Oceanus (Uranus orbiter)

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OCEANUS (Origins and Composition of the Exoplanet Analog Uranus System)

Uranus2.jpg

Uranus, an ice giant planet, was photographed in real color by Voyager 2 in January 1986
Mission type Reconnaissance
Operator NASA/JPL
Mission duration ≥1.5 years [1]
Spacecraft properties
Launch mass ≈3,939 kg
BOL mass ≈2,000 kg [1]
Dry mass ≈1,110 kg
Power 290 kW [1]
Start of mission
Launch date 2030 (suggested)
Rocket Atlas V 511 or SLS
Uranus orbiter
Orbital insertion 2041
Orbits ≥14 (proposed) [1]

OCEANUS (Origins and Composition of the Exoplanet Analog Uranus System) is a mission concept conceived in 2016 and presented in 2017 as a potential future contestant as a New Frontiers program mission to the planet Uranus. [2] [1] The concept was developed by the Astronautical engineering students of Purdue University during the 2017 NASA/JPL Planetary Science Summer School. OCEANUS is an orbiter, which would enable a detailed study of the structure of the planet's magnetosphere and interior structure that would not possible with a flyby mission. [2]

The New Frontiers program is a series of space exploration missions being conducted by NASA with the purpose of researching several of the Solar System bodies, including the dwarf planet Pluto.

Uranus Seventh planet from the Sun in the Solar System

Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. Uranus is similar in composition to Neptune, and both have bulk chemical compositions which differ from that of the larger gas giants Jupiter and Saturn. For this reason, scientists often classify Uranus and Neptune as "ice giants" to distinguish them from the gas giants. Uranus' atmosphere is similar to Jupiter's and Saturn's in its primary composition of hydrogen and helium, but it contains more "ices" such as water, ammonia, and methane, along with traces of other hydrocarbons. It is the coldest planetary atmosphere in the Solar System, with a minimum temperature of 49 K, and has a complex, layered cloud structure with water thought to make up the lowest clouds and methane the uppermost layer of clouds. The interior of Uranus is mainly composed of ices and rock.

Purdue University public research university in West Lafayette, Indiana, United States

Purdue University is a public research university in West Lafayette, Indiana, and the flagship campus of the Purdue University system. The university was founded in 1869 after Lafayette businessman John Purdue donated land and money to establish a college of science, technology, and agriculture in his name. The first classes were held on September 16, 1874, with six instructors and 39 students.

Contents

Because of the required technology development and planetary orbital dynamics, the concept suggests a launch in August 2030 on an Atlas V 511 rocket and entering Uranus' orbit in 2041. [1]

Atlas V expendable launch system

Atlas V is an expendable launch system in the Atlas rocket family. It was formerly operated by Lockheed Martin and is now operated by United Launch Alliance (ULA), a joint venture with Boeing. Each Atlas V rocket uses a Russian-built RD-180 engine burning kerosene and liquid oxygen to power its first stage and an American-built RL10 engine burning liquid hydrogen and liquid oxygen to power its Centaur upper stage. The RD-180 engines are provided by RD Amross, while Aerojet Rocketdyne provides both the RL10 engines and the strap-on boosters used in some configurations. The standard payload fairing sizes are 4 or 5 meters in diameter and of various lengths. Fairings sizes as large as 7.2 m in diameter and up to 32.3 m in length have been considered. The rocket is assembled in Decatur, Alabama and Harlingen, Texas.

Overview

Atlas V, proposed for OCEANUS, shown here launching a lunar probe into space Atlas V(401) launches with LRO and LCROSS cropped.jpg
Atlas V, proposed for OCEANUS, shown here launching a lunar probe into space

Ice giant sized planets are the most common type of planet according to Kepler data. The little data available on Uranus, an ice giant planet, come from ground-based observations and the single flyby of the Voyager 2 spacecraft, so its exact composition and structure are essentially unknown, as internal heat flux, and cause of its unique magnetic fields and extreme axial tilt or obliquity, [1] making it a compelling target for exploration according to the Planetary Science Decadal Survey. [2] [3] The primary science objectives of OCEANUS are to study Uranus' interior structure, magnetosphere, and the Uranian atmosphere. [1]

Ice giant giant planet primarily composed of elements heavier than hydrogen and helium

An ice giant is a giant planet composed mainly of elements heavier than hydrogen and helium, such as oxygen, carbon, nitrogen, and sulfur. There are two ice giants in the Solar System: Uranus and Neptune.

<i>Voyager 2</i> Space probe and the second-farthest man-made object from Earth

Voyager 2 is a space probe launched by NASA on August 20, 1977, to study the outer planets. Part of the Voyager program, it was launched 16 days before its twin, Voyager 1, on a trajectory that took longer to reach Jupiter and Saturn but enabled further encounters with Uranus and Neptune. It is the only spacecraft to have visited either of these two ice giant planets.

In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, or, equivalently, the angle between its equatorial plane and orbital plane. It differs from orbital inclination.

The required mission budget is estimated at $1.2 billion. [1] The mission concept has not been formally proposed to NASA's New Frontiers program for assessment and funding. The mission is named after Oceanus, the Greek god of the ocean; he was son of the Greek god Uranus. [4]

Oceanus Ancient Greek god of the sea

Oceanus, also known as Ogenus or Ogen, was a divine figure in classical antiquity, believed by the ancient Greeks and Romans to be the divine personification of the sea, an enormous river encircling the world.

Uranus (mythology) primordial Greek deity, god of the Sky

Uranus was the primal Greek god personifying the sky and one of the Greek primordial deities. Uranus is associated with the Roman god Caelus. In Ancient Greek literature, Uranus or Father Sky was the son and husband of Gaia, Mother Earth. According to Hesiod's Theogony, Uranus was conceived by Gaia alone, but other sources cite Aether as his father. Uranus and Gaia were the parents of the first generation of Titans, and the ancestors of most of the Greek gods, but no cult addressed directly to Uranus survived into Classical times, and Uranus does not appear among the usual themes of Greek painted pottery. Elemental Earth, Sky, and Styx might be joined, however, in a solemn invocation in Homeric epic.

Power and propulsion

Since Uranus is extremely distant to the Sun (20 AU), relying in solar power is not possible past Jupiter, so the orbiter is proposed to be powered by three multi-mission radioisotope thermoelectric generators (MMRTG), [2] [1] a type of radioisotope thermoelectric generator. There is enough plutonium available to NASA to fuel only three more MMRTG like the one used by the Curiosity rover. [5] [6] One is already committed to the Mars 2020 rover. [5] The other two have not been assigned to any specific mission or program, [6] and could be available by late 2021. [5] The trajectory to Uranus would require a Jupiter gravity assist, but such alignments are calculated to be rare in the 2020s and 2030s, so the launch windows will be scant and narrow. [2] If launching in 2030, reaching Uranus would occur 11 years later, in 2041, [1] and it would use two bipropellant engines for orbital insertion. [1] Alternatively, the SLS rocket could be used for a shorter cruise time, [7] but it would result in a faster approach velocity, making orbit insertion more challenging, especially since the density of Uranus' atmosphere is unknown to plan for safe aerobraking. [6]

Astronomical unit mean distance between Earth and the Sun, common length reference in astronomy

The astronomical unit is a unit of length, roughly the distance from Earth to the Sun. However, that distance varies as Earth orbits the Sun, from a maximum (aphelion) to a minimum (perihelion) and back again once a year. Originally conceived as the average of Earth's aphelion and perihelion, since 2012 it has been defined as exactly 149597870700 metres, or about 150 million kilometres. The astronomical unit is used primarily for measuring distances within the Solar System or around other stars. It is also a fundamental component in the definition of another unit of astronomical length, the parsec.

Multi-mission radioisotope thermoelectric generator

The multi-mission radioisotope thermoelectric generator (MMRTG) is a type of radioisotope thermoelectric generator developed for NASA space missions such as the Mars Science Laboratory (MSL), under the jurisdiction of the United States Department of Energy's Office of Space and Defense Power Systems within the Office of Nuclear Energy. The MMRTG was developed by an industry team of Aerojet Rocketdyne and Teledyne Energy Systems.

Radioisotope thermoelectric generator electrical generator that converts heat released by radioactive decay into electricity by the Seebeck effect

A radioisotope thermoelectric generator is an electrical generator that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive material into electricity by the Seebeck effect. This generator has no moving parts.

The orbital configuration and distance would require two Venus gravity assists (in November 2032 and August 2034) and one Earth gravity assist (October 2034) along with the use of solar-electric propulsion within 1.5 AU. [1] The science phase would take place from a highly elliptical orbit and perform a minimum of 14 orbits. [1]

Gravity assist space maneuver

In orbital mechanics and aerospace engineering, a gravitational slingshot, gravity assist maneuver, or swing-by is the use of the relative movement and gravity of a planet or other astronomical object to alter the path and speed of a spacecraft, typically to save propellant and reduce expense.

Ion thruster Propulsion method for spacecraft

An ion thruster or ion drive is a form of electric propulsion used for spacecraft propulsion. It creates thrust by accelerating cations by utilizing electricity. The term refers strictly to gridded electrostatic ion thrusters, and is often incorrectly loosely applied to all electric propulsion systems including electromagnetic plasma thrusters.

Payload

The 12.5 kg scientific payload would include instruments for a detailed study of the magnetic fields and to determine Uranus' global gravity field: [2] [1]

See also

Uranus mission proposals

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References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Bramson, A. M; Elder, C. M; Blum, L. W; Chilton, H. T; Chopra, A; Chu, C; Das, A; Delgado, A; Fulton, J; Jozwiak, L; Khayat, A; Landis, M. E; Molaro, J. L; Slipski, M; Valencia, S; Watkins, J; Young, C. L; Budney, C. J; Mitchell, K. L (2017). "OCEANUS: A Uranus Orbiter Concept Study from the 2016 NASA/JPL Planetary Science Summer School". 48th Lunar and Planetary Science Conference. 48: 1583. Bibcode:2017LPI....48.1583B.
  2. 1 2 3 4 5 6 7 Elder, C. M; Bramson, A. M; Blum, L. W; Chilton, H. T; Chopra, A; Chu, C; Das, A; Davis, A; Delgado, A; Fulton, J; Jozwiak, L; Khayat, A; Landis, M. E; Molaro, J. L; Slipski, M; Valencia, S; Watkins, J; Young, C. L; Budney, C. J; Mitchell, K. L (2017). "New Frontiers-Class Missions to the Ice Giants". Planetary Science Vision 2050 Workshop. 1989: 8147. Bibcode:2017LPICo1989.8147E.
  3. ↑ "Lean U.S. missions to Mars, Jupiter moon recommended". 7 March 2011. Reuters. 8 March 2011.
  4. ↑ OCEANUS: A Concept Study (PDF) - poster. 2017.
  5. 1 2 3 Leone, Dan (11 March 2015). "U.S. Plutonium Stockpile Good for Two More Nuclear Batteries after Mars 2020". Space News. Retrieved 12 March 2015.
  6. 1 2 3 Moore, Trent (12 March 2015). "NASA can only make three more batteries like the one that powers the Mars rover". Blastr. Retrieved 13 March 2015.
  7. ↑ Mansell, J; Kolencherry, N; Hughes, K; Arora, A; Chye, H.S; Coleman, K; Elliott, J; Fulton, S; Hobar, N; Libben, B; Lu, Y; Millane, J; Mudek, A; Podesta, L; Pouplin, J; Shibata, E; Smith, G; Tackett, B; Ukai, T; Witsberger, P; Saikia, S (2017). "Oceanus: A multi-spacecraft flagship mission concept to explore Saturn and Uranus". Advances in Space Research. 59 (9): 2407–33. Bibcode:2017AdSpR..59.2407M. doi:10.1016/j.asr.2017.02.012.

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