US2955415A

US2955415A - Cooled combustion chamber liner and nozzle supported in buckling modes

Info

Publication number: US2955415A
Application number: US700252A
Authority: US
Inventors: Theodore M Long
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-11-27
Filing date: 1957-11-27
Publication date: 1960-10-11
Anticipated expiration: 1977-10-11

Description

Oct. 11, 1960' T. M. LONG 2,955,415

coouzo COMBUSTION CHAMBER LINER AND NOZZLE SUPPORTED IN BUCKLING MODES 2 Sheets-Sheet 1 Filed Nov. 27, 1957 INVENTOR. J'Zeadarl ff [mfg arra VH5 Oct. 11, 1960 T. M. LONG 2,955,415

COOLED COMBUSTION CHAMBER LINER AND NOZZLE SUPPORTED IN BUCKLING MODES 2 Sheets-Sheet 2 Filed Nov. 2'7, 1957 FIG.|2

INVENTOR. Theodore M.Long

MM if? ATTORNEYS COOLED COMBUSTION CHAMBER LINER AND- V NOZZLE SUPPORTED IN BUCKLING MODES .Theodore M. Long, 40 S. Bridge St., Somerville, NJ. Filed Nov. 27', 1957, Ser. No. 700,252

13 Claims. (Cl. 60-356) This invention relates to a combustion chamber andnozzle structure to be primarily employed in a liquidcooled rocket engine.

This application is a continuation-in-part of'my pn'or application for United States Letters Patent Serial No. 292,008 filed June '5, 1952 and entitled, Combustion Chamber and Nozzle, now abandoned.

1 Bymeans of the present teachings, the parts may be made sufficiently thin so thata proper heat exchange is feasible between the coolant passages and the adjacent surfaces without weakening the assembly in a manner such that the chamber liner or nozzle will tend to collapse. Rather, by means of this invention, the parts are rigidified and strengthened against any probability of such collapse.

Moreover, the design herein contemplated serves" to strengthen the entire assembly so that the chamber jacket as well as the nozzle jacket are eifectively interconnected and supported with the adjacent nozzle and liner portions.

With this construction, the structural and cooling limi-' cations, which have previously limited the maximum size of rocket chambers, are removed. Combustion chambers and nozzles for engines of 1,000,000 pounds thrust may be operated as satisfactorily as those one-tenth that size.

This result is achieved without any sacrifice on the effective functioning of the coolant passages or space. Also, the structure permits of relative movement of the parts incident to their differential expansion under operating conditions.

Additional objects of the present invention are those of furnishing structures which may be produced with facility and with relatively low expense aside from the fact that the components of these structures may be readassembled.

With these and other objects in mind, reference is had to the attached sheet of drawings illustrating practical embodiments of the invention and in which:

- Fig. 1 is a sectional side view of a liquid cooled rocket engine combustion chamber and nozzle assembly;

' Fig. 2 is a transverse sectional view taken'along the line 22 and in the direction of the arrows as indicated, in Fig. 1; i 1 t Fig. 3 is a fragmentary sectional view in enlarged scale illustrating one of the connecting structures as'embodied in Figs. 1 and 2;

Figs. 4 to 6 are views similar to Fig. 3 but showing alternative types of structures;

Fig. 7 is a somewhat schematic view illustrative of the manner in which the jacket and liner may be formed;

Fig. 8 is a view similar to Fig. 7 but showing the arrangement of parts which is preferably employed in connection with the nozzle and its adjacent jacket; and v Figs. 9 to 12 are schematic transverse sectional views taken along the line 2-2 in Fig. 1 showing the manner in which unrestrainedliners fail. 'I'he nozzle is omitted for clarity.

2,955,415 Pa tented Oct l1, 196p In the type of rocket or similar engine here under coni struction, the combustion chamber liner is surrounded by a jacket and the nozzle is surrounded by a similar.

jacket. These parts are spaced so that a series of cooling passages are provided between them. Through thesepassages, one of the propellants of the rocket engine is" passed. This cools the chamber liner and nozzle and' prevents them from beingmelted or eroded by the come bustion gases. Normally, during operation the pressure. of this liquid propellant in these cooling passages exceedsv the pressure of the combustion gases by asconsiderable;

amount. Accordingly, the chamber liner andnozzle are under a crushing radial force which tends to collapse. them. The chamber jacket and nozzle jacket arecdn-I versely under a bursting radial force which tends .to ex.

pand and stiffen them.

Where a design such as the foregoing is employed, it is usually desirable to form the chamber liner and nozzle from relatively thin material. Thiswill serve to assure a cooling of the parts in a proper manner. However, with the liner and nozzle formed of thin stock, they would tend to be easily collapsed. By means. of the present. teachings, the chamber liner and nozzle aremechanically connected to the chamber and nozzle jacket without line terfering with the flow of the cooling propellant. More important, in these chambers the size andshape of the. coolant passages must be carefully calculated at every point to controlthe coolant velocity in order to carryaway the necessary amount of heat from the liner soas to protect itfrom distortion and burn-out.

and jacket at all points.

It is the nature .of these chambers that the amount of coolant available is definitely limited and that the pressure losses incurred in pumping the coolant at high velocities must be kept an absolute minimum as above. It should.

be understood that any improvement which permits a thinner. liner to be used is of great advantage. It is reflected by not only a saving in weight ofthe chamber,

but by a reduction in the .size and weight of many components of the'rocket. Pumps, piping, controls, fuel for the pumps are all reduced. And, since rocket performance' is very sensitive to weight, small savings at each; of these points result in large performance increases With these effects, the cooling provided in an efficiently designed-chamber is reducedto a bare minimum, so any:

margin of safety recoolant passage at that point (for the liuer'in moving-in-j wardsincreases the clearance'between it and the jacket);

Theincrease in area, in accordance with the equation of continuity, reduces the coolant velocity and this reduces the cooling at the point of inward distortion. Typically inward distortions as small as .01 inch-aresufiicient to,

initiate. burn-out. This is a self-accelerating process, for

reduced cooling causes the chamber liner to become hotter, softer and weaker; a small distortion by coolant pressure or locked-in thermal stresses leads instantly to larger distortion and failure. It is one of the two common types of failure of these nozzles and chambers, one

which has severely limited the development of large cham bersin the 50,000 pound thrust class and above.

Thus, the. designer is confronted with 'two diametrically opposite. requirements. He must first use the thinnestpossible. liner to reduce the amount ofcooling required by the liner Wall and, second, must provide a thick enough liner to properly resist thecoolant pressure so as tomaintain'. accurately the dimensions of thepassages between liner.

Since it is important from the coolingstandpoint to use as thin a liner as possible, and since thin liners are move easily distorted inward in the form of a buckle, especially in chambers :of large size, .itwill' be shown' to be.of advantage to restrain the liner. or': nozzle against buckling when this can be donein a mannerwhich avoids thermal stresses by permitting these members to undergo ditferentialexpansionin' their jacketstdue to temperature.

made: to Figs..9 to 12 which serve. to? explain the'basic structure. which must be envisioned to understand the manner in which buckling. modes of liners and nozzles.

are: restrained. The term bucklingmode? is a precise one stemmingifrom the mathematical interpretation of the failureof thin-walled cylindrical or of circular cross section-nozzle members under the effects of external pressure It is itself descriptive of a type of failure; the restraintof this typeof failure enables the thin liner or nozzle to bear higher pressure than if unrestrained and.

free to buckle.

In order to. give a definition of this conciseterminology, Fig. 9 illustrates a cylindrical chamber jacket 10 enclosing a chamber liner 11. The dotted lines represent the cylindrical liner before sufficient pressure has been applied to initiate a buckle. The solid lines, in the form ofian outline of a figure eight, represent the liner buckled in the second buckling mode. That is to say the liner has buckled in two longitudinal places which occupy'two equal 180 degree segments of the liner;

Fig; 10 shows the cross-section of a cylindrical liner buckled in the third buckling mode. The originally circular cross-section has buckled into three equal segments or lobes occupying one-third of the liner or 120 degrees of are along its length. Similarly, Fig. 11 represents the same situation, but with the linerbuckled in the fifth mode, eachbuckle or longitudinal lobe occupying onefifth of the circumference or 72 degrees ofarc.

Generally speaking, thin'members of this sort do not develop all five lobes in practice (or whatever the characteristic number may befor the particular proportions ofadefinite chamber), for very minor differences in the wall thickness arising from manufacturing tolerances result-in the liner buckling first in the thinnest area. Usually when they are inspected after buckling, only one lobe has developed as in Fig. 12, with the others occasionally being formed in their'proper place around the cylinder.

When the single or multiple lobes occupy one-fifth of the 1 circumference each, the liner is still said to have failed in the-fifth buckling mode.

The number of the mode in which an unrestrained liner will buckle under external pressure depends upon the'thickness of the liner wall, the radius, the length, the amount of support given the liner atthe ends, the mannerin which the pressure is applied to cause buckling, and the material of which it is made. The common pro portions of cylindrical combustion liners are such that these members buckle in the range of the third to the tenth mode when unrestrained. That is they are, as presently designed, so proportioned that the buckle appears-so as to occupy one-third, one-fourth, one-fifth and so on down to one-tenth of the circumference. He'retofore, designers have'simply increased the thickness of these liners or of nozzles until' they are in themselves stifi enough to resist buckling failure. This, in"accQrd-' improvement.

ance with the equations pertaining to heat transfer, makes the cooling more diflicult, limits the size of chambers, and increases the weight of the entire rocket out of all proportion to the small increase in chamber weight alone, while decreasing rocket performance to a greater degree. For these reasons, methods of decreasing liner thickness have been continually soiightibydesigners of rockets.

By contrast, the importance of the invention considered. here maybe seen. Ifiis' efitirely-unnecessary to increase the thickness of cylii'idiical linersor of circular nozzles to enable them to Withstand higher external pressures. It is only necessary to provide longitudinal means of support or restraint which hold them at equally spaced intervals in a radial directiontoa stable member such as the jacket. Equations have been verified in the laboratory and in practice which demonstrate this improvement. All that need be done is provide a number of longitudinal means of support which'is-greater by one than the natural buckling mode of the unrestrained liner or nozzle (which is determined by its shape and material). If, for example, it is desired to force a liner or nozzle to carry a higher pressure, say one which when unrestrained is weak enough to buckle inwardly in the fifth buckling mode, it is only necessary to providelongitudinal means for connectingand bracing the liner with respect to the jacket or nozzle to the nozzle jacket at six or more equally spaced intervals around the circumference thus restraining these members to a corresponding number of buckling modes. It is important that the longitudinal means be equally spaced and that they be continuous in the longitudinal direction; or very nearly so except for minor interruptions, or the improvement in strength will'not be fully attained.

When firmly supported and restrained in this manner in six places, any buckle or inward distortion can only extend over one-sixth of the circumference, when supported in seven places over only one-seventh. With the addition of.each longitudinal means for connecting and bracing the internal members, they will withstand a higher pressure." To produce larger and larger chambers it is only necessary to increase the number of longitudinal places of restraint. There are upper limits to the amount of improvement which can be obtained in this manner, for after the' instability failure of buckling is overcome, there is one fixed by the strength of the material. Nevertheless, with members shaped as they generally are in these 'chambers and nozzles and within the range of properties of the materials of which they are constructed, a worthwhile improvement may be had as noted above.

In similar fashion, the longitudinal means which connect an'cl brace the liner with respect to the jacket serve to prevent expansion of the jacket by coolant pressure by maintaining a close attachment to the liner. This is' Although the concept leads to a structure which is simple, certain precautions must be taken to obtain the First the liner or nozzle must be maintained free of inward distortion or curvature between the longitudinal means of support. As will be noted later, the nozzle throat is inwardly curved. At that point the means of support are omitted for this and other reasons. For explanation of the effect of inward curvature, assume the curvatureof'the cylindrical liner of Fig. 9' before bucklingiis called' positive in the mathematical sense. The curve inward atthe right side of the figure eight outline, where the buckle occurs, wouldbe opposite or negative, With this definition the requirement for greatest improvement-may be restated: the linermust not be negatively curved at any point. If negative curvature is pres-:

cut, the liner is already buckled and has lost strength. If the liner is flat at any point a buckle is easily started.

This should not be taken to mean the liner or a nozzle should not be formed in accordance with this invention in outwardly curved panels, between the longitudinal means of support, which have a curvature sharper than the true cylinder or true cone of these members. For example, this is the normal situation which exists in an originally cylindrical liner which is hotter than the jacket by a large amount. The liner, when much hotter, can expand to the point where it becomes larger than the jacket along the longitudinal connections. Being outwardly curved between these places, it can only continue to expand outwardly between them. In doing so, it will become more sharply curved. This is not a disadvantage. On the contrary, it is an advantage, for being more sharply curved, each panel then becomes a segment of an effectively smaller diameter cylinder between the supports which is stronger as the sharper arches of a bridge are stronger.

Second, the longitudinal panels between supports of the liner or nozzle must be free toexpand longitudinally with respect to the jackets unless they are given outward curva ture longitudinally to stiffen them. If not outwardly curved in the longitudinal direction and notfree to expand, thermal stresses in the liner or nozzle resulting from the inability to expand, can accidentally introduce a small inward deflection which is an incipient buckle. Although not a fully developed buckle in the mathematical definition of one developed in a buckling mode by external pressure, such an incipient buckle can act to start a true buckle at pressures far below that expected when thermal stresses are avoided. For this reason, the liner or nozzle must be given this freedom in the longitudinal direction to obtain the greatest resistance to distortion where the technique of controlling buckling modes is to be taken advantage of in stiffening these members.

Third, the longitudinal panels of the liners and nozzles must be jointless and continuous across the longitudinal means for connecting them to their jackets if the buckling is to be properly restrained. The unit construction is necessary to avoid mechanical joints which introduce unexpected eccentric forces from one panel to the other, thus weakening the structure. In the jointless, unit structure the adjacent panels mutually strengthen one another to the greatest degree. As an example of this, it is found in the mathematical investigation of these structures that it is impossible to accurately predict the pressure at which one will fail if made of panels connected by joints, for the joints, even when carefully made, precipitate buckling in a panel which develops the slightest eccentricity. On the other hand, the failure of the longitudinally supported jointless structure is accurately predicted for each mode of buckling, showing greater pressure resistance with the addition of each support as the mode of buckling is forced to increase.

' The improvements embodied in the jointless outwardly curved liner, properly res-trained to control buckling modes, can be most clearly seen when compared with prior structures proposed to reduce liner distortion. These prior structures have pursued two exactly opposite lines of reasoning. One line of thought has been to allow the liner to be limp and provide little or no cooling. This releases the thermal stresses, but provides none of the strength required in rocket chambers or other high density combustion chambers where cooling must be done at high pressures and must be exactly controlled. The other line of thought has been to hold the liner absolutely in place bymain force to withstand higher pressure. The main force method must then cope with thermal stresses so introduced and use a heavier liner to withstand these plus the pressure forces. Unfortunately, a thicker liner is required and this necessitates more cooling and, by the very nature of heat transfer effects, causes greater thermal stresses. This upward spiral of liner thickness has been a block to development oflarger and more efiicient controlled, the coolant being low pressure air which'may.

be lost without penalty, this has served to reduce thermal distortion alone. Such a liner will withstand no more than a few pounds per square inch pressure diiferenc'e,.for there is no curvature and no continuous structure to resist buckling mode failure. In contrast, the continuous unit liner, outwardly curved and with longitudinal means for restraint of buckling modes, makesprovision for thermal expansion in the longitudinal direction, uses thermal expansion in the circumferential direction to strengthen the structure, retains coolant without loss and enables exact control of cooling. Also, in the same weight of structure it withstands coolant pressures of several hundred pounds per square inch, permitting cooling which is of the order of one hundred times as great for severe service.

It the second situation, the liner is attached by tie rods or welds to the jacket. With this fixed mounting, differential expansion of the hot liner and cool jacket immediately distorts the liner, for each rod or weld is a focal point for a buckle. With the liner no longer truly circular, or part of a true circle, its resistance to buckling is gone. Thus, it has lost its primary source of strength, its own rigidity, and must depend upon the tie rods or welds. This is easily seen. In this connection it is suggested one employ, for purposes of visulation, a strip of thin metal which has a curved cross-section (a metal tape ruler will do) and bend it. So long as it does not buckle and lose curvature, there is considerable resistance. Once it has buckled, it becomes completely flexible. This, on a very small scale, is the strength which is lost to the incipient buckles caused by thermal stresses and rigid attachment, or more exactly to attachment improperly carried out. i A i There is a side effect which is equally unfortunate arising from tie rod attachment. The tie rods or welds used in a quilted form of attachment each present an edge to the oncoming coolant flow. The great number necessary, usually in the hundreds and (in the case of a large unit) in the thousands, double and triple the resistance to coolant flow by the eddy currents and fluidrfriction they cause. Looking through the coolant passages of a chamber using them reminds one of trying to look through a dense forest. The whole purpose of using thin liners is to reduce the cooling pressure losses by reducing the speed at which coolant must be pumped. Under the best conditions, tie rods permit little if any reduction in liner thickness due to the thermal stresses they cause and so permit little reduction in cooling. At the same time, they tremendously increase cooling pumping loss by their resistance;

Since they defeat their purpose, they are not used. This has been demonstrated time and again in practice; the larger the chamber, the greater is the difficulty with pressure losses, the greater is the difficulty with thermal stresses, and the greater is the difficulty with tie rods tearing and welds failing. Y

Again in comparison, the jointless outwardly curved liner, longitudinally attached to control buckling modes, utilizes the physical properties of the wall material to greatest advantage. Thermal effects are put to use .to strengthen the liner, rather than weaken it. Larger rocket engines and combustion chambers are easily and economically constructed simply by increasing the number'of longitudinal supports with size. Cooling pumping losses are negligibly increased for the supports are parallel not I cross-wise to the flow as with rods and are far less numerous. The other methods entirely overlook the basic principle of the failure of liners under external pressure and'seek only to cure a symptom, distortion, rather than the disease, buckling mode failure.

With the foregoing in mind and referring primarily to Figs. 1 and 2, the numeral 10 indicates the chamber jacket which encloses the chamber liner 11. The nozzle conveniently embraces a converging cone portion 12 continued in the form of a diverging cone portion 13. Surrounding this nozzle are jacket portions 14 and 15 respectivelywhich are connected to each other and to the jacket 10. As shown, the chamber liner and nozzle are spaced from the adjacent jacket portions. Accordingly passages 16 exist between

parts

10 and 11 while passages 17 intervene nozzle parts 12-13 and jacket parts 14-15. Twelve'longitudinal connections are shown between liner and jacket and between nozzle and nozzle jacket. These twelve connections form the longitudinal means for connecting and bracing ,the liner and nozzle with respect to their associated jackets by restraining the liner and nozzle to a corresponding number of buckling modes. In this illustration, the liner and nozzle are restrained in the twelfth mode. Under this restraint a liner of common size and thickness can withstand a pressure several times as great as that withstood by a similar one with other means of support. One preferred structure for connecting the jacket portions with adjacent parts has been shown in Figs. 1 and 2 and in enlarged scale in Fig. 3. This includes the provision of T-shaped webs or strips 18 which extend longitudinally of the assembly and which are preferably integral with the liner for the chamber and the nozzle sections. The heads of these webs are received in channels 19. The parts providing the channels are preferably integral with and extend from the inner faces of the jacket portions. The webs as well as the channel portions may conveniently be formed at the time the jackets, chamber liner and nozzle are produced. Such production may be by means of an extrusion process. Otherwise, the jacket portions and the chamber liner and nozzle may be manufactured of relatively thick stock which is then machined to eliminate undesired portions so that a requisite thinness of the nozzle, liner and jacket portions results. It is, of course, apparent that certain portions might be manufactured under an extrusion technique while other parts might be machined as afore indicated. Alternative manufacturing procedure might likewise be followed if this proves to be desirable.

In certain instances, an assembly might have the coolant passages 16 and 17 of very small radial dimension. Under these circumstances, it may not be feasible to crimp the channels over the webs in non-cylindrical sections. With this in mind, structures such as are shown in Figs. 4 and may be resorted to. In the former figure, the jacket may have its material extended outwardly as indicated at 20 in line with a web station. The inner face of the jacket under these conditions is formed with an undercut slot or groove. The web 21 extending from the liner 11 has its head portion of a width such that it may enter the groove and engage against the base of the same as shown in the figure under consideration. Thereafter, Z-shaped keys or strips 22 are interposed between the surfaces of the channel and the adjacent surfaces of the web and its head. This will prevent radial movement between the parts which are thus securely anchored with respect to each other.

As in Fig. 5, the jacket may be enlarged as at 23 and define on its inner face a suitable number of channel portions. Inwardly extending lips 24 may be provided at the mouths of these channels. The inner surfaces of the channels are rounded inwardly of the lips 24 and receive keys or retaining members 25 which bear against the rounded faces formed adjacent the heads of the Ts of webs 26. Thus, it is again apparent that the parts are properly connected so as to prevent relative radial movement of the same. As shown, the distance between the opposed edges of lips 24 is sufficiently great so that the 8. head of the web may be freely introduced into the channel until it bears against the base of the same. Only thereafter are the keys or rods 25 positioned.

Under'certain conditions, it may be desired that the chamber liner or the nozzle be made so thin that it is not feasible to machine webs upon these members. If it is otherwise impracticable to provide such webs, then a structure such as is shown in Fig. 6 may be employed. In that view the reduced or thin liner has been indicated at27. This liner is extended outwardly as indicated at 28 to provide number of properly spaced longitudinal tubular portions. These are drawn up into the adjacent channel portions 29 forming a part of the jacket sections. After the parts have been thus positioned, keys 30 in the form of rods are forced into these tubes to thus expand the latter into anchoring engagement with the surfaces of the channels.

In all of the several structures it is apparent, in addition to the support which results between the nozzle-liner portions and the adjacent jacket sections, that the chamber liner and nozzle are free to longitudinally expand to a greater degree than these adjacent jacketing parts. Thiswill be necessary because the nozzle and liner are subjected to very high temperatures, while the jacket portions are subjected to much lower temperatures. Also, it is feasible to provide coolant passages, the depths of which may be closely controlled. As shown especially in Fig. 1, portions of the channels may be omitted, for example, in the region of the nozzle throat. This is because the reduction in diameter at this zone causes the throat to be proportionately stiffer and provides greater resistance to the crushing action of the propellant pressure. In this connection, it will be understood that the webs 18 or their equivalents provide considerable stiffening action for the nozzle and the chamber liner. Throughout other areas where the crushing action is more severe, both the channels and cooperating webs may be furnished.

As somewhat diagramatically indicated in Fig. 7, the liner 31 and the jacket section 33 may be conveniently formed of flat sheets either by the extrusion or machining technique in order to provide webs 32 and channels 34. These sheets are then rolled to provide the chamber jacket 10 and chamber liner 11 and the abutting edges of these different sheets are secured against movement as, for example, by welds 35 as shown in Fig. 2. Thereupon the cylindrical chamber liner 11 is slid into the chamber jacket so that the webs 18 have their head portions received within the channels 19. In the instance of structures such as are shown in Figs. 4, 5, and 6, the keys are thereupon slid into position. Where a structure such as is shown in Fig. 3 is involved, it is, of course, apparent that the channels might have their parts initially somewhat opened so that the liner and jacket may be freely slid with respect to each other. Thereafter, the channel portions might be bent or shifted to anchor the webs against accidental movements and should such anchoring be desirable.

In the instance of non-cylindrical sections such as are formed by the parts of the nozzle 1213 and the nozzle jacket 14-15, it is not possible to slip the members together in the same manner as that in which the chamber jacket and liner are connected. Therefore, the parts of the channel are initially formed as for example is shown in Fig. 8. In that view, the numeral 36 indicates the nozzle jacket and 37 the nozzle. Extending outwardly from the face of the latter are webs 38. These are received in channels defined by inwardly extending spaced portions 39. Such portions are left in open positions during the assembly of the parts. After the webs are in position (by, for example, springing the channel portions 39 to a slight extent so as to allow movement of the Webs 38 past the same) these portions 39 are then rolled or crimped. This will retain the webs. In connection with the parts adjacent the nozzle, it will be understood that while not shown, the nozzle jacket is split into. two or resent In this fashion a cylindrical chamber liner and a nozzle of circular cross-section are provided with anumber of,

longitudinal means for connecting and bracing each to the associated jacket thus res-training the liner and nozzle to a corresponding number of buckling modes so as'to enable these members to best resist the effect of external coolant pressure. It is brought out that the liner and nozzle must be of circular form and of unit construction to attain the greatest strength and resistance to inward distortion by the pressure. ,And, it is shown that the structure of this form'c'an attain this greatest strength andresistance to distortion only when the longitudinal means for connecting and bracing permit longitudinal relative expansion offthe parts occasioned by the cooling process. Further, as has been noted this longitudinal freedom for expansion, in the means for connecting and bracing these internal members to restrain them in the proper buckling mode, is best provided, without introducing eccentricity in the structure, by unit construction and by the use of cooperating headed and channel members allowing for slidablerelative motion. Finally, the assembly of this structure is made convenient through the use of keys to retain the cooperating members. Thus, the difficulties, as aforenoted, are overcome and, among others, the several objects of the invention are achieved. Obviously numerous changes in construction and re-arrangement of the parts might be *resorted to without departing from the spirit of the invention as de fined by the claims. r

I'claim:

1. In an engine combustion chamber in combination, a liner and a jacket encircling said liner pi'oviding an intervening passage for conducting coolant under pressure; a plurality of headed members, a plurality of cooperating channelmember's receiving said headed members, certain of said members extending outwardly from and secured to said'liner', others extending inwardly from and secured to said jacket, a number of longitudinally movable keys interposed between adjacent surfaces of 'said members, whereby the liner and jacket'may be assembled to retain the headed members within the channel members to con nect and brace said liner and jacket against'distortion by coolant pressure, said headed and channel members and keys providing" an essentially unobstructed intervening passage for conducting coolant under *pressure, said headed and channel members and keys precisely determining the depth of said intervening passage, saidheaded and channel members and keys being movable relative to each other to permitthe liner and'jacketto have relative longitudinal expansive and contractive movements by virtue ofthe'existenceof temperature differences thereof.

2. In an engine combustion chamber in combination, a a

liner, a jacket encircling said thin liner providing an intervening passage for "conducting coolant under pressure; a plurality of channels formed in said jacket, matching liner portions entering said channels, keys interposed between adjacent surfaces of said portions and channels, whereby the thin liner portions are retained and connected within the jacket channels, said connection bracing said thin liner and jacket against distortion by coolant pressure, said channels and thin liner portions providing an essentially unobstructed intervening passage for conducting coolant under pressure, said channels and thin liner portions precisely determining the depth of said intervening passage, said channels and thin liner portions being movable in longitudinal directions with respect to each other to permit relative longitudinal expansive and contractive movements between the thin liner and the jacket by virtue of the existence of temperature differences thereof.

3. In a rocket engine in combination, means defining a combustion chamber and a nozzle the operative surfaces which extend in non-parallel relationship, a nozzle jacket encircling said nozzle providing an interveningpassage for conducting coolant under pressure; a plurality of headed members, cooperating channel members receiving said headed members, certain of said members extending outwardly from and secured to said nozzle, others extending inwardly from and secured to said jacket, a number of longitudinally movable keys interposed'between the adjacent surfaces of said members, whereby the nozzle and nozzle jacket may be assembled toretain the headed members within the channel members to connect and, brace said nozzle and jacket against distortion by coolant pressure, said headed and channel members and keys providing an essentially unobstructed intervening passage for conducting coolant under pres-' sure, said headed and channel members and keys precisely determining the depth of said intervening passage, said headed and channel members and keys being shiftable to permit the nozzle and jacket to have limited relative longitudinal expansive and contractive movements by virtue of the existence of temperature differences thereof.

4. In a rocket engine in combination, means defining av combustion chamber and a thin nozzle the operative surfaces of which extend in non-parallel relationship, a nozzle jacket encircling said thin nozzle providing an intervening passage for conducting coolant under pressure, a plurality of channel members formed in said jacket, a number of thin nozzle portions entering said jacket channels and a number of longitudinally movable keys for providing couplings, whereby the thin nozzle portions may be assembled to be retained within the jacket channels to connect said thin nozzle and said nozzle jacket against distortion by coolant pressure, said channels and thin nozzle portions providing an essentially unobstructed intervening passage for conducting coolant under pressure, said channels and thin nozzle portions precisely determining the depth of said intervening passage, said channels and thin nozzle portions forming a part of said couplings to permit limited relative longitudinal expansive and contractive movements between the thin nozzle and the nozzle jacket by virtue of the existence of temperature differences thereof.

5. In an engine combustion chamber in combination, a jacket, a thin cylindrical liner of unit construction within and spaced from the jacket to provide intervening passages for conducting coolant under pressure in excess of that within the liner, a number of equally spaced and essentially continuous longitudinal means to radially support said thin cylindrical liner of unit construction with respect tosaid jacket to restrain said thin cylindrical liner of unit construction to a corresponding number of buckling modes to prevent inward buckling of said liner of unit construction by said coolant pressure.

6. In an engine combustion chamber in combination, a jacket, a thin cylindrical liner of unit construction withand spaced from the jacket to provide intervening passages'for conducting coolant under pressure in excess of that within the liner, a number of equally spaced and essentially continuous longitudinal means extending into said passages to radially connect tnd brace said jacket with respect to said thin cylindrical liner of unit construction, to restrain the latter in a corresponding number of buckling modes, to prevent change in depth of the passages by said coolant pressure.

7. In an engine combustion chamber in combination, a jacket, a thin cylindrical liner of unit construction within and spaced from the jacket to provide intervening passages for conducting coolant under pressure in excess of that within the liner, a number of equally spaced and essentially continuous longitudinal means to radially support said thin cylindrical liner of unit construction with respect to said jacket to restrain said thin cylindrical liner of unit construction to a corresponding number of buckling modes to prevent inward buckling of said amen thin cylindrical liner of unit construction by said coolant pressure, and movable means forming a part of said connecting means and functioning inthe presence of a temperature difference existing between said jacket and liner, whereby said jacket and liner may have relative longitudinal expansive and contractive movements by virtue of said temperature difference.

8. In an engine combustion chamber in combination, a jacket, a thin liner of longitudinal panels of unit construction within and spaced from the jacket to provide intervening passages for conducting coolant under pressure in excess of that within the liner, the radius of curvature of said longitudinal panels being less than the general radius of the liner, a corresponding number of equally spaced and essentially continuous longitudinal means to radially support by the jacket said longitudinal panels of lesser radius of curvature to prevent inward buckling of said longitudinal panels by said coolant pressure.

9. In a rocket engine in combination, means defining a combustion chamber and a thin circular nozzle of unit construction, a nozzle jacket encircling said nozzle and spaced therefrom to. provide intervening passages for conducting a coolant under pressure in excess of that within the nozzle, a number of equally spaced and essentially continuous longitudinal means to radially support said thin circular nozzle of unit construction with respect to the nozzle jacket to restrain said thin circular nozzle of unit construction to a corresponding number of buckling modes to prevent the inward bucklingtof said thin circular nozzle of unit construction by said coolant pressure.

10. In a rocket engine in combination, means defining a combustion chamber and a thin circular nozzle of unit construction, a nozzle jacket encircling said nozzle and spaced therefrom to provide intervening passages for conducting coolant under pressure in excess of that within the nozzle, a number of equally spaced and es sentially continuous longitudinal means in said passages to radially connect and brace the thin circular nozzle of unit construction with respect to the nozzle jacket, to restrain the thin circular nozzle of unit construction to a corresponding number of buckling modes, to prevent change in depth of the passages by said coolant pressure.

11. In a rocket engine in combination, means defining a combustion chamber and a thin circular nozzle of unit construction, a nozzle jacket encircling said nozzle and spaced therefrom to provide intervening passages for conducting coolant under pressure in excess of that within the nozzle, a number of equally spaced and essentially continuous longitudinal means to radially support said thin circular nozzle of unit construction with respect to the nozzle jacket to restrain said thin circular nozzle of unit construction to a corresponding number of buckling modes to prevent inward buckling of said thin circular nozzle of unit construction by said coolant pressure and movable means forming a part of said connecting means andfunctioning in the presence of a temperature difference existing between said nozzle and noz zle jacket, whereby the nozzle and nozzle jacket may have limited relative longitudinal ,expansive and contractive movements by virtue of said temperature-difference. I

12. In an engine combustion chamber in combination, a thin cylindrical liner of unit construction, a jacket encircling said liner providing an intervening passage for conducting coolant under pressure, a plurality of headed members extending outwardly from and secured to said liner, a plurality of channel members for receiving said headed members extending inwardly from and secured to said jacket, said headed and channel members engaging to connect and brace the liner and jacket with respect to each other and against distortion by coolant pressure in excess of the pressure developed within said liner, said headed and channel members providing an essentially unobstructed intervening passage for conducting coolant under pressure, said headed and channel members precisely determining the depth of said intervening passage, said headed and channel members having relative movement, whereby said liner and jacket may have relative longitudinal expansion and contraction by virtue of the existence of temperature differences thereof.

13. In a rocket engine in combination, means defining a combustion chamber, a thin circular nozzle of unit construction, a nozzle jacket encircling said nozzle providing an intervening passage for conducting coolant under pressure, a plurality of beaded members extending outwardly from and secured to said nozzle, channel members extending inwardly from and secured to said jacket engaging the headed members to connect and brace the nozzle and jacket against distortion by coolant pressure in excess of the pressure developed within the nozzle, said headed and channel members providing an. essentially unobstructed intervening passage for conducting coolant under pressure, said headed and channel members precisely determining the depth of said intervening passage, said headed and channel members, whereby said nozzle and nozzle jacket may have limited relative longitudinal expansive and contractive movements by virtue of the existence. of temperature difierences thereof.

References Cited in the file of this patent UNITED STATES PATENTS 2,268,464 Seippel Dec. 30, 1941 2,473,728 Rutledge June 21, 1949 2,523,654 Goddard Sept. 26, 1950 2,544,538 Mahnken et a1. Mar. 6, 1951 2,669,835 Rossheim et al. Feb. 23, 1954 FOREIGN PATENTS 764,771 France Mar. 12, 1934 1,011,046 France Apr. 2,, 1952