SR-71 BlackBird

18AS43 Assignment 1 a Materialistic approach
The Engineering Marvel:

Overview
01
A Brief view on various materials, alloys used; their composition and reason of
choosing.
Materials Used
02
A glance at the state-of-the art Engineering sense to manufacture advanced
systems and components.
Manufacturing Processes
03
18AS43_(Group) Assignment 1
Various challenges faced at the time of designing and operation.
Challenges Faced

Materials Used
Titanium & it’s alloys
Composites
Elgiloy Alloy
Nickel & it’s alloys
Quartz Glass
Special Paint & Coatings
Corrosion resistive Steel

 93% Of plane was made
of Special Titanium alloys
(Grade 6 Titanium)
 Aircraft’s profile demanded
materials able to withstand
prolonged exposure to high
temperatures (up to 540°C)
Titanium Alloys
 Titanium also has less
expansion due to heat. It is
light, strong, non-magnetic,
high tensile strength
 Three main alloys used
were:
• A-A110AT
• B-120VCA
• C-120AV

 Composition of three alloys is as follows:
• A-A110AT: 5%Al + 25%Sn
• B-120VCA: 13%V + 11%Cr + 3%Al
• C-120AV: 6%Al + 4%V
 Applications of alloys on different
Components:
• A-A110AT: Equipment Bay doors; Engine
inlet cases; Engine forward compressor
cases.
• B-120VCA: Most of the Bird’s skin (0.5-
1mm thick); forward fuselage rings; chine
support structure; nacelle inlet spikes;
Nose tip spike.
• C-120AV: Fuselage longerons located at
top, bottom & side.

 Most of the peripheral
assembly including large
sections of leading, trailing
edges; vertical stabilizer;
chines; inlet spikes; tail cone
were made of composites.
Composites
Composite Material(s)
 Different composite materials
were used. Some are:
• Phenyl silane
• Silicone-asbestos
 These materials were highly
heat resistive and absorbed
radar waves to good extent.

 Composite honeycomb
sandwich skin panels,
some over one inch thick
were fastened to underlying
titanium framework & were
removeable.
Composites
 They were applied to areas
experiencing temp 200-
400°C.
 External surfaces and internal
components of J-58 engine
were made of silicone-
asbestos reenforced plastic
materials.

 Nickel alloys were the
materials with most heat
bearing capacity (Up to
1200°C).
 Four major alloys were used:
• Nickel-base Rene 41 Alloy:
Ni(base)+Cr+Fe+Mo+Co+Ti+Al
(Can Withstand 870°C).
• Hastelloy-X: Ni+Cr+Fe+Mo (Can
withstand 1200°C).
• Mar-M-20-MDS:
Ni+Co+Cr+Ta+C+Zr (Was cast
with spanwise columnar crystal
grains; It’s granular structure
reduced risk of thermal shock
cracking).
• Waspaloy:
Ni+Co+Cr+Mo+Fe+Si+Mn+C+Al+
Ti+Cu+P+B+S+Zr (Can withstand
760°C, oxidation-resistant).
Waspaloy: Microstructure
Hastelloy-X: Microstructure

 Their Applications were:
• Nickel-base Rene 41 Alloy: Engine
nacelle exhaust ejector.
• Hastelloy-X: Engine compressor
Exhaust section.
• Mar-M-20-MDS: Used to make
Engine components.
• Waspaloy: Most engine components
are made out of it.
 Nickel Alloys were used
extensively in powerplant (J-58).
Nickel alloys with desired
properties were produced.

Corrosion Resistive Steel
 Blackbirds also incorporated
small amount of A-126
Corrosion resistive steel in
some parts of structure and
surface panel.
 A-126 alloy is heat treatable
and can withstand 1200°F
(650°C ).
 The alloy’s composition:
approx. 15%Cr, 26%Ni, 2%Ti,
1%Mo.

Elgiloy
 Elgiloy is a upper alloy typically
used in watch springs.
 Due to thermal soak
requirements and need to cope
with repeated stretching &
contraction; Elgiloy was used
in SR-71 for making Cables.
 Elgiloy Composition: 39-41%
Cobalt19-21% Chromium 14-
16% Nickel11.3-20.5% Iron6-
8% Molybdenum1.5-2.5%
Manganese0.15% Max
Carbon.
 Compared to other extra
advanced systems, Blackbird’s
control system operated on
very conventional fly-by-wire
system.

Quartz Glass
 Quartz is a hard, crystalline
mineral composed of silicon
and oxygen atoms. The atoms
are linked in a continuous
framework of SiO₄
 The outer
windscreen/windshield of the
cockpit was made of quartz
and was fused ultrasonically to
the titanium frame in order to
handle the stress.
 The temperature of the exterior
of the windscreen reached 600
°F (316 °C) during a mission.
Cooling was carried out by
cycling fuel behind the titanium
surfaces in the chines.
 On landing, the canopy
temperature was over 572 °F
(300 °C).

Special Paint & Coating(s)
 The blackbirds earned their
nicknames because they were
coated with a High Emissivity
Black paint.
 This black paint radiated heat.
 This black paint had
emissivity of 0.93, as
compared to 0.38 of unpainted
Titanium
 This resulted in decrease of
surface temperature by 14 to
28°C at cruising altitudes.
 The paint added extra 60
pounds to takeoff weight but it
was well worth it.

Manufacturing Processes
Introduction
Airframe and Canopy
Sensors and Payloads
Powerplant
Navigation System

“Everything had to be invented”
 The SR-71 was a completely different design from
anything else before it—and everything after, as time has
demonstrated.
 At the time, many of the technologies needed to make
these airplanes were considered "impossible." And yet,
thanks to Kelly Johnson and the amazing team at
engineers and scientists at Lockheed's Skunk Works,
they were invented from scratch—in twenty months.
Introduction

Cutaway illustrations of the twin cockpit variant of the SR-71.

Airframe and canopy
 Lockheed found that washing welded titanium
requires distilled water, as the chlorine present
in tap water is corrosive.
 Major sections of the skin of the inboard wings
were corrugated, not smooth. he heat would
have caused a smooth skin to split or curl,
whereas the corrugated skin could expand
vertically and horizontally and had increased
longitudinal strength.
 Fuselage panels were manufactured to fit only
loosely with the aircraft on the ground. Proper
alignment was achieved as the airframe
heated up and expanded several inches.
 The outer windscreen of the cockpit was
made of quartz and was fused ultrasonically
to the titanium frame

Airframe and canopy
 Ironically, the United States did not
have enough titanium to build
these airplanes, so they have to
buy it from the Soviet Union.
Imagine that: Buying the only
material in the world that could
make an spy plane from the
country you wanted to spy.
 Since all-titanium construction had
not yet become common,
Lockheed engineers and
technicians pioneered new
inspection, test, quality-control, and
manufacturing techniques.
 Lockheed had to invent new drills,
cutting machinery, powerheads for
profilers and cutting, lubricants to
increase the rate of metal removal.
Lockheed's Skunk Works's manufacturing plant in Burbank,
California.

Only 50 Blackbird airframes were built. "The dies or moulds were
destroyed as directed by then Secretary of Defence McNamara to
prevent any other nation from building the aircraft."

Engines
 The SR-71 was powered by two Pratt &
Whitney J58 axial-flow turbojet engines.
 Most of the data regarding the
manufacturing of this engine is classified
 Originally, the Blackbird's J58 engines were
started with the assistance of two Buick
Wildcat V8 internal combustion engines,
externally mounted on a vehicle referred to
as an AG330 "start cart“
 Later start carts used Chevrolet big-block V8
engines.
 Eventually, a quieter, pneumatic start system
was developed for use at main operating
bases.

Navigational system
 Nortronics, Northrop Corporation's
electronics development division, had
developed an astro-inertial guidance
system (ANS), which could correct inertial
navigation system errors with celestial
observations.
 Its "blue light" source star tracker, which
could see stars during both day and
night, would continuously track a variety
of stars as the aircraft's changing position
brought them into view.
 The system's digital computer ephemeris
contained data on a list of stars used for
celestial navigation: the list first included
56 stars, and was later expanded to 61.

Sensors and payload
 The SR-71 originally included
optical/infrared imagery systems; side-
looking airborne radar (SLAR), electronic
intelligence (ELINT) gathering systems,
defensive systems for countering missile
and airborne fighters, and recorders for
SLAR, ELINT, and maintenance data.
 The SR-71 carried a Fairchild tracking
camera and an infrared camera both of
which ran during the entire mission.
 Over its operational life, the Blackbird
carried various electronic
countermeasures (ECMs), including
warning and active electronic systems
built by several ECM companies and
called Systems A, A2, A2C, B, C, C2, E, G,
H, and M.
The SR-71 Defensive System B

Notice the titanium panels forming the skin

Challenges Faced
Potential of Existing Technology
Titanium was troublesome
Heat was the main enemy
Fuel system & leakage issues

Potential of Existing Technology
 The fact that it was designed before
the advent of supercomputing & AI
technology makes it really unique and
artistic.
 Everything had to be invented! The
Engineers had to build everything from
scratch. As no such similar
technologically advanced project was
ever undertaken.
 New methods for Part Fabrication,
tooling assembly, Construction, and
testing were discovered.
 Titanium construction was not a
common thing so Lockheed Engineers
pioneered new inspection tests, quality
control & manufacturing techniques.

Titanium was troublesome
 Lockheed technicians found the
machinability of Titanium had great
effect on overall cost of Project.
 Titanium is one of the most common
metals in crust but it’s extraction was
very difficult specially in 1960s.
 Lockheed had to invent new drills,
cutting machinery, power heads for
profilers and cutting lubricants to
increase the rate of metal removal.
 No sealant was very compatible with
Titanium and resisted so much heat.
They had tough time there.
 Ironically, U.S. imported most of the
Titanium from Soviets and the pricing
and taxation was high amid tensions
between them.

Heat was the main enemy
 The SR-71 was designed as a Spy
plane & reconnaissance aircraft by US
Airforce. So it’s design demanded
stealth & speed.
 In 1960’s the aircraft attained Mach 3.2
and cruising altitude of 85,000 feet.
 Due to immense aerodynamic drag;
the surface temperatures reached up
to 1000°C
 Even in these situations, it was
necessary to maintain max. 26°C in
cockpit. Hence, cool air (-40°C) was
feed to cockpit.
 While designing, it was taken care that
heat was properly dissipated and
didn’t harm any avionics or control
systems.

Fuel system & leakage issues
 Because it operated at high
aerodynamic heating, it used special
low vapor pressure (high Flash-
Point) fuel.
 The fuel was so difficult to ignite that
a lit math stick thrown in it’s puddle
extinguished.
 A special ignition agent called Tri-
EthylBorane shots were given to fuel
during supercrusie although only 6
shots were carried by a pilot.
 Although Blackbird included 10,000
linear feet of sealant, tanks leaked
considerable amount of fuel on
ground; as a result of provision of
expansion & contraction of tanks with
change in Temp. They had a chart for
safe amount of fuel leaked as shown
alongside.

SUBJECT
CODE
18AS43
PLANE
SELECTED
Lockheed Martin SR-
71 (Blackbird)
Faculty Dr. S Sudhagara Rajan
Chaitanya Shukla | LinkedIn
Chaitanya Shukla | Email
Chaitanya Shukla | Slideshare

SR-71 BlackBird

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