UNIT 5 PROPULSION

RAMJET ENGINE
By
S.VELMURUGAN
AP/AERO

RAMJET BASIC OPERATION
• Ramjet has no moving parts
• Achieves compression of intake air by forward speed of vehicle
• Air entering the intake of a supersonic aircraft is slowed by aerodynamic
diffusion created by the inlet and diffuser to low velocities
• Expansion of hot gases after fuel injection and combustion accelerates
exhaust air to a velocity higher than that at inlet and creates positive thrust
Fuel
injectors

KEY RESULTS: RAMJET
• Begin with non-dimensional thrust
equation, or specific thrust
• Ratio of exit to inlet velocity
expressed as ratio of Mach numbers
and static temperatures. Recall that
for a Ramjet Me=M0
• Ramjet specific thrust depends on
temperature ratio across burner, tb
– Compare with H&P EQ. (5.27)
• Energy balance across burner
• Expression for fuel flow rate for
certain temperature rise of incoming
mass flow and fuel energy, h
• Useful propulsion metrics
– Specific impulse, thrust specific
fuel consumption, and overall
efficiency
 
 
 
h
m
TU
T
m
TSFC
g
m
T
I
h
T
c
m
m
T
T
c
m
h
m
M
M
T
T
M
a
m
T
T
T
M
M
RT
RT
M
M
U
U
U
U
M
a
m
T
f
overall
f
f
sp
o
p
o
f
t
t
p
o
f
o
b
o
t
t
o
o
o
o
e
o
e
o
e
o
e
o
e
o
e
o
o
o









0
0
4
3
4
0
4
3
4
1
1
1
1














































t



WHAT DID WE LEARN?
• Figure 5.9 from Hill and Peterson: Ramjet performance parameters vs. flight Mach number
• Specific thrust has peak value for set Tmax and Ta
• Specific thrust increases as maximum allowable combustor exit temperature increases
• Specific fuel consumption decreases with increasing flight Mach number

WHAT DID WE LEARN?
• Figure 5.10 from Hill and Peterson: Ramjet performance parameters vs. flight Mach number
• Specific thrust has peak value for set Tmax and Ta. Peak is around Mach 2.5
• Propulsive, thermal and overall efficiencies increase continually with increasing Flight Mach number

RAMJET POWERED MISSILES
Boeing/MARC CIM-10A BOMARC A Surface-to-Air Missile
Aerojet General LR59-AG-13 liquid rocket; Two Marquardt RJ43-MA-3 ramjets

SOME DETAILS ON BOMARC MISSILE
• Flight testing started in 1952
– First launch from Cape Canaveral in September of 1952
• Bomarc A became fully operational in 1959
– Numerous deployments from Florida to Maine defended U.S. eastern sea board
• Booster on Bomarc A was source of problems
– Fuel was too corrosive to store in missile, so fueling took place immediately
before launch (increasing time to launch)
– Fueling process was also quite hazardous, involving three steps (white fuming
nitric acid, analine-furfuryl alcohol, and kerosene)
• New model that utilizes a solid fuel booster
– Bomarc B became operational in 1961, and featured a safer solid fuel booster
and more powerful sustainers
• Boeing built 700 Bomarc missiles between 1957 and 1964, and Bomarc in active
service until 1972
• Length 46 ft. 9 in, Wingspan 18 ft. 2 in, Speed Mach 2.8, Range 250 miles,
Ceiling 65,000 ft, Cost: $ 1,154,000 per shot
• Propulsion:
– One Aerojet General LR59-AG-13 liquid rocket
– Two Marquardt RJ43-MA-3 ramjets

MISS BOMARC
http://home.att.net/~ferguspcj/mbomarc/bomarc01.htm

HyFly RAMJET CONCEPT
• Hypersonic Flight Demonstration Program
• Cruise Flight Mach Number ~ 6
• Range 600 nm (1111 km)
http://www.globalsecurity.org/military/systems/munitions/hyfly.htm

HyFly RAMJET CONCEPT
http://www.designation-systems.net/dusrm/app4/hyfly.html
• HyFly program was initiated in 2002 by DARPA (Defense Advanced Research Projects Agency) and
U.S. Navy's ONR (Office of Naval Research) to develop and test a demonstrator for a hypersonic Mach
6+ ramjet-powered cruise missile
• Prime contractor for HyFly missile is Boeing, Aerojet builds sustainer engine
• Air-launched from F-15E and accelerated to ramjet ignition speed by solid-propellant rocket booster
• Engine runs on conventional liquid hydrocarbon fuel (JP-10)
– Much easier to handle than cryogenic fuels (LH2) used on other hypersonic scramjet vehicles
• Sustainer engine of HyFly is a dual-combustion ramjet (DCR) (very complex)
– Two different air inlet systems
• Operate as a "conventional" ramjet with subsonic combustion
• Operate at hypersonic speeds as a scramjet
• First scramjet engine (hybrid or otherwise) to demonstrate operability with LH2 fuel

RAMJET POWERED MISSILES
Orbital Sciences GQM-163 Coyote: Ducted rocket/ramjet engine, Flight speed up to Mach 2.8 at seal-level
http://www.orbital.com/
Hercules MK 70 rocket booster

RUSSIA'S P-700 GRANIT LONG-RANGE ANTI-SHIP
MISSILE (SS-N-19 ‘SHIPWRECK’)
• Launched by two solid-fuel boosters
before sustained flight with ramjet
• Maximum speed believed ~ Mach 2.25
• Range is estimated at 550 to 625 km
• Weight: 7,000 kg, Length: 10 m,
Diameter: 0.85 m
• Altitude up to 65,000 ft

J58 SR-71 ENGINE: RAMJET/TURBOJET HYBRID
http://aerostories.free.fr/technique/J58/J58_01/page8.html

RAMJET VS. SCRAMJET
• Large temp rise associated with deceleration from high speed to M~0.3 for combustion
• Solution for increased flight speed: decelerate to ‘lower’ supersonic speeds in combustor
• Combustion very difficult (flame support) in a high speed flow
• Vehicle cooling requirements become very challenging

SUMMARY
• Ramjet develops no static thrust
• Relies on ‘ram’ compression of air
– Requires high speed flight
• Performance depends on increase in stagnation temperature across burner
(combustor)
• Efficiencies (thermal, propulsive, and overall) increase with increasing flight Mach
number
• Next step: We desire an engine that develops static thrust
– Put in a device to mechanically compress air (compressor)
– Put in a device to power compressor (turbine)
• Solution: Turbojet engine

INTERSTELLAR RAMJET: ‘HYDROGEN-BREATHING ENGINE’
• In this concept, interstellar hydrogen is scooped to provide propellant mass
– Hydrogen is ionized and then collected by an electromagnetic field
• Onset of ramjet operation is at a velocity of about 4% speed of light
• Typically, interstellar ramjets are very large systems
• A ramjet sized for a 45-year manned mission to Alpha Centauri would have a ram
intake 650 km in diameter and weigh 3000 metric tons including payload
http://www.daviddarling.info/encyclopedia/I/interstellar_ramjet.html

UNIT 5 PROPULSION

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UNIT 5 PROPULSION