I posted something similar on another thread. You could build cloud nine structures on venus (http://stevendejonckheere.blogspot.com/2006/08/cloud-nine.html). These could be made into 2-part domes with one section providing lift and one made for habitation. The main section could be lower pressure and heated by solar panels. The atmosphere might be a combination of oxygen, nitrogen and helium. CNT materials would enable you to get more bouyancy. We may eventually have a large number of these structures and use ceramic balloons to ferry robotic miners and ores up and down from the surface. We could also harvest the sulfuric acid and the CO2.

The economics of a lunar space elevator are rather interesting. The longer it is, the more you reduce the rocket equation on the Earth side. However, you also increase the required ribbon material logarithmically. You'd probably look at the price of rocket fuel by total launches during the life of the ribbon to specific altitudes versus the cost of ribbon material at specific lengths. (total fuel cost vs. ribbon cost) I think the optimum length is around 300,000 km (provided it doesn't interact too strongly with Earth's magnetic field).

An LSE reaching to within 100km of earth at perihelion would not be quite as strong as an earth SE (there's a slight advantage because the LSE is always at high tide). However a material requiring a specific taper ratio would require MUCH more ribbon for an LSE than the same material ESE.

Research into robotic mining should be better funded if a permanent moon base is to become feasible. Hell, we could use robotic mining here on Earth.

This is actually too long. The distance at perigee is 363,104 km.

This is also incorrect. If a taper were utilized, the thickest point would be at L1.


The project could begin as an unmanned space station at L1. The longevity of such a station would be greater than the ISS, as there could be no atmosphere degrading it's orbit. Minor station keeping would be required until an elevator is deployed. Afterwards the station would be anchored by opposing gravities. Eventually it could be made into a manned station, with artificial gravity so that lunar dwellers could spend part of the year under full gravity.

The station would outlive the longevity of the ribbon and could continue to faciliate moon operations. New ribbons could be launched from Earth until recycled loop elevators became possible.

One difficulty for solar energy is that the moon side of the elevator would be in shadow twice a month.

The important point, I believe, isn't that it gives you access to the moon's resources (although that's a nice bonus). The important point is that it provides a single-stage-to-tether, but doesn't require the supersonic speeds of a skyhook. Also, the fact that it could be built and repaired with conventional materials, I think, would make it cheaper than an Earth SE. Additionaly, if it could achieve a <1 taper ratio, you could vastly increase it's longevity and have an easy way of scaling it up. I don't know if it could be 380,000km long, however. The wikipedia article suggests 230,000km is possible (I think based on Jerome Pearson's work). http://en.wikipedia.org/wiki/Lunar_space_elevator

The catch 22 is that you'd need a moon base and a carbon supply on the moon to do repairs. A loop elevator might work if you could recycle the carbon. There are very trace amounts of carbon on the moon http://www.asi.org/adb/m/08/08/lunar-carbon.html

I thought it would be moving a bit faster. Did I miss something?

Rotation velocity of Earth at equator: 465.11 m/s
Mean Circumference of Earth: 40,041.47 km
Orbital period of Moon: 655.717968 hours

1,674.396 km/hr - (40,041.47 km/655.717968 hours) = 1613.3 km/hr

You could probably reach it with something similar to SpaceShipOne. I don't think you would need CNT for a lunar elevator, but it would help. Not only is the moon's gravity well 1/20th of Earth's, but every point along the elevator would have tension alleviated by opposing gravities, and you wouldn't have the centrifugal force. I think a taper ratio of <1 is possible, which would allow you to fold it over and reel up new material as well as increase the size. Does anyone know the target GPA for the lunar elevator?

Mean radius of Venus' orbit: 108,209,184 km
Mass of Venus: 4.8685×10^24 kg
Mass of Sun: 1.9891 ×10^30 kg

http://www.google.com/search?hl=en&q=108%2C209%2C184km*cube+root%284.8685%C3%9710%5E24kg%2F%283*1.9891+%C3%9710%5E30kg%29%29&btnG=Search

Distance to Venus' L1: 1,011,121.22 km

Axial Tilt: 2.64°
Sidereal rotation period: −243.0185 day
Venus' mean radius: 6051.8 ± 1.0 km

13.4 km/h would be required at the equator to keep up with the planet's rotation. You could anchor it at 50km altitude to a buoyant platform. You could use breathable air as the buoyant gas. You eventually might even try something like a cloud nine structure (http://stevendejonckheere.blogspot.com/2006/08/cloud-nine.html).

At the counterweight, you wouldn't be orbiting the planet. You'd be orbiting the sun with Venus rotating nearby, so the taper ratio would be 1. You could use conventional materials for the cable. With plant life on the platform, you could harvest oxygen from the atmosphere and use Venus as a fueling station.

Your cable car would probably drop off near L1 and burn fuel to attain an elliptical orbit, then slingshot back to Earth or elsewhere. Anyone care to run figures on fuel requirements?

Perhaps space junk could fuel a bolo? Decelerate it into earth's atomosphere.

There's no way I could ride a bike, and I'm really fit. I drive about 300 miles a week between my job and school, so it's just not happening. A friend of mine used to bike. He got clipped by a car one time and couldn't walk for a week. I don't see how you could ban cars. There aren't enough horses to ban cars. Any government solution is going to mean more taxes regardless. So, yea, if we can't find any better solution I'd rather pay for some balloon shields in my taxes than give up driving. I don't see balloons costing more than a few hundred million. Hell, we could have just the auto industries pay for it and they'd still make money and we'd still be wealthier than we would be on bikes. In an ideal world, we would drive electric cars and use solar energy, but that's a long term solution. A long term solution won't help us if we fry in the near term.

Well, we already are blocking sunlight to some extent due to global dimming. This happens when particle emmisions from non-clean burning change the composition of our clouds. The clouds form more droplets than otherwise and reflect more sunlight. This actually helps reduce global warming, but the particles emmisions are bad for our health. We have had some success reducing global dimming with carbourators and clean burning in factories, but the turn-around may make global warming more pronounced. A solar shade might be a way to make global warming less pronounced without having dirty air.

The SE, as a whole, is not in GSO: the anchor not only has to prevent the SE from being pulled upwards, it has to prevent the SE from moving westwards. If the anchor is on water, this means running the engines or having fins to create drag.

Below GEO, the laser's energy lifts the climber. Above GEO, the climber can continue upwards powered by earth's angular momentum. But if the boat is pulling the ribbon eastward, then the boat's engines impart momentum to the climber, just as you are thrown backwards in your seat when you accelerate your car. The kinetic energy of the climber is relative.

One climber a day? Is that possible? Dr. Edwards says 97hrs is the minimum launch interval as it is the time necessary for a climber to reach the 0.1g point, but I'm not sure that his math checks out. Earth's gravity becomes 0.1g at about 13800km which is 69hrs travel time at 200kmph. The EFFECTIVE gravity (adjusted for centripital acceleration) becomes 0.1g at 12800km which is 64hrs travel time at 200kmph. I get the feeling that the math is really fuzzy on some points:

• Is the 2x safety factor for the final ribbon or during buildup as well?
• Does the 2x safety factor apply only to the ribbon capacity to climber mass ratio or to the launch interval as well?
  
• Dr. Edwards uses 1.5% as the strength increase per strand (hopefully we can achieve that). This is a complicated number based on the ribbon material properties, the ratio of ribbon strength to climber mass, and the ratio of climer mass to climber payload mass.
• Dr. Edwards uses 207 as the total number of strands added to achieve a final tension of 20tons and a final maximum payload of 13tons. I have no idea how he arrives at that number.
  
• Supposedly, the most important number is 0.87 which is both the cable mass to counterweight mass ratio and the climber mass to climber payload mass ratio. That doesn't make sense to me either.

Any illumination on these points would be appreciated.

What do you mean by "energy dissipating cables" and "shotput style tether?" How would they differ? You might want to check out hoytethers. http://www.tethers.com/Hoytether.html

I wouldn't say "not seen." Here's some CNT that's nearly 2cm in length:

It occurs to me that the laser requirements used by Dr. Edwards represent what would be necessary to power 1 climber. However, during the ribbon build-up phase, it would be ideal to support as many as 7 climbers assuming a 144000km ribbon, 200km/hr speeds, and a 97hr minimum launch interval. (I don't know how many climbers Dr. Edwards assumed when calculating his laser cost estimates).

Maximum ribbon capacity would be ideal during the ribbon build-up phase, when the climbers would necessarily traverse the entire ribbon length. However, during normal use, the majority of payloads would be destined for LEO. This means a minimum drop point at 24000km. Climbers for LEO drops would likely descend the ribbon as well, which means only 1 LEO climber on the ribbon at a time. You would still want to support traffic to GEO and beyond, so it is likely that the total number of laser systems for the SE would be 3. This would allow the SE to have an entire backup laser system during most operation. It would also allow the other 4 laser systems to be retooled for SE2. These other laser systems might be specialized for higher altitudes (ie. more power).