Space elevator vs Moon elevator

Discussion in 'Architecture & Engineering' started by icarus2, May 30, 2010.

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  1. icarus2 Registered Senior Member


    Few years ago, I tried to think on methods to transport freight and humans to space economically and safely. I thought at that time, moon elevator could be created if powerful cable can be produced from development of carbon nano-tube technology. Through moon elevator, space development of mankind, commercial travel to space and moon will become possible, and contribute enormously to development of human civilization.

    Please have a look at the following introduction of basic concepts, and compare relatively with "space elevator" and its feasibility etc

    [Moon Elevator]

    【Brief explanation on Figures】
    Figure 1 is structure diagram of moon elevator

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    Figure 2 is plane figure seen from perpendicular of lunar orbit plane

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    Figure 3 is structure diagram of multiple moon elevators

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    【Purpose of invention】
    This invention is about transport method of freight and humans to space using rocket and space shuttle. More specifically, a cable is put on the moon toward the earth, so the moon acts as a ceiling with a cable hanging down. Although position changes at all time due to moon moving around the earth, using the property that this cable will always face toward the center of the earth because of earth gravity will allows an elevator to move on this cable.
    Currently the only method to go out to space from the earth is by using rocket or space shuttle, and since space shuttle uses exterior rockets to obtain propulsive force to go out to space, rocket is the only present method.

    However, escaping earth by using these rockets has many problems.
    First, solid fuel and liquid fuel etc that are used for rocket fuel are extremely high explosive materials. Little mistakes or problems while using these fuel types could lead to deadly accidents, as example, Challenger explosion accident or Columbia explosion accident etc.

    Second, in order for a rocket to head out to the space through self-propulsion, it takes off from launching pad with enormous amount of fuels. To increase efficiency of fuel, most of the fuels on the rocket are used at the initial stage of take off, thus maintaining very fast speed. However, because it passes through the atmosphere at very high speed, air friction and collision with outside material damages body of the rocket frequently and safety system in preparation for these damages causes problem of increase in weight and fuel amount of rocket body.

    Third, the most crucial problem is that current rocket launching cost is commercially too expensive. Because of its high cost, space exploration or moon exploration using rockets has become a project performed by nations, and due to high cost, the only nation that has accomplished landing on the moon is United States. These high costs are acting as an obstacle in moon development, space exploration and launching artificial satellites etc…

    【Technical task achievement through invention】
    The aim of this invention is to present safer and inexpensive transport method of freight and humans to space than existing rocket method and the goal is not only transporting freights needed for moon development but also transporting extracted resources from moon to earth efficiently.

    【Invention structure】
    Figure 1 is a diagram that shows the final outcome of this invention, a cable (103) is suspended from moon (100) toward the earth (101), elevator (102) is attached to the cable (103), and this elevator (102) operates from the earth surface to space or moon (100) to transport freight or humans to space.
    Composition elements of moon elevator (102) are solar power plant (105) that is constructed on the moon (100), motor (106) that pulls the cable (103), cable (103) that can withstand the weight of elevator (102) and freights and elevator (102) that can operate by obtaining power externally or internally.
    For power plant (105), solar power plant (105) or other fuel type power plant (105) can be installed to operate the motor (106), and electric power can be transmitted to moon when cable (103) connects the earth (101) and the moon (100) and this power can be stored for later use.

    Construct moon (100) base on the surface of the moon (100) where it is closest to the earth (101) and distance change between earth (101) and moon is the minimum, and construct power plant (105) to supply power and motor (106) to operate the cable (103). For case where elevator operates itself by power supplied, cable does not need to be operated by motor directly.

    Construct a structure underneath the moon (100) and after tying up one end of the cable (103) to the structure, launch the rocket with the cable so cable points toward the earth.

    From locations of earth surface where earth gravitation direction (201) of the cable (103) meets, construct earth base where accessibility is ease, affect on flight service of plane and weather is low and location is close to the moon (100).

    When cable (103) suspended from moon (100) reaches the earth base, install the elevator (102) located at the earth base. To maintain the cable in straight line, install weight and communication equipments for ground base etc at the end of the cable.

    On the elevator (102), embark freight and human that will be transported to moon (100) or space.

    Supply power to the elevator (102), transport freight and human to locations by ascending and descending the elevator (102) or by pulling the cable directly to pull up the elevator from the space base located at the middle.

    As seen in Figure 1, moon (100) performs as a ceiling (211), and although one end of the cable (103) is not tied up to the surface, cable (103) is pulled tightly in perpendicular due to gravity (213) on the cable (103), so the elevator(102) on the cable (103) is able to move upward. Similarly, even if the cable (103) is floating on air, it would perform similarly to cable(103) hanging on the ceiling (211) due to gravity from the moon (100) and the earth (101) and direction of the cable (103) rotates in 360 degree because the moon rotates around the earth, but due to characteristics of gravity, it will always point upward as the earth surface as base, so it can perform necessary role to head out to space from the earth surface.

    Figure 2 is a plane figure of this invention seen from perpendicular of lunar (100) orbit plane (205). Due to affect from rotation of the earth (101) and moon’s (100) revolution affect around the earth (101), it takes approximately 27.32 days for moon (100) to revolve around the earth (101) once. These revolution cycles of the moon (100) as to revolution-side of the moon (100) that meets with surface of earth (101) shows angle changes of approximately 13.36 degree a day, and in time unit, shows less than one degree per hour, 0.56degree/hour. Thus cable that is suspending from the moon stays on top of earth base for a certain time, providing enough time for the elevator to load and unload the freights. Of course the speed of cable on the earth surface due to revolution of the moon is relatively huge but expects embarking freight and passenger is technically possible.

    There is some distance difference between closest and farthest location because to be exact, the moon (100) rotates in oval orbit, not in circle. The most appropriate location to build earth base on the earth surface is where the moon is the closest or select location where revolution surface meets the earth surface with minimal obstacle elements and ease to access considering land features of circumference, accessibility, climate, plane operation situation etc, with location where moon is close by. At this point, earth gravitational direction of the cable suspending from the moon is necessary to consider.

    As seen in Figure 2, cable (103) and elevator (102) suspending from the moon (100) is affected by the earth (101) gravity so it is always perpendicular to the surface, whether the moon (100) is in three o’clock direction(303), six o’clock direction(302) or at ten o’clock direction(301). The mass of the moon (100) or mass of the earth (101) are much greater than the mass of elevator (102) or freight inside the elevator (102), so affect on moon (100) and earth (101) by the movement of cable (103) or elevator (102) and freight mass can be ignored.

    Figure of three o’clock direction (303) is when elevator (102) is located at the moon (100). Elevator (102) can transport freight or human from the earth (101) or transport extracted resources from the moon (100) to earth (101) using the elevator (102).

    Figure of six o’clock direction (302) is when elevator (102) reached the geostationary satellite orbit (206). Instead of firing up satellites from the earth surface, elevator (102) can be used to transport satellites to the geostationary satellite orbit (206) and these satellites can be placed on its proper orbit using self-propulsion fuel from geostationary satellite orbit (206). If satellites can be transported using moon (100) elevator (102), not only satellite can be transported to precise height but it will also extend the life span of the satellites by more couple of times than current method because it can be transported with enough fuel of its own.

    Figure of ten o’clock direction (301) is when moon elevator (102) reached the transport center, known as earth base (300) located at earth (101). At this moment, freight and human can be loaded or unloaded from the elevator (102) and supply power to elevator (102) and the moon (100). Communication equipment (208) is installed at the end of the cable (103) to communicate exact position and height etc information with earth base (300), and perform role as a weight.

    As shown, there is no danger of explosion using moon elevator (102), although it does have a possibility of fall, but it can escaped using parachute etc inside troposphere and also when emergency situation occur, it has some time to figure out the problem compared to explosion, so this is much more safer method compared to using rockets.
    Furthermore, to construct habitable space and live on the moon while developing moon and extracting resources, vast amount of materials are needs to be transported but using current rocket method has considerable constraint and cost problem. However using this invention, vast amount of materials can be transported to moon (100) inexpensively and also transport extracted resources from moon to earth easily. When exploiting resources like helium3 on the moon (100), transport method needs to be ready at all time, thus moon elevator (102) will be utilized very usefully for these development.
    Although there are high priced space-travel plans available now, if moon elevator (102) gets installed, cheaper space travel will become possible, achieving commercial success, and can also be utilized for uses like launching artificial satellite and various exploration vessels.

    Figure 3 shows an object produced by applying core concept of this invention. It is a multiple elevator (102) system that uses space base (107) that is connected with the moon.
    Unlike from previous space base, this invention does not exhaust fuel from rotating after when it is installed, ease in transporting material and human to earth, able to conduct various types of experiment by adjusting the position of the space base and is able to adjust height.

    Construct space base (107) as in this plan, install motor (133) inside the space base (107) to transport freight and human on earth to space, this is a bit more efficient compared to operating the elevator (102) by using the motor (106) installed at the moon (100). Suppose cable1 (131) is pulled by activating motor (106) located at the moon (100), entire cable (131,132) needs to be pulled but if motor (133) installed at space base (107) is operated, energy can be saved by only operating cable2 (132), from space base (107) to earth surface. Space base (107) can be used for space experimental lab and tourist uses etc. As mentioned before, if elevator can operate itself from self-power or transmitted power, it is better for the elevator itself to move rather than pulling the cable up.

    Construct numerous space bases, such as moon base, geostationary orbit base, 100km upper sky base etc by expanding multiple elevator system to transport human and materials between sections and use it for various uses (moon base- transport moon resources and commercial travel, geostationary orbit- space station and execute artificial satellite launch and commercial travel, 100km base- commercial travel etc).

    Movement between corresponding sections in the multiple elevator system can be operated by technically ease method, either pulling the cable directly to move the elevator or elevator itself can move up and down following the cable by self-power or transmitted power.

    【Effect of invention】
    As described above, this invention can install cables in air with no support put on the surface, and even though the earth rotates, this cable always maintain on top of the surface due to characteristics of gravity. This invention does not have danger of explosion and is considerably safe compared to methods that use rockets. Also it uses electric energy as source power so it is eco-friendly compared to fossil fuels. This invention can be applied to satellite launch and space exploration etc, which still has quite a lot of demand, and can be used as very useful tool for moon exploration and transporting resources located at the moon. And can provide cheaper method of commercial space travel and moon travel than previous method.

    My idea also has some drawbacks.
    Drawbacks are that distance between moon and earth is extremely far, and will it be possible to manufacture strong cable like carbon nano tube to reach other and will it have enough tensile strength? The key is if sufficient tensile strength is achieved through development of technology, length of the cable is not a big problem because it only needs funds, and I think the cost of development can be sufficiently supplied through resource exploit from the moon, executes artificial satellite launches, and commercial space travel demand etc.

    Although my idea has some drawbacks, I believe that my idea is much more stable, ease in technology, and can be used in multipurpose than space elevator. And it has a merit that only if cable related technology is achieved, moon elevator can be developed easily with current technology.

    Regardless of existing space elevator’s high possibility, it seems it has several drawbacks of instability elements, technical difficulty and increase in transportation cost etc.

    First, even though earth base is located where climate affect is minimum because the cable is always linked between space and earth base, enormous power is applied to the cable by the movement of the atmosphere and to keep the cable connected with space and earth base, couple more times of cable tension than normal connection is required and dangerousness will increase largely due to movement of the atmosphere.
    ==> Moon elevator technology: Cable is not tied up with earth base, so danger from atmosphere and tension increase of cable is relatively low because of flexible condition.

    Second, even though space base does not lose additional energy due to its location at geostationary orbit, cable connected from the earth base is continuously forced and in result, space base is forced downward pulling, so energy is exhausted continuously to propulsion the space base to maintain its orbit. Therefore, space base will require 24hour 365day supply of energy even if there are no transports of freight and personnel to space base, which will eventually increase the transportation cost.
    ==> Moon elevator technology: Space base is held by earth’s gravitation, and rotates due to revolution of moon so almost no additional energy is exhausted. Lowering the cable or elevator to earth only for transportation can cut down cost of operation.

    Third, it seems transmitting energy needed to operate the elevator that will move to the space base is considered to be sent through laser etc from earth base, but with current technology and near futures, it seems technically hard to possess energy transmitting technology to move the elevator to space base.
    ==> The key to moon elevator is whether able to manufacture cable that has enough tensile to be used on space elevator, than rest of technology difficulty are relatively low, such as lowering the cable using the motor or technology that moves elevator up and down through transmitted electric energy.

    Have a good time!
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  3. Kernl Sandrs Registered Senior Member

    Why is this not being funded?
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  5. kurros Registered Senior Member

    I'm not really clear on how you're proposing to overcome the basic orbital mechanics problems (leaving aside the fact that the tensile strength required for your cable is rather a lot higher than what is required for a "normal" space elevator, I believe (edit, maybe it isn't actually, it might actually be less, hmm).

    The Earth rotates a heck of lot faster than the orbital period of the moon. I think you mention this, but I don't see how you propose to connect things to this cable which is hurtling through space above the Earth (or so it would appear from our perspective on the ground). The nice thing about the normal space elevator is that if you put your anchor just a little higher than geostationary orbit then its period will be 24 hours so the cable can be attached at both ends. Is this some kind of combo system where you reach geostationary orbit with one elevator then somehow try to switch onto the moon elevator? The moon elevator would fly past the earth elevator once every 24 hours (approximately) at quite a pace, how do you get from one to the other? Or maybe this isn't what you're suggesting.
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  7. eupyongri Registered Senior Member

    If it is possible to build the elevator system, and then how fast is the elevator able to move? I'm very curious about the speed of the moon(or space) elevator because all elevators in buildings are very slow.
  8. Pandaemoni Valued Senior Member

    Back to kurros's question: A space elevator works in theory. A "Moon elevator" would (because the Earth spins on its axis faster than the Moon orbits the Earth) start wrapping elevator cable around the whole planet.

    You could hold the Moon in geostationary orbit, which would require either moving it a lot closer to the Earth, or speeding the entire Moon up tremendously...and then preventing it from shooting off into space (perhaps by means of tethering it to that elevator cable).
  9. Nasor Valued Senior Member

    Yeah, if I'm understanding this correctly then I think the Earth end of the cable would be moving through the air at something like 400 m/sec from the perspective of someone watching it from the Earth's surface. This would make it hard to hop onto Earth end of the cable to catch a ride.

    Are you still around, icarus2?
  10. Kernl Sandrs Registered Senior Member

  11. phlogistician Banned Banned

    Is it news to you that the Earth rotates?
  12. Kernl Sandrs Registered Senior Member

    No, I said 'what' because I didn't quite understand what he was trying to communicate.
  13. phlogistician Banned Banned

    That the Earth rotates. DUH!
  14. kurros Registered Senior Member

    Haha, that's kind of interesting. Although I think you would actually have to slow the moon down so that it would lose some energy and drop into a lower orbit. Hmm maybe it's a bit complicated, because sure orbital velocity increases the closer to the Earth you get, so it has to speed up in that sense, but it needs to lose energy overall because it has a lot of gravitational potential energy orbiting way out where it is. As it falls into the lower orbit due to the speed decrease some of the potential energy will speed it up again, faster than it was originally going I guess. I guess you need to be careful not to throw it into some highly eccentric orbit or something too.

    I wonder what the tides would be like with the moon so close. Presumably it would screw up the weather pretty badly too. Or maybe it would be fine... *shrugs*
  15. keith1 Guest website is a compendium of all space-elevator-related items...

    There are many design issues and directions being discussed.
    Many tether arrangements may reach fruition.

    Assuming initial segments of such an "Earth-to-Space" system were implemented, a second system could transport "Space-to-Space", and a third system segment completing the "Space-to-Moon" tether connection.

    All three "separate" systems would require space taxi/docking/rendezvous vehicles between, to coordinate a scheduled connection, to reach each system's "Station" (located at the ends of each tether), so as to continue along the route to destination points.
  16. phlogistician Banned Banned

    The Moon is currently ~250,000 miles away. Geostationary orbit less than a tenth of that, I think you can see what's going to happen. Disaster. Not that moving the Moon is in any way realistic, and if we had that capability, I think elevators would be obsolete.
  17. Blindman Valued Senior Member


    A cable suspended by the moon to the Earth above atmospheric drag is feasible. But the cable will flex and sprial. The Earth end will whip about as the moon does not have a perfect orbit.

    Eccentricity of the moon is about 40000km. So this whip would have to maintain an average in high orbit 25000km (Earth end).

    There is a good part. As the earth end whips around the energy can be used to launch from the end, both escape and re-entry velocity.

    Another positive is the cable will drag through a magnetic field and could generate the power needed to pull elevators up out of Earths gravity.

    Ahh such a great idea. But what if the whipping affect is beyond human endurance. What if every lunar month the G's at the end of the cable are above 9g for a few hours. It would take a lot of work to find out how a cable would react from the moon. Add, will us humans ever become so rich as to do such an adventure.
  18. cluelusshusbund + Public Dilemma + Valued Senior Member

    What woud cause this whip-action you'r talkin about.???
  19. Blindman Valued Senior Member

    The eccentricity of the moons orbit would cause this. The earth end would be well below orbital speed. As the moon drops from apogee (high point in orbit) the earth end of the cable will move closer and gain energy and advancing in orbit. Also the total tension on the cable will reduce. If the cable has any elasticity it will also shrink in size.

    As the moon reaches perigee (low point in orbit) the end of the cable which has been accelerating will start to move up as elasticity relaxes and it decent from the moon anchor stops. Forward (prograde) whip

    Now as the moon moves to apogee, tension on the cable increase and it begins to stretch but the earth end velocity will begin to fall to the eventual (retrograde) whip.

    The extent of this whipping effect is beyond me as it would take weeks to work on a computer model just to get an estimate.
  20. cluelusshusbund + Public Dilemma + Valued Senior Member

    Why woud the earf end of the cable advance as it gets closer to earf... woudnt earfs gravity pull the earf end of the cable toward the center of earf... which woud keep the cable perpindicular to the moon.???
  21. Blindman Valued Senior Member

    I could be wrong. But as it (falls) moves toward the earth it will accelerate in a vector not perpendicular to the earth as it is attached to the moon which is in orbit. We have two forces, gravity of the earth, and tension on the cable from the moon.

    This is a simple view of it. The resonance frequency of the cable will be low and if it matches the 28 day orbit of the moon that could have dramatic effect on the cable. But this could be and advantage.
  22. cluelusshusbund + Public Dilemma + Valued Senior Member

    Well now i visualize the cable stayin perpindicular to earf (not the moon).!!!

    It seems like earfs gravity woud keep the cable ponted toward the center of earf... but the cable woud not stay perpindicular to the moon... dew to the rotation of the moon stayin constent durin its elicptical orbit.!!!


    The only force i see is the tension on the cable caused by earfs gravity.!!!

    Of course ther woud also be force on the moon end of the cable dew to the moons gravity.!!!
    Last edited: Aug 13, 2010
  23. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

    But the cable is being pulled round in orbit by the Moon, and that pull does not act instantaneously on the entire length. The longer the cable the greater the lag between the Moon end moving and that movement taking place at the Earth end.
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