Plasma-A Credit - © Mark Wade

In 1987 two experimental Plazma-A satellites (Cosmos 1818 and 1867) were launched with new-generation Topaz reactors. The spacecraft used the US-A first generation bus but tested new on-board systems being developed for the US-AM. These included new elements of the orientation system, and ion engines.

Use of a new high radiation-safety orbit was also demonstrated. The Topaz used a new thermo-emission conversion method to convert heat to electricity. This would also power a range of new systems including electrostatic maneuvering engines, ion orientation/stabilization engines, solar sensors, magnetic momentum compensators, multi-channel wave devices, and special plasma weapons to provide a defense against anti-satellite weapons. The Plazma-A satellites carried instruments to map the magnetic field of the earth, with an eye toward developing a magnetic navigation system. Topaz provided over 10 kW of power and had long endurance and storage in a radiation-safe orbit. A follow-on Plazma-2 would have been equipped with the even safer Topaz-2. The spacecraft would be orbited by a Tsyklon 2 booster and have a mass of 3550 kg. Despite these encouraging tests, the US-AM nuclear-powered component of the Pirs system was abandoned on the instructions of Gorbachev in 1988 due to continued reliability problems and international incidents when the reactor cores of the satellites crashed to the earth.

Mass: 3,550 kg (7,820 lb).

• 1974 December 31 - Plasma-A satellite authorised. -
  Ministry of General Machine Building (MOM) Decree 314 'On development of the Topaz-1 thermionic nuclear reactor for Plasma-A spacecraft' was issued.

• 1976 December 10 - Plasma-A construction authorised. -
  Military-Industrial Commission (VPK) Decree 342 'On development of the Topaz-1 thermionic nuclear reactor for Plasma-A spacecraft' was issued.

• 1987 February 1 - Cosmos 1818 - Program: RORSAT. Launch Site: Baikonur. Launch Complex: LC90/19. Launch Vehicle: Tsiklon. Mass: 3,800 kg (8,300 lb). Perigee: 774 km (480 mi). Apogee: 803 km (498 mi). Inclination: 65.00 deg. Period: 100.60 min.
  Test of new Topaz reactor, new systems, and ion engines aboard US-AM bus.

• 1987 July 10 - Cosmos 1867 - Program: RORSAT. Launch Site: Baikonur. Launch Complex: LC90/19. Launch Vehicle: Tsiklon. Mass: 3,800 kg (8,300 lb). Perigee: 776 km (482 mi). Apogee: 803 km (498 mi). Inclination: 65.00 deg. Period: 100.70 min.
  Test of new Topaz reactor, new systems, and ion engines aboard US-AM bus - Tested Plasma-2 SPT electric engine.