it was fielded as primary to the relatively low risk[3] Nectar (ZOMBIE device) with satisfactory performance, and to the highly innovative Koon (MORGENSTERN device) with disastrous effects.[2]
: 196 : 200 


The RACER was developed in 1953 at Los Alamos, was DT gas-boosted, and used a TOM initiator for internal initiation.[2]: 172  The boosting capsule was made of steel and was internally lined with copper, a standardisation derived from the Booster Ball[4]: 258  tested in the Item test. Inside the capsule, the TOM initiator was nested with a caltrop-like steel mounting. This method of assembly of the TOM initiator was known as sealed initiator, doing away with the mounting bracket employed in earlier pure-fission designs.[5][4]

Testing and finalisation

Several RACER cores were proof-fired during

Badger (Mark 16) with deuterium-only gas boosting, and a redesigned (RACER IV) core as shot Simon (Mark 17/24) with DT gas boosting. In its finalised, RACER IV configuration, two kilograms of HEU were added[3] to the initial (RACER) composite core design.[2]: 196  According to Chuck Hansen, during the Upshot-Knothole tests RACER exhibited inconsistent yield,[6] varying from 23 kilotons in the Badger and 24 kilotons in the Nancy shot, to 43 kilotons in the Simon shot (as the revised RACER IV version); the yields lay outside the predicted range of 35-40 kilotons.[2]
: 196 

Unpredictability and discontinuation

Concomitant to stringent yield predictability and reproducibility requirements, the design's bizarre yields meant that as a primary, RACER did not furnish the proper quantity and strength of x-rays and neutrons to implode and initiate respectively the secondary stage. Both x-ray and neutron fluxes were products of the fission process and the degree of fission in the RACER cores varied unpredictably as shown by the yield variability.[2]: 317  The unpredictable neutron flux had a catastrophic impact to the TX-22 program, as the MORGENSTERN prototype fizzled and its sister project RAMROD was canceled due to the poor performance of RACER IV.[2]: 318 


  1. ^ Hansen, Chuck (1995). Swords of Armageddon. Vol. IV. Retrieved 2016-12-28.
  2. ^ a b c d e f g h Hansen, Chuck (1995). Swords of Armageddon. Vol. III. Retrieved 2016-12-28.
  3. ^ a b "The Nuclear Weapon Archive - A Guide to Nuclear Weapons". Retrieved 23 September 2017.
  4. ^ a b Hansen, Chuck (1995). Swords of Armageddon. Vol. II. Retrieved 2016-12-28.
  5. ^ United States Nuclear Weapons. Globalsecurity.org. Retrieved on 2018-02-08.
  6. .