US2972859A - Rocket motors - Google Patents

Description

Feb. 28, 1961 F. J. PORCHER ROCKET MOTORS Filed Feb. 11, 1959 1 m 4 M WM \w SMWWW .mP A w mm; Na d w a m Y flu 8 mm o 0N 7 *3 A .NN a a X y $12 @535 F.J. PORCHER ROCKET MOTORS Feb. 28, 1961 Filed Feb. 11, 1959 IIIIIIIIII 7;;! IW

FIG. 2.

2 Sheets-Sheet 2.

INVENTOR:

Fr eder/c/r Jar es Pore/rel,

ATTORNEY$..

United States i MoTofiS Freaerick-James-Parehr;Eagaaston; niigmaagasstgnei Imperial Chemical Industries Limited, Isond'on, Eng:-

land, acbrpor'atiom of Great Britain- Firearb. 1i, 19'ss;s'"er.1 to: 1922:? Claims priority; appticanon Great-Kirstin New-25,: 1958'- 4 Claims. (e1; 66 45.6

invention is c'cincer'ned era rocket meters of the" kind in which solid propellan is This application is a" continua on-in-part'-'of-"my*afi-* plication Serial No; 641,423, filcd'Feb: 20 1957 now abandoned; v p

Long-burning rocEetniot'c'Srsemploy either-a s'lbw' burrring propellant burningradially-oi a relatively f "tb' ri-- in'g propellant burning cigarette-Wise; Limitations ma dial dimensions and difiicul t yof producing" rcpeuants having a burning rate suitable for the dimension was burning-time factors militate ags'instthe" fadial bu configuration: on theother nan narg'ec changes occurring during warning of the "s configuration are objectionablei I posed to overcome the"- latter dis cigarette-burning configuration 1n whieh sing burns fro'rn-botliends simultaneously p at the head-end of are reaper ng via int axially lo'eatetl' transfer tune-'- to the n' iidot 5 motor. B u't'here agaimother disadvzifit iri ff" the transrerfiib whieh: transfer headend to the? e-end-"of of material whie is not onl'y" capable of resisting the erosive action of the h t gas flow. Those materials which are sufliciently heat -ahd erosibn resi's tant difficlllf" f6 b'bnd to; the charge and also" their respe'cti e coeffibifi O f-e ans h are dilfere'nti The l tffctf issi'gn-ificanf-b motors have: td'be temperafnre'wydd several 1 temperatures ranging" ans-matey from arctic-to" tropi a1 conditions,- and in th'e' course omens test n thecharge frequently separates from lie-transfer t'u the'result that the charge is" liable to beigliitdfiiiiifith tio'n'ally at a surface' other'than anend face 'Acc'ording' to-the'present invention, Meeker motor comprises a solid propellant eliarg eflsecur'ed creme: tor casingand" a second-so 'd i d in. the casing" in such mariner as to pre A flow" ofpro'p'ellant over are outer" suifafc 0nd charge betwee saidsurfaceand thecasingj said'sec on'd charge beingjspac'e'djfrom the first-mentionedc h'ar "a towards the rear'end'of the niotor'whereby" the' adjacent endlsurfaces ofthetwo charges are spacedapart eachother, said adjacent endfsurfacesbe'ingfsilrfaces'f at which the hargsstsurnwhen ignited; ije. ignition ena surfaces, each charge having" that" part of its-surraeee'e posed to the except th ghi'tioncndsurf ce, c6vere by ignition-preventing means; for

Patented Feb. 28, 1 9.61

which pressurises' the end of the charge opposite to it's ignitionend is substantially static gas, the flow path for thesecond charge being. by way of a clearance between the'transfer tube and wall of said passage, the transfer tube and motor casing'being connected rearwardly of the second charge by a gas-tight joint.

In one embodiment of the invention, two propellant charges are employed in axial alignment within the motor casing, and are spaced apart. 1 In part of the space between adjacent ends of the two charges (which are the ignition end surfaces) there is disposed an ignition means which when fired ignites substantially simultaneously both the ignition end" surfaces. The second or rear charge has a bore through which extends a gas transfer tube, the said tube serving to convey all the hot gases" from both charges to the atmosphere external to the rocketthrough an aperture in the rear end wall of thecasing". The two charges are; secured to" the end walls of thecasing at their respective forward and rearw'ardends and-the securing means thus remain operaave substantiallythroughout the burning period. Moreover; the'transfer tube-is secured to the wall of the aper tureiri a gas-tight manner, and'isthe sole exit for the hot area so that all the gases from bothportions' of the chargef'afe caused to now through thefe'r tire length off thetube'and escape therefromo'nly via the motor nozzle;

The second charge is supported" against differential as-pressure theends of the charge by reason of the fact that some propellant gas initially flows through the clearance between the transfer tube and charge into a space behind'the charge where it remains as substan ti'ally static gas in contact with the rear end'thereof.

The forwardcharge may be supportedagainstdiifer entialgaspr'essure in the same way, ize. by the use of a transfer tube-to duct the propellant gasto the end of the ch'argeremote'f ror'n' its ignitionend; Preferably, however the forward charge is solid throughout and the pro-' pella'ntgas-flow to support it is through an annular clear auce between the outer surface of the charge" and the inner surface of-the motor casing. To enable the gas 'to have access to the forward end of this charge the means supporting. the charge in the casing is provided with a passageway to let the gas through.

A racket motor in accordance with the invention has several advantages over hitherto proposed rocket motors. For example, bonding of the charge to the transfer tube and the difficulty of ensuring that the bond remains good after the temperature cycle test are avoided. Moreover,

since all the hot gases must pass through the transfer tube, and there isno continuous flow of hot gases through the space betw'eenthecharge andthe casing or the space between thecharge andthe -transfer tube, the"normal"in'-' Figure 2 is a similar section of the nozzle end of the motor.

The nozzle is connected to the transfer tube shown in Figure 1 either directly or by means of an extension of the transfer tube or by a separate blast tube (not shown).

Referring now to Figure l, the numeral 1 indicates a cylindrical motor casing having forward and rear end closures Z, 3 secured thereto by screws 4. Disposed with-- inthe casing 1 at the forward end is a first propellant charge 5 and spaced therefrom in the axial direction towards the rear end of the casing 1 is a second charge 6, the remote ends of the two charges being spaced from their respective end closures as shown. The adjacent surfaces 7, 8 of the two charges 5 and 6 are the ignition end'surfaces and each charge is covered on all of its sur face other than the ignition end surface with ignitioninhibiting material such as cellulose acetate.

Referring now to the first charge, the inhibiting material takes the form of layers 9 and 10 and a ferrule portion 11. The ferrule 11 is provided with an annular groove 12 and the charge 5 is supported in position by means of a grain hold-back ring 13 screwed to the end closure 2, the grain hold-back ring 13 having a claw portion 14 which engages in the groove 12 in the ferrule 11.,

A shock-absorbing ring 15 is located in the groove 12 and provides a gas-tight joint between the claw portion 14 and the ferrule 11.

The grain hold-back ring 13 is designed to leave a clearance 16 between itself and the ferrule 11 and is provided with a number of circumferentially spaced holes 17. As shown, there is a small gap 18 between the outer surface of the charge 5 and the inner surface of the casing .l and the arrangement thus provides a flow path for propellant gas from the space between the charges, along the annular gap 18, through the holes 17 and clearance 16 and into the space 19 between the forward end face of the charge 5 and the end closure 2. The end closure 2 is plugged at 20 and the space 1% therefore provides a dead end for the gas flow.

The second charge 6 is also provided with layers of inhibiting material and a ferrule of inhibiting material, the

reference numerals for these parts being those employed for the corresponding parts of the first charge 5. The charge 6 is secured in position in a similar manner to the charge 5 by means of a grain hold-back ring 21, the grain hold-back ring 21 differing from the ring 13 for the charge j 5 in that it has no holes corresponding to the holes -17 A gas-tight seal 22 is interposed between the ring 21 and end closure 3 and it will thus be seen that the charge 6 is supported at its outer surface in a manner which will prevent continuous flow of gas along the gap between through the leads 29 to cause ignition of the charges 5 and 6 on the ignition end surfaces 7 and 8. The igniting means 28 soon burns away and disintegrates leaving the forward end of the transfer tube 23 open for the admission thereto of propellant gas generated in the space between the two charges. When the charges start to burn there is an initial flow of propellant gas along the annular gap 18 between the charge 5 and the casing, through the flow path described above and into the space 19. Similarly there is an initial gas flow into the space 27 behind the charge a but in this case the flow path is by way of the clearance Both charges are thereby supported at their ends remote from the ignition ends by means of substantially static gas which has negligible erosive effect on the ignition-inhibiting material.

The main bulk of the gas generated is conveyed through the transfer tube 23 towards the nozzle 30 and the position of the forward end of the transfer tube 23 is such that no erosion of the ignition-preventing material 24 in the passage in the charge 6 occurs.

As the charges continue to burn, the burning surfaces recede from one another maintaining the centre of gravity of the system in a practically constant position. Since "reference to the drawing of a rocket motor containing only two charges of propellant material. It will be appreciated, however, that the invention may be employed with three or more charges of propellant material. In

such arrangements any number of charges may be placed in the motor using the construction and arrangement described above for the second charge. That is to say the charges will be traversed through by transfer tubes and will be pressurised at the ends opposite to their ignition ends by means of static gas in the manner aforementioned.

In f'this case some of the transfer tubes will be fixed to some internal bulkhead and will not be connected directly to the nozzle but will be used to transfer gas from one chamber to another in the motor.

that the charges will be arranged in accordance with the 6 in the passage is covered with ignition-preventing ma-- terial 24 and there exists a clearance 25 between this material 24 and the transfer tube 23.

the end closure 3 and is fitted in the end closure 3 in a The transfer tube 23 passes out of the casing through 1 maximum acceptable centre of gravity change during burning for the motor as a whole, the disposition of the ignition ends of the charges being such that gas flows into a transfer tube without eroding the surface of its adjacent charges.

has a reduced cross-section at one or more positions along its length.

I claim:

1. A rocket motor comprising a casing, first and second propellant charges mounted in said casing in spaced apart relationship, a gas tight joint between said second charge and said casing whereby. passage of gas over the outer circumferential surface of said second charge is prevented, the facing surfaces of said propellant charges "constituting ignition end surfaces and the other surfaces of said charges being covered with ignition-inhibiting macasing, a gas tight joint between said transfer tube and v said casing, said passage being larger than said gas trans tween the charge 6 and end closure 3 is a dead-end for fer tube whereby gases generated in the space between said charges may flow between said gas transfer tube and said second charge to the remote end of said second charge to provide a cushion of substantially static gas to remote end of said first charge to provide a cushion of substantially static gas to equalize the pressure on said first charge, and means for igniting the ignition end surfaces of said charges substantially simultaneouslyr It will be understood The employment of more than two charges is sometimes dictated by the need to using a casing which I 2. A rocket motor as defined in claim 1, wherein said first propellant charge is located at the head end of the motor and is solid throughout, and the flow path for said first charge is by way of a gap between the charge and the casing and through a passage provided in the means by which said charge is mounted in the casing..

3. A rocket motor comprising a casing, first and second propellant charges mounted in said casing in spaced apart relationship, the facing surfaces of said propellant charges constituting ignition end surfaces and the other surfaces of said charges being covered with ignition-inhibiting material, a passage through said second charge, and a gas transfer tube extending through said passage, said passage being larger than said gas transfer tube whereby gases generated in the space between said charges may flow between said gas transfer tube and said second charge to the remote end of said second charge to provide a cushion of substantially static gas to equalize the pressure on said second charge.

remote end of said first charge to provide a cushion of substantially static gas to equalize the pressure on said first charge.-

References Cited in the file of this patent UNITED STATES PATENTS 2,206,809 Denoix July 2, 1940 2,816,721 Taylor Dec. 17, 1957 FOREIGN PATENTS 10,008 Great Britain Ian. 11, 1844

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