Aleksei Mikhailovich Isayev was born in 1908 in Saint Petersburg, the son of an assistant professor at the University. In 1925 he entered the Moscow Mining Institute, and in 1932 began work at the Zaporozhtal Ferrous Metals Factory in Nizhiy Tagil. He discovered a love of aviation, becoming Director of Aviation Factory 22 on 18 August 1934. In October 1934 he began work at the V F Bolkhovitnov design bureau, where his first assignment was to design landing gear for the DB-A long range bomber. This was followed by work on the S fast bomber and I aircraft.
He was then assigned to work with A Ya Bereznyako on development of the first rocket-powered fighter, the BI. In October 1941, 40 days after work began, the Bolkhovitnov factory had to be moved to the Urals in the face of the German army advance into Russia. It was not until 15 May 1942 that G Ya Bakhchivangi made the first flight in the BI.
To replace the troublesome Dushkin D-1-A-1100 engine, Bolkhovitnov asked Isayev to head a bureau team to develop a better replacement. From that point on Isayev worked only on rocket engines. The work began from zero - there was no technical literature on the subject at the design bureau, and no engineers with rocket experience. Design materials were finally sent from the 'sharaga' (prison engineering group) Special Section No. 4 of the NKVD in Kazan, where Glushko was working. This allowed Isayev to develop the RD-1 engine which powered the BI-1 on two flights with pilot B N Kudrin.
From 3 July to 8 September 1945 Isayev was sent to Germany to acquire Nazi rocket technology. In July 1947 he was named head of his own design section, OKB-2 of the NII-1 Scientific Research Institute 1 of the Ministry of Aviation, dedicated solely to rocket technology. This became Section 9 of NII-88 in May 1949. In this period Isayev successfully developed the U-2000 engine for a surface-to-air missile and the U-4000-2 for an air-sea missile. An attempt was made to develop an 8 tonne thrust engine for the 201 missile. But Lavochkin knew from the first test attempt the idea was not achievable. The final design used four 2 tonne thrust chambers.
In 1952 Isayev developed the first practical anti-oscillation baffle for engine chamber of the Krest missile. This brought him to the attention of Korolev, who had him design the S2.253 engine for the R-11 (Scud) missile. In 1954 he was assigned the pump-fed engine for the second stage of the V-75 SAM and the 4 chamber S2.1100 engine for the Burya booster units. In December 1958 OKB-3 (D D Sevruk) was dissolved and consolidated into Isayev's OKB-2.
Isayev's work on space engines began with the retrofire engine TDU for the Vostok manned spacecraft. It was developed in 18 months and flew 104 times on Vostok, Voskhod, and Zenit spacecraft. The KTDU restartable engine was developed for use in unmanned lunar and planetary probes, and manoeuvrable manned spacecraft. These engines had to provide engine pulses ranging from a fraction of a second to many minutes. The latest KTDU-80 is used in the Soyuz TM and Progress M spacecraft.
For the N1-L3 lunar project Isayev developed the KTDU for the LOK lunar orbiter and the first Lox/LH2 engine for the L3M project. In 1967 OKB-2 was renamed KBKhM. Isayev died on 25 June 1971. He was remembered as an engineer of talent and knowledge, possessing phenomenal energy and initiative. He was a good leader of his staff and got along well with the other chief designers. His greatest innovations came in the field of submarine-launched ballistic missile propulsion, where he achieved submerging of the engines in the propellant tanks in order to minimise the length of the missile.