hello and welcome to future path I'm
amreeka forsteri director of external
affairs at the NASA Lewis Research
Center in Cleveland Ohio in NASA's goal
is to try to fly higher further and
faster new materials and structures are
required to meet these goals in today's
segment we're going to look at some of
the things being done in our structures
division structures for flight
propulsion I think you'll find it
interesting let's watch flight in the
air or in space requires propulsion
systems able to withstand extremes of
mechanical stress vibration and
temperatures designing these structures
and matching available materials to the
job has always been a complicated
business and is becoming more so
requiring safety and reliability from
structures needing minimum maintenance
having the least possible weight poses a
basic contradiction which can be
resolved only by the most sophisticated
analytic methods the Lewis research
structures division is dedicated to
advancing the state of the art of
structures technology or aeronautical
space and terrestrial applications the
principal product of the division is the
development of validated analytic
methods to predict the behavior of
structural components and systems or
aerospace propulsion and power machinery
division provides not only solutions to
problems encountered in current
applications but also leadership in
setting new directions for structures
engineering to solve tomorrow's problems
today the purpose of the structures
division at Lewis research center is to
develop advanced credible design tools
these tools can then be used by
designers
to design advanced concepts for future
missions both in aeronautics and in
space we develop these methods for use
on high-speed computers and they are
validated with the state-of-the-art
laboratory equipment we can predict the
life that is the number of missions that
can be flown by the advanced concept and
we can optimize the design both from the
point of view of minimum weight or from
the point of view of lowest cost
breakthroughs in flight usually follow
developments in propulsion systems in
the early days of flight structures
design was a combination of art and
trial and error if you are developing a
rocket you built an engine derived from
earlier designs to be sure it didn't
fail you made it sturdier heavy as
technology advanced lighter stronger
materials and improve manufacturing
methods made the impossible possible but
mistakes were still made and the results
were spectacular and costly failures the
job of the structures division is to
make sure such accidents will no longer
occur they do this by applying the
latest scientific analysis possible and
by using the most up-to-date testing
equipment and methods available to do
this the staff of scientists engineers
and technicians of the division perform
work in structural mechanics structural
dynamics fatigue fracture and on
projects and applications some of the
work in structural mechanics includes
characterizing the properties of metals
used in propulsion systems by subjecting
specimens to stress and varying
temperatures researchers can predict
maximum loading and operating
temperatures and testing is performed at
very high temperatures on materials that
will be used at places like the leading
edge of the National aerospace plane
cowl
the work in structural dynamics focuses
on the forces affecting bodies in motion
when the turbine in a jet engine loses a
blade or even during a very hard landing
the vibrations that occur can cause a
propulsion system to fail tests in
dynamics can simulate a blade boss
condition to provide test data to
compare with simulation models any
rotating machine will tend to vibrate at
certain critical speeds and since modern
rotating equipment is required to
operate at ever higher speeds this
problem is increasingly important
research in the division is developing
methods for both active feedback and
passive suppression to permit operation
of equipment above critical speeds and
to reduce bearing wear high-speed
computer simulation is required for the
full dynamic analysis of rotating
machinery parallel computing developed
in the division is making this possible
by combining a large number of
processors in one transfuser
computations can be performed rapidly
enough to study high speed vibrations of
rotating components
you
studies in fatigue and fracture analysis
are performed in many of the structures
divisions labs both destructive and
non-destructive methods are used to
evaluate and characterize new materials
and sometimes a combination of both are
used to improve the analytical process
much of this work is directed toward
characterizing and understanding
advanced material systems as an example
researchers in the division sonic map a
ceramic disc and send the data to a
computer the computer outputs a color
simulation showing variations in density
defining areas where fractures should
occur later the disc is placed in a
hydrostatic chamber and fractured the
actual fracture disk is then compared to
the computer model for verification
division researchers also test advanced
fiber reinforced composite materials
under varied loads expected in aerospace
applications data collected from these
tests are used to verify mathematical
models which describe the material
behavior these models are then
incorporated into NASA computer codes
used to predict the performance of
composite structures in a variety of
applications beyond solving the problems
which can lead to failures the division
provides leadership in developing new
concepts and integrating information
from many sources for application in
areas ranging from windmills to the
Space Shuttle main engines from
fuel-efficient propellers to computer
codes for production design and
propulsion systems simulations the work
of the division provides verified
mathematical models and computer codes
that are key elements of today's
computer based design analyses for
flight propulsion systems as well as
many other systems with similar problems
using the products of the structures
division designers can better predict
the life of a component by constructing
it on the computer thereby saving time
and material while
venting costly failure future aerospace
systems will require advanced capability
on board computation and real-time
sensors will combine to make it possible
to monitor the health of advanced
systems active elements could be
included to make it possible to suppress
dynamic instabilities structural
tailoring to account for local stresses
and local hot spots may be the only way
to take advantage of the new lightweight
high temperature yet very brittle
materials computational simulation will
allow designers to make rapid affordable
and feasible designs probabilistic
methods will allow designers to quantify
risk and make trade-offs between
performance and life combination these
capabilities will allow those designers
to operate and design closer to the
limits such capability will allow us to
build systems that we couldn't build
before to carry out missions that
conceivably couldn't be carried out with
the development of these capabilities
the structures division hopes to play a
major part in bringing them about a
special combination of experienced
in-house staff and facilities in the
Lewis research structures division has
been tailored to meet the challenges and
needs of a new age of spaceflight and
aviation the work of the division
continues to evolve technology and will
take us into the next generations of
flight our second segment is about a
process developed at Lewis that we're
very proud of an engineer in our
materials division developed a process
called arc sprayed mono tape let's find
out about it and some of its many uses
unfazed by extreme fire not temperatures
possessing amazing strength a strength
beyond belief its creation one of
outstanding engineering achievement the
new the ultra advanced composite
materials being developed by NASA Lewis
Research Center in Cleveland Ohio to
understand this fascinating field we
must start with basics and determine
exactly what is a composite material
possibly the easiest way to visualize a
composite material is to offer the
example of a tennis racquet the arm and
frame part of the rocket is made by
combining two distinct materials
graphite fibers which give it strength
and a low-temperature glue or binder
which hold the fibers together that
allows it to be fashioned into shape
this is a composite material to
different parts each with a different
function research in this area began
about 25 years ago when minut whiskers
were discovered growing on electrical
devices the whiskers were found to be
single grain crystals that when tested
proved to be very strong in later
research work the whiskers were used in
the making of bulk materials today
instead of whiskers fibers like silicon
carbide tungsten and graphite are used
with a glue or binder to make such
things as engineering and sports
products there are some products though
that need to be able to withstand higher
temperatures
at the same time it's also necessary
that they be lightweight and stiff which
incidentally are very important
requirements for just about anything
intended for use in space to meet the
more demanding requirements a glue or
binders such as aluminum or titanium may
be used for other products that need to
be heat-resistant at even higher
temperatures a nickel or iron base alloy
is combined with even certain carbide
fibers or tungsten fibers there are
several ways to do this and one of them
is the arc spray process this method was
developed right here at NASA but one of
our engineers Leonard Westfall he works
in the advanced metallic branch of
NASA's materials division recently mr.
Westfall described exactly how the arc
process works the process works like
this we have an arc spray gun which is
attached to a large vacuum chamber
inside the vacuum chamber is a drum that
has our real strong fibers found on the
surface at a very regular spacing the
arc spray gun works by having two metal
wires coming into the gun an electric
arc is struck between the tips of the
wires the electric arc is sufficient
intensity to cause the water tips to
melt I pressure stream of neutral gas
and will usually use our gun very clean
argon is sprayed on this molten on the
mold and wire tips causing the molten
metal to dislodge from the from the
wires and to be vaporized into very very
fine particles in sprayed and we aim it
right on this drum surface
thin sheet that's formed can be as big
as two drum surface the thin sheet mr.
Westfall was talking about is called a
mono tape it comes off the drum very
easily because a teflon spray is applied
first the spray allows the material to
get hard and yet not stick to the drum
it simply peels off composite mono tapes
are used to make composite shapes which
are rather complex structures requiring
extremely high strength in order to make
the structure as strong as possible the
mono tapes must be positioned in certain
directions to do this the mono tape is
cut into small pieces and stacked one on
top of the other on the first piece all
fibers are placed in one direction on
the next piece the fibers are put in the
opposite direction of those on the first
piece this alternation of the fibers
direction is continued on the pieces in
order to maximize the structure strength
in different directions the small pieces
of composite mono tape usually are glued
together by a method called hot pressing
very heavy pressure is applied to the
stack while it is subjected to a
temperature of almost 2,000 degrees
Fahrenheit as the metal gets squeezed
together any small imperfections in the
mono tape disappeared and the metal
pieces blend together resulting in a
perfectly solid plate cut into thin
strips the plates are used extensively
at NASA for testing purposes engineers
have been able to make large tubes by
using a pressing guide to shape it they
have made demonstration turbine blades
for jet engines these blades are located
very close to the place where air mixed
with fuel is burned as combustion takes
place the expanding gases hit the blade
causing it to turn it's easy to see why
the blades must be able to withstand
extremely high temperatures presently
there are five NASA programs in which
arc spray mono tape plays a major role
our two programs deal specifically with
the space shuttles main engine since the
material now used to make the main
engine is cracking due to thermal shock
NASA is working with tungsten reinforced
super alloys to replace it these
composites in tests so far have proven
to be more shock resistant stronger and
able to withstand higher temperatures
than the present material the second
program deals with the reinforcement of
a combustion liner in the space shuttle
mr. Westfall explains a combustion liner
is a contoured shape that is Hydra
liquid hydrogen cold and it's the vessel
that the liquid oxygen and liquid
hydrogen burned in and you have very
very high temperatures inside this
combustion liner and typically it's made
out of copper or strong copper alloy the
problem this combustion liner is
experiencing is the copper alloy is
deforming due to the very high
temperatures and the stresses that are
generated in the thin inner wall causing
in a while to deform and actually
correct and the liquid hydrogen is
leaking out we are putting tungsten
fibers in the inside layer of the
combustion liner to strengthen to
selectively strengthen the inner wall of
the combustion liner this is an example
of one of the test specimens that we
make and we have tungsten fibers
reinforcing the inside surface of this
specimen alright this specimen then will
be tested in a rocket test chamber under
conditions very very similar to the
Space Shuttle main engine and the
material will be tested to to failure we
predict a much longer life with our
tungsten reinforce copper than the
current copper alloy that's being flown
in space shuttle today also regarding
space the third program has
with the creation and development of
very strong tools to hold liquid metals
and heat pipes for nuclear reactors
because of the tremendous pressure the
tubes will have to withstand a new
material is needed that is much stronger
than the one now used using the
composite process engineers are adding
tungsten fibers to the present material
to strengthen it and again in support of
space power the next program is working
to develop a specific container and will
be able to take high temperatures and
amounts of pressure which the current
container cannot in this case the power
being generated would be for a space
station the composite material that has
been developed is three to four times
stronger than the present one surpassing
the program's goal of finding a
substitute container for present
temperature and pressure levels the
engineers at NASA have created one that
can be used as power demands go up in
the future the final program developing
composite materials for use in space
deals with the improvement of radiators
again NASA engineer Leonard Westfall
explains these tubes I talked about
before have radiator panels hooked on on
the back of them to get rid of the heat
all right we're developing fiber
reinforced radiator panels that are made
out of graphite fibers that I have very
very high thermal conductivity and
thermal conductivity is the materials
ability to conduct heat very quickly
alright these fibers conduct heat
extremely fast and we put them in and
copper as a high-temperature glue copper
also has very high thermal conductivity
and so what we end up with is a
structure that has higher thermal
conductivity than copper is very very
stiff and light and this saves weight it
increases the efficiency of the radiator
panels and makes the whole cooling
scheme work much
much better at NASA there is also very
exciting work being done to support the
national aerospace plane the plans for
this remarkable plane call for it to
take off from the ground and fly up
right into orbit it would fly like an
airplane but it's jet engine at higher
altitudes and speeds would become like a
rocket and boosted into space NASA's
advanced metallics branch is working on
developing a fiber-reinforced inner
metallic material out of which to build
the plane currently the plane severely
lacks a suitable material there are
three vital requirements that the
material must have it must be
lightweight highly resistant to extreme
heat and very strong since it will be
used primarily as a major structural
component the composite material being
tested and developed uses ceramic fibers
the intermetallic matrix and ceramic
fibers together form a material that
could be the solution to one of the
planes most pressing needs in all the
research in all of these programs with
all of the discoveries breakthroughs and
amazing new products tested and those
actually in use still according to mr.
Westfall the present work is quote just
scratching the surface in composite
materials besides the fibers in
existence today there are many many
others with great potential that need to
be developed and tested NASA's goal to
develop even stronger fibers that can
work at even higher temperatures some of
the structures nASA has been working on
will be used for the National aerospace
plane or commonly known as nasp naspa
when it is built will have a unique
capability of taking off from any
airport and fly directly into space
let's learn more about nasp
imagine taking off from an airport
runway flying at three to five times the
speed of sound at altitudes of 20 miles
or even higher a few short hours after
departure you come to a stop halfway
around the world or maybe you took off
from a runway and flew directly into
orbit to work in space and then you
returned landing on a conventional
Airport runway the National aerospace
plane will try to make both scenarios a
reality NASA and the Department of
Defense have done research on hyper
sonic technology for many years the NASP
technology demonstrator will be a highly
advanced explain a new member of the
elite special research aircraft that
includes the x1 which in 1947 was the
first aircraft to break the speed of
sound and fly supersonic in the early
1960s the x-15 became one of the first
manned hypersonic aircraft and reached
speeds of Mach 7 for about 4,500 miles
per hour one of the key technological
developments of the x30 or NASA are in
the propulsion area an air-breathing
hydrogen-fueled supersonic combustion
ramjet engine or scramjet engine is now
being developed for speeds from about
Mach 7 to Mach 25 the engine uses the
velocity of the vehicle to compress air
as it is rammed into the intake this
compressed air is then mixed with
gaseous hydrogen at this stage to
generate high thrust a development on
which we will focus is materials here to
speak on that is Matt
with the advent of the the aerospace
plane there's become a need for a lot of
new material development beyond a shadow
of a doubt we need new materials all
right and these new materials will most
probably be composite materials but
instead of using a metal matrix based
composite will be using our epoxy based
will be using a metal matrix based
composite all right metal matrix being
copper for instance one of the big
problems NASA is facing with the advent
of the National aerospace plane deals
was not only finding the right materials
to use but in cooling them as well we
have to figure out some way of making a
very strong material that's going to
survive in a high temperature
environment and what we're going to have
to do is actively cool this material all
right by putting some kind of a
cryogenic fluid behind a gaseous
hydrogen or liquid hydrogen which is
very cold and X is a good heat transfer
medium to take heat away from the
leading edge so on on one side of the of
the material on the inside of the wing
for instance there'll be a lot of
coolant rushing through to cool the
inside down and on the outside you'll
have a very hot surface and that is why
we need the high heat conductivity with
our instance you look at fighter jets
that's travel Mach 1 or Mach 2 or even
the Concorde which goes up to Mach 2 you
see that their wings are very narrow at
the leading edges okay and there's a
problem with that because the smaller
the leading edge gets the more difficult
it is to cool and the hotter it gets
because it's such a small it's just such
a small point lying out there in the
free stream that it gets it gets very
warm very quickly the National aerospace
plane is one of the projects being
developed by NASA for future space use
but we cannot expect it to do all of our
work in space the National aerospace
plane being something that will possibly
be able to supplement the shuttle fleet
or or maybe even replace it but
obviously if you have an airplane that
can take off from a runway and go to
orbit with some people in it and go
the space station for instance or
something like that obviously it would
have to be capable of shuttle type
operations as far as payload goes I
think moving big things like space
station components or say for instance
they want to go to Mars and they have to
get some big boosters up there or
something like that I don't see the
national aerospace plane taking that
kind of payload up there the National
aerospace plane is expected to yield a
high payoff for the United States in the
early 21st century with reduced space
launch costs vastly reduced transit time
on long-haul air routes major
investments by private enterprise in
commercial space ventures and sustained
us preeminence in aeronautics with all
of the social and economic benefits that
accompany it this is a Mariko forest
area wishing you would buy and hope
you've enjoyed our show I hope you walk
along the future path again with me at
NASA's Lewis Research Center in
Cleveland Ohio
you