EP1496333A1 - Method and device for destroying solid propellant motors - Google Patents

Abstract

The method involves cutting a scrapped solid propellant engine into sections, and withdrawing sections that do not contain propellant. The sections containing propellant are cooled at a very low temperature by immersing it in a cryogenic liquid. The propellant is fragmented and separated from the envelope of each section. The sections of empty envelope are collected for deactivating residues. An independent claim is also included for an installation for the destruction of a solid propellant engine.

Description

The present invention is in the field of solid propellant engines. It concerns more especially the destruction of reformed engines including engines that have reached the limit operational use and which are removed from service.

A solid propellant engine includes basically a cylindrical shell hollow to inside which is placed at least one block of solid propellant, to simplify we will say by the following a block of propellant. One end of the envelope is closed by a dome and the opposite end by a nozzle; the dome and the nozzle will be considered as part of the envelope.

The engines considered here are engines for which the solid propellant block has been joined with the envelope and can not be removed simply from the envelope. It's basically engine said "molded-glued" for which the block of propellant is molded and glued during the manufacture of the engine in the envelope properly prepared for this purpose. We assimilate to this type of engine those for which the propellant block, prepared otherwise, is introduced and stuck irreversibly in the envelope, this wedging being wanted or accidental. We will keep the expression engine molded glued to designate the motors treated in this invention.

The destruction of an engine consists of first time to put it in such a state that it does not can ensure its propulsion function and then in a second step to separate the envelope and the propellant to treat them separately, given that only the propellant presents a pyrotechnic hazard that requires precautions and special conditions in his treatment for the purpose of scrapping or recycling certain elements.

The problem of destruction more particularly addressed here is that of the destruction of a very large number of engines, typically several thousand; he must be able to process dozens of engines by day.

The process and the destruction facility must be able to operate at a very high cadence: it is therefore requested a process with steps simple and fast and a rustic installation.

In addition, the process and the installation must be safe. An incident on an engine or part of an engine during a process step must remain limited or can be limited to this part of the engine and to the place of the installation where it takes place. The incident does not must not spread to the entire installation and become catastrophic given the large number of engines necessarily present on the destruction site.

The state of the art describes several processes of engine destruction but in conditions we will see during the analysis of these processes, which does not do not fit the problem.

US Patent 5,220,107 discloses fragmentation of a block of naked propellant, that is to say not glued to inside the casing of an engine, by cooling at very low temperature of the propellant block and use of a grinder or press for fragment.

U.S. Patent 5,025,632 discloses the extraction of propellant of a molded-glued engine with a central channel using at least one jet of cryogenic liquid. This destruction process derived from the "water knife", is very long and does not meet the need for great pace of work. Moreover, it is potentially dangerous because we work on a whole engine.

U.S. Patent 5,552,093 discloses the extraction of propellant of a molded-and-glued engine that has been cooled by immersion in liquid nitrogen: the block is fragmented by shocks applied in particular to the block of propellant. The application of shocks on propellant even cooled remains potentially dangerous and this danger is increased by the fact that, here again, an entire engine. Moreover for relatively long it is not excluded that fragments get stuck in the envelope and require manipulations to extract them from the envelope.

The present invention aims to solve difficulties which are not taken into account by these various processes when one is led to design a destruction process at a very high rate and this without unreasonably multiplying the facilities running in parallel to destroy a lot engines.

• le moteur est découpé en tronçons perpendiculairement à l'axe du moteur,
• les tronçons ne contenant pas de propergol sont retirés de la suite de la séquence,
• les tronçons contenant du propergol sont refroidis à une température très inférieure au domaine de température de transition vitreuse du liant du propergol,
• le propergol est séparé de l'enveloppe de chaque tronçon, le tronçon est ainsi vidé du propergol qu'il contenait,
• les tronçons d'enveloppe vides sont récupérés pour une étape complémentaire de désactivation des éventuels résidus de propergol,
• le propergol fragmenté est récupéré pour un traitement ultérieur.

The method of destroying a solid propellant engine according to the invention comprises the following steps:

• the engine is cut into sections perpendicular to the axis of the engine,
• sections not containing propellant are removed from the rest of the sequence,
• the sections containing propellant are cooled to a temperature much lower than the glass transition temperature range of the propellant binder,
• the propellant is separated from the envelope of each section, the section is thus emptied of the propellant that it contained,
• the empty envelope sections are recovered for a complementary step of deactivating any propellant residues,
• the fragmented propellant is recovered for further processing.

The present method therefore relates to solid propellant for which the propellant block is integral with the envelope; the engines that go into this method does not include an ignition device: it is disassembled and removed from the engine in an operation preparation before delivery of the engines to the site of destruction. The engine casing is either fully metal, or composite material. The block of propellant has a central channel that spans whole length or only part of it: in this last case the portion of the side opposite the nozzle no channel. The propellant block can be possibly full over its entire length, that is to say does not have a central channel.

• des tronçons sans propergol : en général il y a un seul tronçon de ce type par moteur, ce tronçon porte tout ou partie de la tuyère, il ne contient pas de matériau pyrotechnique, ce type de tronçon est retiré de la présente séquence,
• des tronçons avec du propergol : la portion découpée du bloc est restée collée à la portion découpée de l'enveloppe, ce type de tronçon va suivre les autres étapes du procédé. Au moins une des extrémités du tronçon est grande ouverte : c'est-à-dire que le diamètre de l'ouverture est sensiblement égal au calibre du moteur.

The sections cut in the engine are of two types:

• sections without propellant: generally there is only one section of this type by motor, this section carries all or part of the nozzle, it does not contain pyrotechnic material, this type of section is removed from the present sequence,
• sections with propellant: the cut portion of the block remained glued to the cut portion of the envelope, this type of section will follow the other steps of the process. At least one end of the section is wide open: that is to say that the diameter of the opening is substantially equal to the size of the motor.

Advantageously, the sections containing propellant have a ratio length "1" of the section on outside diameter "d" of the section less than or equal to 2.5, (1 / d ≤ 2.5).

All known methods to cut out Engines in sections are usable. However, account given the need for a high pace and also security requirements, it will be advantageous to resort to methods using at least one liquid jet at high pressure with possibly adding abrasive products adapted.

Preferably to increase the yield of the operation the process uses several jets arranged in parallel and prepositioned with respect to the motor to cut the different sections into one surgery.

Preferentially, to increase the safety, to be cut off the engine is immersed in the same liquid used for the jets; the more commonly the liquid used is water.

The liquid and the chips of envelope and propellant resulting from cutting operations are regularly withdrawn for the purpose of appropriate treatment.

The sections containing propellant are, using appropriate means of handling, transported and immersed in a bath of a neutral cryogenic liquid vis-à-vis the section components; usually the Cryogenic liquid used is liquid nitrogen.

The immersion of the sections lasts long enough to that the cooling of the envelope and the propellant be quite important and that the contractions differentials of the envelope and propellant create tensions cracking and cracking the propellant and also taking off from the envelope.

Typically the target end temperature for the engine section is at least 20 ° C below glass transition temperature range of the binder propellant. Advantageously, we aim for a temperature between about -100 ° C and about -80 ° C for the propellant and the envelope.

Then the sufficiently cooled sections are directed to a station to extract the propellant, weakened by the cold. The propellant is extracted imposing slight deformations on the envelope: these deformations remain in the elastic domain of deformation of the envelope at this temperature. The propellant breaks into fairly large fragments, typically the size of a closed fist.

The stretch has been arranged vertical axis and the propellant fragments fall by gravity and are recovered either on a conveyor belt or in a receptacle containing water to render inert the propellant fragments. The engine section having a relatively small length compared to its diameter, 1 / d ≤ 2.5, the propellant fragments do not get stuck in the envelope.

According to a first variant, the engine section cooled, vertical axis and opening of larger diameter directed downwards, is arranged between a stop and a cylinder head. The cylinder axis is horizontal and perpendicular to the axis of the section of engine. The displacement of the cylinder head is calculated so that the deformation of the envelope remains in the field of elastic deformation of the envelope.

According to another variant, the engine section cooled is driven between two rollers rolling mill, these rollers are suitably spaced for impose, again, a deformation that remains in the field of elastic deformation of the envelope. The rollers drive and slightly deform the section from the bottom of said section to its part high which facilitates the extraction of fragments of propellant by gravity.

The empty envelope section optionally comprises some residual traces of thin propellant remained stuck in certain points of inside the envelope. The empty stretch is recovered for a subsequent step of disabling such residues.

Advantageously this deactivation is done in a closed chamber that includes burners whose flames burn the traces of propellant. The fumes are folded and washed with water: therefore no gaseous effluent is not released into the atmosphere. The wash waters are collected to be processed and decontaminated according to known methods.

Preferably, when the oxidizing charge of Propellant is soluble in a liquid, the deactivation any propellant residues adhering to the inside of the envelope is done by dipping the empty envelope section in said liquid. When the oxidizing charge is dissolved in the liquid, it does not remains more on the inner wall of the envelope than matrix flaps consisting of binder and filler fuel without pyrotechnic danger. The kinetics of diffusion of the oxidizing charge and its dissolution in the liquid is advantageously accelerated in heating the liquid. The liquid containing the charge oxidant in solution is recovered for treatment subsequently by known methods. Frequently the charge oxidant is ammonium perchlorate and the liquid used to dissolve it is water.

Having a lot of engines to destroy, he can paradoxical to multiply the objects to be treated in cutting the engine into sections.

From a security point of view, we withdraw from sequence of operations the sections without propellant that do not present a pyrotechnic risk. A section propellant is relatively short and will not be not propulsive in case of accidental ignition: it will not have disordered and untimely movements could spread the incident to an entire post. However precautions must be taken with regard to the effects thermal.

• les tronçons sont refroidis plus rapidement qu'un moteur entier : masse plus faible, surface d'échange thermique avec le liquide cryogénique plus importante,
• les tronçons étant court les fragments tombent par gravité et ne présentent pas de risque de coincement existant sur un moteur complet,
• la désactivation des résidus de propergol faite sur des tronçons d'enveloppe vides est plus facile que celle faite sur l'enveloppe complète d'un moteur et cela quel que soit le procédé adopté.

From an efficiency point of view, this division into sections contributes to that of the following steps of the process:

• the sections are cooled faster than an entire engine: lower mass, heat exchange surface with the larger cryogenic liquid,
• the sections being short the fragments fall by gravity and do not present any risk of jamming existing on a complete engine,
• the deactivation of the propellant residues made on empty sections of the casing is easier than that made on the complete casing of an engine, whatever the method adopted.

The propellant fragments obtained after the elastic deformation of the envelope are usually pretty big: a few inches, about the size with a closed fist. To move to the next stage of propellant treatment, it is necessary to proceed to finer grinding of said fragments so as to obtain grains of propellant, grains whose dimensions are of the order of not more than one centimeter and preferentially a few millimeters.

This grinding can be done in different ways but preferentially we use grinders to knives and advantageously grinding is done under water spray.

The next stage of propellant treatment, as well put in grains, is the dissolution of the oxidizing charge in a suitable liquid, for example water when the oxidizing charge is perchlorate.

Preferably to accelerate the kinetics of dissolution it is done in a reactor perfectly agitated and thermoregulated.

The liquid that contains the oxidative charge in solution is separated from the solid residue; this last includes the binder and the possible fuel charge, it does not present a pyrotechnic hazard. The residue solid is either directly landfilled in a landfill, be upgraded to extract the metal fuel charge after known and conventional treatments for waste industrial.

The liquid is either treated by biodegradation such as that described in the patent FR 2 788 055 or its correspondent US 6 328 891 for degrade the oxidative charge, be treated for revalorize said oxidizing charge and recrystallize it by known methods.

Below the invention is explained in more detail using figures representing an installation for the realization of the process.

Figure 1 schematically represents a installation for the implementation of the method.

Figure 2 is a blueprint of a propellant fragmentation facility after cooling of the section.

Figure 1 schematically represents the succession of different posts for the implementation of the process. Figure 1a) in plan, Figure 1b) of profile.

The engines are brought to a storage workshop, identified for the traceability of the operation and are placed one by one on a conveyor and are introduced, one to one, through a first airlock in the facility.

At the cutting station 1 the engine is immersed in a tray containing water and positioned on a bench turning in relation to a ramp of several jets to high pressure suitably arranged: the engine is cut into sections. The high pressure ramps are made with standard equipment eg DIGITAL CONTROL, supplying high-pressure jets, approximately 300 MPa using two pumps. In general, there is a section that does not contain propellant but a great part of the nozzle, that section not containing pyrotechnic product is removed from the sequence.

The other sections 10 of the engine are hooked to another conveyor and pass through an airlock to the cooling station 2 by immersion in the liquid cryogenic: this post essentially includes a bath of great length in which are immersed several sections suitably spaced; the sections move as the process unfolds and so stay long in the liquid which promotes cooling to temperatures about -100 ° C.

By another lock the sections are directed, one to one, to the fragmentation station 3 of the bonded propellant in the envelope section. An example of an installation is described in more detail in FIG.

At this station the suitably oriented section is deformed by compression of the envelope: the propellant, weakened, cracked and cracked by cooling fragments. The fragments are recovered for a further processing.

The sections of empty propellant casing are directed to a residue deactivation station 6. The deactivation of sections is, in this example, made by immersing said sections in a vessel containing some water.

The propellant fragments are directed to a fine grinding station 4 using knife mills with water spray. Standard devices powerful, with some security adaptations, can treat up to 1000kg / hour of propellant.

The grains obtained after fine grinding are introduced to the dissolution station 5 in a reactor of large volume, said reactor is perfectly agitated and thermoregulated to increase the kinetics of dissolution the oxidizing charge in the water.

On this scheme are not shown in detail all the different means of manipulation, nor the devices for opening and closing airlock the installation, nor the servitudes of each job.

Figure 2 schematically represents views a) in profile and b) in plan of an extraction apparatus 11 of the propellant of a cooled engine section 10.

The apparatus essentially comprises a frame rectangular 13, anchored on four feet with a stop 14 on one side of the frame and a hydropneumatic cylinder 15 fixed on the opposite side; the cylinder is arranged horizontally.

The motor section 10 to be treated is hooked, vertical axis to a handling means schematized by the reference 12. Said handling means brings the section motor 10 between the stop 14 and the cylinder rod 16.

The cylinder rod 16 is supported on the envelope from the engine section to about one-third of its height from the bottom of the section. Moving the stem jack 16 is determined to impose a deformation to the envelope that remains in the elastic domain of deformations of it and fragment the propellant cold and separate it from the envelope.

A receptacle 17, containing water to make inert the propellant fragments that fall by simple effect of gravity is placed under the stretch of engine; said receptacle 17 is only shown in Figure 2a).

This unit is placed in a suitable room with entry and exit lockers and all easements necessary for remote operation.

Claims (12)

A method of destroying a solid propellant engine, said molded-bonded motor consisting essentially of a propellant block and an envelope, said method is characterized in that it comprises the following steps: the engine is cut into sections perpendicular to the axis of the engine, sections not containing propellant are removed from the rest of the sequence, the sections containing propellant are cooled to a temperature much lower than the glass transition temperature range of the propellant binder, the propellant is fragmented and separated from the envelope of each section, the section is thus emptied of the propellant that it contained, the empty envelope sections are recovered for a complementary step of deactivating the residues, the fragmented propellant is recovered for further processing. A method of destroying solid propellant engine according to claim 1 characterized in that the sections containing propellant have a length to outer diameter ratio less than or equal to 2.5. A method of destroying solid propellant engine according to claim 1 or 2 characterized in that the cutting of the engine is by at least one jet of high pressure liquid. A method of destroying solid propellant engine according to claim 3 characterized in that for cutting the motor is immersed in a tank containing the same liquid as that used to feed a ramp of several jets prepositioned relative to the engine. A method of destroying solid propellant engine according to claim 1 or 2 characterized in that the sections containing propellant are cooled by immersion in a cryogenic liquid. A method of destroying solid propellant engine according to claim 5 characterized in that the cryogenic liquid is liquid nitrogen. A method of destroying solid propellant engine according to claim 5 characterized in that the section is cooled to a temperature of between about -100 ° C and about -80 ° C. A method of destroying solid propellant engine according to claim 5 characterized in that the envelope of each cooled section is subjected to elastic deformation efforts to fragment the propellant whose fragments are collected in a receptacle. A method of destroying solid propellant engine according to claim 5 characterized in that each empty section is deactivated by burning traces of propellant residues with recovery and washing of fumes. A method of destroying solid propellant engine according to claim 5 characterized in that each empty section is deactivated by soaking the section in a liquid dissolving the oxidizing charge. Plant for the destruction of a solid propellant engine, said engine consisting essentially of a block of propellant stuck in an envelope, characterized in that it comprises: an engine preparation station communicating via a decoupling chamber with, a cutting station (1) in sections of said engine, a cooling station (2) sections containing propellant, at least one propellant fragmentation station (3) with recovery of the propellant fragments and empty envelope sections, a station (6) for deactivating the propellant residues of the empty envelope sections. Plant for the destruction of solid propellant engine according to claim 11, characterized in that it comprises: a station (4) for fine grinding of the propellant fragments, a station (5) for dissolving the oxidizing charge of the finely ground propellant.

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