U.S. patent application number 09/782198 was filed with the patent office on 2003-10-23 for projectile diverter.
Invention is credited to Fahey, Wm. David, Folsom, Mark, McGowan, Jared M., Piper, Charles III.
Application Number | 20030197088 09/782198 |
Document ID | / |
Family ID | 29216082 |
Filed Date | 2003-10-23 |
United States Patent
Application |
20030197088 |
Kind Code |
A1 |
Folsom, Mark ; et
al. |
October 23, 2003 |
Projectile diverter
Abstract
The present invention provides a fast, low-cost, small diverter
capable of generating a relatively high impulse (1-5 N-sec) over a
short time period. The diverter is adapted for installation in a
projectile for steering the projectile in flight by ejecting an end
cap in response to control signals from a guidance system. In one
embodiment, multiple diverters are arranged in one or more bands
about a flying projectile such as a rocket. Each diverter includes
a header assembly providing a mounting surface and support for a
plurality of electrical leads, a reactive semiconductor bridge
mounted on the mounting surface of the header assembly and
providing an electrical path for the electrical leads at a certain
voltage across the bridge, a diverter body supporting the header
assembly and containing a prime, wherein the reactive semiconductor
bridge and the prime define a gap, and an end cap attached to the
diverter body and containing a propellant.
Inventors: |
Folsom, Mark; (Carmel,
CA) ; Piper, Charles III; (Los Banos, CA) ;
Fahey, Wm. David; (Copertino, CA) ; McGowan, Jared
M.; (Boulder Creek, CA) |
Correspondence
Address: |
Robert Moll
@ PatentPlant
1173 St. Charles Court
Los Altos
CA
94024
US
|
Family ID: |
29216082 |
Appl. No.: |
09/782198 |
Filed: |
February 8, 2001 |
Current U.S.
Class: |
244/3.22 |
Current CPC
Class: |
F42B 3/13 20130101; F41G
7/305 20130101; F42B 10/661 20130101 |
Class at
Publication: |
244/3.22 |
International
Class: |
F42B 015/01; F41G
007/00 |
Claims
What is claimed:
1. A diverter adapted for installation in a flying projectile,
comprising: a header assembly providing a mounting surface and
support for a plurality of electrical leads; a reactive
semiconductor bridge mounted on the mounting surface of the header
assembly and providing an electrical path for the electrical leads
at a certain voltage across the bridge; a diverter body supporting
the header assembly and containing a prime, wherein the reactive
semiconductor bridge and the prime define a gap; and an end cap
attached to the diverter body and containing a propellant, wherein
the rapid burning of the propellant produces gases, which eject the
end cap from the diverter body to produce a force to divert the
flying projectile.
Description
[0001] The present invention relates to controlling the flight path
of rockets, missiles, and other flying projectiles. In particular,
the invention relates to a small fast diverter for use with a
projectile for steering the projectile in flight by ejecting an end
cap of the diverter in response to a signal from a guidance
system.
BACKGROUND OF THE INVENTION
[0002] In general, a diverter generates lateral reaction force to
steer a rocket, missile, and other projectile in flight. The amount
of impulse generated by the diverter will determine how much the
flight path is diverted. Impulse is the product of the average
reaction force over the time exerted. Recent applications for
diverters include steering 2.75-inch diameter rockets, artillery,
and gun projectiles, e.g., 30 mm projectiles. In such applications,
we need small diverters that can generate relative high impulse
(e.g., 1 to 5 N-sec) in short time periods. Because rockets,
missiles, and projectiles often spin at high rates, the impulses
must be made in a short time period, e.g., on the order of 1 ms.
If, for example, a projectile is spinning at 3600 RPM, it is
spinning at 60 revolutions per second or 21.6 degrees per
millisecond. If the diverter provides a reaction force for 10 ms,
this will provide force over 216 degrees. Providing the force over
this time period is not efficient. Instead, we would like to
provide the force for 1-ms or less. If the diverter can provide the
force over this shorter period, the guidance system can make
multiple steering corrections when needed as a projectile flies
through space by igniting the multiple diverters arranged around
it.
[0003] One might consider using small rocket motors for diverters
having small volume, but this has proven ineffective when a
relatively high impulse is required over a short time. It is too
difficult for a rocket motor with loose loaded propellant to burn
all of its propellant in a short time without ejecting a large
percentage of the propellant unburned. Further, the relatively low
packing density of propellant results in the rocket motor ejecting
a considerable volume of propellant. Additionally, the rocket
propellant container cannot be manufactured that small. Providing
the propellant in a higher density form, e.g., cast propellant
grain, might appear helpful, but a compact single grain is unlikely
to have a thin enough web to operate in the required time period
due to propellant burn rate limitations. Where low cost is
required, such as less than $5.00 per diverter, without large
capital investment, it is difficult to envision good results with
rocket motors. Small rocket motors can provide impulses of 1-5
N-sec, but for longer time periods on the order of 10 ms.
Additionally, rocket motors are not volume efficient for another
reason. To fully use the energy in a rocket propellant, a
converging/diverging nozzle with significant mass and volume is
needed to fully expand and accelerate the propellant gas.
[0004] Another approach might be to use conventional bridgewire
pyrotechnic devices for small diverters, but there are unsolved
problems. One problem is how to ignite them quickly and reliably.
Conventional semiconductor bridge technology provides very fast hot
ignition, but it is also only low energy ignition lasting for
microseconds. The energy output is dependent on energy input; when
only low input energy is available, only small output energy can be
produced, which may not be sufficient to provide reliable ignition.
Further, conventional pyrotechnic devices and semiconductor bridges
require tight coupling between the ignition element and the
pyrotechnic material. Up to now it has been critical for reliable
ignition with semiconductor bridges that the ordnance or
pyrotechnic material to be ignited be in close contact with the
semiconductor bridge during ignition. This means lower ignition
energy can be used, but it requires intimate contact between the
bridge and prime, adding to manufacturing costs. The applications
mentioned earlier can subject diverters to very high accelerations
and shocks, e.g., on the order of 100,000 g's. During such events
the prime may separate from the ignition element and reduce the
reliability of the diverter. Bridgewires require high firing
energies or very small and unsafe bridgewires for fast response.
Thus, attempts to produce small low cost diverters generating
relatively high impulse over brief periods of time have not been
successful.
SUMMARY OF THE INVENTION
[0005] The present invention provides a small, fast, low cost
diverter for steering a rocket, missile, or other projectile. The
diverter uses a reactive semiconductor bridge for the ignition
source and ejects an end cap from a diverter body to generate a
fast relatively high impulse. A header assembly extends into the
diverter body and supports the reactive semiconductor bridge and
provides electrical contact to a fireset. When desired, the
reactive semiconductor bridge provides fast ignition of the prime
and allows for a gap between the semiconductor bridge and the
prime. The ignited prime in turn ignites the propellant. The
burning propellant produces gases, which are confined in the
diverter until the pressure builds to the point when the end cap of
the diverter is ejected. Requiring the propellant to generate high
pressures to eject a solid mass such as an end cap is a much more
efficient method of retrieving the energy from the propellant than
ejecting hot gases from a rocket motor. The advantage of the
present invention is a relatively low cost, high impulse compact,
fast functioning diverter results compared to what can be provided
with a small rocket motor. The use of the reactive semiconductor
bridge allows very fast firings since ignition occurs in
microseconds. The reactive semiconductor bridge allows reliable
operation at low input energies since the reactive semiconductor
bridge provides a large energy output to ignite the prime. The
reactive semiconductor bridge can ignite prime across a gap and
this provides a safety margin in case the shock or acceleration of
projectile launch would cause the prime to become separated from
the bridge. Reliable diverters can be therefore built at relatively
low cost using this technology.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 illustrates a cross-sectional view of a rocket with a
single diverter installed on the right hand side.
[0007] FIG. 2 illustrates a perspective view of the rocket with
three bands of diverters. Each band includes eight diverters like
those shown in FIGS. 1 and 3B. The view includes a partial
cross-section through the first of the three bands of
diverters.
[0008] FIG. 3A is an end view of the diverter shown in FIG. 1.
[0009] FIG. 3B is a detailed cross-section of the diverter shown in
FIG. 1.
[0010] FIG. 4A is an electrical lead end view of the header
assembly shown in FIG. 4B.
[0011] FIG. 4B is a cross-section of the header assembly shown in
FIG. 3B.
[0012] FIG. 4C is a semiconductor bridge end view of the header
assembly shown in FIG. 4B.
[0013] FIG. 5A is a detailed cross-section of the semiconductor
bridge shown in FIG. 3B.
[0014] FIG. 5B is a view of the semiconductor bridge mounted on the
header assembly shown in FIGS. 3B and 4C.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] FIG. 1 shows a cross-sectional view of a rocket 10 with a
single diverter 12 on the right side. In this embodiment, the
rocket 10 is a 2.75-inch diameter rocket. It should be apparent
from the specification, however, that the diverter would be useful
on many types of projectiles. As shown in FIG. 1, the core of
rocket 10 has eight barrels 1, 2, 3, 4, 5, 6, 7, and 8 for
installing eight diverters, just like diverter 12, in a band about
the rocket 10. The rocket 10 includes a free passage 9 to allow
connection of each of the diverters 12 to the fireset (not
shown).
[0016] The diverters can be arranged in several bands about the
rocket 10 as shown in FIG. 2. FIG. 2 illustrates a perspective view
of the rocket 10 with three bands of diverters 12. Each band
includes eight diverters but other amounts are possible besides
those shown in FIGS. 1-2. FIG. 2 shows a partial cross-section
through the first of three bands of diverters.
[0017] As shown in FIGS. 1-2, the diverters have axes perpendicular
to the axis of rocket 10, such that the ejection of an end cap 16
from a diverter body 22 will produce a lateral reaction force. It
may be desirable to have from 1 to 64 diverters on the rocket 10.
It is preferred that the diverter axes be perpendicular to the
rocket axis and arranged at equal angles apart to simplify guidance
system calculations.
[0018] FIG. 3B shows additional details of the diverter 12 shown in
FIG. 1. As shown in FIG. 3B, the diverter 12 includes an end cap
16, made of strong steel, preferably of 17-4 PH CRES, condition
H-1025, with a clean passivated finish. The end cap 16 is attached
to the diverter body 22, and made of the same material and finish
as the end cap 16. A conventional adhesive bonding material 26,
such as a cyano acrylate adhesive, a suitable conventional
structural epoxy, or a conventional urethane adhesive, is applied
on the contacting surfaces between the end cap 16 and the diverter
body 22 to bond the end cap 16 to the diverter body 22 until the
time that the end cap 16 is ejected. One of ordinary skill would
also understand that the end cap 16 and the diverter body 22 could
be also attached by other techniques such as crimping. The end cap
16 is filled with a loosely loaded propellant 14, preferably 50 wt.
% Bullseye (pistol powder) and 50 wt. % HMX (an explosive ordnance
material), shotgun powder or the like. In an optional feature, the
invention provides a conventional adhesive backed paper closure,
which acts as a thermal closure 24, to seal and hold the propellant
14 in place for handling during assembly of the diverter 12.
[0019] The diverter body 22 contains the prime 18, preferably
zirconium potassium perchlorate, or a similar ordnance material.
The diverter body 22 has an aperture for housing the header
assembly 20. The header assembly 20 includes a glass substrate 44
from which two electrical leads 30 and 32 protrude to provide
electrical contact from a fireset (not shown) to a reactive
semiconductor bridge 40 mounted on the other end of the header
assembly 20. Electrical leads 30 and 32 are made of stainless steel
or KOVAR. Conventional shrink tubing 34 and 36 insulates the
electrical leads 30 and 32 from contacting and shorting to the
diverter body 22. Conventional potting material 28 retains the
shrink tubing 34 and 36 and fills the gap between the shrink tubing
34 and 36 and the diverter body 22. A conventional shunt 38
provides an electrical short when attached to the electrical leads
30 and 32 for safe handling of the diverter 12, and which shunt is
removed when the diverter 12 is attached to the fireset. FIG. 3A is
an electrical lead end view of the diverter 12 shown in FIG.
3B.
[0020] FIG. 4A shows the end of header assembly 20 from which
electrical leads 30 and 32 protrude. FIG. 4B shows a cross-section
through the header assembly 20, including the glass substrate 44,
the stainless steel sleeve or eyelet 42, and the electrical leads
30 and 32, and also through the semiconductor bridge 40. FIG. 4B
includes detail A shown as FIG. 5A, and a view B-B shown as FIG.
5B. FIG. 4C shows the end of the header assembly 20 on which the
semiconductor bridge 40 is mounted.
[0021] FIG. 5A is a close up and a cross-section of the
semiconductor bridge 40 mounted on the header assembly 20, labeled
detail A in FIG. 4B. FIG. 5B is an end view. The reactive
semiconductor bridge 40 is shown as mechanically attached on the
header assembly 20 by a non-conductive epoxy 47 such as Able Bond
84-3. Electrical leads 30 and 32 provide an electrical contact
point on the header assembly 20. Electrically conductive epoxy 46
and 45 such as Able Bond 84-1 electrically connect each of the
contact pads of the semiconductor bridge 40 to the electrical leads
30 and 32.
[0022] In operation, the reactive semiconductor bridge 40 provides
fast ignition of the prime 18 even when there is a gap between the
semiconductor bridge 40 and the prime 18. A suitable reactive
semiconductor bridge 40 is described in U.S. Pat. Nos. 5,847,307
and 5,905,226, which patents are hereby incorporated by
reference.
[0023] After the semiconductor bridge 40 is triggered based on
electrical signals from the fireset, hot plasma forms, igniting the
prime 18, which in turn ignites the propellant 14. Burning
propellant 14 produces gases, which are confined in the diverter 12
until the pressure builds to the point where the end cap 16 is
ejected. Ejecting the end cap 16 is more efficient than generating
an impulse by rocket propellant. The ability of the reactive
semiconductor bridge 40 to ignite the prime 18 across the gap
provides a margin of safety in case the shock or acceleration of
the launch causes the prime 18 to separate from the semiconductor
bridge 40. Diverters 12 can be built at low cost using this
technology.
[0024] In a preferred embodiment, the diverter body 16 has an
undercut 48 such that the mouth of the diverter body 22 is smaller
than the base as shown in FIG. 3B to hold the prime 18 in place
during high shock conditions and during ignition. When fired a
semiconductor bridge 40 tends to throw off the prime 18 rather than
ignite it unless the prime 18 is retained. The undercut 48 retains
the prime 18 in place during firing. The reactive semiconductor
bridge 40 allows a gap between the semiconductor bridge 40 and the
prime 18. It should be noted that the reactive semiconductor bridge
40 ignites the prime 18 across a gap, but not necessarily if the
prime 18 is allowed to dynamically shift away from the
semiconductor bridge 40 during the firing process.
[0025] Methods of the present invention provide the following
steps: a firing signal from the fireset is transmitted to the
electrical leads 30 and 32 of the diverter 12 when the shunt 38
removed. The voltage level of fire signal required depends upon the
type of the semiconductor bridge 40 mounted on the header assembly
20. The firing signal can be supplied by many methods including
applying one of the following:
[0026] 1) A constant current of 1 to 10 amps for less than 1 ms.
The actual current will depends on the sensitivity and type of
semiconductor bridge used.
[0027] 2) A capacitive discharge of, e.g., approximately 25 volts
from a 40-microfarad capacitor would be typical for driving a
semiconductor bridge, but values down to 3 volts and capacitor
values down to less than 1 microfarad are possible when highly
sensitive semiconductor bridges are used. Higher voltages, voltages
up and greater than 500 volts can be used with junction
semiconductor bridges that have DC blocking.
[0028] 3) A voltage signal whose value depends on the semiconductor
bridge type, properties, and characteristics.
[0029] The firing signal causes the semiconductor bridge 40 to
generate hot plasma (>2000 F) that ignites the prime 18. The
prime 18 is designed to ignite promptly when driven by the
semiconductor bridge 40 and generate in less than 100 microseconds
hot particles and heat. The hot particles and heat from the ignited
prime ignite the propellant 14. The propellant 14 is designed to
rapidly burn resulting in a rapid pressure rise in the volume
confined by the end cap 16 and diverter body 22. Each diverter 12
is contained within a barrel as shown in FIGS. 1-2. The electrical
lead end of the barrel is closed to match the taper at the back of
the diverter 12. The taper is provided on the diverter 12 so the
diverters can be placed close together. A slot, not shown, is cut
in the side of the back of the barrel to allow the electrical wires
to exit and make connection to the fireset. The opposite end of the
barrel is open as shown in FIGS. 1-2. As the pressure builds inside
the diverter 12 produced by the burning of the prime 18 and the
propellant 14, the end cap 16 outer diameter swells and seals
against the inner diameter of the barrel defined by the rocket 10.
Also the pressure forces the diverter body 22 back against the
taper sealing this potential exit path for hot gas. The header
assembly 20 is mounted on the diverter body 22. As the pressure
within the diverter 12 continues to increase from the burning of
prime 18 and propellant 14, the force on the end cap 16 reaches a
point where the end cap 16 separates from the diverter body 22 and
is accelerated down the barrel and ejected. Ejecting the end cap 16
results in a reaction force, that is, the diverting force.
Additionally, diverting force is created by the reactive forces
from the ejection of the hot gases from the burning of the prime 18
and the propellant 14 out of the barrel similar to the operation of
a rocket.
* * * * *