A rocket firing system and a method of firing a rocket

This invention relates to a rocket firing system and to a method of firing a rocket; the rocket firing system is positioned on a launcher device.

It is already known to fire rockets and other pyrotechnic devices by electrical means, in particular using an inductive linkage. However, a complete system for firing rockets should preferably also enable a pre-firing check upon the presence of the rocket, and upon the effectiveness of the firing circuit of the rocket itself. Effective systems embodying these features have not - previously been known.

Accordingly, the invention provides a rocket firing system comprising a magnetic core and a driver coil mounted co-axial therewith, a sensor coil inductively linked with the core and driver coil, and a detector device connected to the sensor coil to determine the state of any further coil brought into inductive linkage with the core. Preferably, the sensor coil is in two parts lying transversely of and closely adjacent the driver coil.

The firing system may be embodied in a rocket launcher device.

Further, the invention provides a method of firing a rocket having an inductive firing circuit adapted to be magnetically linked by a firing system having a magnetic core, a driver coil and a sensor coil, wherein first the core is brought to link magnetically with the firing circuit, then a low-power signal voltage is applied to the driver coil, the presence and state of the firing circuit being monitored by a signal generated in the sensor coil, and thereafter an operating power voltage is applied to the driver coil so as to induce a firing voltage in the firing circuit.

In order that the invention shall be clearly understood an exemplary embodiment thereof will now be described with reference to the drawings in which:-

• Figure 1 shows the physical disposition of the components of the firing system according to the invention; and
• Figure 2 shows the electrical connections of the firing system.

The firing system which is mounted on the rocket launcher comprises in essence a magnetic core D, which is surrounded by a driver coil A. Mounted in close physical proximity to the coil A is a sensor coil B which is divided into two parts B1 and B₂. The coil

B has its magnetic axis perpendicular to that of coil A and to the core D.

The system is positioned on the launcher such that the core D aligns with a coil C mounted on a rocket positioned in the launcher. The coil C is connected in circuit with a detonator match in the form of a low-voltage, high-current hot wire coil onto which has been deposited a heat sensitive pyrotechnic material. The firing circuit driving coil C has an internal diameter larger than the core D, and when the rocket is in position, the core D enters the coil C and makes an inductive link therewith.

Coil A is connectible to a suitable alternating current supply and which is controlled at two power levels, a low power signal level for testing purposes and a full operating power level for firing. The coil B is connected to a suitable voltage detection circuit. In use, the firing system is set up by moving core D with no rocket present and with the coil A energised at the signal level until the induced voltage in coil B is at a minimum. The core D is then locked in position.

When a rocket is introduced into the launcher, with the signal power voltage applied to the coil A a signal current, well below the safety level of the firing circuit, will flow in coil C. This will result in a major distortion of the magnetic field of coil A and core D. The coil B will detect this change from the normal and the resultant voltage detected by the detection device will indicate the presence of a rocket, and the satisfactory state of the firing circuit on the rocket.

If the rocket is present, but the firing circuit is open-circuited, then no current will flow in the coil C and there will be only minor distortion of the magnetic field when the signal power voltage is applied to coil A.

In the preferred form shown, the coil parts B₁ and B₂ are wound in position, and positioned so that one part will cut more flux than the other when the flux pattern becomes asymetrically distorted by the presence of coil C. This gives a greater sensitivity, and since signal in coil B is a minimum in the balance of a rocket, allows the use of a threshold detector in the circuit to eliminate external effects. The coil parts are preferably connected in a bridge circuit. A single sensor coil, or one co-axial with the core D, could in theory be used but is very much less sensitive.

In another preferred form two sensor coils coaxial with the core D are used, preferably in a bridge circuit.

Such a firing system is adapted well to being applied to a series of launchers, and testing and firing can be carried out remotely, either sequentially or in unison.