Automated flight safety improving space access
CAPE CANAVERAL, Fla. — After supporting over 3,500 launches in the past 70 years, Cape Canaveral Air Force Station (CCAFS) faces a busy 2017. With a scheduled flight manifest of some 30 launches, the Eastern Range is changing the way it handles flight safety to satisfy a wider array of customers.
On-board self-destruct in operation
Every rocket launched has a feature on board that can command the vehicle to self-destruct: a flight termination system. Until 2017, however, the actual command to destroy a rocket came manually from the Range Safety Officer on the ground.
Now, however, a new device, the Autonomous Flight Safety System or AFSS, puts the control in the hands of a computer on board the rocket.
AFSS was first demonstrated as a primary system on an operational flight during SpaceX’s Feb. 19, 2017, CRS-10 launch from Kennedy Space Center’s Launch Complex 39A.
Gwynne Shotwell, SpaceX’s President and Chief Operating Officer, explained that the company has been using autonomous flight safety systems for a while in “shadow mode” with the manual system being the primary.
The AFSS is a self-contained, independent system mounted to a launch vehicle. The system’s computer determines if the launch vehicle poses an unacceptable hazard to people or property by using pre-established, programmed mission rules developed by range safety flight analysts. If the computer determines that the rocket is a danger to public safety, it activates a series of controlled explosions to immediately stop the vehicle’s forward progress.
Up to now, these public safety decisions were made by individual human controllers on the ground. Kennedy Space Center Director and former astronaut Bob Cabana said that the automated system is the wave of the future and it is where the range is going.
Cabana’s reasoning for this is that, in some cases, human beings are more cautious than the computers and might initiate the flight safety system unnecessarily.
“If done right, an autonomous system is safer than having a human in the loop,” Cabana said.
The AFSS is configurable and uses software-based rules that rely on redundant flight processors using data from GPS and onboard sensors. The system also reduces the amount of customized hardware CCAFS must have on the ground to activate flight termination systems. This allows the range to improve its turnaround times using tougher safety standards and fewer people on consoles while still reducing launch costs.
The end result is the automated system can ensure the Eastern Range can increase the number of customers seeking space access.
A busy future ahead
CCAFS’ customer base has been steadily increasing, from NASA and the Air Force to United Launch Alliance (ULA) and SpaceX.
In the next few years, CCAFS will also support launches and landings by Blue Origin, crewed launches to the International Space Station by SpaceX, Boeing, and Sierra Nevada Corporation, as well as small launcher operations from KSC’s Launch Complex 39C.
With more stakeholders requiring access to space, the Air Force’s Eastern Range (the ocean east of CCAFS) and the Western Range (the area south of Vandenberg Air Force Base in California) have had to develop innovative solutions to launch rockets without compromising public safety. They are also coping with aging infrastructure and constrained resources in the face of increased flight rates.
In a recent media release, General Jay Raymond, Air Force Space Command commander, said that the Air Force Space Command partners with industry in order to advance its space capabilities.
“AFSS allows us to increase the pace of launch, reduce costly infrastructure and more rapidly build a resilient space enterprise,” Raymond said. “These benefits will be felt globally.”
While reducing the number of controllers on the ground, AFSS also provides greater flight termination control further downrange than would be possible by activating the system remotely.
Because the controls are aboard the rocket, a flight termination command can also be issued more quickly. The onboard capability also means AFSS can operate over the horizon, so flight termination is no longer limited by ground equipment sending signals by line of sight.
Additionally, AFSS can support multiple objects in simultaneous flight, which is crucial for companies like SpaceX, which plans to land multiple first stage cores for its Falcon Heavy vehicle at nearly the same time.
“Our role to ensure public safety during launches using this system is unchanged,” said 45th Space Wing Chief Engineer Howard Schindzielorz. “Our Flight Termination System requirements still apply for design, test, operational performance and reliability. We still develop the mission rules to provide public safety, but the system works with mission rule data files loaded into the onboard AFSS units. This essentially shifts the workload to the front-end of the launch process.”
AFSS increases launch availability by reducing the amount of hardware needed on the ground. This includes eliminating the cost of hardware needed for non-AFSS launches, such as Uninterruptible Power Supplies, ground-system software, Independent Validation & Verification, and testing equipment.
The 45th Space Wing is pushing its systems to support a launch manifest of up to 48 launches per year – early one per week – by 2020.
Bart Leahy is a freelance technical writer living in Orlando, Florida. Leahy's diverse career has included work for The Walt Disney Company, NASA, the Department of Defense, Nissan, a number of commercial space companies, small businesses, nonprofits, as well as the Science Cheerleaders.
My support to Range Safety dates back to the Apollo era. Based on lessons learned, I find it hard to accept that an autonomous self destruct system will replace radar, optics, and telemetry data reduced in near real time to provide the Range Safety Officer with a comprehensive situational overview.
Consider a failure – Challenger comes to mind – where the optics captured the root cause of the failure when debris analysis may never have revealed the cause.
Speaking of debris, although impact predictions are quite accurate, they are no substitute for radar skin or beacon tracking debris from a failed vehicle. This data is irreplaceable for the recovery of critical payloads which may be classified in nature.
The use of GPS is a sound concept, but the reduction of GPS is not instantaneous. Even 40+ years ago, data critical to range safety was no more than 300 milliseconds old. GPS also relies on antennae which must be oriented toward the GPS constellation – a challenge in a near vertical vehicle. And GPS can be spoofed, introducing a new threat.
Redundant systems certainly do reduce the likelihood of failure. Bearing in mind that most critical vehicle systems are redundant, if they truly eliminated the possibility of a failure, why would a destruct system even be necessary?
One may reasonably summarize that range tracking systems are necessary to identify causes of failure, track reentering debris, and to provide a redundant, man-in-the-loop safety system.
There is, however, no absolute requirement that these range systems be land (or sea) based. A space-based range system may very well be the cost effective solution needed.
Interesting to see my old job replaced by an onboard computer but that’s progress. I was a Range Safety Officer at the AF Eastern Test Range from January 1972 to May 1973. I was part of the Range Safety team for the last 2 Apollo launches and the first Skylab launches.