Editing Northrop B-2 Spirit (section)

====Materials====
According to the [[Huygens–Fresnel principle]], even a very flat plate would still reflect radar waves, though much less than when a signal is bouncing at a right angle. Additional reduction in its radar signature was achieved by the use of various [[radar-absorbent material]]s (RAM) to absorb and neutralize radar beams. The majority of the B-2 is made out of a [[carbon]]-[[graphite]] [[composite material]] that is stronger than steel, lighter than aluminum, and absorbs a significant amount of radar energy.<ref name= "boyne 466"/>

The B-2 is assembled with unusually tight [[engineering tolerance]]s to avoid leaks as they could increase its radar signature.<ref name="tirpak199604" /> Innovations such as alternate [[high frequency]] material (AHFM) and automated material application methods were also incorporated to improve the aircraft's radar-absorbent properties and reduce maintenance requirements.<ref name= "tucker 177"/><ref>Lewis, Paul. [http://www.flightglobal.com/news/articles/b-2-to-receive-maintenance-boost-144086/ "B-2 to receive maintenance boost."] {{Webarchive |url=https://web.archive.org/web/20130516141406/http://www.flightglobal.com/news/articles/b-2-to-receive-maintenance-boost-144086/ |date=16 May 2013}} ''Flight International'', 5 March 2002.</ref> In early 2004, Northrop Grumman began applying a newly developed AHFM to operational B-2s.<ref>Hart, Jim. [http://www.irconnect.com/noc/press/pages/news_releases.html?d=56001 "Northrop Grumman Applies New Coating to Operational B-2."] {{Webarchive |url=https://web.archive.org/web/20111209000416/http://www.irconnect.com/noc/press/pages/news_releases.html?d=56001 |date=9 December 2011}} "Northrop Grumman Integrated Systems", 19 April 2004.</ref> To protect the operational integrity of its sophisticated radar absorbent material and coatings, each B-2 is kept inside a climate-controlled hangar (Extra Large Deployable Aircraft Hangar System) large enough to accommodate its {{convert|172|ft|m|adj=on}} wingspan.<ref name=AW_20070107_Away>Fulghum, D.A. [https://archive.today/20130117150011/http://www.aviationnow.com/search/AvnowSearchResult.do?reference=xml/awst_xml/2007/01/08/AW_01_08_2007_p50-51-01.xml "First F-22 large-scale, air combat exercise wins praise and triggers surprise" (online title), "Away Game".] ''[[Aviation Week & Space Technology]]'', 8 January 2007. Retrieved 13 September 2009.</ref>