NASA's Dryden Flight Research Center is a national gateway to the skies--and beyond. Dryden's responsibility for flight research includes everything from airplanes that use solar power to fly higher than ever before, to a future "space lifeboat" that could safely return crews to Earth in an emergency.
Present ongoing projects at Dryden, located in California's Mojave Desert include: aerospace research that bridges speeds ranging from 25 miles an hour to 10 times the speed of sound; using computers and satellite positioning technology to guide aircraft in bird-like tight formations for greater efficiency and better, safer use of crowded airspace; and twisting a high-speed jet aircraft's wings to give it better maneuverability.
Just as formations of migratory birds use their relative positions to take advantage of reduced drag, thereby increasing their range, so too can aircraft performance benefit from specific tight formation flight. One of Dryden's many projects focuses on Autonomous Formation Flight (AFF), which looks for ways to apply this advantage to aircraft.
With that premise, Dryden engineers, in cooperation with NASA's Ames Research Center, the Boeing Company, and the University of California (UCLA), are collaborating on a sophisticated blend of global positioning system (GPS) technology and inertial navigation gear that promises to give measurements of the relative positions of aircraft in formation with accuracies within six inches. The Dryden-led team believes this accuracy can be used to autonomously guide aircraft and keep them in tight formations, allowing them to reap the benefits of vortex energy caused by the lead aircraft.
Gerard Schkolnik, AFF project manager, explains: "The goal of the AFF project is to demonstrate a sustained ten percent fuel savings of the trailing aircraft during cruise flight." Air cargo companies are already looking on with interest to see if they might one day achieve such economies by dispatching their aircraft in formations using follow-on evolutions of the AFF suite being tested in the skies over Dryden. Another benefit of a mature AFF technology could be the ability to safely handle higher volumes of air traffic by treating formations of aircraft as individual units. And in space, AFF technology might enable a swarm of small satellites to congregate, creating a virtual large satellite for a specific mission.
In cooperation with the U.S. Air Force Research Laboratory and Boeing's Phantom Works, Dryden is researching the use of lighter-weight flexible wings for improved maneuverability of high-performance military aircraft in the Active Aeroelastic Wing (AAW) project.
The AAW project goal is to demonstrate improved aircraft roll control through aerodynamically induced wing twist on a full-scale aircraft. The test aircraft--an F/A-18A obtained from the U.S. Navy--has been modified with additional actuators, a split leading edge flap, and thinner wing skins that will allow the outer wing panels to twist up to five degrees. The traditional wing control surfaces--trailing edge ailerons and the outboard leading edge flaps--are used to provide the aerodynamic force needed to twist or "warp" the wing. Project engineers hope to obtain equivalent roll performance of the production F/A-18 at transonic and supersonic speeds without using the stabilators and with smaller control surface deflections. Removing the stabilators' roll control function will eliminate the "corkscrew" effect common to the F/A-18, which limits the number of rolls performed.
AAW research could also enable thinner, higher aspect ratio wings on future aircraft. This could result in reduced aerodynamic drag, allowing for greater range or payload and improved fuel efficiency. Data obtained from flight tests at Dryden will provide benchmark design criteria as guidance for future aircraft designs.
AAW technicians have completed installation and checkout of research instrumentation and avionics wiring on the modified F/A-18, along with a full-up systems checkout of the flight control software developed by Boeing's Phantom Works in the AAW flight control computer.
Structural loads testing in Dryden's Flight Loads Laboratory began in mid-March 2001. Wing twist testing occurred in early April, followed by more extensive loads calibration testing. The structural loads testing on the F/A-18's modified wings will take almost six months, followed by painting of the aircraft, a traditional rollout, and extensive systems tests and simulation before flights begin. According to Dryden AAW project manager Denis Bessette, the loads applied to the aircraft will be up to 70 percent of the design limit load, with load distribution over the wings a particularly critical item.
The two-phase AAW flight tests will begin with parameter identification flights in late 2001. Data obtained from the first phase flight series will be used to refine the AAW flight control laws, and after further software development, the second phase of research flights should take place in 2003.
The solar-powered Helios Prototype was readied for a summertime 2001 attempt at a never-before-achieved milestone in the annals of flight--sustaining horizontal flight at 100,000 feet above the Earth. Technicians for AeroVironment, Inc., the giant flying wing's manufacturer, completed installation of high-efficiency solar cell arrays on all six of the Helios Prototype's wing sections early this year. They also completed upgrades to the ground control station, the tracking antennas, and updated operational procedures.
The 247-foot-span ultralight flying wing, whose development is being funded and managed under NASA's Environmental Research Aircraft and Sensor Technology (ERAST) project, flew six low-altitude airworthiness validation flights on battery power at Dryden in the fall of 1999.
The 100,000-foot altitude flight is one of two major flight milestones set for the craft by NASA, the other being a four-day non-stop endurance demonstration flight above 50,000 feet planned for 2003. Development of a regenerative hydrogen-oxygen energy storage system which would make the multi-day continuous flight possible is progressing at AeroVironment. The system uses excess power generated by the solar arrays during the daytime to run an electrolyzer that separates water into its component parts, hydrogen and oxygen, which are then stored under pressure in specially-designed tanks. At night, the hydrogen and oxygen are recombined by the fuel cells, with electricity produced as a by-product providing power to Helios' motors.
Two subcontractors, Giner and Lynntech, have developed prototype "short-stack" fuel cells and electrolyzers, which have undergone rigorous testing. Lynntech is building full-size units that will be installed in a prototype energy storage system at AeroVironment. The completed system will then be subject to both sea level and high-altitude testing in an altitude chamber. NASA's Glenn Research Center will conduct further testing of Giner's intermediate and full-size fuel cell and electrolyzer components. Additionally, another subcontractor, Kaiser Compositek, is developing and testing composite pressure tanks for storing the hydrogen and oxygen.
On loan from the Air Force, the X-40A is an 85 percent scale version of NASA's X-37, a flight technology demonstrator testing future launch technologies in orbit and reentry from the harsh environment of space through Earth's atmosphere. The X-40A is performing a series of flights and autonomous landings as part of the X-37 program, intending to reduce the risk of flight testing the X-37, not from 15,000 feet like the X-40A, but from low Earth orbit. With such a wide range of aircraft and aerospace research advancements, Dryden Flight Research Center will continue to be a leading developer of innovative technologies with aviation applications.
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