Radioactive payload and debris

Radioactive payloads have been a concern for the community ever since radioactive debris decayed on Earth and contaminated entire regions. The first such event was in Jan 1978 when Cosmos 0954 decayed. Since then radioactive debris are closely monitored.

Those nuclear reactors which are to remain in orbit for a hundred years or so also caused problems to scientists. "Nuclear noise" as it is called cause gamma ray disturbances to astronomers. Indeed those reactors interfere periodically with gamma-ray surveys.

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Russian satellites

The Russian Rorsat program is the most important program with nuclear reactor equipped satellites (32 spacecrafts). This engine (named Topol or Topaz) contains 50 kg of uranium and provides about 2000 W.

Two other Russian satellites are known to have a Topaz 1 reactor (also named Buk): Cosmos 1818 (87011A) and Cosmos 1867 (87060A), probably for test missions. This reactor provides around 5-6 kW power. It weighs 1350 kg.

A third engine named Enissei or Topaz 2 was built but has never been launched. It provides 6 kW and weighs 1 ton.

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US satellites

The United States also used nuclear power on space missions. Two types of engines were used:

- Nuclear reactors which produce energy by nuclear fission (space based reactors use Uranium-235).
- RTGs (Radioisotope Thermoelectric Generator) which use the energy of radioactive decay (current SNAPs use Plutonium-238).

The SNAP (Systems for Nuclear Auxiliary Power) series include:

RTG engines	Nuclear reactors	Uncertain
Transit 4A	OPS 4682 also called SNAPSHOT (65027A)	LES 5
Transit 4B		LES 6
Nimbus 3		OPS 0757 also called Tacsat (69013A)
LES 8
LES 9

Other missions required nuclear power such as the Apollo moon missions experiments, the Viking Mars Landers, Pioneer and Voyager missions and the Galileo probe:

LAUNR	Spacecraft	Orbit
69-099	APOLLO 12	Moon
71-008	APOLLO 14	Moon
71-063	APOLLO 15	Moon
72-012A	PIONEER 10	escaped solar system
72-031	APOLLO 16	Moon
72-096	APOLLO 17	Moon
73-019A	PIONEER 11	escaped solar system
75-075	VIKING 1 LANDER	Mars
75-083	VIKING 2 LANDER	Mars
77-076A	VOYAGER 2	escaped solar system
77-084A	VOYAGER 1	escaped solar system
89-084B	GALILEO	Jupiter
90-090B	ULYSSES	Sun
96-068A	PATHFINDER	Mars
97-061A	CASSINI	to Saturn

Pathfinder had RHUs (Radioisotope Heater Units) on the Sojourner rover.

Finally 3 missions failed:
Transit 5BN3 on 21 Apr 1964 aboard Thor Ablestar
Nimbus 3A
Apollo 13 (70029A) on 11 Apr 1970 which decayed on 17 Apr 1970

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