Coiled Bi-Metal Exploding Bridgewire

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Although current EBW devices represent the ultimate in safety in Aerospace applications, the use of high temperature insensitive explosives would represent an improvement especially in harsher thermal environments. EBW initiation is used for rocket engines, gas generators. pyro separation devices, activation of emergency systems, and other critical Aerospace and Military Systems.

The intent of the current invention is to enable the initiation of insensitive explosives using current electrical methods. This will provide even greater safety.

To do so the combination of multiple plasma jets from a single bridge wire as well as the potential for focusing these jets and the peripheral possibility of “catalytic” support of initiation offer substantial reasons for exploring this technique.

The simplest version of this method is the use of a bi-metal combination of a lower MP main wire around which is tightly coiled wire of a higher MP with a pitch of some tens of microns.

On application of the high voltage dump from a suitable capacitor, the low MP wire of high conductivity immediately goes into a plasma state emitting jets through the coiled higher MP wire which then also becomes plasma.

The jets being circumferential may be further focused by slightly embedding the bridge wire combination in a slight groove on the header surface which is generally ceramic or glass.

The initiation energy even of currently employed explosive may be lowered using this technique. This means smaller capacitors and/or lower voltages.

A typical combination would be a copper core with a platinum overwrap. The usual dimensions of this combination would be in the ballpark of a 25 to 50 micron copper wire with an overwrap of 25 to 50 micron platinum. The coiled portion may be welded or soldered to the terminals but it may not be necessary as the plasma from the vaporization of the copper internal wire will be conductive and supply the necessary energy to the surrounding coil.


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  • Name:
    William Colburn
  • Type of entry:
  • Patent status: