section_path: Engines
section_name: Engines
paragraph_text: Engines
  
  To date, Firefly is the only organization to develop an orbital-class rocket engine utilizing the combustion tap-off cycle, and the only organization to develop a tap-off cycle engine using RP-1 (highly refined kerosene) and liquid oxygen, also known as a kerolox engine.
  
  This engine type eliminates traditional gas generators and instead opts to "tap off" the main combustion chamber, utilizing the high heat and pressure within it to drive the pumps.
  
  This provides a slight increase in specific impulse and results in a dramatically simpler and lighter engine, in exchange for increased engineering complexity and requiring more exotic materials in order to handle the high heat and pressure. The startup sequence is also more challenging.
  
  As a result of these challenges, tap-off has been largely ignored, with the only other engines using it being the Rocketdyne J-2S and Blue Origin BE-3PM, which are both hydrolox engines (fueled by liquid hydrogen).
  
  Firefly designed both Reaver and Lightning in close cooperation with Firefly Aerospace Ukraine which had status of Ukrainian subsidiary of Firefly. Firefly Aerospace Ukraine hadn't any relations to other Ukrainian aerospace companies like Yuzhnoye and Yuzhmash. However Yuzhmash was involved in production of some engine components. There were plans to use Yuzhmash for mass production of Firefly engines but these plans were cancelled.