Flight termination system

In the field of rocketry, range safety may be assured by a system which is intended to protect people and assets on both the rocket range and downrange in cases when a launch vehicle might endanger them. For a rocket deemed to be off course, range safety may be implemented by something as simple as commanding the rocket to shut-down the propulsion system or by something as sophisticated as an independent Flight Termination System (FTS) that has redundant transceivers in the launch vehicle that can receive a command to self-destruct then set off charges in the launch vehicle to combust the rocket propellants at altitude. Not all national space programs utilize flight termination systems on launch vehicles.

In the United States, range safety is usually the responsibility of a Range Safety Officer (RSO) affiliated with either the civilian space program led by NASA or the military space program led by the Department of Defense, through its subordinate unit the Air Force Space Command. At NASA, the range safety goal is for the general public to be as safe during range operations as they are in their normal day-to-day activities.

RSOs are also present in the hobby of model rocketry. In this case, they are usually responsible for ensuring a rocket is built correctly, using a safe engine/recovery device, and launched correctly.

Some launch systems use flight termination for range safety. In these systems the RSO can remotely command the vehicle to self-destruct to prevent the vehicle from traveling outside prescribed safety zone. This allows as-yet-unconsumed propellants to combust at altitude, rather than upon the vehicle reaching the ground.

Space vehicles for sub-orbital and orbital flights from the Eastern and Western Test Ranges were destroyed if they endangered populated areas by crossing pre-determined destruct lines encompassing the safe flight launch corridor. To assist the RSO in making a flight termination decision, there are many indicators showing the condition of the space vehicle in flight. These included booster chamber pressures, vertical plane charts (later supplanted by computer-generated destruct lines), and height and speed indicators. Supporting the RSO for this information were a supporting team of RSOs reporting from profile and horizontal parallel wires used at lift-off (before radar could capture the vehicle) and telemetry indicators. After initial lift-off, flight information is captured with X and C-band radars, and S-Band telemetry receivers from vehicle-borne transmitters. At the Eastern Test Range, S and C-Band antennas were located in the Bahamas and as far as the island of Antigua, after which the space vehicle finished its propulsion stages or is in orbit. Two switches were used, ARM and DESTRUCT. The ARM switch shut down propulsion for liquid propelled vehicles, and the DESTRUCT ignited the primacord surrounding the fuel tanks. In the case of manned flight, the vehicle would be allowed to fly to apogee before the DESTRUCT was transmitted. This would allow the astronauts the maximum amount of time for their self-ejection.

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