Aerodynamic Braking
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Aerobraking is a
spaceflight Spaceflight (or space flight) is an application of astronautics to fly objects, usually spacecraft, into or through outer space, either with or without humans on board. Most spaceflight is uncrewed and conducted mainly with spacecraft such ...
maneuver that reduces the high point of an
elliptical orbit In astrodynamics or celestial mechanics, an elliptical orbit or eccentric orbit is an orbit with an orbital eccentricity, eccentricity of less than 1; this includes the special case of a circular orbit, with eccentricity equal to 0. Some or ...
(
apoapsis An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...
) by flying the vehicle through the
atmosphere An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...
at the low point of the orbit (
periapsis An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...
). The resulting drag slows the
spacecraft A spacecraft is a vehicle that is designed spaceflight, to fly and operate in outer space. Spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth observation, Weather s ...
. Aerobraking is used when a spacecraft requires a low orbit after arriving at a body with an atmosphere, as it requires less fuel than using
propulsion Propulsion is the generation of force by any combination of pushing or pulling to modify the translational motion of an object, which is typically a rigid body (or an articulated rigid body) but may also concern a fluid. The term is derived from ...
to slow down.


Method

When an interplanetary vehicle arrives at its destination, it must reduce its
velocity Velocity is a measurement of speed in a certain direction of motion. It is a fundamental concept in kinematics, the branch of classical mechanics that describes the motion of physical objects. Velocity is a vector (geometry), vector Physical q ...
to achieve orbit or to land. To reach a low, near-
circular orbit A circular orbit is an orbit with a fixed distance around the barycenter; that is, in the shape of a circle. In this case, not only the distance, but also the speed, angular speed, Potential energy, potential and kinetic energy are constant. T ...
around a body with substantial
gravity In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...
(as is required for many scientific studies), the required velocity changes can be on the order of kilometers per second. Using propulsion, the
rocket equation The classical rocket equation, or ideal rocket equation is a mathematical equation that describes the motion of vehicles that follow the basic principle of a rocket: a device that can apply acceleration to itself using thrust by expelling part o ...
dictates that a large fraction of the spacecraft mass must consist of fuel. This reduces the science payload and/or requires a large and expensive rocket. Provided the target body has an atmosphere, aerobraking can be used to reduce fuel requirements. The use of a relatively small burn allows the spacecraft to enter an elongated
elliptic orbit In astrodynamics or celestial mechanics, an elliptical orbit or eccentric orbit is an orbit with an eccentricity of less than 1; this includes the special case of a circular orbit, with eccentricity equal to 0. Some orbits have been referre ...
. Aerobraking then shortens the orbit into a circle. If the atmosphere is thick enough, a single pass can be sufficient to adjust the orbit. However, aerobraking typically requires multiple orbits higher in the atmosphere. This reduces the effects of
friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Types of friction include dry, fluid, lubricated, skin, and internal -- an incomplete list. The study of t ...
al heating, unpredictable turbulence effects, atmospheric composition, and temperature. Aerobraking done this way allows sufficient time after each pass to measure the velocity change and make corrections for the next pass. Achieving the final orbit may take over six
month A month is a unit of time, used with calendars, that is approximately as long as a natural phase cycle of the Moon; the words ''month'' and ''Moon'' are cognates. The traditional concept of months arose with the cycle of Moon phases; such lunar mo ...
s for
Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...
, and may require hundreds of passes through the atmosphere. After the last pass, if the spacecraft shall stay in orbit, it must be given more
kinetic energy In physics, the kinetic energy of an object is the form of energy that it possesses due to its motion. In classical mechanics, the kinetic energy of a non-rotating object of mass ''m'' traveling at a speed ''v'' is \fracmv^2.Resnick, Rober ...
via rocket engines in order to raise the
periapsis An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...
above the atmosphere. If the craft shall land, it must lose kinetic energy, also via rocket engines. The kinetic energy
dissipated In thermodynamics, dissipation is the result of an irreversible process that affects a thermodynamic system. In a dissipative process, energy (internal, bulk flow kinetic, or system potential) transforms from an initial form to a final form, wher ...
by aerobraking is converted to
heat In thermodynamics, heat is energy in transfer between a thermodynamic system and its surroundings by such mechanisms as thermal conduction, electromagnetic radiation, and friction, which are microscopic in nature, involving sub-atomic, ato ...
, meaning that spacecraft must dissipate this heat. The spacecraft must have sufficient surface area and structural strength to produce and survive the required drag, The temperatures and pressures associated with aerobraking are not as severe as those of
atmospheric reentry Atmospheric entry (sometimes listed as Vimpact or Ventry) is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet, or natural satellite. Atmospheric entry may be ''uncontrolled entry ...
or
aerocapture Aerocapture is an Orbital maneuver, orbital transfer maneuver in which a spacecraft uses aerodynamic drag force from a single pass through a planetary atmosphere to decelerate and achieve orbit insertion. Aerocapture uses a planet's or moon's at ...
. Simulations of the ''
Mars Reconnaissance Orbiter The ''Mars Reconnaissance Orbiter'' (''MRO'') is a spacecraft designed to search for the existence of water on Mars and provide support for missions to Mars, as part of NASA's Mars Exploration Program. It was launched from Cape Canaveral on Au ...
'' aerobraking use a
force In physics, a force is an influence that can cause an Physical object, object to change its velocity unless counterbalanced by other forces. In mechanics, force makes ideas like 'pushing' or 'pulling' mathematically precise. Because the Magnitu ...
limit of 0.35 N per square meter with a spacecraft cross section of about 37 m2, equate to a maximum drag force of about 7.4 N, and a maximum expected
temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...
as 170 °C. The force density (i.e. pressure), roughly 0.2 N per square meter, that was exerted on the ''
Mars Observer The ''Mars Observer'' spacecraft, also known as the ''Mars Geoscience/Climatology Orbiter'', was a Robotic spacecraft, robotic space probe launched by NASA on September 25, 1992, to study the Martian surface, atmosphere, climate and magnetic fie ...
'' during aerobraking is comparable to the aerodynamic resistance of moving at 0.6 m/s (2.16 km/h) at sea level on Earth, approximately the amount experienced when walking slowly. Regarding spacecraft navigation,
Moriba Jah Moriba Kemessia Jah CorrFRSE (born 1971) is an American space scientist and aerospace engineer who describes himself as a "space environmentalist". Jah is adamant finding solution to the accumulating garbage in space. He specializes in orbit de ...
was the first to demonstrate the ability to process Inertial Measurement Unit (IMU) data collected on board the spacecraft, during aerobraking, using an unscented
Kalman Filter In statistics and control theory, Kalman filtering (also known as linear quadratic estimation) is an algorithm that uses a series of measurements observed over time, including statistical noise and other inaccuracies, to produce estimates of unk ...
to statistically infer the spacecraft's trajectory independent of ground-based measurement data. Jah did this using actual IMU data from ''
Mars Odyssey ''2001 Mars Odyssey'' is a robotic spacecraft orbiting the planet Mars. The project was developed by NASA, and contracted out to Lockheed Martin, with an expected cost for the entire mission of US$297 million. Its mission is to use spectro ...
'' and ''
Mars Reconnaissance Orbiter The ''Mars Reconnaissance Orbiter'' (''MRO'') is a spacecraft designed to search for the existence of water on Mars and provide support for missions to Mars, as part of NASA's Mars Exploration Program. It was launched from Cape Canaveral on Au ...
''. Moreover, this was the first use of an unscented
Kalman Filter In statistics and control theory, Kalman filtering (also known as linear quadratic estimation) is an algorithm that uses a series of measurements observed over time, including statistical noise and other inaccuracies, to produce estimates of unk ...
to determine the orbit of an anthropogenic space object about another planet. This method, which could be used to automate aerobraking navigation, is called Inertial Measurements for Aeroassisted Navigation (IMAN) and Jah won a
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
Space Act Award for this work. Many spacecraft use solar panels to power their operations. The panels can be used to refine aerobraking to reduce the number of required orbits. The panels rotate according to an AI-powered algorithm to increase/reduce drag and can reduce arrival times from months to weeks.


Related methods

Aerocapture Aerocapture is an Orbital maneuver, orbital transfer maneuver in which a spacecraft uses aerodynamic drag force from a single pass through a planetary atmosphere to decelerate and achieve orbit insertion. Aerocapture uses a planet's or moon's at ...
is a related but more extreme method in which no initial orbit-injection burn is performed. Instead, the spacecraft plunges deeply into the atmosphere without an initial insertion burn, and emerges from this single pass in the atmosphere with an apoapsis near that of the desired orbit. Several small correction burns are then used to raise the periapsis and perform final adjustments. This method was originally planned for the ''
Mars Odyssey ''2001 Mars Odyssey'' is a robotic spacecraft orbiting the planet Mars. The project was developed by NASA, and contracted out to Lockheed Martin, with an expected cost for the entire mission of US$297 million. Its mission is to use spectro ...
'' orbiter, but the significant design impacts proved too costly. Another related technique is that of
aerogravity assist An aerogravity assist, or AGA, is a theoretical spacecraft maneuver designed to change velocity when arriving at a body with an atmosphere. A pure gravity assist uses only the gravity of a body to change the direction of the spacecraft trajectory. ...
, in which the spacecraft flies through the upper atmosphere and uses
aerodynamic lift When a fluid flows around an object, the fluid exerts a force on the object. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the force paral ...
instead of drag at the point of closest approach. If correctly oriented, this can increase the deflection angle above that of a pure
gravity assist A gravity assist, gravity assist maneuver, swing-by, or generally a gravitational slingshot in orbital mechanics, is a type of spaceflight flyby (spaceflight), flyby which makes use of the relative movement (e.g. orbit around the Sun) and gra ...
, resulting in a larger
delta-v Delta-''v'' (also known as "change in velocity"), symbolized as and pronounced , as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such as launching from or l ...
.


Spacecraft missions

Although the theory of aerobraking is well developed, using the technique is difficult because a very detailed knowledge of the character of the target planet's atmosphere is needed in order to plan the maneuver correctly. Currently, the deceleration is monitored during each maneuver and plans are modified accordingly. Since no spacecraft can yet aerobrake safely on its own, this requires constant attention from both human controllers and the
Deep Space Network The NASA Deep Space Network (DSN) is a worldwide Telecommunications network, network of spacecraft communication ground segment facilities, located in the United States (California), Spain (Madrid), and Australia (Canberra), that supports NASA' ...
. This is particularly true near the end of the process, when the drag passes are relatively close together (only about 2 hours apart for Mars). NASA has used aerobraking four times to modify a spacecraft's orbit to one with lower energy, reduced apoapsis altitude, and smaller orbit. On 19 March 1991, aerobraking was demonstrated by the
Hiten Hiten may refer to: * Hiten (name), Indian given name * Hiten (spacecraft), Japanese lunar probe * Tennin, spiritual being in Japanese Buddhism See also *'' Hi-Ten Bomberman'', 1993 action-maze video game {{disambiguation ...
spacecraft. This was the first aerobraking maneuver by a deep space probe.
Hiten Hiten may refer to: * Hiten (name), Indian given name * Hiten (spacecraft), Japanese lunar probe * Tennin, spiritual being in Japanese Buddhism See also *'' Hi-Ten Bomberman'', 1993 action-maze video game {{disambiguation ...
(a.k.a. MUSES-A) was launched by the
Institute of Space and Astronautical Science , or ISAS, is a Japanese national research organization of astrophysics using rockets, astronomical satellites and interplanetary probes which played a major role in Japan's space development. Established as part of the University of Tokyo ...
(ISAS) of Japan. Hiten flew by the Earth at an altitude of 125.5 km over the Pacific at 11.0 km/s. Atmospheric drag lowered the velocity by 1.712 m/s and the apogee altitude by 8665 km. Another aerobraking maneuver was conducted on 30 March. In May 1993, aerobraking was used during the extended
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 ...
ian mission of the ''Magellan'' spacecraft. It was used to circularize the orbit of the spacecraft in order to increase the precision of the measurement of the
gravity field In physics, a gravitational field or gravitational acceleration field is a vector field used to explain the influences that a body extends into the space around itself. A gravitational field is used to explain gravitational phenomena, such as ...
. The entire gravity field was mapped from the circular orbit during a 243-day cycle of the extended mission. During the termination phase of the mission, a "windmill experiment" was performed: Atmospheric molecular pressure exerts a torque via the windmill-sail-like oriented solar cell wings, the necessary counter-torque to keep the probe from spinning is measured. In 1997, the ''
Mars Global Surveyor ''Mars Global Surveyor'' (MGS) was an American Robotic spacecraft, robotic space probe developed by NASA's Jet Propulsion Laboratory. It launched November 1996 and collected data from 1997 to 2006. MGS was a global mapping mission that examined ...
'' (MGS) orbiter was the first spacecraft to use aerobraking as the main planned technique of orbit adjustment. The MGS used the data gathered from the ''Magellan'' mission to Venus to plan its aerobraking technique. The spacecraft used its
solar panel 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 ...
s as "
wing A wing is a type of fin that produces both Lift (force), lift and drag while moving through air. Wings are defined by two shape characteristics, an airfoil section and a planform (aeronautics), planform. Wing efficiency is expressed as lift-to-d ...
s" to control its passage through the tenuous upper atmosphere of Mars and lower the
apoapsis An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...
of its orbit over the course of many months. Unfortunately, a structural failure shortly after launch severely damaged one of the MGS's solar panels and necessitated a higher aerobraking altitude (and hence one third the force) tha
originally planned
significantly extending the time required to attain the desired orbit. More recently, aerobraking was used by the ''
Mars Odyssey ''2001 Mars Odyssey'' is a robotic spacecraft orbiting the planet Mars. The project was developed by NASA, and contracted out to Lockheed Martin, with an expected cost for the entire mission of US$297 million. Its mission is to use spectro ...
'' and ''
Mars Reconnaissance Orbiter The ''Mars Reconnaissance Orbiter'' (''MRO'') is a spacecraft designed to search for the existence of water on Mars and provide support for missions to Mars, as part of NASA's Mars Exploration Program. It was launched from Cape Canaveral on Au ...
'' spacecraft, in both cases without incident. In 2014, an aerobraking experiment was successfully performed on a test basis near the end of the mission of the ESA probe ''
Venus Express ''Venus Express'' (VEX) was the first Venus exploration mission of the European Space Agency (ESA). Launched in November 2005, it arrived at Venus in April 2006 and began continuously sending back science data from its polar orbit around Venus. ...
''. In 2017–2018, the ESA ExoMars
Trace Gas Orbiter The ExoMars Trace Gas Orbiter (TGO or ExoMars Orbiter) is a collaborative project between the European Space Agency (ESA) and the Russian Roscosmos agency that sent an atmospheric research orbiter and the ''Schiaparelli'' demonstration lande ...
performed aerobraking at Mars to reduce the apocentre of the orbit, being the first operational aerobraking for a European mission. Mars Lander Mission is a future mission by
ISRO The Indian Space Research Organisation (ISRO ) is India's national space agency, headquartered in Bengaluru, Karnataka. It serves as the principal research and development arm of the Department of Space (DoS), overseen by the Prime Minister o ...
, which is proposed to use aerobraking to reduce its
apoapsis An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...
.


Aerobraking in fiction

In
Robert A. Heinlein Robert Anson Heinlein ( ; July 7, 1907 – May 8, 1988) was an American science fiction author, aeronautical engineer, and naval officer. Sometimes called the "dean of science fiction writers", he was among the first to emphasize scientific acc ...
's 1948 novel ''
Space Cadet ''Space Cadet'' is a 1948 science fiction novel by Robert A. Heinlein about Matt Dodson, who joins the Interplanetary Patrol to help preserve peace in the Solar System. The story translates the standard military academy story into outer space ...
'', aerobraking is used to save fuel while slowing the spacecraft ''Aes Triplex'' for an unplanned extended mission and landing on Venus, during a transit from the Asteroid Belt to Earth. The spacecraft ''Cosmonaut Alexei Leonov'' in
Arthur C. Clarke Sir Arthur Charles Clarke (16 December 191719 March 2008) was an English science fiction writer, science writer, futurist, inventor, undersea explorer, and television series host. Clarke co-wrote the screenplay for the 1968 film '' 2001: A ...
's 1982 novel '' 2010: Odyssey Two'' and its 1984 film adaptation uses aerobraking in the upper layers of
Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
's atmosphere to establish itself at the
Lagrangian point In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium (mechanics), equilibrium for small-mass objects under the gravity, gravitational influence of two massive orbit, orbiting b ...
of the Jupiter – Io system. In the 2004 TV series '' Space Odyssey: Voyage to the Planets'' the crew of the international spacecraft Pegasus perform an aerobraking manoeuvre in Jupiter's upper atmosphere to slow them down enough to enter Jovian orbit. In the fourth episode of ''
Stargate Universe ''Stargate Universe'' (often abbreviated as ''SGU'') is a military science fiction drama television series and part of MGM's ''Stargate'' franchise. It follows the adventures of a present-day, multinational exploration team traveling on the An ...
'', the
Ancient Ancient history is a time period from the beginning of writing and recorded human history through late antiquity. The span of recorded history is roughly 5,000 years, beginning with the development of Sumerian cuneiform script. Ancient h ...
ship ''Destiny'' suffers an almost complete loss of power and must use aerobraking to change course. The 2009 episode ends in a cliffhanger with ''Destiny'' headed directly toward a star. In the space simulation sandbox game ''
Kerbal Space Program ''Kerbal Space Program'' is a 2015 Space flight simulation game, space flight simulation video game developed by Mexican studio Squad for Linux, macOS, Windows, PlayStation 4, PlayStation 5, Xbox Series X/S and Xbox One. In the game, players dir ...
'', this is a common method of reducing a craft's
orbital speed In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter (the combined center of mass) or ...
. It is sometimes humorously referred to as "aero breaking", because the high drag sometimes causes large crafts to split in several parts. In
Kim Stanley Robinson Kim Stanley Robinson (born March 23, 1952) is an American science fiction writer best known for his ''Mars'' trilogy. Many of his novels and stories have ecological, cultural, and political themes and feature scientists as heroes. Robinson has ...
's Mars trilogy, the ''Ares'' spaceship carrying the first hundred humans to arrive on Mars uses aerobraking to enter into orbit around the planet. Later in the books, as an effort to thicken the atmosphere, scientists bring an asteroid into aerobraking in order to vaporize it and release its contents into the atmosphere. In the 2014 film '' Interstellar'', astronaut pilot Cooper uses aerobraking to save fuel and slow the spacecraft Ranger upon exiting the wormhole to arrive in orbit above the first planet.


Aerodynamic braking

Aerodynamic braking is a method used in landing aircraft to assist the wheel brakes in stopping the plane. It is often used for short runway landings or when conditions are wet, icy or slippery. Aerodynamic braking is performed immediately after the rear wheels (main mounts) touch down, but before the nose wheel drops. The pilot begins to pull back on the stick, applying elevator pressure to hold the nose high. The nose-high attitude exposes more of the craft's surface-area to the flow of air, which produces greater drag, helping to slow the plane. The raised elevators also cause air to push down on the rear of the craft, forcing the rear wheels harder against the ground, which aids the wheel brakes by helping to prevent skidding. The pilot will usually continue to hold back on the stick even after the elevators lose their authority, and the nose wheel drops, to keep added pressure on the rear wheels. Aerodynamic braking is a common braking technique during landing, which can also help to protect the wheel brakes and tires from excess wear, or from locking up and sending the craft sliding out of control. It is often used by private pilots, commercial planes, fighter aircraft, and was used by the
Space Shuttle The Space Shuttle is a retired, partially reusable launch system, reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. ...
s during landings.''Cosmic Perspectives in Space Physics'' By S. Biswas – Kluwer Academic Publishing 2000 Page 28 File:F22 Raptor landing and aerodynamic braking.JPG, An F-22 Raptor landing at
Elmendorf AFB Elmendorf Air Force Base is a United States Air Force (USAF) facility in Anchorage, Alaska. Originally known as Elmendorf Field, it became Elmendorf Air Force Base after World War II. It is the home of the Headquarters, Alaskan Air Command ( ...
, demonstrating aerodynamic braking. File:Columbia landing on Rogers dry lake.triddle.jpg, Aerodynamic braking in Space Shuttle landings.


See also

*
Aerocapture Aerocapture is an Orbital maneuver, orbital transfer maneuver in which a spacecraft uses aerodynamic drag force from a single pass through a planetary atmosphere to decelerate and achieve orbit insertion. Aerocapture uses a planet's or moon's at ...
*
Boost-glide Non-ballistic atmospheric entry is a class of atmospheric entry trajectories that follow a non-ballistic trajectory by employing aerodynamic lift in the high upper atmosphere. It includes trajectories such as skip and glide. Skip is a flight tr ...
*
Lithobraking Lithobraking is a term used by spacecraft engineers to refer to a spacecraft reducing its velocity by impacting the surface of a planet or moon.McDowell, Jonathan (2020)"Lithobraking" ''Astronautical Glossary''. Retrieved May 16, 2022. Originally ...


References


Further reading


JPL aerobraking report for MGS

An Explanation of How Aerobraking Works
(PDF) * Hoffman, S. (August 20–22, 1984)
A comparison of aerobraking and aerocapture vehicles for interplanetary missions
AIAA and AAS, Astrodynamics Conference. Seattle, Washington: American Institute of Aeronautics and Astronautics. pp. 25 p.. Retrieved 2007-07-31. {{Maglev Spacecraft propulsion Spaceflight Atmospheric entry