Space Stations - Atomic Rockets. Many, but not all, space stations are in orbit around a planet. An orbit is a clever way to constantly fall towards a planet but never hit the ground. There are certain preferred orbits. An equatorial orbit is a non- inclined orbit with respect to Terra's equator (i. Most civilian satellites use such orbits. The United States uses Cape Canaveral Air Force Station and the Kennedy Space Center to launch into equatorial orbits. Collection of Software bugs, glitches, errors, disasters like Ariane 5, Pentium bug, Sleipner, Patriot, Mars Climate Orbiter, Mars Sojourner, London Millenium Bridge, Mars Rover Spirit, Pathfinder, denver Airport, Therac-25.An ecliptic orbit is a non- inclined orbit with respect to the solar system ecliptic. An inclined orbit is any orbit that does not have zero inclination to the plane or reference (usually the equator). A polar orbit is a special inclined orbit that goes over each pole of the planet in turn, as the planet spins below (i. The advantage is that the orbit will eventually pass over every part of the planet, unlike other orbits. Such an orbit is generally used for military spy satellites, weather satellites, orbital bombardment weapons, and Google Earth. The United States uses Vandenberg Air Force Base to launch into polar orbits. Google Earth uses data from the Landsat program, whose satellites are launched from Vandenberg. The Hill Sphere. It is greatly desired that satellites and space stations stay in stable orbits, because corporations and insurance companies become quite angry if hundred million dollar satellites or expensive space stations with lots of people are gravitationally booted into The Big Dark. A good first approximation is ensuring that the orbiting object stays inside the parent's Hill Sphere. This is an imaginary sphere centered on the parent planet (the planet or moon the satellite is orbiting). Within the sphere, the planet's gravity dominates any satellites. For first approximation you have three players: the space station (e. Get information, facts, and pictures about Antigua and Barbuda at Encyclopedia.com. Make research projects and school reports about Antigua and Barbuda easy with credible articles from our FREE, online encyclopedia and dictionary. Supra- New York), the planet or moon it is orbiting (e. Terra), and the object the planet is orbiting (e. Sol) otherwise known as the planet's . The same goes for units of mass for m and M. This equation assumes that the planet is in a near- circular orbit. If it has some weird eccentric orbit the Hill Sphere link has the more complicated equation. The above equation also assumes that the mass of the station or sattelite is miniscule compared to the object it is orbiting. It further assumes that the mass of the primary is quite a bit bigger than the mass of the planet. In practice, for long term stability, the station should not orbit its planet further than one- half the Hill sphere radius. No further than one- third the Hill sphere radius if you are ultra- cautious. EXAMPLEWhat is the Hill sphere radius of Terra? In this case, the planet is Terra, the primary is Sol, the mass of Terra (m) is 5. Luna is at 0. 3. 84 million kilometers, safely inside the Hill sphere. Using other people’s research or ideas without giving them due credit is plagiarism. AOL Radio is powered by humans! Great radio is all about unexpected connections--the kind that an algorithm can't predict. Pick any station in any of the 30 genres AOL Radio DJs have programmed for you and hear the difference. La United States Air Force (abbreviazioni comunemente utilizzate: U.S. Air Force, US Air Force, Air Force, USAF) The implication is that all of Terra's stable satellites have an orbital period of less than seven months. Supra- New York would do well to stay inside. The long term stable radius is 0. Terra's center (1/2 Hill sphere). The ultra- cautious radius is 0. Hill sphere). If you were interested in Lunar satellites, the planet would be Luna, the primary would be Terra, and a would be the distance between Terra and Luna. Any object (like a spaceship) which enters a planet's Hill sphere but does not have enough energy to escape, will tend to start orbiting the planet. The surface of the Hill sphere is sometimes called the . So one would have expected that the International Space Station (ISS) would be in a 2. So that Russian cargo rockets from Baikonur Cosmodrome can reach it. Launching into a different inclination than the space port's latitude costs rocket propellant and reduces payload. Changing the ISS planned inclination to 5. When NASA stupidly cancelled the Space Shuttle program before the replacement vehicle was online, they assured everybody that the replacement would be flying by 2. This would make a small three- year gap in NASA's ISS transport ability. Unfortunately and predictably when 2. NASA has not even started work on deciding which of the many proposals will be used, much less bending metal and cranking out functional rockets. This leaves NASA at the mercy of the Russians for access to the ISS, but without the Russians there would be no access at all and the station would have long ago burnt up in reentry like Skylab. But I digress. Clever readers will say but wait! Baikonur Cosmodrome is at latitude 4. In a perfect world, yes, but there is a problem. When a spacecraft is launched from Kennedy Space Center the lower stages fall into the Atlantic Ocean. And if something goes really wrong, the entire spacecraft can abort and ditch into the ocean as well. If Baikonur Cosmodrome did the same thing, large spent lower stage boosters and/or huge flaming aborting Russian spacecraft would crash into Mainland China, and the political situation would rapidly deteriorate. To avoid that unhappy state of affairs, Russian spacecraft launched from Baikonur go at a 5. They really dislike having much the same problem with respect to space launches. Therefore they are in negotiations for launch privileges at the ESA's. Guiana Space Centre, which is optimally located quite near the Equator and to the West of the Atlantic Ocean. Orbits around Terra (geocentric) are sometimes classified by altitude above Terra's surface: Low Earth Orbit (LEO): 1. At 1. 60 km one revolution takes about 9. Affected by inner Van Allen radiation belt. Medium Earth Orbit (MEO): 2,0. The most common altitude is 2. Geosynchronous Orbit (GEO): exactly 3. Terra (4. 2,1. 64 km from center of Terra). One revolution takes one sidereal day, coinciding with the rotational period of Terra. Circular orbital speed is about 3 km/s. It is jam- packed with communication satellites like sardines in a can. This orbit is affected by the outer Van Allen radiation belt. High Earth Orbit (HEO): anything with an apogee higher than 3. If the perigee is less than 2,0. Clarke) are desirable orbits for communication and spy satellites because they return to the same position over the planet after a period of one sidereal day (for Terra that is about four minutes short of one ordinary day). A Geostationary Orbit is a special kind of geosynchronous orbit that is even more desirable for such satellites. In those orbits, the satellite always stays put over one spot on Terra like it was atop a 3. For complicated reasons all geostationary orbits have to be over the equator of the planet. In theory only three communication satellites in geostationary orbit and separated by 1. Things get ugly when you have, for instance, two nations at the same longitude but at different latitudes: both want the same slot. Russia uses highly eccentric orbits since those latitudes more or less define Russia. Russian communication satellites commonly use Molniya orbits and Tundra orbits. About 3. 00 kilometers above geosynchronous orbit is the . This is where geosynchronous satellites are moved at the end of their operational life, in order to free up a slot. It would take about 1,5. V to de- orbit an old satellite, but only 1. Most satellites have nowhere near enough propellant to deorbit. Those three hundred people in LEO Base can get back to Earth in less than an hour if necessary; we'll have lifeboats, so to speak, in case of an emergency. But out there at GEO Base, it's a long way home. Takes eight hours or more just to get back to LEO, where you have to transfer from the deep- space passenger ship to a Star. Packet that can enter the atmosphere and land. It takes maybe as long as a day to get back to Earth from GEO Base— and there's a lot of stress involved in the trip. I'm required by my license from the Department of Energy as well as by the regulations of the Industrial Safety and Health Administration, ISHA, to set up a hospital at GEO Base. It'll be in weightlessness; it'll have to handle construction accidents of an entirely new type; it'll have to handle emergencies resulting from a totally alien environment; it'll require the development of a totally new area of medicine— true space medicine. The job requires a doctor who's worked with people in isolated places—like the Southwest or aboard a tramp steamer. It's the sort of medicine you've specialized in. In short, T. K., you're the only man I know who could do the job . There were a lot of hatches to go through and a lot of modules to traverse. A scooter to anybody but these acronym- happy engineers. It required almost a half hour to bring the man back to the med module. Lagrangian points are special points were a space station can sit in a sort- of orbit. Lagrange point 1, 2, and 3 are sort of worthless, since objects there are only in a semi- stable position. The ones you always hear about are L4 and L5, because they have been popularized as the ideal spots to locate giant space colonies. Especially since the plan was to construct such colonies from Lunar materials to save on boost delta V costs. The important thing to remember is that the distance between L4 — Terra, L4 — Luna, and Terra — Luna are all the same (about 3. Meaning it will take just as long to travel from Terra to L4 as to travel from Terra to Luna. For a more exhaustive list of possible Terran orbits refer to NASA. It is also possible for a satellite to stay in a place where gravity will not allow it. All it needs is to be under thrust. Which is rather expensive in terms of propellant. Forward noted that solar sails use no propellant, so they can hold a satellite in place forever (or at least as long as the sun shines and the sail is undamaged). This is called a Statite. If the planet has an atmosphere and the station orbits too low, it will gradually slow down due to atmospheric drag. Some fragments might survive to hit the ground. The . When the solar activity is high, the Earth's atmosphere expands, so what was a safe altitude is suddenly not so safe anymore. NASA found this out the hard way with the Skylab mission. In 1. 97. 4 it was parked at an altitude of 4.
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