STS-114 & STS-121
Boeing employees have performed a broad range of critical tasks to support NASA to return the Space Shuttle to flight. The Boeing team's efforts have included design, development, and testing of orbiter systems modifications, verification of orbiter flight certification, and overall Space Shuttle system and payload integration.
As the original developer and manufacturer of the Space Shuttle orbiter, Boeing is also responsible for sustaining engineering support to operations throughout all missions. Boeing is the major subcontractor to NASA's space flight operations contractor, United Space Alliance (USA).
NASA has designed STS-114 and STS-121 as two return to flight test missions. The Space Shuttle Discovery orbiter will be used for both flights. These two missions must be completed without any major problems before assembly of the space station can resume. Boeing has provided a wide range of support for these two missions.
STS-121
Boeing has played a major role in several key Return to Flight tasks for STS-121 (July 2006). Those tasks include:
- Completing the analysis to ensure a replacement Trailing Umbilical System Reel Assembly (TUS-RA) can be safely carried in the payload bay of the Space Shuttle. On the International Space Station, the mobile base station moves along rails on the main solar array truss to position the lab's robot arm for assembly work as required. The TUS-RA has a ribbon-like power/data cables that unreel or wind up in front and behind the cart as it moves along. One of these of these two cables was cut accidentally when a safety device failed in December 2005.
- Replacing two windows in the Orbiter with ones properly tested to handle aerodynamic loads during ascent. The windows were replaced because the vendor under tested the windows and a previous analysis under-predicted the potential loads during ascent. With properly tested windows, they will be able to better withstand potential debris impacts and the full spectrum of potential loads.
- Evaluating the effects of tin whiskering in avionics boxes. Tin whiskering is a phenomenon where tin, typically in a plated application, spontaneously develops thread-like growths from its surface. The concern is that these whiskers could break off and cause an electrical short. Through analysis and testing, Boeing has demonstrated there is sufficient redundancy in the orbiter design and the risks of an electrical short are very low.
- Assisted with the troubleshooting efforts that helped narrowed down a malfunctioning Engine Cut-Off (ECO) sensor in the ET. NASA decided to replace all four ECO sensors to ensure that launch commit criteria of requiring four out of four sensors to indicate "wet" for launch can be met.
- Boeing engineers worked closely with NASA, United Space Alliance and Lockheed Martin to determine the effect of removing foam ramps from the Space Shuttle's external fuel tank. Boeing engineers conducted analyses of the aerodynamic environments to determine the changes in heating, static and dynamic loads on the hardware of the external tank (ET). In July 2005, Discovery lost a sizeable piece of foam from the "protuberance air load" (PAL) ramp, a protective ramp designed to smooth the airflow over cable trays and pressure lines during launch. NASA decided late last year to remove the ramps based on computer modeling that indicated the pressurization lines, cable tray and attachment fittings, and the foam ice/frost ramp insulation used to prevent ice formation on the brackets, would withstand the predicted aerodynamic forces during ascent.
- Boeing engineers, working closely with United Space Alliance (USA) and NASA, have found a way to prevent gap fillers, thin spacers between the Space Shuttle's heat resistant tiles, from protruding from the belly of the Orbiter. There were multiple possible contributing causes why some of the gap fillers were found with various protrusions after the last flight. The cause was narrowed down to the installation process and a new method was developed.
STS-121 mission tested new equipment and procedures that increase the safety of Space Shuttles and also performed maintenance on the space station and deliver more supplies and cargo for future station expansion. For additional information about this mission, see the NASA STS-121 press kit (6MB Adobe PDF). To learn about Boeing contributions to this mission, please read "Gold-medal performance" (Adobe PDF) in the August 2006 issue of Boeing Frontiers.
STS-114
For STS-114 (July 2005), Boeing and NASA tackled a large number of technical challenges which included:
- Performing debris flow field simulation and wind tunnel testing to characterize the debris environment during launch.
- Conducting debris impact testing to quantify the impact damage resistance capabilities of the orbiter.
- Improving orbiter Thermal Protection System (TPS) components, including wing panels and heat-resistive tiles, to further protect the vehicle from debris impacts.
- Design and manufacture of hardware for the Orbiter Boom Sensor System (OBSS) that will be used by the astronauts to inspect the Space Shuttle during the mission.
- Assisting NASA' s team that is developing on-orbit repair capabilities should there be debris damage during a Space Shuttle flight.
- Conducting exhaustive research to evaluate the impact of shuttle design and operational changes to ensure there are no unintended consequences.
NASA divided the STS-114 mission into two parts. The primary mission objectives focused on validating the external tank process control and redesign and validating on-orbit inspection and repair procedures to make sure everything was in place to move back into station assembly mode. The other aspect of the mission was to serve as a logistics support mission, dubbed LF1, for the International Space Station (ISS). For additional information about this mission, see the NASA STS-114 press kit (9.1MB Adobe PDF).