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Lithobraking
Lithobraking is a whimsical euphemism used by spacecraft engineers to refer to a spacecraft impacting the surface of a planet or moon.McDowell, Jonathan (2020)"Lithobraking" ''Astronautical Glossary''. Retrieved May 16, 2022. The word was coined by analogy with "aerobraking," slowing a spacecraft by intersecting the atmosphere, with "lithos" ( grc, λίθος [], "rock") substituted to indicate the spacecraft is intersecting the planet's solid lithosphere rather than merely its gaseous atmosphere. According to Jonathan McDowell, "Lithobraking reduces the apoapsis height to zero instantly, but with the unfortunate side effect that the spacecraft does not survive. Originally a whimsical euphemism, but increasingly a standard term." End-of-mission lithobraking Lithobraking is used to refer to the result of a spacecraft crashing into the rocky surface of a body with no measures to ensure its survival, either by accident or with intent. For instance, the term has been used to descri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aerobraking
Aerobraking is a spaceflight maneuver that reduces the high point of an elliptical orbit (apoapsis) by flying the vehicle through the atmosphere at the low point of the orbit (periapsis). The resulting drag slows the spacecraft. 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 to slow down. Method When an interplanetary vehicle arrives at its destination, it must reduce its velocity to achieve orbit or to land. To reach a low, near-circular orbit around a body with substantial gravity (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 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 req ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asteroid
An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. Of the roughly one million known asteroids the greatest number are located between the orbits of Mars and Jupiter, approximately 2 to 4 AU from the Sun, in the main asteroid belt. Asteroids are generally classified to be of three types: C-type, M-type, and S-type. These were named after and are generally identified with carbonaceous, metallic, and silicaceous compositions, respectively. The size of asteroids varies greatly; the largest, Ceres, is almost across and qualifies as a dwarf planet. The total mass of all the asteroids combined is only 3% that of Earth's Moon. The majority of main belt asteroids follow slightly elliptical, stable orbits, revolving in the same direction as the Earth and taking from three to six years to comple ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmospheric Reentry
Atmospheric entry 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. There are two main types of atmospheric entry: ''uncontrolled entry'', such as the entry of astronomical objects, space debris, or bolides; and ''controlled entry'' (or ''reentry'') of a spacecraft capable of being navigated or following a predetermined course. Technologies and procedures allowing the controlled atmospheric ''entry, descent, and landing'' of spacecraft are collectively termed as ''EDL''. Objects entering an atmosphere experience atmospheric drag, which puts mechanical stress on the object, and aerodynamic heating—caused mostly by compression of the air in front of the object, but also by drag. These forces can cause loss of mass (ablation) or even complete disintegration of smaller objects, and objects with lower compressive strength can explode. Crewed space vehicles must be slowed to subsonic speeds be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asteroid Capture
Asteroid capture is an orbital insertion of an asteroid around a larger planetary body. When asteroids, small rocky bodies in space, are captured, they become natural satellites. All asteroids entering Earth's orbit or atmosphere so far have been natural phenomena; however, U.S. engineers have been working on methods for telerobotic spacecraft to retrieve asteroids using chemical or electrical propulsion. These two types of asteroid capture can be categorized as natural and artificial. * Natural asteroid capture is ballistic capture of a free asteroid into orbit around a body such as a planet, due to gravitational forces. * Artificial asteroid capture involves intentionally exerting a force to insert the asteroid into a specific orbit. Artificial asteroid retrieval may provide scientists and engineers with information regarding asteroid composition, as asteroids are known to sometimes contain rare metals such as palladium and platinum. Attempts at asteroid retrieval include NASAâ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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. The change in direction is limited by the mass of the body, and how closely it can be approached. An aerogravity assist uses a closer approach to the planet, dipping into the atmosphere, so the spacecraft can also use aerodynamic lift with upside-down wings to augment gravity and further curve the trajectory. This enables the spacecraft to deflect through a larger angle, resulting in a higher delta-v (change in velocity). This in turn allows a shorter travel time, a larger payload fraction of the spacecraft, or a smaller spacecraft for a given payload. The related techniques of aerocapture, aerobraking, and atmospheric entry also attempt to use the body's atmosphere to help reduce propulsion requirements. In an aerogravity assist, h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aerocapture
Aerocapture is an 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 atmosphere to accomplish a quick, near-propellantless orbit insertion maneuver to place a spacecraft in its science orbit. The aerocapture maneuver starts as the spacecraft enters the atmosphere of the target body from an interplanetary approach trajectory. The aerodynamic drag generated as the vehicle descends into the atmosphere slows the spacecraft. After the spacecraft slows enough to be captured by the planet, it exits the atmosphere and executes a small propulsive burn at the first apoapsis to raise the periapsis outside the atmosphere. Additional small burns may be required to correct apoapsis and inclination targeting errors before the initial science orbit is established. Compared to conventional propulsive orbit insertion, this nearly fuel-free met ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Levitation Train
Maglev (derived from ''magnetic levitation''), is a system of train transportation that uses two sets of electromagnets: one set to repel and push the train up off the track, and another set to move the elevated train ahead, taking advantage of the lack of friction. Such trains rise approximately off the track. There are both high speed, intercity maglev systems (over ), and low speed, urban maglev systems ( to ) being built and under construction and development. With maglev technology, the train travels along a guideway of electromagnets which control the train's stability and speed. While the propulsion and levitation require no moving parts, the bogies can move in relation to the main body of the vehicle and some technologies require support by retractable wheels at low speeds under . This compares with electric multiple units that may have several dozen parts per bogie. Maglev trains can therefore in some cases be quieter and smoother than conventional trains and have th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Levitation
Magnetic levitation (maglev) or magnetic suspension is a method by which an object is suspended with no support other than magnetic fields. Magnetic force is used to counteract the effects of the gravitational force and any other forces. The two primary issues involved in magnetic levitation are ''lifting forces'': providing an upward force sufficient to counteract gravity, and ''stability'': ensuring that the system does not spontaneously slide or flip into a configuration where the lift is neutralized. Magnetic levitation is used for maglev trains, contactless melting, magnetic bearings and for product display purposes. Lift Magnetic materials and systems are able to attract or repel each other with a force dependent on the magnetic field and the area of the magnets. For example, the simplest example of lift would be a simple dipole magnet positioned in the magnetic fields of another dipole magnet, oriented with like poles facing each other, so that the force between mag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kraft Ehricke
Krafft Arnold Ehricke (March 24, 1917 – December 11, 1984) was a German rocket-propulsion engineer and advocate for space colonization. Biography Born in Berlin, Ehricke believed in the feasibility of space travel from a very young age, influenced by his viewing of the Fritz Lang film ''Woman in the Moon''. At the age of 12, he formed his own rocket society. He attended Technical University of Berlin and studied celestial mechanics and nuclear physics under physicists including Hans Geiger and Werner Heisenberg, attaining his degree in Aeronautical Engineering. He worked at Peenemünde as a propulsion engineer from 1942 to 1945 with Walter Thiel, then went to the United States with other German rocket scientists and technicians under "Operation Paperclip" in 1947. He worked for a short time with the Von Braun Rocket Team at Huntsville. In 1948, while working for the U.S. Army, Ehricke wrote a story about a crewed mission to Mars called "Expedition Ares". It anticipate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of Australia). The Moon is a planetary-mass object with a differentiated rocky body, making it a satellite planet under the geophysical definitions of the term and larger than all known dwarf planets of the Solar System. It lacks any significant atmosphere, hydrosphere, or magnetic field. Its surface gravity is about one-sixth of Earth's at , with Jupiter's moon Io being the only satellite in the Solar System known to have a higher surface gravity and density. The Moon orbits Earth at an average distance of , or about 30 times Earth's diameter. Its gravitational influence is the main driver of Earth's tides and very slowly lengthens Earth's day. The Moon's orbit around Earth has a sidereal period of 27.3 days. During each synodic period ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LUNAR-A
LUNAR-A is a cancelled Japanese spacecraft project that was originally scheduled to be launched in August 2004. After many delays (primarily due to potential thruster faults), the project was eventually cancelled in January 2007. It was planned to be launched on a Japanese M-V rocket from the Kagoshima Space Center. History The vehicle would have been cylindrical, with a diameter of 2.2 m and a height of 1.7 m. It would have had four solar panels and was engineered to be spin-stabilized. Plans called for it to enter an elliptical orbit around the Moon, and deploy two penetrators at an altitude of 40 km on opposite sides of the lunar body. The penetrators were to have been braked by a small rocket at an altitude of 25 km, then free fall to the surface. They were designed to withstand a collision speed of 330 meters per second to deeply penetrate the lunar regolith. Once the penetrators deployed, the LUNAR-A spacecraft was mission-planned to maneuver to an orbi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deep Space 2
Deep Space 2 was a NASA space probe, part of the New Millennium Program. It included two highly advanced miniature space probes that were sent to Mars aboard the Mars Polar Lander in January 1999. The probes were named "Scott" and "Amundsen", in honor of Robert Falcon Scott and Roald Amundsen, the first explorers to reach the Earth's South Pole. Intended to be the first spacecraft to penetrate below the surface of another planet, after entering the Mars atmosphere DS2 was to detach from the Mars Polar Lander mother ship and plummet to the surface using only an aeroshell impactor, with no parachute. The mission was declared a failure on March 13, 2000, after all attempts to reestablish communications following the descent went unanswered. The Deep Space 2 development costs were US$28 million. Overview thumbnail, Deep Space 2 project manager Sarah Gavit with the engineering hardware of the probe Deep Space 2, also known as "Mars Microprobe," was the second spacecraft developed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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