Jettisonable aerodynamic control surfaces

Abstract: A flight vehicle includes a fuselage 10 having a consumable fuel supply 18,12, main wings 12 each with an elevon 14 and a pair of jettisonable foreplanes 16. The foreplanes provide lift at take-off and during transonic flight and, at higher supersonic speeds they are jettisoned.

Description: This invention relates to flight vehicles and to foreplane assemblies for such vehicles. In particular, though not exclusively, this invention relates to recoverable, winged launch vehicles. Examples of such vehicles include a single stage to orbit (SSTO) hydrogen-fuelled, recoverable, winged launch vehicle, and the first stage of a two stage to orbit (TSTO) vehicle. Such vehicles must be controllable in wing-borne flight over a very wide range of speed, extending from subsonic to hypersonic flight, with adequate allowances for manoeuvres and for countering gusts. These types of launch vehicle usually require a wide range of movements of the elevons or other pitch control surfaces because of the following inherent design features and aerodynamic characteristics. The launch vehicles have a voluminous fuselage to enclose the large tanks necessary because of the relatively low density of liquid hydrogen fuel, and relatively small wings equipped with elevons. Although the conventional rearward (i.e. stable) shift of the aerodynamic centre occurs at transonic speed, a much larger forward (i.e. unstable) movement occurs with increasing supersonic speed into the hypersonic range due to diminishing wing lift slope and increasing dominance of fuselage lift, as illustrated in Figure 2 of the accompanying drawings. Also, the centre of gravity shifts rearwardly on ascent because hydrogen propellant is consumed from the tanks in the front fuselage, and the dominant fixed masses (i.e. the propulsion system) of the vehicle are inevitably at the rear of the vehicle. The rearward shift of the centre of gravity reinforces the forward unstable movement of the aerodynamic centre as the Mach number increases supersonically. As shown in Figure 3 of the accompanying drawings, the effectiveness of the pitch control surfaces (i.e. the elevons on the wing) diminishes with increasing supersonic speed to less than 10% of their subsonic power at Mach numbers approaching 5. The above effects combine to require large upward deflections of elevons at subsonic and transonic speeds and large downward deflections at high supersonic/hypersonic speeds. The large control deflections produce high hinge moments, requiring powerful, heavy actuators, with a consequent increase in mass, storage volume, power consumption, and expense. We have studied the possibility of using all-moving foreplanes, potentially a more effective control at supersonic speeds, but we have found that they are impractical. This is due to the severe heating effects on re-entry because of their small leading edge radius (the heating rate varies inversely as the square root of the leading edge radius) and also to their destabilising effect. All-moving foreplanes mounted by a spigot bearing on the vehicle would require large angular travel to negate their nose-up pitching moment at high incidence on re-entry, and this would mean that, on re-entry the spigot bearing region would be exposed to full stagnation heating. GB-A-2187421 shows a "canard" configuration in which the forebody of a flight vehicle is provided with three all-moving foreplanes. The Applicants see a need for an arrangement which allows the full range of positive and negative pitch control moments to be imparted to the flight vehicle which avoids or at least reduces the problems inherent in the existing proposals. Accordingly, this invention provides a flight vehicle, comprising a main body portion, main wing means provided at an aft end region of said main body portion, foreplane means located at a forward end region of said main body portion, wherein said vehicle further includes aerodynamic control means for effecting control in at least the pitch sense, and jettisoning means operable for Jettisoning said foreplane means. The invention also provides a foreplane assembly for a flight vehicle, said vehicle including a main body portion, main wing means and aerodynamic control means for effecting control in at least the pitch sense, said foreplane assembly including foreplane means, anchorage means for being associated with said flight vehicle and for supporting said foreplane means in a predetermined orientation, and jettisoning means for jettisoning said foreplane means from said anchorage means. The invention will now be described by way of non-limiting example, reference being made to the accompanying drawings in which:- Figure 1 is a schematic view of one example of flight vehicle fitted with jettisonable foreplanes in accordance with the invention; Figures 2 and 3 are graphs illustrating the variation with Mach number of the position of the aerodynamic centre, and the effectiveness of the pitch control surfaces respectively, for a flight vehicle of the general type shown in Figure 1; Figures 4a and 4b are detail plan views of one of the jettisonable foreplane assemblies of the vehicle of Figure 1 in the installed and post-jettison positions respectively; and Figure 5 is a transverse sectional view through the jettisonable foreplane assembly illustrated in Figure 4a. Referring to Figure 1, the reusable flight vehicle includes a fuselage 10, main wings 12 each having an elevon 14, and a pair of jettisonable foreplanes 16 projecting laterally from a nose region of the fuselage. The fuselage 10 houses a liquid hydrogen tank 18, a payload bay 20, a liquid oxygen tank 22 and the propulsion system 24. Referring now to Figures 4a, 4b and 5, each jettisonable foreplane assembly comprises a foreplane 16 which, when attached to the flight vehicle, is set at a fixed incidence angle, typically O° . The foreplane 16 is releasably secured to an anchorage 26 on board the vehicle by means of a releasable spring collet arrangement 27 within the anchorage 26 which engages the free end 28 of the actuator rod 29 of a telescopic jettison gun 30. Adjacent the fuselage surface, the anchorage 26 includes a bearing 31 which slidably surrounds the exposed end of the gun 30. The body of the gun is secured to the foreplane 16 and loads are transmitted via the gun reaction region 34 shown in Figure 5. The body of the gun forms part of the load-bearing structure (i.e. resisting bending) in the unfired condition. The actuator rod 29 is made up of telescopically movable sections and the actuator rod is moved to its fully extended position by means of a gun cartridge 32. Forwardly of the jettison gun 30, the foreplane includes an anti-rotation spigot 36 which engages an associated recess 38 in the fuselage 10 of the flight vehicle to prevent rotation of the foreplane 16. The anchorage 26 on the fuselage includes a housing defining a bore 37 which receives the spring collet arrangement 27 and, inboard of the arrangement 27, a reaction pad 40. Detonation of the gun cartridge 32 extends the actuator rod 29 so that its free end disengages from the spring collet arrangement 27 and impacts the reaction pad 40. On disengagement of the free end of the actuator rod 29, the spring collet arrangement collapses to release the actuator rod so that jettisoning can occur. When the free end of the actuator rod 29 impacts the reaction pad 40, the foreplane is jettisoned laterally away from the fuselage in the direction of the arrow in Figure 4b and the body of the gun 30 slides out of the bearing 31. A spring-loaded closing panel 42 is provided adjacent the outer end of the bore 37 and moves to close the bore when the foreplane has been jettisoned. A similar arrangement may be provided for the recess 38 associated with the anti-rotation spigot 36. In use the foreplanes 16 will be jettisoned in a controlled manoeuvre, programmed into the flight control system of the flight vehicle, to ensure both a safe separation trajectory without the risk of collision with the vehicle structure and an acceptably small vehicle disturbance due to the sudden change in pitching moment. Firing of each jettison cartridge may be energised electrically by a pre-programmed signal from the flight control system. On firing (Figure 4b) the explosive gases force the inner telescopic piston of the jettison gun to extend. Immediately after release, the spring-loaded closing panel 42 closes the end of the bore 37 and (if provided) a similar cover closes the spigot recess. This is primarily to prevent local cavity heating on re-entry of the vehicle into the atmosphere, from orbit. At take-off, and during transonic flight, the foreplanes provide positive lift, augmenting lift for take-off and relieving the download on the elevons 14 in transonic flight. At higher supersonic speed, before their destabilising effect becomes detrimental, they are jettisoned.

Claims: A flight vehicle, comprising a main body portion (10), main wing means (12) provided at an aft end region of said main body portion (10), foreplane means (16) located at a forward end region of said main body portion (10), characterised in that said vehicle further includes aerodynamic control means (14) for effecting control in at least the pitch sense, and Jettisoning means (30) operable for jettisoning said foreplane means (16). A flight vehicle according to Claim 1, wherein said foreplane means comprises a pair of foreplanes (16) extending transversely one from either side of said flight vehicle. A flight vehicle according to Claim 2, wherein each of said foreplanes (16) is set at a fixed incidence angle. A flight vehicle according to any of the preceding claims, wherein said aerodynamic control means comprises aerodynamic control surface means (14) associated with said main wing means (12). A flight vehicle according to any preceding Claim, including storage means (18) for storing a consumable or Jettisonable payload in the main body portion (10) intermediate said foreplane means (16) and said main wing means (12), said storage means (18) being positioned such that consumption or jettisoning of said payload causes a rearward shift in the centre of gravity of said flight vehicle. A foreplane assembly for a flight vehicle, said vehicle including a main body portion (10), main wing means (12) and aerodynamic control means (14) for effecting control in at least the pitch sense, said foreplane assembly including foreplane means (16), anchorage means (26) for being associated with said flight vehicle and for supporting said foreplane means (16) in a predetermined orientation, and characterised by jettisoning means (30) for jettisoning said foreplane means (16) from said anchorage means (26). A foreplane assembly according to Claim 6, wherein said jettisoning means comprises a telescopically movable ram actuator (30). A foreplane assembly according to Claim 7, wherein one end (34) of said ram actuator (30) is secured to said aerodynamic control surface means (16) and the other end (28) thereof is releasably secured within said anchorage means (26). A jettisonable control surface assembly according to Claim 8, wherein said other end (28) of said ram actuator (30) is releasably secured within said anchorage means (26) by spring-biased collect means (27). A jettisonable control surface assembly according to any of Claims 6 to 9, further including panel means (42) movable in use to render the surface of the flight vehicle substantially smooth and continuous following jettison of said aerodynamic control surface means (16).

Inventors: BURNS BRYAN ROBERT ALEXANDER, DALE NICHOLAS CHARLES, HOPWELL BRIAN LAWRENCE, BURNS, BRYAN ROBERT ALEXANDER, DALE, NICHOLAS CHARLES, HOPWELL, BRIAN LAWRENCE
Applicants: BRITISH AEROSPACE, BRITISH AEROSPACE PUBLIC LIMITED COMPANY
Application year: 1990
Main classification: B64C5
IPC codes: B64C5