I agree, a rest stop at 20 or 30 kilometers could be multifuntional. The winch could not reel in more than 30 kilometers of cable and the ballons would make whipping the cable around a satellite or piece of space junk more difficult. Perhaps rockets at the way station could whip the ribbon. At any altitude trancients would rock each way station, perhaps violently and frequently.
I presume a lifter or elevator car can bravely pinch 45% of the ribbon's width while passing a way station or vehicle traveling the opposite direction.   Neil

Assuming your 02:57 post numbers are correct, we can do the same thing at the South pole of Earth. The hang down will be 1/3 instead of 1/18 of the length = 63 kilometers which is about 60 times the fall away of Earth's horizon. I think. With present technology there is no way to mount the hub high enough and faster rotation rates mean the tip and pay load would get very hot in Earth's upper atmosphere. At best, the sling shot tether at the South pole would be a first stage with a second stage required to get the pay load out of Earth's atmosphere and up to escape velosity?    Neil

Hi  Bob: I had not heard of this sling shot, but I think it is workable, except it will have to dodge over nearby mountains. It will wobble due to Earth's gravity and also the moon's gravity if it is located away from the pole of the moon. The wooble may allow faster release of the payload.   Neil

The rotating semi polar tether zips by a thousand operational low earth orbit satellites per hour. Collision will occur eventually, unless there are climbers which can whip a portion of the rotating tether out of the way. Climbers are also needed to inspect and repair the tether in much the same way as Dr. Brad Edwards has planned for the space elevator.
Let's try some arithmetic: tether length = 2000 kilometers. Circumfrence of rotation = 6283 kilometers. Low altitude tip speed is orbital speed minus 12,566 kilometers per hour. A tip dips into the exosphere at 15 minute intervals, providing multiple attachment opportunities to most of the nations of Earth, daily. Both tips have a rocket motor which can assist in making a sucessful attachment at about 10,000 kilometers per hour. In the second following payload release from the delivery craft, the payload drops like a rock as the tether streatches. Then a compression transcient arrives, subjecting the pay load to perhaps 10g, and straining the teher close to the breaking point. If necessary the tip motor can minimize the g load and/or the strain on the tether with a short burn. The pay load delivers make up fuel to the tip rocket. About 14 minutes latter the pay load is approaching maximum altitude = about 2100 kilometers. The tip motor may do another short burn to assist the tether in doing a 'snap the whip' at the moment of pay load release at perhaps 40,000 kilometers per hour (orbital speed plus tip speed). The tip motor can also fine tune the direction the pay load is flung. Neil

In my recent "low tech asteroid habitat" thread, I suggested a good reason for a small habitat near the far end of the ribbon. The only other uses are small waystations, in case a passenger panics, gets sick or the elevator car needs repairs. What I don't understand is how these manned stations can be attached to the ribbon without interfering with lifters and elevator cars not making that stop. Can someone explain?   Neil

~This is a paste from a comment reguarding the interview of Dr. Brad Edwards about the proposed space elevator~ Something no one ever mentions: how is the multi-ton lifter supposed to grip the ribbon all the way up? The ribbon starts out narrow and thin (30×1mm?), at the ground, just big enough to support a lifter, which has (many!) pairs of drive wheels gripping it. It has to get wider and, maybe, thicker, higher up, to hold up both the cars and the part of the ribbon hanging below. At the top it’s got to be big enough to hold up 36M meters of ribbon, and all the cars you have running. The ribbon can only get so thick and have the car still be able to grip it. Does it just get wider, with the part further from the edge rolled up? Or will it look like a regular cable, higher up, with a ribbon attached along one edge?

Presumably there has to be more than one ribbon — at least one for traffic up, and one down.
~The starting dimention I saw was 200 mm by 0.01 mm (average) so a lot of strengthening threads can be added before the ribbon thickness is difficult for the squeezing rollars. A cross sectional area of about 2 square mm produces a volume of 2000 cubic millimeters per meter of length = 2 million cubic mm per kilometer of length = 0.2 trillion cubic mm for a length of 100,000 kilometers. A cubic meter has a billion cubic mm; 200 cubic meters = 400 metric tons is the mass of the starter ribbon, assuming an average density of two. Some early thinking was for an even thinner starting ribbon, but it now appears that 2 square mm may not support a one ton lifter = climber plus the 400 ton mass of the ribbon. Most of the 400 tons is at reduced gravity. Please comment, refute and/or embellish. Neil~

Attaching at nanoscale might be better, but the lifter = climber needs to attach on the fly at several hundred kilometers per hour to stay ahead of the micro meteorite etc damage.  Even though nanoscale aeeachment seems impossible, we should likely try, because glue may work poorly.
It seems to me, ribbon width is not a problem as a lower mass, 8 inch climber can squeeze off center a 15 inch ribbon wasting 7 inches or conversely, the more massive, 15 inch climber can squeeze on center an 8 or 10 inch ribbon.
I have not heard a plan for re-using the climbers after they reach the 100 kilometer far end, so each production run of climbers can be a bit wider.
If some of the early climbers are refurbished after the ribbon reaches three feet or one meter, then a 16 inch climber can possibly pass a 19 inch climber in opposite directions by using both edges of the ribbon.  I'm guessing, of course.
The ribbon will continue to need daily repair (and daily inspection) long after it is fully operational, so provision for passing is important, in my opinion.   Neil

Class O,B, A, F and G stars have been rather rare the past 5 or 10 billion years, but they may have been a much higher percentage in the early years of our galaxy. If so, a trillion white dwarfs, nuetron stars and black holes with 5 to 50 solar mass may be crusing our galaxy. Most of them are likely cold and have negligible accreation disk. Would they occult = eclipse distant stars if they were closer than 100 light years? If they partially eclipse, perhaps we should be looking for individual stars that dim briefly. Such a program should also help find space junk, asteroids, comets and tiny moons. Neil

My guess is a tether made of short pieces of CNT will be 10 ohms per foot or more. Are long nano tubes as conductive as the same diameter of copper wire? If we put aluminum or lithium inside the nano tubes do we improve the conductance significantly? We need high conductance = low ohms to discharge the Van Allen Belt and/or produce a strong enough magnetic field to protect the CNT. Likely it is less costly to splice in a new peice of tether = ribbon monthly to replace the 0.01% of the tether damaged by the Van Allen Belt and/or molecular oxygen in Earth's upper atmosphere.   Neil

For this idea, we need a habitat near the far end of the elevator instead of the ISS = international space station.
Here is a paste from   www.space.com  
How about a space craft for two (mother and daughter) docked at a modified ISS. The ladies will catch the next slow asteroid that passes Earth closer than the Moon. Three days in space. The ladies dig as deep into the asteroid as practical and excavate a tiny habitat. Inflate something like an above ground swimming pool liner with 3psi of 98% oxygen = a sphere with an airlock. They live inside, until technology improvements make return to Earth practical. The ladies have a sperm bank and an embryo bank, so they can make babies, if they wish. Unmanned supply rockets bring them food and other essentials to last a century, thus removing one reason for these colonists to be stressed. They can post on www.space.com if they get bored. My guess is lots of volunteers, even though it is
sort of like being in prison, until we figure a way to make life more varied for these colonists in a tiny habitat touring the inner solar system. We can do two of these by 2012 if we make a major effort? Surely by 2025 if modern civilization lasts that long.
We can launch 100 supply craft (carrying a room addition for the habitat) in random directions (if we don't mind being extravagent) before we identify the first asteroid that might make a successful habitat. That way, supplies can be delvered 200 million kilometers from Earth, if closer delivers failed. Neil

Can't comment much on two ladies wishing to be cooped up in Asteroid for 100 years, but I am really interested in technology surrounding the excavation of asteroids (and the moon for that matter). In settlement scenarios, we always envisage digging under the surface - but are there any plans for anyone to try to start to explore thsi technology? I read once of a University team wanting to send a robot to the moon to start dusting an area.......... Oh wait a second, we're not talking robotic diggers, but ladies armed with space shovels!  

Hi: Digging into the asteroid may be the show stopper, especially if it is solid iron/nickel. I considered a rocket engine at both ends of the asteroid lander. The hotter engine would melt and vaporize into the asteroid while the engine with slightly more thrust held the craft in optimum position. The craft would likely need to cool for an hour for each minute it dug, so that is not an optimum solution, but perhaps workable. Most kinds of mechanical drills will require a thuster to keep the drill in working position as a tiny asteroid has essentially no gravity. The system needs to be usable for all types of asteroids as we likely cannot evaluate below surface composition in the seconds we may have to make a go/no go decision when the near approach of a 50 meter asteroid is detected. Most asteroids that small have not yet been charted.
Hopefully the ladies and their children will be cooped up 10 years instead of 100 years. Their heroic feat should inspire us to a much increased space effort. Neil

There is already a (mostly) low tech human colony in solar orbit.

It is called earth.

Perhaps you've heard of it?

 I've got a million of 'em.

Silence is golden. Duck tape is silver.

Depending on the composition of an asteroid, a TBM could do the job quite nicely.

Of course, there's those pesky little details like lifting and transiting a 400 ton TBM TO an asteroid, assembling it, maintaining it and supplying sufficient power to operate it.

But it's not impossible.

I suppose TBM = tunnel boring machine. Can you design a 4 ton TBM that works in free fall. Will it bore iron nickel? can it tolerate 1% diamonds and/or CNT = carbon nano tubes? Neil
 
Not sure of the mass of the machine, but there are commercially available machines down to the 1 meter size. They, of course, could be made lighter by using more exotic metals or composites

An asteroid that is mostly gravel, should be little challange for a modest digging machine. If all else fails, the ladies will need to use hand tools.
How about three narrow beam coded beacons on the asteroid, plus one wide beam beacon centered on the air lock. Can the unmanned supply rocket find a habitat and dock without any human assistance? Neil

Oops! I reduced my number to 12 kilometers, which may still be optimistic.    www.skywindpower thinks a multiple rotor unit can lift perhaps 14 kilometers of two conductor tether to 35,000 feet altitude, but I don't think they have tried it yet. CNT = carbon nanotubes to reduce miscelanious weight is likely necessary to make any design cost effective and/or reach the jet steam more than rarely.   Neil

I've often heard that removing space junk is very costly, but we will soon have private companies flying to low Earth orbit. Suppose NASA pays ten million and 12 million for two remote controled craft, and pays a third company to fly them by remote control. A costly computer program is needed to decide the order in which 10,000 peices of spacejunk are sent to burn up in Earth's atmosphere. Each craft has a laser array, which burns a tiny crater in a peice junk at distances up to 1000 kilometers. The vaporised material is ejection mass which propels the junk in the opposite direction like a very short burn rocket engine. Since the junk is typically tumbling end over end, it will be necessary to recalulate after each laser pulse perhaps 0.01 seconds long. The object is to get the piece of junk to burnup completely in Earth's upper atmosphere. Law suits are likely after the first piece reaches Earth's surface intact, and lawsuits are very costly even if the company proves their innosence. Low earth orbit is a huge volume, and the 10,000 pieces are typically spaced more than 1000 kilometers apart, so the two remote controlled craft may only destroy ten peices of junk perday average for 900 days to get rid of 90% of the space junk. Each craft will likely need to be replace several times in the 900 days because it was damaged by space junk or ran out of fuel for the laser array and for manuvering. It looks like it might be possible to destroy 90% of the space junk for one billion dollars, which is a bargain in my opinion.   Neil

I was also impressed with www.skywindpower.com  but I was told the wind speed data at their website was likely more than typical, so multiple fan units might only produce 100 kilowatt-hours per month, worth perhaps $5, so payback would be too long, unless the cost was very low.  The cost of the tether is likely half the total cost as it must be strong, long, lightweight and able to send several kilowatts to the ground without losing half the power.
I suggested tethering two assemblies together with a few kilometers of non conducting tether. The pair would be free flying and produce power from the wind speed and direction difference between the two ends. The electricity would power a cell phone transponder which would cover an area the size of a large state when the pair flew as high as 12 kilometers including locals that may never get continous cell phone service. Other communications and weather data would also be valuable at the other end. The system would operate at low voltage instead of the very high voltage tether which might be dragged across the ground in populated areas when the tether failed perhaps due to terrorists.  Neil

I wrote this about radiation on the surface of Mars, but much of it relates to the SE in Earth's upper atmosphere and higher.

Radio waves are same as on Earth's surface, except for the man-made radio waves of Earth, with some exceptions. These have little or no effect on biology or ribbon materials, except at intensities that rarely occur except inside microwave ovens. Very strong EMP = electomagnetic pulse will vaporize the ribbon, if it is configured to be electricly conductive.

Earth has three? times the infrared at the surface due partly to greenhouse effect. This makes Mars too cold for most kinds of life/ much of tropical Earth is too hot for some species of life. The ribbon may need to handle temperture changes exceeding 100 degree c = 180 degrees f per second, when compressed by the rollers. The mono frequency infrared beam that powers the climbers will also heat the ribbon significantly, perhaps dangerously, if the ribbon is already hot for other reasons.


Mars averages about the same visable light (and near ultraviolet) as Earth, because negligible clouds and the thinner atmosphere offsets 40%? less visable light from the sun. This is good news for photo synthesis and solar energy.
The rest of the ultraviolet spectrum is reduced by ozone and other things in Earth's atmosphere by about ten, so this (harmful to life and ribbon) radiation is stronger on Mars.

X rays and gamma rays are minor problems to life on Earth's surface. On Mars they are harmful during solar flares, sun spots and CMEs = solar mass ejection. These will degrade the nano tubes over periods of years, perhaps sooner.

Helium nuclii, electrons, and hydrogen nuclii = protons and some other kinds of ionized particles are about ten times more hazardous on Mars due to the very thin atmosphere and lack of magnetic field. This is likely true of the comparatively rare particles from outside our solar system, some of which arrive at nearly the speed of light. Some of these will degrade the nano tubes over a period of years, perhaps sooner.
Neutrons may also be a significant hazard on the surface of Mars and on the ribbon. Sorry there are so many kinds of radiation.    Neil

For an hour or so following the launch of each climber, the average tension at the anchor point will be about zero. As this climber and others enroute to the far end move outward, anchor point tension will increase slowly. When the tension reaches the mass of the next climber, the next climber can be launched (assuming acceptable conditions along the entire length of the ribbon) taking the anchor point tension back to about zero. Assuming the ribbon breaks close to the anchor point (when the tension is about one ton) the low end will accelerate at 0.01g toward space assuming the total low end mass is one hundred tons. The low tension transient will follow the last climber up the tether at perhaps 500 kilometers per hour. There is no indication along the tether that it not anchored until the low tension transient arrives as much as 200 hours after the break. There is no big rush to repair the break. The closest climbers can increase their speed, sending a low tension transient back down the tether, cancelling the acceleration toward space for as much as all day, while a helocopter unwinds ribbon from the anchor point until it reaches the broken end now moving downwind at constant average altitude.
With the break repaired, it may take a week to get the slack pulled out of the longer ribbon near the anchor point and get transients and future tension within acceptable limits, so more climbers can be launched.
A break far from the anchor point, could loose the entire ribbon farther out than the break (into solar orbit?) unless prompt action was in place to take care of such a contingency. Please embellish, refute and/or comment.   Neil