Multi-missile canister gas management system

An exhaust gas management system for missile launch arrangements which incorporates multiple launch cells exhausting into a common plenum. The system provides a flow passage configuration with a transition section that permits rocket exhaust flow gas to expand to fill the channel area downstream of the nozzle exit. Automatic aft closure members are included which serve to close off the flow passages to inactive cells while providing an open passage for exhaust gases from an active cell undergoing a missile firing. This arrangement prevents back flow or recirculation of exhaust gases into the volume in the cell which is upstream of the rocket nozzle exit.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to the field of controlled flow, exhaust 
manifold systems and, more particularly, to apparatus for controlling the 
flow of exhaust gases from a single missile being fired in a multi-missile 
canister and directed into a common exhaust gas manifold or plenum tube 
connected thereto. 
2. Description of the Related Art 
In certain military applications, particularly on warships having missile 
firing capability, the missiles are stored in a series of vertically 
oriented chambers closely adjacent one another. Exhaust gas outlets are 
normally provided to duct rocket exhaust gases generated during intended 
or accidental rocket ignitions to a safe location. In such installations, 
manifolding of a number of chambers into a common exhaust duct or plenum 
tube has become conventional. 
There have been a number of approaches to the problems attendant upon the 
use of a common exhaust duct with a plurality of missile storage chambers. 
It is important to be able to block the exhaust gases from a missile which 
is being fired from blowing out through the individual chambers of other 
missiles. This is commonly accomplished by the use of doors or hinged 
panels which can open into the plenum chamber from the force of an 
impinging missile exhaust for the chamber containing the missile being 
fired and which can close off the passage at the base of a missile chamber 
opening into the exhaust plenum for other missiles. 
Eastman U.S. Pat. No. 2,445,423 discloses apparatus having a plurality of 
individual missile chambers coupled to a common plenum chamber with a 
plurality of hinged, spring-loaded doors at the juncture of each 
individual missile chamber with the plenum tube. These doors open for a 
rocket that is being fired and serve to confine the exhaust gases within 
the plenum chamber and away from other missile-storage chambers. 
There is also the problem of a portion of the rocket exhaust backing up 
into the chamber of the missile being fired and possibly over-pressurizing 
that missile chamber. 
My own prior U.S. Pat. No. 4,044,648, the entire disclosure of which is 
incorporated by reference as though fully set forth herein, discloses a 
pair of hinged doors at the base of each missile storage chamber in the 
passage connecting the chamber to an associated exhaust plenum duct. The 
pressure forces on opposite sides of the doors during the firing of a 
missile are balanced to control the degree to which the doors are opened 
in order to adjust the opening to the varying dimension of the rocket 
exhaust stream as the missile rises and leaves the chamber upon firing. As 
a consequence, the rocket exhaust stream functions as a suitable "gas 
plug" in the opening in order to prevent recirculation of the exhaust 
gases back into the chamber undergoing firing. 
It is important to control the rocket exhaust gas stream so that the gas 
plug is effective to prevent recirculation of exhaust gases back into the 
chamber. Control of the rocket exhaust stream on a dynamic basis to 
develop the gas plug effect appears to be more effective for the intended 
purpose than the use of fixed structure such as baffles, valves, diverters 
or the like which oftentimes have the undesirable result of interfering 
with the direct exhaust gas stream in their attempt to control flow, limit 
reverse circulation, etc. My prior U.S. Pat. No. 4,683,798, the entire 
disclosure of which is incorporated by reference as though fully set forth 
herein, discloses hinged doors near the lower end of each missile storage 
chamber but spaced from the juncture with the common plenum chamber by a 
transition region which provides a smooth transition from a generally 
square cross-section chamber in which a missile is stored and launched to 
a round exit opening in the chamber which connects with the exhaust 
plenum. This enhances the gas plug effect and uses it to prevent 
recirculation of exhaust gases back into the chamber of the missile being 
fired. 
My prior U.S. Pat. No. 4,686,884, the entire disclosure of which is 
incorporated by reference as though fully set forth herein, discloses an 
arrangement including sets of doors to close off missile storage chambers 
coupled to a common plenum chamber upon the firing of a missile in another 
chamber with the addition of pivotable deflector panels which are 
installed in transition sections between the missile storage and launch 
chambers proper and the common plenum chamber. 
The gas management system of the present invention incorporates some of the 
principles which are applicable to the systems of my prior patents cited 
hereinabove. However, the present system is intended for missile launch 
systems with multiple launch cells exhausting into a common plenum but 
with the cells arranged in clusters--e.g., by pairs--sharing common 
exhaust transition regions before reaching the juncture with the common 
plenum. 
SUMMARY OF THE INVENTION 
In brief, arrangements in accordance with the present invention comprise 
missile launch systems incorporating a plurality of launch cells 
exhausting into a common plenum. The construction of the system is such 
that the minimum flow area for exhaust gases resides in the canister or 
cell from which the fired missile is being launched. This flow area is 
such that, during the missile traversal of the launch canister, the 
supersonic rocket exhaust flow cannot negotiate the minimum flow area 
without "choking". "Choking" occurs when the product of the flow density 
and velocity is less than the mass flow rate per unit flow area, as 
described by the Continuity Equation. At the onset of "choke" conditions, 
the velocity at the minimum flow area has a Mach number which is just 
equal to 1.0. For some distance upstream, the flow is subsonic with the 
recovery pressure more than twice the pressure downstream of the minimum 
flow area. 
Arrangements in accordance with the present invention involve rocket 
exhaust flow that expands to fill the designed channel area downstream of 
the rocket nozzle exit, even when opposed by the pressure which exists at 
or beyond the channel exit. Such systems thus prevent any back flow or 
recirculation of exhaust flow into the volume which is upstream of the 
rocket nozzle exit. The area downstream of the rocket nozzle is equal to 
or greater than the nozzle exit and is constant or increasing in size as a 
function of distance downstream from the nozzle. The disclosed embodiments 
are specifically designed to protect multi-missile canisters and the 
missiles therein during any normal or restrained missile firing in a 
Vertical Launcher System (VLS). 
In accordance with an aspect of the invention, embodiments thereof utilize 
a single closure door near the aft end of each cylindrical launch cell in 
the multi-missile canister and further includes a transition section 
mating with the VLS plenum. This door opens under the influence of gas 
flow exhausting from an active rocket nozzle. The flow area through the 
door is not the restricting area in the system, but rather this is the 
minimum flow area as described hereinabove. The door is arranged to close 
under pressure from any opposing gas flow which is directed toward the 
rocket nozzle when the rocket is inactive. Upon reclosure, the door may 
latch and lock in place to isolate that cell from the remaining launch 
environment. 
BRIEF DESCRIPTION OF THE DRAWINGS 
A better understanding of the present invention may be realized from a 
consideration of the following detailed description, taken in conjunction 
with the accompanying drawing in which: 
FIG. 1 is a perspective view of a multi-missile canister system 
incorporating my invention; 
FIG. 2 is a plan view of the arrangement of FIG. 1; 
FIG. 3 is a sectional elevation of a multi-missile canister system in 
accordance with my invention, taken along the line 3--3 of FIG. 2 and 
looking in the direction of the arrows; 
FIG. 4 is a view of a portion of FIG. 3 lying along the line 4--4 of FIG. 3 
and looking in the direction of the arrows; 
FIG. 5 is a sectional view taken along the line 5--5 near the bottom of 
FIG. 3 and looking upward in the direction of the arrows; 
FIG. 6 is a cutaway elevation showing the construction of a prior art 
apparatus; 
FIG. 7 is a graph depicting a plot of door opening time for different 
degrees of initial door closure; 
FIG. 8 is a sectional elevation view of a particular door suspension 
arrangement for use in the embodiments of my invention; 
FIG. 9 is a view showing details of the door suspension of FIG. 8 as viewed 
from the underside along the line 9--9 looking upward in the direction of 
the arrows; 
FIG. 10 is a schematic plan view of a four-missile canister system in 
accordance with the present invention; and 
FIG. 11 is a side sectional view of the arrangement of FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
First Embodiment - Dual Missile Canister System 
One embodiment of my invention comprising a dual missile canister gas 
management system is depicted in FIGS. 1-5. This embodiment 10 principally 
comprises a lower transition section 12, an upper transition section 14 
and a pair of missile canisters or cells 16 which sit atop the section 14. 
The section 12 is generally square (or rectangular) in cross section with 
adjacent sidewalls 20 joined at right angles and provided with a bottom 
flange 22 which serves to couple the system to an associated plenum 
chamber 24. This section 12 is not an essential part of my invention but 
is included where it is part of an existing installation to which 
arrangements in accordance with my invention are to be added. 
The lower transition section 12 terminates in an upper flange 26 which is 
joined to a plate 28 to which the upper transition portion is attached. 
Vertically angled sidewalls 30 extend upwardly from the plate 28 to a 
second plate 32, to which the missile canisters 16 are attached. Adjacent 
sidewalls 30 are joined together, forming a six-sided configuration of the 
upper transition section 14. The upper plate 32 is provided with a pair of 
circular openings 34 to connect the interior volumes of the two missile 
canisters 16 with the upper transition portion 14. The plate 28 is 
provided with an opening 38 shaped to match the lower cross-sectional 
outline of the transition section 14 which serves to connect the interior 
spaces of the two transition portions 12 and 14. A tapered skirt 40 
projects downwardly into the upper portion of the lower transition section 
12, substantially continuing the angle with the vertical which is made by 
the walls 30 of the upper transition section 14. 
The upper transition portion 14 is divided into two compartments 50A and 
50B by a transverse vertical plate 52 which extends across the interior of 
the transition section 14 between opposed sidewalls 30 in a plane which is 
orthogonal to a plane defined by the two longitudinal axes of the missile 
canister 16 (the plane of the paper in FIG. 3). This transverse vertical 
plate 52 extends from near the top of the upper transition section 14 into 
the space encompassed by the skirt 40. 
In each of the spaces 50A, 50B there is a hinged door, 56A or 56B. These 
two doors 56A, 56B are hinged to swing about a pivot point 58 by hinge 
mechanism 60. The doors 56A, 56B are shown in solid outline form in FIG. 3 
in the closed position, wherein the terminal edge of a door, 62A or 62B, 
abuts against the lower edge of adjacent walls 30 of the upper transition 
section 14. This is best shown in FIG. 4, wherein the outline of the door 
56A is depicted as shaped to match the hexagonal cross section of the 
upper transition section 14 at the angle of juncture. The doors 56A and 
56B are shown in broken outline form in FIG. 3 as they transition from the 
fully closed position to the fully open position in which they rest flat 
against the vertical plate 52. It will be noted that the plate 52 extends 
to the lower edge of the doors 50A, 50B when the doors are in the fully 
open position. When in the closed position, the doors 50A, 50B completely 
block off the transfer of any exhaust gases upward into the missile 
cylinders 16 from the exhaust plenum. In the operation of the system 10, 
these doors open one at a time to permit exhaust gases from a missile 
being fired in one of the missile cylinders 16 to flow downwardly into the 
exhaust plenum 24 through the transition sections 12, 14 while limiting or 
preventing any reverse flow or recirculation back into the cell 16. 
FIG. 6 shows one example of a prior art missile launcher system which 
includes a missile storage and launch canister 66, a transition section 67 
and a plenum 68 with an exhaust duct (not shown). The canister 66 is sized 
to contain one missile with its attendant wings and fins. The rocket motor 
diameter and missile body are small, relative to the canister area. A 
hinged door 69 is provided to block reverse flow of gases from the plenum 
68 into the canister 66. The arrangement in accordance with my invention 
depicted in FIGS. 1-5 makes it possible to double the number of missile 
canister which may be accommodated within the deck area formerly assigned 
to a single missile canister while achieving the desirable effects of the 
gas management system of the invention. 
The preferred position for the closed doors of embodiments of my invention 
is at angle of about 45 degrees to the missile centerline, as is indicated 
in FIG. 3. One advantage of this is the reduced response time following a 
rocket ignition and the reduction in kinetic energy of the opening door 
when it hits the back plate 52, compared with a door that closes at 90 
degrees to the missile centerline. FIG. 7 is a graph of door opening time 
from full closure. The solid line 70 shows the time for opening a door 
which is closed at a 45 degree angle, whereas the broken line 72 is a plot 
of the opening time for a door which is closed at a 90 degree angle to the 
missile centerline (0 degrees reference angle) as in the prior art 
arrangement of FIG. 6. As is apparent from FIG. 7, the time to fully open 
the door is reduced by about 30% for a door which is closed at a 45 degree 
angle, compared with a door which is positioned perpendicular the missile 
centerline. The longer it takes the door to open, the greater the ignition 
pressure pulse in the active canister. Also, the impact velocity on the 
divider wall 52 (FIGS. 3 and 5) is reduced by approximately 30% for the 45 
degree angled door configuration. 
The operation of the rigid doors in a multi-missile canister is automatic 
and is powered by the rocket exhaust flows and related gas pressures in 
the vertical launch system. The active cell door is opened under the 
pressure of the active cell rocket exhaust and tends to close under the 
influence of any adjacent rocket exhaust flowing toward it. FIG. 8 shows 
such a configuration with a door which is counterbalanced by a 
counterbalancing weight, indicated in phantom by the reference numeral 53, 
so that it is biased toward closing from the fully opened position. A 
spring biasing arrangement in the hinge 60 could be provided as well. 
Alternatively, or in addition, the door may be configured to allow upward 
flowing gases to stagnate behind the fully opened door, as is indicated in 
the example of FIG. 9 which is a view from the underside of the door 
structure of FIG. 8. FIG. 9 shows a cavity 57 in the back side of the door 
56 which provides a stagnation volume between the door 56 and the wall 52. 
As another option, the lip of the door 56 may be angled as shown at 59 in 
FIG. 8. With an angled lip 59, upwardly flowing gases will tend to force 
the door toward the closed position. 
It will be understood that the rigid doors 56 are ablatively protected on 
both the top (missile side) and bottom (plenum side) surfaces with the top 
surface being provided with greater ablative protection in order to be 
able to withstand restrained firing exhaust impingement. The hinge 
mechanism 60 is shadowed from any direct exhaust impingement, but is 
ablatively coated as needed to provide protection from upwardly flowing 
exhaust gases from adjacent cell firings. Since certain ablative materials 
are non-charring, ablatively effective, flexible and reject aluminum oxide 
deposition under rocket exhaust impingement, an effective seal of the 
active cylinder aft end can be maintained prior to and after active cell 
rocket motor firing. A material bearing the designation REFSET L3203-6 is 
an example of a suitable ablative for this purpose. 
A re-latch capability may be provided so that one of the doors in the 
multi-missile canister will re-latch upon firing in the next adjacent 
cell. Such re-latching is possible as a result of the pressure pulse which 
is imposed on a multi-missile vertical launch system at rocket motor 
ignition. This door re-latching capability is a one-time function. The 
re-latching mechanism would be activated as the doors opened by the active 
cell rocket exhaust and would latch and lock upon door closure which 
results from the firing pressure pulse in an adjacent cell. Once latched, 
the cell would be isolated from the vertical launch system environment for 
all additional firings. 
Second Embodiment - 4-Pack Missile Canister System 
A second embodiment 100 of my invention is represented schematically in 
FIGS. 10 and 11. This embodiment comprises a group of four missile 
canisters assembled and arranged for firing, one at a time, with the 
rocket motor exhaust being directed to the plenum through a common 
transition section. Thus, four missile cells or canisters 102 are shown in 
the plan view of FIG. 10. These cells 102 are coupled together via a 
transition section 104 to the common exhaust plenum 106 (FIG. 11). A 
transverse dividing wall 108 divides the transition section into two 
regions, and each of these is further bifurcated by a wall 110 extending 
orthogonally to the wall 108. In each of the regions formed by the 
dividing wall 108, there is a pair of doors, such as the door 112, which 
are pivotably supported by a central hinge mechanism 114. The action of 
the doors 112 is essentially the same as is described for the operation of 
the doors 56 in the embodiment of FIGS. 1-5. A single door 112 is opened 
during the firing of a rocket motor in the cell 102 with which the door 
112 is associated. An open or partially opened door 112 is restored to the 
closed position upon the development of positive pressure in the plenum 
106 for all missile canisters 102 which are not undergoing firing. 
Thus, as shown and described hereinabove, particular arrangements in 
accordance with the present invention provide for an increase in the 
number of missile canisters in a vertical launch system which can be 
coupled to a single port of an exhaust gas plenum in a shipboard 
installation or the like. The disclosed embodiments include aft closures 
for the individual canisters of a multi-cell system which move to the open 
position under the influence of exhaust gases in the cell undergoing 
ignition while at the same time acting to close off other cells in the 
system and thereby prevent the upward flow of exhaust gases into those 
other cells. Operation of the end closures is automatic under the 
influence of the gas pressures on opposite sides of an individual door. 
Thus, improved control of exhaust gas flow and limitation of reverse 
circulation into a cell undergoing firing provide protection to the 
missiles and prevent the application of excessive gas pressures in the 
cells. 
Although there have been described hereinabove various specific 
arrangements of a multi-missile canister gas management system in 
accordance with the invention for the purpose of illustrating the manner 
in which the invention may be used to advantage, it will be appreciated 
that the invention is not limited thereto. Accordingly, any and all 
modifications, variations or equivalent arrangements which may occur to 
those skilled in the art should be considered to be within the scope of 
the invention as defined in the annexed claims.