US3418878A - Method and means for augmenting hypervelocity flight - Google Patents

Description

Dec. 31, 1968 J. A. srRlcKLlN METHOD AND MEANS FOR AUGMENTING HYPERVELOCITY FLIGHT Filed June 2, 1967 N... wub

3,418,878 METHOD AND MEANS FOR AUGMENTING HYPERVELOCITY FLIGHT James A. Stricklin, Texas A and M University, College Station, Tex. 77840 Filed June 2, 1967, Ser. No. 643,281 8 Claims. (Cl. 89-8) ABSTRACT OF THE DISCLOSURE A process and means for augmenting hypervelocity flight of a projectile. A projectile is initially propelled at supersonic velocities through a tube containing a gaseous medium and lined with a chemically explosive propellant responsive to high temperatures and pressures. Movement of the projectile produces a high temperature and pressure shock wave in the gaseous medium which is reflected off the -propellant lining beside the projectile and detonates the lining. Detonation of the propellant will generate a high pressure gas impinged upon the aft portion of the projectile to accelerate it. As the projectile is moved down the tube, this process is continuously repeated to continuously accelerate the projectile.

This invention relates to a process and a device for accelerating a mass to high velocities.

With the advent of space exploration, the physics and dynamics of hypervelocity flight, as well as impact reactions, must be studied under simulated conditions. One mode of Study devised for this purpose is to propel a projectile or mass in a barrel or launch tube to great speeds.

Current devices propel the projectile or mass by driving it with a high pressure gas forced into the barrel. As the projectile velocity exceeds the speed of sound in the driver gas, the pressure on it begins to reduce rapidly and consequently the acceleration of the -projectile is reduced, limiting its maximum attainable velocity.

Accordingly, it is an object of this invention to propel a projectile or mass in a barrel to greater velocities than have been attainable heretofore.

Another object of this invention is to provide an acceleration tube or barrel lined with a chemically explosive propellant, which is adapted to be ignited by a high temperature and pressure shock Wave generated by the projectile as it is accelerated in the barrel, the consequent explosion of the propellant generating a driving gas for exerting pressure on the aft portion of the projectile for uniformly and continuously accelerating it.

A still further object of this invention is to provide a process for accelerating a projectile or mass, where the projectile or mass is accelerated by ying it down the barrel enclosing it, by causing a series of high pressure gas generating continuous explosions to occur beside it, thereby preventing the projectile or mass from out-distancing the driver gas, which would result in a consequent reduction of gas pressure on it, limiting its acceleration.

Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawing, wherein:

FIGURE l is a fragmentary, side view in elevation of the hypervelocity augmentation apparatus used in the present invention partly in section, and including portions illustrated schematically;

FIGURE 2 is a cross-sectional view of a slightly modied form of the apparatus; and

FIGURE 3 is a fragmentary cross-sectional view taken substantially along the plane indicated by line 3 3 of FIGURE 2.

`nitecl States Patent O rice Referring now to the drawing in detail, wherein like numerals indicate like elements throughout the several views, a hypervelocity augmentation apparatus is generally indicated in FIGURE l by the numeral 10.

The apparatus 10 includes a launch tube or barrel 12 filled with a gaseous medium 13, a standard ignition device 14, and a vacuum pump 15 for reducing friction or gas resistance in the barrel.

The ignition device 14 could be an ordnance type device to initiate a high temperature and pressure of gas 13 and consequent motion of a projectile or mass 16 in barrel 12, or preferably, could constitute a complete rst stage acceleration assembly to have accelerated the projectile 16 to a predetermined supersonic velocity before entering barrel 12.

The ignition device 14 is of standard construction and forms no part of the instant invention. For examples of suitable ignition devices, see U.S. Patent Nos. 3,126,789 and 3,148,587.

In order to increase the velocity of the projectile 16 as it moves through barrel 12, the barrel is lined with a chemically explosive propellant 18, ignitable by heat and pressure. The propellant to be used can be made from any material rated as a low or secondary chemical explosive or a high chemical explosive that can be formed into a plastic-adhesive mass, as more fully discussed hereinafter, and is capable of generating a driver gas at a high rate.

As the projectile 16 is propelled at supersonic velocities down barrel 12, it generates a shock wave or disturbance 20 in gaseous medium 13 about its nose portion 22.

Any small disturbance in a gaseous medium is propagated with the speed of sound in that medium. For example, a disturbance in still air travels outward from the source of disturbance at the speed of sound, as a spherical pressure wave. When the source of the disturbance moves with a subsonic velocity, a wave is generated which tra'vels ahead of the disturbing body and gives the fluid a chance to adjust itself to the oncoming body. However, when the disturbing body is moving at supersonic velocities, the body moves faster than the spherical waves emitted from it, yielding a curved or cone-shaped wave front with a vertex at the body. The pressure front extends out beside the body and is called a shook wave. There is a sudden change in velocity and presure intensity across a shock lwave, with a coresponding increase in temperature.

As shown in FIGUR-E l, the projectile 16 has a maximum cross-section which is smaller than the diameter of barrel 12. Consequently, shock wave 20 extends out beside the nose 22 of projectile 16, which serves as the lvertex of the Wave, and is reflected off lining 1-8 beside the nose.

The temperature and pressure across shock wave 20 is ideal for igniting propellant 16. Neglecting real gas effects, the temperature and pressure across the shock wave beside nose 22, at very high speeds, can be expressed as:

P1 sin2 B where Tlztemperature behind the shock lwave Plzpressure behind the shock wave To=temperature of the gaseous medium ahead of the projectile P0=pressure of the gaseous medium ahead of the projectile V=velocity of the projectile Ao-zspeed of sound in the gaseous medium ahead of the projectile B=angle of the shock wave (see F-IG. 1)

fy=ratio of specic heat of the gaseous medium at constant pressure to its specific heat at constant volume, or the adiabatic constant for the gaseous medium Asuming sea level conditions, and that the gaseous medium is air:

A=1l 16.9 ft./sec. To=59 F. 'y==l.4

Taking B=30 and the value of V as 20,000 ft./sec. and multiplying by 2. to account for the reiiection of the shock This shows that the temperature and pressure rise across shook wave 20 is sucient to trigger almost any type of chemically explosive propellant.

As the shock wave 20 is reflected olf propellant lining 18, it will cause the propellant to explode adjacent the aft portion 24 of projectile 16. Explosion of the propellant 18 will generate a high pressure gas impinged upon the aft portion 24 of projectile 16, to accelerate it.

As the projectile 16 moves down the barrel 12, the shoe-k wave 20 causes the lining 18 to continuously explode beside the projectile to continuously accelerate it and ily it down barrel 12. The projectile 16 is streamlined in shape, as shown in FIGURE l, so as to enable the generated high pressure gas to drive it with maximum forward thrust. The projectile 16 cannot outrun the driving gas, and its maximum attainable velocity is limited only by the length of barrel 12, and the reaction time of the explosive lining.

To insure detonation of the propellant lining 18 at the proper time so that the gas generated by the explosion acts on the aft portion 214 of projectile 16, and not behind it or in front of it, the time lapse or delay time between the triggering of the propellant and the time it explodes should be calibrated along the length of barrel 12.

For example, if a linear distance of .2 inch between the shock and the reaction of the explosive (points 17 and 19 on FIG. 1) is required to obtain proper pressure on the aft portion of the projectile, and the velocity of the projectile is 100,000 ft./sec., the reaction time must be of the order of 2 107 sec. The materials which react this fast are high explosives such as TNT. At lower speeds a less active propellant, such as gunpowder could be used. Therefore the propellant lining 18 should be varied along1 the barrel 12 to compensate for the increasing velocity of the projectile 16.

On the other hand, it may be possible to use a secondary explosive or less active propellant throughout the length of the barrel, as long as the propellant is responsive to the heat radiated ahead of the shock wave. The explosive, due to its reaction time, would explode beside the projectile and thereby exert a force on the aft portion thereof. Often, this may be desirable because high explosives such as TNT are difficult and dangerous to work with.

As an alternative or additional method for controlling the time and place of the detonation, the barrel 12 could have different size cross-sections at the various stages of travel of the projectile 16. These different size barrel sections would serve the purpose of allowing the shock wave 20 to pass around the projectile nose 22 at different speeds and would compensate for the fact that the mass rate of ow of the gaseous medium of the wave will increase with the speed of the projectile.

In lieu of varying the diameter or cross-section of barrel 12, a vacuum tank 26 can be connected to the barrel 12 for varying the density of the gaseous medium 13 in the barrel, in timed reaction to the firing of the projectile. This will also control the mass rate of flow of Wave 20 past the projectile nose 22.

FIGURES 2 and 3 illustrate a slightly modied form of the invention, which is used when it is desired to change the shape or conguration of the projectile for experimentation purposes.

As shown in FIGURES 2 and 3, the cylindrical barrel 12' has enclosed lateral extensions 2-8 and 30. A projectile 16 is provided of any desirable shape. Attached to the sides of the projectile are wing- like elements 32 and 34, corresponding in design to projectile 16, and which extend into lateral extensions 28` and 30, respectively, of barrel 12.

The top and bottom interior surfaces of lateral extensions 28 and 30 are coated with a chemically explosive propellant 18', corresponding to propellant lining 18 in FIGURE 1.

Movement of projectile 16 through barrel 12 at supersonic velocities will generate a shock wave 20' about `wing- like elements 32 and 34. The shock waves 20" will detonate propellant 1'8 in the same manner as in FIG- U'RE l, adjacent the aft portions of wing- like elements 32 and 34, for continuously accelerating projectile 16 down barrel 12.

With the process and means of the present invention, the ,problem of a shock wave building in front of the projectile with the possibility of premature detonation of the lining if the temperature and pressure of the wave is sufficiently high, is also eliminated, because the projectile does not contact the sides of the barrel, but is own down the barrel. This enables the generated wave to be disposed behind the projectile nose.

Barrel 12 or 12 may be made from a recoverable material of high structural strength to resist internal pressure, or it may be made expendable.

The process and means disclosed also has ordnance capabilities. A weapon with a propellant lined barrel as disclosed, will be capable of shooting projectiles with increased range.

While specific embodiments of my invention have been disclosed in the foregoing description, it will be understood that various modifications Within the spirit of the invention may occur to those skilled in the art. Therefore, it is intended that no limitations be placed on the invention except as defined by the scope of the appended claims.

I claim:

1. A process for accelerating a mass having a streamlined-shaped portion comprising the steps of initially propelling said mass at supersonic velocities through a tube lined with an explosive propellant and filled with a gaseous medium, said mass when passing through said gaseous medium in said lined tube generating a shock wave of suilicient temperature and pressure to initiate detonation of said propellant lining, and causing said generated shock wave to detonate said lining adjacent the aft portion of said streamlined mass, thereby providing a force on the mass to accelerate it.

2. A process in accordance with claim 1 wherein said shock wave is reflected off said propellant lining in said tube to detonate said lining adjacent the aft portion of said streamlined mass.

3. A process in accordance with claim 1 wherein said shock wave is continuously generated adjacent said mass as it moves through said tube, causing said propellant to continuously explode adjacent the aft portion of said mass to continuously accelerate it.

4. A process in accordance with claim 1 including the step of varying the mass rate of flow of said shock wave in said tube.

S. Apparatus comprising an elongated barrel having an explosive propellant lining and lled with a gaseous medium, projectile means disposed within said barrel and having a streamlined portion adjacent said barrel lining, the maximum cross-section of said streamlined portion of said projectile means being less than the inside diameter of said barrel lining, means connected to one end of said barrel for initially propelling said projectile means through the gaseous medium in said barrel at supersonic velocities, the passage of said streamlined portion of said projectile means through said gaseous medium generating a shock wave for detonating said lining, said explosive lining having a reaction time so that its detonation occurs adjacent the aft portion of the projectile, whereby said explosion will exert a force acting on the projectile means to accelerate it down said barrel.

6. Apparatus in accordance with claim 5 wherein said barrel includes a pair of opposed lateral extensions, said propellant lining coating only the interior surfaces of said extensions.

7. Apparatus in accordance with claim 6 including vacuum tank means operatively connected to said barrel for varying the density of the gaseous medium within said barrel.

6 8. Apparatus in accordance with claim 6 including pump means operatively connected to said barrel for partially evacuating said barrel to minimize frictional resistance to propulsion of said projectile means.

References Cited UNITED STATES PATENTS 484,010 10/ 1892 Haskell 89-8 3,031,933 5/1962 Kern et al. 89-8 3,126,789 3/1964 Meyer 89--8 3,357,306 12/1967 Boyd et al. 89-8 FOREIGN PATENTS 407,860 12/ 1944 Italy.

SAMUEL W. ENGLE, Primary Examiner.

Us. C1. X.R. 42-76; 89-14

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