Zephyr (rover)
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''Zephyr'' is a concept of a robotic
Venus Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...
rover for a mission called Venus Landsailing Rover. This mission concept would place a rover on the surface of Venus that would be propelled by the force of the wind. The rover would be launched together with a Venus orbiter that would be a communications relay and perform remote atmospheric studies. The rover would be designed to operate on the surface of Venus for 50 Earth days, and navigate sandy plains bathed in heat and dense
sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...
clouds under very high atmospheric pressure. The rover can move in any direction, regardless of wind direction. ''Zephyr'' would sail up to 15 minutes per day to reach its next target, where it would park using a combination of brakes and feathering the wingsail while it performs its science activities. The rover would carry a science payload of , including a robotic arm. The overall mission architecture aims to achieve telerobotic capability, with a 4-minute delay in radio communication. The principal investigator is
Geoffrey Landis Geoffrey Alan Landis (; born May 28, 1955) is an American aerospace engineer and author, working for the National Aeronautics and Space Administration (NASA) on planetary exploration, interstellar propulsion, solar power and photovoltaics. He h ...
of NASA's
Glenn Research Center NASA John H. Glenn Research Center at Lewis Field is a NASA center within the cities of Brook Park, Ohio, Brook Park and Cleveland between Cleveland Hopkins International Airport and the Rocky River Reservation of Cleveland Metroparks, with a s ...
in Cleveland, Ohio.NASA's Plan To Put a Landsail Rover on Venus.
Jon M. Chang, ''ABC News.'' 26 August 2013. When the most critical hardware becomes available and is tested, Landis intends to propose the mission to NASA's
Discovery program The Discovery Program is a series of Solar System exploration missions funded by the U.S. National Aeronautics and Space Administration (NASA) through its Planetary Missions Program Office. The cost of each mission is capped at a lower level t ...
to compete for funding and a launch intended for 2039.
rover Rover may refer to: People Name * Constance Rover (1910–2005), English historian * Jolanda de Rover (born 1963), Dutch swimmer * Rover Thomas (c. 1920–1998), Indigenous Australian artist Stage name * Rover (musician), French singer-songw ...
propelled by a rigid
wingsail A wingsail, twin-skin sail or double skin sail is a variable-Camber (aerodynamics), camber aerodynamic structure that is fitted to a marine vessel in place of conventional sails. Wingsails are analogous to Wing, airplane wings, except that they ...
, inspired on the
landsailing Land sailing, also known as sand yachting, land yachting or dirtboating, entails overland travel with a sail-powered vehicle, similar to sailing on water. Originally, a form of transportation or recreation, it has evolved primarily into a racin ...
vehicles. The vehicle has only two moving parts: the sail, and the steering front wheel. The mission concept is named Venus Landsailing Rover, and the rover is called ''Zephyr'', after the Greek god of the west wind,
Zephyrus In Greek mythology and religion, Zephyrus () (), also spelled in English as Zephyr (), is the god and personification of the West wind, one of the several wind gods, the Anemoi. The son of Eos (the goddess of the dawn) and Astraeus, Zephyrus is t ...
. For simplicity, the rover's wingsail is actually rigid, like a vertical wing with solar cells on its surface. Although some technology development is needed to bring the high-temperature electronics to operational readiness, the study showed that such a mobility approach is feasible, and no major difficulties are seen. The aimed rover's design lifetime is 50 days. Given the extreme environmental conditions at the surface of Venus, all previous landers and atmospheric probes operated for a few hours at most, so the Glenn Research Center team plans to use materials and electronics developed to withstand not just the extreme pressure, corrosive atmosphere and heat, but also operate with minimum solar power and without a cooling system, which reduces the landing mass significantly. The temperature at the surface is 740  K (467 °C, 872 °F), and the pressure is 93 
bar Bar or BAR may refer to: Food and drink * Bar (establishment), selling alcoholic beverages * Candy bar ** Chocolate bar * Protein bar Science and technology * Bar (river morphology), a deposit of sediment * Bar (tropical cyclone), a laye ...
(9.3 
MPa MPA or mPa may refer to: Academia Academic degrees * Master of Performing Arts * Master of Professional Accountancy * Master of Public Administration * Master of Public Affairs Schools * Mesa Preparatory Academy * Morgan Park Academy * M ...
), roughly the pressure found underwater on Earth. For the purposes of propulsion, surface wind velocities of at least and up to are assumed. ''Zephyr'' would sail up to 15 minutes per day to reach its next target. From the images acquired by the Russian
Venera The Venera (, 'Venus') program was a series of space probes developed by the Soviet Union between 1961 and 1984 to gather information about the planet Venus. Thirteen probes successfully entered the Venusian atmosphere, including the two ...
probes, the surface of Venus can be seen to have landscapes of flat, even terrain stretching to the horizon, with rocks at only centimeter scale at their locations, making it possible for
landsailing Land sailing, also known as sand yachting, land yachting or dirtboating, entails overland travel with a sail-powered vehicle, similar to sailing on water. Originally, a form of transportation or recreation, it has evolved primarily into a racin ...
. The largest expected surface irregularities are about in height. The vehicle uses three metallic wheels with cleats, each with a diameter of and wide. Funding from the
NASA Innovative Advanced Concepts The NASA Innovative Advanced Concepts (NIAC), formerly NASA Institute for Advanced Concepts (NIAC), is a NASA program for development of far reaching, long term advanced concepts by "creating breakthroughs, radically better or entirely new aerospa ...
(NIAC) program, is allowing research into developing the needed "Venus-hardened" systems. NASA may also provide some of this equipment to the future Russian
Venera-D Venera-17 or Venera-D (, ) is a proposed Russian space mission to Venus that would include an orbiter and a lander to be launched in 2031. The orbiter's prime objective is to perform observations with the use of a radar. The lander, based on the ...
mission to Venus by providing a long-lived (24 hours) experimental surface station fit on the Russian lander. In 2017, Landis's work was the subject of the book ''Land-Sailing Venus Rover With NASA Inventor Geoffrey Landis'', published by
World Book The ''World Book Encyclopedia'' is an American encyclopedia. ''World Book'' was first published in 1917. Since 1925, a new edition of the encyclopedia has been published annually. Although published online in digital form for a number of years, ...
publishing.Heilman, Richard
"Book spotlights scientist's work on Venus rover"
''Berea News Sun'', Nov. 17 2017. Retrieved Dec, 7, 2017.


Electric power

Previous Venus landers have relied on batteries for electric power, which limits operation to a few hours at most, relying on thermal mass to delay the death of the system due to overheating. The power system for this mission uses sodium–sulfur batteries (NaS) that are re-charged by solar arrays and can function under Venus surface conditions without the need for heavy cooling systems.Landis, G. A. and Harrison, R. (2008) "Batteries for Venus Surface Operation," ''Journal of Propulsion and Power'', Vol. 26, Number 4, 649-654, July/Aug 2010; originally presented as paper AIAA-2008-5796, 6th AIAA International Energy Conversion Engineering Conf., Cleveland OH, July 28–30, 2008. The wingsail and upper deck would be covered with solar panels made of
indium gallium phosphide Indium gallium phosphide (InGaP), also called gallium indium phosphide (GaInP), is a semiconductor composed of indium, gallium and phosphorus. It is used in high-power and high-frequency electronics because of its superior electron velocity with ...
(InGaP, also called GaInP2) because it has been well characterized for use in solar cells, it has a wide enough
band gap In solid-state physics and solid-state chemistry, a band gap, also called a bandgap or energy gap, is an energy range in a solid where no electronic states exist. In graphs of the electronic band structure of solids, the band gap refers to t ...
that it can work at Venus temperature, and responds to light in the band of about 360 to 660 nm. Although the thick cloud layer limits sunlight reaching the surface, there is enough light to use
solar panels A solar panel is a device that converts sunlight into electricity by using photovoltaic (PV) cells. PV cells are made of materials that produce excited electrons when exposed to light. These electrons flow through a circuit and produce direct ...
for low-power demand systems.


Wind force

While the wind speed at the surface of Venus is , at Venus pressure and density (65 kg/m3), even low wind speeds develop significant force.


Wingsail

The propulsion concept is a rigid
wingsail A wingsail, twin-skin sail or double skin sail is a variable-Camber (aerodynamics), camber aerodynamic structure that is fitted to a marine vessel in place of conventional sails. Wingsails are analogous to Wing, airplane wings, except that they ...
, mounted perpendicular to the base that can rotate via an electric motor about its mean aerodynamic center to produce a lift (thrust) vector at any orientation, depending on the direction of the wind. The wing also provides a more stable surface on which to mount the solar cells used to power instruments on the rover. A symmetric flat airfoil is much easier to control at the sacrifice of a small amount of lift. Construction of the wing is standard spar, rib, and skin, using materials appropriate for the corrosive high temperature environment. At wide, the rover is stable on the surface, and the NASA GRC Team estimates that in order to prevent a roll-over caused by wind gusts, the system will incorporate sensors so that a sustained wind gust of or more will be recognized by its meteorology suite, and would give enough time to slack the sail by rotating it to a zero-lift position parallel to the wind. The diameter of the
aeroshell An aeroshell is a rigid heat-shielded shell that helps decelerate and protects a spacecraft vehicle from pressure, heat, and possible debris created by drag during atmospheric entry. Its main components consist of a heat shield (the forebody) an ...
sets the length of the wingsail to , its area at and a height of above the ground. For launch, the wingsail is folded into three sections for storage in the
aeroshell An aeroshell is a rigid heat-shielded shell that helps decelerate and protects a spacecraft vehicle from pressure, heat, and possible debris created by drag during atmospheric entry. Its main components consist of a heat shield (the forebody) an ...
, and it is deployed after the parachute descent and landing on its three wheels.


Science payload

The eyes of the rover would be a mechanically-scanned camera similar to the one used by the
Venera 9 Venera 9 (), manufacturer's designation: 4V-1 No. 660, was a Soviet uncrewed space mission to Venus. It consisted of an orbiter and a lander. It was launched on June 8, 1975, at 02:38:00 UTC and had a mass of . The orbiter was the first sp ...
lander, that would operate without cooling at Venus temperature, , and under Venus illumination conditions and spectrum. The design would use a linear
photodiode A photodiode is a semiconductor diode sensitive to photon radiation, such as visible light, infrared or ultraviolet radiation, X-rays and gamma rays. It produces an electrical current when it absorbs photons. This can be used for detection and me ...
array as the light-sensing element, and except for the
focal plane In Gaussian optics, the cardinal points consist of three pairs of points located on the optical axis of a rotationally symmetric, focal, optical system. These are the '' focal points'', the principal points, and the nodal points; there are two ...
photodiode array, the camera is fabricated with
silicon carbide Silicon carbide (SiC), also known as carborundum (), is a hard chemical compound containing silicon and carbon. A wide bandgap semiconductor, it occurs in nature as the extremely rare mineral moissanite, but has been mass-produced as a powder a ...
electronics. Beside the imaging cameras, the rover would carry approximately of science instruments, including a robotic arm based on the Mars ''Phoenix'' robotic arm, but simplified to a two-joint arm to minimize complexity. This arm would hold several science instruments. The notional science payload includes: *The atmospheric science package: an
anemometer In meteorology, an anemometer () is a device that measures wind speed and direction. It is a common instrument used in weather stations. The earliest known description of an anemometer was by Italian architect and author Leon Battista Alberti ...
(wind speed and direction), a
thermometer A thermometer is a device that measures temperature (the hotness or coldness of an object) or temperature gradient (the rates of change of temperature in space). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb ...
, and a
barometer A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis ...
(pressure sensor). *In-situ mineralogy: These instruments would be fitted to the end of the robotic arm to make contact with the rocks and regolith and determine composition and mineralogy. These instruments include a rock abrasion grinder,
alpha particle X-ray spectrometer :''APXS is also an abbreviation for APache eXtenSion tool, an extension for Apache web servers.'' An alpha particle X-ray spectrometer (APXS) is a spectrometer that analyses the chemical element composition of a sample from scattered alpha parti ...
(APXS) or an Energy-dispersive X-ray spectroscope (EDAX) for composition, and
X-ray diffraction X-ray diffraction is a generic term for phenomena associated with changes in the direction of X-ray beams due to interactions with the electrons around atoms. It occurs due to elastic scattering, when there is no change in the energy of the waves. ...
for mineralogy. In addition to the surface science instruments, the mission may also have science packages that operate during descent, and may also deploy stationary science instruments, such as a
seismometer A seismometer is an instrument that responds to ground displacement and shaking such as caused by quakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The out ...
, that are not carried on the rover. All data would be transmitted to the orbiter with a high-temperature radio, so that the whole system has no cooled parts.


Orbiter

Because of the thick Venus atmosphere, radio signals from the rover would be limited in power and reach, so a relay orbiter needs to be incorporated in the mission architecture. After ''Zephyr'' separation, the orbiter would propulsively brake into a highly eccentric orbit around the planet. This orbit would have a 24 hour period, permitting communication with ''Zephyr'' for 12 to 18 hour during each orbit. When Venus is at its closest to Earth, the communications time-lag from Venus and Earth is approximately four minutes, which is too long to control from Earth in real time, so the rover would be parked most of the time performing observations with the sail slack, while the ground controllers examine the terrain and decide the next target. If selected for funding, the relay orbiter could also host some science instruments.


References

{{Venus spacecraft Missions to Venus Proposed NASA space probes Three-wheeled robots Wind-powered vehicles