the ability to
take off in a short distance and land in
a short distance
or vertically is something aeronautical
engineers have strived towards
since world war two early attempts at
this
include the autogyro the helicopter
the vertiget and other research aircraft
today we have machines like the v-22
osprey
a tilt rotor aircraft
the quiet short-haul research aircraft
or
qsra and the rotor system
research aircraft or rsra
which are in flight testing programs at
other nasa centers
in the united states there is one
aircraft currently being used that is a
true
stovl type aircraft it is the british
made harrier
jump jet this plane is manufactured in
the united states
by mcdonnell douglas under license as
the av-8a
and av8b here at lewis research center
we are currently testing scale models of
advanced
supersonic stoval concepts hot gas
ingestion
and controls and propulsion system
technology
lewis's main role then is to develop
advanced propulsion concepts for air
breathing
aircraft a stovall is an air breathing
aircraft
we develop the engines we develop the
propulsion components that are required
to
power these type of aircraft there are
five types of propulsion concepts for
stovle type aircraft
vectored thrust ejector augmenter
augmented lift system lift plus
lift crews and the tandem fan
configuration the one that we see
the most of in the news today is the
harrier and that's the vector
thrust type of configuration it uses an
engine has four
variable nozzles on it that can be aimed
in a
either in the vertical direction or or
horizontally for forward flight each of
these systems have specific
advantages and disadvantages but one of
the main problems
is one of technology there are several
really key concepts that
propulsion technologies that have to be
developed
one of the more obvious ones is that you
in order to make these airplanes flyable
you have to get lightweight
propulsion systems nasa and the
department of defense have a major
activity going on to develop lightweight
high thrust await
basic engine concepts that applies to
all advanced fighters
in the case of stovall then there's some
other special issues
one is the lift concepts themselves the
ejector system
the raw system lift engines
those all have to be the technologies
associated with those concepts have to
be developed
specifically here at lewis we're
investigating the ejector concept
as part of our current program um
then additional items uh on the list uh
a lot of these concepts have uh complex
internal ducting that
that occurs inside the aircraft fan air
collection systems
valves and so on these things have to be
developed to make them compact
lightweight efficient yet at the same
time not have large pressure losses
at the 9 by 15 foot low speed wind
tunnel
at louis we are looking at some of the
problem areas
hot gas ingestion avoidance and ground
flow field effects
on stovall aircraft another technical
problem that we're looking at
is the hot gas ingestion problem
this is where while many of these
concepts have
hot gas which is produced forward on the
aircraft usually by burning fuel in
in the vertical lift system this hot gas
goes down hits the ground
is is reflected back up and ingested by
the inlet systems on the aircraft
and turbine engines do not like hot gas
they lose their power or they or
something else happens and
it's a major problem there are other
problems that are associated with
stovall aircraft
and in conjunction with nasa langley
research center
and nasa ames research center the nasa
lewis research center is continuing in
its quest
to produce a viable lightweight reliable
propulsion system these aircraft have to
operate efficiently at supersonic speeds
as well as at very low speeds
with very high air flows and as a result
there's a problem of getting
inlets that have high performance both
at supersonic conditions and also at
essentially static conditions while in
hover
possibly at high angles of attack which
which result in
in flow problems for the inlet system
nozzle systems are a key problem here
from the
standpoint that they tend to be in
today's aircraft very heavy if we
put the kind of requirements that a
stovall has so
so a major program has to be evolved to
develop advanced
nozzle concepts and last but not least
is the
is the main is a key problem for the
pilot and that is
the pilot has to be able to control this
beast while he's
uh doing his mission and
the harrier is a difficult aircraft to
fly
one of the areas that we in conjunction
with aims we have a joint program with
aim specifically in this area
to address how do we get the right pilot
interfaces
there to fly the airplane in a manner
which
which makes it easy for him to fly we
could build a stovall airplane today
the problem is that it would be too
heavy and not particularly practical
for what it can do for a mission okay
and
the main thing that we're trying to
develop now
is a supersonic capability an aircraft
with
adequate range and reasonable payload
and that that's the main thrust of of
the advanced technology
we know that stovall works it's a
question of getting an aircraft which
provides the
or meets the requirements that the
services want