Editing Bell X-2 (section)

==Design and development==
The Bell X-2 was developed to provide a vehicle for researching flight characteristics at speeds and altitudes in excess of the capabilities of the [[Bell X-1]] and [[Douglas Skyrocket|D-558 II]], while investigating aerodynamic heating problems in what was then called the "thermal thicket".<ref>https://archive.org/details/Aviation_Week_1957-10-21/page/n55?q=aviation+week+thicket+thermal p.112</ref>

The Bell X-2 had a prolonged development period due to the advances needed in aerodynamic design, control systems, materials that retained adequate mechanical properties at high temperature, and other technologies that had to be developed. Not only did the X-2 push the envelope of manned flight to speeds, altitudes and temperatures beyond any other aircraft at the time, it pioneered [[throttleable]] [[rocket engine]]s in U.S. aircraft (previously demonstrated on the [[Messerschmitt Me 163|Me 163B]] during World War II) and digital flight simulation.<ref name="Machat  p. 37"/> The XLR25 rocket engine, built by [[Curtiss-Wright]], was based on the smooth variable-thrust [[JATO]] engine built by [[Robert H. Goddard|Robert Goddard]] in 1942 for the Navy.<ref>{{cite book|last=Lehman|first=Milton|title=Robert H. Goddard|year=1963|publisher=Da Capo Press|location=New York|page=351}}</ref>

Providing adequate stability and control for aircraft flying at high [[supersonic]] speeds was only one of the major difficulties facing flight researchers as they approached Mach 3. For, at speeds in that region, they knew they would also begin to encounter a "[[thermal barrier]]", severe heating effects caused by [[Drag (physics)|aerodynamic friction]]. Constructed of [[stainless steel]] and a [[copper]]-[[nickel]] [[alloy]] called [[K-monel|K-Monel]], and powered by a liquid propellant (alcohol and oxygen) two-chamber Curtiss-Wright XLR25 2,500 to 15,000&nbsp;lbf (11 to 67&nbsp;kN) sea level thrust, continuously throttleable rocket engines, the swept-wing Bell X-2 was designed to probe the supersonic region.<ref name="Machat  p. 37"/>