Light carbon-fiber structure protects heavy space cargo

  • Published
  • By Michael P. Kleiman
  • AFRL Space Vehicles Directorate
Kirtland AFB, N.M. --  The successful performance of the TacSat-2 micro satellite in December delivered on the expectations of scientists serving here, who established the foundation for this project almost 13 years ago.

Known as the Advanced Grid-Stiffened Composite Payload Fairing, the structure, 20 feet long and 5 feet wide, features a compound-based, triangular rib pattern with an outer covering that resembles a blimp-shaped design, maintains a strength that is pound per pound stronger than steel.

"The AGS Composite Payload Fairing serves as a more efficient way to use the strongest materials to work with, as it makes the most use of carbon fiber composites in their strong direction," said Dr. John Higgins, AGS Composite Payload Fairing program manager, AFRL's Space Vehicles Directorate. "This technology allows us to build stronger, lighter, low-cost structures, which can carry more payloads to orbit."

Since the 1970s, fuel tanks employed on Atlas and Delta liquid-fueled rockets have contained a casing constructed of a lone portion of aluminum reinforced with stiffeners shaped in equilateral triangles, but due to increased weight and cost, alternatives have also been investigated.

In the last three decades, federal government and private industry entities such as the National Aeronautics and Space Administration, as well as the former McDonnell Douglas reviewed the potential advantages of utilizing carbon grid-stiffened composite materials in aerospace systems.

In 1994, a group of researchers serving with the Space Vehicles Directorate developed a compound material structure with consolidated ribs using silicon rubber tooling, which expands with heat. After five years of refining and tweaking their invented prototype, the determined team designed a shroud demonstrator featuring an AGS composite structure, which during testing, performed without damage.

With the success of the innovative carbon-compound apparatus, other opportunities beckoned. As a result, the Space and Missile Systems Center's Space Development and Test Wing, also located here, partnered with the Space Vehicles Directorate to work on an AGS composite fairing for the initial Minotaur I launch vehicle. Soon the collaborative effort would grow as the technology transitioned for further development to Boeing Phantom Works, Seattle, Wash., and Orbital Sciences Corp., Dulles, Va.

"The AGS Composite Payload Fairing project has been the best example of a team effort between industry and government-related organizations. In addition, the program has used about all the technical competence and expertise the Space Vehicles Directorate has to offer to develop this innovative product," said Dr. Higgins. "The whole thing had to be integrated efficiently, and we worked with the two contractors (Boeing Phantom Works and Orbital Sciences Corp.) to ensure that they were satisfied with the grid-stiffened structure's performance and safety design."

Boeing Phantom Works constructed the initial two composite fairings, and then the Space Vehicles Directorate conducted qualification testing on one of the structures.

During the evaluations, the advanced grid-stiffened arrangement successfully held up to 125 percent of the load it would experience in service. To compliment the existing product, the team here created an acoustic blanket system to reduce the potentially damaging effects of noise (from launch) on the payload.

Orbital Sciences Corp. conducted additional assessments to ensure the hardened carbon-fiber assembly could withstand the pressure exerted on it by blast separation from their Minotaur I rocket. One of the two fairings, shipped back and forth across the country for various appraisals, ended up protecting the TacSat-2 micro satellite, which launched from NASA's Wallops Island Flight Facility, Wallops Island, Va.

"The benefits of the AGS Composite Payload Fairing consist of the product's strength, light weight, and the capability to carry and protect the payload. Because of the structure's lightness, more mass can be devoted to the payload," said Dr. Higgins. "We are currently trying to introduce the carbon compound fairing with other systems such as the Evolved Expendable Launch Vehicle."