Last month, NASA released its concept of operations (ConOps) for the future of urban air mobility (UAM). Developed in collaboration with Deloitte, it describes a future where electric air taxi operations are commonplace but not yet ubiquitous, with hundreds of simultaneous flights relying on collaborative and responsible automated systems — “UAM Maturity Level (UML) 4,” in NASA’s framework.
Much more in-depth than the UAM ConOps released last year by the Federal Aviation Administration (FAA), NASA’s ConOps spans 96 densely written pages, including appendices. For those of you who haven’t had a chance to read it, we’ve rounded up some of the key takeaways.
1. It’s a ‘Vision ConOps’
The ConOps is a description of what urban air mobility might look like at some point in the future — not a roadmap for getting there. Consequently, it assumes that manifold problems standing in the way of widespread air taxi operations have already been solved.
“As a ‘Vision ConOps,’ this ConOps presents a generalized vision of the future with UAM and is designed to only imply high-level requirements on the UAM system; as such, it is not designed to suggest or prescribe any specific course of action to reach UML-4,” the document explains. “In describing the anticipated system state at UML-4, it occasionally provides specific details or touches on possible methods to achieve UML-4 as illustrative examples or for clarity.”
That’s not to say that the ConOps discounts the barriers to successful urban air mobility. It presents an extensive list of challenges associated with each of five “pillars,” including airspace design, airspace management, aircraft development, aircraft operations, and community integration. However, “as this ConOps is written from the perspective of someone in the future at UML-4, [it] describes a system that has successfully overcome these barriers for each of the five pillars” — from surmounting technical challenges to convincing the public that urban air mobility is safe and desirable.
2. It envisions flexible UAM airspace
The UAM ConOps Version 1.0 released by the FAA last year relies on the concept of “UAM corridors,” which it defines as “performance-based airspace of defined dimensions in which aircraft abide by specific rules, procedures, and performance requirements.” NASA’s ConOps also envisions UAM airspace with specific rules, procedures, and performance requirements, but its concept is more sophisticated and flexible — as befits a more advanced stage of UAM development.
In NASA’s ConOps, UAM aircraft operate primarily within the UAM operating environment (UOE). The maximum dimensions of this airspace are static and charted, but the available UOE at any point in time is subject to change: “For example, if the flow pattern at a nearby major airport changes, the available UOE may change to avoid potential traffic conflicts among UAM aircraft and traditional commercial airlines.”
Changes in the available UOE might occur a few times per day and are reported by providers of services to UAM (or PSUs — more on them below). In the FAA’s ConOps, conventional, human-operated air traffic control (ATC) is responsible for declaring whether a UAM corridor is open or closed. In the more complex operating environment of NASA’s UML-4, the area of the UOE that is available at any given time is based on traffic demand and criteria established by the FAA, but ATC has the capability to close the UOE as necessary.
Each metropolitan area’s UOE is tailored to meet its specific needs. The floor of the UOE will extend to the ground around “UAM aerodromes,” but will otherwise leave very low-level airspace available for small drones flying under unmanned aircraft system traffic management (UTM). The ConOps assumes that most UAM aircraft will cruise at altitudes between 1,500 and 4,000 feet above ground level.
NASA envisions that within the UOE are high-density routes that require more advanced capabilities for managing aircraft than other areas of the UOE. These areas of high traffic flow may only be open during morning and evening rush hours, or before and after sporting events, and will require more focused and deliberate community engagement to address noise and other community concerns.
3. Providers of services for UAM play a key role
NASA’s ConOps carries over another concept from the FAA’s version: PSUs. Qualified PSUs may be either public (e.g. provided by a local government) or private (a third-party service provider). They provide highly automated flight planning support and air traffic management services within the UOE, leaving ATC free to focus on its traditional responsibilities.
“ATC has access to all available real-time information about UAM operations, but does not generally monitor UAM operations; rather, ATC is alerted only in the case of an emergency or when UAM operations depart from their desired parameters,” the ConOps explains. This approach broadly tracks with the FAA’s initial UAM ConOps, which also provides for notifications to flow from UAM operations to the agency and ATC but explicitly states that ATC will not provide tactical separation services within UAM corridors.
Any aircraft that operates in the UOE, according to NASA’s model, must participate in the PSU Network, which is a digitally connected network of all PSUs in an area and provides a secure information exchange between users of the UOE. Prior to operating in the UOE, an aircraft must submit an operations plan to an appropriate PSU. The PSU transmits information from the fleet operator to the FAA, which authorizes the operations through an automated system.
In some cases, the UOE may extend into actively controlled airspace — as for UAM routes between major airports and urban centers. UAM aircraft following such routes will continue to rely on PSUs and will not be in communication with ATC under normal operations.
By UML-4, NASA also expects UAM vehicles to be exchanging information with each other. This “vehicle to vehicle” (V2V) communication includes position information and data needed to aid in collision avoidance, separation, and deconflction.
4. It assumes simplified vehicle operations
NASA’s ConOps doesn’t actually use the term “simplified vehicle operations” (SVO) except in a citation, but SVO is widely used to describe flight operations that rely on advanced autonomy for some functions traditionally performed by human pilots. Consistent with existing regulations, the ConOps retains the concept of a “pilot in command” (PIC) who holds final authority and responsibility for the safety of the flight, but acknowledges that this could be a remote PIC not onboard the aircraft, or a crewmember with fewer roles than the pilot of a conventional aircraft.
NASA doesn’t expect to see fully autonomous aircraft at UML-4. However, it does anticipate that “methods have been developed to test and certify semiautonomous operation, and historical regulations have been adapted to certify UAM aircraft operations such that automated systems are recognized as ‘responsible’ for the performance of designated, safety-critical functions that have traditionally been the responsibility of human agents (i.e., pilots).”
The ConOps assumes that different organizations have pursued different paths to the long-term goal of full autonomy, resulting in various “aircraft crew archetypes” at UML-4. These include an onboard PIC with no additional crew; a remote PIC responsible for a single aircraft with no additional crew; and a remote PIC responsible for multiple aircraft with a second in command onboard each aircraft. Depending on the archetype, responsibility for various functions is divided between aircraft automation and human crewmembers in different ways.
5. It assumes other technological and regulatory advancements, too
Going back to all of those challenges that have somehow been overcome by the time we get to UML-4, it’s worth highlighting some more of the advancements that are deemed fundamental to NASA’s vision. For example, the ConOps states, “UAM at UML-4 is enabled by advanced CNSI [communications, navigation, surveillance, and information] technologies and services” that enable “seamless, secure, and resilient information exchange” between users. These systems must have robust cybersecurity standards, and sufficient electromagnetic interference protections both on and off the aircraft.
Aircraft designers have their work cut out for them in more ways than one. By UML-4, UAM vehicles are assumed to be able to operate from challenging urban aerodromes in low visibility and high wind conditions, and to follow precise 3D and 4D trajectories with minimal clearance from obstacles. Sensors and real-time PSU Network data exchange must enable them to operate with much less separation from each other than do conventional aircraft today.
Meanwhile, weather data collection, analysis, prediction, and reporting must be tailored to meet the needs of UAM operators, including through the installation of specialized infrastructure. UAM aerodromes must meet the demands and constraints of their local communities, and have sufficient access to local utilities including electrical grids and internet connectivity.
And that’s just on the technology side. The ConOps also assumes that aircraft certification regulations have been adapted to encompass UAM aircraft, that local communities have accommodated UAM operations in their zoning and other regulations, and that legal liability statutes have been refined to address unique aspects of UAM, including the use of semiautonomous systems.
That’s a daunting to-do list, although many people in the UAM industry are actively working towards all of these goals. With its Vision ConOps, NASA aims to engage members of that community with “a common framework to inform the continued development and integration of UAM as part of the broader transportation system.”