US3545212A

US3545212A - Spindle-shaped supersonic projectile with additional propulsion by sternfiring

Info

Publication number: US3545212A
Application number: US690539A
Authority: US
Inventors: Gunter Ludwig
Original assignee: Dynamit Nobel AG
Current assignee: Dynamit Nobel AG
Priority date: 1966-12-15
Filing date: 1967-12-14
Publication date: 1970-12-08
Anticipated expiration: 1987-12-08
Also published as: SE315533B; FR1552302A; DE1578225A1; CH477668A; GB1173098A

Description

Dec. 8, 197 0 e. LUDWIG 3,545,212 SPINDLESHAPED SUPERSONIC PROJECTILE WITH ADDITIONAL PROPULSION BY STERN-FIRING Filed Dec. 14, 1967 V W, 4% MA.

' ,drrok/vers United States Patent Office 3,545,212 SPINDLE-SHAPED SUPERSONIC PROJECTILE WITH ADDITIONAL PROPULSION BY STERN- FIRING Giinter Ludwig, Kiel, Germany, assignor to Dynamit Nobel Aktiengesellschaft, Troisdorf, Bezirk Cologne, Germany Filed Dec. 14, 1967, Ser. No. 690,539 Claims priority, application Switzerland, Dec. 16, 1966, 18,132/ 66 Int. Cl. F02k 7/10 US. Cl. 60-270 1 Claim ABSTRACT OF THE DISCLOSURE A supersonic projectile capable of driving through external combustion along its aft surfaces comprising a spindle-shaped body having a forward section, an aft section, and a conical enlargement section located between the forward and aft sections, each of the forward and aft sections being defined by the revolution of a slightly curved line segment so as to present both a pointed forward end and a pointed aft end and ends of greatest diameter for each of the forward and aft sections. Fuel exit openings are provided at the largest end of the forward section immediately upstream from the conical enlargement section whereby, in addition to the compression shock emanating from the pointed forward end, a second, weaker oblique shock-wave is produced by reason of the conical enlargement section.

Supersonic projectiles have been known which have a spindle-shaped body pointed in the front and rear and which, by combustion of a sufficiently rapidly burning fuel in the area of the largest diameter of the projectile, will receive an additional drive. The largest diameter of the projectile will therefore be located at the contact area of lines extending parallel to the longitudinal axis of said projectile. In the case of this additional drive known as a tail heating or external combustion, the difficulty is in the ignition of the fuel. Customarily, a liquid, a liqiud gas or a highly compressed gas is used as a fuel which emerges from openings distributed along the periphery on or behind the largest diameter of the spindle-shaped body and which burns with the aid of the oxygen of the air. Such a tail heating or external combustion will be come effective and economical only when the relative speed between the air and the supersonic projectile amounts to at least 3 Mach. The fuel ignition speed therefore must be correspondingly high so that the flame will not be broken in the supersonic current. There are fuels which will fulfill this condition, for example, aluminum borohydride. Such fuels, however, are spontaneously flammable in air and therefore their handling and technical exploitation is difficult. A housing in, for example, projectiles that are to be fired from a tube, does not seem to be realizable as yet for the time being. In the case of supersonic projectiles, the so-called wave resistance will occur in addition to the resistances brought about behind the projectile by friction at the surface of the projectile and the formation of eddies, which wave resistance is brought about through the system of condensation as a result of compression shocks and expansion waves developing around the flying body. In the compression shocks, the density of the surrounding air changes irregularly while it steadily decreases in the diverging fields of expansion waves. The impulse delivered to the surrounding air for the change in density corresponds to the wave resistance. In order to keep these losses as small as possible, it has been known to develop supersonic projectiles, so called minimum bodies. These 3,545,212 Patented Dec. 8, 1970 have a minimum wave resistance since the diverging expansion waves will reduce as strongly as possible the compression shocks on the basis of a corresponding profile shape, by interference with an increasing lateral distance from the body of the projectile, and will counteract in this manner, an expansion of the wave emanating from the projectile.

The inventtion will make even slowly igniting and less dangerous fuels burn continuously in the supersonic stream with technical means on the body of the projectile and will thus make them usable for the additional drive of supersonic projectiles.

The invention relates to a spindle-shaped supersonic projectile capable of drive through tail heating or external combustion along its aft surfaces, with a front part of the projectile converging into a pointed forward end a rear part of the projectile tapering afterwards, a conical enlargement between said forward and rear parts, and fuel exit openings at the enlargement which comprises the largest diameter of the projectile. This conical enlargement in addition to the compression shock emanating from the pointed forward end of the projectile, produces a second, weaker oblique shock-wave in the area of the fuel exit openings, which on the basis of the compression taking place during this time and on the basis of the increase in the temperature of the air, will maintain in an effective manner the combustion of the customary fuels, for example, hydrogen, in the case of a supersonic stream. The magnitude of this second compression shock at the same time is dependent on the angle and the diameter of the conic enlargement.

In a practical development of the invention provision has been made according to the invention to continue the contour of the tail of the projectile without interruption downstream from the outside edge of the conical enlargement. For this purpose, the tail end of the projectile can be developed for example in a known manner likewise as a minimum body. However, in view of the effect intended with the drive, it will be more advantageous if according to a further proposal of the invention the contour of the tail part of the projectile tapers toward the end of the projectile in such a manner as the volume of combustion gases increases in consequence of the continuing combustion of the fuel toward the end of the projectile and expansion of the combustion gases, so that the cross sectional size of the space occupied by the tail end of the projectile and the production gases will come as close as possible to the largest cross section of the projectile beyond the longitudinal extent of the tail end of the projectile. Such a development will guarantee optimum conditions concerning an additional acceleration and stabilization of the projectile since the combustion gases are, so to speak, in the shadow of the projectile and consequently will be influenced to a minimum measure by the surrounding air, so that the pressure forces exerted by the combustion gases on the tail end of the projectile, the axial component of which causes the acceleration and the radial component of which causes the stabilization of the projectile, will reach their greatest possible value.

Further objects will be apparent from the following description whenconsidered in connection with the accompanying drawing which is a cross-section of the projectile. The supersonic projectile shown in longitudinal section has a spindle-shaped body which is pointed fore and aft. It has been developed as a forward section 10 in its front part and it produces the compression shock 1 with its point. In the area of the largest diameter of the forward section fuel exit openings 2 are provided and are divided evenly over the periphery. The area of largest diameter is where tangent lines on the projectile run at least approximately parallel to the axis of the projectile.

Downstream from the exit opening 2, the projectile has the conical enlargement 3, which produces a smaller second compression shock 4. The tail end or aft section of the projectile coverages directly from the outside edge of the conical enlargement 3 and is developed by the revolution of a slightly curved line segment similar to the forward section of the projectile. Also, the tail part of the projectile may be continued in such a manner to the combustion process that optimum conditions will be achieved with regard to the thrust and stabilization of the projectile.

The direction and size of the curvature of the after section 5 contour will be selected such that the crosssectional size of the space occupied by the aft section of the projectile and the combustion gases will come as close as possible to the largest cross-section of the projectile via the longitudinal extent of the aft section of said projectile. Accordingly, in the case of a quickly burning fuel, the tail part of the projectile will have to taper even more strongly directly behind the conical enlargement 3 than in the case of a slowly burning fuel.

The conical enlargement 3 may be adapted easily to the pertinent needs through a corresponding dimensioning of the angle and of the outside diameter in order to produce a second compression shock 4 which will suflice for the permanent ignition of the pertinent fuel, which shock will not bring about more resistance than is absolutely necessary. For example, with a conical surface of 28 degrees in the case of an air flow of 3 Mach, hydrogen can be brought to continuous combustion.

I claim:

1. A supersonic projectile capable of drive through external combustion along its aft surfaces, comprising: a spindle-shaped body having a forward section; and aft section; and a conical enlargement section located between said forward and aft sections; said forward section being defined by the revolution of a slightly curved first line segment so as to present a pointed forward end and an end of largest diameter for said forward section downstream of said pointed forward end; fuel exit openings provided along said largest diameter end; said conical enlargement section being defined by a conical segment diverging downstream directly from said exit openings, the divergent end of said conical segment defining the outermost protrusion on said body; and said aft section, which is defined by the revolution of a slightly curved second line segment so as to present a pointed aft end, converging downstream from said divergent end of said conical segment to said pointed aft end whereby, in addition to the compression shock emanating from said pointed forward end, a second, weaker oblique shock-wave is produced by reason of said conical enlargement section.

References Cited UNITED STATES PATENTS 3,008,669 11/1961 Tanczos -270 3,074,668 1/ 1963 Frenzl 60-270 3,363,421 1/ 1968 Ferri 60-270 DOUGLAS HART, Primary Examiner