NASA the National aerospace plane will
launch horizontally fly directly into
space complete its mission and land
horizontally like the Space Shuttle
advanced air-breathing ramjet scramjet
engines being developed by a national
team led by NASA and the Air Force will
allow NASA to fly at up to 25 times the
speed of sound because significant heat
will be generated by the NASP s--
tremendous speeds advanced engine and
engine seal designs are necessary
unlike rocket engines that carry large
heavy oxygen tanks the air-breathing
engines under development for the NASP
extract oxygen from the air
these engines will efficiently scoop and
compress air to burn with the hydrogen
fuel temperatures in the engine reach
over 5,000 degrees Fahrenheit with
pressures exceeding a hundred pounds per
square inch to operate at speeds up to
25 times the speed of a bullet
the NASP engine must meter the
combustion flow going through the engine
duct much like your car's fuel valves
the articulating nozzle panels in the
NASP engine will tailor the flow for
maximum performance
to prevent the hot potentially explosive
combustion gases from escaping past the
panels high-temperature seals are
required around the panel's perimeters
these seals must withstand extreme
temperatures seal highly distorted
sidewalls and resist abrasion over the
life of the engine advance seal concepts
are being developed at NASA's Lewis
research center these seals are made of
high-temperature ceramic materials able
to operate at temperatures up to 2300
degrees Fahrenheit above this some form
of active cooling must be employed to
stay within the operational limits of
the material one leading concept under
development is the ceramic wafer seal
which consists of multiple ceramic
wafers mounted in a channel of the
articulating engine panel the seal
accommodates and seals the large
sidewall distortions through relative
sliding of adjacent elements much like
the behavior of a deck of cards another
approach is the ceramic rope seal which
is braided out of high-temperature
ceramic fibers that maintain flexibility
at temperature both seals are preloaded
against the adjacent walls by a series
of spring-like bellows the hot
performance of the two seals were
measured at NASA Lewis using the
specially designed test fixture
though one cannot see the seals in this
picture the seals are mounted behind the
front wall of the hot test rig tests
have shown that the ceramic wafer seal
has very low leakage even at
temperatures exceeding 1,400 degrees
Fahrenheit it seals both flat and
distorted walls equally well tests of
the braided ceramic rope seal identified
key construction variables that can be
optimized to meet the target flow goal
high temperature seal technology
developed under NASA is immediately
beneficial to numerous aeronautical
space and industrial applications high
temperature seals will be required on
advanced high-temperature combustors and
nozzles being designed for future
commercial and military supersonic
aircraft NASA PI temperature seal
technology can provide an extra margin
of safety over the low-temperature o
ring seals of the shuttles solid rocket
motors and improve gap seals for the
shuttles main engines
the innovative seal work performed by
NASA Lewis under the NASA program has
earned four US patents over the last two
years while R&D magazine recognized the
ceramic wafer seal as one of the most
significant new technical products of
1990
NASA the National aerospace plane is
serving as a national focus for
advancing the state-of-the-art in access
to space and numerous supporting
technologies
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