U.S. patent application number 10/855322 was filed with the patent office on 2007-07-12 for process and plant for destroying solid-propellant rocket motors.
This patent application is currently assigned to SNPE Materiaux Energetiques. Invention is credited to Marie Gaudre, Eric Marchand, Jean-Michel Tauzia, Jean-Louis Trichard.
Application Number | 20070161844 10/855322 |
Document ID | / |
Family ID | 33443260 |
Filed Date | 2007-07-12 |
United States Patent
Application |
20070161844 |
Kind Code |
A1 |
Gaudre; Marie ; et
al. |
July 12, 2007 |
PROCESS AND PLANT FOR DESTROYING SOLID-PROPELLANT ROCKET MOTORS
Abstract
Described is a process and a plant for destroying rocket motors,
including in particular the following steps and stations: cutting
of the motor into sections; cooling of the sections containing
propellant by immersion in a cryogenic liquid; and fragmenting and
extraction of the cooled propellant by elastic deformation of the
casing of the section. The propellant fragments are recovered for
subsequent treatment and the casings are deactivated before being
scrapped.
Inventors: |
Gaudre; Marie; (Le Haillan,
FR) ; Marchand; Eric; (St. Medard en Jalles, FR)
; Tauzia; Jean-Michel; (Blanquefort, FR) ;
Trichard; Jean-Louis; (St. Medard en Jalles, FR) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
SNPE Materiaux Energetiques
Paris
FR
|
Family ID: |
33443260 |
Appl. No.: |
10/855322 |
Filed: |
May 28, 2004 |
Current U.S.
Class: |
588/403 ;
86/50 |
Current CPC
Class: |
F42B 33/06 20130101 |
Class at
Publication: |
588/403 ;
086/050 |
International
Class: |
F42B 33/00 20060101
F42B033/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 10, 2003 |
FR |
03 08474 |
Claims
1. (canceled)
2. The process of claim 15, wherein the sections containing
propellant have a length/outside diameter ratio of less than or
equal to 2.5.
3. The process of claim 15, wherein the motor is cut up by at least
one high-pressure liquid jet.
4. The process of claim 3, wherein, for cutting up the motor, the
latter is immersed in a tank containing the same liquid as that
used for supplying a spray rail delivering several jets that are
prepositioned relative to the motor.
5. The process of claim 15, wherein the sections containing
propellant are cooled by immersion in a cryogenic liquid.
6. The process of claim 5, wherein the cryogenic liquid is liquid
nitrogen.
7. The process of claim 5, wherein the sections containing
propellant are cooled to a temperature between about -100.degree.
C. and about -80.degree. C.
8. The process of claim 15, wherein one or more fragments of
propellant are collected in a receptacle.
9. The process of claim 5, wherein each empty section is
deactivated by burning off traces of propellant residues, with
recovery and scrubbing of flue gases.
10. The process of claim 5, wherein each empty section is
deactivated by immersing the section in a liquid that dissolves the
oxidizing charge.
11-12. (canceled)
13. The process of claim 2, wherein the motor is cut up by at least
one high-pressure liquid jet.
14. The process of claim 2, wherein the sections containing
propellant are cooled by immersion in a cryogenic liquid.
15. A process for destroying a solid-propellant rocket motor of a
cast-bonded type, the motor having an axis, a casing, and a block
of propellant including a binder, comprising: cutting up the motor
into sections perpendicular to the axis; withdrawing sections not
containing the propellant; cooling sections containing the
propellant to a temperature of at least about 20.degree. C. below a
glass transition temperature range of the propellant binder;
fragmenting the propellant and separating the propellant from the
casing of each section containing the propellant by elastic
deformation of the casing, thereby emptying the casing of the
propellant; recovering the emptied casing sections; deactivating
propellant residues of the empty casing sections; and recovering
the fragmented propellant for a subsequent treatment.
16. The process of claim 15, wherein the elastic deformation is
carried out on the casing of each cooled section with the axis of
the cooled section being vertical.
17. The process of claim 16, wherein the axis of the casing of the
cooled section is held vertical by a jack having its axis
horizontal.
18. The process of claim 17, wherein the jack is a hydro pneumatic
jack.
19. The process of claim 17, wherein the jack bears on the casing
about one third along a length of the casing starting from the
bottom of the cooled casing section.
20. The process of claim 15, wherein the elastic deformation is
carried out by driving the casing of each cooled section between
two rolls forming a rolling mill.
Description
[0001] The present invention relates to the field of
solid-propellant rocket motors. It relates more particularly to the
destruction of reformed rocket motors, especially those that have
reached the limit of their operational use and have been removed
from service.
[0002] A solid-propellant rocket motor essentially comprises a
hollow cylindrical casing inside which is placed at least one block
of solid propellant--to simplify matters we will refer hereafter to
one block of propellant. One end of the casing is closed off by a
dome and the opposite end by a nozzle; the dome and the nozzle will
be regarded as forming part of the casing.
[0003] The rocket motors considered here are those for which the
block of solid propellant has been fastened to the casing and
cannot be removed simply from the casing. These are essentially
what are called "cast-bonded" motors for which the block of
propellant, during manufacture of the motor, is cast in and bonded
to the casing suitably prepared for this purpose. We shall liken to
this type of motor those for which the block of propellant,
prepared elsewhere, is introduced and fitted irreversibly into the
casing, this fitting operation being intentional or accidental. We
shall retain the expression "cast-bonded" rocket motors to denote
the motors treated in this invention.
[0004] The destruction of a rocket motor consists firstly in
placing it in a state such that it cannot fulfil its propulsion
function and then secondly in separating the casing from the
propellant in order to treat them separately, taking into account
the fact that only the propellant involves a pyrotechnic risk,
which requires special precautions and conditions in its treatment
for the purpose of scrapping or recycling certain components.
[0005] The problem more particularly tackled here is that of how to
destroy a very large number, typically several thousand, of rocket
motors; it is necessary to be able to treat several tens of motors
per day.
[0006] Both the destruction process and the destruction plant must
be capable of operating at a very high rate. What is therefore
required is a process with simple and rapid steps and an
unsophisticated plant.
[0007] In addition, the process and the plant must be reliable. An
incident occurring on a motor or part of a motor during one step of
the process must remain limited, or be able to be limited, to this
part of the motor, and to the location in the plant where the said
incident occurs. The incident must not propagate throughout the
plant and become catastrophic, owing to the large number of motors
necessarily present on the destruction site.
[0008] The prior art discloses several processes for destroying
rocket motors, but under conditions which do not correspond to the
problem posed, as we will see during the course of analysing these
processes.
[0009] U.S. Pat. No. 5,220,107 discloses the fragmentation of a
block of bare propellant, that is to say one not bonded to the
inside of the casing of a rocket motor, by cooling the block of
propellant down to a very low temperature and by using a crusher or
a press to fragment it.
[0010] U.S. Pat. No. 5,025,632 discloses the extraction of the
propellant from a cast-bonded rocket motor with a central channel
using at least one jet of cryogenic liquid. This destruction
process, derived from a "water knife", is very lengthy and does not
meet the requirement for a high work rate. In addition, it is
potentially hazardous as the work is carried out on an entire
rocket engine.
[0011] U.S. Pat. No. 5,552,093 discloses the extraction of the
propellant from a cast-bonded rocket motor that has been cooled by
immersion in liquid nitrogen. The block of propellant is
fragmented, especially by applying mechanical shocks to it. The
application of shocks to the propellant, even when cooled, is still
potentially hazardous, and this hazard is greater owing to the fact
that, here again, the work is carried out on an entire motor. In
addition, for relatively long motors, the possibility of fragments
becoming jammed in the casing, and requiring further handling
operations to extract them from the casing, cannot be ruled
out.
[0012] The present invention aims to solve the difficulties that
these various processes do not take into consideration when it is
necessary to devise a destruction process to be carried out at a
very high rate, and to do so without unreasonably increasing the
number of plants operating in parallel in order to destroy a large
number of rocket motors.
[0013] According to the invention, the process for destroying a
solid-propellant rocket motor comprises the following steps: [0014]
the motor is cut up into sections perpendicular to the axis of the
motor; [0015] the sections not containing propellant are withdrawn
from the rest of the sequence; [0016] the sections containing
propellant are cooled to a temperature very much below the glass
transition temperature range of the propellant binder; [0017] the
propellant is separated from the casing of each section, i.e. the
section is thus emptied of the propellant that it contained; [0018]
the empty casing sections are recovered for a supplementary step of
deactivating any propellant residues; and [0019] the fragmented
propellant is recovered for subsequent treatment.
[0020] The present process therefore relates to solid-propellant
rocket motors for which the block of propellant is fastened to the
casing; the motors involved in this process do not include an
ignition device--this is disconnected and removed from the motor in
a preparatory operation before the motors are delivered to the
destruction site. The rocket motor casing is either entirely made
of metal or a composite material. The block of propellant has a
central channel extending over its entire length or only part of
it. In the latter case, that portion on the side away from the
nozzle does not have a channel. The block of propellant may
possibly be a end burning block, that is to say it does not have a
central channel.
[0021] The cut-up sections of the motor are of two types: [0022]
sections without propellant: in general, there is only one section
of this type per motor. This section carries all or part of the
nozzle and it contains no pyrotechnic material; this type of
section is removed from the present sequence; and [0023] sections
with propellant: the cut-up portion of the block remains bonded to
the cut-up portion of the casing; this type of section will undergo
the other steps of the process. At least one of the ends of the
section is wide open, i.e. the diameter of the opening is
approximately equal to the motor calibre.
[0024] Advantageously, the sections containing propellant have a
section length "1"/section outside diameter "d" ratio of less than
or equal to 2.5 (i.e. l/d.gtoreq.2.5).
[0025] All the methods known for cutting up rocket motors into
sections may be used. However, owing to the need for a high
operating rate and also the safety requirements, it will be
advantageous to employ methods using at least one jet of
high-pressure liquid to which suitable abrasive substances may
optionally be added.
[0026] Preferably, to increase the efficiency of the operation, the
process uses several jets placed in parallel and prepositioned
relative to the motor in order to cut it up into the various
sections in a single operation.
[0027] Also preferably, in order to increase safety, for cutting up
the motor the latter is immersed in the same liquid as that used
for the jets; usually the liquid used is water.
[0028] The liquid and the casing and propellant chips resulting
from the cutting operations are periodically removed for the
purpose of suitable treatments.
[0029] The sections containing propellant are, using appropriate
handling means, transported and immersed in a bath of a cryogenic
liquid that is inert with respect to the section components. In
general, the cryogenic liquid used is liquid nitrogen.
[0030] The sections are immersed for a time long enough for the
casing and the propellant to be cooled quite substantially and for
the differential contractions between casing and propellant to
create tensile stresses that crack the propellant and also debond
it from the casing.
[0031] Typically, the intended final temperature for the motor
section is at least 20.degree. C. below the glass transition
temperature range of the propellant binder. Advantageously, the
intended temperature is between about -100.degree. C. and about
-80.degree. C. for both the propellant and the casing.
[0032] The sufficiently cooled sections are then sent to a station
for extracting the propellant, which has been embrittled by the
cold. The propellant is extracted by making the casing undergo
slight deformation. Such deformation remains within the elastic
range of deformation of the casing at this temperature. The
propellant breaks up into rather coarse fragments, typically of the
size of a clenched fist.
[0033] The section is placed with its axis vertical and the
propellant fragments drop out under gravity and are recovered
either on a conveyor belt or in a receptacle containing water in
order to make the propellant fragments inert. Since the motor
section has a relatively short length compared with its diameter,
i.e. l/d.gtoreq.2.5, the propellant fragments do not become jammed
in the casing.
[0034] According to a first variant, the cooled motor section, with
its axis vertical and its larger-diameter opening directed
downwards, is placed between a stop and a jack head. The axis of
the jack is horizontal and perpendicular to the axis of the motor
section. The displacement of the jack head is calculated so that
the deformation of the casing remains within its elastic
deformation range.
[0035] According to another variant, the cooled motor section is
driven between two rolls forming a rolling mill. These rolls are
suitably spaced apart in order to impose, here again, a deformation
that remains within the elastic deformation range of the casing.
The rolls drive the motor section and deform it slightly, from the
bottom of the said section up to its top, thereby making it easier
to extract the propellant fragments by gravity.
[0036] The empty casing section possibly has a few thin residual
traces of propellant that have remained bonded at certain points
inside the casing. The empty section is recovered in order to
undergo a subsequent step of deactivating such residues.
[0037] Advantageously, this deactivation is carried out in a closed
chamber comprising burners whose flames burn off the traces of
propellant. The flue gases are collected and scrubbed with
water--no gaseous effluent is therefore discharged into the
atmosphere. The scrubbing water is collected in order to be treated
and decontaminated using known processes.
[0038] Preferably, when the oxidizing charge of the propellant is
soluble in a liquid, the deactivation of any propellant residues
adhering to the inside of the casing is carried out by immersing
the empty casing section in the said liquid. When the oxidizing
charge has dissolved in the liquid, there then remain, on the
inside wall of the casing, only bits of matrix consisting of binder
and combustible charge of no pyrotechnic hazard. The rate of
diffusion of the oxidizing charge and of its dissolution in the
liquid is advantageously speeded up by heating the liquid. The
liquid containing the oxidizing charge in solution is recovered for
subsequent treatment by known processes. Frequently, the oxidizing
charge is ammonium perchlorate and the liquid used for dissolving
it is water.
[0039] Having many rocket motors to be destroyed, it may seem
paradoxical to increase the number of objects to be treated by
cutting a motor up into sections.
[0040] From the safety standpoint, the sections without propellant,
which do not entail any pyrotechnic risk, are removed from the
sequence of operations. A section containing propellant is very
short and will not be propulsive in the event of accidental
ignition. It will not undergo any random and inopportune
displacement that can make the incident propagate to any other
station. However, precautions must be taken as regards thermal
effects.
[0041] From the standpoint of efficiency, this
cutting-into-sections operation contributes to the efficiency of
the following steps of the process: [0042] the sections are cooled
more rapidly than an entire motor because of a lower mass and a
larger area for heat exchange with the cryogenic liquid; [0043]
since the sections are short, the fragments drop out by gravity and
do not run the risk of becoming jammed, as exists in a complete
rocket motor; and [0044] the deactivation of the propellant
residues carried out on empty casing sections is easier than that
carried out on the complete casing of a motor, and this is so
whatever the process adopted.
[0045] The propellant fragments obtained after elastic deformation
of the casing are in general rather coarse, namely a few
centimetres or about the size of a clenched fist. Before passing to
the next step of the propellant treatment, it is necessary to carry
out finer milling of the said fragments so as to obtain particles
of propellant, the particles having dimensions of the order of at
most a centimetre and preferably a few millimetres.
[0046] This milling may be carried out in various ways, but
preferably knife mills are used, the milling advantageously being
carried out under a water spray.
[0047] The next step in the treatment of the propellant, thus
particulated, is the dissolution of the oxidizing charge in a
suitable liquid, for example water when the oxidizing charge is a
perchlorate.
[0048] To increase the rate of dissolution, the latter is
preferably carried out in a well-stirred and thermally regulated
reactor.
[0049] The liquid that contains the oxidizing charge in solution is
separated from the solid residue; the latter comprises the binder
and the optional combustible charge--there is no pyrotechnic risk.
The solid residue is either directly discharged into a technical
burial centre or is reutilized in order to extract the metallic
combustible charge therefrom after conventional known treatments
for industrial waste.
[0050] The liquid is either treated by biodegradation processes,
such as those described in patent FR 2 788 055 or its corresponding
patent U.S. Pat. No. 6,328,891, in order to degrade the oxidizing
charge, or treated in order to reutilize the said oxidizing charge
and to recrystallize it by known processes.
[0051] The invention will be explained in further detail below by
means of figures that show a plant for carrying out the
process.
[0052] FIG. 1 shows schematically a plant for implementing the
process.
[0053] FIG. 2 is a drawing showing the principle of a device for
fragmenting the propellant after the section has been cooled.
[0054] FIG. 1 shows schematically the succession of various
stations for implementing the process: FIG. 1a) in plan view and
FIG. 1b) in side view.
[0055] The rocket motors are brought into a storage area,
identified, for traceability of the operation, placed one by one on
a conveyor, and introduced one by one into the plant via a first
airlock.
[0056] In the cutting station 1, the motor is immersed in a tank
containing water and positioned on a rig that rotates relative to a
suitably placed spray rail delivering several high-pressure jets
and the motor is cut up into sections. High-pressure spray rails
are produced with standard equipment, for example Digital Control
equipment, delivering high-pressure jets, the pressure being about
300 MPa, by means of two pumps. In general, there will be one
section that does not contain propellant but a large part of the
nozzle; this section containing no pyrotechnic substance is removed
from the sequence.
[0057] The other sections 10 of the motor are taken up by another
conveyor and carried, through an airlock, into the cooling station
2 where they are cooled by immersion in the cryogenic liquid. This
station essentially comprises a long bath in which several sections
suitably spaced apart are immersed. The sections are moved along as
the process takes place and they therefore remain a long time in
the liquid, thereby cooling them down to temperatures of about
-100.degree. C.
[0058] The sections are directed, one by one, via another airlock,
to the fragmentation station 3 where the propellant bonded to the
casing section is fragmented. An example of a device is illustrated
in greater detail in FIG. 2.
[0059] In this station, the suitably oriented section is deformed
by compressing the casing. The propellant, embrittled and cracked
by the cooling, fragments. The fragments are recovered for
subsequent treatment.
[0060] The casing sections emptied of propellant are directed to a
residue deactivation station 6. In this example, the deactivation
of the sections is carried out by immersing the said sections in a
tank containing water.
[0061] The propellant fragments are directed to a fine milling
station 4 using knife mills with water spray. Standard
high-performance machines, with a few safety modifications, can
treat up to 1000 kg of propellant per hour.
[0062] The particles obtained after fine milling are introduced, in
the dissolution station 5, into a reactor of large volume, the said
reactor being well stirred and thermally regulated in order to
increase the rate at which the oxidizing charge dissolves in the
water.
[0063] In this diagram, all the various handling means have not
been shown in detail, nor have the devices for opening and closing
the airlocks of the plant, nor the services for each work
station.
[0064] FIG. 2a) shows schematically a side view and FIG. 2b) a plan
view of an apparatus 11 for extracting the propellant from a cooled
rocket motor section 10.
[0065] The apparatus essentially comprises a rectangular stand 13,
anchored on four feet, with a stop 14 on one of the sides of the
stand and a hydropneumatic jack 15 fastened on the opposite side,
the jack being placed horizontally.
[0066] The rocket motor section 10 to be treated is held, with its
axis vertical, by a handling means shown schematically by the
reference 12. The said handling means brings the motor section 10
between the stop 14 and the jack rod 16.
[0067] The jack rod 16 bears on the casing of the motor section
approximately one third the way along its length starting from the
bottom of the section. The displacement of the jack rod 16 is
defined in order to subject the casing to a deformation which
remains within the elastic deformation range of the latter, to
fragment the cold propellant and to separate it from the
casing.
[0068] A receptacle 17, containing water in order to make the
propellant fragments that drop simply under gravity inert, is
placed beneath the motor section, the said receptacle 17 being
shown only in FIG. 2a).
[0069] This apparatus is placed in a suitable room with entry and
exit airlocks and all the services needed for remote-controlled
operation.
* * * * *