Cryogenic Engine

Start music   Aug 27 2016 || 1:08 PM


  • A cryogenic rocket engine is a rocket engine that uses a cryogenic fuel or oxidizer, that is, its fuel or oxidizer (or both) is/are gases liquefied and stored at very low temperatures.
  • Cryogenic engines are fundamentally different from electric motors because there isn't anything rotating in them. They're essentially reaction engines, working according to Newton's law: "to every action there is an equal and opposite reaction."
  • The cryogenic (or rocket) engine throws mass in one direction, and the reaction to this is a thrust in the opposite direction. This thrust lifts the rocket, and helps in the launching and movement of the rocket.
  • Cryogenic rocket engines are more efficient than solid propellant based engines. They can deliver more thrust for a given mass of propellant. This is particularly useful for raising heavier payloads to higher orbits. When compared t

    o conventional liquid rocket engines using fuel storable at room temperature, cryogenic engines develop 1.5 times more thrust.

  • For the propellant to be efficient, it should develop greater thrust per unit mass of propellant consumed per unit time, a factor which we call Specific Impulse (Isp). High values of specific impulse are obtained from high exhaust gas temperature and from exhaust gas having very low (molecular) weight.
  • To be efficient, therefore, a propellant should have a large heat of combustion to yield high temperatures, and the combustion products should contain light molecules made of elements such as hydrogen (the lightest), carbon and oxygen.
  • Another important factor is the density of a propellant. A given weight of
  • A dense propellant can be carried in a smaller, lighter tank than a low-density propellant of the same weight.
  • The advantage of cryogenic propellants is that they are the most energetic and, therefore, have the highest specific impulse. The (liquid hydrogen + liquid oxygen) combustion yields the highest amount of total energy and the product of combustion is water vapour, with a low molecular weight.