Space Elevator in a nutshell

Tom Kalbfus · 2016-04-10 10:31:06

Here is an interesting video that sets up the basics of a space elevator
http://holykaw.alltop.com/space-elevator-work-video

RobertDyck · 2016-04-10 11:22:53

Dreams are nice. Study always learned more. But a space elevator has major problems. Technological problems were (briefly) described in the video. However, there is one major issue that proponents choose to ignore. The elevator cuts through every orbit from the ground to GEO. A few new satellites could be in a harmonic with rotation of the elevator (once per day), but all existing satellites below GEO would collide with it. And most low and medium orbits would no longer be available, because they collide with the elevator. But proponents don't want to face that. Like an impetuous two-year-old: "I want! I want! I want!"

Tom Kalbfus · 2016-04-10 21:14:55

RobertDyck wrote:

Dreams are nice. Study always learned more. But a space elevator has major problems. Technological problems were (briefly) described in the video. However, there is one major issue that proponents choose to ignore. The elevator cuts through every orbit from the ground to GEO. A few new satellites could be in a harmonic with rotation of the elevator (once per day), but all existing satellites below GEO would collide with it. And most low and medium orbits would no longer be available, because they collide with the elevator. But proponents don't want to face that. Like an impetuous two-year-old: "I want! I want! I want!"

Correction, a space elevator cuts through every equatorial orbit up to geosynchronous orbit. Most low Earth orbiting satellites don't orbit directly over the equator along the equator, which is where a space elevator would be located. All orbits cross the equator at some point, but most of those points would not be where the space elevator is! The Earth's equator is 40,074 km long, there are many points along that equator, that a satellite can cross, where the space elevator won't be, and on those rare occasions where a satellite is on a collision course, the satellite simply makes a course correction to miss the space elevator, and as the Earth rotates under its orbit, the next orbit will likely be a complete miss. The probability of any one satellite being at the same place as the space elevator at the same time, is very small. Space is 3 dimensional, most of the satellites won't be orbiting at the same orbital plane as the space elevator. The first space elevator will be very thin, the chances of any satellite snipping it are very small. as the space elevator grows thicker, it can support more things. For example a maglev rail, and a sleeve. A sleeve would be a hollow tube surrounding the space elevator, supported by cables attached to the space elevator, or perhaps will be a separate space elevator unto itself. An object would hit the outer sleeve and vaporize completely, doing some damage to the sleeve, but then that is what it is there for to absorb damage from orbiting debris.

SpaceNut · 2016-04-10 21:31:51

http://www.satview.org/

http://earthobservatory.nasa.gov/Featur … tsCatalog/

Tom Kalbfus · 2016-04-10 21:51:17

Yes, there are a lot of satellites orbiting the Earth, but those satellites shown in the picture are not shown to scale! They are very tiny, and space is vast! There are probably more airplanes flying in the atmosphere than their are satellites orbiting Earth. the satellites in low Earth orbit cross the equator at many different points. the ones that are active have maneuvering systems, that can be used to change their orbits to miss the space elevator, the others that are defunct would need to be gotten rid of, but even so, the chances of any one hitting the space elevator is very small, because the space elevator itself would be very small or have a small profile. the only dimension where it is not small, would be its length, however with width and breath would be very tiny indeed, it would be a small target for any of those satellites to hit, and most won't by trying to hit it!

If the space elevator got snipped, it would be a total loss for the space elevator, but then the solution would be simply to build another one. After lifting one million tons to orbit, it would have paid for itself, it can also lift the seeds for other space elevators. and a space elevator that is a thin ribbon, would most likely not survive reentry into the atmosphere, so there is no wrap-around crater, the elevator would not be thick enough to produce such a crater, and carbon nanotubes would burn up in the atmosphere very easily under the heat of reentry!

RobertDyck · 2016-04-10 21:57:56

Tom Kalbfus wrote:

Correction...

*EVERY* orbit crosses the equator. That's because every orbit is centred on the core of the Earth. Low orbit has a short period, ISS orbits every 90 minutes or so. ISS altitude changes due to atmospheric drag from the thin whisp of atmosphere at that altitude, then gets reboosted by each cargo spacecraft. Russia cargo ships carry propellant to refill tanks on Zvezda and Zarya, those modules have thrusters to allow ISS to reboost itself. When Europe flew ATV, it carried propellant as well. Lower orbit results in shorter period. But a space elevator crosses every orbit twice: once on north-to-south side, once south-to-north. The only exception are geostationary orbits, which orbit the Earth once per day as well, so they're always a certain number of degrees ahead or behind. Satellites could be launched into an orbit with a harmonic of the space elevator's rotation: twice per day, three times per day, four, etc. ISS orbits about 16 times per day. Then position the satellite so it's on the opposite side of the Earth when the space elevator crosses its orbit. Or some reasonable distance away. But current satellites aren't. And as I just described with ISS, anything in LEO is constantly changing orbital period.

RobertDyck · 2016-04-10 22:05:05

Tom Kalbfus wrote:

Yes, there are a lot of satellites orbiting the Earth, but those satellites shown in the picture are not shown to scale! They are very tiny, and space is vast!

May 2009: Mid-Air Collision Monday, Two Light Planes Destroyed

The image is of jumbo-jets, and the article talks about light planes, so the news website had to scramble for an image. But you get the idea. And I watch a TV program called "Mayday". It said the first accident in the US that prompted creation of the NTSB was a mid-air collision of two passenger planes. It happens.

With the number of satellites in orbit now, there is a branch of the military that tracks everything. Orbits have to be calculated to not intersect other satellites. One reason every launch has to be approved by government. Failure to address this issue is guaranteed to cause collision. It's just a matter of time.

Tom Kalbfus · 2016-04-11 05:27:27

RobertDyck wrote:

Tom Kalbfus wrote:
Correction...
*EVERY* orbit crosses the equator. That's because every orbit is centred on the core of the Earth. Low orbit has a short period, ISS orbits every 90 minutes or so. ISS altitude changes due to atmospheric drag from the thin whisp of atmosphere at that altitude, then gets reboosted by each cargo spacecraft. Russia cargo ships carry propellant to refill tanks on Zvezda and Zarya, those modules have thrusters to allow ISS to reboost itself. When Europe flew ATV, it carried propellant as well. Lower orbit results in shorter period. But a space elevator crosses every orbit twice: once on north-to-south side, once south-to-north. The only exception are geostationary orbits, which orbit the Earth once per day as well, so they're always a certain number of degrees ahead or behind. Satellites could be launched into an orbit with a harmonic of the space elevator's rotation: twice per day, three times per day, four, etc. ISS orbits about 16 times per day. Then position the satellite so it's on the opposite side of the Earth when the space elevator crosses its orbit. Or some reasonable distance away. But current satellites aren't. And as I just described with ISS, anything in LEO is constantly changing orbital period.

What's more valuable, a space elevator or our current constellation of satellites? I suppose all our active satellites could be deorbited under their own power. A space elevator could easily replace them, launching new satellites would be much cheaper using the space elevator, and launching ships which can collect all the dead satellites should be cheaper as well. With a space elevator, we should be able to clean up near Earth space.

I got another idea for a space elevator as well How about one around Saturn? Saturn has a rotational period of 10.2336 hours, and the synchronous orbit for it is at a radius of 109,275 km, Saturn's equatorial radius is 60,268 km thus a space elevator around Saturn would be 49,007 km long. This puts synchronous orbit in the middle of Saturn's B ring. On Earth the distance is 35,786 km, or 29,386 km after subtracting Earth's radius. That means a Saturnian Space Elevator would be 19,621 km longer than an Earth Space elevator. Fortunately Saturn has rings, the closest ones are at 66,900 km from the center, the furthest ones are 480,000 km from the center. These rings could be used as construction materials for the Elevator and the rest can be used to support the weight of the elevator at various distances from Saturn, using an orbital Space Fountain concept, in other words transferring some of the momentum of the ring particles to the space elevator to support its weight. Helpfully, most of these ring particles all orbit in the same plane. The bottom portion of the elevator could dangle within Saturn's atmosphere. The elevator could be used to mine Saturn, and to get humans and other cargo into and out of Saturn's atmosphere without expending too much rocket propellant. Saturn's atmosphere would be valuable in a fusion economy, especially when it comes to obtaining that rare element Helium-3. Saturn is probably the most hospitable gas giant for humans, (although that isn't saying much) The gravity is about the same as Earth. (Varies with latitude due to Saturn's spin) Saturn could be said to be the warmest gas giant with Earth-normal gravity, but more importantly, it is closest to Earth, Uranus and Neptune are further away. Saturn's ring system could be used to help extract Helium-3 from Saturn's atmosphere. People could also live in Saturn's atmosphere either dangling at the end of a space elevator or by using hot hydrogen balloons to remain aloft.

Last edited by Tom Kalbfus (2016-04-11 05:28:09)

JoshNH4H · 2016-07-27 20:54:46

One thing I've been thinking about lately is that a space elevator might be more useful as a power conduit than as a means of transportation.

Hold your skepticism. I know Zubrin's take on the matter. But Zubrin's analysis was done a long time ago and can't take into account advances since. He certainly (and probably wisely) did not take into account possible future advances.

For the purposes of this post, I'm going to ignore the questions of the space elevator itself. Posit that we have materials with a tensile strength of 100 GPa if you'd like.

The basic idea is pretty simple: Space transport is small change relative to energy. This website indicates that in 2015 we launched 365 tonnes of stuff into space. Valued at $5,000/kg, this represents about $1.8 billion in launch services. In comparison, the global energy market is about $5 trillion per year, or about 2,500-3,000 times more. Capturing 1% of the global energy market would be more valuable than capturing 100% of the global launch market, and it's not even close.

There are good reasons to believe that solar power makes more sense in space than on Earth, too. There are a few thing about Earth that make it a less-than-ideal base for a solar power farm. The Earth is:

A rotating sphere
With an atmosphere

On a rotating sphere, it is nighttime half of the time and high noon for only a moment out of the day. This means that the insolation will be reduced by a factor of pi. Solar panels with tracking motors can reduce these losses somewhat, but nighttime is unavoidable. On top of that, if the panels are too closely spaced one will shadow another later on in the day. A loss factor of two is unavoidable. Realistically, it will be about 2.5 even with tracking motors.

The atmosphere also reduces insolation with clouds and gases that block various spectra of the Sun's light. This probably reduces insolation by 1/3, or a factor of 1.5.

Put together, these will reduce insolation by 3.75. That is to say, while a solar panel orbiting the Sun at one Earth radius will see 1366 W/m^2, one on the Earth will only see 365 W/m^2, even with a tracking array. If you can simply transmit this energy down a space elevator with High Voltage DC power (to minimize losses), you can perhaps cut costs relative to producing it on the ground.

Beyond that, you've also got a good reason to do energy intensive manufacturing processes such as Aluminium smelting in space, possibly from ores mined up there.

Thoughts?

Antius · 2016-07-28 10:39:30

A skyhook from a platform in Low Earth Orbit is a near-term intermediate step that is technically much easier and does not require the use of exotic materials. The tether could be constructed from Kevlar or carbon fibre reinforced polymer. The tether and counter-weight must be ~100 times heavier than the payload being lifted, so capital cost would be significant, but could be amortised over a large number of launches. It would appear that a skyhook deployed using a single heavy lift vehicle would have sufficient mass to lift objects about 1tonne in mass into orbit. This could include satellites or small modules for assembly of a larger space craft.

https://en.wikipedia.org/wiki/Skyhook_(structure)

Wiki references a Boeing study into a rotating skyhook with a ground-relative tip speed of 3.6km/s at a height of 100km. To reach that speed and altitude by my calculation would require a booster vehicle with total delta-V of 3.86km/s – probably closer to 4.5km/s when drag and gravity losses are factored in. This would place the tip within reach of a single-stage LOX/Kerosene reusable sub-orbital rocket plane. Maybe a ramjet assisted propulsion system could be used to improve mass ratio.

Due to the much lower final velocity of the space plane, re-entry issues would appear to be much less severe, as the plane would re-enter the Earth’s atmosphere with something like a quarter of the specific kinetic energy of the space shuttle. Using LOX/Kerosene and a single stage, the vehicle may turn out to be quite cheap to operate. This is something that could be accomplished relatively soon and at a cost of billions rather than trillions. Having invested in the ISS, maybe a skyhook is the next logical step for the space faring nations.

GW Johnson · 2016-07-28 11:06:31

Hi Josh, long time no see. Hi Tom & RobertDyck. This is an intriguing conversation. Cannot comment on Antius's skyhook idea, I know nothing about those yet.

I translated Josh’s 100 GPa strength to 14.5 million psi, just because I think better in US units. That's several orders of magnitude higher than any known materials, unless you just look at individual fiber strength. And not many of them. I think I remember the strength of an individual iron crystal as being on the order of only 1 million psi. The best alloy steel materials known are only about 280,000 psi.

I know that carbon nanotubes themselves are incredibly strong fibers. I also know they are very short and exceedingly tiny in diameter. There is only one way known to put fibers like this together into a macroscopic form we can use: twist them together into a thread or string or twine, and then braid those into ropes or cables.

The twisting of fibers into thread or twine works almost entirely by plain fiber-to-fiber friction. Within a small species-dependent variation, this is the same basic friction mechanism for any fiber you care to name. This is a fundamental and inherent limitation. There is no basic science, much less any process or technology, to support any other way of doing this.

Create such science and develop it into a real technology, and you make possible space elevators. Until it exists, elevators are but an interesting concept that we cannot actually put into practice. Sorry, but it really is that simple. It’s not so much the fiber strength, it’s the strength of whatever form it is when you combine them, that is important to the finished material strength.

That is why I am relatively unimpressed by lab reports about incredible fiber strengths. So far, we cannot make any use of it.

As for the collision problem, RobertDyck is correct: there's a swarm of satellites whose orbits periodically cross the position of any space elevator, so a collision is eventually certain.

There's also 10's of thousands of bits of uncontrollable space junk in those same crossing orbits, tracked by radar, and of centimeter size or larger. When you consider tiny thinks like paint flakes, it's 10's, if not 1000's, of millions. Collisions are thus dead certain, and on a time scale of days, not years. And even paint flakes have proven dangerous.

Earth is not a good candidate for a space elevator because of the traffic and debris problem, even if the science and technology existed to build one (it does not). As long as we need satellites not in geosynchronous orbits (and we do), this risk will obtain. Maybe by the time the science and technology exists to create the elevator materials, we won't. But you cannot count on that, you have to make it happen.

As for an accident causing reentry of an elevator structure, do not count on the materials burning up to save the people and assets below.

I would point out that the body parts of the flight deck astronauts from Columbia's flight deck landed unburnt in east Texas. Scorched a tad, but not burnt. That breakup occurred at Mach 12-ish and 40-ish miles up at the TX-NM border. Their trajectories landed them about 600 miles downrange from breakup.

The ballistic coefficient for a human forearm flying broadside is around 20+ kg/sq.m, and far higher end-on, so you cannot claim "low ballistic coefficient rapid deceleration kept them from burning up". That argument applied to the uniform patches, not the body parts.

I would also point out the debris from Skylab that fell on western Australia in 1979: of the 85-90 tons at entry, about 75 tons of debris was recovered. The actual final breakup occurred after entry was over, at near Mach 1 at around 20,000 feet. That's also the conditions where Columbia's cabin was crushed, killing the 3 mid-deck occupants just prior to impact.

A couple of years earlier than that, Cosmos 954 fell into Great Slave Lake in Canada. That one was powered by a nuclear reactor, made of refractory metals and ablative high-temperature graphite in its core. Most of that landed in the lake. I still laugh when I remember Russian claims at the time that it was designed to burn up on reentry. No way in hell that was true. That was nothing but CYA PR.

And, a piece of the propellant plumbing from John Glenn's Atlas booster was recovered from an African beach. They identified it positively from the serial number. That was a Mach 25 entry inside an aluminum shell so thin it had to be pressurized in order not to crush under its own weight. Yet the internal pipe survived to impact.

These things do not burn up the way "everybody says". They are lying, or lying-by-omission, for CYA purposes. The only reasons no accidents occur all the time from falling debris are two-fold: (1) probability of a hit on a given small target is low, and (2) care is taken to dump them in the ocean, where the fish are unable to complain about it.

These are all things to consider when we do finally become capable of building such things. Myself, I would guess it will be easier to solve the wireless power transmission problem (in a safe way!!!) than the space elevator material problem. Solve that, and a power satellite becomes very feasible.

GW

RobertDyck · 2016-07-28 23:28:06

GW Johnson wrote:

The twisting of fibers into thread or twine works almost entirely by plain fiber-to-fiber friction. Within a small species-dependent variation, this is the same basic friction mechanism for any fiber you care to name. This is a fundamental and inherent limitation. There is no basic science, much less any process or technology, to support any other way of doing this.
Create such science and develop it into a real technology, and you make possible space elevators. Until it exists, elevators are but an interesting concept that we cannot actually put into practice. Sorry, but it really is that simple. It’s not so much the fiber strength, it’s the strength of whatever form it is when you combine them, that is important to the finished material strength.

Well... They have made some progress. A small square catalyst will grow a "forest" of carbon nanofibres. They used to say the longest fibres were 1/10th of a millimetre long. One company bragged they grew fibres 1/3rd of a millimetre long. Still, not useful. I talked to a chemist friend to brain-storm this problem, and posted our solution on a few internet forums. My chemist friend suggested somehow pulling the fibres to produce continuous extrusion. He thought the limiting factor was gravity; once a fibre grew so far it's own weight would prevent the chemical reaction that caused it to grow. So my idea was to use a Post-It note, grab all the fibres with the glue and pull them. The reason for using a Post-It note is the glue is weak enough to peal off without damaging the fibres. Then one lab that specializes in carbon nanofibres tried it. He even used the exact same brand name: "Post-It" manufactured by 3M. The fact he used the same brand name tells me he read my post and tried it. He found it worked!

If he pulled at an angle, not straight up, then the fibres combined to form a ribbon. The ribbon was translucent, and stiff. He later tried to twist while pulling from the catalyst, producing a more traditional twisted fibre cable. He found the cable was more supple that way. Detailed analysis revealed the individual fibrils were still only 1/10th of a millimetre long, but combined to form a continuous ribbon or cable. They're called "fibrils" instead of fibres because they're so small. Within a ribbon, these fibrils are held together by Van der Waals force.

In physical chemistry, the van der Waals' forces (or van der Waals' interaction), named after Dutch scientist Johannes Diderik van der Waals, are the residual attractive or repulsive forces between molecules or atomic groups that do not arise from a covalent bond, or electrostatic interaction of ions or of ionic groups with one another or with neutral molecules.

The toes of a Gecko are covered with tiny fibres, these fibres produce van der Waals' force to stick to a wall.

So this is a means to produce a cable or ribbon without hooks. Wool or cotton have scales that act as hooks to hold tightly twisted fibres together. Carbon nanotubes are smooth, they don't have hooks or scales. But Van der Waals' force works instead. The result is a cable that's very strong, but still only a fraction of the strength of an individual fibril. Military has even found how to make entire sheets of this stuff, and it's stronger than graphite fibre, but still only a fraction of the strength of an individual fibril.

Strength of a fibril of carbon nanofibre is more than enough for a space elevator. However, current technology to manufacture a ribbon is not.

JoshNH4H · 2016-07-29 19:51:35

Hi Antius, GW, and RobertDyck,

Good to see you again also! While the discussion of the practical aspects of building a space elevator is both interesting and a precondition for using a space elevator as an electrical power conduit, I'm a bit more curious about the economics of doing so.

While I'm quite interested in the skyhook/rotovator concept, it's not useful as a power conduit and therefore has much less potential than the space elevator concept.

Over 36,000 km of space elevator, power losses are going to be an important question. I've heard HVDC lowers power losses, but how low can we go?

SpaceNut · 2016-07-29 20:01:27

I got thinking about the use of the power and the earths atmosphere to keep the tower from falling down (ion engine or some other chemical engine that could basically run none stop) if the base of the tower stopped say near space elevation and continued to orbit. One would launch from earth to the end of the tower and simply climb the rest of the way to orbit using the power coming down to the vehicle that is climbing.

GW Johnson · 2016-07-30 12:11:14

Well, when V is higher, I is lower, and so is I^2 R. Excluding superconductivity, that's how you reduce I^2 R losses: raise the voltage. True for both AC and DC. It's easier to reduce a really high AC voltage down to something you can really use, because there are no DC transformers.

If your space elevator (made of some blend of unbelievium, manurium, and unobtainium, of course, ha ha) had two conductors side by side kept separated by an insulator, then those two charged conductors are essentially a toy electric train track. Whatever keeps your space elevator charged just needs the power capacity to run the cars that travel upon it. Lionel knows how to do that. Mine has run since 1952.

I worry about electron flow off of charged surfaces in vacuum. What limits this in the atmosphere is the breakdown voltage for arcing through the gas. I simply do not know how much voltage difference you can support in vacuum. I think it's more likely "high" than "low", but I cannot quantify those words. Electricity is somewhat outside what I do know really well.

GW

Last edited by GW Johnson (2016-07-30 12:12:51)

RobertDyck · 2016-07-30 12:35:41

Carbon nanofibres are conductive. If carbon atoms are arranged helical around the fibre, then it's a semiconductor. If atoms are arranged in a straight line along the fibre, then it's a conductor. And the conductor has less resistance than copper, and can carry 1,000 times as much current as aluminum for a cable of the same diameter. Not 1,000 times as much as copper, but more than copper too. Resistance isn't 1/1000th; the difference for electrical resistance (impedance) is not as great.

I've said for a while that long distance power transmission cables should be made of this stuff. Reducing power loss means more power gets to the customer, which makes the power utility more profitable because more of the power produced is actually billed. And reduces carbon emissions because any power plant that burns fuel will produce smoke (carbon emissions), and more efficient transmission means you can reduce how much power is produced in the first place.

However, as a space elevator? Any conductive space elevator will be a giant lightning rod. What do you think would happen to a carbon cable struck by lightning?

IanM · 2016-07-31 00:13:29

RobertDyck wrote:

Any conductive space elevator will be a giant lightning rod. What do you think would happen to a carbon cable struck by lightning?

Nothing good, especially if it shorts out any engine keeping it up and thus causes it to collapse. Perhaps in theory there could be an insulative sheath covering the actual carbon, like the plastic coverings of electrical cords. But while such things have negligible or at least manageable weight with your household extension cord, I wonder how much it would weigh at the scale of a space elevator? If it's too heavy, that would complicate things immensely. There might already be an insulator light enough to do the job, but if there isn't, that means that there would be yet another material to be developed.

SpaceNut · 2016-07-31 09:07:10

The superconductivity has thus far only been with temperature control and with ceramics for the conductor of the power, which means they would tend to be brittle and quite fragile.

Things that effect power are the number of phases, the frequency of the cycle of ac and yes the media use to transmit it to the object using it. So what happens with more than 2 conductors growing to 3 or 4 means or more means we would spread the power accross more therefore reducing the amount power that each will see. Changing the ac frequency also has an effect on the transformer coupling needed to drop the voltage levels back down as it will reduce the transformer mass.

JoshNH4H · 2016-07-31 16:38:48

GW:

Regarding breakdown and arcing, the problem seems manageable. I would imagine that for stability reasons the structure of a space elevator would actually be quite wide (a few kilometers? I see no reason why not) and therefore any issues related to arcing would be reduced to very manageable proportions, especially because there are a limited number of charge carriers in the vacuum.

I wouldn't be so worried about lightning either. Atmospherics are only relevant for the bottom 50 km or so in a cable that's 36,000 km long. It could be coated with insulation. For that matter, relative to building down 36,000 km building a compressive tower to meet the tether at an altitude of 50 km doesn't seem all that crazy either.

I'm definitely not opposed to using CNT as a conductor, if we find that it lives up to its promise. Since I'm already speculating with unobtanium for the tether it's certainly not crazy to speculate with unobtanium for the conductor. Maybe superconductors will be economical by then, which would be great.

I was under the impression that, in order to step down DC, you had to rectify it to AC, step down the AC current, and then rectify it back to DC (For our purposes, we probably would just leave it as 120 VAC). It's a second step which makes it less efficient but is still quite doable.

SpaceNut · 2016-07-31 18:16:05

The initial dc to ac conversion is to be coupled with an ac to dc charging unit for battery storage as solar will only be available for under 12 hours for lower part of the tower and a bit more for the upper portion. To make the most of solar the panels need to be tracking even if we place them at specific distances from the bottom to the top. The lower panels that are in the atmosphere would cause drag on the tower so we need to keep this to a minimum...

Space elevators needed for space solar power?

This is the typical base built elevator that reaches space....
Space elevator by 2050 planned, to include space solar power

JoshNH4H · 2016-08-01 11:49:34

Actually, solar panels located at the top of the tower would have a nearly unfettered ability to point themselves directly at the Sun because they are so far from Earth. Given the relatively small forces involved, a boon that is a few thousand kilometers long could certainly be built which would allow them to be in permanent sunshine.

SpaceNut · 2016-08-01 17:36:47

Agreed that the higher they are the better so lets focus on the counterweight requirements...to elevator mass....

http://users.wpi.edu/~paravind/Publicat … vators.pdf

http://www.niac.usra.edu/files/studies/ … dwards.pdf

https://en.wikipedia.org/wiki/Centripetal_force

http://physics.bu.edu/~duffy/py105/Circular.html

https://www.lhup.edu/~dsimanek/scenario/centrip.htm

JoshNH4H · 2016-08-01 18:11:57

I think the best way to do a space elevator is to extend the tether to its maximum length, that way you can get the highest possible delta-V out of it

SpaceNut · 2019-09-03 20:59:41

Sometimes our newest of topics on a subject are not to fresh so here is a wake up.

Pull Me to the Moon: Scientists Revolutionize Space Lift Concept to Save Cash on Lunar Missions

This is a twist to have the cable stretching from the moon back toards earth. So long as the mass of the cable is not more than the moons. If in contact its got to be on some sort of slip ring for it to stay in alignment with earth.

Just get into orbit, hook onto the end and start climbing all the way to the moon.

tahanson43206 · 2020-04-10 05:22:49

For SpaceNut .... re this topic ...

Terraformer recently introduced Space Elevator in his vision of a triangular trading relationship between Ceres and two trading partners.

At one point in the discussion, you suggested continuing the discussion of space elevators elsewhere, and I was not surprised to find this topic from the olden days of the forum.

As the messages I read so far have made clear, a space elevator looks like an unlikely technology to expect to see at Earth, but it most definitely has potential elsewhere in the Solar System.

I searched for my battered copy of Brad Edwards and can't find it.

What I do NOT remember from Edwards is a discussion of how to manage angular momentum.

Terraformer introduced the idea (interesting to me) of using ion engines to replace angular momentum consumed by a mass being lifted from the surface of the primary body.

The insight that came to me recently is that the elevator vehicle itself could provide the angular momentum it needs to stay in alignment with the cable, by delivering ions in abundance to the anti-spinward side of the cable.

(th)

New Mars Forums

Announcement

#1 2016-04-10 10:31:06

Space Elevator in a nutshell

#2 2016-04-10 11:22:53

Re: Space Elevator in a nutshell

#3 2016-04-10 21:14:55

Re: Space Elevator in a nutshell

#4 2016-04-10 21:31:51

Re: Space Elevator in a nutshell

#5 2016-04-10 21:51:17

Re: Space Elevator in a nutshell

#6 2016-04-10 21:57:56

Re: Space Elevator in a nutshell

#7 2016-04-10 22:05:05

Re: Space Elevator in a nutshell

#8 2016-04-11 05:27:27

Re: Space Elevator in a nutshell

#9 2016-07-27 20:54:46

Re: Space Elevator in a nutshell

#10 2016-07-28 10:39:30

Re: Space Elevator in a nutshell

#11 2016-07-28 11:06:31

Re: Space Elevator in a nutshell

#12 2016-07-28 23:28:06

Re: Space Elevator in a nutshell

#13 2016-07-29 19:51:35

Re: Space Elevator in a nutshell

#14 2016-07-29 20:01:27

Re: Space Elevator in a nutshell

#15 2016-07-30 12:11:14

Re: Space Elevator in a nutshell

#16 2016-07-30 12:35:41

Re: Space Elevator in a nutshell

#17 2016-07-31 00:13:29

Re: Space Elevator in a nutshell

#18 2016-07-31 09:07:10

Re: Space Elevator in a nutshell

#19 2016-07-31 16:38:48

Re: Space Elevator in a nutshell

#20 2016-07-31 18:16:05

Re: Space Elevator in a nutshell

#21 2016-08-01 11:49:34

Re: Space Elevator in a nutshell

#22 2016-08-01 17:36:47

Re: Space Elevator in a nutshell

#23 2016-08-01 18:11:57

Re: Space Elevator in a nutshell

#24 2019-09-03 20:59:41

Re: Space Elevator in a nutshell

#25 2020-04-10 05:22:49

Re: Space Elevator in a nutshell

Board footer