Oleg Zabluda's blog
Sunday, April 29, 2012
 
Reading old issues of "Aviation Week & Space Technology" magazine, came across the sentence, I don't see often, but...
Reading old issues of "Aviation Week & Space Technology" magazine, came across the sentence, I don't see often, but I wish I would: "As the airplane decelerates, the [engine switches to ramjet mode] to provide sustained thrust down to around Mach 4]. How do you decelerate an air-breathing airplane to Mach 4? Read full quote below: 
"""
Passing through Mach 1.5, with drag coming down, the inlet ramp doors to the turbine engines are partially closed as the thrust from the ERJs builds up. By Mach 2 the rockets are turned off, and then at Mach 2.5 the turbine inlets are fully closed [...]


For the challenging push from Mach 2.5 to Mach 4, [engine switched to DMRJ mode].

The scramjet operates like two ramjets in this mode up to Mach 4.5, at which point the vehicle relies solely on the scramjet, [up to] Mach 7-8.

Following completion of the mission, the vehicle decelerates and the door to the ERJ is opened to provide sustained thrust down to around Mach 4. As the vehicle decelerates below Mach 3, the inlets to the turbine engines are opened and at a lower Mach number these are re-started for the final powered rendezvous with a tanker and/or recovery to a runway.
"""
http://www.military.com/features/0,15240,232190,00.html
http://en.wikipedia.org/wiki/Scramjet_programs
http://web02.aviationweek.com/aw/mstory.do?id=news/awst/2011/06/13/AW_06_13_2011_p22-332894.xml

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