The A4 rocket motor was a liquid propelled rocket used to power the German V-2 WW2 ballistic missile and was developed in the early 1940's by a team led by Wernher von Braun, the A4 rocket motor produced 25 tonnes of thrust for about 60 seconds in operational use, this gave the V-2 missile a maximum range of 234 miles and a maximum altitude of between 50 and 60 miles at the height of it's parabolic ballistic arc. The distance travelled was controlled by cutting off the fuel to the motor at a pre determined height and the resulting accuracy was normally three to 10 miles from the desired aim-point.
How did the V-2's A4 rocket motor work? Please scroll down!
A compressed air tank pre-charged to 550 psi was used to pressurise two tanks, one filled with hydrogen peroxide the other a mixture of sodium permanganate/water, these were mixed together where the hydrogen peroxide then violently reacted with the sodium permanganate/water catalyst producing vast amounts of superheated high pressure steam at a temperature of 385 degrees Celsius. The steam was used to power a steam turbine which produced 580 Hp at over 5,000 rpm , this directly drove two high flow centrifugal vane pumps, one pumped the "B-Stoff" fuel, 75% ethyl alcohol and 25% water, at the rate of 3,710 kg per minute, the second pumped the oxidizer "A-Stoff" which was liquid oxygen (LOX) at the rate of 4,900 kg per minute.
The liquid oxygen was pumped in to a distributor which fed 18 burner-cups mounted directly on the top of the combustion chamber via individual pipes, the liquid oxygen then entered the main combustion burner via 1,224 nozzles within the burner-cups. The main combustion burner was double walled and the ethanol/water fuel was pumped into the bottom of this cavity effectively providing a cooling jacket around the inner combustion chamber wall and also pre-heating the fuel mixture before it entered the top of the combustion burner where it mixed with the oxygen and then ignited.
A small percentage of the fuel was allowed to "bleed" through carefully located holes from the combustion chamber's cooling jacket into the lower part of the combustion chamber, as the oxygen had already been burnt higher up in the chamber, the fuel could not burn and provided a relatively cool boundary layer between the incredibly hot exhaust gases and the surface of the vulnerable combustion chamber inner wall. Once expelled from the A4 rocket motor the vaporised boundary layer fuel would burn using the oxygen in the atmosphere creating the V-2's characteristic feather like fiery plume.
It is noteworthy that the ethyl alcohol fuel was produced by fermenting potatoes, it required 30 tons of potatoes to produce the fuel to run a single A4's rocket motor for it's average 60 second operational burn, Also most operational V-2's were painted green/brown of just green for camouflage before launch, the black and white checker board paint scheme often depicted was used on test rockets so that observers could easily determine if the rocket was spinning.