1. MAE 4261: AIR-BREATHING ENGINES
Ramjet Analysis Overview
Mechanical and Aerospace Engineering Department
Florida Institute of Technology
D. R. Kirk

2. RAMJET BASIC OPERATION
Fuel
injectors
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

3. 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

4. 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

5. 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

7. 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

8. 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

9. MISS BOMARC

10. HyFly RAMJET CONCEPT Hypersonic Flight Demonstration Program
Hypersonic Flight Demonstration Program
Cruise Flight Mach Number ~ 6
Range 600 nm (1111 km)

11. HyFly RAMJET CONCEPT http://www. designation-systems
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

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

13. 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

14. J58 SR-71 ENGINE: RAMJET/TURBOJET HYBRID

15. MAIN IDEA: TURBO-RAMJET

16. J58 TURBO-RAMJET

17. 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

18. X-51

19. 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

20. 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