Rocket engine

The rocket engines are reaction engine used on the rocket S, almost all are designed to function as well out of the terrestrial atmosphere as on the level of the ground or of the sea, with this intention, They embark to them Comburant in addition to their Carburant.

There exist two main categories of rocket engines:

  • rocket engine with Propellent S solids;
  • rocket engines with liquid propellents.

Combustive fuel/

Various couples carburizing/combustive, can be used in these engines.

  • Poudre+oxygène . Used for the fused of fireworks like in supplement of power on the takeoff of the planes very large transport aircrafts and the launch vehicles of space vehicles.

  • Hydrogène+oxygène . extrèmement difficult to use because of the inflammability of the Hydrogen, this couple is dangerous of use because of the high risks of explosion. It is employed by the American Space shuttle (with its Booster S with powder for the primary rise). It is also used by the engine Snecma HM7-B (ARIANE 4) and by the driving Vulcan and Vulcan 2 (ARIANE 5).
  • Kérosène+oxygène . Easy of employment but less powerful than the Hydrogène+oxygène couple. It is used by the rockets Soyuz and was used by the first stage of the lunar rocket Saturn 5.
  • Métal+oxygène . In certain cases, one uses the fast simple metal oxidation like chemical reaction. For that, it is necessary to pulverize metal in order to increase the surface of combustion, some powders are thus made by using Aluminum, Soufre, Magnésium (as in certain old lamps photographic Flash S), or of the Lithium.

In a general way, the most current fuels (and simplest) are:

Combustive the simplest is:

The most current propellent couples are:

  • Oxygen liquid/Kerosene (Soyuz, Saturn 5 (1st stage))
  • Oxygen liquid/Hydrogen liquid (space shuttle, ARIANE 5, Delta IV, Energia, Saturn 5 (2e and 3e stage))
  • Tétraoxyde of nitrogen (N2O4)/asymmetrical dimethylhydrazine (UDMH) (Proton, ARIANE 1 to 4 (1er and 2e stage), Vanguard)

To give an example of real complexity (beyond basic information given higher), in the case, very mediatized, of the Booster rocket S of the American Space shuttle, the mixture of Ergol in each engine of booster rocket consists of (% mass):

  • 69,6% of Perchlorate of ammonium - the combustive one/oxidant
  • 16% of aluminum - the Polymeric fuel
  • 12,04% of which makes it possible to bind the two components
  • 1,96% of an agent of cleaning epoxy
  • 0,4% of iron oxide - catalyst

Engines with propellents liquid

These engines use propellents stored in separated tanks, which are injected into a combustion chamber then ejected by the conduit, generating the push.

Example: Soyuz, booster rocket of Energia,

Engines with hypergolic propellents

The hypergolic propellents have the characteristic to blaze up spontaneously when they are put in contact, which makes it possible to simplify the engine.

Example: the engine of increase of the lunar module of the Program Apollo, engines of operation of the space shuttle.

Engines with cryogenic propellents

These engines use stored cryogenic propellents at very low temperatures. The only propellent couple of this type used in real situation is Oxygène liquid/Hydrogène liquid.

Example: principal engine of the American space shuttle, the driving main thing of ARIANE 5, the driving main thing of Energia.

Engines with solid propellents

These engines use a mixture of propellents in solid form. One uses then the term of Propergol to indicate an autonomous reducing mixture oxidizing/or semi-propellent when another component must be brought (for example: air in a Ramjet).

The engines with solid propellent consist of a body of engine filled with propellent which can be formatted at share then set up in the body of engine, or run then cooked in situ in the body of engine, which is generally the case for the large recent engines.

Combustion proceeds ideally in parallel layers. The initial geometry of the block of propellent then fixes the law of evolution of surface of the block, therefore its law of flow and push. The most current geometries are:

  • with frontal combustion: the block burns " in cigarette" , i.e. with a weak compared to volume but constant surface of combustion;

  • with a channel: a channel is practiced in the axis of the block and combustion evolves/moves radially. The channel can be axisymmetric or present a particular reason, often out of star.

Example of engines with solid propellent: Booster rocket S with powder of the American space shuttle, booster rockets with powder of ARIANE 5, Russian also used sometimes these engines, the majority of the engines of tactical or ballistic missiles.

Close subject

See also: Priming

One wonders sometimes why the flame produced on the outlet side of the engine of rocket does not go up not until in the tanks and its contents do not ignite in a brutal way. In fact, it is acted simply owing to the fact that the speed of ejection of the product of combustion is largely more important than the propagation velocity of the chemical reaction. It is thus maintained a flame which does not start that at a certain distance from the engine stops.

See too

Internal bonds

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