RACER IV was a component of some of the first hydrogen bombs made by the United States during the 1950s . 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 . RACER was the second fusion-boosted fission device type incorporating the principles tested first with the BOOSTER in the Greenhouse Item ( the first was the modified MK-7 device tested in 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 . Its reliability issues ruled it out as a primary in the emergency capability devices , whose proper operation was imperative . Nevertheless it was fielded as primary to the relatively low risk Nectar ( ZOMBIE device ) with satisfactory performance , and to the highly innovative Koon ( MORGENSTERN device ) with disastrous effects
Greenhouse Item
Greenhouse Item
RACER IV