5.5 KiB
| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| V-2 rocket | 2/10 | https://en.wikipedia.org/wiki/V-2_rocket | reference | science, encyclopedia | 2026-05-05T13:12:26.817016+00:00 | kb-cron |
The A4 used a 75% ethanol/25% water mixture (B-Stoff) for fuel and liquid oxygen (LOX) (A-Stoff) for oxidizer. The water reduced the flame temperature, acted as a coolant by turning to steam, augmented thrust, tended to produce a smoother burn, and reduced thermal stress. Rudolf Hermann's supersonic wind tunnel was used to measure the A4's aerodynamic characteristics and center of pressure, using a model of the A4 within a 40 square centimeter chamber. Measurements were made using a Mach 1.86 blowdown nozzle on 8 August 1940. Tests at Mach numbers 1.56 and 2.5 were made after 24 September 1940. At launch the A4 propelled itself for up to 65 seconds on its own power, and a program motor held the inclination at the specified angle until engine shutdown, after which the rocket continued on a ballistic free-fall trajectory. The rocket reached a height of 80 km (50 mi) or 264,000 ft after shutting off the engine. The fuel and oxidizer pumps were driven by a steam turbine, fueled by decomposition of concentrated hydrogen peroxide (T-Stoff) facilitated by a sodium permanganate (Z-Stoff) catalyst. Both the alcohol and oxygen tanks were an aluminum-magnesium alloy.
The turbopump, rotating at 4,000 rpm, forced the fuel mixture and oxygen into the combustion chamber at 125 liters (33 US gallons) per second, where they were ignited by a spinning electrical igniter. The engine produced 8 tons of thrust during the preliminary stage whilst the fuel was gravity-fed, before increasing to 25 tons as the turbopump pressurised the fuel, lifting the 13.5 ton rocket. Combustion gases exited the chamber at 2,820 °C (5,100 °F), and a speed of 2,000 m (6,600 ft) per second. The oxygen to fuel mixture was 1.0:0.85 at 25 tons of thrust; as ambient pressure decreased with flight altitude, thrust increased to 29 tons. The turbopump assembly contained two centrifugal pumps, one for the fuel mixture, and one for the oxygen. The turbine was connected directly by a shaft to the alcohol pump and through a flexible joint and shaft to the oxygen pump. The turbopump delivered 55 kg (121 lb) of alcohol and 68 kg (150 lb) of liquid oxygen per second to a combustion chamber at 1.5 MPa (218 psi). Dr. Thiel's 25 ton rocket motor design relied on pump feeding, as opposed to earlier pressure-fed designs. The motor used centrifugal injection, and used both regenerative cooling and film cooling. Film cooling admitted alcohol into the combustion chamber and exhaust nozzle under slight pressure through four rings of small perforations. The mushroom-shaped injection head was removed from the combustion chamber to a mixing chamber, the combustion chamber was made more spherical while being shortened from 6 to 1-foot in length, and the connection to the nozzle was made cone shaped. The resultant 1.5 ton chamber operated at a combustion pressure of 1.52 MPa (220 psi). Thiel's 1.5 ton chamber was then scaled up to a 4.5 ton motor by arranging three injection heads above the combustion chamber. By 1939, eighteen injection heads in two concentric circles at the head of the 3 mm (0.12 in) thick sheet-steel chamber, were used to make the 25 ton motor. The warhead was a source of trouble. The explosive used was amatol 60/40 detonated by an electric contact fuze. Amatol had the advantage of stability, and the warhead was protected by a thick layer of glass wool, but even so it could still explode during the re-entry phase. The warhead weighed 975 kilograms (2,150 lb) and contained 910 kilograms (2,010 lb) of explosive. The warhead's explosive percentage by weight was 93%, a very high portion compared to other types of munitions. A protective layer of glass wool was also used for the fuel tanks to prevent the A-4 from forming ice, a problem which plagued other early ballistic missiles such as the balloon tank-design SM-65 Atlas which entered US service in 1959. The tanks held 4,173 kilograms (9,200 lb) of ethyl alcohol and 5,553 kilograms (12,242 lb) of oxygen.
The V-2 was guided by four external rudders on the tail fins, and four internal graphite vanes in the jet stream at the exit of the motor. These 8 control surfaces were controlled by Helmut Hölzer's analog computer, the Mischgerät, via electrical-hydraulic servomotors, based on electrical signals from the gyros. The Siemens Vertikant LEV-3 guidance system consisted of two free gyroscopes (a horizontal for pitch and a vertical with two degrees of freedom for yaw and roll) for lateral stabilization, coupled with a PIGA accelerometer, or the Walter Wolman radio control system, to control engine cutoff at a specified velocity. Other gyroscopic systems used in the A-4 included Kreiselgeräte's SG-66 and SG-70. The V-2 was launched from a pre-surveyed location, so the distance and azimuth to the target were known. Fin 1 of the missile was aligned to the target azimuth. Some later V-2s used "guide beams", radio signals transmitted from the ground, as an added input to the Mischgerät analog computer to keep the missile on course in azimuth. The flying distance was controlled by the timing of the engine cut-off, Brennschluss, ground-controlled by a Doppler system or by different types of on-board integrating accelerometers. Thus, range was a function of engine burn time, which ended when a specific velocity was achieved. Just before engine cutoff, thrust was reduced to eight tons, in an effort to avoid any water hammer problems a rapid cutoff could cause.