Jarkowski-Effekt. Der Jarkowski-Effekt wurde um 1900 von dem russisch-polnischen Ingenieur Iwan Ossipowitsch Jarkowski beschrieben und nach ihm benannt. Er erklärt den Einfluss einer schwankenden Oberflächenerwärmung von Asteroiden auf deren Bahnverlauf. Beschreibung[Bearbeiten] 1: Oberflächenstrahlung, 2: prograd rotierendes Objekt, 3: Orbit, 4: Sonneneinstrahlung Siehe auch[Bearbeiten] Weblinks[Bearbeiten]
Optical tweezers. History and development[edit] The detection of optical scattering and gradient forces on micron sized particles was first reported in 1970 by Arthur Ashkin, a scientist working at Bell Labs.[1] Years later, Ashkin and colleagues reported the first observation of what is now commonly referred to as an optical tweezer: a tightly focused beam of light capable of holding microscopic particles stable in three dimensions.[2] One of the authors of this seminal 1986 paper, former United States Secretary of Energy Steven Chu, would go on to use optical tweezing in his work on cooling and trapping neutral atoms.[3] This research earned Chu the 1997 Nobel Prize in Physics along with Claude Cohen-Tannoudji and William D.
In the late 1980s, Arthur Ashkin and Joseph M. Optical tweezers have proven useful in other areas of biology as well. The Kapitsa–Dirac effect effectively demonstrated during 2001 uses standing waves of light to affect a beam of particles. Physics[edit] General description[edit] where. 3753 Cruithne. 3753 Cruithne (/kruːˈiːnjə/[2] or /ˈkrʊnjə/)[3] is an Aten asteroid in orbit around the Sun in 1:1 orbital resonance with Earth, making it a co-orbital object. It is a minor planet in solar orbit that, relative to Earth, orbits in a bean-shaped orbit that ultimately effectively describes a horseshoe, and which can transition into a quasi-satellite orbit.[4] It has been incorrectly called "Earth's second moon".[2][5] Cruithne does not orbit Earth and at times it is on the other side of the Sun.[6] Its orbit takes it inside the orbit of Mercury and outside the orbit of Mars.[6] Cruithne orbits the Sun in about 1 year but it takes 770 years for the series to complete a horseshoe-shaped movement around the Earth.[6] The name Cruithne is from Old Irish and refers to the early Picts (Irish: Cruthin) in the Annals of Ulster[6] and their eponymous king ("Cruidne, son of Cinge") in the Pictish Chronicle.
The name is cognate with "Britain" and "British".[7] Discovery[edit] Figure 1. See also[edit] Near-Earth object. Animation of the rotation of 433 Eros, a Near-Earth asteroid visited by an unmanned spacecraft A near-Earth object (NEO) is a Solar System object whose orbit brings it into proximity with Earth. All NEOs have a closest approach to the Sun (perihelion) of less than 1.3 AU.[2] They include a few thousand near-Earth asteroids (NEAs), near-Earth comets, a number of solar-orbiting spacecraft, and meteoroids large enough to be tracked in space before striking the Earth.
It is now widely accepted that collisions in the past have had a significant role in shaping the geological and biological history of the planet.[3] NEOs have become of increased interest since the 1980s because of increased awareness of the potential danger some of the asteroids or comets pose to Earth, and active mitigations are being researched.[4] In the United States, NASA has a congressional mandate to catalogue all NEOs that are at least 1 kilometer wide, as the impact of such an object would be catastrophic. Risk[edit] Gravity assist.
The trajectories that enabled NASA's twin Voyager spacecraft to tour the four gas giant planets and achieve velocity to escape our solar system The "assist" is provided by the motion of the gravitating body as it pulls on the spacecraft.[1] The technique was first proposed as a mid-course manoeuvre in 1961, and used by interplanetary probes from Mariner 10 onwards, including the two Voyager probes' notable fly-bys of Jupiter and Saturn. Explanation[edit] A gravity assist around a planet changes a spacecraft's velocity (relative to the Sun) by entering and leaving the gravitational field of a planet. The spacecraft accelerates as it approaches the planet and decelerates while escaping its gravitational pull (which is approximately the same). Because the planet orbits the sun, the spacecraft is affected by this motion during the maneuver. A close terrestrial analogy is provided by a tennis ball bouncing off a moving train.
Two-dimensional schematic of gravitational slingshot. Lightcraft. Lightcraft being propelled by laser A lightcraft is a space- or air-vehicle driven by laser propulsion. Laser propulsion is in early stages of development. Lightcraft uses an external source of laser or maser energy to provide power for producing thrust. The laser/maser energy is focused to a high intensity in order to create a plasma. The plasma expands, producing thrust.[1] A lightcraft is distinct from a solar sail because it is dependent on the expansion of reaction mass to accelerate rather than being accelerated by light pressure alone. Types[edit] In one type of lightcraft, the laser shines on a parabolic reflector on the underside of the vehicle that concentrates the light to produce a region of extremely high temperature.
In other lightcraft concepts, the laser arrives at the vehicle from above, and operates as an ablative laser tractor beam.[2] This may have applications in the removal of space debris.[3] Description[edit] See also[edit] References[edit] External links[edit] Optical lift. Discovery[edit] Optical lift is a component of force imparted from uniform light. First CP1 fabricated flying carpets The experiment began as computer models that suggested when light is incident on a tiny object shaped like a wing, a stable lift force is applied to the particle. Then the researchers decided to do physical experiments in the laboratory, and they created tiny, transparent, micrometer-sized rods that were flat on one side and rounded on the other, rather like airplane wings. In optical lift, created by a "lightfoil", the lift is created within the transparent object as light shines through it and is refracted by its inner surfaces.
Potential uses[edit] Using optical lift to steer solar sails The 2010 discovery of stable optical lift is considered by some physicists to be "most surprising".[3] Unlike optical tweezers, an intensity gradient is not required to achieve a transverse force. See also[edit] References[edit] External links[edit] Elevator:2010. Elevator:2010 was an inducement prize contest similar to the Ansari X Prize, but with the purpose of developing space elevator and space elevator-related technologies.
Elevator:2010 organized annual competitions for climbers, ribbons and power-beaming systems, and was operated by a partnership between Spaceward Foundation and the NASA Centennial Challenges. History[edit] On March 23, 2005 NASA's Centennial Challenges program announced a partnership with the Spaceward Foundation regarding Elevator:2010, to raise the amounts of monetary prizes and to get more teams involved in the competitions.[1] The partnership was not renewed after its initial 5 year term.[2] There were two (out of an intended seven) competitions of the NASA Centennial Challenges which fell under the Elevator:2010 banner: The Tether Challenge and the Beam Power Challenge.
There were also the two original competitions. Tether Challenge[edit] Beam Power Challenge[edit] Future competitions[edit] See also[edit] References[edit] Space elevator. A space elevator for Earth would consist of a cable fixed to the Earth's equator, reaching into space. By attaching a counterweight at the end (or by further extending the cable upward for the same purpose), the center of mass is kept well above the level of geostationary orbit. Upward centrifugal force from the Earth's rotation ensures that the cable remains stretched taut, fully countering the downward gravitational pull.
Once above the geostationary level, climbers would have weight in the upward direction as the centrifugal force overpowers gravity. (The height relative to the diameter of the Earth on the diagram is to scale. The height of the counterweight varies by design and a typical, workable height is shown.) A space elevator is a proposed type of space transportation system.[1] Its main component is a ribbon-like cable (also called a tether) anchored to the surface and extending into space. The concept is also applicable to other planets and celestial bodies. History where or. Ram accelerator. A ram accelerator is a device for accelerating projectiles to extremely high speeds using jet-engine-like propulsion cycles based on ramjet and/or scramjet combustion processes.
It is thought to be possible to achieve non-rocket spacelaunch with this technology. They consist of a long tube (barrel) filled with a mixture of combustible gases with a frangible diaphragm at either end to contain the gases. The projectile, which is shaped like a ramjet core, is fired by another means (e.g., a light gas gun) supersonically through the first diaphragm into the tube. It then burns the gases as fuel, accelerating down the tube under jet propulsion. Other physics come into play at higher velocities.
Description[edit] In a normal ramjet, air is compressed between a spike-shaped centerbody and an outer cowling, fuel is added and burned, and high speed exhaust gases are expanded supersonically out the nozzle to generate thrust. Advantages[edit] Uses[edit] See also[edit] External links[edit] Spacecraft propulsion. Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. There are many different methods. Each method has drawbacks and advantages, and spacecraft propulsion is an active area of research. However, most spacecraft today are propelled by forcing a gas from the back/rear of the vehicle at very high speed through a supersonic de Laval nozzle.
This sort of engine is called a rocket engine. All current spacecraft use chemical rockets (bipropellant or solid-fuel) for launch, though some (such as the Pegasus rocket and SpaceShipOne) have used air-breathing engines on their first stage. Most satellites have simple reliable chemical thrusters (often monopropellant rockets) or resistojet rockets for orbital station-keeping and some use momentum wheels for attitude control. Soviet bloc satellites have used electric propulsion for decades, and newer Western geo-orbiting spacecraft are starting to use them for north-south stationkeeping and orbit raising. ). ). Laser propulsion. Laser propulsion is a form of beam-powered propulsion where the energy source is a remote (usually ground-based) laser system and separate from the reaction mass.
This form of propulsion differs from a conventional chemical rocket where both energy and reaction mass come from the solid or liquid propellants carried on board the vehicle. A laser launch Heat Exchanger Thruster system History[edit] The basic concepts underlying laser propulsion were first developed by Eugene Sanger and the Hungarian physicist Georgii Marx, with practical schemes being developed by Arthur Kantrowitz and Wolfgang Moekel in the 1970s.[1] Laser propulsion systems may transfer momentum to a spacecraft in two different ways. The first way uses photon radiation pressure to drive momentum transfer and is the principle behind solar sails and laser sails. The second method uses the laser to help expel mass from the spacecraft as in a conventional rocket. Forms[edit] There are several forms of laser propulsion.
Light gas gun. The light-gas gun is an apparatus for physics experiments, a highly specialized gun designed to generate very high velocities. It is usually used to study high speed impact phenomena (hypervelocity research), such as the formation of impact craters by meteorites or the erosion of materials by micrometeoroids. Some basic materials research relies on projectile impact to create high pressure: such systems are capable of forcing liquid hydrogen into a metallic state.
Operation[edit] A light-gas gun works on the same principle as a spring piston airgun. A large-diameter piston is used to force a gaseous working fluid through a smaller-diameter barrel containing the projectile to be accelerated. This reduction in diameter acts as a lever, increasing the speed while decreasing the force. One particular light-gas gun used by NASA uses a modified 40 mm cannon for power.
Design physics[edit] Hybrid electrothermal light-gas gun[edit] Impact profile[edit] See also[edit] References[edit] Railgun. Naval Surface Warfare Center test firing in January 2008[1] A railgun is an electrically powered electromagnetic projectile launcher based on similar principles to the homopolar motor. A railgun comprises a pair of parallel conducting rails, along which a sliding armature is accelerated by the electromagnetic effects of a current that flows down one rail, into the armature and then back along the other rail.[2] Railguns have long existed as experimental technology but the mass, size and cost of the required power supplies have prevented railguns from becoming practical military weapons.
However, in recent years, significant efforts have been made towards their development as feasible military technology. Basics[edit] Schematic diagram of a railgun In its simplest (and most commonly used) form, the railgun differs from a traditional homopolar motor in that no use is made of additional field coils (or permanent magnets). A railgun requires a pulsed, direct current power supply. History[edit] Hall effect thruster. In spacecraft propulsion, a Hall thruster is a type of ion thruster in which the propellant is accelerated by an electric field. Hall thrusters trap electrons in a magnetic field and then use the electrons to ionize propellant, efficiently accelerate the ions to produce thrust, and neutralize the ions in the plume.
Hall thrusters are sometimes referred to as Hall effect thrusters or Hall current thrusters. Hall thrusters are often regarded as a moderate specific impulse (1,600 s) space propulsion technology. The Hall effect thruster has benefited from considerable theoretical and experimental research since the 1960s.[1] Hall thrusters operate on a variety of propellants, the most common being xenon.
Hall thrusters are able to accelerate their exhaust to speeds between 10–80 km/s (1,000–8,000 s specific impulse), with most models operating between 15–30 km/s (1,500–3,000 s specific impulse). History[edit] Two types of Hall thrusters were developed in the Soviet Union: Operation[edit] Ion thruster. Space gun. Space tether. Electrically powered spacecraft propulsion. Electrodynamic tether.
Variable Specific Impulse Magnetoplasma Rocket. Magnetoplasmadynamic thruster. Beam-powered propulsion. Mass driver. High Power Electric Propulsion. Resistojet rocket. MagBeam. Helicon Double Layer Thruster. Pulsed plasma thruster. Variable Specific Impulse Magnetoplasma Rocket. Electrodeless plasma thruster. Magnetoplasmadynamic thruster. Pulsed inductive thruster. Ionocraft. Arcjet rocket. Electrostatic ion thruster.
Nano-particle field extraction thruster. Field-emission electric propulsion. Colloid thruster.