A Miniaturized Laser Firing Unit with Tunable Power Output
- Paper ID
92280
- author
- company
Vikram Sarabhai Space Centre (VSSC); Vikram Sarabhai Space Centre, ISRO, Thiruvananthapuram
- country
India
- year
2025
- abstract
Traditionally, pyrotechnics systems and components are used for stage ignition, stage separation, and satellite separation in launch vehicles. Thermal or mechanically driven initiators, as well as electric initiators are commonly employed for these purposes. The choice of technology is typically based on application, cost, and environmental factors such as shock, electrical interferences, and thermal conditions. In current launch vehicles, the pyrotechnic chain is ignited by applying an electrical current through a bridge wire in the pyro initiating device (squib). However, operating squibs using electric current requires higher current and battery capacity. This calls for batteries with greater size, weight, and cost. To address these challenges, this paper proposes the design of a Laser Firing Unit (LFU) for operating laser initiated squibs with five safety breaks in the Pyro chain. In an opto-pyrotechnic system, Laser Initiated Devices (LID) are directly operated by intense laser pulses transmitted via optical fibers from the LFU. The proposed system has several advantages over conventional designs, including, reduced total weight and size, low current requirements, and decreased battery capacity. The optical pyrotechnic system of launch vehicles consists of three subsystems to execute the required command: Laser Firing Unit (LFU), Optical Harness (OH), and, Laser Initiated Device (LID). The LFU consists of a battery, five safety breaks, a laser diode, and a constant current circuit to regulate the current through the laser diode. This design includes a provision for tunable laser power output based on mission requirements. System miniaturization is achieved through the use of MOSFET-based circuits for the safety breaks, with redundancy. Detailed Failure Mode Effects and Criticality Analysis (FMECA) and Sneak Path Analysis have been completed for the design. The developed LFU system was integrated with the LID and tested under standard room conditions and thermo-vacuum conditions. The system has also been qualified for the shock, vibration and thermal levels specified for launch vehicle and satellite applications. The Bruceton test for the LID was conducted with the LFU system in integrated condition and the All Fire Power (AFP), No Fire Power (NFP) and Recommended Fire Power (RFP) levels were characterized for the LID. The results demonstrate that the system performance is normal during all the environmental tests specified for operation in space environments.