What is Space elevator: Definition and 50 Discussions

A space elevator is a proposed type of planet-to-space transportation system. The main component would be a cable (also called a tether) anchored to the surface and extending into space. The design would permit vehicles to travel along the cable from a planetary surface, such as the Earth's, directly into orbit, without the use of large rockets. An Earth-based space elevator would consist of a cable with one end attached to the surface near the equator and the other end in space beyond geostationary orbit (35,786 km altitude). The competing forces of gravity, which is stronger at the lower end, and the outward/upward centrifugal force, which is stronger at the upper end, would result in the cable being held up, under tension, and stationary over a single position on Earth. With the tether deployed, climbers could repeatedly climb the tether to space by mechanical means, releasing their cargo to orbit. Climbers could also descend the tether to return cargo to the surface from orbit.The concept of a tower reaching geosynchronous orbit was first published in 1895 by Konstantin Tsiolkovsky. His proposal was for a free-standing tower reaching from the surface of Earth to the height of geostationary orbit. Like all buildings, Tsiolkovsky's structure would be under compression, supporting its weight from below. Since 1959, most ideas for space elevators have focused on purely tensile structures, with the weight of the system held up from above by centrifugal forces. In the tensile concepts, a space tether reaches from a large mass (the counterweight) beyond geostationary orbit to the ground. This structure is held in tension between Earth and the counterweight like an upside-down plumb bob. The cable thickness is adjusted based on tension, it has its maximum at a geostationary orbit and the minimum on the ground.
Available materials are not strong enough to make an Earth space elevator practical. Some sources have speculated that future advances in carbon nanotubes (CNTs) could lead to a practical design. Other sources have concluded that CNTs will never be strong enough. Possible future alternatives include boron nitride nanotubes, diamond nanothreads and macro-scale single crystal graphene.The concept is applicable to other planets and celestial bodies. For locations in the solar system with weaker gravity than Earth's (such as the Moon or Mars), the strength-to-density requirements for tether materials are not as problematic. Currently available materials (such as Kevlar) are strong and light enough that they could be practical as the tether material for elevators there.

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  1. D

    I A "space elevator" extended to Neptune's orbit

    Summary: Achieving speed of light with Earth's rotation Excuse my ignorance, but I think of dumb things. If you theoretically built a strong, lightweight cable that traversed over 2.5 billion miles attached to the rotating Earth, the tip would be traveling at or greater than the speed of...
  2. R

    Space elevator minimum initial speed

    Homework Statement In the far future, humans have built a space elevator as a cheap means of access to space. However before that could be done, a few basic principles had to be worked out. . . a) What is the minimum initial speed (in an Earth-centered inertial reference frame) needed for an...
  3. P

    I Space elevator and Coriolis force

    It seems to me that the concept of a space elevator does not take Coriolis force into account. If the elevator were in built with a space station in geosynchronous orbit and counterweight then there is more to reaching the space station than just climbing the rope. The rope would have to be...
  4. Physics345

    Space Elevator Cable: Physical & Chemical Properties

    Homework Statement a) research the space elevator concept. Consider the environment in which the cable must operate. Recommend two physical and one chemical property that the cable should have. Justify your choices. b) Based on what you have learned about bonding and forces in solids, which...
  5. F

    Calculating the Length of a Space Elevator Rope

    Homework Statement The following task causes me problems: The science fiction writer R.A. Heinlein describes in the novel "Friday" a satellite ("space elevator"), which consists of a long rope, placed directly above the equator. The rope is aligned along the Earth's radius. It moves so that...
  6. F

    Space elevator wondering about torque

    Say you have an elevator that reaches space. I have 2 questions : 1) say a space rock hits the top of the elevator... that would create a torque = force * distance on the ground... Wouldn't it instantly snap from any light force or space junk hitting the top of the elevator? Would the station...
  7. QuestionMark1

    I Is the space elevator affected by lightening, sprites, emf?

    Does a conductor from space to Earth mess with the separation of charges in the solar system?
  8. Charles Kottler

    B Is a lunar space elevator a realistic proposition?

    I recently came across this article (from 2005) outlining a proposal for a lunar space elevator: http://www.niac.usra.edu/files/library/meetings/fellows/mar05/1032Pearson.pdf Their is nothing in the article which stands out to me as being unrealistic, although the cost estimate ($10B) might...
  9. sander2798

    How does the addition of a lift affect the forces on a space elevator?

    Hello everyone, I am trying to find out how space elevators work, but there is one think I can't figure out. Normally, the forces on the countermass and it's tether will be as following, assuming you neglect the gravity on the tether. But now, I put the lift somewhere on the cable (below...
  10. fredey

    What would happen if? you heatsink earth and space

    It is a thought I just thought of with all the wonderful attention that climate change has been getting recently. The thought goes as follows: The world has ever increasing entropy as the whole universe has so. With humans adding to this effect even if green house gases curbed due to this...
  11. L

    Space Elevator Rope: Homework Solution & Equations

    Homework Statement Consider a long rope with uniform mass density extending radially from just above the surface of the Earth to a radius of n'R. Show that if the rope is to remain above the same point on the equator at all times, then n' must be given by n'2+n' = (8 pi G p)/(3 w^2) G is...
  12. Mk

    How Can We Harness the Power of Space Elevators and Atmospheric Electricity?

    Hi PF, I've been tasked with joining a team in Budapest to design an endogenously powered space elevator. I was wondering if I could talk about some concepts with you while I prepare for the 1 month camp. http://copernicus.exosphe.re/ Right now I'm wondering if there is a way I can generate a...
  13. 1

    What's the point of building a space elevator?

    i don't get it, people say that it would be a god sent, but i don't get it, even if you are in space, you still need to travel at escape velocity, so you would still need to accelerate, and building a station on geostationary location is EXTREMELY FAR (i thin it was X3 the diameter of earth...
  14. Troy Barnes

    Why can't we make a space elevator using Quantum Levitation?

    Why can't we make a space elevator out of separate rings that are stacked over each other through Quantum Levitation? You know, have hollow rings that are quantum locked over each other, like in this video That way, the ladder freely moves around and changes shape, but would still be "intact"...
  15. W

    How much gravity could a space elevator survive?

    No matter how strong and how light the materials are, it seems that a space elevator is an insurmountable engineering challenge on Earth under 1G of gravity. However that is because the gravity on Earth is too much for a space elevator to survive, given a somewhat modest estimation of...
  16. U

    Can a Balloon Float Inside a Hollow, Air-Filled Space Elevator?

    What would the problems be with having a hollow cylindrical space elevator made of carbon (e.g. recent benzene linked chains) and instead of having the payload climb to the top you filled the inside with 1 ATM of air and floated to the top via balloon?
  17. O

    Can Magnetic Hoops Create a Space Elevator to Geo Orbit?

    Would it be possible to have a stack of thin magnetic hoops that, when energized, space out from each other to reach geo orbiit Kinda like a magnetic slinky?
  18. R

    Space elevator problem: how long is the cable?

    Homework Statement "Consider a cable, of fixed mass per unit length, which extends radially from just above the surface to a distance ηR measured radially from the center of the Earth. By determining the total force on the cable, or otherwise, find an expression and numerical value for η. At...
  19. P

    Near earth Asteroids and a space elevator

    Ok so this is silly and purely hypothetical... I am under the impression that should we ever decide to construct a space elevator we would need a pretty large mass on the space side of things. and that is one of the hurtles to making one. I am wondering if we have the capability to...
  20. R

    .Understanding Stress on Space Elevator

    i am not able to understand how, where and why stresses will act on the space elevator considering it to be a rope or ribbon, i mean to ask that if we make a free body diagram of the space elevator then where and in which direction forces will act on it. and why that forces will act as they...
  21. V

    Space Elevator: Magnitized Cable for Supersonic Travel

    Everyone has heard of the space elevator using a cable(s) that attaches to a geosynchronus satellite. Now trying to lift things is always a very energy expensive process, since just making a payload weightless cost energy and you get zero velocity and travel. Also how fast could an elevator...
  22. E

    How would I go about creating a computer simulation for a Space Elevator?

    I want to create a computer simulation of the Space Elevator, simulating if different materials would be able to handle the tension, and whether the whole thing would be able to function efficiently through the gravitational field. Anyone how I can go about doing this, and what software to...
  23. B

    Instead of a space elevator a well

    Instead of a space elevator I would like the thoughts on a well. Create a structure from Geo orbit to a altitude where a the atmosphere is thick enough to harvest . Pump the gases to a altitude where it is most practical to processing the gases for shipping. I would like to think of spinning...
  24. A

    Momentum and Energy Conservation of a Space Elevator

    I want to know what exactly is the free-electron laser power beaming system that will be used in our future Space elevator and how the conservation of energy and momentum is associated with this project that NASA will launch. ? Other info: I am taking grade 12 university level physics; All...
  25. Eagle9

    Releasing the object from Space Elevator

    Let’s imagine that the Space Elevator is built and we ascend to space with its cabin. The cabin stops temporarily at the altitude of 100 km (or a bit more) and then we release some object (sphere, hemisphere) downwards, the question is: what trajectory will it (object) follow when falling down...
  26. Algr

    Skyhook - is this better then space elevator?

    Hi Physics Forum! I've been reading about the space elevator and the amazing feat of running a cable past geosynchronous orbit. It occurred to me that there might be an easier way. I may have heard about this somewhere ages ago, or maybe I made it up, but I haven't been able to find any...
  27. B

    Energy savings with space elevator

    Hi I read in a paper that the enrgy saving in taking a payload to geostaionary orbit with a space elevator is (R/Rg)*(2-R/Rg) where R- radius of earth, Rg - radious of geostaionary orbit. How is this obtained ? TIA
  28. B

    Energy savings with space elevator

    Hi I read in a paper that the enrgy saving in taking a payload to geostaionary orbit with a space elevator is (R/Rg)*(2-R/Rg) where R- radius of earth, Rg - radious of geostaionary orbit. How is this obtained ? TIA
  29. K

    Tensions in the space elevator

    Homework Statement I am tasked to summarise this paper http://chaos.swarthmore.edu/courses/PDG07/AJP/AJP000125.pdf I am struggeling to understand the statements of tension at the bottom of the first side namely For an element at geostationary height that is, at a distance from the...
  30. M

    Force on a Swinging Rod (space elevator)

    This is part of the space elevator problem. It starts with a swinging rod scenario: 1. Suppose that you swung a rod of mass m and length l at angular speed w in a vertical circle with your shoulder as the axis. The distance ra is the length of your arm, which is the distance from the bottom...
  31. S

    Space Elevator Questions and What Ifs

    Suppose the classic elevator is created, affixed to the Earth somewhere on the equator. The elevator would be perfectly balanced so that there would be no net force i.e. the centrifugal force of the string and end station would equal the force of gravity. What would happen if the cord was...
  32. edpell

    Space Elevator on the Moon: Why is Nobody Building It?

    Building a space elevator for the moon seems doable with existing materials (see the wikipedia page). So my question is why is no country or organization interested in building one?
  33. D

    Space Elevator: Carbon Nanotubes, Lasers & Beamed Energy

    The tether generally proposed for a space elevator is usually made of carbon nanotubes. However, the lifters themselves are usually powered by lasers or some type of beamed energy. Two questions: 1. Carbon nanotubes can be very good conductors, why can't they be used to conduct electricity...
  34. R

    Space elevator ? How can it work?

    I have been reading about the so called "SPACE ELEVATOR" in various articles in the news papers and magazines and reading that in a contest recently a company won a $900,000. prize as their creation climbed a mile long cable suspended from a helicopter in under 4 min. I understand that this...
  35. Pattonias

    A hypothetical space elevator question.

    I am a fledgling undergrad with a potential mechanical engineering degree in my future. I just have a hypothetical question about the space elevator that yall may be able to help me with. I have not taken my physics courses yet so forgive my limited working knowledge of the material. If you...
  36. N

    Space Elevator Vehicle: Acceleration After Cable Release

    Say you have a space elevator 47000 km* long (well past the point where centripetal acceleration cancels out gravity) There is a vehicle traveling up the cable with a pretty high velocity, and instead of braking it just shoots off the top. (assume the counter weight allows this) At the...
  37. J

    Space Elevator: Physics Challenge

    Space Elevator Your first job after graduation you are hired by a engineering firm that just got a contract to build the first space elevator. The space elevator consists of a cable hanging from geo-stationary satellite to an anchor point on earth’s surface. Once installed this equipment can...
  38. N

    Space Elevator Tether: The Importance of a Round Design

    I think there has been floated the idea that the space elevator tether may be a ribbon. I think it will fail if it isn't round. I think it will twist with the wind, it will twist in different directions at different altitudes, the twisting will change it's length dramatically and it will break...
  39. L

    Space Elevator and Centrifugal Force

    I was thinking about the Space Elevator idea, and I think most of us can agree that as one goes higher up the the tower, the pull of gravity gets weaker and "centrifugal force" gets stronger (compared to one another), until the altitude of geosynchronous orbit, where the two become equal. So...
  40. B

    Lunar Space Elevator: Is a Rocketless Trip Possible?

    Lunar space elevator... Based on my limited understanding of the idea. If this system were to omit a rocket or chemical propellant power plant and is not an unbound free traveling vehicle, I would infer, given the distance of the journey the travel time may venture into the realm of the...
  41. S

    Space Elevator - Your take on an exam question

    I recently had an exam in my 2nd year dynamics course that included a question concerning a Space Elevator. My view on this question (or the answer to this question) seems to be different than my instructor's. I was hoping to get some of your thoughts so I could get a better understanding...
  42. S

    What's the Latest on Space Elevators?

    http://www.newscientistspace.com/article/dn8725" Jolly Cool.
  43. E

    Einstein's space elevator and the twins paradox

    A PBS program said that the theory of general relativity holds acceleration and gravity observationally equivalent. (Einstein's space elevator example was given.) Here is a thought experiment based on that mental picture. A "gravity switch" will make the following thought experiment easier to...
  44. W

    Space Elevator to Solve World's Energy Shortage

    If carbon nanotubes are great conductors, and if a wire moved through a magnetic field generates electricity, then a space elevator constructed out of carbon nanotubes should be able to generate a lot of electricity. Maybe too much. I think the carbon nanotubes would melt. Indeed, if there...
  45. S

    Space Elevator on Mars: Feasibility, Design Issues & Vibration

    How feasible is the idea of making a space elevator on Mars? What are the design issues? Will the swaying and vibration problems be of the same magnitude as earth?
  46. L

    NASA Space Elevator Feasibility: NASA Announces New Launch Vehicle and CEV

    Yeah, they'll have those right after they have satellites that can scratch your ass with a laser beam from space. Cheers...
  47. A

    Can a space elevator be stabilized without reaching geostationary orbit?

    Hi. This may be really basic, but would appreciate your help. Is a tower whose height reaches a geostationary orbit at 35,000km's altitude or so more stable that one which doens't quite reach that height? So, say you are building a tower, decide you'd like it more stable, so should you go...
  48. M

    Space elevator and ionoshphere

    space elevator and ionosphere would a space elevator short circuit the 250,000 volt difference between the Earth and the ionoshere making it dangerous?
  49. M

    Your weight on a Space Elevator ?

    Your "weight" on a "Space Elevator"? I'm not sure the term "Space Elevator" is widely used, and outside of those who've read Clarke's THE FOUNTAINS OF PARADISE I'm not sure the term would mean much to many, so by way of an overly simplified description of the term... You put a big rock in...
  50. Ivan Seeking

    Scientist Sees Space Elevator in 15 Years