Martin Odber

This conversation is closed.

Can a satellite have any sort of dangling earth elevator?

In the same fashion that a bobber floats on the surface of rushing stream of water while a hook and sinker ride a line deeper into the stream, could a space station take advantage of this for an easy access supply elevator?

Planes could supply the dangling supply line the same way they do in air refueling.

Why or why not?

Closing Statement from Martin Odber

Having a plane meet a grappling hook from a satellite is no more feasible at this time than having a cable strung from the earth to a geostationary object due to technological limitations it seems.

This means the answer may lie in other directions, such as a line between two balloons at 50,000 ft which the satellites grappling hook would claim and detach claiming the package, if that is, the grappling hooks speed accelerating the stationary package did not cause a significant issue.

Admittedly it has been a thought provoking conversation. I'd like to thank everyone for participating and hope we all had fun.

Thank you again! The future is out there.


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      May 20 2014: I really like that picture, thank you Jacob.

      Another commenter pointed to this sort of thing along with the difficulty of finding a cable strong enough to be reliable.
      • May 20 2014: From the wiki link-

        "On Earth, with its relatively strong gravity, current technology is not capable of manufacturing tether materials that are sufficiently strong and light to build a space elevator. However, recent concepts for a space elevator are notable for their plans to use carbon nanotube or boron nitride nanotube based materials as the tensile element in the tether design. The measured strength of these molecules is high compared to their densities and they hold promise as materials to make an Earth-based space elevator possible.[2]"
  • May 20 2014: When you look up space elevator you will find many results.
    There are competitions to make both the tether and the climber, for example:
    There is lots of information out there and research being done.
    Transferring payloads in mid air seems more complicated to me. You suddenly add (a lot of) weight to something hanging in the air, where will it get a sudden increase in lift from? Drop ballast? Then you have the problem of getting ballast up there. Tethering a satellite to earth makes sure the line is always taut and as long as the satellite is flung outwards far enough, it can have an overcapacity of "lift" which can be used to hoist things up (in most concepts the lift is self propelled and not hoisted by cable).
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      May 20 2014: " it began to fail at 1,600 pounds-force (7,100 N), forcing the test to be called off" An interesting article to say the least.

      The idea you spoke of, that of tethering a satellite to the earth and using centrifugal force to create tension, may offer a few hazards; both line and satellite (rather than the easily calculable fixed satellite a moving satellite would require its entire orbit protected) always in place providing an on going target for space debris, could offer a hazard for flight paths, would require a clear flightpath not only through earth atmosphere, but also through existing satellites, might be subject to additional degradation from heat/strain, once goods arrived at the top something would have to travel roughly 1000mph and dock to retrieve the goods from the satellite.

      If those and other concerns could be overcame, the satellite end were a large high density anvil like device and we had numerous of them in place, they could also serve to deflect space debris and might offer a double function. As the article mentioned however, finding a tether that strong and resistant, may pose a significant challenge.
  • May 20 2014: Martin,

    It was mentioned in the 50's in science fiction and was proposed a lot earlier. There has been many papers on it.
  • May 19 2014: In theory at least, this is a possible concept. Google X-Labs have been rumored for quite some time now to be researching the viability of such an endeavor. There are however many challenges associated with this. Firstly it couldn't be any kind of solid structure as the weight would be far too large and any movement would be amplified by the distance. Secondly is the problem of space junk, with over 500,000 pieces being tracked by NASA, the likelihood of a solid immovable and relatively stationary object being hit over any length of time is far too large. The next problem is preventing the weight of the cable its self from either pulling the satellite out of orbit or snapping the cable. This is currently beyond are technology however new advancements in Carbon nano-tubes and Graphine offer some hope. The problem of a break is amplified by this as the satellite would have to have enough velocity to apply tension to the cable meaning that if the cable was hit by space jink the satellite would go flying off uncontrollably into space. Finally and most crucially is the question of cost. The cost involved in the construction of the base as well as a geostationary satellite of any size would be huge, far too much for any one country to afford. It would take a huge international effort to make this a reality, something people will be unwilling to do for a very long time as money can be better spent else where.
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    May 27 2014: For the ground end of the cable to be stationary on the ground, the object to which it is tethered must be in a geo-stationary orbit. (circa 36000km) Any lower than that and the sattelite will fall to Earth as its orbital velocity would be insufficient to overcame gravity. If it was slighly higher than necessary it would generate slight tension in the cable which would work. However even carbon nano-tubes will struggle to produce a tether that is 40,000km long.
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      May 27 2014: So why go from the ground to the satellite? Why not drop a line from the satellite into the atmosphere, attach goods to it with a high flying plane, and haul the goods back up?
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        May 28 2014: Because for a sattelite in relatively low orbit (200-500km) the delivery plane would have to be flying at 20,000kmph, which is impossible. To get the required ground speed down to a sensible limit you would still need the sattelite to be tens of thousands of kilometres away. The international space station for example completes an orbit in about 90mins. That's a ground distance of about 40,000km in 90mins. The plane grabbing the end of the cable would have to keep up with that.
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          May 29 2014: Thank you Peter for explaining that. I'd always thought of satellites as stationary while the earth turned beneath them. You certainly explained a great deal.

          Peter, hypothetically speaking of course, if a satellite DID drop a line down through the atmosphere to the earth, would the hooks speed be constant at all altitudes at the 20,000
          kph, or would the hooks speed be relative to its distance from the earths surface?
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        May 29 2014: Basically the closer to the Earth the staellite is the faster it has to orbit to fight the pull of gravity. Most satellites are either in a low orbit which means they are less than 1000km up or in geostationary orbit which means they orbit once a day but are 35,786km above the surface. Each has it's pros and cons. Low Earth orbit means you can use small transmitters as the distance in small but the receivers on Earth need to track the satellite as it moves across the sky. Geostationary satellites are stationary in the sky as they orbit in time with the Earth's rotation, but as they are sooo far away they need much more powerful transmitters and the distance produces a delay in transmissions.
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          Jun 10 2014: Peter, this has been very educational for me. I now understand that if a satellite travels 8,000 meters per second, it is constantly falling, but AROUND the curve of the earth which is what keeps it in place as the earth horizon drops about 5ft per 8,000 meters.

          Our fastest plan at mach 3 about 2.5 thousand mph .. even with the earth turn 1000mph does not equal the 20,000 mph the falling satellite has.

          I'll have to think on this more.

          Thank you Peter.
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    May 21 2014: a dangling supply line between airplanes is one thing, but miles of vertically tethered 'cable' is another. Even if we overcome the technical construction, what would be the costs of the research and the construction and maintenance of such a feat vs fuel and craft deployment? How much travel time would we save by this implementation over current transportation methods? What is the realistic payload? How many 'cables' would be allowed to extend from the ground to space - and who would be 'permitted' to have one? When one falls, who gets killed and who's responsible? Yes, I believe we could have them, but do we want them?
  • May 20 2014: It would be cool to try, but I don't want to live in the debris path.
  • May 20 2014: No problem, we can just attach a ladder so the astronauts can climb up and down, we could do one for each of the thousands of satellites also, think of all the money we could save. What could possibly go wrong with that idea? That is right up there with setting off nuclear bombs in space, probably another Stanford idea right? Let's see we got sub-zero temperature swings and what happens to the line when a 200 mph tornado wraps a tree or two around the line? Do we get to vote on this one?
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      May 20 2014: First, it is reasonable to presume that the persons in charge would not book a SATLIFT event during a tornado or hurricane. Second, if one sprang up spontaneously the SATLIFT event could be occurring 5,000 to roughly 40,000 feet above its position making it a non threat so there goes that issue.

      Third, sub zero temperature swings .. could be a hazard all right. How do our space stations deal with that issue currently might be a great starting point. Wish we could ask someone like Commander (retired) Chris Hadfield that one, he'd probably have a great answer.

      How do you feel we could overcome the subzero issue?

      A tornado can go to as much as 60,000ft.
      Hurricane 50,000

      Specially modified military jets have gone up to 100,000 feet plus for short amounts of time. (20 minutes max)
      • May 20 2014: Maybe I didn't understand your intention, I thought you were going to extend this connection to earth somewhere like a kite string and flying a kite in a hurricane is a pretty ridiculous idea, I've been in a hurricane. Did I mention the earth is spinning at 1,700 km/h at the equator? Once attached that would make a huge ball of thread. Back to the refuel in air idea, the reason that works is both planes are traveling at the same speed. In this instance you have a plan traveling rather fast and a string stationary, not conducive to making a connection. However you may want to consult with Elon Musk as his new rocket design will hover in the air. Then all you have to do is keep the interplanetary traffic and satellite positioning rockets from crossing your line. Oh, did I mention our friends with big eyes and funny looking heads from other planets, you may want to inform them also, there is nothing that ticks off our Unidentified Flying Friends more than getting string wrapped around their tail.
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    May 19 2014: Fascinatiing..

    Oliver, given the situation you have outlined so very well, what if a heat resistant cable were temporarily lowered from the International Space Station into earth atmosphere to be reeled back in like a fish on a hook?

    The cable itself could be comprised of multiple sections that would detach prior to enough force accumulating to destabilize the orbit of the satellite.

    Also each of those cable sections could have mini parachutes built in that would deploy if the line were broken thus offsetting any damage a falling "package" might create.

    The cable would be reeled out into the atmosphere, a plane or helicopter would meet the end of it, attach the goods, and the line be reeled back in.

    Packages could include goods, and or passengers in small capsules.

    As the cable itself would be relatively thin, and only present during transfer phases, it would vastly reduce the chances of being hit by space junk.

    It would also be alot more affordable than say sending up an actual spaceflight?