Systems Nuclear Auxiliary Power Program
Encyclopedia
The Systems Nuclear Auxiliary Power (SNAP) program was a program of experimental radioisotope thermoelectric generator
s (RTGs) and space nuclear reactor
s flown during the 1960s by NASA
.
-144 in a Rankine cycle
, with mercury
as the heat transfer fluid; it operated for 2500 hours successfully.
SNAP-3 : In 1961, the first RTG used in a space mission was launched aboard a U.S. Navy Transit 4A and 4B navigation satellites
. The electrical power output of this RTG, which was called (SNAP-3), was a mere 2.7 watts.
SNAP-7 was designed for marine applications such as lighthouses and buoys; at least six units were deployed in the mid-1960s, with names SNAP-7A through SNAP-7F. SNAP-7D produced thirty watts of electric power using 225 kilocurie
s (about four kilograms) of strontium-90
as SrTiO3. These were very large units, weighing between 1870 and 6000 pounds.
After SNAP-3 on Transit 4A/B, SNAP-9A units served aboard many of the Transit satellite
series. On April 24, 1964 a SNAP-9A failed to achieve orbit and disintegrated, dispersing 2.1 pounds of Plutonium-238 over all continents, and leading to NASA's increased development of solar photovoltaic energy technology.
SNAP-11, an experimental RTG intended to power the Surveyor
probes during the lunar night.
SNAP-19s powered Pioneer 10
and Pioneer 11
missions as well as the Viking 1
and Viking 2
landers.
SNAP-21 and SNAP-23 were designed for underwater use and used strontium-90
as the radioactive source, encapsulated as either strontium oxide
or strontium titanate
. They produced about ten watts.
, 14
, 15
, 16
, and 17
. The fuel capsule, containing 3.8 kilograms (8.4 pounds) of plutonium-238
in oxide form (44,500 Ci
or 1.65 PBq), was carried to the Moon in a separate fuel cask attached to the side of the Lunar Module. The fuel cask provided thermal insulation and added structural support to the fuel capsule. On the Moon, the Lunar Module pilot removed the fuel capsule from the cask and inserted it in the RTG.
These stations transmitted information about moonquakes and meteor impacts, lunar magnetic and gravitational fields, the Moon's internal temperature, and the Moon's atmosphere for several years after the missions. After ten years, a SNAP-27 still produced more than 90% of its initial output of 70 watts.
The fuel cask from the SNAP-27 unit carried by the Apollo 13
mission currently lies in 20,000 feet (6,500 m) of water at the bottom of the Tonga Trench
in the Pacific Ocean
. This mission failed to land on the moon, and the lunar module carrying its generator burnt up during re-entry into the Earth's atmosphere, with the trajectory arranged so that the cask would land in the trench. The cask survived re-entry, as it was designed to do, and no release of plutonium has been detected. The corrosion resistant materials of the capsule are expected to contain it for 10 half-lives (870 years).
division of North American Aviation
.
SNAP Experimental Reactor (SER) was the first reactor to be built by the specifications established for space satellite applications. The SER used uranium zirconium hydride as the fuel and eutectic sodium-potassium alloy (NaK
) as the coolant and operated at approximately 50 kW thermal. The system did not have a power conversion but used a secondary heat air blast system to dissipate the heat to the atmosphere. The SER used a similar reactor reflector moderator device as the SNAP-10A
but with only one reflector. Criticality was achieved in September 1959 with final shutdown completed in December 1961. The project was considered a success. It gave continued confidence in the development of the SNAP Program and it also led to in depth research and component development.
SNAP-2 Developmental Reactor was the second SNAP reactor built. This device used Uranium-zirconium hydride fuel and had a design reactor power of 55 kWt. It was the first model to use a flight control assembly and was tested from April 1961 to December 1962. Studies were performed on the reactor, individual components and the support system. The SNAP 2DR used a similar reactor reflector moderator device as the SNAP-10A
but with two movable and internal fixed reflectors. The system was designed so that the reactor could be integrated with a Mercury- Rankine cycle to generate 3.5 KW of electricity.
SNAP-8 reactors were designed, constructed and operated by Atomics International under contract with the National Aeronautics and Space Administration. Two SNAP-8 reactors were produced: The SNAP 8 Experimental Reactor and the SNAP 8 Developmental Reactor. Both SNAP 8 reactors used the same highly enriched uranium zirconium hydride fuel as the SNAP 2 and SNAP 10A reactors. The SNAP 8 design included primary and secondary NaK loops to transfer heat to the mercury
rankine
power conversion system. The electrical generating system for the SNAP 8 reactors was supplied by Aerojet General.
The SNAP 8 Experimental Reactor was a 600kWt reactor that was tested from 1963 to 1965. The SNAP 8 Developmental Reactor had a reactor core measuring 9.5 inches wide by 33 inches long, contained a total of 18 lbs of fuel, had a power rating of 1 MWt. The reactor was tested in 1969 at the Santa Susana Field Laboratory
.
The SNAP-10A
was a nuclear qualified flight system which was launched into earth orbit. The reactor produced 500 W of electrical power during an abbreviated 43-day flight test.
Radioisotope thermoelectric generator
A radioisotope thermoelectric generator is an electrical generator that obtains its power from radioactive decay. In such a device, the heat released by the decay of a suitable radioactive material is converted into electricity by the Seebeck effect using an array of thermocouples.RTGs can be...
s (RTGs) and space nuclear reactor
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...
s flown during the 1960s by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
.
Odd-numbered SNAPs: radioisotope thermoelectric generators
SNAP-1 was not deployed, but was designed to use ceriumCerium
Cerium is a chemical element with the symbol Ce and atomic number 58. It is a soft, silvery, ductile metal which easily oxidizes in air. Cerium was named after the dwarf planet . Cerium is the most abundant of the rare earth elements, making up about 0.0046% of the Earth's crust by weight...
-144 in a Rankine cycle
Rankine cycle
The Rankine cycle is a cycle that converts heat into work. The heat is supplied externally to a closed loop, which usually uses water. This cycle generates about 90% of all electric power used throughout the world, including virtually all solar thermal, biomass, coal and nuclear power plants. It is...
, with mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
as the heat transfer fluid; it operated for 2500 hours successfully.
SNAP-3 : In 1961, the first RTG used in a space mission was launched aboard a U.S. Navy Transit 4A and 4B navigation satellites
Transit (satellite)
The TRANSIT system, also known as NAVSAT , was the first satellite navigation system to be used operationally. The system was primarily used by the U.S...
. The electrical power output of this RTG, which was called (SNAP-3), was a mere 2.7 watts.
SNAP-7 was designed for marine applications such as lighthouses and buoys; at least six units were deployed in the mid-1960s, with names SNAP-7A through SNAP-7F. SNAP-7D produced thirty watts of electric power using 225 kilocurie
Curie
The curie is a unit of radioactivity, defined asThis is roughly the activity of 1 gram of the radium isotope 226Ra, a substance studied by the pioneers of radiology, Marie and Pierre Curie, for whom the unit was named. In addition to the curie, activity can be measured using an SI derived unit,...
s (about four kilograms) of strontium-90
Strontium-90
Strontium-90 is a radioactive isotope of strontium, with a half-life of 28.8 years.-Radioactivity:Natural strontium is nonradioactive and nontoxic, but 90Sr is a radioactivity hazard...
as SrTiO3. These were very large units, weighing between 1870 and 6000 pounds.
After SNAP-3 on Transit 4A/B, SNAP-9A units served aboard many of the Transit satellite
Transit (satellite)
The TRANSIT system, also known as NAVSAT , was the first satellite navigation system to be used operationally. The system was primarily used by the U.S...
series. On April 24, 1964 a SNAP-9A failed to achieve orbit and disintegrated, dispersing 2.1 pounds of Plutonium-238 over all continents, and leading to NASA's increased development of solar photovoltaic energy technology.
SNAP-11, an experimental RTG intended to power the Surveyor
Surveyor program
The Surveyor Program was a NASA program that, from 1966 through 1968, sent seven robotic spacecraft to the surface of the Moon. Its primary goal was to demonstrate the feasibility of soft landings on the Moon...
probes during the lunar night.
SNAP-19s powered Pioneer 10
Pioneer 10
Pioneer 10 is a 258-kilogram robotic space probe that completed the first interplanetary mission to Jupiter, and became the first spacecraft to achieve escape velocity from the Solar System. The project was managed by the NASA Ames Research Center and the contract for the construction of the...
and Pioneer 11
Pioneer 11
Pioneer 11 is a 259-kilogram robotic space probe launched by NASA on April 6, 1973 to study the asteroid belt, the environment around Jupiter and Saturn, solar wind, cosmic rays, and eventually the far reaches of the solar system and heliosphere...
missions as well as the Viking 1
Viking 1
Viking 1 was the first of two spacecraft sent to Mars as part of NASA's Viking program. It was the first spacecraft to successfully land on Mars and perform its mission, and until May 19, 2010 held the record for the second longest Mars surface mission of 6 years and 116 days .- Mission :Following...
and Viking 2
Viking 2
The Viking 2 mission was part of the American Viking program to Mars, and consisted of an orbiter and a lander essentially identical to that of the Viking 1 mission. The Viking 2 lander operated on the surface for 1,281 Mars days and was turned off on 11 April 1980 when its batteries failed...
landers.
SNAP-21 and SNAP-23 were designed for underwater use and used strontium-90
Strontium-90
Strontium-90 is a radioactive isotope of strontium, with a half-life of 28.8 years.-Radioactivity:Natural strontium is nonradioactive and nontoxic, but 90Sr is a radioactivity hazard...
as the radioactive source, encapsulated as either strontium oxide
Strontium oxide
Strontium oxide or strontia, SrO, is formed when strontium reacts with oxygen. Burning strontium in air results in a mixture of strontium oxide and strontium nitride. It also forms from the decomposition of strontium carbonate SrCO3...
or strontium titanate
Strontium titanate
Strontium titanate is an oxide of strontium and titanium with the chemical formula SrTiO3. At room temperature, it is a centrosymmetric paraelectric material with a perovskite structure...
. They produced about ten watts.
SNAP-27
Five SNAP-27 units provided electric power for the Apollo Lunar Surface Experiment Packages (ALSEP) left on the Moon by Apollo 12Apollo 12
Apollo 12 was the sixth manned flight in the American Apollo program and the second to land on the Moon . It was launched on November 14, 1969 from the Kennedy Space Center, Florida, four months after Apollo 11. Mission commander Charles "Pete" Conrad and Lunar Module Pilot Alan L...
, 14
Apollo 14
Apollo 14 was the eighth manned mission in the American Apollo program, and the third to land on the Moon. It was the last of the "H missions", targeted landings with two-day stays on the Moon with two lunar EVAs, or moonwalks....
, 15
Apollo 15
Apollo 15 was the ninth manned mission in the American Apollo space program, the fourth to land on the Moon and the eighth successful manned mission. It was the first of what were termed "J missions", long duration stays on the Moon with a greater focus on science than had been possible on previous...
, 16
Apollo 16
Young and Duke served as the backup crew for Apollo 13; Mattingly was slated to be the Apollo 13 command module pilot until being pulled from the mission due to his exposure to rubella through Duke.-Backup crew:...
, and 17
Apollo 17
Apollo 17 was the eleventh and final manned mission in the American Apollo space program. Launched at 12:33 a.m. EST on December 7, 1972, with a three-member crew consisting of Commander Eugene Cernan, Command Module Pilot Ronald Evans, and Lunar Module Pilot Harrison Schmitt, Apollo 17 remains the...
. The fuel capsule, containing 3.8 kilograms (8.4 pounds) of plutonium-238
Plutonium-238
-External links:**...
in oxide form (44,500 Ci
Curie
The curie is a unit of radioactivity, defined asThis is roughly the activity of 1 gram of the radium isotope 226Ra, a substance studied by the pioneers of radiology, Marie and Pierre Curie, for whom the unit was named. In addition to the curie, activity can be measured using an SI derived unit,...
or 1.65 PBq), was carried to the Moon in a separate fuel cask attached to the side of the Lunar Module. The fuel cask provided thermal insulation and added structural support to the fuel capsule. On the Moon, the Lunar Module pilot removed the fuel capsule from the cask and inserted it in the RTG.
These stations transmitted information about moonquakes and meteor impacts, lunar magnetic and gravitational fields, the Moon's internal temperature, and the Moon's atmosphere for several years after the missions. After ten years, a SNAP-27 still produced more than 90% of its initial output of 70 watts.
The fuel cask from the SNAP-27 unit carried by the Apollo 13
Apollo 13
Apollo 13 was the seventh manned mission in the American Apollo space program and the third intended to land on the Moon. The craft was launched on April 11, 1970, at 13:13 CST. The landing was aborted after an oxygen tank exploded two days later, crippling the service module upon which the Command...
mission currently lies in 20,000 feet (6,500 m) of water at the bottom of the Tonga Trench
Tonga Trench
The Tonga Trench is located in the South Pacific Ocean and is deep at its deepest point, known as the Horizon Deep.The Tonga Trench is a convergent plate boundary. The trench lies at the northern end of the Kermadec-Tonga Subduction Zone, an active subduction zone where the Pacific Plate is being...
in the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
. This mission failed to land on the moon, and the lunar module carrying its generator burnt up during re-entry into the Earth's atmosphere, with the trajectory arranged so that the cask would land in the trench. The cask survived re-entry, as it was designed to do, and no release of plutonium has been detected. The corrosion resistant materials of the capsule are expected to contain it for 10 half-lives (870 years).
Even-numbered SNAPs: compact nuclear reactors
A series of compact nuclear reactors primarily developed for the U.S. Government by the Atomics InternationalAtomics International
Atomics International was a division of the North American Aviation company which engaged principally in the early development of nuclear technology and nuclear reactors for both commercial and government applications...
division of North American Aviation
North American Aviation
North American Aviation was a major US aerospace manufacturer, responsible for a number of historic aircraft, including the T-6 Texan trainer, the P-51 Mustang fighter, the B-25 Mitchell bomber, the F-86 Sabre jet fighter, the X-15 rocket plane, and the XB-70, as well as Apollo Command and Service...
.
SNAP Experimental Reactor (SER) was the first reactor to be built by the specifications established for space satellite applications. The SER used uranium zirconium hydride as the fuel and eutectic sodium-potassium alloy (NaK
NaK
NaK, or sodium-potassium alloy, an alloy, of potassium , and sodium , is usually liquid at room temperature. Various commercial grades are available. NaK is highly reactive with water and may catch fire when exposed to air, so must be handled with special precautions...
) as the coolant and operated at approximately 50 kW thermal. The system did not have a power conversion but used a secondary heat air blast system to dissipate the heat to the atmosphere. The SER used a similar reactor reflector moderator device as the SNAP-10A
SNAP-10A
SNAP-10A was the first and so far only known launch of a U.S. nuclear reactor into space . The Systems Nuclear Auxiliary Power Program reactor was developed under the SNAPSHOT program overseen by the U.S...
but with only one reflector. Criticality was achieved in September 1959 with final shutdown completed in December 1961. The project was considered a success. It gave continued confidence in the development of the SNAP Program and it also led to in depth research and component development.
SNAP-2 Developmental Reactor was the second SNAP reactor built. This device used Uranium-zirconium hydride fuel and had a design reactor power of 55 kWt. It was the first model to use a flight control assembly and was tested from April 1961 to December 1962. Studies were performed on the reactor, individual components and the support system. The SNAP 2DR used a similar reactor reflector moderator device as the SNAP-10A
SNAP-10A
SNAP-10A was the first and so far only known launch of a U.S. nuclear reactor into space . The Systems Nuclear Auxiliary Power Program reactor was developed under the SNAPSHOT program overseen by the U.S...
but with two movable and internal fixed reflectors. The system was designed so that the reactor could be integrated with a Mercury- Rankine cycle to generate 3.5 KW of electricity.
SNAP-8 reactors were designed, constructed and operated by Atomics International under contract with the National Aeronautics and Space Administration. Two SNAP-8 reactors were produced: The SNAP 8 Experimental Reactor and the SNAP 8 Developmental Reactor. Both SNAP 8 reactors used the same highly enriched uranium zirconium hydride fuel as the SNAP 2 and SNAP 10A reactors. The SNAP 8 design included primary and secondary NaK loops to transfer heat to the mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
rankine
Rankine cycle
The Rankine cycle is a cycle that converts heat into work. The heat is supplied externally to a closed loop, which usually uses water. This cycle generates about 90% of all electric power used throughout the world, including virtually all solar thermal, biomass, coal and nuclear power plants. It is...
power conversion system. The electrical generating system for the SNAP 8 reactors was supplied by Aerojet General.
The SNAP 8 Experimental Reactor was a 600kWt reactor that was tested from 1963 to 1965. The SNAP 8 Developmental Reactor had a reactor core measuring 9.5 inches wide by 33 inches long, contained a total of 18 lbs of fuel, had a power rating of 1 MWt. The reactor was tested in 1969 at the Santa Susana Field Laboratory
Santa Susana Field Laboratory
The Santa Susana Field Laboratory is a complex of industrial research and development facilities located on a 2,668 acre portion of the Southern California Simi Hills in Simi Valley, California, used mainly for the testing and development of Liquid-propellant rocket engines for the United States...
.
The SNAP-10A
SNAP-10A
SNAP-10A was the first and so far only known launch of a U.S. nuclear reactor into space . The Systems Nuclear Auxiliary Power Program reactor was developed under the SNAPSHOT program overseen by the U.S...
was a nuclear qualified flight system which was launched into earth orbit. The reactor produced 500 W of electrical power during an abbreviated 43-day flight test.