Abstract:
A nose cap and control strut assembly for supersonic aircraft is disclosed. In one embodiment, the nose cap extends forward from the nose of the aircraft to deflect shock waves and decrease draft during supersonic flight. In another embodiment, control struts extending from the nose of the aircraft have control surfaces which provide yaw and pitch control for the aircraft. The control struts may be rotatable around axes substantially parallel with the longitudinal axis of the aircraft. The control struts may also be retractable into the aircraft. The nose cap may be mounted at the forward ends of the control struts in such a manner that the nose cap remains in a stationary position with respect to the aircraft when the control struts are rotated.

Description:
FIELD OF THE INVENTION 
     The present invention relates to supersonic aircraft, and more particularly relates to extendable and/or rotatable nose cap and control strut assemblies for supersonic aircraft. 
     BACKGROUND INFORMATION 
     Supersonic and hypersonic aircraft tend to have low leading edge sweeps. Such low leading edge sweeps are beneficial for supersonic and hypersonic flight, but they can generate unwanted supersonic drag. An approach to reduce such drag would be to add a cap extending from the nose of the aircraft which deflects supersonic bow shock waves away from the aircraft. It would also be desirable to provide control struts for such an extended nose cap including control surfaces which can provide yaw and pitch control for the aircraft. 
     SUMMARY OF THE INVENTION 
     An embodiment of the present invention provides a nose cap for supersonic aircraft which extends forward from the nose of the aircraft to deflect shock waves and decrease drag during supersonic flight. Another embodiment of the invention provides control struts extending from the nose of the aircraft having control surfaces which may provide yaw and pitch control for the aircraft. The control struts may be rotatable around axes substantially parallel with the longitudinal axis of the aircraft. The control struts may also be retractable into the aircraft. The nose cap may be mounted at the forward ends of the control struts in such a manner that the nose cap remains in a stationary position with respect to the aircraft when the control struts are rotated. 
     An aspect of the present invention is to provide an aircraft nose cap and control strut assembly comprising at least one rotatable control strut extending from a nose of the aircraft, and a nose cap mounted at a forward end of the rotatable control strut(s). 
     Another aspect of the present invention is to provide an aircraft nose cap and control strut assembly comprising at least one contoured control strut including a control surface extendable from a nose of the aircraft, and a nose cap mounted at a forward end of the contoured control strut(s). 
     A further aspect of the present invention is to provide an aircraft nose cap and control strut assembly comprising at least one contoured control strut including a control surface extendable from a nose of the aircraft and rotatable around an axis substantially parallel with a longitudinal axis of the aircraft, and a nose cap mounted at a forward end of the control strut(s). 
     These and other aspects of the present invention will be more apparent from the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partially schematic side view of a supersonic aircraft including a movable nose cap and control strut assembly in a stowed position in accordance with an embodiment of the present invention. 
         FIG. 2  is an enlargement of the nose portion of the supersonic aircraft shown in  FIG. 1 . 
         FIG. 3  is a partially schematic top view of the supersonic aircraft of  FIG. 1 , illustrating the movable nose cap and control strut assembly in the stowed position. 
         FIG. 4  is an enlargement of the nose portion of the supersonic aircraft shown in  FIG. 3 . 
         FIG. 5  is a partially schematic side view of the supersonic aircraft shown in  FIGS. 1 and 3 , illustrating the movable nose cap and control strut assembly in an extended or deployed position. 
         FIG. 6  is an enlargement of the nose portion of the supersonic aircraft shown in  FIG. 5 . 
         FIG. 7  is a partially schematic top view of the supersonic aircraft of  FIG. 5 , illustrating the movable nose cap and control strut assembly in the extended position. 
         FIG. 8  is an enlargement of the nose portion of the supersonic aircraft shown in  FIG. 7 . 
         FIG. 9  is a partially schematic top view of the nose portion of a supersonic aircraft including an extended nose cap and control strut assembly in accordance with an embodiment of the present invention. 
         FIG. 10  is a cross sectional view of the control struts taken through section A-A of  FIG. 9 . 
         FIG. 11  is a cross sectional view of the control struts taken through section B-B of  FIG. 9 . 
         FIG. 12  is a partially schematic top view of the nose portion of the supersonic aircraft of  FIG. 9 , with the control struts rotated 90 degrees from their positions shown in  FIG. 9 . 
         FIG. 13  is a cross sectional view of the control struts taken through section A-A of  FIG. 12 . 
         FIG. 14  is a cross sectional view of the control struts taken through section B-B of  FIG. 12 . 
         FIG. 15  is a partially schematic top view of the nose portion of a supersonic aircraft including an extended nose cap and control strut assembly in accordance with another embodiment of the present invention. 
         FIG. 16  is a cross sectional view of the control struts taken through section A-A of  FIG. 15 . 
         FIG. 17  is a cross sectional view of the control struts taken through section B-B of  FIG. 15 . 
         FIG. 18  is a partially schematic top view of a portion of the supersonic aircraft of  FIG. 15 , with the control struts rotated 90 degrees from their positions shown in  FIG. 15 . 
         FIG. 19  is a cross sectional view of the control struts taken through section C-C of  FIG. 18 . 
         FIG. 20  is a cross sectional view of the control struts taken through section D-D of  FIG. 18 . 
         FIG. 21  is a front view of the nose of the supersonic aircraft of  FIG. 15 , illustrating the connection of the control struts to the aircraft nose by rotatable turntables. 
         FIG. 22  is a front view of the nose of the supersonic aircraft of  FIG. 18 , illustrating a 90 degree rotation of each control strut and corresponding turntable in comparison with the control strut and turntable orientations shown in  FIG. 21 . 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1-8  illustrate a supersonic aircraft  10  including a nose portion  12 , tail  14  and engines  16 . The supersonic aircraft  10  includes a movable nose cap and control strut assembly  18  in accordance with an embodiment of the present invention. The movable nose cap and control strut assembly  18  includes a nose cap  20  and control struts  30   a  and  30   b.    
     In  FIGS. 1-4 , the nose cap  20  and control struts  30   a  and  30   b  are in a stowed or retracted position in which the control struts  30   a  and  30   b  are retracted into the nose  12  and the nose cap  20  is seated against the nose  12 . In  FIGS. 5-8 , the nose cap  20  and control struts  30   a  and  30   b  are extended to a deployed position extending from the nose  12  of the aircraft  10 . In the embodiment shown in  FIGS. 1-8 , two control struts  30   a  and  30   b  are attached to the nose cap  20 . Alternatively, any other suitable number of control struts may be used. 
     The nose cap  20  may have any desired shape which helps reduce supersonic drag. In the embodiment shown in the present figures, the nose cap  20  has a generally hemispherical shape. However, any other suitable shape may be used, preferably blunt nosed or other shapes which help reduce drag of the aircraft during supersonic flight. 
     The controls struts  30   a  and  30   b  are each rotatable around an axis that is substantially parallel with a longitudinal axis of the aircraft  10 . Each control strut  30   a  and  30   b  may rotate from about 1 to 360 degrees around its axis. For example, each control strut  30   a  and  30   b  may rotate from about 5 to about 180 degrees. In a particular embodiment, the control struts  30   a  and  30   b  rotate about 90 degrees. 
     In accordance with an embodiment of the present invention, in its extended position, the nose cap  20  does not rotate in relation to the nose  12  of the aircraft  10 . Thus, when the control struts  30   a  and  30   b  rotate, the nose cap  20  remains stationary. This may be accomplished by providing any suitable type of rotatable coupling between the nose cap  20  and each of the control struts  30   a  and  30   b.    
     The nose cap  20  mounted at the forward ends of the control struts  30   a  and  30   b  may be extendable any desired distance away from the nose  12  of the aircraft  10 . For example, the nose cap  20  may be extended a distance of least about 10 cm. In one embodiment, the nose cap  20  may be extendable a distance of at least about 1 m from the nose  12  of the aircraft  10 . Any suitable mechanism may be used to extend and rotate the control struts. For example, a conventional flap screwjack with extending rails (not shown) may be used to guide the control struts  30   a  and  30   b . In the embodiment shown in  FIGS. 1-8 , the control struts  30   a  and  30   b  are retractable into the nose  12  of the aircraft  10 . However, for some aircraft, it may be desirable to provide control struts which are permanently extended from the aircraft, or which only partially retract into the nose  12  of the aircraft  10 . 
     In accordance with an embodiment of the present invention, the control strut(s) may include control surfaces which may be used to provide yaw and pitch control for the aircraft  10 , for example, in the subsonic flight regime of the aircraft.  FIGS. 9-14  illustrate an embodiment in which control struts  32   a  and  32   b  include control surfaces  34   a  and  34   b .  FIG. 10  is a cross section taken through section A-A of  FIG. 9  corresponding to the elongated control surface sections  34   a  and  34   b  of the control struts. As shown in  FIG. 10 , the control surface sections  34   a  and  34   b  are non-circular and have elongated cross sections. For example, the control surface cross sections  34   a  and  34   b  may have aspect ratios X:Y of greater than about 2:1, for example, greater than about 3:1.  FIG. 11  is a cross sectional view of the control struts  32   a  and  32   b  taken through section B-B of  FIG. 9 . At this location, the control struts  32   a  and  32   b  have substantially circular cross sections. 
     The top view of the supersonic aircraft nose  12  illustrated in  FIG. 12  shows rotations of the control struts  32   a  and  32   b  90 degrees from their positions shown in  FIG. 9 . In the position shown in  FIG. 12 , the control surfaces  34   a  and  34   b  extend laterally. This is further illustrated in the cross sectional view of  FIG. 13 , taken through section C-C of  FIG. 12 . Comparing the orientation of the control surface sections  34   a  and  34   b  shown in  FIG. 13  with those shown in  FIG. 10 , it can be seen that each control strut has been rotated 90 degrees around its axis.  FIG. 14  is a cross section taken through section D-D of  FIG. 12 , further illustrating the circular cross sections of the control struts  32   a  and  32   b  near the aircraft nose  12 . 
       FIGS. 9-14  thus illustrate an embodiment of the control strut assembly which may be used for trimmed/controlled flight of the aircraft. The rotated control struts expose a sharp edged paddle near the front of the assembly exposed to the up-wash in front of the aircraft. This may be desirable because a sharp edge low aspect surface will provide aerodynamic control for a relatively small surface. The amount of yaw and pitch control is controlled by the amount of rotation of the control struts around their axes parallel to the centerline of the aircraft. 
       FIGS. 15-20  illustrate an extended nose cap and control strut assembly in accordance with another embodiment of the present invention. In this embodiment, the control struts  36   a  and  36   b  have elongated control surfaces extending along their entire lengths.  FIG. 16  is a cross sectional view of the control struts  36   a  and  36   b  taken through section A-A of  FIG. 15 , while  FIG. 17  is a cross sectional view of the control struts  36   a  and  36   b  taken through section B-B of  FIG. 15 . The control struts  36   a  and  36   b  maintain substantially the same elongated control surface cross sections having the aspect ratio X:Y along their lengths. 
     In  FIGS. 18-20 , the control struts  36   a  and  36   b  have been rotated 90 degrees from their positions shown in  FIGS. 15-17 . The 90 degree rotation R of the control struts  36   a  and  36   b  provides a substantially horizontal control surface at the nose of the aircraft  12  which can provide yaw and pitch control for the aircraft. 
       FIGS. 15-20  thus illustrate another embodiment of the control strut assembly which may be used for trimmed/controlled flight of the aircraft. The rotated control struts expose their sharp edges to the upwash in front of the aircraft to provide aerodynamic control. 
       FIGS. 21 and 22  illustrate details of the rotational connection between the control struts  36   a  and  36   b  and the nose  12  of the aircraft. The control strut  36   b  is mounted on a turntable  40   b  which rotates in the direction R with respect to the nose  12 . Similarly, the control strut  36   a  is mounted on a turntable  40   a  which is rotatable in the direction R with respect to the nose  12 . The turntables  40   a  and  40   b  are preferably flush with the surface of the nose  12 , and may be sealed against the surface of the nose  12 , in order to substantially prevent airflow between the inside and outside of the aircraft skin. In  FIG. 22 , the control struts  36   a  and  36   b , and their respective turntables  40   a  and  40   b , are rotated 90 degrees with respect to their positions shown in  FIG. 21 . 
     Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.