Mining the Moon

[nexium]

The low gravity does reduce the strength required by the tether, but 80,000 miles of tether would be a massive project even with the most optimistic projections for CNT = carbon nano tubes. The elevator proposed by Dr Hugh Edwards is about 91,000 kilometers long.<br />Besides a practical sling shot manuver, starting from a launch from the moon elevator; how much more delta v is needed to reach Mars in less than two years, or so? Neil

 

[dan_casale]

From Space.com<br />http://www.space.com/news/beyond_iss_020926-1.html<br />The Earth-Moon L1 Lagrange point is at a distance of some 200,000 miles (323,110 kilometers) from the Earth, or 84 percent of the way to the Moon.<br /><br /><br />Thus the elevator only needs to be twice the distance as the L1 point. or 76,190 miles long. Almost 20,000 miles shorter than the Earth elevator proposed by Dr. Edwards. Because it only has 1/6 the stress for the same payload, I believe that current materials will work. I don't remeber how we ended up with a figure of 240,000 miles but I believe that would almost touch Earth's atmosphere.<br /><br />But if the real goal is to supply Mars with Lunar materials, then you want a rotating tether (not an elevator). Information about these can be found at www.tethers.com. Rotating tethers are practical with current materials. There three problems with the rotating tether idea, it would have to be constructed in space because nothing available is large enough to launch one. A mach 10 - 12 vehicle is needed to deliver payloads to the tether at an altitude above 100,000 feet (the shuttle could be adapted). Currently there is nothing to do with that large of a payload.<br /><br />

 

[nexium]

Would you believe 221,000 miles? That way it would clear Earth's geo stationary belt most of the time, but that would leave 600 miles plus to Earth or from Earth to the tether.<br />The length of the of the Dr Hugh Edwards' tether is almost 3 times the distance to geo stationary altitude with considerable ballast, but I suspect you are correct double is enough 76,190 miles long = about 1/3 of the Moon's closest approach to Earth. Will the 5 degrees the moon orbit is tilted with respect to the plain of the Earth's orbit complicate the design?<br />The radius to the center of the moon is about 78,000 miles times 6.28 = the distance the end travels in 27 days = 18,142 miles per day = 756 miles per hour with respect to the moon's surface, at the Moon's poles. Speed with respect to Earth's poles will vary, maxing at a small percent of orbital speed. Payloads dropped off the end of the tether will drop like a rock toward Earth and burn up in the atmosphere without considerable delta v being added.<br />From Earth to tether end (at average Moon distance) will take about as much energy as going to LEO = low Earth Orbit.<br />I think payloads not going to Earth need to be released close to L1 where the tether is only moving about 380 miles per hour with respect to the moon's axis of rotation but the craft is near the outer edge of the Earth-moon gravity well as it starts for Mars or elsewhere. Please check my arithmetic as one test of accuracy failed. Neil

 

[nexium]

A moon elevator reaching 1/3 of the way to Earth or 99% of the way to Earth will swing like a very slow pedulum, and have several modes of transients. It may be practical to flip a space craft off the end, like the crack of a whip with the help of carefully timed transients. I think this is also true of the Dr Hugh Edwards' elevator. Dodging the tether around space junk and micro meteors can be done with transients. The (much farther from Earth) Moon elevator likely needs collision avoidance humans at stations along the tether, while Dr Edwards hope this task can be done from Earth's surface. Neil

 

[nexium]

2 Another problem with rotating tethers, is extremely critical timing of both climb aboard and flip off.<br />3 A rotating tether is the second of three stages and perhaps the least powerful of the three stages, while a Dr Hugh Edwards tether is all the stages needed except mid course corection and manuvering at the destination.<br />4 The rotating tether needs considerable fuel for station keeping and speeding up the tether repeatedly unless incoming traffic matches out going. Neil

 

[dan_casale]

Good points...Lets discuss.<br /><br /> />>The length of the of the Dr Hugh Edwards' tether is almost 3 times the distance to geo stationary altitude with considerable ballast,....<br />With that much length, both the inner and outer planets are reachable without additional propultion, only course adjustment thrusters. The lunar elevator only allows access to solar orbit at L1 or Earth orbit. Both require additional propultion, which in the case of a STS sized launch system means about 3 million LBS of propellents to get to and land on Mars.<br /><br /><br /> />>Will the 5 degrees the moon orbit is tilted with respect to the plain of the Earth's orbit complicate the design? <<<br />I don't think so, the elevator will always point directly at Earth. As you point out later, the moon does have a rocking motion, that and the Earth gravity well can be used to add several Km/s to any payload. That is what I ment about using the Earth's gravity well to slingshot payloads.<br /><br /> />>The radius to the center of the moon is about 78,000 miles times 6.28 = the distance the end travels in 27 days = 18,142 miles per day = 756 miles per hour with respect to the moon's surface, at the Moon's poles.<<<br />No energy can be gained from the Moon's rotation because the same side always faces the Earth, so there isn't any rotational energy available for an elevator on the Earth's side of the Moon. An elevator on the far side would be able to sling payload very fast, but it would have to be very long to overcome the Moon's gravity.<br /><br /><br /> />>It may be practical to flip a space craft off the end, like the crack of a whip with the help of carefully timed transients. I think this is also true of the Dr Hugh Edwards' elevator. <<<br />While the Moon's elevator might be able to use the "crack of a whip" method, the Earth elevator uses centriapedal forces.<br /><br /><br /> />>2 Another problem with rotating tethers, is extremely critical timing of bo

 

[nexium]

Hi eburacum: Most of that seems correct. L1 ranges from 37,000 to 41,000 (about) from the Moon, so 50,000 miles of tether with little or no counterweight may be enough to prevent the moon elevator from falling back to the moon. Payloads and/or tether repair climbers may have to assist when the moon is farthest from Earth. Any large fixed mass near the average L1 point will stress the tether, perhaps dangerously. I believe the sun also shifts the zero g point of L1 by perhaps one thousand miles, some times horizontally. so this will upset the rythem of the pedulum effect, but I believe we can live with this effect also and a Moon elevator and Earth elevator will both be practical, when and if, we have cheap, but very strong material. Neil

 

[nexium]

Lets try some numbers with a rotating tether 1200 miles long as streched under typical launch to Pluto conditions. 1000 miles may be the relaxed length (lazy S shaped~) with the center at an altitude of 600 miles in a semi polar orbit which will allow it to be over (all but the highest latitude) nations occasionally. If it makes one rotation per half hour, the circular path of the tips has a circumfrence of 3142 miles and the average speed is 6283 miles per hour. Since the center of the tether is orbiting about 17,000 miles per hour, a hypersonic craft at about 10,000 miles per hour is needed to attach the pay load when a tip dips into Earth's upper atmosphere. Trancients produced by the previous pay load and the motor effect of an electrically conducting tether may slow the tip to 9000 miles per hour and air friction to 8000 miles per hour reducing the fuel consumption of the hypersonic aircraft considerably. I suspect a rocket motor is needed at each tip to flatten the lazy S enough to get the tip deep into Earth's atmosphere. We do not want the tips dragging though the atmosphere, except when a pay load attachment is schedualed. There are 96 oportunities per day, but we will pass up many of them until the transients are favorable. We really need an other transient shortly after attachment of a pay load to assist the tether momentum and the tip motor in pulling the tip out of Earth's atmosphere, before that end of the tether is stretched to the point of failure in the rapidly rising heat due to air friction. A short burn of the pay load motor would be helpful. A somewhat longer and faster tether may be a bit more favorable, except g loading of the pay load may reach ten g briefly. A rotating tether near the moon is much better, I think. Neil

 

[w_ashley]

Here are some things to research:<br />0 emissions <br />solar furnace <br />superconductor testing for low space temperatures<br /><br />-there is no reason to send humans to the moon, it should all be robots, only a 'test and main command points will be viable like antartica stations. ' It is a resource drain, having repair robots ects can take away the need for humans on the moon<br /><br />-It makes no sense to land things on the moon only to take off when you can just launch them right out into outer space<br /><br />-There is a need for a united front for any real future space mission one that is held by a united earth organization. Privateering and claiming of land and all the other hypocracies of militancy need end in space as here on earth. With taxing jurisdictional governments we cannot in good spirit go to space. We have many potential issues on earth that need be solved. <br /><br />Our major issue is that we are killing time and surviving because it is humans pastime, death is just a meaningless or meaningful as life, we should remember we are enhacing each others life. Money really has no value except for wage livers, it is a means of exchange but it does not fully translate to what is valued in the long run mearly what is currently available, and what individuals are willing to do for it.<br /><br />We have an abundance of resources on earth but we have a lack of intelligence, humans have been gaining material wealth from the planet but have raped it in the process. Essentially we need to see mater as matter, we don't need fecalfobes and we don't need agressors, what we need is facilitators and individuals who are willing to put into practice efficient non damaging systems. We simply have no need to be on the moon right now except for the excuse of research, it simply isn't viable without creating support systems. We have large landmasses here that are not 'fully faciitiated' such as antartical Northern Wildernesses. We have terrible efficiency on earth, we hav

 

[rocketman5000]

how bright if your sun in your imaginary land. If the course of history has told us anything it is this. humans will always agree, it is only human. if we disagree we bind together collectively. If everyone flet the same we would either all be communist already or we would have been invaded by the borg collective. Nationalism has achieved great things and it has caused grave calamities. <br /><br />If it wasn't for war we would not have some of the greatest inventions ever made. Rockets for an example. You seem very antispace so I question your reason for posting here. <br /><br />Without competition you cease to have innovation. Windows is an example. If everyone thought together you would cease to have great innovations.