Wright XRJ47

The Wright XRJ47 was an American ramjet engine developed in the 1950s to help propel the rocket-launched SM-64 Navaho supersonic intercontinental cruise missile. Although the design flight Mach Number was 2.75, a peak flight speed of Mach 3.0, at altitudes up to about 77000 ft, was envisaged. This very large ramjet had a number of design problems, including some difficulty in light-up. Development of the Navaho missile was cancelled along with the ramjet engine in 1957.

XRJ47
Type Ramjet
National origin United States
Manufacturer Wright Aeronautical

Design

The single cone supersonic intake supplied ram air to a long annular diffuser terminating at the aft-mounted cylindrical combustion chamber. The centreline of the intake system was gently curved, presumably to line up the intake face with the flow-field of the missile nose section.

The combustion chamber flame-holder consisted of a center-body pilot region, with three annular V-gutters interconnected by slanted radial V-gutters. Fuel jets were of variable area design.

A heat-shield, with multiple exit ports, provided cooling air for the jetpipe and the fixed area ratio convergent-divergent propelling nozzle. The exit diameter of the nozzle equaled that of the combustion chamber.

Specifications (XRJ47-W-5)

Data from Aircraft Engine Characteristics Summary: Ram-jet XRJ47-W-5[1], Preliminary evaluation of flight-weight XRJ47-W-5 ram-jet engine at a Mach number of 2.75[2]

General characteristics

  • Type: Ramjet
  • Length: 390 in (9,900 mm) combustion chamber plus ducting and diffuser
  • Diameter: 48 in (1,200 mm) (combustion chamber)
  • Intake lip area: 636 sq in (4,100 cm2)
  • Combustion chamber area: 1,810 sq in (11,700 cm2)
  • Nozzle throat geometric area: 1,182 sq in (7,630 cm2)
  • Nozzle exit geometric area: 1,810 sq in (11,700 cm2)
  • Dry weight: 1,011 lb (459 kg)

Components

  • Compressor: Ramjet inlet/diffuser
  • Combustors: approx 1,887 K (2,937 °F; 1,614 °C)
  • Combustion efficiency: 83.3%
  • Burn time: 6500 s
  • Fuel type: JP-5 (F-44 / AVCAT)

Performance

  • Maximum thrust: 3,792 lbf (16.87 kN)
  • Air mass flow: 59.8 lb/s (27.1 kg/s)
  • Fuel consumption: 10,548 lb/h (4,784 kg/h)
  • Specific fuel consumption: 2.782 lb/lbf/h (283.7 kg/kN/h)
  • Thrust-to-weight ratio: 3.75
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References
  1. Aircraft Engine Characteristics Summary: Ram-jet XRJ47-W-5. www.avialogs.com. 1957.
  2. Welna, Henry J.; Reilly, Dwight H. (1955). Preliminary evaluation of flight-weight XRJ47-W-5 ram-jet engine at a Mach number of 2.75 (PDF). Lewis Flight Propulsion Laboratory, Cleveland, Ohio.

Further reading
  • Arrighi, Robert S. (2016). Bringing the Future Within Reach: Celebrating 75 Years of the NASA. NASA.
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