The Systems Nuclear Auxiliary POWER (SNAP) program was a program of experimental
radioisotope thermoelectric generator
A radioisotope thermoelectric generator (RTG, RITEG), sometimes referred to as a radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioacti ...
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeeding t ...
radioactive decay
Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...
to produce electricity.
SNAP-1
SNAP-1 was a test platform that was never deployed, using
cerium-144
Naturally occurring cerium (58Ce) is composed of 4 stable isotopes: 136Ce, 138Ce, 140Ce, and 142Ce, with 140Ce being the most abundant (88.48% natural abundance) and the only one theoretically stable; 136Ce, 138Ce, and 142Ce are predicted to under ...
mercury
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
as the
heat transfer fluid
In fluid thermodynamics, a heat transfer fluid is a gas or liquid that takes part in heat transfer by serving as an intermediary in cooling on one side of a process, transporting and storing thermal energy, and heating on another side of a proc ...
SNAP-7A D and F 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 electricity using (about four kilograms) of strontium-90 as SrTiO3. These were very large units, weighing between .
SNAP-9
After SNAP-3 on Transit 4A/B, SNAP-9A units served aboard many of the Transit satellite series. In April 1964 a SNAP-9A failed to achieve orbit and disintegrated, dispersing roughly of
plutonium-238
Plutonium-238 (238Pu or Pu-238) is a fissile, radioactive isotope of plutonium that has a half-life of 87.7 years.
Plutonium-238 is a very powerful alpha emitter; as alpha particles are easily blocked, this makes the plutonium-238 isotope suitab ...
over all continents. Most plutonium fell in the southern hemisphere. Estimated 6300 GBq or 2100 person-Sv of radiation was released.
SNAP-11
SNAP-11 was an experimental RTG intended to power the
Surveyor
Surveying or land surveying is the technique, profession, art, and science of determining the terrestrial two-dimensional or three-dimensional positions of points and the distances and angles between them. A land surveying professional is ca ...
probes during the lunar night. The
curium-242
Curium (96Cm) is an artificial element with an atomic number of 96. Because it is an artificial element, a standard atomic weight cannot be given, and it has no stable isotopes. The first isotope synthesized was 242Cm in 1944, which has 146 neutr ...
RTGs would have produced 25 watts of electricity using 900 watts of thermal energy for 130 days. The hot junction temperature was , the cold junction temperature was . They had a liquid
NaK
In data networking, telecommunications, and computer buses, an acknowledgment (ACK) is a signal that is passed between communicating processes, computers, or devices to signify acknowledgment, or receipt of message, as part of a communicatio ...
In general, the SNAP 11 fuel block is a cylindrical multi-material unit which occupies the internal volume of the generator. TZM (molybdenum alloy) fuel capsule, fueled with
curium-242
Curium (96Cm) is an artificial element with an atomic number of 96. Because it is an artificial element, a standard atomic weight cannot be given, and it has no stable isotopes. The first isotope synthesized was 242Cm in 1944, which has 146 neutr ...
(Cm2O3 in an iridium matrix) is located in the center of the fuel block. Capsule is surrounded by a platinum sphere, approximately inches in diameter, which provides shielding and acts as an energy absorber for impact considerations. This assembly is enclosed in graphite and beryllium sub-assemblies to provide the proper thermal distribution and ablative protection.
SNAP-19
SNAP-19(B) was developed for the Nimbus-B satellite by the Nuclear Division of the Martin-Marietta Company (now Teledyne Energy Systems). Fueled with plutonium-238, two parallel lead telluride thermocouple generators produced an initial maximum of approximately 30 watts of electricity. Nimbus 3 used a SNAP-19B with the recovered fuel from the Nimbus-B1 attempt.
SNAP-19's powered the
Pioneer 10
''Pioneer 10'' (originally designated Pioneer F) is an American space probe, launched in 1972 and weighing , that completed the first mission to the planet Jupiter. Thereafter, ''Pioneer 10'' became the first of five artificial objects to ach ...
and
Pioneer 11
''Pioneer 11'' (also known as ''Pioneer G'') is a robotic space probe launched by NASA on April 5, 1973, to study the asteroid belt, the environment around Jupiter and Saturn, solar winds, and cosmic rays. It was the first probe to encounter ...
missions. They used n-type 2N-PbTe and p-type TAGS-85 thermoelectric elements.
Modified SNAP-19B's were used for the
Viking 1
''Viking 1'' was the first of two spacecraft, along with ''Viking 2'', each consisting of an orbiter and a lander, sent to Mars as part of NASA's Viking program. The lander touched down on Mars on July 20, 1976, the first successful Mars land ...
and
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. ''Viking 2'' was operational on Mars for sols ( days; '). The ''Vik ...
landers.
A SNAP-19C was used to power a telemetry array at Nanda Devi in
Uttarakhand
Uttarakhand ( , or ; , ), also known as Uttaranchal ( ; the official name until 2007), is a state in the northern part of India. It is often referred to as the "Devbhumi" (literally 'Land of the Gods') due to its religious significance and ...
for a CIA operation to track Chinese missile launches.
SNAP-21 & 23
SNAP-21 and SNAP-23 were designed for underwater use and used strontium-90 as the radioactive source, encapsulated as either
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. It is a stron ...
or
strontium titanate
Strontium titanate is an oxide of strontium and titanium with the chemical formula Sr Ti O3. At room temperature, it is a centrosymmetric paraelectric material with a perovskite structure. At low temperatures it approaches a ferroelectric phase ...
. They produced about ten watts of electricity.
SNAP-27
Five SNAP-27 units provided electric power for the
Apollo Lunar Surface Experiments Package
The Apollo Lunar Surface Experiments Package (ALSEP) comprised a set of scientific instruments placed by the astronauts at the landing site of each of the five Apollo missions to land on the Moon following Apollo 11 (Apollos 12, 14, 15, 16, ...
12, 14, 15, 16, and 17. The SNAP-27 power supply weighed about 20 kilograms, was 46 cm long and 40.6 cm in diameter. It consisted of a central fuel capsule surrounded by concentric rings of thermocouples. Outside of the thermocouples was a set of fins to provide for heat rejection from the cold side of the thermocouple. Each of the SNAP devices produced approximately 75 W of electrical power at 30 VDC. The energy source for each device was a rod of plutonium-238 providing a thermal power of approximately 1250 W. This fuel capsule, containing of
plutonium-238
Plutonium-238 (238Pu or Pu-238) is a fissile, radioactive isotope of plutonium that has a half-life of 87.7 years.
Plutonium-238 is a very powerful alpha emitter; as alpha particles are easily blocked, this makes the plutonium-238 isotope suitab ...
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 Apollo Lunar Module (LM ), originally designated the Lunar Excursion Module (LEM), was the lunar lander spacecraft that was flown between lunar orbit and the Moon's surface during the United States' Apollo program. It was the first crewed ...
. 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
moonquake
A quake is the result when the surface of a planet, moon or star begins to shake, usually as the consequence of a sudden release of energy transmitted as seismic waves, and potentially with great violence.
The types of quakes include:
Earthquak ...
s 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 75 watts.
The fuel cask from the SNAP-27 unit carried by the
Apollo 13
Apollo 13 (April 1117, 1970) was the seventh crewed mission in the Apollo space program and the third meant to land on the Moon. The craft was launched from Kennedy Space Center on April 11, 1970, but the lunar landing was aborted aft ...
mission currently lies in of water at the bottom of the Tonga Trench in the
Pacific Ocean
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...
. This mission failed to land on the moon, and the
lunar module
The Apollo Lunar Module (LM ), originally designated the Lunar Excursion Module (LEM), was the lunar lander spacecraft that was flown between lunar orbit and the Moon's surface during the United States' Apollo program. It was the first crewed ...
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 intended for space use, the even numbered SNAPs were developed for the U.S. government by the Atomics International division of
North American Aviation
North American Aviation (NAA) was a major American aerospace manufacturer that designed and built several notable aircraft and spacecraft. Its products included: the T-6 Texan trainer, the P-51 Mustang fighter, the B-25 Mitchell bomber, the F ...
.
SNAP Experimental Reactor (SER)
The 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 Uranium zirconium hydride (UZrH), a combination of uranium hydride and zirconium(II) hydride, is used as the fuel in TRIGA reactors. UZrH fuel is used in most research reactors at universities and has a large, prompt negative fuel temperature coeffi ...
NaK
In data networking, telecommunications, and computer buses, an acknowledgment (ACK) is a signal that is passed between communicating processes, computers, or devices to signify acknowledgment, or receipt of message, as part of a communicatio ...
) 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 (Systems for Nuclear Auxiliary Power, aka Snapshot for Space Nuclear Auxiliary Power Shot, also known as OPS 4682) was a US experimental nuclear powered satellite launched into space in 1965 as part of the SNAPSHOT program.lithium hydride. The reactor was at the small end and the crew capsule/payload was in the shadow of the large end.
Studies were performed on the reactor, individual components and the support system. Atomics International, a division of North American Aviation did the development and testing work. The SNAP-2 Shield Development unit was responsible for developing the radiation shield. Creating the shield meant melting lithium hydride and casting it into the form required. The form was a big truncated cone. Molten lithium hydride had to be poured into the casting mold a little at a time otherwise it would crack as it cooled and solidified. Cracks in the shield material would be fatal to any space crew or payload depending on it because it would allow radiation to stream through to the crew/payload compartment. As the material cooled, it would form kind of a hollowed vortex in the middle. The development engineers had to create ways to fill the vortex while maintaining the shield's integrity. And, in doing all this they had to keep in mind that they were working with a material that could be explosively unstable in a moist oxygen rich environment. Analysis also revealed that under thermal and radiation gradients, the lithium hydride could disassociate and hydrogen ions could migrate through the shield. This would produce variations of shielding efficacy and could subject the payloads to intense radiation. Efforts were made to mitigate these effects.
The SNAP 2DR used a similar reactor reflector moderator device as the
SNAP-10A
SNAP-10A (Systems for Nuclear Auxiliary Power, aka Snapshot for Space Nuclear Auxiliary Power Shot, also known as OPS 4682) was a US experimental nuclear powered satellite launched into space in 1965 as part of the SNAPSHOT program.National Aeronautics and Space Administration
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeeding th ...
. 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 commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
rankine Rankine is a surname. Notable people with the surname include:
* William Rankine (1820–1872), Scottish engineer and physicist
** Rankine body an elliptical shape of significance in fluid dynamics, named for Rankine
** Rankine scale, an absolute-te ...
power conversion system. The electrical generating system for the SNAP 8 reactors was supplied by Aerojet General.
The SNAP 8 Experimental Reactor was a 600 kWt reactor that was tested from 1963 to 1965.
The SNAP 8 Developmental Reactor had a reactor core measuring , contained a total of of fuel, had a power rating of 1 MWt. The reactor was tested in 1969 at the Santa Susana Field Laboratory.
SNAP-10A
The SNAP-10A was a space-qualified nuclear reactor power system launched into space in 1965 under the SNAPSHOT program.SNAPSHOT NASA Glenn Research Center, March 20, 2007. Retrieved 3 April 2019. Gunther's Space Page. Retrieved 3 April 2019. It was built as a research project for the Air Force, to demonstrate the capability to generate higher power than RTGs. The reactor employed two moveable beryllium reflectors for control, and generated 35 kWt at beginning of life. The system generated electricity by circulating NaK around lead tellurium thermocouples. To mitigate launch hazards, the reactor was not started until it reached a safe orbit.
SNAP-10A was launched into Earth orbit in April 1965, and used to power an Agena-D research satellite, built by Lockheed/Martin. The system produced 500W of electrical power during an abbreviated 43-day flight test. The reactor was prematurely shut down by a faulty command receiver. It is predicted to remain in orbit for 4,000 years.
See also
*
List of nuclear power systems in space
This list of nuclear power systems in space includes nuclear power systems that were flown to space, or at least launched in an attempt to reach space. Such used nuclear power systems include:
* radioisotope heater units (RHU) (usually produce he ...
*
Nuclear power in space
Nuclear power in space is the use of nuclear power in outer space, typically either small fission systems or radioactive decay for electricity or heat. Another use is for scientific observation, as in a Mössbauer spectrometer. The most common ...