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

I can't settle the disagreement, but perhaps I can muddy the waters. It seems to me that a vast array of transients will propagate slowly, but perhaps strongly up and down the ribbon. Some may even continue past GEO stationary altitude and reflect off both ends repeatedly.
The stretch = tension transients may allow the climber or elevator to ride the transient like a surfboard reducing at least a little the energy needed from the lasers. At an average speed of 500 kilometers per hour, it will take 200 hours for the climber or elevator to travel the entire 100,000 kilometers, so we don't want to go much slower.
We could have a dozen widely spaced vehicles moving simultaneously on the ribbon, so there could be 100 transients of significance to monitor. Each climber should have transient analysis telemetering and some fixed location telemetering is also desirable. On occasion a climber or elevator needs to reverse direction briefly and/or fire a short burn rocket to modify a possibly dangerous transient. My guess is nothing needs to be done 99% of the time other than modify slightly the estimated arrival time.   Neil

While encouraging the government and indivduals to do more and make sacrifices we should make some sacrifices ourselves.
Most (60%?) locations are a bit warmer than a few decades ago. This recent trend could begin to reverse next week, leading to new ice age disasters next year or next decade. We should continue to make modest investments in research and do engineering studies both large and small scale. We should actually build one or two each of mid scale projects that attempt to reverse global warming and other potential polutants.
In my opinion we should reduce natural polution instead of manmade, if we can show that the side effects will less harmfull. Capturing carbon dioxide and methane from swamps and near volcanos should prove more cost effective than capturing polutants from smoke stacks. Please embellish, refute and/or comment.   Neil