Snapshot (satellite)
| Snapshot (OPS 4682) | |
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| Country: | United States |
| Operator: | United States Department of the Air Force |
| COSPAR-ID : | 1965-027A |
| Mission dates | |
| Dimensions: | 440 kg (without Agena level) |
| Begin: | April 4, 1965 |
| Starting place: |
Vandenberg AFB , launch pad PALC-2-4 |
| Launcher: | Atlas-SLV3 Agena-D |
| Orbit data | |
| Rotation time : | 111.5 min |
| Orbit inclination : | 90.2 ° |
| Apogee height : | 1325 km |
| Perigee height : | 1279 km |
Snapshot (military name OPS 4682 ) is an experimental technology satellite launched by the United States Air Force on April 4, 1965, with the aim of testing a nuclear reactor as an energy source for satellites. The on-board SNAP-10A reactor was the first nuclear reactor in space. This mission also brought the first American ion engine into orbit.
development
A compact nuclear reactor suitable for space was developed as part of the US Atomic Energy Commission's Systems for Nuclear Auxiliary Power Program (SNAP) . In addition to nuclear reactors, radionuclide batteries were also developed in this program . Even serial numbered SNAP models were reactors and odd numbered models were radionuclide batteries.
The main contractor for the reactor development was Atomics International , then a division of North American Aviation . System development and reactor testing took place in dedicated facilities at the Santa Susana Field Laboratory in Ventura County , California.
The company had previously built and tested experimental compact reactors in the SNAP program - including the SNAP Experimental Reactor (SER) , SNAP-2 , SNAP-8 Developmental Reactor (SNAP8-DR) and SNAP-8 Experimental Reactor (SNAP-8ER) versions . However, these were purely experimental and not yet suitable for use on a satellite. In addition, Atomics International built the Sodium Reactor Experiment, the first nuclear power plant to supply electricity to the public electricity network.
In addition to the development of the space-compatible reactor itself, it was also necessary to develop new safety guidelines for handling such a device. This was done as part of the Aerospace Nuclear Safety Program , which examined the hazards associated with the construction, launch, operation and disposal of the SNAP systems. Safety was the responsibility of Atomics International, while Sandia National Laboratories performed an independent review and various tests. Before the start was allowed, these guidelines had to demonstrate that under no circumstances could the reactor pose a serious risk.
construction
The satellite snapshot consists of the SNAP-10A reactor, which is permanently connected to the Agena upper stage of the launcher. The Agena stage took over the attitude control for the satellite after it was launched into earth orbit, so that the payload does not need its own systems.
reactor
The SNAP-10A reactor consisted of three main components:
- a compact reactor
- a controllable neutron reflector
- a heat transfer and energy conversion system
The reactor core had a mass of 290 kg with a height of 39.62 cm and a width of 22.40 cm. It contained 37 fuel rods made of uranium-zirconium hydride (UZrH), which served both with enriched uranium- 235 ( 235 U) as a nuclear fuel and as a moderator . The thermal power of the reactor was 30 kW .
To achieve the criticality and to control the output of the reactor, neutron reflectors made of beryllium were arranged around the reactor core. Some of these reflectors were mounted in a fixed position, but four semi-cylindrical beryllium masses were rotatably mounted so that the amount of reflected neutrons could be changed by rotating the reflectors. At the start, the reflectors were in an open position, so that the arrangement was subcritical. Only in the orbit did the control reflectors turn into a position that put the reactor core into criticality.
For safety reasons, the reflectors could be separated from the reactor core in order to put it in a permanently subcritical state. For this purpose, a retaining strap was cut with an explosive bolt and the reflector elements were pushed off by springs. Without the presence of the reflectors, the reactor core can no longer sustain chain reactions.
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A eutectic alloy of sodium and potassium served as coolant , which was pumped through the reactor core by means of a thermoelectric pump . The hot liquid was passed through tubes in the conical structure below the reactor, where the heat was transferred to radiators via thermocouples . A voltage was generated in the thermocouples due to the temperature gradient between the hot coolant lines and space. The output power of the thermocouples was 0.5 kW.
Ion propulsion
As a secondary experiment was on the satellites cesium - ion engine , whose power was carried out by the current produced in the reactor. The ion thruster was the first example of an electric drive to be tested in orbit.
The power supply for the ion thruster delivered a voltage of 4500 V from a battery at a current of 80 mA for a period of one hour. The battery then had to be recharged over 15 hours using the SNAP-10A reactor, which required 0.1 kW. Ionized cesium , which was electrically accelerated, served as the reaction mass of the engine . The engine neutralizer consisted of a wire mesh coated with barium oxide . The engine reached a thrust of 8.5 mN.
Mission description
Snapshot was launched into low polar orbit on April 4, 1965 on an Atlas SLV3 Agena-D rocket from Vandenberg Air Force Base . Also on board was a small secondary payload , the geodetic satellite SECOR 4 , which was disconnected after reaching earth orbit. Snapshot itself was integrated with the Agena stage and thus remained intentionally linked to the rocket stage. Snapshot successfully entered an orbit with an apogee of 1325 km, a perigee of 1279 km, and an orbit inclination of 90.2 °.
The ion thruster had to be switched off permanently after only one hour of operation, as there were numerous voltage flashovers that severely disrupted the satellite's attitude control system.
After 43 days in orbit, a voltage regulator in the satellite electronics failed , causing the reactor to shut down, which meant the end of the snapshot mission.
Even if the fundamental suitability of a nuclear reactor for supplying energy to a satellite was demonstrated, the mission goal of operating the reactor for at least a year was thus unsuccessful. Testing the ion thruster was also a failure.
aftermath
Snapshot's orbit is 1,300 km high, so the satellite will remain in orbit for about 4,000 years. This means that there is no short-term risk from the re-entry of the radioactive reactor.
In November 1979 it was observed that around 50 objects had detached themselves from the satellite snapshot. The reason for this is unknown, but a collision with space debris cannot be ruled out. Radioactive material may also have been released.
A nuclear reactor was used here for the first and last time as an energy supply by the USA. The Soviet Union continued to use reactors in numerous satellites under the RORSAT program until 1988 , with several incidents in which radioactive substances were released into the environment. Nuclear reactors no longer play a practical role in both civil and military space travel in the USA, even if further, unrealized projects with this energy source were considered. However, nuclear energy continues to play an important role as an energy supplier for space probes into the outer solar system beyond Jupiter's orbit and in the radiation belts that destroy Jupiter's solar cells , for example in the form of the radionuclide battery or the radionuclide heating element , since there the solar radiation is too low or not possible for photovoltaic energy supply . For terrestrial satellites and many space probes, however, solar cells are a risk-free, economical and reliable technology.
literature
- GL Schmidt: SNAP 10A Test Program , Rockwell International, Canoga Park , California, DCN: SP-100-XT-0002, September 1988
- Susan Voss: SNAP Reactor Overview , US Air Force Weapons Laboratory, Kirtland AFB, New Mexico, AFWL-TN-84-14, August 1984
- Gary L. Bennett: Opening the Final Frontier (PDF; 2.3 MB) , American Institute of Aeronautics and Astronautics, 2006, p. 17ff.
- DW Staub: SNAP 10 Summary Report. Atomics International Division of North American Aviation, Inc., Canoga Park, California March 25, 1967, NAA-SR-12073
Web links
- Department of Energy: SNAP Overview ( Memento from October 15, 2011 in the Internet Archive )
- Department of Energy: SNAP-10A Video ( Memento October 15, 2011 in the Internet Archive )
- Department of Energy: Snapshot Video ( Memento from October 15, 2011 in the Internet Archive )
- NASA Glenn Research Center: Snapshot
- Gunter's Space Page: Snapshot
Individual evidence
- ^ Gunter's Space Page: List of all satellites with nuclear energy supply
- ^ A b C. Stokely, E. Stansbury: Identification of a debris cloud from the nuclear powered SNAPSHOT satellite with Haystack radar measurements , Advances in Space Research 41 (7): pp. 1004-1009, 2008
- ↑ Susan Voss: SNAP Reactor Overview , US Air Force Weapons Laboratory, Kirtland AFB, New Mexico, AFWL-TN-84-14, August 1984
- ^ GL Schmidt: SNAP 10A Test Program , Rockwell International, Canoga Park, California, DCN: SP-100-XT-0002, September 1988
- ↑ Department of Energy: SNAP Overview ( Memento of the original from February 15, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ^ Gary L. Bennett: Opening the Final Frontier (PDF; 2.3 MB) , American Institute of Aeronautics and Astronautics, 2006, pp. 17ff.
- ↑ a b NASA Glenn Research Center: Snapshot
- ^ A b David S. F Portree, Joseph P. Loftus, Jr .: Orbital Debris: A Chronology. , TP-1999-208856, NASA, January 1999
- ↑ DW Staub: SNAP 10 Summary Report. Atomics International Division of North American Aviation, Inc., Canoga Park, California March 25, 1967, NAA-SR-12073
- ↑ The radioisotope elements on board space probes
