Safety and arming unit for a munition

A safety and arming device for a munition, the device comprising:

• a separation detector operable to generate a separation signal on detection of separation of the device from a delivery platform;
• a free fall detector operable to generate a free fall detection signal on detection of free fall of the device during a free fall phase following separation;
• a roll manoeuvre detector operable to generate a roll manoeuvre detection signal on detection of a roll manoeuvre of the device, wherein the roll manoeuvre detector is configured to generate the roll manoeuvre detection signal if and only if:
• during the free fall phase, a roll rate of the device is determined to be between a lower threshold and an upper threshold;
• and
• in a first time window after the free fall phase, the roll rate is determined to exceed a first roll-rate threshold that is above the upper threshold of the first time window;
• and
• in a second time window after the first time window, the roll rate is determined to be below a second roll-rate threshold, the second roll-rate threshold being lower than the first roll-rate threshold;
• and
• a munition firing signal generator operable to generate a munition firing signal, wherein the munition firing signal generator is operable to generate the munition firing signal only on presence of all of:
• a separation signal, and
• a free fall detection signal, and
• a roll manoeuvre detection signal.