ISS iROSA Spacewalks 100 and 101: Final Solar Array Installs

Two spacewalks set for Thursday, October 29 and Thursday, November 5 are meant to finish the International Space Station's power augmentation by installing the last two iROSA roll-out solar arrays. NASA briefed reporters on the plan, which will be US spacewalk 100 and US spacewalk 101, the 285th and 286th spacewalks supporting station assembly, maintenance and upgrades.

Why the numbers matter

US EVA 100 is counted from the first spacewalk out of the Quest airlock without a space shuttle at the station, conducted by Carl Walz and Dan Bursch during Expedition 4 on February 20, 2002. Gaurang Patel said the arrays will raise power generation capability by up to 30%, from 160 kW to up to 215 kW of total station power. The seventh iROSA will support critical station operations, including safe and controlled deorbit.

First spacewalk

NASA astronaut Anil Menon and CSA astronaut Joshua Kutryk will leave the Quest airlock to install the array on the 2A power channel. It will be Menon's fourth spacewalk and Kutryk's first. Flight director Garrett Hehn said the arrays flew up in the Dragon trunk, and 20% of the previous 99 US EVAs were devoted to upgrading station power.

Each folded array is around 750 lb and about 10 ft long. Menon will ride the station's robotic arm carrying it to the 2A outboard position, with maneuvers planned around the array's center of mass to be less tiring. Kutryk will release the final bolts. The array unfolds from about 10 ft to around 20 ft, and deployment takes about 10 minutes. Hehn compared it to a snap bracelet.

The crew will then reconnect power cables with a jumper joining the legacy array power and the new array power. That must be done in eclipse, because the cables are hot. The first spacewalk also includes setup work for the second array.

Second spacewalk

The same two astronauts head to the starboard side to install the eighth and final set on the 3A Bravo channel, which Patel said essentially completes the power augmentation upgrades. It will be Menon's fifth spacewalk and Kutryk's second. The mobile transport system will be relocated between the two. At the outboard set, Kutryk and Menon will use a "leapfrog" maneuver, swapping platforms, to close the distance the robotic arm cannot reach.

Preparation and questions

The same two astronauts were chosen for both spacewalks because the tasks mirror each other and share hardware. Flight controllers are working with the mobile transporter's channel B as prime after transaction errors on channel A, and Canadarm2 is operating nominally. Hehn said spacesuits are not entirely redundant and are aging. The neutral buoyancy lab replicates the spacewalk in chunks. Radiation is assessed using solar monitoring spacecraft, and coronal mass ejections are watched for. The next baseline spacewalks, for the Alpha Magnetic Spectrometer upgrade, are targeted for early January.