3.5 Motions of Satellites and Spacecraft
2 min read•june 12, 2024
Orbits and spacecraft trajectories are crucial for space exploration. From placing satellites in Earth's orbit to sending probes to distant planets, understanding is key. We'll explore the physics behind orbits and the strategies used to navigate the cosmos.
Launching satellites, escaping Earth's gravity, and maneuvering through space all require precise calculations. We'll look at the differences between low Earth orbits and interplanetary trajectories, and learn about the clever techniques used to save fuel and reach far-off destinations.
Orbits and Spacecraft Trajectories
Satellite orbit placement
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Top images from around the web for Satellite orbit placement
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- Launch above Earth's atmosphere (thermosphere) to reduce drag forces
- Rocket accelerates satellite to
- Circular orbit velocity (: gravitational constant, : Earth's mass, : orbit radius)
- Higher orbits require lower velocities (: 3.1 km/s, : 7.8 km/s)
- Release satellite from rocket at target altitude and velocity
- Satellite's velocity perpendicular to gravity causes it to fall around Earth in a circular (same altitude) or elliptical (varying altitude) path
- Elliptical orbits have an (farthest point from Earth) and (closest point to Earth)
Earth orbit escape requirements
- Achieve to overcome Earth's gravity
- Earth's surface : 11.2 km/s
- Escape velocity decreases with distance from Earth (Moon's orbit: 1.4 km/s)
- High energy needed to reach escape velocity
- Chemical rockets most common propulsion (Space Shuttle, Saturn V)
- Staged rockets reduce spacecraft mass as fuel consumed (, )
- Launch eastward near equator to minimize drag and use Earth's rotational velocity boost (, )
Low Earth orbit vs interplanetary trajectories
- Low Earth orbit (LEO) satellites:
- Orbit 160-2,000 km above Earth (, )
- Lower energy than interplanetary spacecraft
- More atmospheric drag requires periodic boosts (ISS reboost every 2-3 months)
- Mostly circular or slightly elliptical orbits
- Interplanetary spacecraft:
- Must escape Earth's gravity for solar system travel ( & 2, )
- Much higher energy than LEO to reach escape velocity
- Gravitational assist slingshots around planets to gain speed and save fuel ( around Venus and Earth)
- Elliptical or hyperbolic trajectories based on mission ( around Mercury, New Horizons hyperbolic flyby of Pluto)
- May orbit or flyby target body ( orbited Jupiter, flyby of Venus and Mercury)
Orbital Mechanics and Spacecraft Maneuvers
- describe the motion of orbiting bodies
- : efficient method to move between two circular orbits
- : change in velocity required for orbital maneuvers
- : using a planet's gravity to change a spacecraft's trajectory and speed
Key Terms to Review (29)
Apogee: Apogee is the point in an orbit around Earth where the orbiting object is farthest from the planet. It is one of two apsides, the other being perigee, which is the closest point.
Apogee: Apogee refers to the point in an object's orbit around Earth when it is farthest from the planet's surface. This term is particularly relevant in the context of the motions of satellites and spacecraft, the phases and motions of the Moon, ocean tides, and eclipses of the Sun and Moon.
Ariane 5: Ariane 5 is a heavy-lift launch vehicle that has been used to launch a variety of payloads, including satellites and spacecraft, into Earth's orbit and beyond. It is a critical component in the context of the motions of satellites and spacecraft, as it provides the means to transport these objects into space.
Cape Canaveral: Cape Canaveral is a region on the Atlantic coast of Florida, United States, that has been the site of numerous space launches and rocket testing since the 1950s. It is a crucial location for the motions of satellites and spacecraft, serving as a launch pad for various space missions.
Cassini: Cassini was a spacecraft mission that studied the planet Saturn, its rings, and its moons in great detail. It was a collaborative effort between NASA, the European Space Agency, and the Italian Space Agency, and its observations have significantly advanced our understanding of the Saturnian system.
Delta-V: Delta-V, or change in velocity, is a fundamental concept in astronautics and rocketry that represents the amount of velocity a spacecraft or satellite must attain to accomplish a particular maneuver or change in orbit. It is a crucial factor in determining the energy requirements and feasibility of various space missions and orbital transfers.
Elliptical Orbit: An elliptical orbit is a type of orbital path in which a satellite or spacecraft revolves around a larger body, such as a planet or the Sun, in an elliptical shape rather than a perfect circle. This orbital pattern is a fundamental concept in the study of the motions of satellites and spacecraft.
Escape velocity: Escape velocity is the minimum speed an object must reach to break free from the gravitational pull of a massive body without further propulsion. In astronomy, it's crucial for understanding phenomena like black holes where gravitational forces are extreme.
Escape Velocity: Escape velocity is the minimum speed an object must attain to break free of a planet or moon's gravitational pull and enter outer space without being pulled back down. It is a fundamental concept in the study of orbital mechanics and the motion of satellites and spacecraft.
Falcon 9: Falcon 9 is a reusable, two-stage-to-orbit medium-lift launch vehicle developed and operated by SpaceX. It is designed to transport satellites and the Dragon spacecraft into orbit around Earth.
Galileo: Galileo Galilei was a renowned Italian astronomer, physicist, engineer, and philosopher who played a pivotal role in the scientific revolution of the 17th century. His groundbreaking observations and discoveries significantly contributed to the birth of modern astronomy and our understanding of the universe.
Geostationary Orbit: A geostationary orbit is a specific type of Earth orbit where a satellite revolves around the planet at the same rate as the Earth's rotation, effectively remaining stationary relative to a point on the Earth's surface. This unique orbital pattern is crucial for various applications in the context of satellite and spacecraft motions.
Gravitational Slingshot: A gravitational slingshot, also known as a gravity assist, is a technique used in spacecraft navigation to increase a spacecraft's velocity by using the gravity of a planet or other celestial body. This maneuver allows a spacecraft to gain speed and change direction without expending additional fuel.
Guiana Space Centre: The Guiana Space Centre, also known as the Guiana Space Port, is a spaceport located in French Guiana, South America. It serves as the primary launch site for the European Space Agency's (ESA) space programs, as well as other international space missions.
Hohmann Transfer Orbit: A Hohmann transfer orbit is a type of spacecraft trajectory used to move a spacecraft between two circular orbits, typically from a lower orbit to a higher orbit or vice versa, in the most fuel-efficient manner. It is named after the German engineer Walter Hohmann, who first described this orbital transfer method.
Hubble Space Telescope: The Hubble Space Telescope is a large, space-based observatory that has revolutionized our understanding of the universe. Launched in 1990, it orbits the Earth outside the distortion of the atmosphere, providing clear and detailed images of celestial objects. The Hubble Telescope's unique position above the Earth's atmosphere allows it to observe the cosmos in ways that ground-based telescopes cannot, making it a crucial tool for advancing our knowledge of astronomy and cosmology.
International Space Station: The International Space Station (ISS) is a large, permanently crewed, artificial satellite that orbits the Earth at an average altitude of about 400 kilometers (250 miles). It serves as a unique microgravity laboratory for scientific research and a platform for various space-based activities, including satellite deployment and maintenance, as well as human space exploration and habitation.
Kepler's Laws of Planetary Motion: Kepler's laws of planetary motion are three fundamental principles that describe the motion of planets around the Sun. These laws were formulated by the German astronomer Johannes Kepler in the early 17th century and are essential in understanding the orbits of objects within the Solar System, including the motion of satellites and spacecraft.
Low Earth Orbit: Low Earth orbit (LEO) refers to the region of space surrounding the Earth where satellites and spacecraft orbit at altitudes below 2,000 kilometers (1,200 miles) above the Earth's surface. This orbital regime is characterized by a relatively short orbital period and close proximity to the Earth's atmosphere.
Mariner 10: Mariner 10 was a NASA spacecraft launched in 1973 to study the planet Mercury and its environment. It was the first spacecraft to visit multiple planets, making three flybys of Mercury and one of Venus before running out of fuel.
MESSENGER: MESSENGER is an acronym that stands for 'MErcury Surface, Space ENvironment, GEochemistry and Ranging', which was a NASA robotic spacecraft that orbited the planet Mercury from 2004 to 2015. It was the first spacecraft to orbit the planet Mercury, providing valuable data and insights about the planet's composition, geology, and magnetic field.
New Horizons: New Horizons is a NASA spacecraft launched in 2006 with the primary mission of studying Pluto and the Kuiper Belt, the region of the solar system beyond the orbit of Neptune. It is the first spacecraft to explore Pluto and the farthest planetary object ever visited by a spacecraft.
Orbital Mechanics: Orbital mechanics, also known as celestial mechanics, is the study of the motion of objects around other objects, such as planets, stars, or other celestial bodies. It is a fundamental concept in astronomy that describes the complex interactions and trajectories of objects in space.
Orbital Velocity: Orbital velocity is the speed at which an object, such as a planet or satellite, travels in its orbit around another object, typically a larger body like a star or planet. This velocity is a critical factor in determining the stability and characteristics of an object's orbit.
Perigee: Perigee is the point in an orbit of a celestial body where it is closest to Earth. It applies to any object, such as the Moon or a satellite, that is orbiting our planet.
Perigee: Perigee refers to the point in the orbit of a satellite, the Moon, or any other celestial body when it is closest to the Earth. This term is particularly important in the context of understanding the motions of satellites and spacecraft, the phases and motions of the Moon, ocean tides, and eclipses of the Sun and Moon.
Satellite: A satellite is an object that orbits a planet or another celestial body. Satellites can be natural, like moons, or artificial, like spacecraft launched from Earth.
Voyager 1: Voyager 1 is a robotic spacecraft launched by NASA in 1977 to study the outer solar system and eventually interstellar space. It is the first human-made object to leave the solar system and continue on into the vast expanse of interstellar space, providing invaluable data about the outer planets, the heliosphere, and the nature of the cosmos beyond our solar system.
Voyager 2: Voyager 2 is an unmanned interplanetary spacecraft launched by NASA in 1977 to study the outer planets of our solar system. It is one of the most successful and long-lasting space missions, providing invaluable data and images that have significantly expanded our understanding of the distant worlds it has explored.