The Space Shuttle Atlantis orbiter has been fitted with sensors in the leading edges of the orbiter wings that would provide real-time warnings if they take a hit from falling chunks of foam insulation during launch, crew members said.

In an earlier incident, foam insulation ripping loose from the external fuel tank hit a wing leading edge on Space Shuttle Columbia, punching a hole in the wing. Later, as Columbia headed back toward a landing, the blistering-hot gases of reentry rushed inside the wing and caused structural failure. The orbiter and crew were lost Feb. 1, 2003.

That led to improvements on the Space Shuttle Discovery external fuel tank, eliminating or reducing foam insulation in some areas, protuberance air ramp removal, and more.

It worked. During a brilliant July 4 launch on a mission to the International Space Station (ISS), only tiny pieces of foam broke loose, and that occurred too late in the flight to cause any damage. Discovery returned to a smooth landing.

That’s good, but no reason to assume no problem could arise in future launches, according to Atlantis crew members at a news conference at Kennedy Space Center, Fla. Atlantis is slated to launch on a mission (STS-115) to the ISS in a window beginning Sunday, Aug. 27.

While the great post-landing condition of Discovery is encouraging, the crew said that further precautions will be taken.

Aside from sensors in the wing leading edges to record any hits from insulation breaking free during launch, there also will be a minute check of the Atlantis orbiter vehicle after it soars into space to be sure there is no damage, similar to the inspection of the Discovery orbiter vehicle as it neared and then docked with the ISS.

As well, in the impending Atlantis mission, the orbiter will undock from the ISS a day early so there can be a late inspection of the vehicle. This will permit examination of the orbiter for any damage it may have suffered from micro-meteorite debris blasting in from space while it was docked to the ISS.

The inspection will focus on many areas of the orbiter vehicle, including the underside, so see if the belly has damage or has a problem such as protruding gap fillers between the heat tiles.

If damage is discovered during the post-undocking inspection, the orbiter vehicle has enough propellant in its thrusters system that it could rendezvous and re-dock with the ISS.

Prior to the July 4 Discovery launch, NASA leaders outlined how a damaged shuttle orbiter wouldn’t be sent into reentry, at least not until it was repaired. Instead, the shuttle crew could use the ISS as a cosmic life raft until being picked up by other spacecraft for a return to Earth.

If damage is detected and repairs are feasible, they could be performed in a spacewalk (extra vehicular activity, or EVA).

As it is, there will be ample EVAs during the mission, as astronauts become construction workers, laboring to assemble more components of the ISS.

NASA has set a challenging schedule of 16 shuttle launches over the next four years, in a drive to complete the space station assembly before shuttles cease flying. The shuttles are key to the goal, because their cargo bays are large enough to accommodate the bulky components that must be bolted into place on the artificial moon.

“The flights ahead will be the most complex and challenging we’ve ever carried out for construction of the International Space Station in orbit,” said Mike Suffredini, NASA station program manager, speaking to journalists at Johnson Space Center in Houston. “The station literally becomes a new spacecraft with each assembly mission, and that will be true starting this year with dramatic changes in its cooling and power systems, habitable volume, utilization capability as well as its appearance.”

With the remaining shuttle missions, NASA will embark on a series of flights as difficult as any in history to complete the International Space Station.

The station is nearly halfway through assembly. The next four flights will bring new truss segments, massive structural girders, to the complex. The new segments will increase the mass of the station by almost 40 tons.

Two of the trusses include huge sets of solar array wings, totaling more than 17,000 square feet (a typical new home has less than 2,500 feet of interior floor space), and more than 130,000 solar cells. The new segments include giant rotary joints to allow the tips of the station “backbone” to move as the massive panels track the sun.

Together, the new arrays will add 50 kilowatts of power for the complex. The increased electrical power will set the stage for the addition of European and Japanese laboratories that will far surpass any previous research capability in space.

The installation of the new truss segments and unfurling of the arrays require unprecedented robotic operations. Those operations will use the shuttle and station’s Canadian- built mechanical arms to delicately maneuver school bus-sized station components into place, according to NASA.

The operations will rely heavily on the station’s mobile transporter, a sort of space railway that positions the robotic arm along the truss to install the components, the space agency explained.

Later this year, the station and shuttle crews face a unique challenge to activate a permanent cooling system and the new power sources.

They must rewire the orbiting laboratory and change its electrical supplies without interrupting the continuous operation of any of its critical systems. Once the power grid is in place, additional shuttle flights will launch a connecting node and the European and Japanese laboratories.

“The assembly of the station on these flights has no parallel in space history,” Suffredini said. “We have planned, studied and trained for these missions for years. We know they will be hard, and we may encounter the unexpected. But we are eager to get started, and there is tremendous excitement building in NASA and among our international partners.’

The station’s assembly and maintenance in orbit, the long-duration spaceflight experience gained aboard the complex, and the research into the effects of long spaceflights contribute to NASA’s plans for future missions to return to the moon and travel beyond, according to NASA.

The current station represents only a fraction of its eventual capabilities. Between now and station completion:

• The volume and mass of the station will more than double. The interior of the space station will be larger than a five-bedroom house with a cabin volume of 33,023 cubic feet. When completed, it will have a mass of almost a million pounds.
• The number of research facilities on the complex will more than triple. The percentage of total power dedicated to research will increase by 84 percent.
• The total power generated by the complex will almost quadruple.
• The station’s truss, currently 134 feet long, will grow to 354 feet, the longest man-made object to fly in space.
• To construct the station, more than 100 international space flights will have been conducted on five different types of vehicles launched from four different countries.
• More than 140 spacewalks, totaling nearly 800 hours, dedicated to assembly and maintenance of the space station will have been completed. That is more spacewalks than were conducted in all of U.S. space history before construction of the station began.

There have been 115 space shuttle flights, of which 18 were dedicated to the space station. With 15 remaining assembly flights planned to the station, more than one-quarter of all shuttle flights will have been dedicated to station assembly.

Those spacewalks are physically demanding for the astronauts performing them, said mission specialist Heidemarie M. Stefanyshyn-Piper. She will participate in two spacewalks during the mission.

Working in a bulky space suit, under strong air pressure, while grappling with heavy components and tools, is strenuous work, she said.

Physical training to develop upper body strength helps to meet the challenge, she said. But even then, “six hours in the suit is a long time.”