The Space Shuttle brings a new dimension to space research, as was first demonstrated dramatically on April 14, 1981, when the gleaming black and white craft landed and rolled to a stop at Edwards Air Force Base. The Shuttle can transport payloads with ease not only to space but also from space, and the Long-Duration Exposure Facility (LDEF) has been tailored to utilize this two-way transportation capability.
Specifically, the LDEF has been designed to provide a large number of economical opportunities for science and technology experiments that require modest electrical power and data processing while in space and which benefit from postflight laboratory investigations with the retrieved experiment hardware. In fact, many of the experiments developed for the first LDEF-STS mission are completely passive and will depend entirely on postflight laboratory investigations for the experiment results.
Like the Shuttle, the LDEF is reusable, and repeat missions are planned, each with a new complement of experiments. The first LDEF mission is currently scheduled for early 1984 and subsequent missions are envisioned, possibly every 18 months.
The LDEF is essentially a free-flying cylindrical structure. The experiments on LDEF are totally self contained in trays mounted on the exterior of the structure. LDEF can accommodate 86 experiment trays, 72 around the circumference and 14 on the two ends.
The LDEF is delivered to Earth orbit by the Shuttle. In orbit, the Shuttle remote manipulator system (RMS) removes the LDEF from the Shuttle payload bay and places it in a gravity-gradient stabilized attitude. After an extended period in orbit, which is set by experiment requirements, the LDEF is retrieved on a subsequent Shuttle flight. The Shuttle RMS is used again during the retrieval to capture the LDEF and return it to the payload bay. (See fig.1.)
The LDEF operation focuses on experimenters in the user community who conceive, build, and mount their respective experiments in trays for attachment to the LDEF. As LDEF has no central power or data systems, the primary interface with the LDEF which is of concern to the experimenters is the mechanical and thermal interface of the experiment to the tray. The LDEF....
...does provide initiation and termination signals to experiments at the start and end of the mission. Any power and/or data systems required by the experiments are included by the experimenter in his respective tray.
Fifty-seven science and technology experiments involving investigators from the United States and nine other countries are planned for flight on the first LDEF mission. These experiments, a number of which include additional subexperiments, have been organized into four categories: ( 1) materials, coatings, and thermal systems; (2) power and propulsion; (3) science; and (4) electronics and optics. Each of the experiments is discussed in this document. The arrangement of these experiments on the LDEF structure is illustrated in figure 2.
The LDEF, which was built at NASA Langley Research Center, is a 1 2-sided open-grid structure made of aluminum rings and longerons (fore and aft framing members). (See fig. 3.) The LDEF is 30 ft long and 14 ft in diameter and weighs 8000 lb. The aluminum (6061-T6) center ring frame and end frames are of welded and bolted construction. The longerons are bolted to both frames, and intercostals (crosspieces positioned between the main rings) are bolted to the longerons to form intermediate rings. The main load of the...
...LDEF is transmitted to the orbiter through two side support trunnions on the center ring. A keel fitting on the center ring gives lateral support.
The end support beam, attached by a pin joint to one end frame, will take vertical loads and ensure that loads through the attachment fittings are static. The end support beam also reduces the effects of thermal distortion and other misalignments when LDEF is redeployed into the orbiter's payload bay. A fitting to allow attachment of the orbiter's remote manipulator system is located in a tray near the center ring frame.
Typical trays for mounting experiment hardware to the periphery of the LDEF structure are 34 in. wide and 50 in. Iong. (See fig. 4.) Trays for mounting hardware on the end frames are smaller (34 in. square). The depths of the trays vary as required by the experiments. Tray depths being used on the first LDEF mission are 3, 6, and 12 in. Typical experiment weights that can be....
.....accommodated in the trays range from 180 to 200 lb for the peripheral and end trays, respectively. The combined weight of the LDEF and the experiments for the first mission is approximately 21 400 lb.
For additional information regarding LDEF capability and operations, or future opportunities to fly experiments on LDEF, please contact: