Ramjet Analysis Overview for Air-Breathing Engines

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

10. 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

11. HyFly RAMJET CONCEPThttp://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

12. 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

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 http://aerostories.free.fr/technique/J58/J58_01/page8.html

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 http://www.daviddarling.info/encyclopedia/I/interstellar_ramjet.html