Next Shuttle Mission to Kick Start Tricky ISS Construction

A computer generated view of the International Space Station after NASA's STS-115 mission, which will deliver the Port 3/Port 4 truss segment and two new solar arrays (right) to the orbital laboratory. CREDIT: NASA/JSC.

HOUSTON - When NASA's space shuttle Atlantis launches toward the International Space Station (ISS) this month, it will kick off an increasingly complex set of missions to complete the orbital laboratory, agency officials said Friday.

Slated to launch toward the ISS on Aug. 27, Atlantis and its STS-115 astronaut crew will haul a 17.5-ton addition to the space station's main truss and two new solar wings to double power production.

"It's great to be back flying an assembly mission," said STS-115 lead shuttle flight director Paul Dye during a press briefing here at NASA's Johnson Space Center today. "We've flown a couple of test flights where we've proven the shuttle's back and flies well. Now we're going to get back to the business of expanding the space station and that's very exciting."

Atlantis' STS-115 spaceflight will mark NASA's first dedicated ISS construction mission since late 2002. The orbital construction work stalled after the 2003 loss of NASA's Columbia orbiter and its seven-astronaut crew, which grounded the space agency's fleet for more than two years while engineers developed new safety modifications. Since then, NASA's Discovery orbiter has flown two test flights to shakedown those enhancements.

With Atlantis' upcoming mission NASA is poised to resume an at least 15-shuttle flight sequence to complete the ISS by the orbiter fleet's 2010 retirement.

"You can imagine that in 18 shuttle flights, that's going to be a busy period for the program," said ISS program manager Michael Sufferdini, including NASA's recent STS-121 mission and two reserve flights into his construction mission count. "But it's why we're here and we're looking forward to the challenge."

A tricky mission

At nearly 35,000 pounds (15,875 kilograms), Atlantis' truss and solar array cargo is by far the heaviest ISS element to ride in an orbiter cargo bay to date. It is designed to generate about 20 kilowatts - about one-fourth of the station's power needs - or enough electricity to support about six average homes.

Installing the $371.8-million truss segment, connecting its power and data lines to the ISS, and deploying its twin solar arrays on the station's port side will require no less than three spacewalks by two teams of STS-115 astronauts.

To ensure a successful construction job, spacewalkers must work smoothly with flight controllers and engineers on Earth, as well as their fellow crewmates inside the ISS and Atlantis.

"These are extremely intense, extremely tightly choreographed missions," NASA mission operations representative Phil Engelauf said. "Probably more so than we've done in the past."

The first of many

NASA's STS-115 mission is just the start of an ambitious plan to complete the ISS.

It will take one more shuttle flight - STS-116 aboard Discovery set to launch on Dec. 14 - to bring the station's new solar arrays online, then two more spaceflights to deliver two additional massive power modules to the orbital lab. A fourth solar array is already aboard the ISS, but will have to be moved into its final position during an upcoming shuttle flight.

Once all four solar arrays are in place and functioning, the real heavy lifting begins to launch long-waiting modules and international laboratories toward the outpost.

"There is very little wiggle room," Sufferdini said the ISS assembly plan. "Over the next four years, every flight is very full, very busy."

But despite the daunting path that lies ahead, station managers are confident they will hit their target.

"We have prepared long and hard for this," Sufferdini said of the road ahead for the ISS. "This is what we've been planning for, this is what we've trained for, so we're ready to go do this assembly task."

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