US2937493A

US2937493A - Rocket propellant igniter

Info

Publication number: US2937493A
Application number: US490760A
Authority: US
Inventors: Barnet R Adelman
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1955-02-28
Filing date: 1955-02-28
Publication date: 1960-05-24
Anticipated expiration: 1977-05-24

Description

May 24, 1960 B. R. ADELMAN 2,937,493

ROCKET PROPELLANT IGNITER Filed Feb. 28, 1955 FIG. 2.

INVENTOR. B.R.ADELMAN BY #W M ATTORNEYS ROCKET PROPELLANT IGNITER Barnet R. Adelman, Waco, Tex., assignor to Phillips Petroleum Company, a corporation of Delaware Filed Feb. 28, 1955, Ser. No. 490,760

5 Claims. (Cl. 60'-35.6)

This invention relates to the ignition of a solid rocket propellant. In one of its aspects it relates to *an improved method and apparatus for the ignition of an' internal-external burning propellant grain.

Solid propellant grains arev formed in a variety of shapes and sizes such as cylinders, boards and tubes. The tubular propellant grains are usually burned on the inside and the outside simultaneously with only the end's'being restricted. With the increased burning area provided in this configuration of propellant charge, ignition of the entire surface has been diflicult to obtain and it is desirable that the entire exposed surface be ignited in orderfor United StatcsPatent o" Recently it has been discovered that superior solid propellant mixtures are obtained comprising a major proportion of a solid oxidant such as ammonium nitrate or ammonium perchlorate and a minor proportion of a rubb nf der ma e ial such a a. cop l m of a conjugated diene and a vinylpyridine or other substituted heterocyclic nitrogen base compound, which after incorporation is cured by a quaternization reaction or a vulcanization reaction. Solid propellant mixtures of this nature and a process for their production are disclosed and claimed in copending application Serial No. 284,447, filed April 25, 1952, by W. B. Reynolds and J. E. Pritchard.

The difficulty encountered in the ignition of an internalexternal burning charge is in obtaining uniform ignition ofthe periphery of the charge. This difiiculty does not occur in the case of an external burning charge because the gases are forced to pass over the periphery of the charge because there is no other place for the hot gases to go. This is also true in the case of an internal burning charge. It is different, however, in the case of an internal-external burning charge because the gases tend to pass through the center opening rather than to take the more devious path around the periphery of the charge.

It is an object of this invention to provide an improved method for the ignition of an internal-external burning propellant grain.

It is also an object of this invention to provide an improved igniter for the ignition of an internal-external burning propellant grain.

It is an object of this invention to provide an igniter which is capable of directing hot gases and burning particles over the entire area of an internal-external burning propellant grain so as to provide instantaneous ignition of the entire exposed area of the propellant grain.

It is a further object of this invention to provide a rocket motor utilizing an internal-external propellant 2,937,493 Patented May 24, 196i) ice.

tained.

Other and further objects and advantages will be apparent to one skilled in the art upon study of the following description of the invention including the attached drawing wherein:

Figure l is a schematic sectional elevation of a rocket motor illustrating a preferred embodiment of the invention, and

Figure 2 is a sectional elevation of a rocket motor illustrating a modification of the invention.

Broadly speaking, the invention provides an igniter comprising a cylindrical cup having positioned therein a conical cup whose open base is substantially parallel to the opening of the cylindrical cup. Both cups aresub stantially filled with an easily ignitable material such as black powder, or a suitable pyrotechnic .composition' The igniter is positioned in the combustion chamber, spaced from one end of the propellant charge and centrally located with respect to the cross sectional dimensions of the combustion chamber so that upon ignition the cone shaped cup directs hot gases and burning particles down through the center opening of the propellant grain and the cone shaped configuration of'the inner cup deflects burning particles and hot gases evolved from the cylindrical cup so that these burning particles and hot gases pass over and around the outside of the propellant place the rocket motor is hermetically sealed by the die:

phragm so as to avoid deterioration of the propellant charge and in the second place the diaphragm seals combustion gases in the combustion chamber, upon ignition, so that optimum operation pressure is quickly attained. Pressure favors the combustion rate of a propellant charge comprising ammonium nitrate and a rubbery binder material. Therefore, the sealed combustion chamber attains maximum rate of combustion almost immediately when ignition is obtained.

Referring now to the drawing and particularly to Figure 1, a rocket motor is comprised of casing 10 having exhaust nozzle 11 positioned at one end and closure member 12 attached to the other end by threaded connection 13. Tubular propellant charge 14 is positioned in combustion chamber 15 and maintained in position by compression springs 16 operating against shoulders 17. The charge is restricted at each end by

plates

18 and 19 and centrally positioned by

spiders

21 and 22 which are projections from

plates

18 and 19. Frangible disk 23 acts as a closure for exhaust nozzle 11 and also supports igniter 24 comprised of cylindrical cup 25 and conical 'cup 26. Ignition wire 27 is imbedded in igniter 24 and connected to a circuit containing a source of electrical potential (not shown). Cylindrical igniter cup 25 and conical igniter cup 26 are made from light material, preferably fusible metal, plastic material or paper material such as cardboard.

In Figure 2 is shown a modification of the rocketmotor of Figure 1 and like numerals refer to like members whenever possible. In this modification exhaust nozzle 11 is secured to casing 10 by threaded connection 13a. Igniter 24 is secured to the closed end portion 12a. Spring 16a is shown as a single compression spring, however, a plurality of smaller springs can be employed as in Figure 1.

In both Figures 1 and 2 the conical cup 26 is adapted so as to deflect burning particles and hot gases from cylindrical cup 25 around the periphery of the tubular propellant grain 14 and at the same time to direct buming particles and hot gases through the center opening of propellant grain 14.

It is preferred that the hollow solid angle of the conical cup be such that the inner conical surface of rotation confining the ignition products of the ignited material from the outer cylindrical cup has a diameter substantially equal to or slightly less than the diameter of the end of the grain at the point of intersection with the grain. In most cases the intervening distance between the igniter cup and the end of the grain is fixed and the hollow solid angle of the cup is constructed accordingly, however, it is possible to vary the distance at which the igniter cup is placed from the grain in order to achieve the desired result.

Reasonable variations and modifications are possible within the scope of the disclosure of the present invention, the essence of which is the provision of an igniter for a tubular solid rocket grain comprising a container substantially filled with ignition material and having positioned therein deflecting means adapted so as to direct a portion of the ignition products to the periphery of the grain and to direct a portion of the ignition products to the perforation of the grain.

That which is claimed is:

1. An igniter for an internal-external burning propellant grain comprising a cylindrical container means having one open end and being substantially filled with an ignition material; means embedded in said igniter material in said container and adapted to direct a portion of ignition products to the internal surface of said grain and the remaining portion of ignition products to the external surface of said grain; and means for igniting said ignition material.

2. An igniter for an internal-external burning propellant grain which comprises a cylindrical cup member; a conical cup member positioned in said cylindrical cup with its open base substantially parallel with the cylindrical cup opening; an easily ignitable material substantially filling both of said cups; and means to simultaneously ignite the material in both cups.

3. In a rocket motor comprising a combustion chamher having an exhaust nozzle, an internal-external burning propellant positioned in said combustion chamber, exhaust nozzle closure means closing said nozzle and adapted so as to fail at less than combustion chamber operating pressure, the improvement comprising a propellant igniter positioned in said combustion chamber comprising a cylindrical cup spaced from said propellant with the open end of said cup facing said propellant, a conical cup positioned in said cylindrical cup with its open base substantially parallel with the open end of said cylindrical cup, an easily ignitable material substantially filling both of said cups; and means for igniting said propellant igniter.

4. In a rocket motor comprising a combustion chamber having an exhaust nozzle and an internal-external burning propellant comprising ammonium nitrate oxidant, conjugated diene-vinylpyridine copolymer binder, and a burning rate catalyst, positioned in said combustion chamber, the improvement comprising an igniter comprising a cylindrical cup, a conical cup positioned in said cylindrical cup so that the open base of said conical cup is substantially parallel with the open end of said cylindrical cup, both of said cups being substantially filled with an easily ignitable material, said igniter being positioned in said combustion chamber with the open ends of said cups facing said propellant and spaced from said propellant so that the conical surface of rotation defining a projection of the hollow solid angle of the conical cup has a diameter substantially equal to the diameter of the propellant at the point of intersection with the propellant; and means for igniting said igniter.

5. An igniter for an internal-external burning propellant grain which comprises a cylindrical cup member; a conical, fusible material cup member positioned within the cylindrical cup member and having a hollow solid angle such that a projection of the inner conical surface of rotation of said angle has a diameter substantially equal to the diameter of the propellant grain at the point of intersection with the propellant grain; an easily ignitible material substantially filling both of said cups; and means to simultaneously ignite the material in both cups.

References Cited in the file of this patent UNITED STATES PATENTS 2,685,837 Sage et a1. Aug. 10, 1954 who