Headlines

Precision Window for the Space Station

When astronauts view Earth from the International Space Station, they will look through a glass porthole developed by Karen Scott of Aerospace.

Karen Scott of the Aerospace Houston office, flanked by Astronaut Mario Runco and Dean Eppler of Science Applications International Corporation (SAIC), looks through the space station's optical research window. (Photo courtesy of NASA)

This 20-inch-diameter window provides a view of more than three-quarters of Earth's surface and is the highest quality window ever installed in a crewed spacecraft. Astronauts will be performing long-term global monitoring with remote-sensing instruments and Earth science photographic observations.

As primary optical scientist for developing the window, Scott tested the viewing glass originally planned for the window and found that it would not support high-resolution telescopes or precision remote-sensing experiments. Her recommended upgrade was approved for the four-piece window, now consisting of a thin exterior "debris" pane, primary and secondary pressure panes, and an interior "scratch" pane.

Scott led a 30-member team from Johnson and Kennedy Space Centers, Marshall Space Flight Center, and the University of Arizona Remote Sensing Group that conducted calibration tests on the upgraded window before it was installed in the Destiny module scheduled for launch in January 2001. The team determined that the window could support a wide variety of research, including the monitoring of coral reefs and Earth's upper atmosphere. Scott's efforts in completing the tests on a tight schedule brought her a Johnson Space Center group achievement award.

Bringing Down a "Giant"

The Aerospace Corporation was recognized at a NASA press conference in June 2000 for its role in bringing down a 17-ton "giant." The Compton Gamma Ray Observatory reentered Earth's atmosphere and safely plunged into the Pacific Ocean June 4, 2000, after nine years in orbit studying gamma-ray emissions in space. It is one of the largest spacecraft ever launched by NASA.

Compton Gamma Ray Observatory. (Photo by space shuttle crew, Compton Science Support Center. Courtesy of NASA)

NASA began deliberating the probability of uncontrolled reentry after one of the observatory's three attitude-control gyros failed in December 1999. Given the spacecraft's size, scientists thought it likely that several large masses of the spacecraft could survive reentry. NASA enlisted the corporation's assistance, and Aerospace technical experts helped to design and execute the successful splashdown.

William Ailor and Kenneth Hagen participated in a NASA "red team" review to provide recommendations to NASA program management. They were assigned responsibility for reviewing the state of the remaining gyros and the likelihood of uncontrolled reentry. After NASA decided in February to deorbit the observatory, Wayne Hallman and Benjamin Mains helped develop the deorbit plan with the operations team from Goddard Space Flight Center.

Popular Science Picks "Picosats"

The smallest operational satellites ever flown-built by Aerospace with Defense Advanced Research Projects Agency (DARPA) funding-were selected by Popular Science as one of the top 100 technologies for the year 2000. About the size of cellphones, these picosatellites, or "picosats," were featured in the magazine's December 2000 issue in the "Best of What's New" section. Project director Ernest Robinson of the Aerospace Center for Microtechnology accepted an award for Aerospace at a Popular Science exhibition in New York in November 2000.

A pair of these picosats flew a groundbreaking mission in February 2000 with the primary goal of demonstrating the use of miniature satellites in testing DARPA microelectromechanical systems (MEMS). (See Crosslink, Summer 2000.) Two more picosats, launched in July 2000, are scheduled for orbital release during the summer of 2001.

Battling Buffet Loads on the Titan IVB

An Aerospace investigation has revealed new data on why the Titan IVB vehicles have been experiencing much larger than expected buffet loads during transonic flight. To identify the origin of these loads, Aerospace engineer William Engblom conducted a computational fluid dynamics simulation of the transonic flow environment.

Map of unsteady pressure loads at Mach 0.8.

"Snapshots" of pressure contours. Pair of vortices (left); new pair of vortices (right) on opposite side of core vehicle (0.035 seconds later).

Approximately 25,000 CPU hours were required to complete the calculations on a four-million-cell mesh over a real time of almost one second. Data-processing resources at the Wright Patterson Air Force Aeronautical Systems Center were key to executing this simulation accurately and quickly. The solution was obtained for the Titan IVB at Mach 0.8. Animations clearly illustrated a new, important fluid dynamic mechanism that is likely responsible for the anomalous pitch accelerations experienced on several Titan IVB vehicles. The mechanism involves strong pairs of vortices (see illustrations), which are alternately shed from the noses of the solid-rocket-motor upgrade boosters at a nearly constant frequency, causing substantial pressure loads on the vehicle surface.

This newly discovered buffet behavior is common to all multibody vehicle configurations, according to Engblom, and should be considered in the design of future launch vehicles.

Raymond de Gaston, left, and Astronaut Frank Culbertson with award. (Photo courtesy of NASA)

Preventing Power Failure on the Space Station

Raymond de Gaston, an Aerospace engineer at NASA Johnson Space Center Operations in Houston, received NASA's prestigious Silver Snoopy award for his work in preventing possible electrical power failure on the International Space Station. The award, which was presented to de Gaston by Astronaut Frank Culbertson, recognizes outstanding performance contributing to flight safety or mission success. The award is given annually to less than one percent of the space program workforce and is always presented by an astronaut. De Gaston was recognized for finding a potentially disastrous shortcoming in component quality for the station's direct-current-to-direct-current converter units. These key components alter voltage generated by photoelectric arrays and provide all usable electrical power to the station.

To Winter 2000/2001 Table of Contents