Editing Advanced Tactical Fighter (section)

===Concept development===
[[File:F-22 RFI.jpg|thumb|upright=1.25|Diagram of several designs submitted for request for information (RFI)]]
In 1981, the USAF began forming requirements for the ATF, eventually codenamed "''Senior Sky''". In May, a [[request for information]] (RFI) to the aerospace industry was published by the USAF [[Aeronautical Systems Center|Aeronautical Systems Division]] (ASD), followed by another RFI for the ATF propulsion systems in June. In response, a number of aerospace [[defense contractor]]s provided design concepts for analysis by the ASD, which released their final report in December 1982.<ref>Aronstein and Hirschberg 1998, pp. 30-33.</ref> During this time, the ASD also established an internal ATF Concept Development Team (CDT) in October 1982 to manage concept development studies. As the ATF was still early in its requirements definition, including whether the aircraft should be focused on air-to-air or air-to-surface, there was great variety in the RFI responses; the submitted designs generally fell into four concepts.<ref name="ReferenceA">Aronstein and Hirschberg 1998, p. 40.</ref>

* ''Numbers Fighter'' (N): Lightweight, low-cost design trading lower individual capability for quantity.
* ''Supersonic Cruise and Maneuver'' (SCM): Approximately {{convert|55000|lb|kg|abbr=on|adj=on|sigfig=3}} takeoff weight fighter with high maneuverability and [[Energy–maneuverability theory|specific excess power]] at transonic and supersonic speeds.
* ''Subsonic Low Observable'' (SLO): An internal ASD concept that sacrificed fighter-like performance and speed for low [[radar cross-section]] and [[infrared signature]].{{refn|Despite the conceptual similarities, the SLO (based on a General Dynamics flying wing design) was separate from the ''"Senior Trend"''/[[Lockheed F-117 Nighthawk|F-117]] due to the latter's classification and special access restriction as a "black" program.<ref name="ReferenceA">Aronstein and Hirschberg 1998, p. 40.</ref>|group=N}}
* ''High-Mach/High-Altitude'' (HI): Large and fast missileer aircraft over {{convert|100000|lb|kg|abbr=on|sigfig=3}} at takeoff intended to operate well above Mach 2 and {{convert|50000|ft|m|sigfig=3}}.

Further analysis by ASD would indicate that the best air-to-surface concept was ''SLO'', while the best air-to-air concept was ''SCM''; neither ''N'' nor ''HI'' were rated highly, and responses from contractors also broadly agreed on avoiding either extremes of the quality-versus-quantity spectrum. Even with the variety of the submitted designs in the responses, the common areas among some or all the concepts were reduced observability, or [[stealth technology|stealth]] (though not to the extent of the final requirements), short takeoff and landing ([[STOL]]) and sustained supersonic cruise without afterburners, or [[supercruise]].<ref name=Sweetman_p12>Sweetman 1991, pp. 12–13.</ref><ref name="A&H1998p42-45">Aronstein and Hirschberg 1998, pp. 42-45.</ref>  It was envisioned that the ATF would incorporate emerging technologies to include advanced alloys and [[composite material]], advanced avionics and [[fly-by-wire]] flight control systems, higher power propulsion systems, and low-observable, or stealth technology.<ref name=Sweetman_p10-1>Sweetman 1991, p. 10-11, 21.</ref><ref name="Hehs1998P1">Hehs 1998, Part 1.</ref>

[[File:Advanced Tactical Fighter Systems Project Office Patch.jpg|thumb|left|ATF SPO Patch, 1990]]
By October 1983, the ATF Concept Development Team had become the System Program Office (SPO) led by Colonel Albert C. Piccirillo at [[Wright-Patterson Air Force Base]].<ref name="A&H1998p56-57">Aronstein and Hirschberg 1998, pp. 56-57.</ref> After discussions with [[Tactical Air Command]] (TAC), the CDT/SPO determined that the ATF should focus on air-to-air missions. The air-to-surface missions would be handled by the upgraded [[General Dynamics F-111 Aardvark|F-111]], the upcoming [[Enhanced Tactical Fighter|Dual-Role Fighter]] (DRF) (which would result in the [[F-15E Strike Eagle]]) as well as the then-classified [[Lockheed F-117 Nighthawk|F-117 Nighthawk]] ("''Senior Trend''"), while the air-to-air threat from the new Soviet fighters and AWACS remained.{{refn|Early on, the F-117 had been considered for hunting the Soviet AWACS, but this was deemed not effective in 1982.<ref>Aronstein and Hirschberg 1998, p. 50.</ref>|group=N}} Additionally, as with ASD and industry responses, TAC did not want the ATF to be at either extremes of the quality-versus-quantity spectrum.<ref name=Miller_p13/><ref name="A&H1998p45-54"/> The ATF would thus be a new air superiority fighter in the vein of the SCM concept with outstanding aerodynamic performance, and intended to replace the capability of the [[McDonnell Douglas F-15 Eagle|F-15 Eagle]]. In the potential scenario of a Soviet and [[Warsaw Pact]] invasion in [[Central Europe]], the ATF was envisaged to launch from bases in central England and support the [[AirLand Battle|air-land battle]] by performing [[offensive counter air|offensive]] and defensive counter-air missions against the Soviet air-to-air threats. This would then allow the DRF and other strike aircraft to perform [[air interdiction]] against ground targets.<ref name="A&H1998p45-54">Aronstein and Hirschberg 1998, pp. 45-54, 72.</ref><ref>{{cite magazine |last=Canan |first=James |date=1 April 1988 |title=Sorting Out the AirLand Partnership |url=https://www.airandspaceforces.com/article/0488airland/ |magazine=Air Force Magazine |location=Colorado Springs, Colorado |publisher=Air Forces Association |access-date=}}</ref>

With the ATF's mission now focused on air-to-air, another round of requests were sent to the industry for concept exploration and study contracts were awarded to seven airframe manufacturers for further definition of their designs.<ref name="A&H1998p56-57"/> A request for proposals (RFP) for the fighter's engine, initially called the Joint Advanced Fighter Engine (JAFE) due to its potential joint application with the U.S. Navy's short-lived Advanced Carrier-Based Multirole Fighter (VFMX), was released in May 1983 to [[Allison Engine Company|Allison]], [[General Electric]], and [[Pratt & Whitney]]. In September 1983, General Electric and Pratt & Whitney each received $202 million contracts (~${{Format price|{{Inflation|index=US-GDP|value=202000000|start_year=1983}}}} in {{Inflation/year|US-GDP}}) for the development and production of prototype engines; Allison chose to not submit a bid due to technical problems with their advanced development demonstrators.<ref name=Sweetman_p13>Sweetman 1991, p. 13.</ref><ref>Aronstein and Hirschberg 1998, pp. 207-208.</ref> The SPO also expected that avionics would be a major component of the ATF in light of rapidly advancing semiconductor technology; requests for advanced avionics components such as the integrated [[electronic warfare]] system were sent out that November.<ref name="ReferenceB">Aronstein and Hirschberg 1998, p. 61.</ref>

During this time, the SPO took an increasing interest in stealth as results from classified [[Special access program|special access]] or "[[black project|black world]]" programs such as the [[Lockheed Have Blue|''Have Blue'']]/F-117, [[Northrop Tacit Blue|''Tacit Blue'']], and the Advanced Technology Bomber (ATB) program (which would result in the [[Northrop Grumman B-2 Spirit|B-2 Spirit]], or "''Senior Ice''") promised greatly reduced radar cross sections (RCS) that were orders of magnitude smaller than existing aircraft.{{refn|The [[Radar#Radar range equation|radar range equation]] meant that all else being equal, detection range is proportional to the fourth root of RCS; thus, reducing detection range by a factor of 10 requires a reduction of RCS by a factor of 10,000.<ref>Aronstein and Hirschberg 1998, p. 270.</ref>|group=N}}<ref name="A&H1998p56-57"/><ref name="Hehs1998P1"/> The ATF requirements would place increasing emphasis on stealth to improve survivability over the course of concept exploration, while still demanding fighter-like speed and maneuverability; the combination of low observables with the SCM concept was expected to greatly reduce the lethal zone of hostile surface-to-air missiles.<ref name="A&H1998p42-45"/> As a result of stealth technology, the design details became "black" even though the ATF was a publicly acknowledged program. By late 1984, the SPO had settled on the ATF requirements and released the Statement of Operational Need (SON). The SON called for a fighter with a takeoff gross weight of {{convert|50000|lb|kg|sigfig=2}}, a [[radius of action|mission radius]] of {{convert|500|nmi|mi km|sigfig=2}} mixed subsonic/supersonic or {{convert|700|-|800|nmi|mi km|sigfig=3}} subsonic, supercruise speed of Mach 1.4–1.5, the ability to use a {{convert|2000|ft|m|sigfig=1|adj=on}} runway, and signature reduction particularly in the frontal sector.<ref name=Miller_p13>Miller 2005, p. 13.</ref><ref>Aronstein and Hirschberg, pp. 105-106, 209.</ref>