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And so here I am in January 2013 after a 3+ year delay.....How is that even POSSIBLE?
The Aerodynamic Development of the Antiaircraft Missile "Wasserfall"
Munich, 15 March 1945
Department Head and Author: Dr. Kurzweg
Director: Dr. Hermann
PART 1: The Nature of the Task
In
the beginning of 1943, at the Aerodynamics Institute in Karlshagen, a
demand was put forth for an aerodynamically perfect antiaircraft rocket. We were given this task
to solve in a new aerodynamic way using large-scale wind tunnel measurements. The tactical purpose required a device with a diameter of about 90 cm, 9 caliber[?] long, start with zero velocity and reach three times the speed of sound at an altitude of 20 km, ground controls up to 50 km, or perhaps equipped with a homing device, and it should describe small flight deviations in order to contact the enemy plane and counter evasive maneuvers. A device that meets
these conditions must be part projectile, part airplane. But there are currently no airplanes that fly at supersonic speed.
Therefore, in the aerodynamic development of an antiaircraft rocket, we had to rely solely on the experience gained in the development of the A-4 [V-2]. Because the A-4 is the first and only rocket/missile, flying through a wide range of speeds from initial velocity of 0 m/sec to final speed of 1500 m/sec, transitioning perfectly through the speed of sound. Also, control surfaces were prior experiences [with the A-4].
In order to lose no time, the Wasserfall antiaircraft rocket incorporated the basic shape of the A-4, the external shape of the tail, and its overall arrangement. Control devices in the form of air rudders had to be developed. Some experience with that - but only in a wind tunnel - was available on a glider model, which was part of the development of the A-4 device.
The demand for narrowly curved flight - even at very high speeds - required the attachment of wings in order to achieve the required lifting forces. The four control surfaces, which are arranged in two mutually perpendicular planes, has - unlike the usual plane shape - a symmetrical cross wing structure attached to the body to allow for a quick pivoting of the rocket in all directions. The
last thought led temporarily to investigate a basic body which would have been
surrounded concentrically by a circular
airfoil, that would have been able to slightly tilt the rocket. The very high
drag closed this issue after the first use of the wind tunnel measurements.
[This particular portion of the German text was very difficult to translate, and some words were not even found in my German dictionary. This was my "best guess" - MFW]
The
antiaircraft rocket should be based on static tests loaded to a load factor of 12
at an empty weight of ~1.5 tons, which must not be even slightly higher than
that of the aircraft to be attacked. The load factor of each type are shown in
the following table:
Type: Load Factor:
Fighters
- Dive Bomber 6 - 8
Destroyer 5 - 7
Glide bomber 3 - 5
Horizontal
Bomber and transport aircraft 2 - 3
It
was therefore for the aerodynamic shape design that a lift value of 18000 kg had to be achieved. [MFW note: 1.5 metric tons = 1500 kg. 1500 X 12 = 18000 kg]
From the calculated trajectories
with initially adopted aerodynamic coefficients, a thrust of 8 tons, a burn
time of 45 seconds and a flight time of 90 seconds
revealed that maximum dynamic pressures are reached, on the flight altitude, of the type of the
shot - or whether orthogonal
diagonally - dependent [MFW - Needs more work.]
MFW note: Definition of Load factor:
In aeronautics, the load factor is defined as the ratio of the lift of an aircraft to its weight and represents a global measure of the stress ("load") to which the structure of the aircraft is subjected:
- where:
n = Load factor
L = Lift
W = Weight
