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(Anulowanie wersji nr 17286102 autora Leafnode)
[[Image:LaunchLoop.svg|thumb|right|Launch Loop (with thanks to Keith Lofstrom-1985)]]
A '''launch loop''' or '''Lofstrom loop''' is a design for a [[belt (mechanical)|belt]] based [[maglev]] [[orbital launch]] system that would be around 2000 km long and maintained at an altitude of up to 80 km (50 mi). It provides a potential way of [[non-rocket spacelaunch]]. [[Statek kosmicznySpacecraft|Vehicles]] weighing 5 metric tons would be [[maglev|electromagnetically accelerated]] on top of the cable which forms an acceleration track, from which they would be projected into Earth [[Orbita|Orbitorbit]] or even beyond.
 
The published cost estimates for a working launch loop are significantly lower than a [[Winda kosmiczna|Spacespace elevator]], with a greater launch capacity, lower payload costs and similar or greater payload masses; and unlike the space elevator no new materials need to be developed.
 
The system is designed to be suitable for launching humans for [[turysta kosmiczny|Spacespace tourism]], [[Eksploracja kosmosu|Spacespace exploration]] and [[Kolonizacja kosmosu|Spacespace colonization]].
==Description==
[[Image:LaunchLoopRotor.png|thumb|right|Launch loop accelerator section (with thanks to Keith Lofstrom-2002)]]
The launch loop was proposed in 1985 by [[Keith Lofstrom]]. It is essentially a hybrid of the [[orbital ring]] concept and the [[space fountain]]. It is an oval ring around 2000 km long, it has two base stations about 2000 km apart on Earth which can launch and catch a very fast moving [[Żelazo|Ironiron]] belt called a "rotor" to and from high altitude.
 
Although the loop is very long, at around 4000 km circumference, the belt itself is thin, around 5 cm diameter and the sheath is not much bigger. The rotor for the loop is made of iron and is in the shape of a pipe, and it is spaced from a sheath by [[magnetic bearing]]s. As well as holding the belt in place, the sheath also maintains a vacuum which avoids atmospheric friction.
 
The loop starts off at ground level, and stationary. The rotor is spun up, turned by a [[Silnik liniowy|Linearlinear motor]] powered by a several hundred megawatt power station. As the speed increases the central parts of the structure are arranged to push upwards into an approximate arch shape- carried there by the momentum of the rotor. When the cable reaches an altitude of around 80 kilometers the loop is restrained and shaped by cables that hang down to sea level. The rotor is spun up to a linear speed of 14 km/s taking almost 5 minutes to make a revolution. Using a 300 MW power generator, this would take about two months to reach full speed.
 
Once raised, the structure needs some power to deal with power dissipated in the magnetic bearings and energy to deal with the imperfect vacuum in the sheath; overall this requires around 200 MW of energy. Additional energy would be needed to power any vehicles that are launched.
==Launching payloads==
 
To launch, vehicles are raised up on elevators to a loading dock at 80 km, and placed on the track. The payload then creates a magnetic field which generates [[Prąd wirowy|Eddyeddy current]]s in the fast-moving rotor, which both lift the payload away from the cable, as well as pulling the payload along with 3''g'' (30 m/s²) acceleration. The payload then rides the rotor until it reaches the required orbital velocity, and then leaves the track.
 
If a stable or circular orbit is needed, once the payload reaches the highest part of its trajectory then an on-board rocket engine ("kick motor") or other means is needed to circularise the trajectory to the appropriate Earth orbit.<ref>[http://www.launchloop.com/launchloop.pdf PDF version of Lofstrom's 1985 launch loop publication (AIAA 1985)]</ref>
 
The eddy current technique is compact, lightweight and powerful, but inefficient. With each launch the rotor temperature increases by 80 [[Kelwin|Kelvinkelvin]]s due to power dissipation. If launches are spaced too close together, the rotor temperature can approach 770 °C (1043 K), at which point the iron rotor loses its [[Ferromagnetyzmferromagnetism|ferromagnetic]] properties and rotor containment is lost.
 
==Capacity and capabilities==
Closed orbits with a perigee of 80 km quite quickly decay and re-enter, but a launch loop would be, in and of itself, not only capable of directly reaching such an orbit; but also of reaching [[Prędkośćescape ucieczkivelocity|escape orbits]], [[Asysta grawitacyjna|Gravitygravity assist]] trajectories past the [[Księżyc|Moonmoon]] as well as other non closed orbits such as close to the Trojan points.
 
To access circular orbits using a launch loop a relatively small 'kick motor' would need to be launched with the payload which would fire at [[apogee]] and would circularise the orbit. For [[Orbitageosynchronous geosynchronicznaorbit|GEO]] insertion this would need to provide a [[Delta-v|Deltadelta-v]] of about 1.6 km/s, for [[LEO]] to circularise at 500 km would require a delta-v of just 120 m/s.
 
Launch loops in Lofstrom's design are placed close to the equator and can only directly access equatorial orbits. However other orbital planes might be reached via high altitude plane changes, lunar perturbations or aerodynamic techniques.
 
==Difficulties of launch loops==
A running loop would have an extremely large amount of energy in the form of linear momentum. While the magnetic suspension system would be highly redundant, with failures of small sections having essentially no effect at all; if a major failure did occur the energy in the loop (1.5×10<sup>15</sup> [[Dżul|Joulejoule]]s or 1.5 petajoules) would be approaching the same total energy release as a small [[nuclear bomb]] explosion (350 kilotons of [[Równoważnik trotylowy wybuchu jądrowego|TNT equivalent]]) but would not emit ionising radiation.
 
While this is a large amount of energy, it is unlikely that this would destroy very much of the structure due to its very large size, and because the energy release would be spread-out over several minutes. Steps might need to be taken to lower the cable down from 80 km altitude with minimal damage, such as parachutes.
Launch loops would be quiet in operation, and would not cause any sound pollution, unlike rockets.
 
Finally, their low payload costs is compatible with large-scale commercial [[turysta kosmiczny|Spacespace tourism]] and even [[space colonisation]].
 
==References==
* [[Megascale engineering]]
* [[Orbital ring]]
* [[Kolejka górska|Roller coaster]]/[[Launch track]]
* [[Winda kosmiczna|Space elevator]]
* [[Space fountain]]
* [[turysta kosmiczny|Space tourism]]
* [[Cyklotron|Cyclotroncyclotron]] - the magnetic fields necessary to deflect the loop are similar to a cyclotron
* [[Belt (mechanical)]]