 The Tupolev Tu @-@ 73 jet @-@ engined bomber project was suffering delays in early 1947 and Tupolev suggested re @-@ <unk> the Tu @-@ 2 medium bomber with imported British Rolls @-@ Royce Nene jet engines to produce a jet bomber as quickly as possible . Design work began well before official approval was received on 31 May 1947 for one Tu @-@ 2S to be converted in the <unk> 's workshop and another five to be converted at <unk> ( Factory ) Nr. 23 , but construction of the prototype had already begun in early May under the bureau designation Tu @-@ 77 . 
