Automated Aerial Refueling
Persistent Surveillance Requires
Platforms Up to the Task.
One Way to Extend the Reach of UAVs
is to Refuel Them While Airborne.
Platforms Up to the Task.
One Way to Extend the Reach of UAVs
is to Refuel Them While Airborne.
The United States Air Force desires to further develop an automated aerial refueling (AAR) capability within the Air Force Research Laboratory (AFRL) as a risk reduction measure to enable future unmanned air vehicle (UAV) weapon system development programs. This program will build upon previous AAR Phase I technical efforts that developed and demonstrated a proof-of-concept AAR capability employing a single-channel relative navigation (RELNAV) system based on precision GPS (PGPS). The AAR Phase I system was developed, integrated into tanker and (piloted) surrogate UAV receiver aircraft, and demonstrated by simulation and by flight test to the pre-contact, contact and observation aerial refueling positions. During formal simulation activities conducted at AFRL Aerospace Vehicles Technology Assessment and Simulation (AVTAS) facility, entire refueling operations beginning with rendezvous through post refueling were demonstrated. During flight test, automated maneuvering between positions and key portions of rendezvous were also demonstrated.
Future unmanned aircraft may utilize both boom and receptacle (USAF-style) and probe and drogue (U.S. Navy and NATOstyle) refueling. As such, AFRL has issued broad agency announcement that seeks to develop and demonstrate AAR capabilities for aerial refueling using the boom and receptacle method, while ensuring as much commonality between the USN and USAF AAR architectures as possible. Although desired in the future, unique USN AAR configurations will not be demonstrated under this BAA.
The program will be executed in two spirals. The first spiral will be preceded by a task to formulate AAR system-level requirements. After the requirements have been derived, in Spiral 1 of the program, the AAR Phase II Integrator will take a government- developed single-channel system and design, develop, integrate, fabricate and qualify a multi-channel PGPS-based relative navigation system, an automated flight control system (FCS), and AARspecific command and control (C2) system components to accomplish boom and receptacle AAR. The design, architecture, development, and testing under this effort will be on hypothetical UAV “equivalent” models designated EQ1, EQ2 Small and EQ2 Large.
In Spiral 2, the AAR Phase II Integrator will conduct trade studies and evaluations of (non-GPS) sensor-based relative navigation measurements to augment the Spiral 1 system.
Outside the AAR Phase II Integrator contract, AFRL is further developing a single- channel PGPS RELNAV system, which will be provided to the integrator as government furnished equipment (GFE). The GFE system employs a network communications (signal-in-space) architecture. The government intends to qualify the GFE system with a single-channel avionics configuration prior to the AAR Phase II Integrator developing the single-channel system into a multi-channel, redundant system.
Using the GFE system, an integrator will integrate multiple channels and further develop the tanker and receiver aircraft components of the Spiral 1 RELNAV system. The resulting receiver aircraft’s multi-channel integrated RELNAV system will provide performance and reliability appropriate for an autonomous system. The AAR Phase II integrator will integrate the multi-channel receiver RELNAV system with a redundant automated FCS. Using outputs from the RELNAV system, the FCS will provide outer loop control of the receiver aircraft during air refueling operations, including stationkeeping, re-positioning around the tanker, rendezvous, post-refueling separation and contingencies. The AAR-specific C2 capability will enable a remotely-located test engineer to monitor and control the AAR system during automated refueling operations in hardware-in-the-loop (HITL) simulation and flight test.
The single-channel PGPS RELNAV system will be evaluated under separate government planned and conducted ground and flight test efforts to evaluate and document single-channel performance against the specifications before being provided as GFE. The AAR Phase II integrator will participate in planning and observing these tests and will receive the test data as GFI. In FY11, the AAR Phase II integrator will support and receive data from a governmentconducted flight test, for an early evaluation of the Spiral 1 integrated multi-channel RELNAV system performance. The AAR Phase II Integrator will participate in the test planning, provide a Spiral 1 RELNAV multi-channel system as the test item, support test operations and receive the test data as GFI for analysis. After receiving the GFE system, the AAR Phase II Integrator will develop and fabricate at least one receiver aircraft AAR system (multi-channel RELNAV system, FCS, and AAR-specific C2) to enable HITL simulation and other ground test efforts.
The manned surrogate is the second government planned and conducted flight test program. Through a planned future acquisition the government will select a receptacle-equipped military aircraft (the manned surrogate aircraft) to act as a surrogate UAV receiver. A tailored version of the AAR Phase II Integrator’s Spiral 1 system will be installed and flight tests will be conducted in FY 11 and 12. Irrespective of the manned surrogate provider, the AAR Phase II Integrator will retain AAR system performance responsibility throughout the flight test program.
Under Spiral 2 of the contract resulting from this solicitation, the AAR Phase II integrator will study alternatives for a “sensor-augmented” AAR RELNAV system that would integrate additional state measurements from sensors or other sources to enable AAR under normal operating conditions and GPS-degraded or GPSdenied conditions.
OBJECTIVES AND PRODUCTS
The desired end state of the AAR Phase II Program is such that the USAF could enter Post-Milestone B system development and demonstration (SDD) with a future aircraft acquisition program and implement the Spiral 1 AAR system with low risk. To enable that end state, the desired products of the AAR Phase II Integrator effort include the following:
A prototype integrated multi-channel PGPS-based RELNAV system demonstrated in an operational environment (Technology Readiness Level (TRL) 7). Flight testing of the system will occur under other contracts.
A redundant FCS design, embodying robust outer loop and trajectory control, tested to demonstrate compatibility with a range of aircraft inner-loop flight control models, and documented with tailoring guidance /lessons learned, for application to future aircraft acquisitions.
Supporting documentation for a PGPSbased (Spiral 1) AAR system, to include concept of operation (CONOPS system, subsystem and interface requirements, a technology transition process, including airworthiness certification and a product improvement strategy.
A HITL/flight test remote monitor and control system, referred to as the AARspecific C2 system, capable of remotely monitoring and interacting with the AAR system in HITL and flight test on the manned surrogate. These interactions will be derived and representative of the CONOPS and should be documented through specifications, design guidelines and lessons learned.
A recommended technical approach, tailored CONOPS, Spiral 2 architecture, and documented system requirements for a sensor-augmented (Spiral 2) RELNAV system. The estimate cost of this BAA currently stands at about $49 million. The duration of this effort is 52 months. This includes 48 months of technical effort and four months for reporting.
The integrator selected under this BAA will develop program management tools required to support program control, documentation, and reporting.
The AAR Phase II Integrator will be responsible for establishing associate contractor agreements and teaming arrangements with the broader AAR contractor team. The integrator will also be responsible for ensuring that all items under development will meet the integrator’s technical requirements as part of the overall AAR system, to include tanker and receiver.
It is important to note that the Phase II Integrator program focuses solely on the EQ and EQ2 models for the design and implementation. Any tailoring of the Spiral 1 system or specific development for the surrogate aircraft will be accomplished under separate efforts. The Phase II Integrator should be concerned about the surrogate test objectives, required data collection, and data analysis, not the vehicle systems or modification. ♦