On June 21 Isaev proposed a new design using compressed air instead of a pump to force propellant to the engine. The next day, Operation Barbarossa brought the Soviet Union into World War II, and the rocket-powered interceptor suddenly became important.Bereznyak and Isaev met with Andrea Kostikov, the head of RNII. Dushkin was not happy about the idea of bypassing his fuel pump design, but they backed the plan and cosigned a letter that was eventually shown to Joseph Stalin. After giving a report at the Kremlin, they were ordered to build the aircraft and were given only 35 days to do so. The official order was dated August 1, but work began in late July. The engineers were given leave to visit their families, and then literally lived at the factory until the aircraft was finished.The new design was called “BI” for Blizhnii Istrebitel (meaning close-range-fighter), but the letters were also understood by everyone else to stand of its inventors: Bereznyak and Isaev. The original plan was to include 4 machine guns was replaced by a design with a pair of 20 mm (or 0.79 in) ShVAK cannon. The new aircraft was a low-wing monoplane 6.4 m (or 21 ft) long, with a wingspan of 6.5 m (or 21 ft) and an estimated takeoff mass of 1,650 kg (or 3,640 lb) (or dry mass of 805 kg (1,775 lb) and had a maximum propellant load of 705 kg (1,554 lb) letting it fly for a total of 2 minutes. In October, both OKB-293 and RNII were evacuated to the Urals, along with most of Moscow’s war industry. Bolkhovitnov’s team was stationed in Bilimbay, with a dynamometer cradle to hold the BI-1 during engine testing. A new test pilot, Grigory Yakovlevich Bakhchivandzhi, was assigned to the team. Dushkin was increasingly absorbed by other work, including RNII’s own rocket aircraft project, the Kosikov-302. He assigned his engineer Arvid V. Pallo to oversee the installation and testing of the rocket engine. Nitric acid presented a constant problem, corroding parts…
wiki link: https://en.wikipedia.org/wiki/Bereznyak-Isayev_BI-1