Clearing a Path for Commercial Space OperationsFebruary 2017
Topics: Aviation Industry, Airspace, Modeling and Simulation
Commercial space launch and reentry operations are becoming increasingly common in the National Airspace System (NAS). This trend is challenging the Federal Aviation Administration to find more efficient methods to integrate these operations into the NAS while ensuring the safety and efficiency of more traditional users—such as airlines, the military, and private aircraft operators. MITRE researchers have created a modeling and simulation capability to help the FAA assess the safety of these more efficient methods.
Traditionally, the FAA has cordoned off large segments of airspace—called Aircraft Hazard Areas (AHAs)—during launch and reentry operations. But this requires other NAS users to reroute around these areas to safely segregate the operations. That often lengthens their flight times and increases their fuel consumption.
To minimize effects on NAS users, the FAA wants to make these AHAs more dynamic and activate them for the shortest possible durations.
Maintaining the Safety of Launch and Reentry Operations
When it comes to space launch and reentry operations, one of the issues the FAA must consider is the possibility that an unexpected event—such as vehicle failure or breakup—could occur. Events like that create falling debris that presents a hazard for other air traffic. These debris fields can be quite large, spanning 100 miles or more for launches and several hundreds of miles for reentry operations.
To account for the possibility of falling debris, the FAA could activate multiple AHAs covering vast amounts of territory during every launch or reentry operation. However, this would be disruptive to other NAS traffic, particularly as commercial space operations continue to grow.
As a result, during a reentry operation, the FAA is considering activating some AHAs only if an unexpected, debris-causing event occurs. If such an event does occur, aircraft would be required to evacuate these areas before the debris from the upper airspace reaches the altitudes where aircraft fly. To ensure the safety of aircraft in such scenarios, the FAA wants to establish efficient procedures for evacuating these "dynamic" AHAs when they're activated.
The FAA could also implement smaller AHAs for launches by using dynamic AHAs, but only if it can better understand the time needed to evacuate them and contributing factors.
Developing a Flexible Modeling and Simulation Capability
To help inform these decisions, MITRE funded an independent research study under the MITRE Innovation Program. The goal of this research was to develop a prototype modeling and simulation capability to predict how long it would take aircraft to evacuate the AHA based on a variety of factors. These include the size and shape of the AHA and traffic density and directional flows within and around the AHA. Other factors are the performance characteristics of the aircraft to be rerouted and the time it takes for air traffic controllers to issue alerts and rerouting instructions.
MITRE also needed a capability to help understand how wide an area the debris would cover. Stanford University researchers had already developed an open source debris model, so MITRE collaborated with them to adapt their model for its research purposes as an alternative to purchasing a full-fledged commercial debris model.
"The great thing about the modeling capability we created is that we can simulate different strategies for evacuating and avoiding these hazard areas, and measure the benefits they produce," says MITRE engineer Zheng Tao, who is leading this research.
"For example, we might input what was actually done during a specific debris event. We would then change the priority of the reroutes or the maneuvers the air traffic controller issued to assess which one resulted in a faster evacuation. That's helping us learn what the most beneficial strategies are for evacuating AHAs so that they can be employed in the future."
Facilitating Future Launch and Reentry Operations
Additionally, the prototype produces several metrics the FAA would be able to use to determine which launch and reentry missions meet a target level of safety. It also helps provide insight into the required surveillance performance, air traffic control response times, and traffic limits to support these safety targets.
MITRE is now working with the FAA to further refine the capability to meet the agency's needs.
"Ultimately, we hope to provide the FAA with a flexible tool to help evaluate the safety and efficiency of past and planned launch and reentry scenarios," Tao says. "That, in turn, will help the FAA support the expansion of space traffic without undue disruption to existing NAS traffic."
—by Marlis McCollum