Volume 9, Number 5 • September/October 2001 • Aerospace Technology Development

Inflatable Wing Proves Itself

During test flights of the I2000 inflatable wing aircraft, the radio-controlled (R/C) I2000 was airlaunched from an R/C utility. As the I2000 separated from the carrier aircraft, its inflatable wings “popped-out,” deploying rapidly via an on-board nitrogen bottle. Photo provided by Dryden Flight Research Center.

Dryden Research Engineering staffers and Projects personnel have been flying a deployable, inflatable wing technology demonstrator experiment. The inflatable wing team includes Jeff Bauer, Jim Murray, Joe Pahle, Tony Frackowiak, Bob Allen and John Redmond. They have worked hard to get the test vehicle, the I2000 radio-controlled (R/C) airplane, to the project’s current point of success.

Three successful flights have taken wing. During the flights, the team air-launched the I2000 from an R/C utility vehicle airplane at an altitude of 800–1,000 feet. As the I2000 separated from the carrier aircraft, its inflatable wings “popped-out,” deploying rapidly via an onboard nitrogen bottle. The aircraft remained stable as it transitioned from wingless to winged flight. The unpowered I2000 glided down to a smooth landing under complete control.

Dryden’s inflatable aircraft project manager Jeff Bauer noted that, “with these tests we have put some reality behind the many imagined applications for inflatable winged aircraft.”

There is data to verify and validate computer models of inflatable wings for the future. The I2000 was equipped with a miniature flight data recorder designed by Jim Murray. That data, in addition to video and the photographic records, provides valuable insights into the aircraft’s flight dynamics.

“We are particularly interested in the dynamics of the vehicle during the rapid wing deployment, the transition from wingless flight to winged flight. We proved that we have a good flying vehicle during the transition to wings fully deployed,” says Joe Pahle, project engineer.

Flight testing of the I2000 followed a conservative “build-up” approach common in developmental flight testing. They began flying the I2000 with rigid wings having the same physical dimensions as the inflatable wings. Following successful flights with the conventional rigid wings, the actual inflatable wings were flown pre-inflated on the I2000. These risk-reduction efforts were all geared to narrowing the possibility of trouble in launching and flying with the deployable wings. Tony Frackowiak, of Dryden’s model shop, built all the glider models and the R/C aircraft used in the project, and served as the I2000 pilot.

“There were no surprises since I was well-prepared for the actual wing deployment flights,” says Frackowiak. “We flew the I2000 build-up style in the powered mode with the wings pre-inflated. The drop and wing deployment was so smooth that the rest of the flight and landing was uneventful.”

The inflatable wing has a span of 5.5 feet. In the undeployed stowed state, the wings fit in a container the size of a small coffee can.

An onboard compressed nitrogen gas source at 1,800 psi is used to inflate the wings in flight. Wing deployment time is typically on the order of 0.33 seconds, almost faster than the human eye can see. The wing pressure after inflation (180–200 psi) is sufficient to give the 15-lb I-2000 aircraft a load capability in excess of 3 g.

With the I2000 flights completed, the project’s impending goal is to successfully fly a four-foot-long X-24A model with inflatable wings. The X-24A model effort is a complementary but separate effort in demonstrating the utility of inflatable wings.

The X-24A shape was chosen due to the fact that it has a well-established aerodynamic database. It represents lifting body vehicles in general and has upper body flaps for additional roll control. The inflatable wings do not have flight controls, so the body flaps are critical for flight control. The I2000’s tail surfaces filled the gap on the standard configuration airplane. Potential advantages of utilizing inflatable wings on future lifting body vehicles include providing greater cross-range and lower landing speeds than totally wingless vehicles.

Potential applications of inflatable wings include Earth science aircraft, any volumetrically limited aircraft and planetary research aircraft. In addition, a Helios-type high-altitude, long-endurance platform could conceivably carry multiple small deployable inflatable wing aircraft to release as “probes” to more closely investigate areas of interest located by the platform’s sensors.

The deployable inflatable wings were constructed by Vertigo, Inc., as a subcontractor for a U.S. Navy Phase II Small Business Innovation Research contract. The contract previously utilized the wings tested on a gun-launched vehicle to add glide capability.

Inflatable aircraft have been around since the 1960s. Goodyear Tire Company built and flew several full-sized, entirely inflatable two-person aircraft under military contract. Furthermore, Goodyear lab-tested several small inflatable lifting body reentry vehicle models. These models rapidly inflated rearward out of solid ballistic reentry nosecones. The nosecones remained attached, forming the nose of the inflated vehicles.

However, these aircraft used low-pressure (7–9 psi) air to inflate and keep the structures inflated. The wings of the Goodyear aircraft were not cantilevered, therefore requiring external support in the form of cables running from the fuselage to the wings.

The deployable inflatable wings used by Dryden team members are relatively high pressure at 180–200psi. The current wings are manufactured differently using an advanced high-pressure material known as Vectran. As they are cantilevered, the tough wings support their own weight, as well as the weight of the aircraft in flight. Q

For more information, contact James Murray at Dryden Flight Research Center, 661/276-2629 or murray@rigel.dfrc.nasa.gov Please mention you read about it in Innovation.

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