OVERVIEW OF AUTONOMOUS FLIGHT TERMINATION SYSTEMS

AFTS: past, current and future

Why AFTS?

The current range ground-based infrastructure responsible for public safety during launches is extremely costly to operate and maintain. The Autonomous Flight Termination System (AFTS) developed by NASA is an independent, self-contained subsystem mounted onboard a launch vehicle.

The AFTS (also known as Autonomous Flight Safety Systems or AFSS by the military) eliminates the need for a ground-based infrastructure by moving the flight termination function from the ground to the launch vehicle and is considered safer than having an individual in the loop making the decision to terminate a flight.

A Brief History

Work on the Autonomous Flight Termination System (AFTS) began over 20 years ago by Dr. James Simpson at NASA. He wrote papers on the subject which ultimately created the AFTS development program at the agency. Dr. Simpson, who passed away, was memorialized on the first AFTU that went into space (May 2017).

How does AFTS Work?

It starts with a core software package developed by NASA, the U.S. Air Force and the Defense Advanced Research Projects Agency. To that, a “wrapper” — software customized for its own rockets — is added. This software runs on an AFTU or Autonomous Flight Termination Unit such as those produced by Sagrad.

During flight, GPS and other sensors on the launch vehicle continuously record the vehicle's position and trajectory. If the vehicle crosses vehicle boundary lines pre-programmed into the AFTU, which would indicate repeated violations of flight rules, the AFTU provides signals to the vehicle in order for it to take flight termination actions (thrust termination, pyrotechnic detonations, etc.), just as if the signals were sent from the ground.

The System Design Overview

The system uses a ruggedized chassis, a NASA-designed custom board, NASA-developed wrapper interface software, and the Core Autonomous Safety Software (CASS) running on a COTS processor. The range requires that the AFTS system consist of a redundant chassis with redundant sensor inputs. The sensor inputs can be GPS, INS, IMU, accelerometers, or any combination thereof. All sensor inputs can be available to both chassis.

Each chassis is capable of initiating a flight termination. If both chassis are healthy, and either recommends a flight termination, the flight will be terminated. If one chassis is unhealthy, its failsafe must initiate a termination unless it can verify the other chassis is healthy. If both chassis are unhealthy, both failsafes will initiate a termination.

The First Launch with AFTS

After years of development, testing and ‘shadow’ launches, the first launch using live AFTS took place at Cape Canaveral in a SpaceX Falcon 9 on February 19, 2017. This was an historic “game changer” according to Brig. Gen. Wayne Monteith of the Air Force’s 45th Space Wing. The launch demonstrated that the new technology will improve safety, lower costs and enable more launches from Florida’s Eastern Range.

“It was tested extensively, and is actually safer than having an individual in the loop,” Monteith said in a recent interview. “It fundamentally changes the way we are doing business.”

The second launch using a ‘live’ AFTS was also a SpaceX flight which launched on the West Coast on June 25, 2017 at Vandenberg Air Force Base, California. Several other flights have taken place and more are scheduled with the Sagrad AFTU.

The AFTS Mandate from Congress

On July 10th, 2017, the Senate Committee on Armed Services created a directive to the Secretary of the Air Force to provide a report to various government agencies on a strategy to transition to Automated Flight Safety and Termination Systems at the Eastern and Western ranges by 2022.

The Air Force responded in April 2018 confirming the branch is driving toward a transition of all Eastern and Western Range users to Automated Flight Safety Systems. They are working on this now, saying “AFSPC is working with the DoD test programs on an intense 120-day effort to define and cost alternative approaches that will allow those programs to transition sooner than 2023.”

The Future of AFTS

SpaceX was the first to fly an AFTS system operationally, and there are several other programs currently working with the Air Force’s 30th Space Wing, the 45th Space Wing, the FAA and DARPA to design, test and deploy AFTUs based on CASS for use on their launch vehicles. Sagrad has been involved with the development and commercialization of these programs for four years, and we lead the industry in the development of the next generation AFTUs.

It’s clear from the Congressional mandate that autonomous flight termination systems will continue to grow as more are fielded and knowledge of the system capabilities and flexibility grows. Customers and requirements are key to this progression.

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SAGRAD COMPANY OVERVIEW

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Sagrad is a privately-held corporation, incorporated in August of 2004. The business is organized into four business units that provide products and engineering services to companies worldwide.

  • Wi-Fi
  • Aerospace
  • OEM Products
  • Electronics Manufacturing

Sagrad provides full lifecycle electronics development, from requirements through design, development, in-house manufacturing, test and packaging.