Blackbird’s successor has a combined cycle propulsion
system for reaching hypersonic speedsInside the SR-72
O
n 1 May 1954, the Sov iet Union’s
newest bomber – the Myasishchev
M-4, nicknamed ‘Hammer’ –
soared above Red Square in Moscow. It
wasn’t long after the successful detonation
of a hydrogen bomb, and the US watched as
its former World War II ally turned into a
Cold War enemy.
Gaining intelligence was almost
impossible, as surveillance planes that
tried to enter Soviet airspace were shot
down. The Lockheed U-2 would prove to be
a complete game-changer. Developed at
what went on to become the top secret Area
51 facilit y, this plane could fl y out of reach of
enemy fi ghters and missiles, taking
detailed aerial photographs of airfi elds,
factories and shipyards. Knowledge is
power, and these images proved to the USthat there was no immediate threat and so
a deadly arms race – and potential nuclear
war – was averted.
Over the course of their history, spy
planes have become the most feared
aircraft, despite carr ying no weapons.
Deployed by government and military
forces, these eyes in the sk y can be used for
many different tasks, from patrolling
borders and gathering information behind
enemy lines, to monitoring battlefi elds for
strategic decision-making.
Getting the information they need
quickly and discreetly is the key aim for
engineers. Modern spy planes use cutting-
edge science and technolog y to do this, but
historical planes were able to achieve
amazing feats too. One such example is the
SR-71 Blackbird. It was built in the analogueage, taking off in
1964 and
performing
reconnaissance
missions until its
retirement in 1990.
Despite being 32
metres long with a
17-metre
wingspan, this
black behemoth
could fl y faster
than a rifl e bullet,
hitting Mach 3 –
three times the speed of sound, over 3,700
kilometres per hour. Its distinctive cur ved
shape with a sharp edge that ran along the
body of the plane presented ver y few
surfaces for radar detection, and using“ Throughout history,
spy planes have
become the most
feared aircraft,
despite carrying
no weapons”
Many technologies
invented for the SR-71 are
still in use today© Lock heed Mar tin/Sk un k work s; WIKI; Gett y / Illustration by Ad rian MannThe SR-72 will reach
speeds of Mach 6, double
that of its predecessorCommon nozzle
The turbojet and ramjet/
scramjet engines share an air
inlet nozzle to reduce drag.Ramjet force
The ramjet engine then
takes over, accelerating
the aircraft from Mach 3
up to Mach 5.Combustion
Air and fuel are fed into a
combustion chamber and ignited.Turbojet
The turbojet engine provides the
initial thrust to accelerate the
SR-72 from takeoff to Mach 3.Air inlet
Air is scooped into the
inlet and compressed as it
enters the diffuser.Thrust
An exhaust nozzle
accelerates the burst of
expanding hot air, producing
a huge amount of thrust.Scramjet force
The dual-mode ramjet engine switches to
scramjet (supersonic ramjet) mode to
accelerate from Mach 5 to Mach 6. It
uses supersonic air for combustion to
reach speeds of around 7,400km/h.Combined cycle
A turbojet engine is combined with
a supersonic combustion ramjet
engine for optimum performance.DID YOU KNOW? In 1974 an SR-71 flew from London to New York in under two hours – a record time that still stands to this day