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//--------------------1--------------------
var faq = new FAQ("This is the quick answer book for the Space Elevator, largely independent of the specifics of the Elevator:2010 competition. \
These questions were compiled from questions we get at lectures, those we get by email, and questions science reporters always come up with. \
We do try to answer all of them - if you have a question that you think is not answered by the FAQ - please let us know!");
faq.enterSection("primer","Space Elevator 101",
"The questions that start most every SE conversation, ranging from the "hows" to the "what ifs", and everything in between.")
faq.enterQA("50words","In 50 words or less - what is the Space Elevator?",
"The Space Elevator is a safe and low-cost Earth-to-Space transportation system that does not use rocket propulsion. It is a physical stationary tether between the ground and an object in space, and a set of vehicles that can travel to space and back, moving on the tether using electric motors.")
faq.enterQA("whatsSpecial","What makes the Space Elevator better? What can it do?",
"The Space Elevator will carry very large loads to space - 10 and 100 times as much as rockets do, all without carrying a single ounce of rocket fuel, and with a quality of ride comparable to that of a modern train. With the Space Elevator in place, the true "Space Age" will truly begin.")
faq.enterQA("300words","In 300 words or less - what is the Space Elevator?",
" \
- The Space Elevator is a thin Carbon Nanotube based tether, with a cross-section area roughly half that of a pencil, extending from a ship-borne anchor to a counterweight well beyond geo-synchronous orbit. \
- The tether is kept taut due to the rotation of the earth (and of the counterweight) around the earth. At its bottom, it pulls up on the anchor as if to lift it out of the water, so tether is always under tension. \
- Electric vehicles, called climbers, ascend the ribbon using solar power assisted by a ground based booster light beam. \
- In addition to lifting payloads from earth to orbit, the elevator can also release them directly into lunar-injection or earth-escape trajectories, putting them on track to landing on solar system destinations as far away as the asteroid belt. \
- The baseline system weighs about 1500 tons (including counterweight) and can carry up to 15 ton payloads, easily one per day. \
- In space, the tether is shaped as a ribbon, 100,000 km [62,000] miles long, about 1 meter [3 feet] wide, and is thinner than a sheet of paper. \
- The climbers travel at a steady 200 kilometers per hour (120 MPH), do not undergo significant accelerations or vibrations, can carry large and fragile payloads, and have no propellant stored onboard. \
- Satellites and large pieces of orbital debris are avoided by moving the anchor ship. The ribbon itself is made resilient to damage from small-scale (e.g. paint chips) space debris. \
- The elevator can be made larger by using itself to carry more ribbon pieces into space. There is no limit on how large a Space Elevator can be. with time, the Space Elevator will lift hundreds, and then thousands of tons of payload at a time! \
");
faq.enterQA("fictionOrFact","Science Fiction or Science Fact?",
"The Space Elevator was first proposed in the 1960s by a Russian engineer (Yuri Artsutanov) as a far-reaching engineering concept. The scientific principles underlying it are well understood and do not require any fictional physical principles. \
To built the Space Elevator, however, the tether material has to be stronger than any material that existed at the time, and so the concept has been relegated to the status of science fiction, and as such it appeared in several books, the most famous of which is Sir Arthur C. Clarkes The Fountains of Paradise. The Space Elevator described in the book, however, is of immense size and is probably not practical any time soon. \
In 1991 a new class of molecules was discovered - carbon nanotubes (CNTs) - which were predicted and then measured to have the strength necessary to build the Space Elevator.
\
This discovery prompted Dr. Bradley C. Edwards to propose the modern Space Elevator design in his now famous 1999 NIAC paper. This design differs greatly from the "science fiction" Space Elevators, and can be pursued even today.
\
The greatest hurdle on the way to the Space Elevator is the creation of a composite tether made out of CNTs that retains most of their native strength, and active development is now taking place in this field.
\
The image to the right is linked to Yuri Artsutanov's original article. To keep track of progress in tether technology, take a look at this page.",
"
Original SE article by Yuri Artsutanov
(Courtesy of Roger Gilbertson)");
faq.enterQA("whatWillRideBeLike","What will a ride in the Space Elevator be like?",
"The term "Elevator" is a bit misleading. Perhaps a better analogy is a large Gondola-type ski lift, except much larger, and moving vertically. \
The view will be grand. The ride up will occur at just over 100 miles per hour, so the ascent through the atmosphere and the gradual distancing from Earth will be a staggering site.
\
There will be none of the fire and acceleration of a rocket launch. The windows can be large, since the Elevator structure does not have to stand up to the rigors of launch. There will be no acceleration chairs, and passengers will be able to walk around throughout the entire ride.
\
Slowly, over the course of the trip, the passengers will notice that their weight is decreasing, until they will become completely weightless, just when they arrive at GEO, 25,000 miles above the surface of earth. \
The gondola itself will be large enough to house the passengers for 4-5 days, which means that a manned Space Elevator will be much larger than the initial 20-ton cargo-only Space Elevator.
\
See a more detailed description here");
faq.enterQA("howMuchCanItCarry","How much weight can the Space Elevator carry?",
"Space Elevators can be built in any size. Dr. Edward's "baseline" design considers a Space Elevator system capable of carrying 20 ton climbers, comparable to today's launch systems such as the Space Shuttle or an EELV.
\
It is just as feasible, however, to built a Space Elevator that can carry 2 ton or 200 ton or even 2000 ton climbers. This property (known as scalability) is extremely important - it allows us to start with a very small Space Elevator (to reduce development and operational risk) and to later grow it practically without limit, as space transportation needs reach into the million ton range.");
faq.enterQA("whenWillItBeBuilt","When do you think the Space Elevator will be built?",
"We believe all the fundamental challenges can be met by the year 2010 or thereabouts, and at that point it should be possible to begin the construction of the first Space Elevator by the year 2020.
\
Whether this will indeed happen is not a matter of technology, but of political circumstance, and this is much harder to predict. President Kennedy's "Place a man on the surface of the Moon ... by the end of the decade." promise showed how much can be achieved if there's a vision. With the Elevator:2010 project, we're increasing public awareness of the Space Elevator concept, in order to expedite its construction.
\
While the Space Elevator may seem a far off prospect, remember that all the transportation devices we're used to today - rockets, airplanes, cars - were all perceived as impractical only several decades before they became commonplace. The future is closer than it appears!");
faq.enterQA("whatsHoldingAir","What's holding the Space Elevator in the air?",
"The Space Elevator is perhaps the ultimate example of swinging a ball at the end of a string - except that the string is 100,000 km long, and the "person" doing the swinging is the Earth.
\
From experience, you know that the longer the string is, the more time it takes the ball to go around. With the Space Elevator, we make the string so very very long, that the ball takes 24 hours - one complete day - to go around.
\
Just like with the string and ball, since the system is constantly trying to fly out and escape the center of its rotation, the proper question is actually: "What's holding it down?". The answer to that is that we indeed have to keep the bottom of the tether securely anchored to the surface, and make very sure that we never let go!",
"
a very small Space Elevator");
faq.enterQA("whatIfItBreaks","What happens if it breaks?",
"The short answer is that (much like the ball-on-a-string example) the portion of the elevator above the break point flies outwards and into space, whereas the portion below the break point falls down to earth. \
With Science Fiction Space Elevators weighing billions of tons, this is a very bad thing for the planet. In reality, with the Space Elevator being a large stretch of thin ribbon, the impact of a falling Space Elevator would hardly be detectable. \
Given that the falling tether falls "equally" around the equator, each square mile will receive only several ounces of tether remnants.
\
We should also keep in mind that virtually all failure scenarios involve a break in the very bottom portion of the Space Elevator, in which case there will be absolutely no impact on the ground.
\
Still, we obviously do not want to see the Space Elevator break, and there are extensive measures to prevent that - read more about it in the "what-if" section below.");
faq.enterQA("HowPreventPlanes","How do you prevent planes from flying into it?",
"This is actually very simple - The Space Elevator will be a single well-known location in the middle of the Pacific ocean, surrounded by at least 100 miles of no-fly space - just like the White House, for example. \
One of the reasons for anchoring the tether to a ship is the ability to locate it away from any populated spot. Planes do not just fly blindly through the sky, or they would constantly collide with each other. \
There are many closed airspaces in the world, and in the middle of the ocean, away from any airport, an accidental collision between an airplane and Space Elevator is easily prevented.
\
A malicious attack is a different matter, of course, and one that has to be guarded against. However, the isolated location of the anchor point (eastern equatorial pacific) allows the restricted air space to be well enforced, guaranteeing that a plane that is detected on a course into the no-fly zone is not simply lost or confused.");
faq.enterQA("willItCarryPeople","Will it carry people?",
"Initially, the best use of the Space Elevator will be in constructing the large infrastructure necessary to support routine manned activity in space - space stations that can accommodate hundred, or thousands of people. \
This would be possible, since the Space Elevator will make it possible to lift much larger payloads to space than we can even imagine doing with rockets.
\
With time, the capacity of the Space Elevator will increase to the point where it can lift Jumbo-Jet sized payloads, and with that sort of capability, manned space access would finally become affordable and routine.");
//On the other hand, the concpet of a dinner trip to 250 km is quite feasible, although of course would be rather expensive!");
faq.enterQA("costToBuild","How much will it cost to build and operate?",
"The Space Elevator is a much simpler and less expensive project than the Space Station or a new type of rocket. With development and deployment included, the Space Elevator will cost well under $10B, which is a very reasonable price for a transportation infrastructure project.
\
Since there are barely any consumables, the cost per pound will be limited to the cost of operating the anchor and power beaming station, divided by the very large carried volume - the end cost will start at $100 per lb, and will quickly decrease from there.");
faq.enterQA("stateOfCNTReseach","What is the current state of Carbon Nanotube tether research?",
"Yearly production of CNTs is increasing each year by a factor of 10. This is turn is making it possible for CNT Composite research to speed up, since the raw materials required by the labs are easily obtainable. As an example, the 2007 Space Elevator games had a team bring in a pure CNT tether weighing 2 grams.
\
In order to track this projected progress, we have established the tether-strength tracking chart which shows how research is progressing in comparison to a reference curve that will get us to Space Elevator worthy materials in about 7-8 years.",
"
spool of CNT tether");
// 1 mm long CNT-based fibers with a strength of more than 20 GPa (compared to 2 GPa for steel wire) have been recently produced.. \
faq.enterQA("whyCompareWithTodaysRockets","Why do you compare the Space Elevator with today's rockets? won't we have much better rocket technology in 20 years?",
"There are several reasons why the Space Elevator represents a quantum leap beyond either current or future rocket technologies.
\
\
- Cost. All rocket designs are governed by the rocket equation, which means that even the rockets of the future will weigh thousands of tons in order to lift a truck-sized payload to LEO, or a car-size payload to GEO. (a 5-10% payload mass ratio) \
- Cost again. All rocket designs will have to burn tons of propellant every second in order to get going - such machines cannot be made cheaply. \
- Safety. For the same reasons, rockets cannot be made to be safe. The huge amount of stored energy means that even a small problem results in a catastrophic explosion. A Space Elevator climber can literally stop in its tracks if an anomaly is detected, and even slide back down if necessary. \
- Cost again. The Space Elevator offers the same cost to LEO, GEO, and Earth Escape trajectories. \
- Energy. A rocket wastes most of its energy as propellant heat and velocity - only a fraction of the energy goes towards pushing the rocket forward. A Space Elevator, on the other hand, derives most of its energy from the rotation of the Earth, and so needs to provide only a fraction of the energy - and even that, in the form of electricity. \
- Reliability. A Space Elevator climber is simply a set of photovoltaic panels and electric motors. Even the rockets of the future will remain much more complex machines, continuously balancing fire and ice as close to an explosion as they dare push their designs. \
- Quality of Service. Because of "gravity drag", rockets have to accelerate at many times the force of gravity, or they waste even more propellant against Earth's gravity. At such high forces, dynamic loads reach many tens of g's and the ride on top of the rocket becomes a very destructive experience. Most of the cost of building a payload goes into making sure it survives launch. A Space Elevator, on the other hand, transfers gently from 1 to 0 gravities, with no dynamic loads. The impact of this on the complexity, capabilities and cost of the payloads cannot be overstated. \
- Scalability. The Space Elevator can grow in a linear fashion - if we double the thickness of the tether and double the power beaming station, the system can carry twice as much load. If we do this every two years for 20 years, the system will be able to carry 1000 times as much load. Can we envision rockets increasing their performance x1000 in 20 years? \
- No fairing size limitation. Since it only moves through the atmosphere at slow speeds, the Space Elevator can haul up an entire radio telescope dish in once piece - no in-orbit deployment necessary, resulting in simpler payloads. \
- Quality of Service again. The Space Elevator can carry a communication satellite into space, test it in position, and bring it back down if it's not performing well. This sort of capability will do wonders to the insurance rates! \
- Reliability. No sub-nominal launches. Once the climber reached GEO altitude, the payload is in GEO - period. No circularization burn necessary, either. Gone are the days of launches-gone-wrong. \
- Up and Down capabilities. The Space Elevator is the only system capable of getting back down to Earth without the very risky maneuver of aero-breaking. \
\
In short, even though there is no doubt that rocket transport can get much better and cheaper than it is today (go SPACEX!), it has fundamental characteristics and inherent problems that cannot be circumvented. In the long run, if we want to create a real space-faring economy, we need a quantum leap in capabilities, something that only the Space Elevator can provide. \
This is not to say, of course, that rockets will become obsolete - in many ways rockets compare to the Space Elevator in the same way that airplanes compare to ships - ship are safe, slow, cheap, and can carry huge amounts of payload. Airplanes are used to carry things fast around the globe. This is not a perfect analogy, but it captures a lot of the inherent traits of the systems.",
"
Why rockets are expensive -
moon rocket and passenger. (to scale)");
faq.enterQA("moreWebInfo","Where can I find more information on the web about the Space Elevator?",
"There are plenty of web sites that have exciting information about the Space Elevator. A partial list includes: \
\
- Wikipedia has a good Space Elevator overview article.
\
- Ted Semon's very excellent news site and Blog. \
- Spaceref's Space Elevator Site \
- Blaise Gassend's pages \
- NOVA's recent video segment on the Space Elevator. \
")
faq.enterQA("SciFiBooks","Which works of Science Fiction feature the Space Elevator?",
" \
- Jack and the beanstalk - an interesting 1800's tale - read all about it \
here \
and here \
- Fountains of paradise, by Sir Arthur C. Clarke, the Space Elevator SF classic. buy at Amazon \
- The Mars color trilogy, by Kim Stanley Robinson, a chromology of mars colonization. \
Red \
Green \
Blue \
");
//--------------------2--------------------
faq.enterSection("basics","Basic Principles of the Space Elevator",
"This section answers questions about the basic principle of operation of the space elevator. This section can also be read in order for a pretty good introduction to the Space Elevator.");
faq.enterQA("stringOnEnd","How do you stand a string on end?",
"Unlike a magic rope, the Space Elevator is not supported by its base, and unlike a regular rope, it is not hanging from its top. \
The best way to look at it is that because of the rotation of the earth, the Space Elevator is hanging from the ground, and is falling into the sky.",
"
The Earth and the Space Elevator rotate in unison
",4);
faq.enterQA("howThick","How thick is the tether? How heavy is it?",
"One of the major steps taken by Dr. Edwards in his 1999 paper is the calculation of the overall size of the Space Elevator system. Given the strength of Carbon Nanotubes, a CNT tether capable of carrying 20 ton climbers would be less than 4 mm in diameter (~1/8"), and would weigh only 1000 tons - about the weight of 2 or three jumbo jets. Over 100,000 km, this works out to less than 1 ton per 100 km, or 10 grams per meter - 1/10 ounce per foot! \
The entire system, including the counterweight, would weigh only 2-3 times the International Space Station - definitely a project that is within reach today in terms of size.
\
Since the tether is so thin, Dr. Edwards realized that in the vacuum of space, for several reasons, it would make sense to abandon the natural round cross section of a string, and instead fashion the strands into a thin sheet - a ribbon - one that is several feet wide and thinner than a thousandth of an inch.");
faq.enterQA("whatsHoldingItUp","What's holding it up?",
"The Space Elevator is perhaps the ultimate example of swinging a ball at the end of a string - except that the string is 100,000 km long, and the "person" doing the swinging is the Earth.
\
From experience, you know that the longer the string is, the more time it takes the ball to go around. With the Space Elevator, we make the string so very very long, that the ball takes 24 hours - one complete day - to go around.
\
Just like with the string and ball, since the system is constantly trying to fly out and escape the center of its rotation, the proper question is actually: "What's holding it down?". And indeed, we have to keep the bottom of the ribbon securely anchored to the surface, and make very sure that we never let go...");
faq.enterQA("whatsHoldingItDown","What's holding it down then?",
"For many reasons, the bottom end of the Space Elevator (called the "anchor") is best placed on a ship located in the Eastern Equatorial region of the Pacific Ocean, west of Equador. The Ribbon will tug up on the ship with a force somewhat larger than the Space Elevator's capacity - 20 tons in the baseline design.");
faq.enterQA("whyLongerThanGEO","Why is the ribbon so much longer than the minimum 25,000 miles?",
"Theoretically, we could have done with a ribbon that is only one mile longer than GEO, but that would have required a very massive counterweight, since near GEO it is almost balanced and so is very ineffective at pulling the tether up. The farther the counterweight is above GEO, the smaller it needs to be. This is an optimization problem, and 50,000 miles (double GEO) is a good working point. \
A different way of looking at it is that since the ribbon has weight, we want to have as much ribbon above GEO as we want below it, more or less.
\
A second consideration is that the longer the ribbon is, the higher the velocity of its tip, and the faster it can sling objects out of Earth orbit. At 60,000 miles, objects flung from the tip can reach Mars and the inner asteroids, making it a very tempting design point.");
faq.enterQA("howDoClimbersTravel","How do the climbers travel on the ribbon?",
"The climbers use traction wheels and electric motors - no rocket science here. In science fiction, Space Elevator cars are assume to use linear induction motors and magnetic suspension, more similar to mag-lev trains. In practice, these solutions require a very heavy ribbon, one that will break under its own weight. The traction wheels are a very simple solution, though they do impose an upper limit on fast the Space Elevator climbers can travel.");
faq.enterQA("howtoPowerClimbers","How do you power the climbers?",
"The climbers carry thin-film solar foils, are are mostly powered by direct sunlight. The foils are active on both sides, and during the first night they are also illuminated by a strong booster light beam projected from the ground.
\
Under one proposal, several even lower intensity beams will converge on the climber, so we gain both redundancy, and the ability to make the beams eye-safe.
");
faq.enterQA("howDoYouGetItUpThere","How do you get it up there in the first place?",
""Getting it up there" is often referred to as deployment. The first (seed) ribbon has to be launched by rockets and then spooled down from GEO and captured by the anchor. From that point, the Space Elevator can make itself larger (thicker or wider) by hauling up new ribbon material. In this way, we can rocket-launch only a very light-weight elevator, reducing the number of required launches by a fair amount.
\
If fully dedicated to such "self growth", a Space Elevator can haul up its own weight in about 6 months.",
"
Spooled ribbon being deployed
",1);
faq.enterQA("How","How fast can it grow?",
"Based on the above considerations, if the Space Elevator dedicates 25% of its capacity to "self growth", it can double its capacity every 2 years. \
That is an amazing growth rate. The only other comparable growth-rate we know of is in the field of computers (also known as Moore's law), except that Moore's law is an observation, and the Space Elevator can acheive exponential growth by design.
\
This same property also allows us to start with a small (1/10 scale) Space Elevator, and grow the basic "full-scale" system from it. This will allow the entire Space Elevator to be launched in only 2-3 rocket launches, and the initial confidence-building operations to be performed on a smaller system.");
faq.enterQA("howMuchEnergy","How much energy does it take to launch a pound into space?",
"This question is often heard when trying to ball-park the minimum cost of going to space. With the Space Elevator, since we only have to provide the potential energy difference, this turns out to be a relatively low number: 60 MJ, or 17 kWatt-hour, per kg. \
This is about 50 cents worth of generated electricity. Since most of the electricity is provided by solar panels, the energy cost will be negligible .");
faq.enterQA("multipleClimbers","Can multiple climbers run on the ribbon at once?",
"Yes. In fact, that is the preferred mode of operation. Since climbers get lighter as they move up the ribbon, it actually makes a lot of sense to use climbers that are only 50% the maximum load, since they can then be launched much more frequently than twice as often.");
faq.enterQA("twoWayTraffic","How can you handle two-way traffic? Will there be more than one Space Elevator?",
"Multiple Space Elevators are possible, though there are some technical arguments against it. We believe this issue will end up being a political rather than a technocal one.
\
In the initial years, there will be much more "up" traffic than "down" traffic, so even if there is only one Space Elevator, it will be possible to declare a "down" week every couple of month to accomodate such traffic.");
faq.enterQA("goToMars","Can you use the Space Elevator to travel to Mars?",
"Yes you can. If you take the Space Elevator half-way up the ribbon, to GEO, you end up in Earth orbit. If instead you take the Space Elevator all the way to the end of the ribbon, you find yourself in the role of the ant clinging to the ball at the end of the string - if you time it just right, you can let go and fly out to the other side of the room...
\
An interplanetary boost using the Space Elevator is exactly the same thing, only with a 100,000 km string... The string only rotates once per day, but the speed of the tip is enough to send the payload well beyond Mars, even as far as the Asteroid Belt.
\
As a vehicle for exploration, the Space Elevator can place several tons on the surface of Mars each day, for little more than the cost of electricity.",
"
A payload launched to Mars
",1);
//--------------------3--------------------
faq.enterSection("challenges","Design Challenges and Solutions",
""It will never work!" ... This section addresses various factors that can make the design of the Space Elevator more chalenging. Also - \
"What will happen if?" ... If anything can go wrong, it will! In this section we also cover things that can go wrong during Space Elevator operations, and what we do about them.");
faq.enterQA("holdToPaperThinRibbon","How can you hold onto a paper-thin ribbon when the vehicle weighs 20 tons and is traveling at over 100 mph?",
"It is true that grabbing the ribbon with pinch-rollers is not going to work, but there are several other mechanical arrangements that will. The one we like the most is a capstan - the same principle that allows a hand-wound rope to prevent a ship from escaping its mooring, or allows a mountain climber to hold his entire weight with a slight tug on the rope. \
The speed of motion, as long as it is constant, does not affect this force.
\
There are other limitations on how fast the climber can handle the ribbon, and that's the reason for the 100 mph estimates travel speed.",
"
A capstan
",2);
faq.enterQA("atomicOxygen","What about atomic Oxygen?",
"Atomic Oxgen (AO) is Oxygen in its loose atom state (as opposed to O2 Oxygen molecules) that are created at the top layers of the atmosphere (100 - 500 km) and are very corrosive. \
Without preventive steps, AO will attack the ribbon (which has a very large surface area) and destroy it. \
As it turns out, a thin non-oxydizing metalic layer can protect the ribbon against such erosion for a considerable amount of time. Even this layer will have to be re-deposited by climbers as they go by, but this is a relatively straight-forward process. ");
faq.enterQA("Hurricanes","What about Hurricanes?",
"Luckily for us, hurricanes cannot form on or near the equator, where our anchor point is. Cyclonic weather systems are created by the Coriolis force, and so only happen at latitudes higher than 5 or 10 degrees.
\
"regular" weather systems can be an issue though, and one of the reasons the anchor is located on a ship is to be able to move out of the way of oncoming weather. With todays weather monitoring capabilities, the only reasons ships go through storms is that they can, and it's cheaper to go across than it is to go around. If the main directive of the anchor ship is to steer clear if storms, that should not be hard.
\
In addition, the atmospheric portion of the ribbon will actually be shaped like a regular tether, with a round cross section (about as thick as a pencil) to minimize interaction with wind.");
faq.enterQA("bottomRound","But if the bottom portion of the Space Elevator is not a ribbon, how will you climb it?",
"One very good suggestion is to reel in the round-tether portion when we want to launch, attach the climber, and release - the climber will float up like a Helium filled balloon. Once out of the atmosphere, the climber can start climbing the ribbon portion.
\
This proposal also removes the need to have a beaming station under the climber, and allows the climber solar array to be made lighter, since it never sees wind.
\
The lower ribbon part will of course enter the atmosphere, but only briefly, and we will avoid doing so if weather does not permit it.");
faq.enterQA("lightning","What about lightning?",
"A lightning bolt can indeed sever the ribbon, and there are several layers of defense against lightining. The most important one is the ability to move the anchor point. A ship can easily outrace a storm. The only reasons that ships go through weather is that they have a schedule to keep. \
If all a ship wanted to do was avoid storms, with the aid of modern weather forecasting, it can see blue skies indefinitely.");
faq.enterQA("tzunamis","What about tsunamis?",
"In mid-ocean, Tzunamis are no different than regular rolling waves, and compared to 100,000 km, even a 30 foot wave doesn't really seem all that large... As a matter of fact, in theory, the anchor ship can sink to the bottom of the ocean and the ribbon won't be affected.");
faq.enterQA("lasrCut","Won't the laser cut the ribbon?",
"The laser is a very high power system, but actually has a very low intensity - only about 2-3 suns. That's enough to give you a sun-burn pretty quickly, but not the sort of laser beam that drills through metal. Since the beam will always hit the ribbon at a very shallow angle, there won't be any heating problems associated with it.");
faq.enterQA("potentialDifference","There's a huge potential difference between the ionosphere and the ground - won't the ribbon make a short circuit?",
"Carbon Nanotubes, in some configurations, are super conductors. The ribbon's CNT composite, on the other hand, will likely be a pretty bad conductor. In addition, the ribbon is a very long resistor, so the resultant current will be small.
\
Another factor that will limit the current is the coupling between the ionosphere medium and the ribbon - the charge carriers around the ribbon will be quickly depleted. In short, while there may be some current going through the ribbon, it is not something that will affect it. To the curious, it will also not be enough to be a free source of energy.");
faq.enterQA("magneticCurrents","How about magnetically induced currents?",
"There have been several experiments where tethers released from satellites (or the Space Shuttle) measured significant induced currents, and some were even cut by associated arcing. These satellites, however, were moving through the Earth's magnetic field at several miles per second. The Space Elevator is a geo-stationary structure, and so does not move relative to the magnetic field, and so does not see any induced currents at all.");
faq.enterQA("wearAndTear","What about wear and tear on the ribbon?",
"Wear and tear happens after a very large number of cycles, similar to what an engine belt sees - several million cycles is typical. The ribbon is pretty much stationary, until a climber passes by, maybe once a day. This adds up to maybe a thousand passes throughout its life - not yet a wear-and-tear like number.");
faq.enterQA("collisions","How do you deal with the risk of collisions with satellites and space junk?",
"Space junk is a common term for orbital devris - the remnants of satellites past - shread of aluminum, paint flecks, larger pieces of metal from old and deteriorating satellites. \
All satellites and space debris move at several miles per second just to remain in orbit, but regretably, they all move in different direction, so a collision with a bolt at a relative speed of 10 miles per second is not good.
\
All orbiting object larger than a few inches are tracked by radar and telescopes and mapped using computers, so we can get plenty of warning if a collision if forecasted. The Space Station, for example, quite often uses its thrusters to avoid such collisions. \
This is one more reason the anchor point is located on a ship. As we move the ship, we move the entire Space Elevator, and so can avoid the collision too. ");
faq.enterQA("smallJunk","What about really small pieces of space junk?",
"It is true that we cannot track pieces below a certain size - probably 1 cm or so. Luckily, the shape of the ribbon - a wide and thin strip - makes it resilient to small holes. \
Damage from paint fleks and similar hazzards will accumulate statistically, and become one of the factors that will determine the life-expectency of ribbon material in space.");
faq.enterQA("meteorites","Can't a Meteorite sever the ribbon?",
"Unlike earth-bound space junk that keeps circling the earth, random bits of space rock cannot be mapped, and so cannot be avoided. Luckily, howver, since they are not Earth bound, the risk of a colliding with a meteorite is infinitely smaller than that of hitting a piece of space junk, and the density of Meteorites that are large enough to cause real damage is very very low.");
faq.enterQA("damageRepair","How will you repair damage to the ribbon?",
"The ribbons will be made from discrete segments. New segments will be introduced on a regular basis where the ribbon is thickest (in GEO) and removed at the anchor and counterweight locations.
\
This will address the problem of the accumulated damage and finite longevity of the ribbon material. Anecdotal damage will have to be addressed on demand, by replacing the damaged section. There are several procedures for doing this without jeoperdizing the Elevator.");
faq.enterQA("oscillations","What about oscillations?",
"The ribbon will be in a continuos state of motion - back and forth, sideways, and along its length. Many factors will contribute to that: wind loading at the bottom of the ribbon, lunar gravitaional pull at the top, pressure from solar wind, and movement of climbers.
\
In order to control thiese oscillations, we will have to actively damp them out using motion of the anchor ship, and by controlling the velocity of the climbers.
\
We should stress though that the Space Elevator is a very stable structure, and can easily swing hundreds of miles in each direction without any adverse effects.");
faq.enterQA("whatIfBreaks","What happens if the ribbon breaks?",
"If you knock out a floor of a high-rise building, the section of the building that is above the break will collapse on top of the bottom section. \
The Space Elevator, on the other hand, is a structure in tension, being pulled up by its counter-weight that is constantly trying to escape. \
As a result, if a break occurs in the ribbon, the portion of the ribbon that is above the break, along with the counter-weight, will fly out into the space, and the portion that is below the break will fall down. \
Since the ribbon is wide and thin, it cannot really move fast through the atmosphere - it will either slow down, break apart, or burn up, and will end up distributed around the equator. \
Assuming that on their way down, the remnants will scatter a few tens of miles sideways, the world will witness a sort of very thin ticker-tape parade, at an average density of a few ounces per square mile - hardly the world shattering event the is depicted in some Science Fiction books.
\
We should also keep in mind that almost all failure scenarios involve a break in the very bottom (1%) portion of the Space Elevator, in which case there will be virtually no impact on the ground at all.");
faq.enterQA("cntToxic","But aren't Carbon Nanotubes toxic?",
"There are several answers to this worry:
\
Loose Carbon Nanotubes are probably not good for you, but one should compare any potential scenario to naturally occuring ones. \
Forest fires, for example, generate tons of Carbon Nanotubes each year, and distribute them very efficiently into the atmosphere, often near population centers. \
A good sized volcanic eruption does the same with all sorts of nasty metals - toxicity is a function of concertration, not only of the material itself.
\
In addition, the ribbon's CNT composite is different than loose CNTs, and is likely not to be toxic. CNTs will not break out of the composite unless they are subjected to very high reentry temperatures, somthing that can only happen in the very high layers of the atmosphere. In such a case, the CNTs will end up over a much wider corridor, reducing their concentration even further. This case is only relevant if we have a break high up the ribbon, which is a less likely scenario.");
faq.enterQA("recovery","If the ribbon ever breaks, how will you recover?",
"Once the first Space Elevator is constucted, we can use it to built a second Space Elevator, or just keep a spooled stand-by Space Elevator at GEO to act as a back-up, ready to be deployed if the first one fails.");
faq.enterQA("explodingPayloads","What about exploding payloads?",
"A payload exploding while on the ribbon stands a very good chance of breaking it. Note though that in the entire history of Space Launches, this has never happened, and rocket launches are very rough on their payloads.");
faq.enterQA("paloadIfBreaks","what will happen to the payload if the ribbon breaks?",
"Unless the payload is most of the up, it will fall down back to earth and reenter. For cargo payloads, this is the only way a launch can go wrong, and should be factored in as an acceptable risk. For manned climbers, they will have to be designed with a one-time thermal protection system, similar to what can be found on Soyuz capsules.");
faq.enterQA("terrorists","What about terrorists?",
"When an aircraft carrier sails through the ocean, it enforces a no-fly zone around it. \
Since the anchor is ship-based, we will be able to place it in international waters, away from any inhabited land, and do the same thing. \
The Space Elevator will be the most important structure on Earth, and we will have to protect it accordingly. A 100 mile restricted zone is plenty enough to protect it against almost any form of sabotage.");
faq.enterQA("laserWeapon","Can the laser be used as a weapon?",
"The laser produces a very wide beam - it is a high power, but low intensity laser. You probably don't want to stand in the light for more than a few minutes, but such a beam is useless as a weapon.");
//--------------------5--------------------
faq.enterSection("alternates","Alternative Proposals",
""why don't you do it this way?" ... Questions about other ways to build the Space Elevator.");
faq.enterQA("condutPower","Isn't it possible to simply conduct the electricity up the ribbon",
"The short answer to this one is no. Remember that the whole Space Elevator concept (literally) hangs on the strength-to-weight property of the ribbon material. \
While carbon nanotubes can superconduct under certain conditions, the final tether material will likely not be, and so the conductor will have to be added separately - which will increase the weight of the ribbon several fold, but will not add any strength - making the Space Elevator impossible to construct. \
Another consideration is that with a MegaWatt worth of power flowing through the conductor, and a length of thousands of kilometers, the voltage drop will be large, and will require extensive insulation layers between the conductors - resulting in an even higher mass penalty.");
faq.enterQA("powerExchange","Can you use the energy generated by the down-moving climber to power the up-moving climber?",
"Don't we wish we could... While the Space Elevator is very energy efficient, pulling off a trick like that would have made it practically energy-neutral! Regrettably, we can't come up with a way to transfer power between the climbers.");
faq.enterQA("solarPower","Can you use solar energy from collectors on the counter weight or in GEO?",
"Again, we wish we could, but there's no elegant way of doing this. The power beam is best generated on Earth since the highest power requirement on the climber occur when it is in Low Earth Orbit - this way we only have to beam full power when the range is under 6000 km (as opposed to 40,000 km if we're beaming from GEO). Also, while the power beam is not that dangerous, we'd rather have it on the ground and pointing up than in space and pointing down.");
faq.enterQA("batteries","Could you use advanced batteries to lift the climbers?",
"Current battery technologies store two orders of magnitude (100x) too little energy per pound in order to be useful. A climber carrying enough batteries for the trip to space will be too heavy to lift itself up - we'll be back to the Rocket Equation and climbers that are 99% stored energy. Mechanical batteries (flywheels) are also a possibility, but they are only marginally better than chemical ones.");
faq.enterQA("fuelCells","Could you use Fuel Cells?",
"For large amounts of energy, fuel cells are more mass efficient than batteries, but they present us with two problems: safety (large amounts of explosive fuel and oxygen on board) and thermal consideration, as discussed in the next questions.");
faq.enterQA("nuclearPower","Could you nuclear power packs?",
"Nuclear power sources, just like fuel cells, fall into a category of engines called "Thermal Engines" which share a common property that prevents us from using them. \
Thermal engines are governed by a law called Carnot's law which states that they must exhaust their heat at a low temperature in order to be efficient. Regrettably, another law called Newtons's Law states that in space, you cannot get rid of low-temperature heat. \
Caught between Carnot and Newton, thermal engines are incapable of generating enough power per weight in order power a Space Elevator climber.");
faq.enterQA("skiliftElevator","Can we add pulleys at the counterweight and anchor, double-up the ribbon, and operate the elevator like a giant closed loop? We pull down on one end, and up comes the other?",
"That's one of the more appealing alternatives, since it completely does away with any power systems on the climber. The problem is that it only works with a constant-cross-section ribbon, and as we explain elsewhere, the taper on the ribbon is essential. \
Other problems include the very large counter-moving mass of the double-ribbon which represent a lot of stored energy, and a potential problem with electric charge build-up (this will be the world's largest Van-der-Graaf generator).");
faq.enterQA("disposableElevator","What if we use a simple elevator structure, but keep feeding ribbon from the bottom.",
"This ideas has merit if we manage to build a taper-less Space Elevator. Since the bottom of the ribbon is pulling up anyway, why don't we just keep adding material at the bottom, and chopping up pieces at the top? \
Such an idea would get around the obstables presented by the closed-loop elevator, and the cost of launching payloads will be exactly that of the new ribbon material we add. Such an elevator will have to be made longer than 100,000km, since it cannot use a counterweight.");
faq.enterQA("multipleLegs","Could you split the bottom leg of the Space Elevator in order to provide redundancy?",
"We can, and this is actually a viable proposal. Since most of the risks to the ribbon (lightning, terrorists, etc) occur near its base, a split anchor design would provide insurance against such failure, at a very modest cost.");
faq.enterQA("liftWithSecondTether","Could you put a motor on the counterweight, and use a thin tether to raise and lower the climbers?",
"The problem with this proposal is that the "thin" tether, much like the main Space Elevator ribbon, has to mainly carry its own weight, so has to be as thick as the main ribbon, and weigh as much, and so the motor will have to raise not 20 tons but 1000, and the main cable will have to support its weight too - and therfore become thicker itself... you can see where this is going...");
faq.enterQA("balloons","could you use balloons to support the bottom of the ribbon?",
"The heighest we can fly a balloon and still carry noticable load is about 25 km, a very small fraction of the 35,000 km total distance to GEO... The weight of the cable below the balloon is only 250 - 500 kg, so the benefit is small. The penalty in terms of wind drag is pretty high though, so overall, it's probably not a good idea.");
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faq.enterSection("applications","Future Application","This section tries to answer the "why" questions. To some of us, this is the simplest section to answer - what do you mean why go to space? haven't you seen 2001? ... But still, the question is worth answering in a very detailed way");
faq.enterQA("","What's the first thing you'd do once the Space Elevator is built?",
"The first operational Space Elevator, capable of lifting 10-20 tons at a time, will lift, per year, about as much as the rest of the world's rockets. So the first thing we'll do, naturally, is service the existing market at significantly lower costs and risks, and with a much nicer ride to orbit. This market byitself is enough to financially justify the Space Elevator.");
faq.enterQA("","What about scientific applications?",
"Imagine what the Hubble Space Telescope could do if its optics did not have to be built to withstand launch, or fit into the fairing of a rocket.... Imagine what Mars exploration could look like if instead of sending a 250 kg payload once every two years, we could send out a 10 ton payload - once every couple of days... With vastly increased capacity, we will be limited only by our imagination.");
faq.enterQA("","Can the Space Elevator help with the battle against global warming?",
"The short answer is Solar Power Satellites. These are essentially solar cell farms, but located in space rather than on the roof of your house. A solar cell in space makes about 10 times more electricity than a cell on earth, since sunlight is more than twice as strong, is available at full power 24 hours a day, there are no clouds, and there's no dust accumulation. \
These solar farms are the only proposed method to generate electricity with virtually zero impact on the ecology. With the Space Elevator in place, we can have Solar Power satellites operating within 10 years.");
faq.enterQA("","What about Space Tourism?",
"Space Tourism today is envisioned to include suborbital flights, or maybe $20,000,000 trips to a space hotel that can accomodate a handful of people. \
With the Space Elevator, we'll be able to build space stations that can accomodate hundreds, and then thousands of people. With such infrastructure, going to Space will be as easy and safe as flying to a vacation in resort hotel. Such infrastracture can be in our immediate future.");
faq.enterQA("","What about Space Medicine?",
"In a similar manner to Space Tourism, space medicine only makes sense when Space Habitats can accomodate large amounts of people. The Space Elevator also allows trasportation of people to space without requiring them to be in top physical shape.");
faq.enterQA("","Can you manufacture things in Space?",
"Yes you can, and there are a lot of advantages to processes that happen at zero-G. The key to making these process viable, however, is a reduction in transportation cost down to a few tens of dollars per pound - something only the Space Elevator can do.");
faq.enterQA("","What about a manned mission to Mars?",
"The only reason a manned mission to Mars is considered difficult today is that we are severely limited in the amount of mass we can send. Crossing the ocean in a 20-foot yacht may be difficult and hazardous, but the trip in an ocean liner is easy and safe. With the Space Elevator, we will be able to prepare and stock large Mars habitats well in advance of the arrival of the first humans, and then send them over in what will amount to a large space liner. With the Space Elevator in place, such habitation of Mars can begin within a few years.");
faq.enterQA("","Mining the asteroids?",
"This is considered by many to be the ultimate in Space Faring - the ability to use the mind boggling amounts of material that are out there in the asteroid belt. A single iron asteroid contains more iron than was ever mined, or will ever be mined, on earth. And all of this metal is already outside of the gravity well, so nothing prevents you from building space structures much bigger than, say, aircraft carriers... Such application are not in our immediate future, but the Space elevator removes the one large barrier on the way to making them come true.");
faq.enterQA("","What is Helium-3?",
"Helium 3 is a rare isotop of Helium that enables an easier form of nuclear fusion, which is the holy grail of energy production. The problem with Helium 3 is that all of the oceans of earth only contains a few fractions of an ounce of it - hardly something we can use. \
There are two locations in the Solar System where we can get Helium 3 - the surface of the moon nearby, where we need heavy machinery to process the rock and extract it, and the atmosphere of Jupiter or Saturn, where we can scoop it out. Both of these application lie many years in our future, but definitely require a full industrial base to exist in space.");
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faq.enterSection("politics","The Politics of the Space Elevator","This section deals with the illogical aspects of the Space Elevator.");
faq.enterQA("","Who will built the Space Elevator? Who will control it?",
"We'd like to think that the Space Elevator will be built by an international business group, but we're keenly aware that the Space Elevator has such strategic importance that governments will want control of it. The best case scenario we envision is something similar to a private Space Launch company, which is an independent business entity, but which operates under close scrutiny of the government.");
faq.enterQA("","How many Space Elevators will there be?",
"This is a very good question. Multiple Space Elevators can buy you redundancy, but only if the debris from a broken Space Elevator do not pose a significant threat to other Space Elevators. It is probably wisest to have only a single large Space Elevator (and a spare one in GEO as a safeguard) but from a political standpoint we're likely to end up with multiple Space Elevators, since most major powers will want to have one of their own.");
faq.enterQA("","Why isn't the government building one",
"This is the most important question of all, and is also the reason the Spaceward Foundation and the Elevator:2010 project are here. \
The government today is incapable of undertaking far reaching projects. Congress is driven by pork, NASA by PR, and the whitehouse can't see beyond 4 years. \
This is not a good formula for visionary long-reach programs. Since we're lacking an adversary, the government is not likely to build one without strong public pressure.");
faq.enterQA("","Are the major rocket makers in favor of the Space Elevator or against it?",
"Conspiracy theorist will have it that the Space Elevator will practically eliminate the rocket launch business, and so the Lockheeds and Boeings will never let it happen. \
This idea does not hold water. The markets that will open with the presence of the Space Elevator are ming blowing, and at the end of the day, the aerospace companies are technology companies. \
You could equally argue that they will oppopse jet engines because they will displace piston powered airplanes.");
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faq.enterSection("e2010","Elevator:2010","This section answers questions related to the Elevator:2010 project");
faq.enterQA("","What is the role of the Elevator:2010 project?",
"We sometimes see ourselves as the people advocating airplanes in the times when people thought - we sure, actually - the airships are the right technology for commercial air travel. \
What the airplane people did was come up with a concept call an "airshow", which brought together elements of showmanship and competition to create what was bascially an advocacy tool. \
Messers Allan Loughead (Lockheed), Glenn Martin, Jack Northrop, Leroy Grumman and William Boeing were all spectators at these early airshows.");
faq.enterQA("","Are you really trying to build the Space Elevator by running a student competition?",
"Not directly. The Space Elevator will not get built by using progressingly taller cranes. However, in order for the Space Elevator to be built, the aerospace community as a while has to embrace the concept. \
By running this competition year after year, we engage students, faculty members, private enthusiasts, and aerospace professionals, and so when the tether becomes available, we will have the critical mass of professionals that have been involved with the project and are familiar with the Space Elevator concept.");
faq.enterQA("","Are the competitions happening now?",
"Yes they are! We've held the first competition at NASA's Ames research center in Mountain View, CA in 2005, and the second competition at the X-Prize Cup in Las Cruces, NM. The next competition will be held in the September-October timeframe in 2007.");
faq.enterQA("","Who won in 2005? who won in 2006?",
"Well, as the saying goes, we ALL won. which means nobody won the prize money, but the prize money rolled over to the following year, so we now have $1,000,000 on the line. \
In 2006, we did have some very good performers. The team from Saskatchewan, Canada, came within 2 seconds of claiming the prize money, and several other team peformed very well, notably Kansas City Space Pirates, University of Michigan, Turbo Crawler from Germany, and Lite Won from Campbel, CA. \
In the tether competition, which we consider to be a harder challenge, we're seeing real professional interest, and hope to see a winner in 2007. This will be a very significant milestone on the way to the Space Elevator.");
//--------------------9--------------------
faq.enterSection("advanced","Technical Questions - Advanced","These questions delve a little bit deeper into the design of the Space Elevator.");
faq.enterQA("geoCW","How come the counterweight is not in Geo-Stationary orbit?",
"Because the counterweight is not quite a satellite. A satellite assumes an orbit in which its weight and the centrifugal force exactly balance each other. \
The counter weight, on the other hand, is not balanced. It is superorbital, which means it is moving too fast to stay where it is, and so is constantly trying to pull outwards. \
Luckily, the counterweight is held down by the ribbon, and this is what maintains the tension in the ribbon and keeps the system stable.");
faq.enterQA("geoCM","Is the center of mass of the Space Elevator in Geo-Stationary orbit?",
"Actually, though it may seem intuitive, the CM is not at GEO. See Blaise Gassend's excellent Space Elevator pages for a good discussion of this question.");
faq.enterQA("fallBehind","Won't the ribbon "fall behind" every time you lift a payload?",
"Yes it will. But since the Space Elevator is stable around its vertical position, once it starts falling behind, it wants to return to the vertical.
\
The invisible player that helps the Space Elevator straighten out is Earth. Every time a payload is lifted, the Earth's rotation will slow down by an immeasurable amount!. This contribution is also the reason why a Space Elevator launch requires so little energy.",
"
A rope pushing sideways
",2);
faq.enterQA("ropeSidways","A rope cannot push anything sideways. How does the payload achieve its 8 km/sec orbital speed?",
"This question is related to the last one. As the payload ascend, for exactly the reason mentioned in the question, the payload begins to retard relative to the rotation of the system, and so it pulls the ribbon backwards (Westwards). Once this begins to happen, however, the ribbon has assumed a slight angle, and so is able exert a small component of force in the tangential direction - exactly what is needed to pull the payload in the right direction. Over the entire climb, this pull adds up and accelerates the payload, ever so gently, to orbital speed.");
faq.enterQA("elasticInstability","Won't the ribbon material become unstable because of the stored elastic energy?",
"It's been pointed out (among others, by Dr. Freeman Dyson) that the stored elastic energy in a stretched Carbon Nanotube is comparable (or even higher than) the chemical energy stored in gasoline, and so a snapped filament (so the argument goes) will cause a chain reaction and will annihilate the ribbon. \
While this is a possibility, the stability of the ribbon depends on other factors, chief among them is the Nanotube's ability to disperse thermal energy. A tank of gasoline, for example, does not spontaneously combust even though individual gas molecules are continuously combining with oxygen in an exothermic reaction, since the heat is distributed quickly enough among the surrounding mass.
\
As it turns out, individual CNTs are incredible thermal conductors, so it is likely that failures in the molecular level will not create a chain reaction.
\
Correct construction of the ribbon will compartmentize the strands from each other, also arresting any possible elastic chain reaction.
\
Lastly, as Dr. Dyson was quick to note, this aspect of the Space Elevator can be easily tested and demonstrated in the lab, so will not be an issue for a working Space Elevator.");
faq.enterQA("shortCNT","How do you manufacture a 100,000 km long Nanotube?",
"We don't really have to. When you buy a rope at a store, it is made up of strands that are shorter than the length of the rope, yet the rope is virtually as strong as the individual strands, since the friction between the strands is stronger than their individual breaking strength. In order to make this trick work with Carbon Nanotubes, we only have to make them a few mm in length, a capability which is right around the corner.");
faq.enterQA("","Can you explain the relation between scalability, bootstrapping, and Moore's law?",
"Moore's law is an observation of the computer market that notes that the number of transistors per square inch doubles every year and a half. This dry sounding statement is just another way to say that computers are getting better at an incredible rates. Your computer today is 1000 times "better" than the computer you had 15 years ago. This is unprecedented - can you say that about your car? refrigerator? even about the airplane you flew in last year? \
No other system in the world, and definitely not a transportation system, is improving at a rate comparable to that described by Moore's law. \
The Space Elevator will be the first such system, and it will do so by design - and here's why.
\
The first ingredient is linear scalability. This is a fancy way to say that we can double the capacity of the Space Elevator by doubling its basic components: \
If we use a ribbon that is twice as thick, double the amount of lasers, PV cells, and electric motors, we'll get a Space Elevator system that can carry twice as much mass. This is an unprecedented and extremely powerful property in transportation systems: you cannot make an airplane carry double the payload by doubling the size of its components. \
The second ingredient is bootstrapping. This is a fancy way of saying that we can use the existing capability of the system in order to achieve this doubling. While the first Space Elevator has to be launched by rockets, progressively larger Space Elevator can each be constructed using the exiting Space Elevators, keeping the rate of progress constant - and hence our claim for Moore's law, or truly exponential, growth.");
faq.enterQA("whatsATaper","What's a taper? What's a taper ratio?",
"You may have heard of taper mentioned in relation to the ribbon's thickness. When looking at a vertical tether that is carrying mostly its own weight, it becomes obvious that the bottom sections of the tether don't have to be as thick, since they do not have to carry as much load, and so by making them thinner, the sections above them have to carry less load too!
\
The upshot of this is that if we want to stress the ribbon material in a uniform manner, the ribbon ends up being thickest at GEO, and thinner at its tips.
\
The exact profile is not linear, but we still talk about the ratio between the thickest and thinnest portions of the ribbon - the taper ratio.
\
The taper ratio determines how heavy the ribbon will be, and is a function of the material we use. The stronger and lighter it is, the smaller the necessary taper ratio becomes. With Carbon Nanotubes, the ratio can be as low as 1:2 !");
faq.enterQA("howToBootstrap","How can the Space Elevator increase its own capacity?",
"The hardest problem in making the Space Elevator bigger is thickening up the ribbon - while it is still in service! In order to do that, we need to start with a climber that is carrying a rolled-up stretch of ribbon to space and unroll and add the new stretch to the existing ribbon.
\
This can be done by bonding thin new layers of ribbon on top of the existing ones, or by using mechanical connectors and introducing thicker and thicker segments at the center of the ribbon and removing the older (and thinner) material from the tips of the ribbon.
\
The rest of the system growth is easier. Power beams can simply be aggregated, larger climbers are very simple to build, and the counter weight can be grown by accumulating empty climbers (instead of sending them back down).",
"
Thicker (Blue) ribbon replacing thinner (Red) ribbon
",1);
faq.enterQA("howManySegments","If made out of segments, how many of them will the ribbon have?",
"We want to be able to replace no more than 1% of the ribbon at a time, we want a climber to be able to carry a segment, but we don't want so many segments that the complexity overwhelms the system. \
A good working point is to have 1000 segments, each 100 km long and weighing approximately 1 ton. This way, if we keep the weight of the connectors to 10 kg, we still don't impose more than 1% mass penalty on the system.");
faq.enterQA("howToSegment","What will a segmented ribbon look like?",
"There are several ways to connect segments - they can be bonded, spliced, or connected mechanically. \
Below is an illustration of one possible mechanical connection scheme. To terminate a ribbon segment, it is doubled back unto itself and bonded, to form an eyelet. (This process is performed on earth and the result tested.) The double-thickness portion can be several hundred of feet long, to ensure good adhesion.
\
Two such terminated segments can then be connected in space using simple connectors as shown on the right. Note that the triangular connector allows the addition of a third segment, so a damaged segment can be replaced by a fresh one. This is another reason for having the segments weigh only 1 ton, so the repair climber can be made very light.",
"
");
faq.enterQA("ribbonDegradation","Won't the ribbon material degrade in Space?",
"In space, almost all materials degrade over time, because of the combined effects of vacuum, radiation, temperature changes and micrometeorites. The ribbon is no exception. \
In order to maintain a healthy ribbon, we will keep introducing new material at the center of the ribbon (where it is thickest) and removing it at both tips. \
In order to maintain the ribbon taper, we'll need to keep introducing thicker and thicker ribbon, but this is consistent with our goal of exponentially growing the Space Elevator system. \
If we want to maintain a growth rate comparable to Moore's law (double the capacity every 2 years), and if we're using a taper ratio of 2:1, we'll need to go through a complete replacement every 2 years. We therefore need to design the ribbon material so its expected lifetime in space is 2-3 times that. (4-6 years).
\
As material is pulled in at the anchor, we'll be able to test it and confirm how much it degraded. We will also be able to manufacture the ribbon with extra areas that can be trimmed off during its lifetime and tested for their condition. \
Such practices guarantee that we won't be surprised by a faster-than-expected material degradation rate.");
faq.enterQA("smallestPossible","What's the smallest Space Elevator possible?",
"When we first deploy the Space Elevator, we need to launch it using rockets. We're therefore interested in the minimal viable size Space Elevator that we can then use to bootstrap our way up to a fully operational system.
\
We're currently considering a Space Elevator comprised of 100 tons of ribbon, 50 tons of counterweight, and capable of lifting 2 tons at a time as the minimal viable system. As we go down in size, the thickness of the ribbon becomes too small, and so we need to start decreasing its width as well. This in turn increases its vulnerability to orbital debris. \
In addition, as we get the system down to a reasonable size, and the cost of the rocket launch stops dominating the deployment costs, the motivation to further downscale goes away.");
faq.enterQA("whatLaser","What kind of Laser will power the Space Elevator?",
"In the last several years, operating solid state lasers have gone into the 10 kWatt range, and R&D labs are working on MWatt-class lasers. With tantalizing possibilities such as disk lasers and optical phased arrays (Phasers?!) just around the corner, it seems as if this component will be ready well in time for use by the Space Elevator.");
faq.enterQA("costEstimate","How did you arrive at the $10B price tag? how do you know how much it will cost? No one has ever even built a Space Elevator before!",
"Well, what we did was actually put a higher bound on what it will cost, breaking the down the cost and using rough and conservative estimates for each component:
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- Cost of ribbon manufacturing - even at a very conservative $1000/kg, this will be $1B. \
- Cost of power beaming station - this is a heavily modified telescope and laser. These components have been costed before at under $1B. \
- Cost of building anchor station, payload facilities, mission control - these too are almost standard facilities, costing well under $1B. \
- Cost of first 100 climbers - even at a very conservative $10M each, this is under $1B. \
- Cost of initial launches, first year's operations - 4 large launches, well under $1B. \
- Cost of R&D - the Space Elevator is a very simple system in terms of the actual engineering. $1B includes one orbital technology test. \
- Cost of legal and regulatory work, other non-technical work - $1B. \
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Obviously, these items won't cost $1B each, but we're demonstrating here that the cost of the Space Elevator will not exceed $10B - nor even come close. For comparison, this is 10% of the cost of the International Space Station, or the cost of a single Space Shuttle.");
