WO2010025178A1

WO2010025178A1 - Shape memory safe and arm system and vehicle incorporating same

Info

Publication number: WO2010025178A1
Application number: PCT/US2009/055032
Authority: WO
Inventors: Roger W. Melin; Michael L. Fortner
Original assignee: Lockheed Corp; Lockheed Martin Corp
Current assignee: Lockheed Martin Corp
Priority date: 2008-08-27
Filing date: 2009-08-26
Publication date: 2010-03-04
Anticipated expiration: 2011-02-27

Abstract

A shape memory safe and arm system includes a fuze and a shape memory switch operably associated with the fuze. A vehicle includes a skin and a shape memory safe and arm system disposed within the skin.

Description

SHAPE MEMORY SAFE AND ARM SYSTEM AND VEHICLE INCORPORATING

SAME

Technical Field

The present invention relates in general to the field of systems for preventing inadvertent activation of munition systems.

Description of the Prior Art

Vehicles, such as missiles, rockets, torpedoes, and the like, often carry munitions to be applied to a target as need be. It is desirable for such a munition to be in an unarmed state prior to deployment of the vehicle for safety reasons. Accordingly, "safe and arm" systems have been developed that arm a munition only after a set of unrelated events have occurred. Such conventional safe and arm systems, however, have complex configurations and some are active devices, i.e., the devices require some type of power provided by the vehicle in order to operate.

While there are many safe and arm systems well known in the art, considerable room for improvement remains.

Brief Description of the Drawings

The novel features believed characteristic of the invention are set forth in the appended claims. However, the invention itself, as well as a preferred mode of use, and further objectives and advantages thereof, will best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings, in which the leftmost significant digit(s) in the reference numerals denote(s) the first figure in which the respective reference numerals appear, wherein:

Figure 1 is a stylized, side, elevational view of an exemplary vehicle, in which a skin thereof has been partially removed to reveal components therein;

Figure 2 is a stylized, block diagram of an illustrative embodiment of a safe and arm system; Figures 3A, 3B, 4A, and 4B are stylized views depicting exemplary embodiments of a shape memory switch;

Figure 5A is a top, plan view of an illustrative embodiment of a polymeric shape memory operator for the switch of Figures 3A, 3B, 4A, and 4B;

Figure 5B is a side, elevational view of the polymeric shape memory operator of Figure 5A;

Figures 6A, 6B, 7A, and 7B are stylized views depicting alterantive, exemplary embodiments of a shape memory switch;

Figure 8 is a stylized, block diagram of an illustrative embodiment of shape and arm system of Figure 2; and

Figure 9 is an end, elevational view of an illustrative embodiment of the propulsion system of Figure 8, in which a shape memory switch is incorporated into a pole piece thereof.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Description of the Preferred Embodiment

Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system -related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present application, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as "above," "below," "upper," "lower," or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction.

The present invention represents a safe and arm system that includes one or more switches that employ an operator comprising a "shape memory material," such as a "shape memory alloy" or "polymeric shape memory material," as is discussed in greater detail herein. The present invention further represents a vehicle incorporating the safe and arm system.

Figure 1 depicts a stylized, side elevational view of an exemplary vehicle 101 , in which a portion of a skin 103 of vehicle 101 has been removed to reveal certain components of vehicle 101. In the illustrated embodiment, vehicle 101 is a missile, although the present invention contemplates many various types of vehicle 101. Vehicle 101 comprises a propulsion system 105 for propelling vehicle 101 ; a plurality of control surfaces 107 that, in conjunction with a guidance system 109, operate to control a trajectory of vehicle 101 ; a munition package 111 to be applied to one or more targets; and a safe and arm system 113 that operates munition package 111. It is desirable for safe and arm system 113 to be inoperable prior to deploying vehicle 101 and prior to vehicle 101 traveling a distance away from the vehicle 101 's deployment site so that munition package 111 cannot be inadvertently activated near friendly personnel.

Figure 2 depicts a block diagram of an illustrative embodiment of safe and arm system 113 as operably associated with munition package 111. In the illustrated embodiment, safe and arm system 113 comprises a fuze 201 and a plurality of switches, e.g., switch A, switch B, and switch C. Each of switch A, switch B, and switch C include an operator comprising a shape memory material, as is discussed in greater detail herein. Furthermore, each of switch A, switch B, and switch C are operably associated with fuze 201 , such that fuze 201 does not activate munition package 111 unless each of switch A, switch B, and switch C exhibit a predetermined state, such as "on" or "off." While the embodiment of safe and arm system 113 illustrated in Figure 2 includes three switches, i.e., switch A, switch B, and switch C, the scope of the present invention is not so limited. Rather, safe and arm system 113 may include any number of switches, sensors, or the like and may include switches, sensors, and/or the like that do not include operators comprising a shape memory material, so long as at least one switch, sensor, or the like, includes an operator comprising a shape memory material. It should also be noted that a plurality of shape memory switches, e.g., switch A, switch B, or switch C, can be combined to provide a single input to fuze 201.

Figures 3A and 3B depict an illustrative embodiment of a switch 301 , which may be any switch of safe and arm system 113 (shown in Figure 2), such as switch A, switch B, or switch C (also shown in Figure 2). Figure 3A depicts switch 301 in an open state, while Figure 3B depicts switch 301 in a closed state. In the illustrated embodiment, switch 301 comprises a base 303, an operator 305, and a contact 307. Operator 305 is attached at a first end 309 to base 303, for example, by a fastener 311. Operator 305 is coupled with a first line 313, while contact 307 is coupled with a second line 315. First line 313, operator 305, and second line 315 complete an electrical circuit 317 with fuze 201 , which provides an indication to fuze 201 that a required state has been achieved for activating munition package 111 (shown in Figures 1 and 2). In the illustrated embodiment, operator 305 comprises an electrically- conductive shape memory material. Examples of such shape memory materials include, but are not limited to, a nickel-titanium alloy, a copper-zinc-aluminum alloy, a copper-aluminum-nickel alloy, a copper-zinc-aluminum-nickel alloy, a silver-cadmium alloy, a gold-cadmium alloy, a copper-tin alloy, a copper-zinc alloy, a copper-zinc- silicon alloy, an iron-platinum alloy, a manganese-copper alloy, an iron-manganese- silicon alloy, a platinum alloy, a cobalt-nickel-aluminum alloy, a cobalt-nickel-gallium alloy, a nickel-iron-gallium alloy, and a titanium-palladium alloy.

Generally, an element made from a shape memory material, exhibits different geometries depending upon the temperature of the element. Shape memory alloys are a unique class of metallic alloys that can recover apparent permanent mechanical strains when the alloys are heated above a certain temperature. Shape memory alloys have two stable, solid phases, a high -temperature phase known as austenite and a low-temperature phase known as martensite. Additionally, martensite can be in one of two forms, "twinned" or "detwinned."

If a mechanically-deforming load is applied to the element made from the shape memory alloy while in the twinned martensite phase, i.e., at a non-elevated temperature, the martensite becomes detwinned and the material remains deformed upon releasing the load. Subsequent heating of the element to an elevated temperature results in the reverse phase transformation, i.e., from martensite to austenite, and a recovery of the shape prior to the element being mechanically deformed.

Alternatively, if an element is shaped to a first shape by a mechanically- deforming load at an elevated temperature in the austenitic phase, the element retains its deformed shape when cooled to the twinned-martensitic state. If the element is then detwinned by a mechanically-deforming load to a second shape, the element will return to the first shape when heated into the austenitic phase.

Still referring to Figures 3A and 3B, operator 305 comprises an electrically- conductive, shape memory alloy. In one implementation, operator 305 is provided in a form such as shown in Figure 3B. Operator 305 is then mechanically deformed at a non-elevated temperature, thus detwinning the martensitic structure thereof, to a form such as shown in Figure 3A. When a temperature of operator 305 is raised to a higher temperature, the martensitic structure of operator 305 is transformed to an austenitic structure, resulting in a recovery of the shape of operator 305 to a form such as shown in Figure 3B. In an alternative implementation, operator 305 is mechanically deformed at an elevated temperature while in the austenitic phase to the form such as shown in Figure 3B, then cooled to the twinned-martensitic state. Operator 305 is then mechanically deformed to the detwinned-martensitic state to a form such as shown in Figure 3A. When a temperature of operator 305 is raised to a higher temperature, the martensitic structure of operator 305 is transformed to an austenitic structure, resulting in a recovery of the shape of operator 305 to a form such as shown in Figure 3B. In either embodiment, operator 305 exhibits a form such as shown in Figure 3A at a non-elevated temperature. However, at an elevated temperature, operator 305 exhibits a form such as shown in Figure 3B.

In the embodiment of Figures 3A and 3B, fuze 201 requires electrical circuit 317 to be made, i.e., to be closed to indicate that a required state exists for munition package 111 (shown in Figures 1 and 2) to be activated. Operator 305 is not in electrical contact with contact 307 at a non-elevated temperature, as shown in Figure 3A. Thus electrical circuit 317 with fuze 201 is not made, i.e., is open, thus providing no indication to fuze 201 that munition package 111 can be activated. Operator 305, however, is in electrical contact with contact 307 at a second end 319 thereof at an elevated temperature, as shown in Figure 3B. Thus, the electrical circuit 317 with fuze 201 is made, i.e., is closed, thus providing an indication to fuze 201 that a required state exists for munition package 111 to be activated.

In an alternative embodiment, shown in Figures 4A and 4B, operator 305 comprises an electrically-conductive, shape memory alloy. In one implementation, operator 305 is provided in a form such as shown in Figure 4B. Operator 305 is then mechanically deformed at a non-elevated temperature, thus detwinning the martensitic structure thereof, to a form such as shown in Figure 4A. When a temperature of operator 305 is raised to a higher temperature, the martensitic structure of operator 305 is transformed to an austenitic structure, resulting in a recovery of the shape of operator 305 to a form such as shown in Figure 4B. In an alternative implementation, operator 305 is mechanically deformed at an elevated temperature while in the austenitic phase to the form such as shown in Figure 4B, then cooled to the twinned-martensitic state. Operator 305 is then mechanically deformed to the detwinned-martensitic state to a form such as shown in Figure 4A. When a temperature of operator 305 is raised to a higher temperature, the martensitic structure of operator 305 is transformed to an austenitic structure, resulting in a recovery of the shape of operator 305 to a form such as shown in Figure 4B. In either embodiment, operator 305 exhibits a form such as shown in Figure 4A at a non-elevated temperature. However, at an elevated temperature, operator 305 exhibits a form such as shown in Figure 4B.

In the embodiment of Figures 4A and 4B, fuze 201 requires electrical circuit 317 to not be made, i.e., to be open to indicate that a required state exists for munition package 111 (shown in Figures 1 and 2) to be activated. Operator 305 is in electrical contact with contact 307 at second end 319 thereof at a non-elevated temperature, as shown in Figure 4A. Thus electrical circuit 317 with fuze 201 is made, i.e., is closed, thus providing no indication to fuze 201 that munition package 111 (shown in Figures 1 and 2) can be activated. Operator 305, however, is not in electrical contact with contact 307 at an elevated temperature, as shown in Figure 4B. Thus, the electrical circuit 317 with fuze 201 is not made, i.e., is open, thus providing an indication to fuze 201 that a required state exists for munition package 111 to be activated.

Alternatively, as shown in Figures 5A and 5B, an operator 501 replaces operator 305, shown in Figures 3A, 3B, 4A, and 4B. Other aspects of switch 301 remain as shown in Figures 3A, 3B, 4A, and 4B. Figure 5A is a top, plan view of operator 501 , while Figure 5B is a side, elevational view of operator 501. Operator

501 includes a substrate 503, comprising a non-electrically conductive, shape memory polymer, and an electrically-conductive layer 505 disposed thereon. Electrically-conductive layer 505 is coupled with first line 313. Electrically-conductive layer 505 is in contact with contact 307 when electrical circuit 317 is closed. Electrically-conductive layer 505 may comprise any electrically-conductive material, such as copper or a copper alloy, silver or a silver alloy, gold or a gold alloy, or the like. If substrate 503 is electrically conductive, electrically-conductive layer 505 may be omitted. Similar to an operator, such as operator 305, made from a shape memory alloy, a substrate, such as substrate 503, made from a shape memory polymer, exhibits different geometries depending upon the temperature of the element. Certain shape memory polymers are co-polymers comprising at least two different units, which may be described as defining different segments within the copolymer, each segment contributing differently to the elastic modulus properties and thermal transition temperatures of the material. The term "segment" refers to a block, graft, or sequence of the same or similar monomer or oligomer units that are co-polymerized to form a continuous, crosslinked, interpenetrating network of these segments. The segments may be crystalline or amorphous materials and, therefore, may be generally classified as one or more hard segments or one or more soft segments, wherein the hard segment generally has a higher glass transition temperature than the soft segment.

Each segment contributes to the overall flexural modulus properties of the shape memory polymer and the thermal transitions thereof. The hard segments tend to increase and the soft segments tend to decrease both the flexural modulus properties and the glass transition temperatures associated with the composition of the shape memory material. When multiple segment types are used, multiple glass transition temperatures may be observed, wherein the thermal transition temperatures of the co-polymer may be approximated as weighted averages of the glass transition temperatures of its comprising segments.

The previously defined or permanent shape of substrate 503 made from a shape memory polymer can be set by heating the element to a temperature higher than the highest glass transition temperature for the shape memory polymer, followed by cooling below the highest glass transition temperature. A temporary shape of substrate 503 can be set by heating substrate 503 to a temperature higher than any glass transition temperature of the shape memory polymer but lower than the glass transition temperature of constituent having the highest thermal transition temperature of the shape memory polymer and subjecting substrate 503 to an external stress or load to deform substrate 503, followed by cooling substrate 503 to fix the shape.

Substrate 503 can then be reverted to the permanent shape by heating the material, with the external stress or load removed, above any of the glass transition temperatures of the shape memory polymer but below the highest glass transition temperature of the constituents of the shape memory polymer.

In other words, at the soft segment glass transition temperature, the temporary shape of the shape memory substrate 503 is set followed by cooling of substrate 503, while still under mechanical load, to lock in the temporary shape. The temporary shape of substrate 503 is maintained as long as substrate 503 remains below the soft segment glass transition temperature. The permanent shape is regained when the shape memory polymer element is once again brought to or above the glass transition temperature of the soft segment. Repeating the heating, shaping, and cooling steps can reset the temporary shape. The soft segment transition temperature can be chosen by modifying the structure and composition of the polymer.

Suitable shape memory polymers include, but are not limited to, thermoplastic polymers, thermosetting polymers, interpenetrating networks, semi-interpenetrating networks, mixed networks, or the like. The polymers can be a single polymer or a blend of polymers. The polymers can be linear or branched thermoplastic elastomers with side chains or dendritic structural elements. Examples of shape memory polymers include, but are not limited to polyphosphazenes, polyvinyl alcohols, polyamides, polyester amides, polyamino acids, polyanhydrides, polycarbonates, polyacrylates, polyalkylenes, polyacrylamides, polyalkylene glycols, polyalkylene oxides, polyalkylene terephthalates, polyotho esters, polyvinyl ethers, polyvinyl esters, polyvinyl halides, polyesters, polylactides, polyglycolides, polysiloxanes, polyurethanes, polyethers, polyether amides, polyether esters, polystyrene, polypropylene, polyvinyl phenol, polyvinylpyrrolidone, chlorinated polybutylenes, polyoctadecyl vinyl ether ethylene vinyl acetates, polyethylenes, polyethylene oxide-polyethylene terephthalates, polyethylene/nylon graft copolymers, polycaprolactones-polyamide block copolymers, polycaprolactone dimethacrylate-n-butyl acrylates, polynorbornyl-polyhedral oligomeric silsesquioxanes, polyvinyl chlorides, urethane/butadiene copolymers, polyurethane block copolymers, styrene-butadiene-styrene block copolymers, and the like, and combinations comprising at least one of the foregoing polymer components.

Figures 6A and 6B depict an alternative illustrative embodiment of a shape memory switch 601. Switch 601 comprises a fixed contact 603 and a movable contact 605. A shape memory operator, such as a shape memory wire 607, extends from movable contact 605 and a fixed location, shown generally at 609. It should be noted that shape memory wire 607 may comprise a metallic, shape memory alloy or a polymeric shape memory material. Fixed contact 603 and movable contact 605 are coupled with a first line 611 and a second line 613, respectively. Fixed contact 603, movable contact 605, first line 611 , and second line 613 form an electrical circuit 615 with fuze 201. When a temperature of operator 607 is not elevated, operator 607 exhibits a first length. When a temperature of operator 607 is elevated, operator 607 exhibits a second length, which is shorter than the first length, thus bringing movable contact 605 into contact with fixed contact 603. In this embodiment, no indication is made to fuze 201 that munition package 111 (shown in Figures 1 and 2) can be activated when circuit 615 is open, i.e., movable contact 605 is not in contact with fixed contact 603. However, when circuit 615 is closed, i.e., when movable contact 605 is in contact with fixed contact 603, an indication is made to fuze 201 that a required state exists for munition package 111 to be activated.

Alternatively, as shown in Figures 7A and 7B, shape memory operator 607 exhibits a shorter length when at a non-elevated temperature than when at an elevated temperature. Other aspects of switch 601 operate in the same fashion as described herein concerning Figures 6A and 6B. Thus, operator 607 lengthens to allow movable contact 605 to move away from fixed contact 603 when at an elevated temperature. In this embodiment, no indication is made to fuze 201 that munition package 111 (shown in Figures 1 and 2) can be activated when circuit 615 is closed, i.e., when movable contact 605 is in contact with fixed contact 603. However, when circuit 615 is closed, i.e., when movable contact 605 is in not contact with fixed contact 603, an indication is made to fuze 201 that a required state exists for munition package 111 to be activated.

It should be noted that the present invention contemplates embodiments of switch 301 other than those particularly depicted in Figures 3A, 3B, 4A, and 4B and contemplates embodiments of switch 601 other than those particularly depicted in

Figures 6A, 6B, 7A, and 7B. Moreover, the present invention contemplates embodiments of operator 501 other than that shown in Figures 5A and 5B.

Referring to Figures 1 , 2, 3A, 3B, 4A, 4B, 5A, 5B, 6A, and 6B, in one implementation, switch A corresponds to switch 301 , including either operator 305 or

501 ; or switch 601 disposed proximate an interior surface of skin 103 of vehicle 101 , such as in a nose section of vehicle 101 . Switch B corresponds to switch 301 , including either operator 305 or 501 ; or switch 601 and is electrically coupled in-line with a circuit that activates propulsion system 105 of vehicle 101. Switch C corresponds to switch 301 , including either operator 305 or 501 ; or switch 601 , disposed proximate propulsion system 105 of vehicle 101.

Such an implementation is depicted in Figure 8, wherein switch A is shown as switch 801 , switch B is shown as switch 803, and switch C is shown as switch 805. Switch 801 is operably associated with an interior surface 807 of skin 103 for detecting an elevated temperature of skin 103. Switch 803 is operably associated with, e.g., electrically coupled in-line with, a circuit 809 that activates propulsion system 105. A temperature of switch 803 is elevated to operate switch 803 by resistive heating induced in switch 803 by current passing through circuit 809. Switch 805 is disposed proximate propulsion system 105 for detecting an elevated temperature of propulsion system 105. Switches 801 , 803, and 805 are operably associated with fuze 201 and provide inputs to fuze 201 that correspond to indications that a plurality of required states exists for munition package 111 to be activated. In one embodiment, each of the plurality of required states is independent of the other states. In the illustrated embodiment, three inputs are provided to fuze 201 that correspond to indications that three required states exists for munition package 111 to be activated.

Figure 9 depicts one particular implementation of switch 805 and propulsion system 105. In the illustrated embodiment, propulsion system 105 includes a pole piece 901 disposed at a forward end 811 of propulsion system 105. Switch 805 is operably associated with pole piece 901. In various embodiments, switch 805 may be disposed on pole piece 901 , disposed within or partially within pole piece 901 , or the like.

The present invention provides significant advantages, including: (1 ) providing a safe and arm system that is simpler in construction than conventional safe and arm systems; and (2) providing a safe and arm system that includes components that require little or no electrical power to operate.

The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below. It is apparent that an invention with significant advantages has been described and illustrated. Although the present invention is shown in a limited number of forms, it is not limited to just these forms, but is amenable to various changes and modifications without departing from the spirit thereof.

Claims

1. A shape memory safe and arm system, comprising: a fuze; and a shape memory switch operably associated with the fuze.

2. The shape memory safe and arm system of claim 1 , wherein the shape memory switch comprises: an operator comprising a shape memory material; and a contact; wherein the operator changes to a predetermined shape within a predetermined temperature range and makes electrical contact with the contact.

3. The shape memory safe and arm system of claim 2, wherein the shape memory material is a metallic, shape memory material.

4. The shape memory safe and arm system of claim 2, the operator comprising: a substrate comprising a polymeric shape memory material; and an electrically-conductive layer disposed on the substrate, such that the electrically-conductive layer contacts the contact when the operator changes to the predetermined shape.

5. The shape memory safe and arm system of claim 2, further comprising: a first line coupling the operator and the fuze; and a second line coupling the contact and the fuze.

6. The shape memory safe and arm system of claim 1 , wherein the shape memory switch comprises: a fixed contact; a movable contact; and an operator comprising a shape memory material extending from the movable contact; wherein the operator changes length at an elevated temperature to operate the movable contact.

7. The shape memory safe and arm system of claim 6, further comprising: a first line coupling the fixed contact and the fuze; and a second line coupling the movable contact and the fuze.

8. The shape memory safe and arm system of claim 1 , wherein the shape memory safe and arm system is operably associated with a munition package.

9. The shape memory safe and arm system of claim 1 , wherein the shape memory safe and arm system is operably associated with a vehicle.

10. The shape memory safe and arm system of claim 1 , wherein the shape memory switch is replaced by a plurality of shape memory switches operably associated with the fuze.

11. A vehicle, comprising: a skin; and a shape memory safe and arm system disposed within the skin.

12. The vehicle of claim 11 , wherein the shape memory safe and arm system comprises: a fuze; and a shape memory switch operably associated with the fuze.

13. The vehicle of claim 12, wherein the shape memory switch comprises: an operator comprising a shape memory material; and a contact; wherein the operator changes to a predetermined shape within a predetermined temperature range and makes electrical contact with the contact.

14. The vehicle of claim 13, wherein the shape memory material is a metallic, shape memory material.

15. The vehicle of claim 13, the operator comprising: a substrate comprising a polymeric shape memory material; and an electrically-conductive layer disposed on the substrate, such that the electrically-conductive layer contacts the contact when the operator changes to the predetermined shape.

16. The vehicle of claim 13, further comprising: a first line coupling the operator and the fuze; and a second line coupling the contact and the fuze.

17. The vehicle of claim 11 , wherein the shape memory switch comprises: a fixed contact; a movable contact; and an operator comprising a shape memory material extending from the movable contact; wherein the operator changes length at an elevated temperature to operate the movable contact.

18. The vehicle of claim 16, further comprising: a first line coupling the fixed contact and the fuze; and a second line coupling the movable contact and the fuze.

19. The vehicle of claim 12, wherein the shape memory switch is operably associated with the skin of the vehicle for detecting an elevated temperature of the skin.

20. The vehicle of claim 12, further comprising a propulsion system; and a circuit for activating the propulsion system; wherein the shape memory switch is operably associated with a circuit for activating the propulsion system, such that the shape memory switch is resistively heated by a current passing through the circuit.

21. The vehicle of claim 12, further comprising: a propulsion system; wherein the shape memory switch is operably associated with the propulsion system for detecting an elevated temperature of the propulsion system.

22. The vehicle of claim 21 , wherein propulsion system comprises: a pole piece; and wherein the shape memory switch is operably associated with the pole piece.

23. The vehicle of claim 11 , further comprising: a munition package operably associated with the shape memory safe and arm system.

24. The vehicle of claim 11 , wherein the shape memory safe and arm system is operably associated with the skin of the vehicle.