Lockheed F-117A Nighthawk
F-117A ndi chizindikiro cha kupambana kwaukadaulo waku America pa Cold War.
F-117A Nighthawk idamangidwa ndi Lockheed poyankha ku United States Air Force (USAF) kufunikira kwa nsanja yomwe imatha kulowa munjira zodzitchinjiriza za adani. Ndege yapadera idapangidwa, yomwe, chifukwa cha mawonekedwe ake osazolowereka komanso luso lankhondo lodziwika bwino, idalowa m'mbiri ya ndege zankhondo mpaka kalekale. F-117A idakhala ndege yoyamba yotsika kwambiri (VLO), yomwe nthawi zambiri imatchedwa "stealth".
Zomwe zidachitika pa Nkhondo ya Yom Kippur (nkhondo yapakati pa Israeli ndi mgwirizano wa Aarabu mu 1973) zidawonetsa kuti ndege idayamba kutaya mkangano wake "wamuyaya" ndi machitidwe oteteza ndege. Machitidwe ojambulira pakompyuta ndi njira yotetezera ma radar ndi "kutsegula" ma electromagnetic dipoles anali ndi malire awo ndipo sanapereke chivundikiro chokwanira cha ndege. The Defense Advanced Research Projects Agency (DARPA) yayamba kuganizira za kuthekera kwa "bypass" yathunthu. Lingaliro latsopanoli lidakhudza chitukuko chaukadaulo kuti achepetse mawonekedwe owoneka bwino a radar (Radar Cross Section - RCS) ya ndegeyo mpaka pamlingo womwe umalepheretsa kuzindikirika kwake ndi ma radar.
Kumanga #82 ya chomera cha Lockheed ku Burbank, California. Ndegeyo idakutidwa ndi zokutira zomwe zimayamwa mu microwave komanso utoto wotuwa.
Mu 1974, DARPA idakhazikitsa pulogalamu yomwe imadziwika kuti Project Harvey. Dzina lake silinali mwangozi - linatchula filimuyo "Harvey" mu 1950, munthu wamkulu yemwe anali kalulu wosawoneka pafupifupi mamita awiri wamtali. Malinga ndi malipoti ena, ntchitoyi inalibe dzina lovomerezeka isanayambe siteji ya "Have Blue". Imodzi mwamapulogalamu a Pentagon panthawiyo inkatchedwa Harvey, koma inali yanzeru. Ndizotheka kuti kufalikira kwa dzina loti "Project Harvey" kudalumikizidwa ndi zochitika za disinformation kuzungulira zomwe zidachitika panthawiyo. Monga gawo la pulogalamu ya DARPA, idapempha njira zamakono zothandizira kuchepetsa RCS ya ndege yomwe ingathe kumenyana. Makampani otsatirawa adaitanidwa kuti achite nawo pulogalamuyi: Northrop, McDonnell Douglas, General Dynamics, Fairchild ndi Grumman. Ophunzira nawonso adayenera kudziwa ngati ali ndi zida zokwanira komanso zida zopangira ndege yotsika kwambiri ya RCS.
Lockheed sanali pamndandanda wa DARPA chifukwa kampaniyo sinapange ndege yankhondo zaka 10 ndipo adaganiza kuti mwina alibe. Fairchild ndi Grumman adasiya chiwonetserochi. General Dynamics idaperekedwa kuti ipange zida zatsopano zamagetsi, zomwe, komabe, zidalephera kukwaniritsa zomwe DARPA idayembekezera. McDonnell Douglas ndi Northrop okha ndi omwe adapereka malingaliro okhudzana ndi kuchepetsa mawonekedwe owoneka bwino a radar ndikuwonetsa kuthekera kwachitukuko ndi ma prototyping. Kumapeto kwa 1974, makampani onsewa adalandira PLN 100 iliyonse. Mapangano a USD kuti apitirize ntchito. Panthawiyi, Air Force inalowa nawo pulogalamuyi. Wopanga radar, Hughes Aircraft Company, nawonso adatenga nawo gawo pakuwunika momwe mayankho amagwirira ntchito.
Chapakati pa 1975, McDonnell Douglas anapereka ziwerengero zosonyeza kutsika kwa gawo la radar la ndege kuti likhale "losawoneka" ndi ma radar a nthawiyo. Kuwerengera uku kudatengedwa ndi DARPA ndi USAF ngati maziko owunikira ntchito zamtsogolo.
Lockheed imayamba kusewera
Panthawiyo, utsogoleri wa Lockheed udazindikira zomwe DARPA idachita. Ben Rich, yemwe kuyambira Januwale 1975 anali mtsogoleri wa dipatimenti yapamwamba yotchedwa "Skunk Works", adaganiza zotenga nawo gawo pa pulogalamuyi. Anathandizidwa ndi mtsogoleri wakale wa Skunks Works Clarence L. "Kelly" Johnson, yemwe adapitirizabe kugwira ntchito monga injiniya wamkulu wa gululo. Johnson wapempha chilolezo chapadera ku Central Intelligence Agency (CIA) kuti aulule zotsatira za kafukufuku wokhudzana ndi miyeso ya gawo la radar la Lockheed A-12 ndi ndege zowunikiranso za SR-71 ndi D-21 reconnaissance drones. Zida izi zidaperekedwa ndi DARPA monga umboni wa zomwe kampaniyo idakumana nazo ndi RCS. DARPA inavomereza kuti ikhale ndi Lockheed mu pulogalamuyi, koma panthawiyi sakanatha kulowa naye mgwirizano wachuma. Kampaniyo idalowa mu pulogalamuyi ndikuyika ndalama zake. Ichi chinali cholepheretsa kwa Lockheed, chifukwa, osakhala womangidwa ndi mgwirizano, sanasiye ufulu ku mayankho ake aliwonse aukadaulo.
Mainjiniya a Lockheed akhala akukambirana ndi lingaliro lambiri lakuchepetsa malo owonetsera bwino a radar kwakanthawi. Engineer Denis Overholser komanso katswiri wa masamu Bill Schroeder anafika pa mfundo yakuti kuonetsa bwino kwa mafunde a radar kungatheke pogwiritsa ntchito malo ang'onoang'ono ang'onoang'ono ang'onoang'ono ang'onoang'ono monga momwe angathere pamakona osiyanasiyana. Amawongolera ma microwave owonetseredwa kuti asabwerere ku gwero, ndiko kuti, ku radar. Schroeder adapanga equation ya masamu kuti awerengere kuchuluka kwa kunyezimira kwa cheza kuchokera pagawo lathyathyathya la katatu. Kutengera zomwe apezazi, wotsogolera kafukufuku wa Lockheed, Dick Scherrer, adapanga mawonekedwe oyamba a ndegeyo, yokhala ndi mapiko akulu opindika komanso fuselage yamitundu yambiri.
