ard ▁( or ▁En te ) ▁with ▁both ▁skin ▁and ▁structure ▁made ▁of ▁metal . ▁This ▁was ▁constructed ▁with ▁assistance ▁from ▁Hugo ▁J unk ers ▁who ▁had ▁previously ▁shown ▁little ▁interest ▁in ▁av iation . ▁Both ▁were ▁profess ors ▁at ▁the ▁University ▁of ▁A achen . ▁The ▁first ▁flight ▁was ▁made ▁on ▁May ▁ 2 3 , ▁ 1 9 1 2 ▁with ▁Robert ▁G s ell ▁at ▁the ▁controls . ▁ ▁During ▁the ▁Naz i ▁regime ▁Re iss ner ▁was ▁able ▁to ▁work ▁in ▁the ▁aircraft ▁industry ▁although ▁he ▁did ▁not ▁have ▁an ▁A ry an ▁certificate . ▁In ▁ 1 9 3 5 ▁he ▁lost ▁his ▁post ▁at ▁the ▁Techn ical ▁University ▁of ▁Berlin ▁due ▁to ▁his ▁Jewish ▁ancest ry , ▁and ▁in ▁ 1 9 3 8 ▁he ▁em igr ated ▁to ▁the ▁United ▁States . ▁He ▁taught ▁at ▁the ▁Illinois ▁Institute ▁of ▁Technology ▁( 1 9 3 8 – 4 4 ) ▁and ▁the ▁Poly techn ic ▁Institute ▁of ▁Brook lyn ▁( 1 9 4 4 – 5 4 ). ▁ ▁Cur iously , ▁it ▁was ▁this ▁engineer , ▁rather ▁than ▁a ▁phys ic ist ▁or ▁math ematic ian , ▁who ▁first ▁solved ▁Ein stein ' s ▁equation ▁for ▁the ▁metric ▁of ▁a ▁charged ▁point ▁mass . ▁His ▁closed - form ▁solution , ▁redis cover ed ▁by ▁several ▁other ▁phys ic ists ▁within ▁the ▁next ▁few ▁years , ▁is ▁now ▁called ▁the ▁Re iss ner – N ord ström ▁metric . ▁ ▁Eric ▁Re iss ner ▁( Max ▁Er