Patent Publication Number: US-7581383-B2

Title: Acoustic pulsejet helmet

Description:
FIELD OF INVENTION 
     The invention relates generally to pulsejet engines and more particularly to valve-less pulsejet engines that direct all thrust forces along an axis of positive thrust. 
     BACKGROUND OF THE INVENTION 
     Pulsejet engines are extraordinarily simple devices that provide an inexpensive means to provide thrust for an aircraft. Most pulsejets typically include a mechanical valve to prevent air and thrust from escaping through the inlet of the pulsejet when combustions occur in the combustion chamber of the pulsejet. A main disadvantage of these pulsejets is that they generally have a low efficiency and the mechanical valves have a limited durability. Some more recent pulsejet designs have implemented a pneumatic air inlet valve that eliminates the durability problem of the mechanical inlet valve. The pneumatic air valve generally injected air into a throat section of the inlet nozzle as the fuel in the combustion chamber ignited. This created a high pressure zone at the inlet nozzle throat that prevented thrust from the fuel combustion from escaping out the inlet. Notwithstanding the removal of the mechanical valve and greatly improved durability, implementation of the pneumatic air valve required supplemental equipment to provide and inject the air into the inlet nozzle of the pulsejet. And, the amount and complexity of the additional supplemental equipment significantly increases as the number of pulsejets included in a system multiply. 
     Additionally, a typical bank of pulsejets would include a plurality of round pulsejets aligned in columns and rows. In this configuration, the pulsejets where interconnected using a webbing of orthogonal walls that formed a grid of square compartments with a single pulsejet within each compartment. The interconnected webbing adds considerable weight to each pulsejet bank and the space created by round pulsejets in square compartments created gaps that could allow a portion of the thrust generated by each pulsejet to escape in the wrong direction. 
     A need therefore exists for a pulsejet engine design that reduces maintenance, weight and complexity of existing designs while increasing the thrust efficiency. 
     BRIEF SUMMARY OF THE INVENTION 
     In various embodiments of the present invention, a pulsejet is provided that includes an inlet, an exhaust nozzle, and a combustion chamber between the inlet and the exhaust nozzle. The pulsejet additionally includes a flow-turning device positioned over an end of the inlet. The flow turning device forms an air flow pathway (AFP) having a substantially 180° turn. The 180° turn aligns a direction of exhaust exiting the combustion chamber through the inlet along a positive axial thrust line and substantially parallel with exhaust exiting the combustion chamber through the nozzle. 
     In various other embodiments, a method for providing vertical take off and landing propulsion for an aircraft is provided. The method includes providing at least one valve-less pulsejet integrated within a fuselage of the aircraft. The pulsejet includes a body having an inlet, an exhaust nozzle, a combustion chamber between the inlet and the exhaust nozzle. The method additionally includes positioning a flow-turning device over an end of the body to form an air flow pathway (AFP) having a substantially 180° turn. The 180° turn aligns a direction of exhaust exiting the combustion chamber through the inlet to be substantially parallel with exhaust exiting the combustion chamber through the nozzle along a positive axial thrust line. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. Furthermore, the features, functions, and advantages of the present invention can be achieved independently in various embodiments of the present inventions or may be combined in yet other embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and accompanying drawings, wherein: 
         FIG. 1A  is an isometric cross sectional view of the valve-less pulsejet engine, in accordance with various embodiments of the present inventions; 
         FIG. 1B  is a cross sectional side view of the pulsejet engine shown in  FIG. 1A ; 
         FIG. 2  is a cross sectional side view of the pulsejet engine shown in  FIG. 1B  including an elongated straight inlet section, in accordance with various embodiments of the present invention; 
         FIG. 3A  is a cross sectional side view of the pulsejet engine shown in  FIG. 1B  including a cruciform shaped combustion chamber, in accordance with various embodiments of the present invention; 
         FIG. 3B  is a cross sectional top view of the cruciform shaped combustion chamber shown in  FIG. 3A , along line  3 B- 3 B, having a flow-turning device positioned over an inlet of the pulsejet engine; 
         FIG. 4  is an isometric view of the pulsejet engine shown in  FIG. 1A  mounted within an augmentor cell, in accordance with various embodiments of the present invention; 
         FIG. 5  is an isometric view of a plurality of the pulsejet engines shown in  FIG. 1  A mounted within a multi-bay augmentor to form a pulsejet augmentor bank, in accordance with various embodiments of the present invention; 
         FIG. 6  is an isometric view of a linear acoustic pulsejet (LAP), in accordance with various embodiments of the present invention; 
         FIG. 6A  is a cross-sectional view of the LAP shown in  FIG. 6 , along line A-A; 
         FIG. 6B  is a side view of the LAP shown in  FIG. 6 ; 
         FIG. 6C  is an isometric view illustrating a plurality of dividers in a linear helmet of the LAP shown in  FIG. 6 ; 
         FIG. 7  is an isometric view of the LAP shown in  FIG. 6  having undulating side panels, in accordance with various embodiments of the present invention; 
         FIG. 7A  is an end view of the LAP shown in  FIG. 7 ; 
         FIG. 8  is an isometric view of the LAP shown in  FIG. 6  mounted in a LAP augmentor, in accordance with various embodiments of the present invention; 
         FIG. 8A  is an isometric view of the LAP shown in  FIG. 8  including auxiliary inlets in the LAP augmentor, in accordance with various embodiments of the present invention; 
         FIG. 9  is an isometric view of the LAP shown in  FIG. 6  including double walled intercostals, in accordance with various embodiments of the present invention; 
         FIG. 9A  is a cross-sectional view of the LAP shown in  FIG. 9 , along line A-A; 
         FIG. 9B  is the cross-section shown in  FIG. 9A  having walls of double walled intercostals forming rounded corner for the pulsejet cells; 
         FIG. 9C  is an isometric view illustrating a plurality of double-walled dividers in the linear helmet of the LAP shown in  FIG. 9 ; and 
         FIG. 10  is a perspective view of an exemplary aircraft having multiple banks of pulsejet engines providing for VTOL capability. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application or uses. Additionally, the advantages provided by the preferred embodiments, as described below, are exemplary in nature and not all preferred embodiments provide the same advantages or the same degree of advantages. 
       FIGS. 1A and 1B  are cross sections of the valve-less pulsejet engine, in accordance with various embodiments of the present inventions. The pulsejet engine will simply be referred to herein as the pulsejet  10 . The pulsejet  10  includes a body  12  having an inlet  14 , an exhaust nozzle  18 , a combustion chamber  22  between the inlet  14  and the exhaust nozzle  18 , and a flow turning device  26 , herein referred to as a helmet  26 , positioned over an end of the inlet  14 . An air flow pathway (AFP)  30  through which air flows into and out of the pulsejet  10  is formed between a side wall  34  of the helmet  26  and an outer portion of the pulsejet  10  near combustion chamber  22  and the inlet  14 . In various embodiments, as shown in  FIG. 1 , the AFP  30  is an annular AFP. In operation of the pulsejet  10 , a propulsion cycle comprises an air intake phase, a compression phase and a combustion phase. Generally, during the compression phase, intake air flows through the AFP  30  in the A direction and enters the inlet  14 . The intake air is mixed with fuel injected into the combustion chamber  22  and detonated during a combustion phase due to pressure created inside the combustion chamber  22 . More particularly, initially air is injected into the combustion chamber  22  to mix with the injected fuel and an ignition source is provided to cause the air/fuel mixture to combust during at least one initial combustion phase. Each air/fuel combustion produces exhaust thrust that discharges from the exhaust nozzle  18  in B direction. This exhaust thrust will be referred to herein as the primary exhaust or primary thrust. Each combustion phase additionally produces exhaust thrust that exits the combustion chamber  22  through the inlet in the C direction. Thrust exiting the combustion chamber  22  through the inlet  14  of the pulsejet  10  will be referred to herein as secondary exhaust or secondary thrust. 
     Reflective pressure waves generated by each air/fuel combustion create pressures within the combustion chamber  22  that cause subsequent air/fuel mixtures to detonate during subsequent propulsion cycles. The propulsion cycle of a valveless pulsejet, such as pulsejet  10 , is described in issued U.S. Pat. No. 6,824,097, titled “Vertical Takeoff And Landing Aircraft” and issued Nov. 30, 2004, which is herein incorporated by reference in its entirety. In various embodiments, the helmet  26  forms approximately a 180° turn section  36  in the AFP  30  that turns the secondary exhaust thrust effectively 180° such that both the primary and secondary thrusts flow along an axis of positive thrust in the B direction that is approximately parallel with a pulsejet  10  longitudinal centerline C. Therefore, negative thrust problems of known pulsejet engines are eliminated without the need for additional devices or equipment, such as mechanical valves or large high pressure air injection systems. Additionally, the AFP  30  formed by the helmet  26  ensures that a path followed by inlet acoustic expansion/reflection waves is such that they meet returning nozzle acoustic expansion/reflection waves in the combustion chamber  22  to initiate new cycle ignition. After ignition, expansion waves exit the pulsejet  10  via the inlet  14  and the exhaust nozzle  18  causing reflection waves to travel through the inlet  14  and the nozzle  18  toward the combustion chamber  22 . However, prior to ignition cool air is taken into the combustion chamber via the AFP  30 , such that the inlet  14  maintains a much cooler temperature than the exhaust nozzle  18 , which during operation can obtain a temperature of approximately 1500° F. Therefore, since the speed and distance traveled of the expansion/reflection wave is a function of temperature, it takes the expansion/reflection waves much more time to traverse through the cooler, shorter inlet  14  than through the hotter, longer nozzle  18 . Thus, the inlet acoustic expansion/reflection waves meet returning nozzle acoustic expansion/reflection waves to provide self-sustained operation, i.e. self-sustained repetitive propulsion phases, of the pulsejet  10  at or near a resonant frequency. 
     Additionally, in various embodiments helmet  26  has an outside diameter D that is approximately 100% to 125% of an outside diameter F of the combustion chamber  22 . Therefore, an overall diameter of installation of the pulsejet  10  is minimized such that installation of the pulsejet  10  in an aircraft, e.g. a VTOL aircraft, requires only a minimal amount of space. The helmet  26  and the inlet  14  are sized such that the entire AFP  30 , including the 180° turn section  36 , provides as much airflow gap as possible to increase the inlet airflow and improve performance of pulsejet  10 . In various embodiments, the helmet  26  is formed such that the AFP  30  increases in area near a lip  37  of the helmet side wall  34 . This allows more air to be drawn into the pulsejet and diffuses the secondary exhaust as it exits the AFP  30 . 
     Referring to  FIG. 2 , in various embodiments the pulsejet  10  includes an elongated straight inlet section  40  extending from the inlet  14 . The inlet section  40  provides a specified aspect ratio, i.e. inlet section length over inlet section diameter, for stable operation of the pulsejet.  10 . The straight inlet section  40  creates an AFP  30  having an expanding area ratio as helmet side wall  34  extends toward the combustion chamber  22  and nozzle  18 . That is, an annular area between the exterior of the inlet section  40  and the interior of the helmet side wall  34  increases from the open end, or inlet  14 , of the inlet section  40  to an open end of the helmet side wall  34 . Therefore, the expanding area ratio provide increase and improved air flow into the pulsejet  10  during the compression phase and also provides diffusion of secondary exhaust during the combustion phase that reduces or eliminates back pressure caused by a restrictive AFP  30 . The length-to-diameter ratio of the inlet section  40  is configured to acoustically tune the inlet section  40  such that resonant waves will sustain operation, i.e. combustions, of the pulsejet  10  with no other combustion controls than fuel. That is, further artificial ignition, e.g. a glow plug or spark plug, is not required. A key critical resonant length P of the inlet section  40  extends from an inlet plane in the combustion chamber  22  to the lip  37  of the helmet side wall  34 . The length P control the resonant frequency of the reflection waves that combust the air/fuel mixture in the combustion chamber  22 . Furthermore, the straight inlet section  40  allows the outside diameter D of the helmet  26  to be minimized to provide a reasonably compact design that reduces the overall diameter of installation. 
     Referring now to  FIGS. 3A and 3B , in various embodiments, the combustion chamber  22  has a non-cylindrical shape. For example, the combustion chamber  22  can have an elongated cruciform or star-like shape. The cruciform combustion chamber  22  includes a plurality of linear apexes  41  and linear valleys  43 . The spaces between the interior of the helmet side wall  34  and the valleys  43  create a plurality of AFPs  30  that provide effectively unimpeded air intake flow and secondary exhaust flow. This reduces or eliminates back pressure caused by a restrictive AFP  30 . In addition to providing the AFP  30 s, the cruciform shaped combustion chamber  22  allows the outside diameter D of the helmet to be approximately equal to the outside diameter F of combustion chamber  22  at the widest point, i.e. from one apex peak  41  to an opposing apex peak  41 . Therefore, the overall diameter of installation can be greatly reduced. 
     Referring now to  FIG. 4 , in various embodiments, the pulsejet  10  is mounted within an augmentor cell  38 . The augmentor cell  38  includes a pair of opposing entraining walls  42  adapted to entrain ambient air with the pulsejet primary and secondary exhausts to maximize propulsion thrust from the pulsejet  10 . For clarity of illustration, one of the entrainment walls  42  has been removed from  FIG. 2 . The entrainment walls  42  can have any shape suitable to entrain the ambient air. For example, the entrainment wall  42  can be flat or curved, as shown in  FIG. 4 . The augmentor cell  38  additionally includes a pair of opposing side panels  46  connected to and substantially orthogonally between the entraining walls  42 . The pulsejet  10  can be mounted within the augmentor cell  38  using any suitable mounting means, component, device or structure. For example, the pulsejet  10  can be mounted to one or more of the augmentor cell walls  42  and/or the side panels  46  using one or more of fairings  50 . Although the fairings  50  are shown to extend along the entire length of the pulsejet  10 , the fairing  50  can extend along a portion of each pulsejet  10  without altering the scope of the invention. In various embodiments, the side panels  46  include a plurality of apertures  54  adapted to allow a portion of the entrained air and the primary and secondary exhausts to exit the augmentor cell  38  in a cross flow direction G. It should be understood that any of the various embodiments described above in reference to  FIGS. 1A ,  1 B,  2 ,  3 A and  3 B can be incorporated in the pulsejet augmentor cell  38 . 
     Referring to  FIG. 5 , in various embodiments a plurality of pulsejets  10  are mounted within a multi-bay augmentor  58  to form a pulsejet augmentor bank  62 . The pulsejet augmentor bank  62  includes a pair of opposing entraining walls  66  and a plurality of intercostals  70  connected to and substantially orthogonally between the entraining walls  66 . For clarity of illustration, one bank entrainment wall  66  has been removed from  FIG. 3 . The plurality of intercostals  70  effectively subdivide the pulsejet augmentor bank  62  into a plurality of pulsejet augmentor bays  74  similar to the augmentor cell  38  described above with reference to  FIG. 2 . Analogous to the entrainment walls  42  of the augmentor cell  38  in  FIG. 2 , the bank entrainment walls  66  are adapted to entrain ambient air with the primary and secondary exhausts of each pulsejet  10  to maximize propulsion thrust from the pulsejets  10 . Additionally, the bank entrainment walls  66  can have any shape suitable to entrain the ambient air, e.g. flat or curved, and each of the pulsejets  10  can be mounted within the respective augmentor bay  74  in any suitable manner, e.g. using one or more fairings such as fairing  50  shown in  FIG. 4 . Furthermore, in various embodiments, the bank intercostals  70  include a plurality of apertures  78  adapted to allow a portion of the entrained air and the primary and secondary exhausts of each pulsejet  10  to exit the respective augmentor bay  74  in a cross flow direction G. Therefore, the apertures  78  permit equalization of flow between each of the pulsejet primary and secondary exhaust flows such that any of the pulsejets  10  within the pulsejet augmentor bank  62  that operate above or below a nominal operating condition are equalized with the remaining pulsejet  10  primary and secondary exhaust flows. It should be understood that any of the various pulsejet  10  embodiments described above in reference to  FIGS. 1A ,  1 B,  2 ,  3 A and  3 B can be incorporated in the pulsejet augmentor bank  62 . 
     Exemplary embodiments of the pulsejet augmentor cell  38  and the pulsejet augmentor bank  62  are described in issued U.S. Pat. No. 6,824,097, titled “Vertical Takeoff And Landing Aircraft”, issued Nov. 30, 2004, which is herein incorporated by reference in its entirety. 
     Referring now to  FIGS. 6 ,  6 A,  6 B,  7  and  7 A a linear acoustic pulsejet (LAP)  72  includes a body  82  having a first side panel  86  and an opposing substantially parallel second side panel  90 . A plurality of substantially parallel intermediate walls, or intercostals  94 , are connected to and substantially orthogonally between each of the first and second side panels  86  and  90  to create a plurality of pulsejet cells  98  in an interior of the body  82 . The LAP  72  additionally includes an inlet section  102  that forms an inlet for each pulsejet cell  98 , an exhaust nozzle section  106  that forms an exhaust nozzle for each pulsejet cell  98 , and a combustion chamber section  110  that forms a combustion chamber between the inlet and the exhaust nozzle of each pulsejet cell  98 . The inlet, exhaust and combustion sections  102 ,  106  and  110  are best shown in  FIG. 6B . The inlet, exhaust nozzle and combustion chamber of each pulsejet cell  98  will be respectively referred to herein as inlet  102 ′, exhaust nozzle  106 ′ and combustion chamber  110 ′. The LAP  72  further includes a linear inlet helmet or inlet cap  114  positioned over and connected to an end of the inlet section  102 . A linear air flow pathway (LAFP)  118 , best shown in  FIG. 7A , is formed between opposing walls  120  of the linear helmet  114  and the inlet section  102  through which air flows into and out of each pulsejet cell  98 . For clarity of  FIGS. 6 ,  6 A,  6 C and  7 , the side panels  86  and  90 , and the intercostals  94  are illustrated by a single solid or dashed line. However, it should be understood that the side panels  86  and  90 , and the intercostals  94  have a thickness sufficient to withstand the heat, stresses and forces the panels  86  and  90 , and the intercostals  94  are exposed to during operation of the aircraft and the LAG  72 . 
     In operation of the LAP  72 , each pulsejet cell  98  operates independently of the other pulsejet cells  98 . For each pulsejet cell  98  one propulsion cycle comprises an air intake phase, a compression phase and a combustion phase. Generally, during the compression phase, intake air flows through the LAFP  118  in the H direction and enters the inlets  102 ′ of the respective pulsejet cell  98 . The intake air is mixed with fuel injected into the respective pulsejet cell  98  combustion chambers  110 ′ and detonated during the combustion phase. Initially, air is injected into each combustion chamber  110 ′ to mix with the injected fuel and an ignition source is provided to cause the air/fuel mixture to combust during at least one initial combustion phase. Reflective pressure waves generated by each air/fuel combustion create pressures within the combustion chambers  110 ′ that cause subsequent air/fuel mixtures to detonate during subsequent propulsion cycles. That is, further artificial ignition, e.g. a glow plug or spark plug, is not required. 
     Each air/fuel combustion produces exhaust thrust that discharges from the respective exhaust nozzles  106 ′ in an I direction and exhaust thrust that exits the respective combustion chambers  110 ′ through the respective inlets  102 ′ in the J direction. Exhaust thrust discharging via each pulsejet cell nozzle  106 ′ will be referred to herein as the LAP primary exhaust thrust or primary thrust and exhaust thrust exiting via the pulsejet cell inlets  102 ′ will be referred to herein as the LAP secondary exhaust thrust or secondary thrust. In various embodiments, the linear helmet  114  forms the LAFP  118  to have an approximately 180° turn section  116 . The 180° section effectively turns the secondary exhaust thrust 180° such that both the LAP  92  primary and secondary thrusts flow along a plane of positive thrust in the K direction that is approximately parallel with the LAP  92  first and second side panels  86  and  90 . Additionally, in various embodiments, the LAP  92  is operated such that each pulsejet cell  98  is operated effectively 180° out of phase with adjacent pulsejet cells  98 . For example, if the LAP  92  included eight pulsejet cells  98  sequentially numbered from one end of the LAP  92  as pulsejet cells  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7  and  8 , as illustrated in  FIG. 6A , pulsejet cells  1 ,  3 ,  5  and  7  would substantially simultaneously operate 180° out of phase with the substantially simultaneous operation of pulsejet cells  2 ,  4 ,  6  and  8 . More particularly, when pulsejet cells  1 ,  3 ,  5  and  7  are in the compression phase of the propulsion cycle, pulsejet cells  2 ,  4 ,  6  and  8  are substantially simultaneously in the combustion phase, and vice versa. 
     Furthermore, when the air/fuel mixture combusts in the combustion chamber sections  110 ′ of each pulsejet cells  98 , the high pressure primary exhaust is discharged from the respective nozzle sections  106 ′ creating a high pressure zone at the end of each respective nozzle section  106 ′. Because all adjacent pulsejet cells  98  are 180° out of phase, the adjacent pulsejet cells  98  are substantially simultaneously in the compression phase drawing air into the respective combustion chamber sections via the LAFP  118 . As previous combustion results in reduced combustion chamber pressures a significant pressure differential exists between the respective combustion chambers  110 ′ and the ends of the respective nozzles  106 ′. More significantly, by having the adjacent pulsejet cells  98  180° out of phase, the high pressure zones at the end of pulsejet cells  98  in the compression phase is multiplied due to the adjacent pulsejet cell(s)  98  simultaneously discharging primary exhausts. Thus, the pressure differential between the respective combustion chambers  110 ′ and the ends of the respective nozzles  106 ′ is multiplied. This increased or multiplied pressure differential will create significantly larger compressive forces within each combustion chamber section  110 ′ during the respective compression phases and generate higher combustion efficiency for each pulsejet cell  98 . 
     As best shown in  FIG. 6C , the linear helmet  114  includes a plurality of dividers (webbing)  122  that are located within the linear helmet  114  to substantially align with the intercostals  94 . The dividers  122  direct air/exhaust flow into and away from the individual pulsejet cells  98  through the LAFP  118 . In various embodiments, the LAP  72  includes a pair of linear nozzle flaps  124  located at the end of the nozzle section  106 , shown in  FIG. 6 , that pivot to control the primary exhaust flow exiting each pulsejet cell  98 . The nozzle flaps  124  are pivotal between a closed position, in which the exhaust nozzles  106 ′ of each pulsejet cell  98  are completely closed off, and in a full open position, in which the nozzle flaps direct entrained airflow through flap gaps  128  between the nozzle flaps  124  and the nozzle section  106 . 
     Referring particularly now to  FIGS. 7 and 7A , in various embodiments the first and second side panels  86  and  90  of body  82  have an undulating, i.e. wave-like or corrugated, form having a plurality of linear ridges  126  and linear valleys  130  that extend a height L of the body  82  . Each of the intercostals  94  connects between the first and second side panels  86  and  90  at opposing linear valleys  130  so that each pulsejet cell  98  has a quasi-cylindrical or quasi-oval form. That is, each pulsejet cell  98  will have opposing curved walls comprising respective portions of the first and second side panels  86  and  90  and opposing flat walls comprising two of the intercostals  94 . Alternatively, the first and second side panels  86  and  90  could have an undulating form only at the combustor section  110  of the LAP  82 . The linear valleys  130  provide AFPs  30  between the linear helmet  114  and the exterior of the body side panels  86  and  90  that allow increased air flow into and out of each pulsejet cell inlet  102 ′. 
     Referring now to  FIG. 8 , in various embodiments, the LAP  82  is mounted within a LAP augmentor  142 . The LAP augmentor  142  includes a pair of opposing entraining walls  146  adapted to entrain ambient air combined with the LAP  82  primary and secondary exhausts to maximize propulsion thrust from each of the pulsejet cells  98 . The entrainment walls  146  can have any shape suitable to entrain the ambient air. For example, the entrainment walls  146  can be flat or the entrainment walls  146  can be curved, as shown in  FIG. 8 . The LAP augmentor  142  additionally includes a pair of opposing end walls  150  connected to and substantially orthogonally between the entraining walls  146 . The LAP  82  can be mounted within the LAP augmentor  142  using any suitable mounting means, component, device or structure. For example, the LAP  82  can be mounted to one or more of the LAP augmentor entraning walls  146  and/or the end walls  150  using one or more of bridge fairings  154 . In various embodiments, the end walls  150  include a plurality of apertures  158  adapted to allow a portion of the entrained air and the LAP primary and secondary exhausts to exit the LAP augmentor  142  in a cross flow direction M. 
     The LAP  82  is connected to the LAP augmentor  142  such that unimpeded planar gaps or spaces are created between the entraining walls  146  and the LAP side panels  86  and  90 . Entraining low velocity ambient air with the high pressure, high velocity primary and secondary exhaust of each pulsejet cell  98 , will substantially increase the thrust generated by each pulsejet cell  98 . For example, the LAP augmentor  142  can effectively double the thrust generated by each pulsejet cell  98 . It should be understood that it is with the scope of the invention for the augmentor  142  to include the embodiment of the LAP  82  illustrated in  FIG. 6 . 
       FIG. 8A  is an isometric view of the LAP  82  and LAP augmentor  142 , wherein the augmentor entraining walls  146  include auxiliary inlet flaps  132 , in accordance with various embodiments of the present invention. The inlet flaps  132  are pivotal between a closed position, in which the entraining walls  146  substantially have the form shown in  FIG. 8 , and various open positions in which an auxiliary air intake opening  164  is provided. The size of the auxiliary air intake opening  164  is variable based on the position of the auxiliary inlet flaps  132 . The auxiliary air intake openings allow auxiliary air flows into the LAP augmentor  142  that supply intake air to the LAP  82 . When the auxiliary inlet flaps  132  are in the closed position, all air supplied to the LAP  82  is provided through the open top of the LAP augmentor  142 . Depending on the open position of the auxiliary inlet flaps  132 , air supplied to the LAP  82  via the open top of the LAP augmentor  142  will be varyingly reduced. That is, the further open the auxiliary inlet flaps  132  are, the more air will be supplied to the LAP  82  through the auxiliary air intake opening  164 . This allows the air flowing through the top of the LAP augmentor  142  to increasingly be used to cool the LAP  82 . The auxiliary inlet flaps  132  and the auxiliary air intake opening  164  can be of various designs to accommodate specific aircraft integration, and remain within the scope of the invention. 
     For clarity of  FIG. 8 , the side panels  86  and  90 , and the intercostals  94  of the LAP  82  are illustrated by a single solid or dashed line. However, it should be understood that the side panels  86  and  90 , and the intercostals  94  have a thickness sufficient to withstand the heat, stresses and forces the panels  86  and  90 , and the intercostals  94  are exposed to during operation of the aircraft and the LAP  82 . Additionally, in various embodiments, the LAP augmentor  142  is incorporated into the structural framework of the aircraft, e.g. a VTOL aircraft, as an integral load bearing structural member of the aircraft. For example, in various embodiments the LAP augmentor entraining walls  146  and the LAP side panels  86  and  90  can functions as keel structures of an aircraft fuselage and the bridge fairings  154  can also function as a load bearing structure for such things as propulsion and/or aircraft loads. In various embodiments, a plurality of LAPs  82  including LAP augmentors  142  can be joined side-by-side. In which case the center augmentor wall  146  could be omitted or formed as a flat partition between the LAPs  82 . 
     Referring now to  FIGS. 9 ,  9 A,  9 B and  9 C in various embodiments, intercostals  94  are double walled partitions having a pair of walls  160 . In various other embodiments, the walls  160  have an air gap  162  between them through which cooling air passes to cool the pulsejet cells  98 . Cooling the pulsejet cells  98  adds to the life or survivability of the material used to fabricate the LAP  82  and to reduce the absorption of heat into the aircraft structure. Additionally, the helmet dividers  122  are double walled dividers having a pair of walls  166  and an air gap  168  between the walls  166  through which air can flow into the double walled intercostals air gap  162  to cool the pulsejet cells  98 , as shown in  FIG. 9C . Although the intercostals air gaps  162  are illustrated in  FIG. 9  to be approximately rectangular, in various embodiments the walls  160  of the double walled intercostals  94  are configured to form the pulsejet cells  98  having rounded corners, as shown in  FIG. 9B . That is, the pulsejet cells will have an effectively oval cylindrical or round cylindrical shape. The rounded corners will improve the aerodynamics and combusting efficiency of the LAP  82 . 
     Referring to  FIG. 10 , an exemplary VTOL aircraft  210  is shown. The VTOL aircraft  210  structurally includes a fuselage, or body,  212  and a pair of flight wings  214 . To provide VTOL capability, a plurality of pulsejet/ejector banks are provided. A pair of pulsejet/ejector aft banks  216  and a pulsejet/ejector forward bank  220  are provided. Each of the pulsejet/ejector aft banks  216  and the pulsejet/ejector forward bank  220  include a plurality of pulsejet engines  218 . The pulsejet/ejector aft banks  216  and the pulsejet/ejector forward bank  220  provide vertical takeoff capability. The VTOL aircraft  210  is further described in U.S. Pat. No. 6,824,097, entitled “Vertical Takeoff and Landing Aircraft”, issued Nov. 30, 2004, the disclosure of which is incorporated herein by reference in its entirety. 
     The LAP  82  described above provides a high thrust to weight ratio, low fuel consumption, highly effective low weight thrust system for aircraft, for example VTOL aircraft. Additionally, the LAP  82  and augmentor  142  can be incorporated as an integral load bearing structure of the aircraft. That is, the LAP  82  and augmentor  142  are totally integrated as a permanent aircraft structure used for carrying aircraft and propulsion loads. Furthermore, the linear aspects of the integration of the LAP  82  and augmentor  142 , as a component of the aircraft structure, will promote more predictable mass flow entrainment characteristics. 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification and following claims.