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Space Elevator


Published on Jan 28, 2016

Abstract

The story of Jack and the Beanstalk is starting to sound more and more plausible every day. A huge, tall structure comes out of the ground and goes straight up through the clouds; at the end is a wonderful, mysterious castle. Experts agree that the biggest drain of energy takes place when a vehicle blasts off, pushing through Earth's gravitational pull requires great amounts of fuel, but once they get out of our atmosphere, the rest is easy.

If you could cut out that "blast off" portion, space travel would be easier and much more fuel-efficient.

In a Space Elevator scenario, a Maglev vehicle would zoom up the side of an exceedingly tall structure and end up at a transfer point where they'd then board a craft to the Moon, Mars, or any other distant destination. If it all sounds like too much science fiction, take a look at the requirements for making the Space Elevator a reality. A new material has been developed, however, called carbon nanotubes, that is 100 times as strong as steel but with only a fraction of the weight. A carbon nanotube is an idea that makes this all sound much more achievable.

In this concept, which is very fuel efficient and which brings space tourism closer common man uses the newly added concept of nanotubes to light.

CHALLENGES FACED BY SPACE ELEVATOR

The major challenges faced for bringing this concept to light are

Atmospheric issues

Lightening, clouds, winds. Historic data maps shows lightening occurs a land masses ,less on mountains and least along equator, further experimental cables don't attract lightening ,winds aren't a factor since it is capable of withstanding wind spend of 71m/hr and hurricanes not a problem since they form and travel outside the equatorial region.

Impact or Collision

Big issues requiring more study .Debris is monitored using radar. Stud between Debris and meteors indicate space debris to be more hazardous .It must be noted number of impacts on ribbon, not as important as degradation cost due to impact.

Health issues

Fiber health focuses on three things, dose, dimension and durability .The bigger ones can't be integrated and smaller ones appear to dissolve quickly.

DIFFERENT CONCEPTS

LOW EARTH ORBIT CONCEPT

The LEO space elevator is an intermediate version of the Earth surface to GEO space elevator concept, and appears to be feasible today using existing high-strength materials and space technology. It works by placing the system's midpoint station, and center of gravity, in a relatively low-Earth orbit and extending one cable down so that it points toward the center of the Earth and a second cable up so that it points away from the Earth. The bottom end of the lower cable hangs down to just above the Earth's atmosphere such that a future space plane flying up from the Earth's surface would require 2.5 km/sec less change in velocity than a single-stage-to-orbit (SSTO) vehicle launched directly to LEO.

The space plane and LEO space elevator combination would likely be able to carry 10 to 12 times the payload as an equivalent-sized SSTO launch vehicle without the LEO space elevator. The length of the upper cable is chosen so that its endpoint is traveling at slightly less than Earth escape velocity for its altitude. This is done so that a spacecraft headed for higher orbit, the Moon, or beyond, can be placed in the proper orbit with only minimal use of its onboard propellant.

Space Elevator

The overall length of a LEO space elevator from the bottom end of its lower cable to the top end of its upper cable is anywhere from 2,000 to 4,000 km, depending on the amount of launch vehicle velocity reduction desired. It should be possible to launch a LEO space elevator in segments using existing launch systems. Once on orbit the LEO space elevator would then use its own onboard propulsion system to raise itself to the necessary orbital altitude while reeling out the upward and downward pointing cables as it went.

Another advantage of this system is that as the market expands and materials improve, it could continue to grow in length and diameter, further reducing launch velocity and increasing system payload capacity. It even appears possible to grow the LEO space elevator into the full-length, 35,000-km-plus space segment length of the Earth surface to GEO space elevator if that were desired. The fact that it is a freely orbiting system and not attached to the Earth at its lower end allows the system to be placed in an inclined orbit aligned with the plane of the ecliptic. This has advantages for traveling to the Moon and other planets as it would avoid plane change maneuvers and would greatly increase the number of launch windows for a given timeframe.

Another advantage of the inclined orbital plane is that if a resonant orbit is used, the lower end of the system will pass within range of most of the world's major airports twice a day on a fixed schedule. Once the velocity required to reach the lower end of the LEO space elevator is down to the Mach 16 range or less, horizontal takeoff and landing space planes operating out of those airports appear to become both technically and feasible economically feasible.

3.2 Lunar Space Elevator Concepts

Another near-term application of the space elevator concept could be demonstrated at the Moon. The one-sixth gravity at the Moon makes it theoretically possible to construct tethered connections from the surface of the Moon to the LaGrange libration points L1 and L2, on the near and far side, respectively, using existing materials (Kevlar, Spectra, or PBO graphite epoxy).

It has been envisioned that on the near side of the Moon such a structure could become the transportation system for moving materials to L1 in support of solar-powered satellite construction and propellant storage platforms. The regolith located at the base of the elevator contains oxygen which could be extracted. Additional gases from ice deposits at the lunar poles might also be transported around the Moon to this point for transfer to L1. At L1, solar-powered satellites would become part of a space utility system for production and transfer of power to the surface of the Moon and other stations within the Earth/Moon system. Likewise, a propellant platform at L1 would act as a service station for reusable in-space transportation vehicles.

On the far side of the Moon at L2, a similar system could be envisioned for lunar and space infrastructure support. On the surface of the far side of the Moon, ideas have been proposed for large space observatories, and as a remote location for the long-term storage of hazardous materials like the nuclear waste generated on Earth that must be stored safely for thousands of years.














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