Patent Publication Number: US-2018037103-A1

Title: Rocket motor integration

Description:
TECHNOLOGICAL FIELD 
     Embodiments of the present invention relate to the integration of a rocket motor into a vehicle. In particular, they relate to the integration of a rocket motor into a support structure of a land-based vehicle or a helicopter. 
     BACKGROUND 
     A rocket motor/engine comprises propellant which, when ignited, causes the rocket motor to eject gas. Ejection of the gas generates thrust. 
     BRIEF SUMMARY 
     According to some, but not necessarily all, embodiments of the invention there is provided a vehicle, comprising: a vehicle support structure comprising a casing of a rocket motor that is arranged to sustain an inertial load generated, at least in part, by the vehicle when the rocket motor is inactive; wherein the casing has a length dimension, a width dimension and a depth dimension, the length dimension being greater than the width dimension and the depth dimension; and wherein the rocket motor is configured to generate a force in a direction that is substantially perpendicular to the length dimension of the casing. 
     According to some, but not necessarily all, embodiments of the invention there is provided a land-based vehicle, comprising: a roll cage comprising a rocket motor that is arranged to sustain an inertial load generated, at least in part, by the vehicle. 
     According to some, but not necessarily all, embodiments of the invention there is provided a land-based vehicle, comprising: a vehicle support structure comprising a casing of a rocket motor that is arranged to sustain an inertial load generated during motion of the vehicle, while the rocket motor is inactive. 
     According to some, but not necessarily all, embodiments of the invention there is provided a helicopter, comprising: a skid structure comprising a rocket motor that is arranged to sustain an inertial load generated, at least in part, by the mass of the helicopter. 
     According to some, but not necessarily all, embodiments of the invention there is provided a pallet comprising: at least one rocket motor having a casing; wherein the casing has a length dimension, a width dimension and a depth dimension, the length dimension being greater than the width dimension and the depth dimension; and wherein the rocket motor is configured to generate a force in a direction that is substantially perpendicular to the length dimension of the casing. 
    
    
     
       BRIEF DESCRIPTION 
       For a better understanding of various examples of the embodiments of the present invention, reference will now be made by way of example only to the accompanying drawings in which: 
         FIG. 1  illustrates a perspective view of the first example of a linear rocket motor; 
         FIG. 2  illustrates a perspective view of some component parts of the first example of a linear rocket motor; 
         FIG. 3  illustrates a cross-sectional view of the first example of a linear rocket motor; 
         FIG. 4  illustrates a plan view of the first example of a linear rocket motor; 
         FIG. 5  illustrates a filter from the first example of a linear rocket motor; 
         FIG. 6  illustrates a perspective view of a second example of a linear rocket motor; 
         FIG. 7  illustrates a schematic of an apparatus; 
         FIG. 8  illustrates a perspective view of a land-based vehicle; 
         FIG. 9  illustrates a side view of the land-based vehicle; 
         FIG. 10  illustrates an aircraft in the form of a helicopter; 
         FIG. 11  illustrates a first example of a support structure for the helicopter; 
         FIG. 12  illustrates a portion of a second example of the support structure for the helicopter; 
         FIG. 13  illustrates an expanded view of a connection between a cross bar and a linear rocket motor in the second example of the support structure for the helicopter; 
         FIG. 14  illustrates a cross-sectional view of a portion of the second example of the support structure for the helicopter; 
         FIG. 15  illustrates a perspective view of a pallet for transporting goods; 
         FIG. 16A  illustrates a plan view of an underside of a first example of the pallet; and 
         FIG. 16B  illustrates a plan view of an underside of a second example of the pallet. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention relate to integrating a rocket motor into a vehicle. The rocket motor is integrated into a support structure of the vehicle which comprises a casing of the rocket motor. The casing is arranged to sustain an inertial load generated, at least in part, by the vehicle when the rocket motor is inactive. The inertial load may be generated, for example, by motion of the vehicle. Alternatively or additionally, the inertial load may be/include a gravitational load which is generated, at least in part, by the vehicle. 
     The vehicle is for transporting people or goods. It may or may not be self-propelled. In some examples, the vehicle is configured to transport multiple people, one of whom may be the driver of the vehicle, and possibly goods in addition. In other examples, the vehicle is configured to transport only a single person, possibly alongside goods, and that person might be the driver of the vehicle. In some further examples, the vehicle may be configured to transport goods and not people. 
     In some examples, the vehicle is a land-based vehicle. In other examples, the vehicle is an aircraft such as a helicopter. In further examples, the vehicle is a spacecraft. An example of a vehicle for transporting goods and not people is a pallet. 
       FIG. 1  illustrates a perspective view of a first example  434  of a rocket motor. 
     The rocket motor includes a casing  440  having a length dimension L, a width dimension W and a depth dimension D. The length dimension L, the width dimension W and the depth dimension D are substantially orthogonal to one another. The first example  434  of the rocket motor may be elongate in shape such that the length dimension L is much greater than the width dimension W and the depth dimension D. For this reason, the rocket motor may be hereinafter referred to as a “linear rocket motor”. 
     In some examples, the length dimension L may be at least 1.25 times as great the width dimension W and/or at least 1.25 times as great as the depth dimension D. In other examples, the length dimension L may be at least twice as great as the width dimension W and/or at least twice as great as the depth dimension D. In some further examples, the length dimension L may be at least five times as great as the width dimension W and/or at least five times as great as the depth dimension D. In some implementations, the length dimension L is in the region of 125 millimetres to 100 metres, the width dimension W is in the region of 100 to 300 millimetres and the depth dimension D is in the region of 100 to 500 millimetres. 
     The casing  440  in the first example  434  comprises a base  435 , a front wall  439   a , two side walls  436 ,  437 , a rear wall  439   b  and an upper wall  443 . The casing  440  might be made from aluminium or one or more other metals. The two side walls  436 ,  437  are substantially planar in the illustrated example. The side walls  436 ,  437  are substantially parallel to one another, substantially orthogonal to the front and rear walls  439   a ,  439   b  and substantially orthogonal to both the base  435  and the upper wall  443 . 
     The base  435  and the upper wall  443  are substantially planar in the illustrated example. The base  435  and the upper wall  443  are substantially parallel to one another, substantially orthogonal to the front and rear walls  439   a ,  439   b  and substantially orthogonal to each of the side walls  436 ,  437 . 
     The front wall  439   a  and the rear wall  439   b  are substantially planar in the illustrated example. The front wall  439   a  and the rear wall  439   b  are substantially parallel to one another, substantially orthogonal to the side walls  436 ,  437  and substantially orthogonal to the base  435  and the upper wall  443 . 
     The base  435 , the side walls  436 ,  437 , the front wall  439   a  and the rear wall  439   b  define a chamber in which (solid) propellant may be stored. In some examples, the propellant may be a single item. It may have a honeycomb structure. Alternatively, the propellant may take the form of one or more fins and/or one or multiple pellets. The pellets may or may not have perforations. The pellets may have a honeycomb structure. 
     The upper wall  443  comprises a plurality of efflux/gas exit apertures  401   a ,  401   b ,  401   c ,  401   d ,  401   e ,  401   f ,  401   g ,  401   h ,  401   i . In this example, the length of each of the exit apertures  401   a - 401   i  is aligned with the length dimension L of the rocket motor  434 . Some or all of the exit apertures  401   a - 401   i  may diverge in the direction of movement of the efflux/gas ejected from the casing  440  in operation. 
     In the illustrated example, the upper wall  443 , the side walls  436 ,  437  and the base  435  are integrally formed, for example, using an extrusion process. Each of the front wall  439   a  and the rear wall  439   b  is partially formed from an edge of each of the upper wall  443 , the side walls  436 ,  437  and the base  435  and also by a surface of an end cap  409   a ,  409   b . The end cap  409   b  which forms part of the rear wall  439   b  can be seen in  FIG. 1 . 
     The end cap  409   b  includes an ignition connection  421  for an igniter  420  of the linear rocket motor  434 . The igniter  420  is arranged to ignite propellant located inside the casing  440  of the linear rocket motor  434 , which causes an efflux/gas to be ejected from the casing  440  via the exit apertures  401   a - 401   i  and which, in turn, causes a force to be generated that is substantially perpendicular to the length dimension L of the casing  440  (and substantially aligned with the depth dimension D). 
       FIG. 2  illustrates some component parts of the first example  434  of a linear rocket motor.  FIG. 3  illustrates a cross section of the first example  434  of a linear rocket motor.  FIG. 4  illustrates a plan view of the first example  434  of a linear rocket motor. 
     In order to show the component parts in  FIG. 2 , the side walls  436 ,  437 , the base  435  and the upper wall  443  have been removed. It can be seen in  FIGS. 2 and 3  that the igniter  420  extends across the length dimension L of the linear rocket motor  434  from one end cap  409   a  to the other end cap  409   b.    
     In the illustrated example, a (substantially planar) filter  410  is present which is positioned above the igniter  420 . Solid propellant (for example in pellet form, as described above may be positioned around the igniter  420 . 
     The filter  410  is positioned between the propellant (not shown) and the gas exit apertures  401   a - 401   i  to prevent unburnt propellant (for instance, unburnt pellet pieces) from being ejected through the exit apertures  401   a - 401   i  in operation. 
       FIG. 5  illustrates a portion of the filter  410  in more detail. The filter  410  comprises a plurality of apertures  411  which enable gas to pass through the filter  410  but prevent chunks of unburnt propellant from passing through. The filter  410  also comprises a plurality of protrusions  412  which abut the inner surface of the upper wall  443 . 
       FIG. 6  illustrates a perspective view of a second example  534  of a linear rocket motor. The second example  534  is the same as the first example  434  save for the orientation of the exit apertures  501   a ,  501   b ,  501   c ,  501   d ,  501   e ,  501   f ,  501   g ,  501   h ,  501   i ,  501   j ,  501   k ,  5011 ,  501   m ,  501   n . In the second example  534 , the length of the exit apertures is orthogonal to the length dimension L of the casing  540 , rather than parallel to it. 
     The reference numerals  509   b ,  521 ,  535 ,  536 ,  537 ,  539   a ,  539   b  and  543  in  FIG. 6  designate an end cap  509   b , an ignition connection  521 , a base  535 , a first side wall  536 , a second side wall  537 , a front wall  539   a , a rear wall  539   b  and an upper wall  543  respectively. 
       FIG. 7  illustrates a vehicle protection apparatus  1000 . The apparatus  1000  may, for example, be for mitigating/preventing damage from being caused to a land-based vehicle, by applying a groundwards force to the vehicle in response to an explosion. Alternatively, the vehicle protection apparatus  1000  may be for mitigating/preventing damage from being caused to a descending aircraft, spacecraft or pallet, by applying an upwards force to the aircraft, spacecraft or pallet. 
     An explosive event local to a land-based vehicle can cause significant trauma to a vehicle and/or a vehicle&#39;s occupants. In order to protect the occupants of the vehicle from shrapnel and blast emanating from an explosive such as a bomb, mine or improvised explosive device (IED), some vehicles comprise armour. 
     The armour may protect the occupants of the vehicle against injury caused directly from the shrapnel and blast effects. However, depending upon the size of the explosive, some aspects of the vehicle (such as the floor of the vehicle if the explosion occurs underneath the vehicle) can be very heavily damaged. Furthermore, an explosion underneath or to the side of a vehicle may cause the vehicle to accelerate rapidly into the air, resulting in injury to the occupants either when being accelerated upwards or when the vehicle lands on the ground. 
     The detonation of a mine generates an initial shockwave which is very quickly followed by a blast wave. If the detonation occurs underneath the vehicle, these events cause damage to the vehicle and contribute to the vehicle being accelerated upwards into the air. 
     Immediately after the explosion occurs, there is an input of energy from the initial shockwave, the following reflected pressure waves, ejecta, and from localised very high pressure gas. Over the next few milliseconds, the gases produced by decomposition of the explosive from the mine expand underneath the vehicle and together with other contributors (to the total impulse imparted to the vehicle) may apply a large enough force to cause the vehicle to accelerate upwards into the air and fall onto its side or top. The effect of the expanding gases can be likened to a large airbag expanding very rapidly under the vehicle. 
     If the mine is buried very shallowly on very hard ground, the upwards force that is generated by the expanding gases is at maximum for around 5 milliseconds or so, and then rapidly reduces in value over the next 5 milliseconds to near zero. However, if the ground is softer and the mine is more deeply buried, the total time over which a particularly significant upwards force is exerted on the vehicle might generally be around 20-30 milliseconds. 
     Furthermore, in the case of a very deeply buried mine, gas escaping from the ground and the ejecta carried with it may continue to provide an impulse to the vehicle for another 30-500 milliseconds or so, depending on the depth of the burial of the explosive and the soil type and condition. The proportion of the total impulse imparted to the vehicle by the ejecta is very variable. If the mine is buried very deeply in a culvert under a road, practically all of the impulse may arise from the ejecta. If the mine is located on the top of a hard surface there may be very little or no contribution from the ejecta, and practically all of the lifting impulse will be generated by the gas pressure. 
     When the vehicle protection apparatus  1000  forms part of a land-based vehicle, it mitigates/prevents the damage caused to a vehicle by an explosion by counteracting the forces generated by the explosion and stabilizing the vehicle in response to the explosion. It may, advantageously, enable injury to the vehicle&#39;s occupants to be prevented or limited and enable the vehicle to remain upright and in fighting condition. This is explained in further detail below. 
     The vehicle protection apparatus  1000  illustrated in  FIG. 7  may be applied to a vehicle during manufacture or post manufacture. The apparatus  1000  may, for example, be a kit of parts. The vehicle may be a land-based armoured vehicle. For example, the vehicle may be a civilian car, a modified sports utility vehicle, a lightweight Special Forces vehicle or a larger military armoured vehicle such as a personnel carrier or a tank. 
     The apparatus  1000  comprises one or more linear rocket motors  434 / 534 , such as those described above in relation to  FIGS. 1 to 6 , one or more detectors  1006 , control circuitry  1012  and memory  1020 . 
     The control circuitry  1012  may, for example, be or comprise a single processor or multiple processors. 
     The control circuitry  1012  is configured to receive inputs from the one or more detectors  1006 . The control circuitry  1012  is configured to provide outputs to the one or more rocket motors  434 ,  534 . The control circuitry  1012  is also configured to write to and read from memory  120 . 
     It will be appreciated by those skilled in the art that  FIG. 7  is a functional schematic. In this regard, it should be recognised that intervening elements (such as additional circuitry) may be positioned between the control circuitry  1012  and each of the one or more rocket motors  434 ,  534 , the one or more detectors  1006  and the memory  1020 . 
     The memory  120  is illustrated in  FIG. 7  as storing a computer program  1021  comprising computer program instructions  1022 . The computer program instructions  1022  control the operating of the apparatus  1000  when loaded into the control circuitry  1012 . 
     The computer program  1021  may arrive at the apparatus  1000  via any suitable delivery mechanism  1026 . The delivery mechanism  1026  may be, for example, a (non-transitory) computer-readable storage medium, a computer program product, a memory device for a record medium such as a CD-ROM or DVD. The delivery mechanism may be a signal configured to provide the transfer the computer program instructions  1022 . 
     In an alternative implementation, the control circuitry  1012  and/or the memory  1020  may be provided by a dedicated application specific integrated circuit (ASIC). In such an implementation, it may be that no computer program is required. 
     When the apparatus  1000  is for a land-based vehicle, the detectors  1006  are detectors for detecting that an explosion has occurred local to (for example, underneath) a vehicle. The detectors  1006  may be any type of detectors and may, for example, include: one or more pressure detectors, one or more temperature detectors and/or one or more light detectors. 
     The pressure detectors may, for example, be piezoelectric pressure detectors. Advantageously, piezoelectric pressure detectors operate effectively in adverse weather and ground conditions. 
     Alternatively or additionally, the detectors  1006  may include one or more break wire detectors. An explosion may cause a circuit of such a break wire detector to break, causing the break wire detector to provide an input to the processor  12 . 
     Alternatively or additionally, the detectors  1006  may include one or more ionisation detectors for detecting ionised particles that result from an explosion. 
     Alternatively or additionally, the detectors  1006  may comprise one or more electromagnetic pulse detectors for detecting an electromagnetic pulse resulting from an explosion. 
     Alternatively or additionally, the detectors  1006  may comprise one or more accelerometers and/or one or more gyroscopes. 
     In operation, when an explosion occurs local to a land-based vehicle (such as underneath the vehicle), the explosion causes a blast shockwave. The detectors  1006  detect that an explosion has occurred local to the vehicle and provide inputs to the control circuitry  1012  which are indicative that an explosion has occurred. The control circuitry  1012  analyses the inputs provided by the detectors  1006  and determines than an explosion has occurred. The control circuitry  1012  then responds to the inputs provided by the detectors  1006  by causing the linear rocket motors  434 ,  534  to apply a groundwards force to the vehicle. The application of the groundwards force to the vehicle urges the vehicle towards ground and mitigates the upward forces generated by the blast shockwave from the explosion. Advantageously, this may enable the vehicle to remain upright and in fighting condition. 
     As explained above, the vehicle protection apparatus  1000  may also be for vehicles which are not land-based such as aircraft. The aircraft may, for example, be a helicopter. The aircraft may be operated by at least one pilot. The aircraft may be manned in that there is at least one pilot present in the aircraft. Alternatively, the aircraft may be unmanned and the pilot may be located remotely from the aircraft. 
     If the vehicle protection apparatus  1000  is for an aircraft, the one or more rocket motors  434 ,  534 , control circuitry  1012  and the memory  1020  may be similar to those described above in the context of the application of the apparatus  1000  to a land-based vehicle. The detectors  1006  may, however, be different. For example, the detectors  1006  may be for detecting the proximity of the aircraft to terrain or water. The detectors  1006  may, for example, comprise one or more altimeters, and/or one or more radar arrangements. The detectors  1006  may also comprise one or more engine failure detectors and/or one or more fuel gauges. 
     In operation, the one or more detectors  1006  may detect that an aircraft has entered a state in which an upwards force is required, or likely to be required in due course. For example, this could be because an altimeter or a radar arrangement has detected that the aircraft is flying too close to terrain or water. It may be because the rate of descent is above a threshold value and the altitude of the aircraft is below a threshold value. Alternatively, it could be because an engine of the aircraft, or an aspect of an engine of the aircraft, has failed. Alternatively, it could be because the aircraft has run out of fuel. 
     The inputs provided by the detectors  1006  are analysed by the control circuitry  1012  to determine when to cause an upwards force to be provided to the aircraft. This may be immediately, or after a period of time has elapsed. 
     At an appropriate point in time, the control circuitry  1012  causes the one or more rocket motors  434 / 534  to apply an upwards force to the aircraft. The upwards force is applied when the one or more rocket motors  434 / 534  eject gas towards ground. 
     The upwards force may, for example, be applied in response to detection of a potential collision by the detectors  1006 . The potential collision could, for example, be potential controlled or uncontrolled flight into terrain. 
     The application of the upwards force reduces the rate of descent of the aircraft and may, depending upon the aircraft, alter the pitch of the aircraft. Alternatively, the application of the upwards force may prevent a collision, or reduce the severity of the collision. 
       FIG. 8  illustrates a perspective view of an example of a, self-propelled, land-based vehicle that comprises the apparatus  1000  illustrated in  FIG. 7 . In this example, the vehicle is a lightweight Special Forces vehicle.  FIG. 9  illustrates a side view of the vehicle  2 . 
     The vehicle  2  further comprises a body  100  and wheels  28 . The illustrated vehicle  2  comprises four wheels  28 , but in other implementations of the invention, the vehicle  2  may include a different quantity of wheels and/or may include tracks. The reference numerals  3 ,  4 ,  5 ,  6  and  7  in  FIG. 8  designate the front, rear, first side, second side and underside of the vehicle  2  respectively. 
     The vehicle  2  has an occupant compartment  109  comprising three regions  106 ,  107  and  108  for housing occupants of the vehicle  2 . The first region  106  comprises two front facing seats  7   a ,  7   b , one of which may be for the driver of the vehicle  2 . The second region  107  of the vehicle  2  is located behind the first region  106  and comprises six seats in the illustrated example, three of which face towards the first side  5  of the vehicle  2  and three of which face towards the second side  6  of the vehicle  2 . The seats facing the second side  6  of the vehicle  2  are labelled with the reference numerals  8   a ,  8   b  and  8   c  in  FIG. 8 . The third region  108  is located behind the second region  107  and comprises a further seat  9  facing towards the rear  4  of the vehicle. 
     The vehicle  2  further comprises a vehicle support structure  10   a  in the form of a roll cage. The support structure  10   a  comprises a plurality of upwardly extending supports  11   a ,  11   b ,  11   c ,  11   d ,  11   e ,  11   f ,  11   g ,  11   h  and  11   i . Each of the supports  11   a - 11   i  is substantially vertical in the illustrated example. The two front facing seats  7   a ,  7   b  are connected to first and second supports  7   a ,  7   b . The three seats facing the first side  5  of the vehicle  2  are connected to third, fourth and fifth supports  11   c ,  11   d ,  11   e . The three seats  8   a - 8   c  facing the second side  6  of the vehicle  2  are also connected to the third, fourth and fifth supports  11   c ,  11   d ,  11   e . The seat  9  facing the rear  4  of the vehicle  2  is connected to sixth and seventh supports  11   g ,  11   h.    
     Each of the seats is connected to its support(s) using at least one spring. If and when the rocket motors  534   a ,  534   b ,  534   c  are activated, a groundwards force is applied to the vehicle  2 . This force is applied through the supports  11   a - 11   i , causing the supports  11   a - 11   i  and other aspects of the vehicle  2  to move groundwards. The springs which connect the seats to the supports  11   a - 11   i  enable the seats to remain in substantially the same position (or, at least, to move to a lesser extent than the supports  11   a - 11   i ), which keeps movement of any occupants in the vehicle  2  to a minimum and helps to reduce/prevent injury to those occupants. 
     Three rocket motors  534   a ,  534   b ,  534   c , and their respective casings  540   a ,  540   b ,  540   c , form part of the support structure  10   a . The support structure  10   a  and the rocket motor casings  540   a ,  540   b ,  540   c  therein form a load bearing structural element of the vehicle  2 , such that when the vehicle  2  is in motion and the rocket motors  534   a ,  534   b ,  534   c  are inactive, the structure  10   a  and the casings  540   a ,  540   b ,  540   c  therein bear an inertial load which enables the vehicle to function as a moving vehicle. The inertial load results from movement of the vehicle  2  and is therefore generated (at least in part) by the vehicle  2 . 
     The expression “the rocket motors  534   a ,  534   b ,  534   c  are inactive” is intended to mean that the propellent inside the rocket motors  534   a ,  534   b ,  534   c  has not been ignited and the rocket motors  534   a ,  534   b ,  534   c  are not providing a groundwards force in response to detection of an explosion. The motion of the vehicle  2  is therefore being caused by a source that is different from the rocket motors  534   a ,  534   b ,  534   c , such as an internal combustion engine of the vehicle  2 . 
     In the illustrated example, if the support structure  10   a  were not present, the vehicle  2  would not be able to function as a moving vehicle because an essential load bearing part of the vehicle  2  would not be present. 
     In the example illustrated in  FIG. 8 , linear rocket motors  534   a ,  534   b ,  534   c  are located above the first and second regions  106 ,  107  and their casings are integrally formed into the vehicle support structure  10   a . The linear rocket motors  534   a ,  534   b ,  534   c  have the same form as the linear rocket motor  534  illustrated in  FIG. 6 , but in other implementations some or all of them may alternatively have the structure of the linear rocket motor  434  illustrated in  FIGS. 1 to 5 . 
     When the rocket motors  534   a ,  534   b ,  534   c  are activated by the control circuitry  1012 , an efflux which is directed away from ground is generated which causes a groundwards force to be applied to the vehicle  2 . 
       FIG. 10  illustrates an aircraft  20  in the form of a self-propelled helicopter which comprises a body/fuselage  200 , a vehicle support structure  10   b  and the apparatus  1000  illustrated in  FIG. 7 . The body/fuselage  200  defines an internal enclosure for housing occupants of the helicopter  20 . The vehicle support structure  10   b  comprises rocket motors  534   d  and  534   e . The structure  10  and the casings  540   d ,  540   e  of the rocket motors  534   d ,  534   e  therein are arranged to sustain an inertial load generated, at least in part, by the aircraft/helicopter  20  when the rocket motors  534   d ,  534   e  are inactive. 
     The inertial load may be generated, at least in part, by the fuselage  200  of the helicopter  20 . In this example, the inertial load is generated, at least in part, by the mass of the helicopter  20 . The inertial load may, for instance, be a gravitational load. A gravitational load is a type of inertial load that is generated by the mass of a body (such as the fuselage  200 ) and the Earth&#39;s gravitational pull. Other types of inertial loads are also generated by the mass of a body (such as the fuselage  200 ) but the source of acceleration is different from the Earth&#39;s gravitational pull. 
     The inertial load may, for instance, result from the helicopter  20  being positioned stationary on ground, from upwards movement of the helicopter  20  during take-off or from the helicopter  20  interacting with ground during landing. 
     The expression “the rocket motors  534   d ,  534   e  are inactive” is intended to mean that the propellant inside the rocket motors  534   d ,  534   e  has not been ignited and the rocket motors  534   a ,  534   b ,  534   c  are not providing an upwards force to prevent/mitigate excessively rapid descent of the helicopter  20 . 
       FIG. 11  illustrates the support structure  10   b  in more detail. The support structure  10   b  comprises a first helicopter skid  22   a  and a second helicopter skid  22   b . The first and second helicopter skids  22   a ,  22   b  are connected by the first and second crossbars  21   a ,  21   b . Each of the first and second crossbars  21   a ,  21   b  are connected to an underside  207  of the body/fuselage  200  of the helicopter  20 . 
     It can be seen from  FIG. 11  that the casings  540   d ,  540   e  of the rocket motors  534   d ,  534   e  are integrally formed into the support structure  10   b . In this example, the casings  540   d ,  540   e  of the rocket motors  534   d ,  534   e  are integrated into the first and second skids  22   a ,  22   b  in such a way that the bases  535   d ,  535   e  of the rocket motors  534   d ,  534   e  face upwardly. 
     Reference numeral  536   d  denotes an inwardly facing side wall of the rocket motor  534   d  integrated into the first skid  22   a  and the reference numeral  536   e  denotes an outwardly facing side wall of the rocket motor  534   e  that is integrated into the second skid  22   b . The wall of each rocket motor  534   d ,  534   e  that comprises the exit apertures faces downwards. This means that when each rocket motor  534   d ,  534   e  is activated by the control circuitry  1012 , a groundwards efflux is generated which causes an upwards force to be applied to the body of the aircraft  200 . 
     The support structure  10   b  is a skid structure that, together with the casings  540   d ,  540   e  of the rocket motors  534   d ,  534   e  therein, is arranged to sustain an inertial load generated by the mass of the (body  200  of the) helicopter  20 . The inertial load may, for instance, be a gravitational load generated by the mass of the helicopter  20 . 
       FIGS. 12 to 14  illustrate an alternative example  10   c  of the vehicle support structure illustrated in  FIGS. 10 and 11 . In the vehicle support structure  10   c  illustrated in  FIGS. 12 to 14 , the first and second crossbars  23   a ,  23   b  each comprise first and second arms which attach to the casing  540   f  of a rocket motor  534   f  (and therefore to a skid of a helicopter). 
     As in the  FIG. 11  example, the base  535   f  of the rocket motor  534   f  faces upwardly and the wall comprising the exit apertures faces downwardly. Reference numeral  536   f  in  FIG. 12  denotes an inwardly facing side wall of the support structure  10   c.    
       FIG. 13  illustrates a magnified view of the area labelled with the reference numeral  50  in  FIG. 12 .  FIG. 14  illustrates a cross-sectional view of the second crossbar  23   b  and the rocket motor  534   f  illustrated in  FIG. 12 . 
     The first and second crossbars  23   a ,  23   b  have the same structure. It can be seen in  FIG. 13  that the second crossbar  23   b  has a first arm  24   a  which connects to a first connection point  510  on the upwardly facing base  535   f  of the rocket motor  534   f . A second arm  24   b  of the crossbar  23   b  connects to a second connection point  512  on an inwardly facing side wall  536   f  of the rocket motor  534   f . In  FIG. 14 , the reference numerals  537   f  and  543   f  denote an outwardly facing side wall and a downwardly facing wall (comprising exit apertures) respectively. 
       FIG. 15  illustrates a perspective view of a vehicle for transporting goods (and not people) in the form of a pallet  600 . The pallet  600  comprises the apparatus  1000  illustrated in  FIG. 7 . 
     Cartesian co-ordinate axes  650  comprising x, y and z axes are illustrated in  FIG. 15 . A length dimension L of the pallet  600  is aligned with the y-axis, a width dimension W of the pallet  600  is aligned with the x-axis, and a depth dimension D of the pallet  600  is aligned with the z-axis. The z-axis is directed out of the page in  FIG. 15 . 
     The pallet  600  comprises has a support structure  10   d , which in the example illustrated in  FIG. 15  includes a plurality of elongate members  611 - 623  extending in the width dimension W of the pallet  600  and at least one transverse elongate member  624  extending in the length L dimension. In the example illustrated in the figures, a transverse elongate member  624  is positioned beneath the plurality of elongate members  611 - 623  (see  FIGS. 16A and 16B ). 
     The pallet  600  illustrated in  FIG. 15  has an upper surface  602  and an underside  604 . The outer extremities of the pallet  600  are defined by the first, second, third and fourth edges  605 - 608  of the pallet  600 . In the illustrated example, the upper surface  602  of the pallet  600  is generally rectangular in shape, but it may be different in other examples. For instance, it may be generally square in shape. 
     A plurality of linear rocket motors may be integrated into the support structure  10   d  of the pallet  600 .  FIG. 16A  illustrates the underside  604  of a first example of a pallet  600  which includes first, second, third and fourth linear rocket motors  534   a - 534   d . In this example, the linear rocket motors  534   a - 534   d  are those illustrated in  FIG. 6 , but in other examples they could have an alternative form, such as that illustrated in  FIGS. 1 to 5 . 
     The first and third linear rocket motors  534   a ,  534   c  extend along the length dimension L of the pallet  600  at the second and fourth edges  606 ,  608  of the pallet  600 . The second and fourth linear rocket motors  534   b ,  534   d  extend along the width dimension W of the pallet  600  at the first and third edges  605 ,  607  of the pallet  600 . 
     The linear rocket motors  534   a - 534   d  are arranged such that their bases  535  face upwardly and the wall  443   a - 443   d  of each linear rocket motor  534   a - 534   d  that comprises the exit apertures  501  faces downwards. 
     The pallet  600  may be for use in supplying military equipment, such as logistical equipment and/or munitions. The equipment may be positioned on the upper surface  602  of the pallet  600  and secured in place using one or more nets, for instance. In use, the pallet  600  may be dropped from an aircraft to ground in order to provide the equipment on the pallet  600  to ground forces. 
     The casings  540  of the linear rocket motors  534   a - 534   d  are integrally formed into the support structure  10   d  of the pallet  600 . The support structure  10   d , including the casings  540  of the linear rocket motors  534   a - 534   d  therein, is arranged to sustain an internal load generated by the mass of the pallet  600  (while the linear rocket motors  534   a - 534   d  are inactive). The internal load may, for example, be a gravitational load generated by the mass of the pallet  600  when it is dropped. 
     After the pallet  600  has been dropped, the control circuitry  1012  may activate the linear rocket motors  534   a - 534   d , generating a downwards efflux and causing an upwards force to be applied to the pallet  600 . This causes the rate of descent of the pallet  600  to slow before it reaches the ground, preventing goods that are being transported on the pallet  600  from being destroyed/damaged when the pallet  600  impacts the ground. 
     The example illustrated in  FIG. 16B  is the same as that illustrated in  FIG. 16A , except that it includes a further linear rocket motor  534   e  positioned along a central portion of the pallet  600  and extending in the width dimension W. The addition of a further rocket motor  534   e  enables a greater upwards force to be generated and may improve the structural integrity of the pallet  600 . In practice, a pallet  600  could include any number of linear rocket motors  534   a - 534   e.    
     Features described in the preceding description may be used in combinations other than the combinations explicitly described. 
     Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. 
     Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not. 
     Where elements have been defined or described as being “connected” to one another, this should be interpreted to cover i) those elements may directly connected together (with no intervening elements) and ii) those elements being connected together via intervening elements. 
     Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.