Note: Descriptions are shown in the official language in which they were submitted.
13DV-9152
HYPERSONIC FLIGHT VEHICLE
The United States Government has rights in this invention
pursuant to a contract between the U.S. Government and the
General Electric Company.
BACKGROUND OF THE INVENTIO~
The present invention relates generally to flight vehicles
and more particularly to an inlet for a hypersonic flight vehicle
~ngine.
At hypersonic Mach numbers (i.e., greater than Mach 5) a
flight vehicle having an air breathing engine requires an engine
inlet having a large air-capture region. In addition, hypersonic
flight vehicle engine design requires inlet surfaces to be three-
dimensionally-swept to reduce aerodynamic drag and friction
heating. Three-dimensionally-swept engine inlet designs can
produce non-planar ~low components reguiring a complex and
perhap~ impractical analysis of a three-dimensional airflow path.
This may be contrasted with non-hypersonic supersonic engines
having ramp inlet surfaces producing planar flow components
allowing a much easier analysis of a two-dimensional airflow
path. Furthermore, two-dimensional flow allows easier direct
, connect engine component testing ~which means testing an engine
;I component by duplicating its input conditions with some apparatus
`l~ without having to use the upstream engine components to produce
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such input conditions), such as testing an engine without its
large inlet by duplicating the two-dimensional airflow conditions
calculated at the engine throat. Finally, a hypersonic engine
design may introduce a pitch moment on the flight vehicle which
would require a constant trim such as from a drag-producing
control surface.
In describing the invention, the terminology ~caret-shaped
surface" will be used. For the purpose of this invention, a
"caret-shaped surface~ is defined as the surface of an isosceles
triangle which has been folded along its base altitude line to
form two mirror-image right triangles which meet along the
altitude line with an anhedral angle. To help visualize this
caret-shaped surface, one can cut an isosceles triangle out of a
piece of stiff paper, and crease the triangle along the altitude
line so that two mirror-image right triangles are superimposed on
each other. ~The steps up to now are identical to the beginning
~tep~ in making certain paper airplanes.~ I~ the bent isosceles
triangle is placed on the surface of a table, so that the legs of
the isosceles triangle rest on the table surface, the two right
triangle portions will form an anhedral angle at the altitude
line. The lower (inside) surface of the bent isosceles triangle
is a caret-shaped surface. The angle between the altitude line
(the crease line) and the airflow is the angle of attack of the
caret-shaped surface.
For unique combinations of hypersonic speed and angle of
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13DV-9152
attack (hereinafter referred to as i~predetermined operating
conditions~), as can be determined by those skilled in the art,
the above-defined caret-shaped surface will generate a plane
shock wave in the plane of its leading edges (the plane
containing the legs of the bent isosceles triangle which is also
the plane of the table surface) which leads to a uniform pressure
between the shock wave and the caret-shaped surface tthe lower
surface of the bent isosceles triangle) equal to the pressure
behind the shock in a two-dimensional wedge flow. Two-
dimensional wedge flow will be closely approximated fordeviations from the design hypersonic speed and angle of attack.
The caret shaped surface of the invention is the same as the
lower surface of the caret wing of the literature. Caret wings
are described in a paper by K. Kipke entitled ~Experimental
Investigations o~ Wave Riders in the Mach Number Range from 8 to
15~ published in AGARD HY~ersonic Boundary Layers and Flow Fields
~May, 1968), said paper hereby incorporated by reference.
SUMMARY OF THE INVENTION
It i5 an object of the invention to provide a flight vehicle
engine inlet having a large air-capture region.
It is another ob;ect of the invention to provide a
hypersonic flight vehicle engine inlet which is three-
dimensionally swept yet provides two-dimensional flow.
It is a further object of the invention to provide a
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hypersonic flight vehicle engine which provides a generally zero
pitch moment.
It is an additional object of the invention to provide a
hypersonic flight vehicle with an engine which provides the
vehicle with pitch maneuvering control.
In a first embodiment, the flight vehicle engine inlet of
the invention includes a first member, a second member, and an
aft portion. The first and second members each have at least a
partial generally caret-shaped surface portion and are positioned
to generally oppose each other across a capture region which at
least partially includes the two-dimensional wedge flows produced
by such caret surface portions. The aft portion joins the first
and second members and has an orifice forming the throat of the
engine inlet.
15In a second em~odiment, the hypersonic flight vehicle engine
inlet of the invention includes an upper member, a lower member,
and an aft portion. The upper member has a generally caret-
shaped lower sur~ace portion. The lower member has two inverted
- and transposed generally semi-caret-shaped upper surface
portions. The aft portion connects the upper and lower members
and has an orifice forming the throat of the engine inlet.
In a third embodiment, the hypersonic flight vehicle engine
of the invention includes the inlet of the previously-described
sPcond embodiment, a combustion chamber, fuel injectors, and an
~ 25 exhaust nozzls. The fuel injectors are positioned in the
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combustion chamber, and the combustion chamber is serially
connected to the inlet's aft portion. The exhaust nozzle is
serially connected to the combustion chamber and has generally
symmetric upper and lower segments.
In a fourth embodiment, the hypersonic flight vehicle of the
invention includes the engine of the previously-described thixd
embodiment and two swept wings attached to the engine inlet's
lower member wi~h the exhaust nozzle's upper and lower segments
each having an aft flap for pitch maneuvering control and with
the wings each having a mechanism for yaw and roll maneuvering
control.
Several benefits and advantages are derived from the
invention. The caret and semi-caret inlet surfaces provide a
three-dimensionally-swept and large air-volume-capturing
hypersonic engine inlet which produces two-dimensional wedge
~low. This allows easier analysis of a two-dimensional airflow
path and easier direct connect engine component testing. The
~ymmetriC upper and lower exhaust nozzle ssgments pr~vide
generally zero pitch moment. The aft flaps on the exhaust
nozzle's upper and lower segments provide an engine which
provides pitch maneuvering control.
BRIEF DESCRIPTION OF T~E DRAWINGS
The accompanying drawings illustrate several embodiments of
the present invention wherein:
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Figure 1 is a perspective view of the hypersonic flight
vehicle including its engine inlet;
Figure 2 is a cross-sectional side view of the hypersonic
engine; and
SFigure 3 is a front elevational view in perspective of the
hypersonic flight vehicle.
DETAILE~ DESCRIPTION OF THE INVENTION
The presént invention, as embodied in an engine inlet 10, a
hypersonic engine 12, and a flight vehicle 14, is illustrated in
Figures 1 through 3. The flight vehicle engine inlet 10 is
designed for hypersonic operation and includes a first or upper
member 16, a second or low~r member 18 (preferably, but not
necessarily, hàving two upper surface portions 26 and 28 to be
described later), and an aft portion 20.
15The inlet upper member 16 has a generally caret-shaped lower
sur~ace portion 22 and a contoured upper surface 24. The caret-
shaped lower sur~ace portion 22 has the shape of the lower
surface of a caret wing. As is known to those skilled in the
art, the three-dimensionally swept lower surface of a caret wing
will produce a two-dimensional wedge flow below such lower
surface at predetermined operating conditions of angle of attack
and hypersonic speed (typically chosen as the vehicle's cruise
speed). ~he upper surface 24 of the engine inlet 10 also serves
as part of the vehicle's fuselage, and between the upper surface
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24 and the caret-shaped lower surface portion 22 of the engine
inlet 10 may be located the cockpit (for a manned vehicle) and at
least part of a payload bay.
The inlet lower member 18 has two inverted and transposed
generally semi-caret-shaped upper surface portions 26 and 28
defined as follows: invert (turn upside down) the lower surface
of a caret wing to produce a caret-shaped upper surface, then
longitudinally cut this surface in half to produce two (mirror-
image) semi-caret-shaped upper surfaces, and then transpose
(switch positions without rotation) the two semi-caret-shaped
upper surfaces. The three-dimensionally swept semi-caret-shaped
upper surface portions 26 and 28 will produce a two-dimensional
wedge flow above such surface portions at predetermined operating
conditions of angle of attack and hypersonic speed (chosen to be
èqual to the angle of attack and hypersonic speed chosen for the
design of the caret-shaped lower sur~ace portion 22 of the inlet
upper member 16), as can be appreciatQd by those skilled in the
art. I~ an exemplary embodiment, the caret-shaped lower surface
portion 22 and the semi-caret-shaped upper surface portions 26
and 28 are disposed and oriented to equally compress their
respective two-dimensional flows at the throat 30 at the
predeter~ined hypersonic speed. Preferably, each semi-caret-
shaped upper surface portion 26 and 28 of the inlet lower member
18 is created from an inverted and transposed longitudinally-cut-
half of the caret-shaped lower surface portion 22 of the inlet
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13DV-9152
upper member 16. The semi-caret-shaped upper surface portions 26
and 28 are joined inboard to corresponding contoured lower
surface portions 32 and 34 of the inlet lower member 18, such
lower surface portions also serving as part of the vehicle's
fuselage and between such upper and lower surface portions may be
located at least part of the landing gear. The upper surface
portions 26 and 28 and the lower surface portions 32 and 34 are
joined outboard to corresponding generally-vertical raised ramp
portions 36 and 38 which help to control the amount of inlet air
lost to side spillage during off-design operation at lower Mach
numbers.
The inlet aft portion 20 connects together the upper 16 and
lower 18 inlet members and has an orifice defining the throat 30
o~ the engine inlet 10. The throat 30 receives at least a
portion of the two dimensional wedge flows produced by the inlet
upper 16 and lower 18 members. The upper 16 and lower 18 inlet
members are seen to generally oppose each other across an air
capture region 40 which is large in relation to the relative size
of the vehicle 14. A large capture area is needed at high
speeds. At lower speeds, at least some of the unneeded portion
o the inlet air is naturally spilled out the open side and
bottom portions of the engine inlet 10 reducing the need for an
engine with a variable forward inlet geometry.
For added compression needed at higher speeds, the aft
portion 20 of the engine inlet 10 also includes an upper
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transition ramp 42 and two lower transition ramps 44 and 46. The
upper transition ramp 42 extends from the caret-shaped lower
surface portion 22 of the inlet upper member 16 downward and aft
terminating at the throat 30. The lower transition ramps 44 and
46 (which may be integrally combined into a single ramp) extend
from a corresponding semi-caret-shaped upper surface portion 26
and 28 of the inlet lower member 18 upward and aft terminating at
the throat 30. The transition ramps, as can be appreciated by
those skilled in the art, turn the two-dimensional flow from the
coxresponding caret or semi-caret surface without affecting its
two-dimensional nature. The transition ramps not only add
compression but also allow the inlet throat 30 to have a
rectangular design shape which simplifies analysis and testing.
rectangular throat geometry also interfaces efficiently with
the downstream combustor portion 48 of the engine. Preferably,
the transition ramps are movable to ad;ust the height of the
rectangular-shaped throat. Having a variable-area rectangular
throat allows ad~ustment ~or dif~erent compression ratios needed
by the engine at different speeds during the flight, such as
increasing speed from Mach S to a speed of Mach 25 or 30. A
variable-area rectangular throat also permits use of variable
geometry in the combustor portion of the engine as might be
desirable for operation over a wide range of flight Mach numbers.
The hypersonic engine 12, preferably is a ramjet, scramjet,
hybrid or combined cycle or the like, and includes the
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previously-described inlet 10, a combustion chamber 48 serially
connected to the inlet aft portion 20, a plurality of fuel
injectors 50 disposed in the combustion chamber 48, and an
exhaust nozzle 52 serially connected to the combustion chamber
S 48. The exhaust nozzle 52 has symmetric upper 54 and lower 56
segments which together produce generally zero pitch moment. The
a~t portion 20 of the engine inlet 10 preferably contains
spaced-apart swept ribs 58. Such ribs 58 provide structural
sùpport and are located forward, proximate and across the width
of the throat 30. Additional fuel injectors (not shown) are
positioned in the inlet's aft portion 20, such as on the walls of
the ribs 58 and/or in their aft-facing base regions.
The hypersonic flight vehicle 14 includes the previously-
described engine 12 and two swept wings 60 and 62 attached to the
inlet lower member 18. The wings 60 and 62 have means for yaw
and roll vehicle maneuver control. Preferably such means include
cant~d vertical ~ins 64 and 66 Othar such means include roll-
control ~lap portions in the wings plu5 vert~cal fins with yaw-
control flap portions, reaction jets, and the like, as is known
to those skilled in the art. Vehicle pitch maneuver control is
provided by aft flaps 68 and 70 attached to the exhaust nozzle
upper 54 and lower 56 segments. At hypersonic speeds, pitch
maneuver control is achieved by turning an aft flap 68 or 70
inward into the nozzle exhaust region 72 as there may not be
enough air pressure for vehicle control in turning an aft flap
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13DV-9152
outward of the exhaust nozzle, especially if the outward region
is in t~e nshadow~ of the vehicle relative to the free air
stream. As a hypersonic vehicle needs large quantities of fuel
~as well as air), preferably conformal fuel tanks 74 are disposed
at least partially within the exhaust nozzle 52.
Preferably, the hypersonic flight vehicle 14 takes off from
a runway powered by take-off rockets 76 mounted on the sides of
the exhaust nozzle 52. When sufficient speed is reached for
ramjet or scramjet operation, the rockets 76 are shut down or
expended, and the previously-described engine 12 takes over to
power the flight vehicle 14 to hypersonic speeds. Other take-off
means include the vehicle riding piggy-back on a large
conventional-type supersonic aircraft or the vehicle having one
or more turbo;et~ in a combined or hybrid cycle design with the
engine of the invention, as can be appreciated by those skilled
in the art. When orbital operat$on o~ the flight vehicle 14 is
d~sired, the rock~ts 76 may be reignited, if necessary, to help
achieve final orbital velocity.
Typical design parameters, which have been subject to
computer simulations, include a predetermined hypersonic speed of
Mach 25, an inlet contraction (area) ratio of 30 to 1, transition
ramp angles of from 5 to 11 degrees, and an inlet leading edge
sweep angle of 77 degrees.
The foregoing description of several preferred embodiments
of the invention has been presented for purposes of illustration.
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13DV-9152
It is not intended to be exhaustive or to limit the invention in
the precise form disclosed, and obviously many modifications and
variations are possible in light of the above teaching. It is
noted that the terms ~upper~ and nlower" are terms of convenience
used to describe the elements of the engine inlet 10. For
example, it is clear that the engine inlet 10 can be oriented,
with respect to the rest of the hypersonic flight vehicle 14, at
any pre-chosen angle about the vehicle's longitudinal axis. In a
preferred embodiment of the hypersonic flight vehicle 14, the
term~ ~upper~ and ~lower~ describe the elements of the engine
inlet 10 when the hypersonic flight vehicle 14 is in level
flight. It is intended that the scope of the invention be
defined by the claims appended hereto.
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