Space elevators have to be verry long (35,786 km) to reach geostationair orbits, and they need to reach GEO because they need a fixed point on the ground. Would it be possible for example to build a "air carrier" (sort of zeplin) That circles the earth in (example 24hours) so in combination with the earths own rotation it would only need a MEO orbit ad 10,058 km to be stable (less then 1/3th of the original space elevator. The "air carrier" itself could if necesairy be connected with 2 cables to fixed anchor points acros the equator making sure it's anckored at all times. Those cables would have to be rather long and be vornable to wear and tear but it might be worth the extra costs
The airflow at these altitudes generally are always the same. and quit fast if you would take anough with those winds youl probably could turn a 24 hour rotation to near 20 and then their would be no air drag.
Wind speeds are different at different altitudes though. I'd imagine the elevator would buckle. They will never be able to make it strong enough without it taking up half a continent.. lol. Then theres hurricanes.. And what about ice formation ?
Long is right. NASA has 2 in mind. one is a light propelled idea, for equipment since the speeds there suggesting would pulp any biomass inside. The second is a "rope" that would take 2 weeks or more to transverse. Talk about the stairway to heaven if anything goes wrong. I think NASA looked into and rejected your suggestion, a simple search in the NASA archives would tell you why.
They actually have to reach past GEO, because the center of mass for the enitre structure has to be at least as high as GEO, preferably higher.
I never really understood the whole space elevator thing. A space elevator wire or beam cound no way withstand the bending moment. You need something of virtually infinite stiffness. Comeon, It's easier to just pile dirt on top of Mt. Evererest until it's 200 miles high.
if you could do it with air breathing rockets then that's fine but that will be the last mayor inprovement possible with chemical rockets then it's a death end afther that it will probably talk nuclair energy to get in orbit witch would start to become dangerous Then again this ID might not even be possible
You don't want something stiff, just something with a high tensile strength. The cable is basically just "hanging" down under its own weight from a center of mass that's in geostationary orbit. But then you would just be up really high; you wouldn't actually have any velocity. The real purpose of a space elevator isn't to get you up really high, it's to impart velocity on you as you ride up it. By the time you get to the top, you will have enough velocity that you are in orbit, and can simply step out of the elevator without falling.
I think if you would make a graph abouth the evolution of tensile strength then the result would be very promising for a practical space elevator in the first 50 years or so. In the end the ID is more realistic then to ad a 100 000kg rocket to a ram/scramjet that could never have the lift to carry it's load and power source never mention the effect of the multi G's on them, the launcher probably desintigrates the moment the heavier rocket comes loose
The thing is, you're probably never going to be able to fit enough mass of equipment into any conventional single-stage spaceship to actually do anything big in space (like build a colony, a mine on another planet, etc.) It's fine for little science missions or even "Hey, we got a few people here!" type exploration missions, but it's not enough to really industrialize space or take advantage of its resources.
some time ago some man named Bradley C. Edwards calculated a space elevator would need a minimal tensile strength of 130 GPa (including a safety factor of 2). As of now no nano tubes have exceeded either 52 or 63 GPa depending on the type. Now Recent research by James D. Iverson and Brad C. Edwards has revealed the possibility developing nano tubes of 138 GPa, for 106 MN·m/kg. Could this mean it is strong enough? So the only drawback is the lenght and the cost, or will it most likly never reach this strength because the predictions are to optimistic either way ones this milestone is reached 2010 might still be imposible but there would be a change that their is a space elevator before their is a mannend mission to mars. source
You'd have so many variables. wind/ sunlight/weather damage at higher levels. the cables would cast shadows miles long over countries, the cables themselves would have to be made of a really flexible yet strong matierial.
That would not be practical such cables could never hold their own weight. For it's use the cable has to be at least 35 790 000 meters long but it can be as thin as paper so there would hardly be any shadow. I believe if you lived further then 1 km of a space elevator you would never even see it directly altough higher up water could condense near it. The biggest threat would either be the high amount of oxygen and resulting corrosion and micrometeorites. The oxygen problem can probebly be solved by adding a special coating the first few kilometers there would most defenitly not be any corrosion above 80 km what leaves micrometeorites. Perhpas that can be solved by a multitude of cables and banning most low earth satelites or debris hazards
[edit] Failure cascade It is not enough that other fibers be able to take over the load of a failed strand — the system must also survive the immediate, dynamical effects of fiber failure, which generates projectiles aimed at the cable itself. For example, if the cable has a working stress of 50 GPa and a Young's modulus of 1000 GPa, its strain will be 0.05 and its stored elastic energy will be 1/2 × 0.05 × 50 GPa = 1.25×109 joules per cubic meter. Breaking a fiber will result in a pair of de-tensioning waves moving apart at the speed of sound in the fiber, with the fiber segments behind each wave moving at over 1,000 m/s (more than the muzzle velocity of a standard .223 caliber (5.56 mm) round fired from an M16 rifle). Unless these fast-moving projectiles can be stopped safely, they will break yet other fibers, initiating a failure cascade capable of severing the cable. The challenge of preventing fiber breakage from initiating a catastrophic failure cascade seems to be unaddressed in the current (January, 2005) literature on terrestrial space elevators. Problems of this sort would be easier to solve in lower-tension applications (e.g., lunar elevators). [edit] Corrosion Corrosion is a major risk to any thinly built tether (which most designs call for). In the upper atmosphere, atomic oxygen steadily eats away at most materials. A tether will consequently need to either be made from a corrosion-resistant material or have a corrosion-resistant coating, adding to weight. Gold and platinum have been shown to be practically immune to atomic oxygen; several far more common materials such as aluminum are damaged very slowly and could be repaired as needed. Another potential solution to the corrosion problem is a continuous renewal of the tether surface (which could be done from standard, though possibly slower elevators). This process would depend on the tether composition and it could be done on the nanoscale (by replacing individual fibers) or in segments. [edit] Radiation The effectiveness of the magnetosphere to deflect radiation emanating from the sun decreases dramatically after rising several earth radii above the surface. This ionizing radiation may cause damage to materials within both the tether and climbers. [edit] Material defects Any structure as large as a space elevator will have massive numbers of tiny defects in the construction material. It has been suggested,[37][38] that, because large structures have more defects than small structures, that large structures are inherently weaker than small, giving an estimated carbon nanotube strength of only 24 GPa down to only 1.7 GPa in millimetre-scale samples, the latter equivalent to many high-strength steels, which would be vastly less than that needed to build a space elevator for a reasonable cost. [edit] Weather In the atmosphere, the risk factors of wind and lightning come into play. The basic mitigation is location. As long as the tether's anchor remains within two degrees of the equator, it will remain in the quiet zone between the Earth's Hadley cells, where there is relatively little violent weather. Remaining storms could be avoided by moving a floating anchor platform. The lightning risk can be minimized by using a nonconductive fiber with a water-resistant coating to help prevent a conductive buildup from forming. The wind risk can be minimized by use of a fiber with a small cross-sectional area that can rotate with the wind to reduce resistance. Ice forming on the cable also presents a potential problem. It could add significantly to the cable's weight and affect the passage of elevator cars. Also, ice falling from the cable could damage elevator cars or the cable itself. To get rid of ice, special elevator cars could scrape the ice off. [edit] Vibrational harmonics A final risk of structural failure comes from the possibility of vibrational harmonics within the cable. Like the shorter and more familiar strings of stringed musical instruments, the cable of a space elevator has a natural resonant frequency. If the cable is excited at this frequency, for example by the travel of elevators up and down it, the vibrational energy could build up to dangerous levels and exceed the cable's tensile strength. This can be avoided by the use of suitable damping systems within the cable, and by scheduling travel up and down the cable keeping its resonant frequency in mind. It may be possible to dampen the resonant frequency against the Earth's magnetosphere. [edit] In the event of failure If despite all these precautions the elevator is severed anyway, the resulting scenario depends on where exactly the break occurred: [edit] Cut near the anchor point If the elevator is cut at its anchor point on Earth's surface, the outward force exerted by the counterweight would cause the entire elevator to rise upward into an unstable orbit. The ultimate altitude of the severed lower end of the cable would depend on the details of the elevator's mass distribution. In theory, the loose end might be secured and fastened down again. This would be an extremely tricky operation, however, requiring careful adjustment of the cable's center of gravity to bring the cable back down to the surface again at just the right location. It may prove to be easier to build a new system in such a situation. [edit] Cut up to about 25,000 km If the break occurred at higher altitude, up to about 25,000 km, the lower portion of the elevator would descend to Earth and drape itself along the equator east of the anchor point, while the now unbalanced upper portion would rise to a higher orbit. Some authors (such as science fiction writers David Gerrold in Jumping off the Planet, Kim Stanley Robinson in Red Mars, and Ben Bova in Mercury) have suggested that such a failure would be catastrophic, with the thousands of kilometers of falling cable creating a swath of meteoric destruction along Earth's surface; however, in most cable designs, the upper portion of any cable that fell to Earth would burn up in the atmosphere. Additionally, because proposed initial cables (the only ones likely to be broken) have very low mass (roughly 1 kg per kilometer) and are flat, the bottom portion would likely settle to Earth with less force than a sheet of paper due to air resistance on the way down. If the break occurred at the counterweight side of the elevator, the lower portion, now including the "central station" of the elevator, would entirely fall down if not prevented by an early self-destruct of the cable shortly below it. Depending on the size, however, it would burn up on re-entry anyway. Simulations have shown that as the descending portion of the space elevator "wraps around" Earth the stress on the remaining length of cable increases, resulting in its upper sections breaking off and being flung away. The details of how these pieces break and the trajectories they take are highly sensitive to initial conditions.[39] http://en.wikipedia.org/wiki/Space_elevator
Anyone ever heard of space fountains? It seams a much safer and practical option. It could even be constructed with current technology. Tensile strength would not be as much of a factor. I can't post the link yet, but search for space fountain on wiki and Enjoy!
[edit] History The concept originated in a conversation on a computer net in the 1980s when some scientists who usually work in artificial intelligence, Marvin Minsky of MIT and John McCarthy and Hans Moravec of Stanford, were speculating about variations on the skyhook concept with some scientists at Lawrence Livermore National Laboratory who usually work on laser-initiated fusion, Roderick Hyde and Lowell Wood. As a means of supporting the upper end of a traditional space elevator at an altitude much less than geostationary, they proposed a ring of space stations hovering 2000 kilometers above Earth, motionless relative to the surface. These stations would not be in orbit; they would support themselves by deflecting a ring of fast-moving pellets circling Earth. The pellets would be moving at far greater speed than the orbital velocity for that altitude, so if the stations stopped deflecting them the pellets would move outward and the stations would fall inward. Robert L. Forward joined the conversation at this point, suggesting that instead of using a pellet stream to support the top of a traditional tensional cable, a vertical pellet stream shot straight up from Earth's surface could support a station and provide a path for payloads to travel without requiring a cable at all. Problems that were initially raised with this proposal were friction of the pellet stream with Earth's atmosphere at lower altitudes and the Coriolis forces due to the rotation of the Earth, but Roderick Hyde worked out all the engineering design details for a Space Fountain and showed that there were no show-stoppers.[1] [edit] Design The Space Fountain acts as a continuous mass driver with captive projectiles travelling in a closed loop. Hyde designIn the Hyde design for a Space Fountain a stream of projectiles is shot up through the bore of a hollow tower. As the projectiles travel upward through the tower they are slowed down by electromagnetic drag devices that extract kinetic energy from the upgoing stream and turn it into electricity. As the projectiles are braked they also transfer some of their upward momentum to the tower structure, exerting a lifting force to support some of its weight. When the projectiles reach the station at the top of the tower they are turned around by a large bending magnet. In the turnaround process they exert an upward force on the station at the top of the tower, keeping it levitated above the launch point. As the projectiles travel back down the tower they are accelerated by mass drivers that use the electrical energy extracted from the upgoing stream of projectiles. This provides the rest of the upward lifting force required to support the weight of the tower. The projectiles reach the bottom of the tower with almost the same speed that they had when they were launched, losing a small amount of energy due to inefficiencies in the electromagnetic accelerators and decelerators in the tower. This can be minimized by the use of superconductors.[2]
