- The MiG-9, which was known internally in OKB as the I-307 was powered by the same two RD-21 engines, like the previous versions. The armament was rearranged in order to solve the gun gas ingestion problem with the N37 mounted on the starboard side of the fuselage and the two NS-23 on the port side, well aft so the gun barrels did not protrude beyond the air intake. Therefore, the cockpit had to be moved forward slightly giving pilot that way better field of view when landing. Internal fuel tanks were reduced to five, but the overall fuel capacity of the fighter remained the same.It flew for the first time in July 1947 but factory test flights weren't completed until early 1948. It failed the state acceptance trials in spite of a top speed of 965Km/h (600mph) at 5000m (16000ft) as apparently the engines continued to flame out if they were run at low rpm at altitudes above 8000m (26000ft) and the mounts for the cannons weren't fully developed and the workmanship of the pressurized cockpit was low. However, the real reason was that the MiG-15, which already under development, was far superior.
- There was a, two-seat trainer version, called I-301T internally and izdeliye FT, which was a converted regular MiG-9 one. Fuel capacity was reduced by a third in order to make room for the second cockpit. Dual controls were fitted as well as an intercom to allow instructor and student to communicate in the air. Each cockpit had ejectable seats designed after the ones used in the German Heinkel He.162 Salamander. It was delivered on 17th January 1947 but it wasn't fully tested until 5th April. Ejection seats weren't tested in mid-air as they required extensive ground-training to ensure proper operation of the seat. It was tested by the state in June, but it was rejected due to poor visibility from the rear cockpit. A second aircraft was made on 15th July, which had better visibility from the rear cockpit as it had removed the original bulletproof windscreen with a larger glass plate, reshaping that way canopy's side panels and removing the partition between cockpits. It was fitted with wing airbrakes and two 260 litres (57 imp. gal - 69 US gal) drop tanks under wingtips. This version passed state acceptance trials in late 1947 and was recommended fro production with the designation of MiG-9UTI. Ejection seats were extensively tested all through 1948 but, as the aircraft was considered obsolete, there was not point in developing a trainer version. Sixty of them were ordered together with two-hundred and fifty regular fighter versions in 1948 but as the aircraft was deemed obsolete, the order was cancelled as the MiG-15 was already pushing forward.
- The MiG-9FK was a modified version made in 1949 to serve as a testbed for the Raduga KS-1 Komet air-launched anti-shipping cruise missile. This version featured a second unpressurized cockpit in line with the trailing edge of the wing for the guidance system operator. It was fitted with two radars, a KM-1 target illumination radar and a prominent bullet-shaped fairing above the air intake plus an aft-looking radar mounted on a cigar-shaped fairing at the top of the vertical-stabilizer. This system was intended to test the mid-course guidance system of the launching aircraft and the guidance systems of the missile. Signals from the KM-1 radar were received in small bullet-shaped fairings on the leading edges of the wings. This aircraft served in this role for four years, until the Raduga KS-1 passed its state acceptance trials in 1952-1953.
- The MiG-9FP was a regular MiG-9 with the N-37 cannon moved to the port side in order to solve the gas ingestion problem, but it seems that it wasn't successful.
- The MiG-9FL was a version powered by two Lyulka TR-1 Turbojet engines instead of the RD-20. These engines, the TR-1, had a power of 1500kgf (15KN, 3300lbf) and were the first jet ones to be natively developed in the USSR. Armament was rearranged as well, with the 23mm cannons moved to each of them to a side of the fuselage and the N-37 still in the centre of the air intake. It had the ammunition for the N-37 increased to 45 rounds. It was intended to have a pressurized cockpit and a reduced overall weight of 4500Kg (9900lb). However, as the engine was not fully developed by 1948 and the MiG-15 was already pushing forward, the variant was discarded.
Sources:
1. https://en.wikipedia.org/wiki/Mikoyan-Gurevich_MiG-9
2. Salamander Books - The Complete Book of Fighters
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