yee@trident.arc.nasa.gov (Peter E. Yee) (11/21/89)
Bruce Buckingham
Kennedy Space Center, Florida Nov. 16, 1989
KSC RELEASE NO. 118-89
KSC ENHANCES ABILITY TO MANUFACTURE TPS TILES ON SITE
Kennedy Space Center recently passed a milestone in the
timely processing of orbiters by acquiring the machinery and
equipment necessary to manufacture and process thermal protection
system tiles on site.
As NASA moves toward its goal of launching up to nine
Shuttle missions in 1990, a key component in meeting the
challenge is insuring that all the necessary thermal protection
system products are in place on the orbiters.
In support of this effort, KSC's Thermal Protection System
(TPS) Facility recently upgraded its capabilities and began the
production of low and high temperature reusable surface
insulation tiles. Formerly, these tiles were obtained from two
California plants.
In the TPS Facility, located across from the Orbiter
Processing Facility, Rockwell technicians recently machined from
a block of raw silica the first flight-worthy tile manufactured
entirely at KSC. That specific tile is now in place on the
orbiter Columbia's port side fuselage near the Star Tracker door.
Columbia will be flown on Space Shuttle Mission STS-32 in
December 1989.
Chuck Finney, manager of the TPS Facility at KSC, said, "by
having this capability at KSC, we are able to shave several days
off the time it normally takes to manufacture and ship a tile
from our California plants. This ability is especially important
late in the flow if a tile is damaged and has to be replaced
prior to rollout or launch."
At KSC's TPS Facility, technicians cut from a large block of
pure white silica fiber a piece that is approximately the size
needed to fit into a specific cavity on the orbiter. A final cut
is then made on the tile with diamond-tipped cutters, allowing
for a tolerance of only a few thousands of an inch. The cutting
devise, called a Contour Milling Machine, permits technicians to
create an exact replica of the original tile by tracing the
contours of a previously manufactured mold. This is a process
similar to that used when cutting a new key by tracing the
outline of an old one.
"The Contour Milling Machine cuts accurately even the
slightest sidewall angles," Finney said. "It takes all the guess
work out of the machining process."
After all the cuts are made and the new tile is the exact
shape and size needed to fit perfectly into its cavity on the
orbiter, the tile is weighed and sprayed with an alcohol mist.
This is followed by the application of a ceramic coating. The
alcohol allows the coating to penetrate and adhere to the tile's
dusty silica texture.
Following the coating application, each tile is placed into
an oven pre-heated to temperatures reaching up to 2250 degrees
Fahrenheit for a period of 65 to 95 minutes, depending on the
kind of tile being processed. The heating process bakes the
coating, producing a hard, glass-like finish for higher re-entry
temperature allowances, many of which exceed 3,000 degrees
Fahrenheit.
Finally, each tile is weighed a second time to determine the
exact amount of coating applied. The tile is stenciled with its
own identification number, waterproofed and installed on the
orbiter.
The entire manufacturing process, from the time the block of
silica is received at KSC to the time the tile is installed on
the orbiter, takes about three days -- approximately half the
time necessary if the tile is manufactured in California and must
be shipped to Florida for installation.
Though the TPS Facility is currently capable of producing
only the basic cube-style tiles, within the coming year a
computer operated, 5-axis milling machine will allow production
of every tile needed on the orbiters -- some of which have eight
to ten cut surfaces.
About 24,000 tiles cover 70 percent of the orbiter's
external surface. The remaining areas are shielded by felt
reusable surface insulation blankets, also produced at KSC's TPS
Facility, and reinforced carbon-carbon.