Space Shuttle Research Is Earthshaking
echnologies developed by NASA to
protect delicate experiments from minor vibrations and movement aboard the Space Shuttle in
orbit are being applied to reduce damage to buildings and bridges from major vibrations
during severe earthquakes and high winds.
"Right now we're working on developing technological 'tools' which architects and construction engineers can use when designing more earthquake-tolerant structures and in enabling existing structures to better survive earthquakes," said Dr. Mark S. Whorton, an aerospace engineer at Marshall Space Flight Center in Huntsville, Alabama, who has been working for years to resolve microgravity environmental vibration problems that affect sensitive science experiments.
"There are several ways to reduce the effect of structural vibrations. A direct approach is to stiffen the structure, which requires changing its mass and therefore its vibration characteristics. While this may be acceptable for many terrestrial applications, the need for strong but light-weight structures in space renders this option infeasible for NASA," Whorton said.
"Clearly, for applications in the space program, lightweight but equally effective vibration mitigating alternatives were needed. We found that these technologies had down-to-earth applications as well. One way of countering structural vibrations caused by a strong gust of wind or seismic ground motion is to place sensors and force producing devices called actuators at specific locations on buildings. As sensors in the system measure the motion of the structure, actuators apply forces to counteract the structure's vibrations," Whorton said.
"One such force device would use hydraulic pistons moving counterweights. Another method involves placing adjustable tendons along the sides of structures. In fractions of a second, sensors in the systems can read the structural vibration patterns caused by earthquakes or high winds and adjust the tension on the appropriate tendons to reduce the excessive forces or motions of the building," Whorton said.
"The active control technology for vibration isolation is mature and is fully capable of doing the job. This is a technology ready now for commercial applications," Whorton said. Of the actively controlled buildings in operation today, all are in Japan with the exception of one in Taiwan. A TV tower in Nanjing, China will also be retrofitted with active vibration control. Other new construction will incorporate the technology, particularly in seismically active regions; and, of course, it may be possible to retrofit the technology to other existing structures.
For more information, contact Jerry Berg at Marshall Space Flight Center.
Call (205) 544-6540,
Fax (205) 544-5852
E-mail: Jerry.Berg@msfc.nasa.gov
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NASA and Argentina Sign Agreement
memorandum of understanding (MOU) between NASA and the Argentina National Commission
on Space Activities (CONAE), was signed recently to launch Argentine satellites SAC-C
and SAC-A of the Satelite de Aplicaciones Cientificas for experiments and technology
testing in numerous areas to benefit both the Argentine and U.S. Space programs.SAC-C will conduct correlated observations of the Earth of interest to Argentina and the United States, and also will contribute directly to the NASA Mission to Planet Earth Program. NASA will launch the satellite, currently scheduled for a Delta rocket, in May 1999.
SAC-A will be launched as a hitchhiker payload from the Space Shuttle cargo bay in 1998 on the STS-88 mission, which also is the first Space Station assembly mission. The small Argentine-built satellite will test several new space technologies for the Argentine and U.S. space programs.
The signing of these agreements reflects the continued growth and importance of civil space cooperation between NASA and CONAE. Argentina opened the doors to a partnership with NASA, establishing CONAE in 1991, and a framework agreement was signed. The level of cooperation has increased significantly since then. NASA and Argentina also are cooperating on ozone investigations and protein crystallography investigations aboard the Space Shuttle.
For more information, contact Douglas Isbell at NASA Headquarters.
Call (202) 358-1753.
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