mention the world's fastest aeroplane
and many will think of the concorde and
while that may have been a
record-holding passenger jet it was far
from the fastest capable of over mach 3
the lockheed sr-71 blackbird is the
holder of this title it found its use
under both the united states air force
and nasa the sr-71 introduced in the
mid-1960s was based on the formations
that its predecessor left the a12 the
a12 was one of the first aircraft
designed with its radar cross section in
mind but more on that later the sr-71
was longer and heavier than the a12
capable of longer distances thanks to a
larger fuel tank it was also designed to
accommodate a pair of tandem cockpits a
total of 32 sr-71s were built each at
the cost of around 33 million each and
while none were lost in enemy attacks 12
were lost in accidents each of them was
painted in a dark blue color to help
release as much internal heat as
possible as well as to help the aircraft
blend into the night sky this is the
origin of its nickname the blackbird
join us in this video as we explore what
it took to make a plane capable of these
unbelievable speeds and some of the
challenges it faced along the way
generally titanium is avoided in the
aerospace industry despite its benefits
which are far outweighed by its cost it
was generally only used in components
exposed to high temperatures such as
parts of the engines and exhausts as
well as some edges of the wings the cost
wasn't so much a priority with the sr-71
which is why around 80 to 90 percent of
its structure revolves around titanium
albeit an alloy that was both cheaper to
produce and easy to work with thanks to
its ability to soften at a lower
temperature the rest of the aircraft was
built from polymer composite materials
interestingly many of the surfaces were
corrugated while a smoother surface may
be more aerodynamic thus fuel efficient
having a corrugated surface would mean
that the plane's skin could expand both
horizontally and vertically making it
better resistant to the extreme heat it
would face that wasn't the only strange
thing about this design the fuselage
panels were not built to fit tight to
the frame on the ground the sr-71 wore
its skin rather loosely but true
alignment would happen as the airframe
heated up when in action often by
several centimeters the fuel system was
built in a similar way which meant when
stationary the fuel tank would drip jp7
fuel onto the ground this along with its
incredible speed and power led to the
misconception that the blackbird
required refueling immediately after
takeoff while it's true that mid-flight
refuelling would be paramount to its
long-distance success this is mostly
because on a typical mission it would
take off with a partial fuel load to
reduce stress on the brakes and tires
thanks to this it was significantly
lighter allowing it to take off even if
one engine were to fail jp7 fuel is
difficult to ignite which is why
triathlon or teb was injected to produce
high enough temperatures for the fuel to
ignite teb gave the flame a
characteristic green color to
demonstrate the dedication to its
military purpose cesium-based additives
were used to help suppress the exhaust
plume's visibility to radar several
studies into exotic fuels were conducted
including coal slurry and liquid
hydrogen but both were written off as
being unfeasible its tyres manufactured
by bf goodrich were constructed with
aluminium built-in filled with nitrogen
they would last around 20 missions and
cost almost two and a half thousand
dollars to reduce stress on landing
which would be around 200 miles per hour
the sr-71 deployed a parachute to
increase the drag onto its source of
power and the blackbird had plenty of it
a pair of pratt whitney j-58 axial flow
turbo jets produced a static thrust of
145 kilonewtons which for the time was
an extraordinary amount of force they
were so well tuned for high speed that
to start each engine up the us air force
and nasa would rely on a pair of buick
wildcat v8 mounted on a start cart
spinning each jet to around 3 200
revolutions per minute before it could
self-sustain later these were replaced
by chevrolet big block v8s which in turn
was switched out for a quieter pneumatic
system as outside air entered the engine
through the air inlets it would slow
down to subsonic speeds the plane itself
would be traveling at around mach 3.2
almost two and a half thousand miles per
hour but was often proven to be more
efficient at higher speeds depending on
the air temperature behind the quartz
windscreen which could reach up to 316
degrees celsius on a mission the cockpit
would be pressurized to an altitude of 3
000 or 8 000 meters even inside the
cockpit the temperature could reach up
to 120 degrees celsius so an advanced
air conditioning unit was needed
specially developed suits were required
to be worn by pilots with a small
opening for food via sachet and drink
via a straw if any ground-based systems
were able to detect the sr-71 travelling
at over three times the speed of sound
they would then have to tend to its 10
square meter radar cross section about
10 times larger than that of an average
human or 10 times smaller than that of a
large cargo aircraft on board the
blackbird was equipped with optical and
infrared imagery systems a side-looking
airborne radar an electronic
intelligence gathering system and
defensive systems for countering missile
and airborne fighters while early
propositions considered fitting weaponry
to the aircraft they were later
dismissed let's remember it was built as
a reconnaissance aircraft and it served
its purpose very well without the need
for any armament given the opportunity
would you ever fly in an aircraft
capable of traveling at two and a half
thousand miles per hour around nine
times as fast as a bugatti chiron or
does the 500 or so miles per hour that
the average passenger jet flies out
sound more appealing let us know in the
comments below and be sure to share this
video with fellow aeroplane fanatics and
speed freaks
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