What type of engine does the x-15 have?

The X-15 rocket plane is equipped with a Reaction Motors XLR99 rocket engine. This engine uses a combination of liquid oxygen and anhydrous ammonia as propellants, allowing it to achieve high thrust levels. The XLR99 was capable of producing up to 57,000 pounds of thrust, enabling the X-15 to reach the edge of space and achieve hypersonic speeds.