RORSAT

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RORSAT ( R adar O cean R econnaissance SAT ELLITE ; German radar-based satellite to monitor the oceans ) is the western name of the Soviet satellite series Uprawljajemij Sputnik Aktiwnij (US-A or US-AM, GRAU index of the complex: 17K114, the of the satellite 17F16). These satellites were launched between 1967 and 1988 to monitor NATO and merchant ships with active radar. RORSATs were - like the other military satellites - carried under the name Kosmos . They were brought into orbit with Zyklon 2 rockets.

Nuclear reactors for power supply

For the search radar to work effectively, a low orbit had to be chosen for the RORSATs . Due to the high energy requirements of the radar, solar cells could not be used to power the satellite. Due to their size, they would have led to great friction losses in the atmosphere , the resistance of which still plays a role at this relatively low altitude. Thus the altitude of the orbit would have decreased rapidly. Hence, all operational RORSATs contributed nuclear reactors of the type BES-5 , with 235 U were operated. Normally, the satellite reactor modules were detached at the end of their life and flew into a higher orbit (a so-called "elimination orbit") on their own. However, there have been a few incidents where radioactive material was released into the atmosphere. The first prototypes of the RORSAT series did not contain a reactor, but were operated with batteries, which however only had a service life of a few days.

Although most of the reactor cores successfully reached high orbits, these orbits are not final. If no further measures are taken, the highly radioactive objects will return to the earth's atmosphere after a few hundred years; by then, however, the radioactivity will have dropped.

The RORSATs are considered to be the main source of space debris at an altitude of around 950 kilometers above the earth. By design, the satellite emitted her coolant, a eutectic sodium - potassium - alloy ( NaK ), during the separation of the reactor core into orbit. It is estimated that there will continue to be on the order of 10,000 drops (about 5 mm to a maximum of 55 mm in diameter) over the next few decades.

Since the metal coolant was irradiated with neutrons from the nuclear reactor, it contains small amounts of the radioactive argon -39, which has a half-life of 269 years.

Technical specifications

The satellites have a mass of around 3.8 t (launch mass 4.3 t), a diameter of 1.3 m and a length of around 10 m. Two large elongated antennas are attached to each side of the satellite. The fuel section for the reactor (mass 53 kg, 0.6 m length and 0.2 m diameter) consists of 37 cylindrical fuel elements with a total of 31.1 kg uranium fuel, which is enriched to 90% 235 U.

Accidents

RORSAT false start, April 25, 1973

The start failed and the reactor crashed into the Pacific Ocean north of Japan. The radiation was detected by a US measuring aircraft.

Cosmos 954

The reactor core could not be launched into high orbit at the end of its life. Radioactive material re-entered the atmosphere on January 24, 1978, leaving a trail that contaminated an area of ​​124,000 square kilometers of Canada's Northwest Territories with radioactive material.

Cosmos 1402

The end of 1982 could not be reached. The reactor core was separated from the rest of the satellite and was the last piece of the satellite to return to Earth. It crashed into the South Atlantic on February 7, 1983.

Cosmos 1818

The satellite, also called “Plasma-A”, was used (like Kosmos 1867) to test the new Topas-1 reactor type, which with a mass of 320 kg delivered 5-10 kW electrical power and contained 12 kg of 235 U. It was started on February 2, 1987, but switched off again after 142 days. Since July 2008 the satellite has been disintegrating into parts (30 so far) that are slowly spreading along the orbit.

Cosmos 1900

The primary system failed while attempting to shoot the reactor core into its final orbit. However, the reserve system shot the core into an orbit 80 kilometers below the planned one.

Start list

Start date Surname Remarks
December 28, 1965 Cosmos 102 Test satellite
July 20, 1966 Cosmos 125 Test satellite
December 27, 1967 Cosmos 198
March 22, 1968 Cosmos 209
3rd October 1970 Cosmos 367
April 1, 1971 Cosmos 402
December 25, 1971 Cosmos 469
August 21, 1972 Cosmos 516
April 25, 1973 False start
December 24th 1973 Cosmos 626
May 15, 1974 Cosmos 651
17th May 1974 Cosmos 654
April 2nd, 1975 Cosmos 723
April 7th 1975 Cosmos 724
December 12th 1975 Cosmos 785
2nd July 1976 Cosmos 838
17th October 1976 Cosmos 860
October 21, 1976 Cosmos 861
November 26, 1976 Cosmos 868
September 16, 1977 Cosmos 952
18th September 1977 Cosmos 954
April 29, 1980 Cosmos 1176
March 5th 1981 Cosmos 1249
April 21, 1981 Cosmos 1266
August 24, 1981 Cosmos 1299
May 14, 1982 Cosmos 1365
June 1, 1982 Cosmos 1372
August 30, 1982 Cosmos 1402
2nd October 1982 Cosmos 1412
June 29, 1984 Cosmos 1579
October 31, 1984 Cosmos 1607
August 1, 1985 Cosmos 1670
August 24, 1985 Cosmos 1677
March 21, 1986 Cosmos 1736
August 20, 1986 Cosmos 1771
2nd February 1987 Cosmos 1818 Test satellite with Topas reactor
June 19, 1987 Cosmos 1860
July 10, 1987 Cosmos 1867 Test satellite with Topas reactor
December 12, 1987 Cosmos 1900
March 14, 1988 Cosmos 1932

Web links

Individual evidence

  1. ↑ US-A on Gunter's Space Page, accessed December 18, 2010
  2. ↑ Carsten Wiedemann, Eduard Gamper, Andre Horstmann, Vitali Braun, Enrico Stoll: The Contribution of NaK Droplets to the Space Debris Environment , accessed on November 11, 2018
  3. ^ Globalsecurity.org: RORSAT
  4. ↑ US-A in the Encyclopedia Astronautica (English)
  5. ↑ Russian atomic satellite crumbles in space . Russia News, January 2009