Traditional FTS vs. Autonomous FTS

As a disclaimer here, we may use a few terms interchangeably:

• Flight safety system
• Flight termination system
• Thrust termination system

There are some nuances to the specific meanings of these we may touch on in future articles.

Traditional FTS

Launch vehicles capable of leaving a range and thereby endangering a protected area are required to have the capability to terminate the flight. This system is used if the vehicle deviates from its intended flight path, violating a limit line which has been established as part of a hazard analysis.

The traditional way of doing this relies heavily on both onboard components and significant ground support infrastructure. On the vehicle, a radar, a transponder and its associated antennas and couplers are tracked b ground radar sites. That information is relayed through ground communication networks, back to a flight control console where a safety officer is analyzing the real time data to flight trajectory plan and comparing the telemetry. If there's a violation of a limit line, the officer would issue a terminate command back to the vehicle using ground-based communication networks and transmitters. On the vehicle, this would be received by a flight termination receiver which has its associated antennas and couplers.

Autonomous FTS

On an autonomous flight safety system, we've moved the tracking and decision making capability to the vehicle thereby eliminating the vast majority of the ground support infrastructure required or, at the very least, reducing those assets to non-safety critical.

The tracking and decision-making capability have been moved to the vehicle. This is done by the introduction of a new device, an Autonomous Flight Termination Unit (AFTU). This device tracks the flight of the vehicle either using internal or optional external sensors, or a combination of the two. It's comparing the flight to a set of preloaded mission flight rules known as the mission data load. If one of those rules is violated, the AFTU will issue the terminate command.

How?

• Tracking and light termination decision moved to Autonomous Flight Termination Unit (AFTU) on the vehicle
• Tracking data from internal / external GPS and INS sensors
• Mission Data Load (MDL) - rule set built in pre-flight
• If a rule is violated the flight is terminated

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