V-2 Turbopump Unit cutaway on display shows some of the pumps' moving parts. The turbopumps forced 128 pounds of alcohol and 159 pounds of liquid oxygen into the V-2's combustion chamber every second. (U.S. Air Force photo)
Note: The Missile & Space Gallery will close temporarily, beginning Dec. 8, 2014, for approximately five months for construction linking the gallery to the museum's new fourth building. This exhibit will not be accessible during that time. Click here for more information.
This rocket engine powered Germany's V-2 "Vengeance Weapon" during World War II. The engine was a technical achievement, using high-speed pumps to move large volumes of fuel into the thrust chamber very quickly. Its design also contributed to American rocketry following WWII.
The V-2's liquid oxygen and alcohol propellants produced a thrust of 56,000 pounds, giving the rocket a maximum range of 220 miles, a ceiling of 50-60 miles and a speed of 3,400 mph. Germany made about 6,000 V-2s during 1944-1945 and launched more than 2,600 against London, Antwerp, Liege, Brussels, Paris and Luxembourg.
Powering the V-2 Rocket
The German V-2 of WWII featured the largest and most powerful rocket engine up to that time. Very advanced for the 1940s, it paved the way toward more powerful rockets developed in the 1950s and later. Two critical engine parts -- the turbopump assembly and the thrust chamber -- are components of the complete engine on display in the museum's Missile & Space Gallery. An entire V-2 rocket is on display in the World War II Gallery.
Large liquid rocket engines require massive amounts of propellants to be fed into the combustion chamber quickly and under high pressure. This was accomplished on the V-2 by using high-speed gas-turbine pumps, or turbopumps. These pumps -- one to move liquid oxygen, the other to move alcohol -- were steam powered. Steam pressure came from the chemical reaction of combining two liquids, sodium permanganate (tank A) and hydrogen peroxide (tank B). The turbine developed 580 horsepower and turned the pumps at about 3,800 revolutions per minute. The cutaway on display shows some of the pumps' moving parts. The turbopumps forced 128 pounds of alcohol and 159 pounds of liquid oxygen into the V-2's combustion chamber every second.
High-speed turbopumps have been critical rocket engine equipment for many decades, and even the most recent rockets use them. The space shuttle's main engines, for example, use turbopumps that deliver up to 970 pounds of liquid oxygen and 162 pounds of liquid hydrogen per second.
Another important component in the V-2 design was its thrust chamber, which had three important features: its propellant-mixing system, its cooling method and its shape.
Mixing: The twin turbopumps forced alcohol and liquid oxygen through small nozzles under high pressure into mixing "cups" at the top of the chamber. These innovative nozzles sprayed a mist of tiny droplets, making the mixture burn efficiently and with tremendous force.
Cooling: The temperature inside the thrust chamber was about 4,800 degrees Fahrenheit, hot enough to melt steel. Cooling the chamber, therefore, was critical to preventing the engine from destroying itself. The V-2's designers used two methods to cool the engine: regenerative cooling and film cooling. Regenerative cooling used the rocket's water/ethyl alcohol fuel to remove excess heat. This liquid circulated between the thrust chamber's double walls, cooling them before being forced through the injector nozzles. At the same time, film cooling used a thin layer of alcohol to cool the inner chamber walls. This alcohol film was injected through small holes in the chamber wall and formed a barrier between the rocket's flame and the chamber structure.
Regenerative and film cooling were used on later rockets with great success. The massive Apollo moon rocket engines, the space shuttle orbiter's main engines, and many Air Force liquid rocket engines relied on these fundamental techniques as rocket power increased in the decades after WWII.
Shape: The chamber's short, round shape made the engine more efficient than older designs which were longer and thinner. The round upper part mixed and burned propellants effectively, and the wide opening at the bottom allowed rapidly expanding gasses to escape with minimal friction. Careful design of thrust chambers is important to liquid rocket engines because the power and stability of fuel combustion depends largely on the shape and size of the chamber.
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