Editing Northrop B-2 Spirit (section)

====Infrared====
[[File:B-2 inlet.jpg|thumb|The gap below the air intake has the purpose of keeping the [[boundary layer]] out of the jet engine.]]

Some analysts claim [[infra-red search and track]] systems (IRSTs) can be deployed against stealth aircraft, because any aircraft surface heats up due to air friction and with a two channel IRST is a {{CO2}} (4.3&nbsp;μm absorption maxima) detection possible, through difference comparing between the low and high channel.<ref>{{cite web |last=Radar |first=Cordless |url=http://www.flightglobal.com/blogs/the-dewline/2008/10/infamous-jsf-report-precedes-a.html |title=RAND Report Page 37 |work=Flight International |access-date=16 December 2010 |archive-date=10 May 2013 |archive-url=https://web.archive.org/web/20130510192736/http://www.flightglobal.com/blogs/the-dewline/2008/10/infamous-jsf-report-precedes-a.html |url-status=live}}</ref><ref name="fas_stealth">{{Cite web |title=VI – STEALTH AIRCRAFT: EAGLES AMONG SPARROWS? |publisher=Federation of American Scientist |url=https://fas.org/spp/aircraft/part06.htm |access-date=21 February 2008 |journal= |archive-date=13 February 2008 |archive-url=https://web.archive.org/web/20080213001551/http://www.fas.org/spp/aircraft/part06.htm |url-status=dead}}</ref>

Burying engines deep inside the fuselage also minimizes the thermal visibility or [[infrared signature]] of the exhaust.<ref name= "tucker 177"/><ref>Croddy and Wirtz 2005, p. 342.</ref> At the engine intake, cold air from the [[boundary layer]] below the main inlet enters the fuselage ([[boundary layer suction]], first tested on the [[Northrop X-21]]) and is mixed with hot exhaust air just before the [[nozzle]]s (similar to the [[Ryan AQM-91 Firefly]]). According to the [[Stefan–Boltzmann law]], this results in less energy ([[thermal radiation]] in the infrared spectrum) being released and thus a reduced heat signature. The resulting cooler air is conducted over a surface composed of heat resistant [[carbon-fiber-reinforced polymer]] and [[titanium alloy]] elements, which disperse the air laterally, to accelerate its cooling.<ref name="janes">Jane's Aircraft Upgrades 2003, p. 1711f</ref> The B-2 lacks [[afterburner]]s as the hot exhaust would increase the infrared signature; breaking the [[sound barrier]] would produce an obvious [[sonic boom]] as well as [[aerodynamic heating]] of the [[aircraft skin]] which would also increase the infrared signature.