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A_M_Swallow
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« on: August 18, 2006, 04:17:42 AM » |
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Return of an old idea, using contra-rotating bands to convert electricity into motion without using propellant.
The two belts would use electromagnets to push each other in opposite directions. The electromagnets can be powered directly from solar cells. The magnets are dynamically adjusted to attract each other when approaching and repel when departing.
The belts have to go in opposite/contra directions because if they go in the same direction one will slow down eventually causing it to fall out of orbit.
Initial launch of two belts going in opposite directions will not be easy since they have to use exactly the same polar orbit. It may be easier to launch them together and reverse one. Keeping the two bands together will be difficult but may be possible using small magnets on the side of the belts.
Once above the atmosphere the two band system should work at any height from LEO to GEO.
The bands can accelerate a satellite by magnetically coupling it to one one of the bands. The satellite is released when it reaches the correct speed. A spaceship can be slowed down by coupling it to the band going in the opposite direction. Between maneuvers there is likely to be a delay whilst the bands return to their correct speed.
Andrew Swallow
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Andrew Swallow
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neil
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« Reply #1 on: August 18, 2006, 09:42:57 AM » |
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Will equitoral orbit work instead of polar orbit? Perhaps you want a solar sychromous semi polar orbit, so the Earth won't block the sun from the solar cells. I think that makes attachment of the spokes at the Earth end impractical. Perhaps you do not intend to attach the spokes at the Earth end?
Many gigawatt hours are stored in the counter rotating bands, so perhaps it is not importatant that the solar cells are in the dark 40% of the time. Neil
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« Last Edit: August 19, 2006, 07:09:29 AM by neil »
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A_M_Swallow
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« Reply #2 on: August 18, 2006, 04:34:07 PM » |
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Will equitoral orbit work instead of polar orbit?
Yes. Although an equatorial orbit of a power cable may get in other people's way. An interesting question - is there anywhere on Earth that cannot be under a made to measure set of bands?
Perhaps you want a solar sychromous polar orbit, so the Earth won't block the sun from the solar cells. I think that makes attachment of the spokes at the Earth end impractical.
Unless the spoke was a beanstalk Space Elevator. The bands could be changing the newly launched satellite's inclination.
Many gigawatt hours are stored in the counter rotating bands, so perhaps it is not importatant that the solar cells are in the dark 40% of the time. Neil
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Andrew Swallow
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Lensman
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« Reply #3 on: August 22, 2006, 11:20:48 PM » |
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As Bob Munck tried to point out in the parent thread, a ring traveling faster or slower than orbital speed isn't actually in orbit, thus its position isn't stable. Pull down on it and the position will shift by an ever-increasing amount until it starts crashing to Earth, and doesn't stop until it's all down. See Larry Niven's Ringworld Engineers for specifics.
This entire idea is fundamentally unworkable, and adding multiple rings and/or magnets doesn't change that.
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A_M_Swallow
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« Reply #4 on: August 23, 2006, 09:37:13 AM » |
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The contra-band is only stationary once, when it is reversed during initial building.
The main band supports the contra-band during the reversing; this places lower limits for the mass and velocity of the main band. These limits have not been calculated yet.
To support a slow contra-band the same techniques can be used that are used on Earth to support moving band going round the roof of rooms. So far no particularly difficult problems has been mentioned, although the quantity makes them expensive (e.g. 500 off supports).
When there is a big speed difference use magnetic coupling, when the velocity differences are small wheels underneath can support the contra-band.
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Andrew Swallow
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neil
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« Reply #5 on: August 24, 2006, 04:05:03 AM » |
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Originally posted by A_M_SHallow
To support a slow contra-band the same techniques can be used that are used on Earth to support moving band going round the roof of rooms. So far no particularly difficult problems has been mentioned, although the quantity makes them expensive (e.g. 500 off supports).
Can you give us a reference for contra=band use in rooms? Neil
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Bob Munck
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« Reply #7 on: August 24, 2006, 10:27:48 AM » |
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By its very nature a self supporting system can only exist in space Not true. The Lofstrom Loop would have been mostly in the atmosphere. There's no law of nature that says something has to be "in space" to be going faster than orbital velocity. The main band is a very large satellite. At full speed the contra-band is also a satellite, at lower speeds it hangs from the ceiling (the main band). No, satellites are in orbit, by definition. These things aren't in orbit. A self supporting satellite Satellites aren't "self-supporting;" they're falling. I don't understand why you didn't have a picture of a kitten. It would have been every bit as relevant as most of these pictures. |
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The future arrives sooner than you expect, and in a different order.
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A_M_Swallow
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« Reply #8 on: August 24, 2006, 11:41:39 AM » |
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Satellites aren't "self-supporting;" they're falling.
Satellites do not have a tower supporting them, unlike say a suspension bridge. Satellites are "falling" in such a way that they do not hit the ground. The only thing keeping them up is their velocity.
I don't understand why you didn't have a picture of a kitten. It would have been every bit as relevant as most of these pictures.
A kitten does use an electric motor to move along a track, unlike the train or the bands. |
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« Last Edit: August 24, 2006, 03:11:29 PM by A_M_SWallow »
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Andrew Swallow
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A_M_Swallow
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« Reply #9 on: August 24, 2006, 03:12:01 PM » |
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The stability problem is that the ring is a solid object that goes all the way round the Earth. As one side gets closer to the Earth the other side is pushed further away. Gravity on the close side is stronger both pulling the object in and accelerating the far side. The ring will either crash into the Earth or like Jupiter's rings be broken into small bits or both. A rotating object that is stable is a gyroscope. http://www.howstuffworks.com/gyroscope.htmTo change the bands into a gyroscope move the entire structure to the same side of the Earth, reduce the diameter and add spokes so gravity etc. cannot compress or elongate the object. Applying an out of plane force to the object will then cause it to perform a precession. Since the contra-rotating bands are now in orbit they cannot provide lift without descending but they can accelerate/decelerate a spacecraft along their tangent. The momentum given up will need replacing by solar powered magnetic repulsion between the bands. No fuel is needed because the second band acting as the propellant. When the velocity of one of the bands gets excessive the pair can slow each other down by reversing the direction of the repulsion. Repeat the slowing down and speeding up sequence until they are rotating at the same speed in different directions. A brake to convert rotation into heat will also be needed. Andrew Swallow |
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« Last Edit: August 24, 2006, 05:43:09 PM by A_M_SWallow »
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Andrew Swallow
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windemut
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« Reply #10 on: August 24, 2006, 06:03:48 PM » |
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To change the bands into a gyroscope move the entire structure to the same side of the Earth, reduce the diameter and add spokes so gravity etc. cannot compress or elongate the object. Applying an out of plane force to the object will then cause it to perform a precession.
Since the contra-rotating bands are now in orbit they cannot provide lift without descending but they can accelerate/decelerate a spacecraft along their tangent. The momentum given up will need replacing by solar powered magnetic repulsion between the bands. No fuel is needed because the second band acting as the propellant. I am not sure I understand this right, but it sounds like you are getting close to a very interesting contraption called the electrowheel, which is much simpler and more well-thought-out: http://www.islandone.org/LEOBiblio/SPBI130.HTMI find the above site to be a real treasure trove for exotic launch contraptions... Andreas |
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A_M_Swallow
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« Reply #11 on: August 24, 2006, 07:16:19 PM » |
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Not true. The Lofstrom Loop would have been mostly in the atmosphere. There's no law of nature that says something has to be "in space" to be going faster than orbital velocity.
The vacuum pumps on the Lofstrom Loop probably make a good approximation to space. |
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Andrew Swallow
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A_M_Swallow
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« Reply #12 on: August 27, 2006, 04:46:26 PM » |
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The Electrowheel is a nice train set. I like it. Since it has been designed with a vertical track and a break at the bottom the Electrowheel has been optimised for launching from rockets. A version to form Stage 2 of the Space Elevator probably needs to be horizontal and have a complete 360° track. Slowing 200 metric ton loads may need thicker cables than piano wire and the projectile to travel anti-clockwise. An alternative to moon dust as a way of slowing the Electrowheel needs inventing. Excess energy could be converted into heat. Using the delta_V data I placed on my website. http://uk.geocities.com/am.swallow@btopenworld.comA wheel in GEO orbit can be used to change the inclination of a spacecraft's orbit through d degrees using a delta-V of 6.14*sin(d/2) km/s by accelerating it South to North. Drops to LEO require between the spacecraft to slow by 1.4 to 1.5 km/s. On reaching LEO a reduction of velocity by 2.47 to 2.24 km/s is needed to circularise the orbit. For high dives to LEO a wheel at say 23,800 km could supply the delta_V of 7.6*sin(d/2) km/s needed to change the inclination. A small delta_V is needed to set the perigree. On reaching LEA a delta_V of -2.0 to -2.2 km/s is needed to circularise the orbit. A wheel in LEO can perform the slowing needed for Earth landings, GEO drops and high dives. Going the other way some of the delta_V of about 7.2 km/s needed for LEO drops could be provided. |
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« Last Edit: September 01, 2006, 01:30:29 PM by A_M_SWallow »
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Andrew Swallow
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neil
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« Reply #13 on: August 28, 2006, 12:31:52 AM » |
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Hi A_M_SWallow: I have several problems with this thread. In the original post, you seemed to infer that a 2 meter counter rotating band with a mass of two kilograms produces a partial levitation of 2 grams, so a big scale up can produce total levetation. I don't think any levitation is produced. It is an old idea that is wrong.
Now if one band has a circumfrence of about 26,000 miles and a speed of 9 miles per second, then the band is above orbital speed and does more than levitate, if it is stong enough not to break apart. This faster than orbital speed band can support a slower band in either direction, but the high speed difference makes the coupling difficult. I don't think counter rotation produces additional levitation, but it does slow the faster band more than it does rotating in the same direction. The slower band could be separate segments, but the design and reliability are better if both bands are a complete circle.
In your 0834 pm post, you mentiond a power cord which might get in the way. Is this a 300 mile long extension cord? This will wrap around Earth unless it is attached to a 3d band segment that is traveling about 1100 miles per hour and the band system precesses about 1100 miles per hour around the Earth's equator.I looked at the electrowheelweb site. I'm suspicious that this is junk science, but I admit to not understanding. Do magnets powered by dc produce eddy currents?
Multiple SEs of the Dr. Edwards type (Is that what you called a beanstock?)could support a single ring, or a ring system, but, my guess is totally impractical, unless the CNT is much stronger than GPa = 130 More in next post. Neil
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« Last Edit: August 28, 2006, 12:59:50 AM by neil »
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A_M_Swallow
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« Reply #14 on: August 28, 2006, 09:25:05 AM » |
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Yes a Beanstalk Space Elevator is a long tether that goes a long way past GEO with optional counter weight. Beanstalk comes from this page http://en.wikipedia.org/wiki/Space_elevatorI had trouble finding post 0834, post #3 displays as 01:34 on my computer. I meant mechanical power - the contra-rotating bands. The advantage of magnetic coupling is that the two bands do not touch when moving at high speeds, reducing wear. The rotating bearings cover the case when the bands are moving at nearly the same speed and direction. Combining the bearings and the supporting magnets reduces the weight and complexity. Lets separate construction from normal operation. Once started the bands would probably never be allowed to stop. If the bands do not circumnavigate the planet they cannot be used to lift things and I have been convinced that keeping the bands in a Ringworld style orbit would be too difficult. Smaller bands that are actually satellites could be used to accelerate spacecraft. One of the bands transfers momentum from itself to the spacecraft. This slows the band down. Solar powered electromagnets are then used to speed up both bands in opposite directions. Conservation of momentum is the reason for two bands or a band and a locomotive/projectile. A full Beanstalk and smaller rotating bands would be independent objects that just happen to meet every 100 minutes or so. |
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Andrew Swallow
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