Lift and Nozzle Change Effects on Tail Shock (LaNCETS), 2008 - 2009
The LaNCETS project's primary task was to investigate the supersonic tail shock and the effects of changing the lift distribution and nozzle area ratio. The purpose of this project was to first validate computation fluid dynamics (CFD) models and second to explore ways to reduce the supersonic tail shock. Flight-testing began in spring 2008.
Benefits: LaNCETS allowed NASA to validate supersonic computational fluid dynamic (CFD) models with real-time data; in particular, the changes in the shocks caused by varying the lift and nozzle ratios. This will help create better prediction tools for supersonic flight, and those predictions can help in the design of a quieter supersonic vehicle that can travel over land. This will allow people to travel faster anywhere in the world and make everyone more mobile.
Space-Based Range Demonstration and Certification/Exploration Communications and Navigation Systems (SBRDC/ECANS), 2006 - 2007
Dryden conducted ground and airborne tests of improved space-based communications and tracking technologies during the Space-Based Range Demonstration and Certification project. The project developed and demonstrated state-of-the-art space-based communication links for tracking data, telemetry, and flight termination systems. It will help eliminate the need for downrange ground-based infrastructure now used for aircraft and space launch vehicles. Results of the flight tests will also aid certification of the new systems for operational use.
NASA Dryden's highly modified NF-15B research aircraft was the testbed for this project. NASA flew 13 flights over a 4-month period from November 2006 through February 2007. The first half-dozen of these flights checked out new Ku-band phased array antennas and associated transceivers for the Range Safety and Range User Systems, while the remaining flights validated the Range Safety System. Both systems were linked between the aircraft, the NASA Tracking and Data Relay Satellite System (TDRSS), and test ranges at Dryden and White Sands in New Mexico, with data transmitted to Goddard Space Flight Center, MD and Kennedy Space Center, FL.
The range safety antennas installed on the aircraft also underwent antenna radiation pattern testing in the Benefield Anechoic Facility at Edwards Air Force Base to validate the actual flight data.
Partners: NASA Dryden; NASA Kennedy; NASA Goddard
A space-based communications system using current satellite technologies could reduce operational costs of ground-based test range assets, and is applicable to a variety of manned and unmanned research aircraft and expendable space launch vehicles.
Intelligent Flight Control System (IFCS), 1999 - 2008
The Intelligent Flight Control System (IFCS) flight research project at NASA Dryden Flight Research Center exploited a revolutionary technological breakthrough in aircraft flight controls that can efficiently optimize aircraft performance in normal and failure conditions. IFCS incorporated self-learning neural network concepts into flight control software to enable a pilot to maintain control and safely land an aircraft that has suffered a failure to a control surface or damage to the airframe.
Major control surface or airframe damage hinders an aircraft flight control system's design integrity, rendering traditional fixed control systems virtually worthless. The IFCS team integrated innovative neural network technologies with state-of-the-art control algorithms to correctly identify and respond to changes in aircraft stability and control characteristics, and immediately adjust to maintain the best possible flight performance during an unexpected failure. The adaptive neural network software "learns" the new flight characteristics, onboard and in real time, thereby helping the pilot to maintain or regain control and prevent a potentially catastrophic aircraft accident.
The primary goal of the project was to develop adaptive and fault-tolerant flight control systems leading to unprecedented levels of safety and survivability for civil and military aircraft. The IFCS project was representative of the type of flight research conducted by NASA to explore new control technologies, blending intelligent flight controls with adaptive airframe structures to expand aircraft performance and capabilities.
The IFCS testbed aircraft was a highly modified McDonnell-Douglas NF-15B Eagle that was formerly flown in the Advanced Control Technology for Integrated Vehicles (ACTIVE) project at NASA Dryden from 1996 through 1999.
The flight test results will be used in an overall strategy aimed at advancing neural network-based flight control technology to new aerospace systems designs. Many vehicle classes will be considered as opportunities arise, including commercial, fighter, transport aircraft, unmanned air vehicles, and spacecraft.
The ultimate goal of the IFCS project was to develop and demonstrate a direct adaptive neural network-based flight control system. The direct adaptive approach incorporates neural networks that are applied directly to the flight control system feedback errors to provide adjustments to improve aircraft performance in normal flight and with system failures. A secondary goal was to develop the processes of verification and validation of neural networks for use in flight critical applications.
Preliminary flight tests of an IFCS neural network that was pre-trained to the NF-15B's aerodynamic database were flown in Spring 1999. These tests validated the non-learning portions of the IFCS Generation I concept. As the aircraft flew, the pre-trained neural network provided a best estimate of stability and control characteristics based on wind tunnel information. The IFCS control algorithm used this information to adjust the control settings to stabilize the system and provide specific flying characteristics.
IFCS Generation I Tests
The IFCS Generation I flight tests, flown in 2003, used onboard algorithms to identify changes in aerodynamic characteristics. It used a Neural Network to organize and map these aerodynamic changes, and provided the flight control system with that information. The flight control system used this information to stabilize the aircraft and provide specific flying characteristics. The Generation I system was flown in an open loop. Prior to the Generation I flights, risk reduction flights were flown in 2002 that provided information to develop and refine the system prior to actual IFCS tests.
IFCS Generation II Tests
Generation II IFCS flight tests allowed the neural networks to take more direct control of the vehicle, working alongside the flight controller to adjust for any shortcomings. The neural network was more like an equal partner with the flight control system.
The performance of this system was directly compared with the performance of Generation I. The Generation II system provided quicker response to simulated failures.
The Generation II system was a direct adaptive system that applied corrections continuously and learned by observing the overall effect on performance. Because the system was more closely integrated into the flight controller, it required advances in techniques to flight-qualify learning systems.
Similar to earlier IFCS risk reduction work; risk reduction flights were flown earlier in 2005 in preparation for the Generation II tests.
Future IFCS Work
As a continuation of the IFCS Generation II, testing of two improved neural nets flew in the summer of 2008. These improved neural nets were designed to improve the handling qualities of impaired aircraft over the generation II neural net.
Partners: NASA Dryden Flight Research Center, NASA Ames Research Center, Moffett Field, CA, Boeing Phantom Works, St. Louis, MO, the Institute for Scientific Research, West Virginia University, Fairmont, WV, and the Georgia Institute of Technology.
Active Control Technology for Integrated Vehicles (ACTIVE), 1994 – 1998
Advanced flight control systems and thrust vectoring of engine exhaust were integrated into a highly modified F-15 research aircraft.
Partners: NASA, the Air Force Research Laboratory, Pratt and Whitney, and Boeing (formerly McDonnell Douglas) Phantom Works.
New aircraft designs that will be lighter, less complex, less costly, and with greatly improved performance as conventional aerodynamic controls and their systems are reduced or eliminated. Helps develop technology for the next generation of high-performance civil and military aircraft, as well as significantly cut the time spent in design by reducing complexity.
Deflected (vectored) thrust reduces drag and increases fuel economy or range as compared with conventional aerodynamic controls.
This technology will provide lower life cycle cost, simplified manufacturing, higher reliability, enhanced performance and safety, as well as, lower observability for future fighter and transport aircraft.
Those modifications included equipping the aircraft with a digital fly-by-wire control system, canards (modified F-18 horizontal stabilators) ahead of the wings and two-dimensional thrust-vectoring, thrust-reversing nozzles which redirected engine exhaust up or down, giving the aircraft greater pitch control and aerodynamic braking capability.
The new nozzles could deflect vector engine thrust up to 20° off center line, giving the aircraft thrust control in pitch (up and down) and yaw (left and right), or any combination of the two axes. This deflected (vectored) thrust can be used to reduce drag and increase fuel economy or range as compared with conventional aerodynamic controls. The nozzles are a production design that could be incorporated into current or future aircraft.
High Stability Engine Control (HISTEC), 1997
This experiment evaluated a computerized system that can sense and respond to high levels of engine inlet airflow turbulence to prevent sudden in-flight engine compressor stalls and potential engine failures. The system used a high-speed processor to process the airflow data coming from sensors on the left engine, and it in turn directed the aircraft's engine control computer to automatically command engine trim changes to accommodate for changing turbulence levels. The system can enhance engine stability when the inlet airflow is turbulent, and increase engine performance when the airflow is stable or smooth. Approximately one dozen flights were flown in the summer of 1997 to validate the HISTEC concept.
Partners: NASA Glenn Research Center; NASA Dryden; Pratt and Whitney; McDonnell Douglas; USAF.
Use of this technology could significantly reduce the cost of air travel
Use of this technology could also reduce the aircraft accident rate.
High-Speed Research Acoustics, 1997
The unique ability of the thrust-vectoring nozzles to change the "area ratio" (the difference in the geometric area between the nozzles' throat and exit) led to the F-15B (#837) being used for research in the fall of 1997 on how to reduce perceived engine noise. This flight experiment focused on validating noise prediction data that could be applied to reducing noise generated during takeoffs and landings of the High Speed Civil Transport, the proposed second-generation American supersonic jetliner. By fully expanding the nozzles' exit area, noise generated by the hot jet exhaust entering the surrounding cooler air is reduced. The acoustics research involved flying the F-15B in precise patterns over an array of 30 microphones spread out over more than a mile along the northeast side of Rogers Dry Lake.
Partners: NASA Langley Research Center
Contributed significantly to reducing the perceived noise levels of future aircraft.