The value of the rocket as a weapon of war has been proved during the conflict of the past 5 years. Even with the vast amount of work that has been done on the rocket dur-ing this war, there is a great deal of work still to be done in perfecting it.

1. The accuracy has been increased by rotating the projectile. This is effected by using skew venturi. The rotations developed range between 1,000 and 1,500 r.p.m. and consi-derably reduce the deviations of the projectile due to the influence of the wind.

2. The range has been increased by using a greater weight of propellant in addition to the development of a new powder: Nitrodiglycol. This new powder is more efficient than black powder and results in greater range and less smoke formation on firing.

3. Multibarrel projectors carrying up to 42 rounds have been developed by the Germans to effect a greater rate of fire. Reloading these new projectors is carried out mechani-cally.

When these first new efforts proved sucessful, great new exertions were made on the part of the Germans to develop more effective rocket weapons: rocket-propelled depth charges, antitank weapons, antiaircraft rockets, flares and air-craft bombs with rocket propulsion were tried out; and at the peak of the research program came the radio-con-trolled long range rocket which was still under development at the end of the war in Europe.

Solid Fuel Rockets

For the purpose of this book it is not necessary to go into the original work done on the powder rocket. The following is a brief résumé on the construction of the rocket at the beginning of this war. The rocket motor consists of the combustion chamber sealed at one end and the base plate which threads into the open end of the combustion chamber. The base plate has a series of holes in it some of which are parallel to the axis of the rocket and some of which are inclined 45° to the axis.

Propellant. The propellant used at this time is the solid nitrodiglycol type. Its advantage lies in the high calorific value and smokelessness, also in the slow rate of burning. Its density is 1.5 kg/m³, which is less than black powder, but this is compensated by the higher calorific value. The range for an 8.6 cm rocket using this type of propellant is 1,200 meters. Maximum velocity is 200 m/sec with a burning time of 5 seconds. This is not considered very good performance and so the rocket is used only against low level attacks.

As long as long range is not required, powder may be used for rocket propulsion. It must, however, be remembered that powder rockets are heavy (heavy construction chamber) and that the charge weight ratio is small. An attempt might therefore be made to deve-lop powder rockets of light construction, by using some arrangements for reloading the combustion chamber so that a larger weight of propellant may be carried. This should in-crease the range. Experiments on these lines have been carried out in Germany, but it was found that in order to insure reliable operation, the constructional complications be-came very great. This reduce use of the main advantages of rockets – less weight and simple construction.

Stabilization. The foundation for the method of stabilization was the spinning shell. By placing the venturies askew to the main axis of the rocket produced a sufficient spin. This action gives rise to a gyroscope effect and tends to resist all external disturbing forces. This method has given very good results and is greatly superior to the fin stabili-zation, which is inherently subject to wind errors.

Liquid Fuel Rockets

The liquid fuel rockets are superior to pwoder rockets as regards to:

1. Weight ratio of the propellant carried.

2. Greater energy available in the liquid propellant.

Liquid Propellant. For example, when 5 gm of powder is required for an impulse of 1kg-sec, only 0.3 to 0.4 gm of hydrogen-oxygen mixture is required for the same impulse. It will been seen that there is, in the case, a vast difference in the energy content of the propellant, moreover, the density of the liquid fuels is far greater than that of powder. The time of burning is increased, greater velocity is reached, and altogether the advan-tage lies in much lighter construction, i.e., dead-weight of the rocket, since the fuel and oxygen containers can be made of thin steel sheet. The combustion chamber also beco-mes lighter.

However, the load on the combustion chamber becomes a problem, because of the grea-ter energy and therefore higher temperatures; but this problem was solved. Combustion temperatures for powder rockets are approximately 980° to 1,000°; they are 3,000° to 4,000° for oxygen-hydrogen moxture, and in addition there is the boiling point of the mix-ture, the boiling points of hydrogen and oxygen being –253° and –183° respectively. These temperatur make severe demands on the material, and it is necessary to look for new alloys which can withstand these demands.

It is, of course, possible to consider other fuels than a hydrogen-oxygen mixture, e.g., petrol, benzol, methly, alcohol, petroleum, spirit, etc., together with liquid oxygen. These fuel have the advantage of a high boiling point and do not require special materials for the tanks; these are only needed for the oxygen.

Fuel Tanks. For the hydrogen and oxygen containers, for example, it is possible to use an alloyed steel, covered with a thin lead coating; if the rocket is to be used only once. At low temperatures (–183° to – 253°), all metals except copper become hard and brittle; however, copper remains ductile even down to such temperatures, and is therefore the best material to use for the fuel tanks.

The containers for liquid fuels at temperatures lower than –160° are best made spherical (e.g., V-1), since this form offers the greatest strenght: They must be insulated, but this offers no difficulties.