Discovery Will Fly
From Refurbished Launch Pad
(11 July 2005) While eliminating
the debris that sheds from the Space Shuttle's External Fuel Tank has been one
of the primary requirements for the Return to Flight mission, work to eliminate
hazardous debris went far beyond the Tank.
When
Discovery launches, the Shuttle stack will depart from a structure that will be
cleaner than ever thanks to a major corrosion abatement effort that began in
April of 2004 and was completed in March of this year. The pad will be
virtually rust-free.
The extensive corrosion control project at Launch
Pad 39 B has corrected decades of exposure to the damaging affects of one of
the most corrosive environments in the world. Additional work on Pad A is
currently underway.
Harry Moore, who is part of the United Space
Alliance (USA) technical operations staff of Construction Management/Corrosion
Control, said the original plan was to treat the corrosion "hot spots" on the
fixed service structure and the rotating service structure of the launch
pads.
"But since the existing coating is at the end of its 10-year
life span, and since we had down time, we decided on a full corrosion control
effort," he said.
The first step of the 11-month corrosion control
project at Pad B was to strip the 247-foot steel launch tower down to bare
metal, ridding the surfaces of all the old coating and getting rid of the
rust.
Preparation for the blasting to take off the rust and paint took
place in April. Critical items such as pneumatic tubing and light fixtures had
to be covered with a heavy-duty plastic. Then, the abrasive blast cleaning
began. Workers from Ivey's Construction, the Merritt Island contractor handling
the job, hit the metal with a spray of crushed coal slag, a by-product of coal-
fired power plants. Moore said the crushed slag is applied with a pressure of
90 pounds per square inch.
"It could cut your desk in half," he
said.
The blasting was finished in January this year and the coating
was applied in February and March. Applying the coating was a two-step process.
First, a basecoat of inorganic zinc was applied. Then a topcoat was applied to
protect the zinc.
That topcoat is a mixture of mostly Portland cement
plus a few other "proprietary ingredients," according to Moore. The mixture was
developed by private industry specifically for KSC to deal with the acidic
residue left behind by the Solid Rocket Boosters that help propel the Shuttle
into space.
In addition to protecting the pad structures from rust
degradation, the corrosion control effort aims to reduce the likelihood of
foreign object debris, or FOD, a key CAIB concern.
In the past the
main focus of corrosion control was preserving structural integrity. Now,
following recommendations of the CAIB, corrosion control is also focused on
reducing debris from pealing paint and rusted flakes of metal. Corrosion now
falls under critical debris.
This change requires more inspection and
stepped-up maintenance day-to- day. Under the new system, any object the size
of a quarter or larger (0.01 pounds of mass or more) will be considered to have
a potential impact on launch.
In addition, a three-step process has
been implemented to monitor debris. The first step is a "clean as you go"
system in which all pad workers monitor for debris they may have created, and
eliminate it as they work. Second, there are daily "walk-down" inspections of
the tower by a designated employee. Finally, once a week, managers perform
walk-downs to check for debris.
This new system complements an
existing corrosion tracking program that involves photographing all sections of
the pad structures and filing those photos in a database.
All of these
efforts - both new and old - have put USA on track for providing one of the
cleanest, safest launch platforms ever for the Return to Flight mission.
United Space Alliance, established in 1995, is a leader in space
operations offering extensive experience in space launch and recovery
operations; mission planning and control; flight hardware processing; space
flight training; on-orbit assembly, payload deployment and servicing;
rendezvous/proximity operations and docking; large-scale integration and
sustaining engineering. United Space Alliance serves as NASA's prime contractor
for the Space Shuttle and provides operations services for the International
Space Station. United Space Alliance employs more than 10,000 people in Texas,
Florida, and Alabama.
(source: United Space Alliance)