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Thread: Moon elevator vs Space elevator!

  1. #1

    Moon elevator vs Space elevator!

    Hello!
    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


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


    Figure 3 is structure diagram of multiple moon elevators


    【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. 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.

    ---------

    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.

    (http://www.thescienceforum.com/Space...tor-24848t.php)
    ---------

    【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!

  2. #2
    Quote Originally Posted by icarus2
    Challenger explosion accident or Columbia explosion accident etc.
    Pet peeve of mine. Neither shuttle exploded. Structural failure of the tank, followed by aerodynamic loads on the orbiter explain the Challenger disaster, and aerodynamic loads from wing failure explain Columbia.

    Quote Originally Posted by icarus2
    air friction and collision with outside material damages body of the rocket frequently
    This is really only a problem for the Shuttle. It's not that big a deal for any other vehicle.



    As for your 'invention', I am not sure how you manage to get around the Earth's rotation in this. Let the cable lie on Earth's surface such that it is dragged once around the Earth each day, and slap some cargo on it such that it catches the cable?

    You set up arguments against rocketry,
    1) It's expensive
    2) It has inherent risk

    And then propose a system that, to me, has these issues in abundance.


    I recall a shuttle mission working with tethers. Something went quite wrong where the tether accumulated charge from particles in the LEO environment(?) and snapped.

    I would imagine your system would have similar issues, especially since it seems to traverse the Van Allen belts.

  3. #3
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    My main question is what advantages you think an Earth-Moon space elevator would have over the more standard Earth-Geostationary orbit space elevator? Particularly as it will require a much longer (and therefore heavier and stronger) cable, does not allow easy access to GSO, cannot be used for launching stuff to the rest of the solar system, and does not connect to a fixed location on Earth's surface (and in fact will be moving at super sonic speeds relative to the surface).

  4. #4
    Quote Originally Posted by Hungry4info View Post
    Pet peeve of mine. Neither shuttle exploded. Structural failure of the tank, followed by aerodynamic loads on the orbiter explain the Challenger disaster, and aerodynamic loads from wing failure explain Columbia.
    I completely agree about Columbia, but in the case of Challenger, the external tank did explode, right? I suppose that technically that wouldn't be the "shuttle" itself, but when I speak of space shuttles in general I tend to use the term to refer to the whole "stack."
    As above, so below

  5. #5
    Quote Originally Posted by Jens View Post
    I completely agree about Columbia, but in the case of Challenger, the external tank did explode, right? I suppose that technically that wouldn't be the "shuttle" itself, but when I speak of space shuttles in general I tend to use the term to refer to the whole "stack."
    The SRB plume weakened the structure of the tank. After burning through, the hydrogen part of the tank began to burn from the hole, producing a thrust. The hydrogen tank was shoved into the oxygen tank. As the tank was losing structural integrety, the SRB came lose and impacted it.
    Quote Originally Posted by Wikipedia
    At T+73.124, the aft dome of the liquid hydrogen tank failed, producing a propulsive force that pushed the hydrogen tank into the liquid oxygen tank in the forward part of the ET. At the same time, the right SRB rotated about the forward attach strut, and struck the intertank structure.
    Also, see http://www.msnbc.msn.com/id/11031097/ (dispells myths about the Challenger accident)

    This is also a fun read, gives the timeline of the accident at millisecond resolution.
    http://en.wikipedia.org/wiki/STS-51-L_Mission_timeline
    Last edited by Hungry4info; 2010-Sep-06 at 10:34 AM. Reason: Spelling.

  6. #6
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    Let's compare the two space elevator models, assuming we have material with sufficient tensile strength and the engineering means to deploy it.

    A. Elevator tethered to Earth, with counterweight beyond the geosynchronous orbit (GSO) radius to keep it taut. Payloads can be hoisted from the ground to GSO radius and released, and presto, we have a satellite in GSO. With relatively moderate delta v by whatever means we can achieve other orbits. If we extend the system out a few thousand more miles we have escape velocity, provided the cable is strong enough that the counterweight does not break it out there.

    B. Elevator tethered to the Moon and dangling near Earth. Even in a simplified thought experiment with the Moon in a circular orbit, getting the end of the elevator near the ground means a steady airspeed and groundspeed of some 1,000 mph. To transfer a payload to it, we would need to dock with it with an aircraft or some sort of vehicle on a track at that speed, and we would be at the mercy of atmospheric turbulence. If everything is not perfect we can have a major crash.

    If we hoist the payload up to GSO radius, we will need a few thousand mph of delta v to get it into orbit, as compared with none in plan A.

    With the Moon's actual orbit, the Earth end of the elevator will be bobbing around monthly over a range of some 30,000 miles, and the perigee distance varies some 7,000 miles because of perturbations from the Sun's gravity. Only once in a great while does the Moon come anywhere near its absolute minimum distance from the Earth.

    An elevator tethered to the Moon and pointing away from the Earth might be useful for launching deep space missions for which the spacecraft are built on the Moon.

  7. #7
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    A moon elevator about 120,000 kilometers long has limited utility, other than transportation from Earth-moon L1 to and from the moon. Making it longer rapidly increases the strength required, beyond what we can expect from CNT = carbon nano tubes. Cargo for Earth travels less than 1/3 of the way on the ribbon, so travel time in space is somewhat longer than lifting off from the moon and almost as much total delta v, unless it is practical to use Earth's gravity to accelerate while still attached to the tether = severe abrasion of the tether. Earth to moon cargo needs to catch the the tether which is somewhat more difficult than catching the ISS = international space station or the Hubble space telescope. Fail to catch, means marooned in space for weeks, before another attempt is possibly practical. Other destination are even less practical. Neil

  8. #8
    Quote Originally Posted by Hungry4info View Post
    I recall a shuttle mission working with tethers. Something went quite wrong where the tether accumulated charge from particles in the LEO environment(?) and snapped.

    I would imagine your system would have similar issues, especially since it seems to traverse the Van Allen belts.
    That was an electrodynamic tether, designed to couple to Earth's magnetic field and ionosphere, likely with damaged insulation following incorrect assembly/modification on a previous flight...not some unknown or insurmountable obstacle. The experiment was extremely successful in spite of the break.

    Tethers of the sort described here don't have any reason to be conductive, and would not experience any effects due to Earth's magnetic field. The belts are irrelevant except for radiation exposure considerations.

    This isn't to say the OP's suggestions are workable (I haven't read through it all yet), just that the objections you raised to tethers in general are incorrect...comparing to a tether of an entirely different sort, and exaggerating the importance of the failure. Several successful tests of orbital tethers have been made, electrodynamic and otherwise.

    http://en.wikipedia.org/wiki/Tether_satellite

  9. #9
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    Quote Originally Posted by cjameshuff View Post
    Several successful tests of orbital tethers have been made, electrodynamic and otherwise.

    http://en.wikipedia.org/wiki/Tether_satellite
    I hadn't seen that Wikipedia article before. Thanks for posting that.

    Kirk Sorensen has talked about tethers a lot on his Selenian Boondocks blog.

    Most of his tether articles have the word "tether" in the title. One exception is "Recursive Algorithm for Moravec's Mass Ratio".

  10. #10
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    Quote Originally Posted by cjameshuff View Post
    Tethers of the sort described here don't have any reason to be conductive.....
    Carbon tubes/cables don't have any reason to be conductive??? Ummmm....

  11. #11
    Quote Originally Posted by JustAFriend View Post
    Carbon tubes/cables don't have any reason to be conductive??? Ummmm....
    No, they don't. Individual nanotubes can be conductive or semiconductive, and the bulk cable could very easily be high resistance or non-conductive.

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