Monday, January 29, 2007

CONSTRUCTING GEO PLATFORM

GEO Node, Natural Transition Point
Consider as start point for any climber, the Up-Link Marine Anchor.  Thus, it's natural to assume that all climbers must first start as Up-Link climbers which must ascend the Up-Link tether to reach the Up-Link GEO Node; then, that climber will transition to either Out-Link or Down-Link. 
At the top end of the Up-Link tether and the bottom end of the Out-Link tether, GEO Node is the natural transition station between Up-Link and Out-Link.  However, many Up-Link climbers will not continue outward from Earth on the Out-Link; instead, many Up-Link climbers will be "tugged" by special vehicles over to a separate, dedicated Down-Link tether.
At geosynchronous altitude and zero-g conditions, GEO Node will off-load and on-load cargo to the tether climber. As an assembly facility, GEO Node can fully enable satellites after their rise from the ocean; they will then go to their operational location. 
This station could do following tasks:
---From Up-link climbers, GEO Node will off-load satellites going to the planets
---GEO Node will host a facility to initiate such satellites for operations. 
---GEO Node will on-load them onto Out-link climbers for subsequent travel beyond GEO.
---GEO Node will monitor them till they depart the climber into their high energy trajectories.
---GEO Node will remove climbers from the tether and transport them to a Down-link tether for descent. 
NOTE: For Downlink tethers to stay taunt, they will need their own Outlink with a terminal AA which will need mass.  Thus, some outward bound climbers could shuttle (via space tugs) from Up-Link's GEO Node to Down-Link's GEO Node and instead of going down to Down-Link's Marine Anchor, go up to Down-Link's AA, on the way accomplish release of payload then continue to become part of Down-Link's AA.
---It will also receive spent satellites as mass for the Apex Anchor. 
---Dead satellites could be mated with the climber for release into disposal orbits or return them to earth.  CONSTRUCTING GEO PLATFORM depends on receipt of numerous materials, components, supplies and people delivered via the space elevator vessels.
GEO Platform and the Space Elevator are interdependent.  (I.e., platform holds the cable for climbers to go up; however, initial climbers must carry many components up to GEO to build the platform which can't hold the initial cable because it's not there; a classic "chicken and egg" problem.)
Such dependencies greatly shrink if g-force elevators use a fusion engine like a tokamak. 
Recall that an Earth surface bound "particle accelerator" sends a constant beam of high speed particles to propel the Space Elevator Vessel (which replaces "climber" used by traditional space elevator cable).  
Vessel could use a large magnetic dish to collect particle beam ions and ingest them into the vehicle's tokamak engine.  
TE assumes tokamak engine could itself expel a portion of the collected ions as high speed particles to contribute a significant momentum exchange to propel vehicle.  1-G propulsion would be desired; however, a lesser acceleration would still get the vehicle from Earth to GEO in a fairly short time (compared to traditional "climber" which might take as long as 5 days to travel the 22,000 mile cable from Earth surface to GEO.
TE further assumes that initial vehicles could autonomously decelerate to "park" at GEO orbit directly above Base Station.  These initial vehicles could deliver initial components to construct GEO Platform which will prove essential for full scale operation of an Enterprise Space Elevator; however, platform won't be required for initial deployment.
SIDEBAR: Tokamak
is a magnetic confinement device, and it is one of the most-researched candidates for producing controlled thermonuclear fusion power. 
It uses magnetic fields to confine ions (i.e., plasma, stuff of stars) because any solid material cannot withstand plasma's extremely high temperatures.
Tokamak is a torus (i.e. "doughnut  shaped") device with specific dynamic, magnetic field lines in a helical shape.


Generate a helical field by combining:
1) toroidal field (particles circle around the torus) produced by electromagnets around the torus
2) poloidal field (travels in circles orthogonal to the toroidal field) from a second set of electromagnets inside the torus.
Construction
Constructing a space elevator requires some advances in engineering, manufacturing and physical technology.  After the first space elevator, subsequent elevators benefit from experience well documented in associated Project Management Plan (PMP).
Prior to the 2000 work of Edwards, most construction concepts called for the cable to be made in space. Manufacturing the cable in space could use an asteroid or Near-Earth object for source material.  PROBLEM: Such concepts require a large space-faring infrastructure to make large quantities of high precision materials in space. Paradoxically, this infrastructure should include the space elevator; however, it doesn't yet exist; thus, the space elevator cannot be used to construct itself.
Since 2001, most Space Elevator work has focused on simpler methods. EXAMPLE:  A space elevator enterprise could launch and orbit a satellite containing a large spool with a long cable. The spool could be initially park in a GeoStationary Orbit (GSO) above the planned anchor point. The long cable could deploy "downward" (toward Earth) and would be balanced by an equal mass deployed "upward" (away from Earth) for the whole system to stay on the GSO. 

Safety issues and construction challenge

For early systems, transit times from the surface to the level of geosynchronous orbit would be about five days. On these early systems, the time spent moving through the Van Allen radiation belts would be enough that passengers would need to be protected from radiation by shielding, which would add mass to the climber and decrease payload.[59]
A space elevator would present a navigational hazard, both to aircraft and spacecraft. Aircraft could be diverted by air-traffic control restrictions. All objects in stable orbits that have perigee below the maximum altitude of the cable that are not synchronous with the cable would impact the cable eventually, unless avoiding action is taken. One potential solution proposed by Edwards is to use a movable anchor (a sea anchor) to allow the tether to "dodge" any space debris large enough to track.[2]
Impacts by space objects such as meteoroids, micrometeorites and orbiting man-made debris, pose another design constraint on the cable. A cable would need to be designed to maneuver out of the way of debris, or absorb impacts of small debris without breaking.xxxxxxxxxxxxxxxxxx

60000 miles up: Space elevator could be built by 2035 .

Imagine climbing a ribbon 100,000 kilometers long, stretching from the surface of the Earth to well past geostationary orbit (GEO).  The International Academy of Astronautics (IAA) predicts cliimbers will simultaneously carry up to seven 20-ton payloads at once. 

This tether will stretch far beyond GEO orbit, and it will attach to an anchor of roughly two million kilograms. Sending payloads up this backbone could fundamentally change the human relationship with space; every climber transit could match the space shuttle in capacity, equivalent to a “shuttle launch” every day or so.


elevator diagramIAA 350 page report lays out a detailed case for the space elevator. It presents a detailed accounting of the challenges. The pay-off is greatly reduced cost; cost-per-kilogram of launch to geostationary orbit shrinks from $20,000 to as little as $500.
Not only is a geostationary orbit intrinsically useful for satellites, but it’s far enough up the planet’s gravity well to be able to use it in cheap, Earth-assisted launches. A mission to Mars might begin by pushing off near the top of the tether and using small rockets to move into a predictably unstable fall — one, two, three loops around the Earth and off we go with enough pep to cut huge fractions off the fuel budget. Setting up a base on the Moon or Mars would be relatively trivial, with a space elevator in place.
IAA's projections for launch mass over time with different technologies.
IAA’s projections for launch mass over time with different technologies.
Those are not small advantages, and are worth significant investment from the private sector. Governments and corporations spend billions installing infrastructure in space — an elevator could easily pay for itself, and demand investment from anyone with an interest in ensuring cheap access to it down the line. A space elevator is relevant to scientists, telecoms, and militaries alike — and with Moon- and asteroid-based mining becoming less hare-brained by the minute, Earth’s notorious resource sector could get on-board as well. It will certainly be expensive, probably the biggest mega-project of all time, but since a space elevator can offer a solid value proposition to everyone from Google to DARPA to Exxon, funding might end up being the least of its problems.
This report lays out a number of technological impediments to a space elevator, but by far the most important is the tether itself; materials science has still to invent a substance that could provide the strength, flexibility, and density needed for a space elevator. Existing technologies will be little help; tethers from the EU and Japan are beginning to push the 100-kilometer mark, but that’s still a long way off orbital altitude, and the materials for existing tethers will not allow much additional length.

Projecting current research in carbon nanotubes and similar technologies, the IAA estimates that a pilot project could plausibly deliver packages to an altitude of 1000 kilometers (621 miles) as soon as 2025. With continued research and the help of a successful LEO (low Earth orbit; anywhere between an altitude of 100 and 1200 miles) elevator, they predict a 100,000-kilometer (62,137-mile) successor will stretch well past geosynchronous orbit just a decade after that.000 miles up: Space elevator could be built by 2035 ... - ExtremeTech

https://www.extremetech.com › Extreme

Mar 6, 2014 - When you get right down to it, how do you build a space elevator? The proposed design really couldn't be simpler: a sea platform (or super-ship) ... IAA hopes for a seven-day climb from the base to GEO — slow, but still ...

Audacious & Outrageous: Space Elevators | Science Mission Directorate

https://science.nasa.gov/science-news/science-at-nasa/2000/ast07sep_1

Sep 6, 2000 - Above: Artist Pat Rawling's concept of a space elevator viewed from the ... into space with its center of mass at geostationary Earth orbit (GEO), 35,786 km ... of the tower and cable structure going to platforms at different levels.




60,000 miles up: Space elevator could be built by 2035, says new study






When you get right down to it, how do you build a space elevator?

The proposed design really couldn’t be simpler: a sea platform (or super-ship) anchors the tether to the Earth, while a counterweight (also called an “apex anchor”) sits at the other end, keeping the system taught through centripetal force. Though many have dreamed of asteroid-capture missions to wrangle a space rock into being our anchor, the IAA points out that such a mission would likely require a space elevator to be possible in the first place.
Instead, the report argues that a nascent space elevator should be anchored first with a big ball of garbage — retired satellites, space debris, and the cast-off machinery used to build the elevator’s own earliest stages. Interestingly, a tether stretching 150,000 kilometers or more would have enough weight of its own to sidestep the need for a counterweight altogether. All tethers, no matter the length, will have to be made in a curved shape so no single edge-on micro-collision could sever the ribbon entirely — though at just a meter wide, a collision wouldn’t have to be very “macro” to cover the entire silhouette.
Climbers might well deploy huge solar arrays like this to power the climb past about 40 kilometers in altitude.
Climbers might well deploy huge solar arrays like this to power the climb past about 40 kilometers in altitude.
To keep weight down for the climbers (the elevator cars, if you will), this report imagines them as metal skeletons strung with meshes of carbon nanotubes — how would you like to ascend to space in a huge future-hammock? Each car would use a two-stage power structure to ascend, likely beginning with power from focused lasers fired from the ground, or with power sent down from a dedicated box satellite. Past 40 kilometers altitude, though, the climber’s own solar array should be able to keep it moving with light unfiltered by Earth’s atmosphere. IAA hopes for a seven-day climb from the base to GEO — slow, but still superior (and far cheaper) to the rockets that lead to months-long delays in launches today.

And more importantly, can we get the international cooperation to build such a mega a contraption?

In terms of placement, IAA is unequivocal: a space elevator would be too precious a resource to be built within the territory of any particular nation-state — they reference the Suez Canal as an example of the problems in giving a self-interested nation control over global infrastructure. Though every government would certainly love a space elevator of their very own, cost considerations will likely make that impossible in the near-term. Purely by virtue of its physical size, a space elevator will stretch through multiple conflicting legal zones, from the high seas to the “territorial sky” to the “international sky” to outer space itself. Each of these presents its own unique legal and political challenges. The US could very well find itself lobbying China for help in building a tether that will help in surveillance of Chinese territory — this will not be an easy project to plan.
A team works on the YES2 tether, which is more than 30 kilometers long and just half a millimeter wide.
A team works on the YES2 tether, which is more than 30 kilometers long and just half a millimeter wide.
Attacks by terrorists or enemies in war are also a major concern — though politically neutral, the eventual location of the Marine Stage One base station will immediately become one of the most aggressively defended no-fly zones in the world. It will be watched from beneath by underwater security, at altitude by radar sweeps and fighter patrols, and in space by nearby satellites. Notice that while this would be a stateless project, it would require a state’s assets to maintain — likely via the UN or some new autonomous body tasked exclusively with elevator defense.
Though there are several possible tether materials, carbon nanotubes are the most likely candidate.
Though there are several possible tether materials, carbon nanotubes are the most likely candidate.
Arthur C. Clarke once famously said that we will build a space elevator 10 years after they stop laughing — and they’ve stopped laughing. He said that in 2003, and while his timeline may have been off, his sentiment surely wasn’t. The concept of a space elevator is taken seriously at NASA these days, as it eyes both shrinking budgets and growing public expectations. Space is quickly becoming a bottleneck in the timeline of human technological advancement.
From mega-telescopes and surveillance nets to space mining operations and global high-speed internet coverage, most of our biggest upcoming projects will require better access to space than we could ever derive from tanks of combustible liquids. It’s simultaneously a boring infrastructure project and a wide-eyed dream machine, a mega-project that illustrates how further progress in space will necessarily require global cooperation. In the eyes of this report, that cooperation could end up being the greatest challenge of all.

Section 4.10 - Space Elevator (Skyhook) - Wikibooks, open books for ...

https://en.wikibooks.org/wiki/Space_Transport_and_Engineering.../Space_Elevator

Space Elevators have been a theoretical transportation method since 1895. ... If the center of mass is atGEO and matches the Earth's daily rotation it will ..... That way the landing platform will be in the same place each time relative to the ...

How Space Elevators Will Work | HowStuffWorks

science.howstuffworks.com/space-elevator.htm

Space elevators are explained in this article. Learn about space elevators. ... could make travel to Geostationary Earth Orbit (GEO) a daily event and transform the ... of a carbon nanotubes composite ribbon anchored to an offshore sea platform ...

In the future could the space elevator may be possible ? - NASA ...

https://forum.nasaspaceflight.com/index.php?topic=28876.60

Dec 2, 2014 - 20 posts - ‎12 authors
If it were to go to a GEO Synch platform then maybe you would be ok. .... to orbit, would be to... have aspace elevator with magnets all along it.

Escaping Earth: Could a Space Elevator Work? – Nat Geo TV Blogs

tvblogs.nationalgeographic.com/2011/.../escaping-earth-could-a-space-elevator-work/

Jun 16, 2011 - The notion of a space elevator has been around for a long, long time. ... $10 billion on a man-made floating base (either a ship or an oil platform ...

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