US3404532A - Self-sealing through-nozzle transfer system - Google Patents

Description

1968 M- A. OLSTEIN SELF-SEALING THROUGHNOZZLE TRANSFER SYSTEM Filed April 28, 1967 TOR United States Patent 3,404,532 SELF-SEALING THROUGH-NOZZLE TRANSFER SYSTEM Myron A. Olstein, Springfield, Va., assignor to the United States of America as represented by the Secretary of the Army Filed Apr. 28, 1967, Ser. No. 635,963 6 Claims. (Cl. 60--256) ABSTRACT OF THE DISCLOSURE A self-sealing system for transferring a charge through a nozzle into a sealed rocket motor, where after the charge is transferred, there will be no significant gas flow through the motor ignition channels.

The invention relates to a self-sealing through-nozzle transfer system and more particularly to a self-sealing through-nozzle transfer system for use with single nozzle rocket motors for boosted artillery projectiles.

In the past, one of the methods used to extend the range of artillery ammunitions was by the addition of a rocket motor thereto. This type of ammunition was then called Boosted Artillery Projectile or as hereinafter referred to as BAP. In nearly every case, optimization of BAPs requires a delay in the ignition of the rocket motor. In use, the delay element is initiated in the gun tube and, at the predetermined time after exit therefrom, it ignites the rocket motor. The ignition delay system serves two functions, they are, preventing the rocket motor from igniting in the gun tube and igniting the rocket motor at a predetermined time after muzzle exit.

Ignition delay system can be of two types, one which is retained for the entire flight of the projectile and one which is discarded upon rocket motor ignition.

Previous retained delay systems have used springloaded ball seals and were centrally located. However, the ball seal arrangement is incapable of the reliability required of BAPs and the central location of the delay element requires multiple nozzles which results in increased cost.

Discarding delay systems have proven to be highly successful; however, due to the fact that it is discarded during flight, the falling delay constitutes a hazard for friendly troops. In larger BAPs where the delay element is heavier, the discarded delay may be lethal to friendly troops.

The invention provides a self-sealing system for transferring a charge through a nozzle into a sealed rocket motor. The system is called self-sealing because, after the charge is transferred, the channels are essentially sealed i.e., there will be no significant gas flow through the channels. Thus, while the acceptor or receiver of the charge transferred must be a rocket motor utilizing the aforementioned nozzle, the donor can be a spin motor, another main rocket motor or an ignition delay.

It is therefore the object of the present invention to provide a self-sealing through-nozzle transfer system which expels only a light weight plastic nozzle closure.

The above objects as well as others together with the benefits and advantages of the invention will be apparent upon reference to the detailed description set forth below, particularly when taken in conjunction with the drawings annexed hereto in which:

FIG. 1 illustrates a partial sectional view of the invention.

FIG. 2 illustrates a view as taken along lines 2-2 of FIG. 1.

As seen in the drawings a BAP rocket motor 10, utilizing a delay system, is housed in a metallic motor body 12. The metallic motor body 12 also houses solid propellant 3,404,532 Patented Oct. 8, 1968 grain 14 which is adjacent to the nozzle plate insulation 16 and has an inhibitor 15, which could be ethyl cellulose, cellulose acetate, or the like, separating said grain 14 from said body 12. Adjacent to the nozzle plate insulation 16 is a nozzle insert 18 having a bell-mouth nozzle 20 extending therethrough. The bell-mouth nozzle 20 contains the rocket igniter 22 therein. Adjacent to the end of the bell-mouth nozzle 20 is a nozzle closure 24 which is made of a light weight plastic and has a seal means 26 located therein. Located on either side of the bell-mouth nozzle 20 are two pyrotechnic delay columns 28 and 30. These columns 28 and 30 have igniters 32 and 34 abutting, respectively, at their ends.'These igniters 32 and 34 abut ignition channels 36 and 38, respectively.

In operation, the gun gases ignite the pyrotechnic delay columns 28 and 30. The nozzle closure 24 prevents early ignition of the solid grain propellant 14. After the delay columns 28 and 30 have burned for the predetermined length of time, the delay column igniters 32 and 34 are ignited. Since the consumed pyrotechnic material forms a hard slag, the ignition charge travels through the ignition channels 36 and 38, thereby igniting the rocket igniter 22. This causes the nozzle closure 24 to be expelled and ignites the solid propellant grain 14.

This ignition system can only be used in conjunction with a particular type of bell-mouth nozzle. In normal nozzles (either conical, bell-mouth or contour), the exhaust gas flow remains attached to the nozzle walls. If this type of nozzle were used, the ignition channel exits 36 and 38 would cause a flow disturbance which would result in a severe decrease of specific impulse. For the ignition system to function properly, the gas must detach at the nozzle throat 40 and reattach downstream from the ignition channel exits 36 and 38. This is accomplished by having the expansion angle exceed the Prandtl-Meyer angle (see diagram below).

Prandtl-Heyen Required Angle Angle However, if the expansion angle is made too much larger than the Prandtl-Meyer angle the gases will impinge (rather than reattach) downstream of the channel exits and result in a loss of specific impulse. For a chamber pressure of 1000 p.s.i. an expansion angle 5 greater than the Prandtl-Meyer angle resulted in negligible loss of specific impulse. For higher pressures, a larger angular increment will be required; for lower pressures, a smaller angular increment will be required.

The nozzle required for this system is designed in the following manner:

(a) The entrance section is designed in the normal manner.

(b) The nozzle throat has a flat section 44 approximately twice as long as is normally provided (.030 inch min. for a flow rate of .2 lbs/sec.) and a sharp corner 46 on the expansion or exit side of the throat.

(c) The expansion angle must exceed the Prandtl- Meyer angle.

(d) The remainder of the expansion section downstream of the channel exits is designed in the normal manner using the method of characteristics.

The following benefits accrue from the use of this selfsealing through-nozzle transfer ignition delay system:

(9.) Use of this system provides an ignition delay which expels only a nozzle closure which can be fabricated from a lightweight plastic.

(b) Use of this system provides a retained delay system which can be used with a single nozzle rocket motor.

3 (e) Since the exhaust gas flow separates at'the nozzlethroat, more eflicient nozzling at the temperature extremes (+140 F. to -65 F.) is obtained since the exhaust gases will form their own optimum envelope. (d) The large flat at the nozzle throat permits cheaper and more reliable control of the nozzlethroat size during production. Obviously many modificationsand variations of the present invention are possible in light of the above teachings. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

I claim: 1. In a single nozzle rocket motor, including a metallic motor body, a solid propellant grain housed in said body, insulation means adjacent said propellant grain, and a self-sealing through-nozzle transfer system adjacent said insulation means, the improvement wherein said self-sealing through-nozzle transfer system includes a nozzle insert adjacent said insulation means, a bell-mouth nozzle contained within said nozzle insert having one end adjacent said propellant grain, a nozzle closure adjacent the other end of said bellmouth nozzle, a pair of delay columns adjacent said nozzle insert perpendicular to said bell-mouth nozzle, a pair of igniting means adjacent said pair of delay columns on the side towards the propellant grain, and a pair of ignition channels extending from the delay columns to the bell-mouth nozzle,

:said nozzle closure is held inplace. by a seal means.

4. A system of the type described in claim 1 wherein the expansion angle of said bell-mouth nozzle exceeds the Prandtl-Meyer angle.

5. A system of the type described in claim 4 wherein the bell-mouth nozzle has a nozzle throat, said. nozzle throat having a fiat section.

6. A system of the type described in claim 5 wherein said nozzle throat has an ignition channel exit side, said ignition channel eXitside having a sharp corner, thereon.

References Cited UNITED STATES PATENTS 2,681,619 6/1954 Chandler -5. 225 2,989,844 6/1961 Alden et al. 60-39 .82 XR 3,251,267 5/1966 Hauser et al. 60-256 XR CARLTON R. CROYLE, Primary Examiner.

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