US3257804A

US3257804A - Frangible booster motor

Info

Publication number: US3257804A
Application number: US342571A
Authority: US
Inventors: Paul E Thomas; Giles P Wetherill
Original assignee: Individual
Current assignee: Individual
Priority date: 1964-02-04
Filing date: 1964-02-04
Publication date: 1966-06-28
Anticipated expiration: 1983-06-28

Description

June 28, 1966 p E. THoMAs ETAL 3357,804

FRANGIBLE BOOSTER MOTOR Filed Feb. 4, 1964 Paul E. Thomas Giles R Wefherill.

INVENToRs. W WI. By J.

JW M W c. M

` 3,257,804 Patented ,June 28,l 1966 3,257,804 FRANGIBLE BOOSTER MOTOR Paul E. Thomas and Giles P. Wetherill, Huntsville, Ala., assignors to the United States of America as represented by the Secretary of the Army Filed Feb. 4, 1964, Ser. No. 342,571 Claims. (Cl. 60-35.6)

The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

The present invention relates to a means for disposing of a booster motor after its ejection from a rocket so as to minimize the danger to personnel' or property upon its descent to earth. In the operation of rockets or the like it is known thatiin order to obtain suficient thrust it is oftentimes necessary to use a booster which may be dropped after use. When using a conventional 'booster it has been necessary to fire the rocket in isolated geographic areas so as to prevent damage or injury caused byv the dropped booster as it returns to earth. Experiments haveindicated that a falling object with only 57 foot pounds of energy would be lethal. A freely falling booster case which may Weigh hundreds of pounds thus constitutes a hazard of formidable proportions. Much experimentation has been performed in an elfortto eliminate this hazard,`thus allowing rockets to be fired over urban or even heavily populated geographical areas.

Our invention contemplates a booster motor case which when ejected may be reduced to non-lethal fragments, that is, fragments having less than 57 foot pounds of energy. In this design, a high strength rigid type sheet explosive such as Tacot, Octol or Monite is used as an integral -part of the motor case and, as such, the sheet materially contributes to the structural strength of the booster motor. Such sheet explosives will burn rather than detonate when exposed to high temperature. The explosive' is insulated from the internal heat of the burni-ng propellant and from the external aerodynamic heating by layers of insulating material to protect the structural integrity of the material as well-as its explosive properties.

Accordingly, on object of our invention is to provide a lbooster motor which will consi-stently disintegrate into minute pieces which constitute no hazard when falling into populated areas.

Another object of our invention is to provide a frangible booster motor having approximately the same dimensions and flight characteristics as a-conventional booster motor.

Still another object of' our invention is to provide a booster motor with an explosive charge which in no way interferes with the operation or fuel capacity of a booster.

Yet another object of our invention is to provide a frangible booster motor which is relatively simple and economical to manufacture.

This invention together with other objects and advantages thereof will best be understood by reference to the following description and accompanying drawing, in which:

The single figure is a cross-sectional showing the general configuration and location of each of he layers which make up the booster motor; A

Referri-ng now to the drawing the frangible booster motor 1 comprises a body 3 having a fuel chamber cylinder 5 and a nozzle portion 7. The forward end of the cylindrically shaped fuel chamber is closed by means of a head closure plate 9. The 'body 3 is usually fabricated from a unitary sheet of steel thus forming a rigid inner liner for the booster motor. The characteristics of the steel used to fabricate the body, of course, are quite varied i-n that it must withstand a great deal of heat while yet being somewhat brittle so as to disintegrate when subjected to explosive forces.

Immedately surrounding the body 3 is an insulating layer 11 which is attached to the body and, as illustrated, conforms to the general configuration of the exterior of the motor. Insulating layer 11, which may be made of any commercially available insulating material, such as polyurethane or asbestos, is designed to prevent the intense heat caused by the firing of the booster from burning eX- plosive layer 13 which surrounds the insulating layer.

It is essential that the insulating layer be extremely effective because although the gradual application of heat will not necessari-ly explode layer 13 it will cause deterioration .or burning thus rendering the explosive layer inoperative as an explosive as well as drastically reducing its structural strength and therefore the strength of the motor itself. A film of igniter material 15 entirely surrounds layer 13 to assure instantaneous and complete ignition of the explosive upon a signal from an igniter mechanism 17. A cord or strip type igniter material may also be used to ignite the eXplosive layer. Igniter material 15 is surrounded by an exterior heat Shield 19 which also conforms to the general 'configuration of the booster motor. This shield, which may be made of any commercially available insulating material, such as polyurethane or asbestos, is provided to protect the igniter material and the explosive layer from heat generated by aerodynamic friction as the rocket passes through the atmosphere. Since the heat shield is located on the exteri'or of the explosive its characteristics must make it extremely resistant to heat while yet it must be quite frangible since its fragments may be blown clear without receiving a great deal of force from the explosive. lThe device is designed so as to locate the explosi-ve completely around and on the exterior of the main booster body so as to exert a great deal of force toward the interior. By locating the explosive on the exterior of the motor body the fragments are blown inwardly from each side of the booster. These fragments are thus vi'olently thrown together in the middle area of the booster and broken into small pieces which will float harrnlessly back to the earth.

In operation of the device, the booster motor will be attached to a rocket and will -be dropped therefrom after its fuel is expended. A timing mechanismmay be built into the igniter mechanism 17 to 'allow a lapse of time between dropping of the booster and ignition of the explosive in the booster so as to avoid interference with the flight of the rocket. Igniter mechanism 17 will then actuate the igniter film or strip whichin turn will set off explosive layer 13. The explosive layer being confined between the exterior heat Shield 19 and the body 3 will cause a uniform force upon the entire area of each of these elements thus causing them to disintegrate in small approximately equal particles which will fall harmlessly to the earth.

It will thus be seen that our invention provides a frangible booster motor which because of the use of high strength rigid type explosive is equal to conventional boosters in all essential design characteristics and yet is completely safe for firing over populated areas.

While the foregoing is a description of a preferred embodiment, the., following claims are i'ntended to include those modifications and variations that are 'within the spirit and scope of our invention.

We claim:

1. A frangible booster motor comprising: a generally cylindrically shaped body having a fuel chamber i-n one end thereof and an open nozzle at the other, a layer of heat resistant insulating material adjacent to and conforming to the configuration of said body, a layer of rigid high strength sheet explosive completely surrounding and conforming to the shape of said body and being located immediately on the exterior of said insulating layer, igniter material immediately adjacent said explosive, an exterior heat shield surrounding the device and conforming to the configuration thereof, and means for igniting said igni'ter material.

2. A device as set forth in claim 1 wherein said igniter material comprises a film completely surrounding and immediately adjacent said explosive layer.

3. A'device as set forth in claim 2 Wherein said igniter means comprises a primer cord.

4. A frangible booster motor comprsing: a generally cylindrically shaped body having a fuel Chamber and a nozzle portion, an explosive sheet completely surrounding said body and insulated from said body, and means disposed exterio-rly of said explosive sheet for igniting said explosive Sheet, said means including a film of igniter material completely surrounding and immediately ad- UNITED STATES PATENTS 2,937,595 5/1960 Margulis et al.

3,013,333 12/1961 Burke 102- 23 X 3,017,746 1/1962 Kiphart 60-356 3,017,836 1/1962 Guay 60 35.6 3,062,l42 11/1962 Breza et al. 102-23 MARK NEWMAN, Primary Examner.

C. R. CROYLE, Assistant Examiner.

Claims

1. A FRANGIBLE BOOSTER MOTOR COMPRISING: A GENERALLY CYLINDRICALLY SHAPED BODY HAVING A FUEL CHAMBER IN ONE END THEREOF AND AN OPEN NOZZLE AT THE OTHER, A LAYER OF HEAT RESISTANT INSULATING MATERIAL ADJACENT TO AND CONFORMING TO THE CONFIGURATION OF SAID BODY, A LAYER OF RIGID HIGH STRENGTH SHEET EXPLOSIVE COMPLETELY SURROUNDING AND CONFORMING TO THE SHAPE OF SAID BODY AND BEING LOCATED IMMEDIATELY ON THE EXTERIOR OF SAID INSULATING LAYER, IGNITER MATERIAL IMMEDIATELY ADJACENT SAID EXPLOSIVE, AN EXTERIOR HEAT SHIELD SURROUNDING THE DEVICE AND CONFORMING TO THE CONFIGURATION THEREOF, AND MEANS FOR IGNITING SAID IGNITER MATERIAL.