Space Station computer problem solved: NASA's fourth spacewalk on Sunday

William Atkins
Monday, 18 June 2007 00:16

Science - Space

Microsoft Office 365

After a set of six computer crashed over the past few days, Russian cosmonauts and U.S. astronauts had to scramble to get them up and running again. After many hours of brainstorming possible problems and solutions, the actual problem was finally isolated: a faulty power switch.

Analysis of the origin of the problem has centered around a static build-up of charged particles on the outside of the Space Station. Charged particles impinge on the Station due to its position outside of the protective webbing of the Earth’s atmosphere. Friction causes them to build up on the Station, and as the structure increases in size, more charged particles have a chance to lock onto the ISS structure.

After the newest piece of hardware was attached to the Station--the massive metal beam, which holds the third solar array and rotary joint--somehow its presence altered or disrupted the field of the charged particles. This change in the electromagnetic field caused the computers to fail.

ISS Expedition 15 commander Fyoder Yurchikin and ISS flight engineer Oleg Kotov spent long and trying hours rewiring the computers in order to bypass the power outlet that went bad. After successfully re-routing the wiring and correcting the bad switch, four of the six computers were re-started on Friday, June 15th.

Luckily, the other two computers, which would not re-start and were planned for replacement during the next Russian trip to the Station, also came to life a day later (Saturday).

As of early Sunday morning, the first four computers remain on, while the other two computers have been switched to “cold standby mode” so they are off but available if needed in the future. Only the oxygen generating device is still not operating of all the various systems adversely affected by the computer failure.

Currently, the computers are running nominally. However, the computers will be tested on Monday, a day before Space Shuttle Atlantis and its seven-person crew leaves on Tuesday, June 19th. The final test of the computer system is to make sure its thrusting capability is normal and will be able to function by itself--so the Station does not need to rely on the Shuttle's thrusting jets while docked to the Station.

Atlantis and its STS-117 crew have been cleared for departure from the Space Station on Tuesday, after a protruding gap in a thermal (insulating) blanket over one of the OMS pods was successfully repaired. However, mission managers at the Mission Control Center at the Johnson Space Center (Houston, Texas), have told the STS-117 crew that they can stay for one additional day if the situation warrants it.

Sunday’s fourth spacewalk, scheduled for 6.5 hours in duration, by STS-117 mission specialists Patrick Forrester and Steven Swanson, will be to activate a rotating joint on the new S3/S4 truss segment. The rotating joint, called the Solar Alpha Rotary Joint (SARJ), will allow the set of solar panels to move in order to track the Sun and receive a maximum flow of the Sun’s rays for electrical generation. They will also make sure that the the Drive Lock Assembly 2 (DLA-2) is working properly. The DLA-2 is one of two mechanisms that control (or drive)  the rotation of the SARJ.

The spacewalking astronauts will also install a camera, remove a keel pin and drag link, install a debris shield onto the Destiny laboratory, and remove a GPS (global positioning system) antenna. In addition, the pair of astronauts will install a computer network cable between the U.S. and Russian sections of the Space Station.

The fourth spacewalk began at 12:25 p.m. EDT (16:25 GMT) and is expected to last six-and-one-half hours.