Another perfect score

ISS performance earns Boeing another 100% score determination

BY ED MEMI

The International Space Station's performance has earned Boeing its sixth consecutive 100 percent score determination for on-orbit performance from NASA.

The rating of the Boeing-built hardware and software is based on the success of the ISS mission and the safety of the crew. The score determination by NASA lets Boeing retain previously awarded money. A rating of less than 100 percent would require Boeing to return some money to NASA.

Boeing has exceeded NASA expectations, which include successful on-orbit assembly of each new element, subsystem performance in line with design requirements, and the provision of planned resources, such as power, to support science objectives. During the on-orbit performance assessment, NASA evaluates subsystem performance, assembly, payload support and resolution of in-flight anomalies.

The on-orbit score determination provides an incentive to make sure hardware works properly when on orbit. The Boeing success demonstrates execution in delivering for the customer—and boosts the bottom line.

Boeing is the prime contractor for the U.S.-developed hardware/software and integrating contractor for the U.S. and international partner segments. With more than 26 complex elements and more than 10 distributed subsystems that must perform perfectly together in more than 20 different vehicle configurations, the station is the nation's most ambitious endeavor in space.

Leading up to the score determination, NASA and Boeing participate in an extensive assessment that examines how new hardware has performed.

"Over the last three years, it has been mostly software that has gone up on station, but we are also assessing whether earlier hardware is still performing as expected," said Harry Johnson, a Boeing systems integration engineer who helps prepare the hardware and software performance briefing to NASA on the annual score determination.

The ISS was designed to be maintained and supported, and some failures are expected. Boeing external hardware and software has on average been experiencing only about one-fifth the rate of failure predicted, thus requiring fewer spacewalks for repairs.

"Boeing has also done a great job, together with NASA, of supporting the hardware on orbit," said Matt Duggan, ISS Mission Operations manager. "We have also come up with creative ways to extend hardware life using different operations methods."

One example is the Beta Gimbal Assembly, the joints that rotate the solar arrays on the station toward the sun for electric power generation. In the current configuration of the Station, the solar arrays are 90 degrees from the original design orientation on the end of the truss.

"In this orientation, the array is moving differently and a lot more than it was designed to move as it tracked the sun. We started to see some bad signs from the joint when stressed," Duggan said. "We jumped in there quickly and designed a couple of new ways to operate it to make sure the stresses on the ball bearings and joints were distributed properly, eliminating any added wear."

Also, new ISS attitudes were developed, much different from the original design attitude. Different attitudes are flown to put less stress on certain hardware.

Although additional station hardware is waiting for rides on future shuttle flights, Boeing-built ISS hardware is on orbit now, performs well and represents the key elements of the completed design. Boeing and its suppliers built about 80 percent of the U.S. side of the ISS.

"We really have the full Boeing design represented right now on the Space Station in orbit," Johnson said. "We now know that the Boeing design for the phased development and manufacture of hardware has been proven."

edmund.g.memi@boeing.com