Patent Description:
Booster rockets are sometimes used to add thrust to flight vehicles, such as missiles. Certain limitations are sometimes present regarding the characteristics for add-on booster rockets.

<CIT> discloses compact lightweight ramjet engines incorporating swirl augmented combustion with improved performance.

<CIT> discloses missile configurations controls and utilization techniques.

A booster rocket has an annular shape, allowing it to be placed around an object.

A booster rocket is mechanically coupled to a nozzle of a main propulsion system, such as a jet, without interfering with operation of the jet.

A booster rocket is couplable to a part of existing flight vehicle, adding thrust without expanding the envelope of the flight vehicle.

A booster rocket is mechanically coupled to a part of main propulsion system, and remains so coupled even after the propellant (fuel) of the booster rocket is expended.

According to an aspect of the invention, a booster rocket includes: an annular casing defining an annular space therewithin, and having a central opening; and a solid rocket fuel in the annular space, wherein the annular casing defines an annular gap that acts as a nozzle for the booster rocket, the casing includes protruding tabs that maintain the annular gap, and the casing includes an inner part and an outer part, with the outer part including a cylindrical forward section, and an inwardly-sloped aft section and the protruding tabs are at an aft edge of the outer casing part.

According to an embodiment of any paragraph(s) of this summary, the casing is made of metal.

According to an embodiment of any paragraph(s) of this summary, the casing is made of sheet metal.

According to an embodiment of any paragraph(s) of this summary, the casing is a single unitary part.

According to an embodiment of any paragraph(s) of this summary, the casing is multiple casing parts.

According to an embodiment of any paragraph(s) of this summary, the multiple casing parts include an inner casing part and an outer casing part.

According to an embodiment of any paragraph(s) of this summary, the inner casing part and the outer casing part are threadedly coupled together.

According to an embodiment of any paragraph(s) of this summary, the protruding tabs are circumferentially spaced around the annular gap.

According to an embodiment of any paragraph(s) of this summary, the protruding tabs are on an inner part of the casing.

According to an embodiment of any paragraph(s) of this summary, the protruding tabs are on an outer part of the casing.

According to an embodiment of any paragraph(s) of this summary, an inner part of the casing includes a cylindrical forward section, and an inwardly sloped aft section.

According to an embodiment of any paragraph(s) of this summary, the inwardly sloped aft section of the inner part is substantially parallel to the inwardly sloped aft section of the outer part.

According to an embodiment of any paragraph(s) of this summary, the inwardly sloped aft section of the outer part includes a wedge portion that decreases in thickness to an aft edge of the outer part.

According to an embodiment of any paragraph(s) of this summary, an outer part of the casing extends further aft than an inner part of the casing.

According to an embodiment of any paragraph(s) of this summary, an inner part of the casing extends further aft than an outer part of the casing.

According to an embodiment of any paragraph(s) of this summary, the casing includes a liner along at least part of an inside surface of the casing, with the liner at least in part defining the annular space.

According to an embodiment of any paragraph(s) of this summary, the fuel is configured within the annular space for end burning.

According to an embodiment of any paragraph(s) of this summary, the fuel is configured within the annular space for core burning.

According to an embodiment of any paragraph(s) of this summary, the fuel is configured within the annular space for both end burning and core burning.

According to an embodiment of any paragraph(s) of this summary, the fuel has one or more channels therein.

According to an embodiment of any paragraph(s) of this summary, the one or more channels include at least one channel in a longitudinal direction.

According to an embodiment of any paragraph(s) of this summary, the fuel is along an outer wall of the casing, with a space between the fuel and an inner wall of the casing.

According to an embodiment of any paragraph(s) of this summary, the booster rocket further includes an igniter in the casing.

According to an embodiment of any paragraph(s) of this summary, the booster rocket is in combination with an object to which the rocket booster is mechanically coupled.

According to an embodiment of any paragraph(s) of this summary, the object is a part of a flight vehicle.

According to an embodiment of any paragraph(s) of this summary, the object is an aft part of a flight vehicle.

According to an embodiment of any paragraph(s) of this summary, the object is part of a propulsion device at an aft end of the flight vehicle.

According to an embodiment of any paragraph(s) of this summary, the object is centered on a longitudinal centerline of the flight vehicle.

According to an embodiment of any paragraph(s) of this summary, the rocket booster is centered around a longitudinal centerline of the flight vehicle.

According to an embodiment of any paragraph(s) of this summary, the object is a turbojet engine.

According to an embodiment of any paragraph(s) of this summary, the object protrudes from an aft end of a fuselage of the flight vehicle.

According to an embodiment of any paragraph(s) of this summary, the flight vehicle is a missile.

According to another aspect of the invention, a missile includes: a fuselage; a main propulsion system that includes a nozzle protruding aftward from the fuselage; and a booster rocket around the nozzle. The booster rocket includes: an annular casing defining an annular space therewithin, and having a central opening through which the nozzle protrudes; and a solid rocket fuel in the annular space.

According to yet another aspect of the invention, a method for increasing thrust of a flight vehicle includes the steps of: placing an annular booster rocket according to an aspect disclosed herein around a part of a main propulsion system of the flight vehicle; and burning fuel of the booster rocket to product thrust, wherein the annular casing defines an annular gap that acts as a nozzle for the booster rocket, the casing includes protruding tabs that maintain the annular gap, and the casing includes an inner part and an outer part, with the outer part including a cylindrical forward section, and an inwardly-sloped aft section and the protruding tabs are at an aft edge of the outer casing part.

To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.

A rocket booster has an annular shape, with a casing defining an annular space therewithin, and a solid rocket fuel in the annular spacing. The casing itself at least in part defines an annular gap that functions as a nozzle for the rocket booster, with protruding tabs on the casing aiding in maintaining a uniform height of the annular gap. The rocket booster may be mechanically coupled to an object protruding from the back of a fuselage of a flight vehicle, such as a missile. For example, the rocket booster may be placed around an aft turbojet nozzle of the flight vehicle. This allows the rocket booster to be used in situations where primary propulsion must be running both before and after (and perhaps during) the firing of the rocket booster. The rocket booster also advantageously may provide thrust along the centerline of the flight vehicle, and may be used in situations where there is a requirement to maintain the booster as part of the flight vehicle throughout flight. The rocket booster may have a truncated aerospike nozzle configuration, and may provide for a low-drag additional propulsion system that does not interfere with the operation of the primary propulsion system. Further, the casing of the rocket booster may double as a rear jet engine mount.

With reference initially to <FIG>, a flight vehicle <NUM>, such as a missile, includes a fuselage <NUM>, with a main propulsion device <NUM> protruding from or as part of an aft end <NUM> of the fuselage <NUM>. The main propulsion device <NUM> may be a turbojet engine. The protruding part of the main propulsion device <NUM> may be a nozzle <NUM> of the turbojet engine.

As shown in <FIG>, a booster rocket <NUM> may be mounted on and around the nozzle <NUM>, with the nozzle <NUM> protruding through a central opening <NUM> in the booster rocket <NUM>. The booster rocket <NUM> may thereby provide additional thrust to the flight vehicle <NUM>, without interfering with the operability of the main propulsion device <NUM>. The booster rocket <NUM> may provide the additional thrust without affecting the general envelope of the flight vehicle <NUM>.

The missile (flight vehicle) <NUM> may have additional features, for example fins <NUM> or other wings or control surfaces. Other types of additional features include a guidance system, a communications system, various types of sensors or information-gathering features, and a payload such as a warhead or other destructive material.

The booster rocket <NUM> is shown mounted around the nozzle <NUM>, but it will be appreciated that the nozzle <NUM> is but one example of a broader category of objects to which the booster rocket <NUM> is mounted. The object may alternatively be other sorts of structures, whether provide a propulsive function or not, that pass into or through the central opening <NUM> of the booster rocket <NUM>. Advantageously, both the object (the nozzle <NUM> in the illustrated embodiment) and the booster rocket <NUM> are centered around a longitudinal centerline (central axis) <NUM> of the flight vehicle <NUM>.

The flight vehicle <NUM> is just one example of the many types of flight vehicles that may receive the booster rocket <NUM>, in order to produce additional thrust. Alternatives to the missile are other types of vehicles with main propulsion devices of any of a variety of suitable types.

<FIG> shows further details of one embodiment of the booster rocket <NUM>. The rocket <NUM> includes an annular casing <NUM> that defines an annular space <NUM> where a solid rocket fuel (propellant) <NUM> is located. The casing <NUM> may be made up of multiple parts, such as an inner casing part <NUM> and an outer casing part <NUM>, linked together by an aft end casing part <NUM>. In the illustrated embodiment the parts <NUM>-<NUM> are all parts of a single unitary part that is made of metal, such as being made out of a single piece of sheet metal, for example steel. However in other embodiments the casing <NUM> may be made of multiple parts.

The outer casing part <NUM> includes a cylindrical forward section <NUM>, and an inwardly-sloped aft section <NUM> that is bent inward toward the turbojet nozzle <NUM>. In some embodiments the slope of the aft section <NUM> may correspond to a slope of the turbojet nozzle <NUM>.

Many configurations are possible for the fuel (propellant) <NUM>. In the illustrated embodiment, the fuel <NUM> is along the outer part <NUM> of the casing <NUM>, with a space between the fuel <NUM> and the inner part <NUM> of the casing <NUM>. The fuel <NUM> may be configured for core burning, for end burning, or for a combination of end burning and core burning. As described further below, the fuel <NUM> may optionally have one or more channels therein, of any of various suitable configurations, to control the burn rate. Such channels, when present, may include at least one channel in a longitudinal (axial) direction, parallel to an axis of the flight vehicle <NUM> (the centerline <NUM>), which may be coincident with axes of both the booster rocket <NUM> and the object (such as the turbojet nozzle <NUM>) to and around which the booster rocket <NUM> is mounted.

The fuel <NUM> is located between the inner part <NUM> and the outer part <NUM>. Combustion of the fuel <NUM> occurs in the annular space <NUM>, which acts as a combustion chamber for the booster rocket <NUM>. Pressurized gases from the combustion of the fuel <NUM> exit the booster rocket <NUM> at an aft end, through an annular rocket nozzle <NUM> defined at least in part by the casing <NUM>. In the illustrated embodiment the annular nozzle <NUM> is an annular gap between the outer casing part <NUM> and an outer surface of the turbojet nozzle <NUM> that serves as the object around which the rocket booster <NUM> is installed.

With reference now in addition to <FIG>, the casing <NUM> has features that help maintain a desired configuration of the gap that serves as the rocket nozzle <NUM>. At an aft edge <NUM> of the outer casing part <NUM> (the edge of the aft section <NUM> of the outer casing part <NUM>) there are a series of protruding tabs <NUM>. The protruding tabs <NUM> protrude inward to maintain a desired spacing between the edge <NUM> and the turbojet nozzle <NUM>. The protruding tabs <NUM> may be evenly circumferentially spaced around the edge <NUM>. The tabs <NUM> may be deformed or otherwise produced from the material of the outer casing part <NUM>, or may be material added on to an inner surface (inner wall) of the outer casing part <NUM>.

<FIG> illustrate a method for making the rocket booster <NUM>, and in particular for forming the annular casing <NUM>, showing a cross-section of material used to produce the casing <NUM> (<FIG>). <FIG> shows flat stock <NUM>, which may be cut to a suitable size and shape by a suitable process, such as by stamping, laser cutting, or water jet cutting. <FIG> shows the shape of the stock <NUM> after a first strike, with inner and outer segments of material to form the inner and outer parts of the casing.

<FIG> shows a third step, to produce the section of the outer casing part that folds inward. The parts of the casing <NUM> are labeled in <FIG> as described above, with the casing parts <NUM>, <NUM>, and <NUM>, and with the forward section <NUM> and the aft section <NUM> of the outer casing part <NUM>.

Finally, <FIG> shows the situation with the fuel or propellant <NUM> introduced into the annular space <NUM> that is within and defined by the casing <NUM>. The casing <NUM> is thus formed by simple manufacturing steps from a single piece of material.

Many variations are possible in the configuration of a booster rocket that is capable of being installed around an object. Some alternative configurations are described below, and different sorts of manufacturing techniques may be used to produce the booster rocket <NUM>, and alternative booster rocket configurations.

The booster rocket <NUM> may have additional features not shown in the figures, for example having an igniter placed in an opening in the casing <NUM> at a suitable location for igniting the fuel (propellant) <NUM>. Such additional features may be shown in one or more of the other embodiments shown below.

The booster rocket <NUM> advantageously uses the turbojet nozzle <NUM> for some of its inner boundary. That is, an outer surface of the turbojet nozzle <NUM> provides part of the boundary of the annular space <NUM> (<FIG>).

The booster rocket <NUM> provides a low profile, without impacting the envelope of the flight vehicle <NUM> (<FIG>). The low profile means that the rocket booster <NUM> does not significantly impact the drag of the flight vehicle <NUM>. The rocket <NUM> is retained without the flight vehicle <NUM> after use, and does not prevent use of the main propulsion device <NUM> (<FIG>), before, after, or during firing of the booster rocket <NUM>. The rocket <NUM> may be configured to operate with a truncated aerospace nozzle configuration, which is compact and altitude compensating.

<FIG> show an alternative configuration, a booster rocket <NUM> that has a casing <NUM> that has two parts <NUM> and <NUM> that are threadedly joined together. The parts <NUM> and <NUM> are formed separately and screwed together along threads <NUM>, after an annular solid fuel (propellant) <NUM> is put into place. Once the parts <NUM> and <NUM> are joined together the fuel <NUM> is in an annular space <NUM> defined by the parts <NUM> and <NUM>. The fuel <NUM> can be ignited by an igniter <NUM> that is secured in a hole in the outer casing part <NUM>. Pressurized gasses from combustion of the fuel <NUM> pass through an annular nozzle <NUM> that is defined between the casing parts <NUM> and <NUM>. The gap height of the annular nozzle <NUM> may be maintaining by tabs <NUM> on the inner casing part <NUM>, as described further below.

The inner casing part <NUM> has a cylindrical forward section <NUM> and an inwardly-angled aft section <NUM>. The inner casing part sections <NUM> and <NUM> may correspond in exterior shape to an object to which the rocket booster <NUM> is coupled, for example to the shape of a turbojet nozzle. Further, the inwardly-angled aft section <NUM> may constitute a truncated aerospike shape, which may provide for efficiency in the operation of the booster rocket <NUM>. The inner casing part <NUM> includes a forward end <NUM> which constitutes the forward end of the rocket booster <NUM>. The forward end <NUM> may have mechanical connections <NUM> and <NUM> thereupon, which may be configured to connect the booster rocket <NUM> to a flight vehicle. The mechanical connections <NUM> and <NUM> may be any of a variety of suitable clips, clamps, or other suitable mechanisms for making a connection.

The inner casing part <NUM> also includes an externally threaded outer portion <NUM> that is used to make the threaded connection with an internally threaded cylindrical aft section <NUM> of the outer casing part <NUM>. The outer casing part <NUM> has an inwardly-sloped aft section <NUM> that has a wedge portion <NUM> of varying thickness, that tapers to an edge <NUM> that forms a boundary of the annular nozzle <NUM>. The inward slope angle of the outer casing aft section <NUM> may be the same as, substantially similar to, or similar to, the inward slope of the inner casing part aft section <NUM>. Thus the aft sections <NUM> and <NUM> may be parallel to one another.

As best seen in <FIG>, the tabs <NUM> are a series of protrusions circumferentially spaced around an aft end of the inner casing cylindrical section <NUM>, where the sections <NUM> and <NUM> meet. These tabs <NUM> mechanically engage the edge <NUM> of the outer casing portion <NUM>, as best seen in <FIG>, to maintain an even height for the annular gap of the nozzle <NUM>.

The casing parts <NUM> and <NUM> may have a liner <NUM> on their surfaces that define the annular space <NUM> that acts as the combustion chamber. The liner <NUM> may be a heat-resistant material that provides some protection to the casing parts <NUM> and <NUM>. The liner <NUM> may be made of any of a variety of suitable materials, non-limiting examples being aluminum and cardboard.

<FIG> shows a cross-sectional shape of an annular fuel <NUM> that includes a series of longitudinal channels <NUM> to regulate the burn speed and thus the thrust production. Such channels may have any of a variety of suitable configurations (depths and/or shapes, for example), and there may be various numbers of channels, with any of various suitable spacings, to produce a desire thrust profile over time. It should be appreciated that the configuration shown in <FIG> is for illustration purposes, and the channels <NUM> shown are necessarily to scale.

Claim 1:
A booster rocket (<NUM>, <NUM>) comprising:
an annular casing (<NUM>) defining an annular space (<NUM>, <NUM>) therewithin, and having a central opening (<NUM>); and
a solid rocket fuel (<NUM>) in the annular space (<NUM>, <NUM>), wherein the annular casing (<NUM>) defines an annular gap that acts as a nozzle for the booster rocket (<NUM>, <NUM>), the casing (<NUM>) includes protruding tabs (<NUM>) that maintain the annular gap, and the casing includes an inner part (<NUM>) and an outer part (<NUM>), with the outer part (<NUM>) including a cylindrical forward section (<NUM>), and an inwardly-sloped aft section (<NUM>), the booster rocket being characterised in that the protruding tabs (<NUM>) are at an aft edge (<NUM>) of the outer casing part.