Algor Software Used on International Space Station Project

The International Space Station (ISS) is the largest scientific cooperative program in history, drawing on the resources and expertise of 16 countries. Using Algor software, Bergaila Engineering Services in Houston, Texas, working with Johnson Engineering Corporation under NASA’s Mentor Protégé program, is designing and analyzing components both for the space station and its testing module.

Construction of many of the space station’s components is already under way. ISS assembly in orbit is scheduled to begin in June 1998* and continue for five years. The ISS will serve to foster advances in science and technology and produce direct and indirect economic benefits worth twice the cost of investment. In addition, the program will forge international partnerships and inspire the next generation of scientists, engineers and entrepreneurs.

Computer-generated drawing of the International Space Station, a cooperative scientific program supported by 16 countries to further scientific and technological research in space. The inset shows a close-up of the 7-A airlock. A replica of this component was designed for training purposes using mechanical engineering software from Algor, Inc. Digital artist's concept courtesy of NASA.

Neutral Buoyancy Lab Training Module Components

The 7-A airlock of the Neutral Buoyancy Laboratory training module will be used by space station trainees to exit the module for underwater exercises. An analysis was performed to determine the best placement of lift points for hoisting the airlock in and out of water. Based on the initial analysis results (shown left), the lift points were moved to decrease high stress levels and associated deflection in the final design (shown right). Models courtesy of Bergaila Engineering Services.

In January 1999*, an international crew of three will begin living aboard the ISS. When complete, the station will provide living space for up to seven astronauts and scientists. To train these people for maneuvers in space, a module is being constructed for the Neutral Buoyancy Laboratory in Clear Lake, Texas.

The Neutral Buoyancy Lab is a large pool 102 feet wide, 202 feet long and 40 feet deep. Modules are lifted into the pool, and astronauts practice maneuvers which will take place outside the space station. These drills, which may include attaching hoses and installing and removing fuel tanks, are used both to train the astronauts and to aid in logistical planning.

The training module replicates the dimensional and functional parameters of the ISS; however, adaptations need to be made to account for its underwater use. The module components must be strong enough to withstand the stress of support systems both in and out of the pool, the lifting system and buoyancy. In addition, stainless steel is used for the training components rather than the aluminum alloys employed in the space station.

Mark Gray, an engineer at Bergaila Engineering Services, worked on several components for the training module including the 7-A airlock, from which trainees emerge into the water. Mr. Gray and fellow Bergaila engineer Kim Wong built a 37,000 plate/shell element model of the airlock based on the ISS design using Algor's precision finite element model-building tool, Superdraw III.

“The latest version of Algor's Superdraw III has made the process of building models faster and easier,” remarked Mr. Gray. A stress analysis was executed to determine whether the airlock would endure use in the Neutral Buoyancy Laboratory.

Mr. Gray appreciates how Algor’s graphical and engineering capabilities complement each other. “The capabilities that enable me to realistically model systems and see how structures react and interact have reduced the need to make assumptions and design unnecessarily conservatively,” said Mr. Gray.

Based on analysis results, engineers at Bergaila Engineering Services and Johnson Engineering determined that the lift configuration used to move the module in and out of the pool should be changed to lower stress levels and associated deflection. In addition, engineers agreed that many of the space station's bolted connections could be welded for the stainless steel training module.

Mechanical fastening methods, such as bolting, are favored for space station flight hardware because the aluminum alloys used weaken when welded. Since stainless steel is used in the training module, welding was a better joining option.

These final modifications were made to Mr. Gray’s model in January 1998. The training module’s construction will be complete by June 1998*, when training will begin.

Flight Hardware for the International Space Station

Ross Bozeman designed this stowage platform, which will be installed in the ISS. This stress contour simulates a 500 lb. payload with translational and rotational acceleration loads in the X, Y and Z directions.

Ross Bozeman, engineering manager at Bergaila Engineering Services, used Algor to design and analyze a flight hardware component for the space station. The aluminum re-supply stowage platform (RSP) needed to weigh less than 150 lb. and be able to support up to 500 lb. of equipment. In addition, the structure’s natural frequencies had to fall within a defined window.

Mr. Bozeman designed a combined beam and plate/shell model of the RSP in Superdraw III according to NASA’s specifications.

“The updates to Superdraw III over the past year strike me as very intuitive, especially to new users,” said Mr. Bozeman. 

For each design, Mr. Bozeman conducted a series of 20 linear stress and vibration analyses. He was able to automate the process using batch files. Dozens of design variations were analyzed to determine the best 3 or 4 designs. For those few designs, Mr. Bozeman used Merlin Meshing Technology and Supergen to refine the mesh of the models before running a series of final analyses.

In addition, he conducted linear dynamic response analyses on other existing flight hardware components. The results of these analyses help engineers at Johnson Engineering to determine the net effects of launch- and crew-induced vibrations.

“The graphical representation of results in Algor has always been superior,” said Mr. Bozeman. “The wide variety of display types Algor offers has always impressed me.”

* Editor's Note: The ISS construction and assembly schedule is subject to change. Check NASA's web site (www.nasa.gov) for more information.