The aviation industry had been studying this problem for some time. From the mid-1940s, there was interest in using nuclear-powered aircraft in the bomber role. In a conventional jet engine, thrust is provided by heating air using jet fuel and accelerating it out a nozzle. In a nuclear engine, heat is supplied by a reactor, whose consumables last for months instead of hours. Most designs also carried a small amount of jet fuel for use during high-power portions of flight, such as takeoffs and high-speed dashes.