NASA Moves To Reduce Risk On Shuttle Flights; Discovery Now On Pad
NASA is taking steps to contain risks on upcoming space shuttle flights, senior space agency officials said in briefing journalists.
For example, while NASA has launched shuttles in daylight to watch for dangerous losses of foam insulation pieces, the next launch will be in evening darkness — with bright lighting on ground units substituting for sunlight in the moments just after the Space Shuttle Discovery liftoff for a mission to the International Space Station (ISS)
A critical design review is set for today to examine the foam insulation loss issue.
At some point, a return to night launches is necessary if NASA is to complete construction of the ISS by 2010, when the shuttle fleet is to be retired, according to Wayne Hale, space shuttle program manager. Only shuttles can lift some of the huge components for the space station.
Day launches can be constrained by many factors, such as a Russian Soyuz spacecraft or a Progress cargo ship going to the space station, weather problems and more. The possibilities of conflicts interfering with day launches increase in winter months when hours of darkness outnumber hours of daylight. Still, launches in daylight “are highly desirable,” Hale said.
The foam loss possibility became an issue after Space Shuttle Columbia in 2003 was damaged during liftoff by a large chunk of foam insulation, leading to later loss of the orbiter vehicle and crew during reentry.
Engineers said they would have to see 30 shuttle flights with little foam loss to have high confidence that the foam debris problem was resolved, which would be more than the entire remaining number of shuttle flights, Hale said. But they needed just two flights with little foam loss to have reasonable confidence the solution had been found, and the last two flights– Space Shuttle Discovery on July 4 and Space Shuttle Atlantis on Sept. 9 — have both launched with little foam loss and no damage to the orbiters from foam pieces. Also, Discovery wasn’t damaged by foam in a mission last year.
Discovery last week was rolled out from the Vehicle Assembly Building to Launch Pad 39B in preparation for a launch initially set for Dec. 7, but which might be moved back to Dec. 6.
Another case in point: in 2008, when a shuttle mission heads to service the Hubble Space Telescope, if the orbiter vehicle were damaged by broken pieces of foam insulation, the space station wouldn’t be there to use as a life raft for the crew on the crippled orbiter.
So NASA will have another space shuttle ready to rocket into space and rescue the shuttle crew, NASA Administrator Michael Griffin announced recently. (Please see Space & Missile Defense Report, Monday, Nov. 6, 2006, page 1.)
To be even safer, NASA will use a separate launch pad for the rescue shuttle, rather than using the same launch pad used for the blastoff of the stricken orbiter, Hale said. “You can get off [on a rescue mission with a second space shuttle] in a shorter period of time” by using a separate launch pad, Hale said.
There will a cost to using two launch pads instead of one, he said, including a slight cost financially, and in participants in the emergent Constellation program (the future manned space flight program) not having use of that second launch pad temporarily. “They can’t get in and do things they would do” otherwise, he said.
Another upcoming risk will be in the Space Shuttle Discovery mission next month to the space station, when astronauts have to shut down some of the power to the station as they engage in a massive rewiring job, following installation in September of a new P3/P4 truss and solar array electrical generating unit on the space station. That was accomplished by a mission of Space Shuttle Atlantis. (Please see Space & Missile Defense Report, Monday, September 25, 2006, page 1.)
“When you take away half the power, you hurt the redundancy” of the space station systems, according to Kirk Shireman, deputy program manager. The redundancy will return when the rewiring job is complete.
Here again, however, there will be safety moves. For example, as part of the space station is powered down, so-called “jumper cables” will be used to provide power to certain areas in the no-power section.
Some risks will remain, always, in such maneuvers, because they can’t be avoided. For example, if half the ISS is without power, and electricity is flowing only from the powered area, what happens in the unlikely event that generating power would be lost on that side?
At that point, astronauts must dig into their bag of tricks. They have prepared “for a number of ugly contingencies … failures,” Shireman said.
One of the best moves is prior preparation, to “make sure the system is in good shape” before the rewiring work begins, he said.
Aside from safety, there are other potential moments of concern in the Discovery mission would include a point in the P5 truss installation where there is just a two-inch clearance with an existing structural component, and concerns about retracting an existing array that has been in space for years.
The payload for the STS-116 Discovery mission was moved to Launch Pad 39B at Kennedy Space Center.
Workers moved the payload canister to the payload changeout room, ready for loading later into the space shuttle payload bay.
Then Discovery was moved on its transporter out of the Vehicle Assembly Building, with the crawler moving about 1 mph to Launch Pad 39B, where it arrived Friday for a Saturday loading of the payload.