Frequently Asked Questions
Please note that a number of issues are addressed in the Phase I NIAC paper,
available in HTML format
- What about conservation of angular momentum?
When an elevator ascends the ribbon, it must be accelerated eastward because
the Earth's rotation represents a larger eastward velocity the higher you go. The required
eastward force on the ascending elevator would have to be provided by a corresponding westward
force on the ribbon.
If you go through the math quantitatively, the angular momentum for the climbers requires a pound
or so of force over the one-week travel time, and we do that easily with our many tons of material in
the anchor and the counterweight.
The quantities really are tiny, but just to be complete, a climber going up pushes the entire elevator
slightly to the east, causing it to lean. However, the ribbon recovers for the same reason that
it stays up in the first place. Centripetal acceleration is acting on the upper two-thirds pulling
it outward, and the lost angular momentum is replaced very quickly (essentially as fast as it is lost).
The ribbon will never loose enough angular momentum to even deflect a single degree let alone fall.
The extra angular momentum is stolen from the Earth's rotation; we will have to worry about this effect
slowing down the Earth and making the day longer if we ever decide to ship Australia into space.
- What if it breaks?
- How easy would it be to break?
The planned position of the elevator avoids hurricanes, lightning and other
extreme weather. The ribbon is engineered to be twice as strong as it needs to
be to support itself and any planned cargo attached to it.
- What if it falls?
The majority, the long end out in
space, gains enough speed that it burns up in the atmosphere, with the lower
portion falling into the sea. It will not fall on top of anyone.
- For the portion that doesn't burn up in a fall- what effect will it have on the environment?
Honestly, it will make a little
bit of a mess. But New York City tickertape parades have made bigger messes.
Comparatively it will put much less dust, dirt, debris and chemicals into the
environment than wildfires of the American west, any one of the large expendable
rockets, or a month of natural meteors hitting Earth. The ribbon is light (7.5
kg/km) so, any pieces that fall to earth will slow down, in the air, to about
the same terminal velocity as that of an open newspaper page falling. It will
not have enough momentum to cause mechanical damage when it comes down. We have
considered other health risks such as inhalation of very small fragments and
believe this will not be a problem but we are conducting studies to make sure
this isn't a problem. Since we are aware of the possible problems now we can
design the elevator to avoid these problems.
- How large a wave/disturbance would it generate?
The wave/disturbance would be nonexistent. As above, there just
isnít enough mass, even in later, larger, ribbons, to generate such energy
dispersion. There might be a small amount of light as a line in the sky as the
ribbon burns up but after that it will be a few pieces of black film fluttering
to Earth. Because of the size, distribution and winds, it is conceivable that
only a few people would even see the event in any way and just as few would find
actual pieces of the ribbon.
- How much warning would there be from the time of a break
and the time it would take for the lower portion to splash down?
Depending on exactly what happened it could be a
few hours to weeks.
- What would happen to the surviving portion?
The ribbon that fell to Earth could be recovered for
study but because of the amount and distribution it would be difficult to find
many pieces. The pieces that do land would eventually degrade but not for a very
long time. Keep in mind that this is mostly a stable form of carbon; it doesnít
do anything. The debris would resemble long hair and would probably be broken up
in interactions with animals, plants, wind, fish and waves. In fiber form it
would be much too large to inhale and would probably work its way through a
digestive system unaffected. The only debris we have any concern about is if it
were reduced to nanotube size. This we don't understand yet so we will study
this to see if there is a problem and then probably also design the ribbon to
remain in larger pieces if it re-enters.
- What would happen to anything climbing the ribbon at the time it broke?
The short answer is that some payloads will fall (below the break and below 24,000
km altitude), some will enter low orbit (below the break and between 24,000km
and GEO) and some will be tossed to high Earth
orbit (above GEO) depending on
where the payloads are and where the break is. However, what happens also
depends on the reaction of the payload. In other words, what happens depends on
lots of factors. Escape pods or re-entry vehicles may be required depending on
- Will high winds pose a problem?
that the proposed ribbon (of 1cm width below 10km altitude) would break at 71.5
m/s (159 mph) or a Category 5 hurricane. The proposed location of the ribbon is
not in a hurricane or high wind area.
- What if lightning strikes the ribbon?
The best way to deal with lightning
is to avoid it hence the proposed location of the ribbon is in an area that
receives little to no lightning.
- Won't the ribbon "short out" the atmosphere?
There is a voltage difference of several hundred
kilovolts between the Earth's surface and the ionosphere. The (presumably conducting) ribbon
would at least provide a path to reduce the global potential and might even short it out,
forcing the ribbon to carry a large current. Would this effect the construction of the highway?
How might a shorting out of the global circuit effect the Earth's meteorology?
It is correct that there are substantial electrical potential in Earth's atmosphere.
However, doing a quantitative analysis of the situation, we found the currents that will flow
through the ribbon will be minimal due to the resistance of the ribbon, cross-sectional area
of the ribbon, the distance the potentials are separated by, and the poor coupling between the
ionosphere and the ribbon. The total effect of the ribbon on the potentials can be seen in
conventional tethered balloons or kites.
- Will the ribbon produce an electrical current?
The last space shuttle-tether experiment, which unspooled about 12 miles
of cable, generated thousands of volts of electrical potential and kilowatts of power, burned
through the insulation of the cable, and generated a tremendous explosive arc of electricity,
that snapped the tether. Now imagine a 60,000-mile-long cable and its electrical-generating
capacity and you begin to see the disastrous potential.
There are several aspects to this question. An electrical might be
produced in several ways: 1) due to the electrical properties of Earth's
atmosphere, 2) collection of the space plasma and 3) due to the movement
of the ribbon relative to the natural magnetic fields near Earth.
1): Earth's atmosphere consists of voltage differentials and charge
build-up in association with storm activity, in the ionosphere and even on
a clear blue-sky day. The last is easiest, the voltage potential set up
there can be many volts but is over a large distance and based on the
resistance of the ribbon would produce little current or difficulty.
Storms produce high voltage differences, enough to produce lightning which
can damage the ribbon. We have selected an anchor location in an area
that has essentially no lightning and very little storm activity. With
our mobile anchor we will be able to avoid the rare storm. In the upper
atmosphere there can also be charge and voltage potential build up. In
the upper atmosphere (ionosphere) the density of plasma is low and there
will be poor coupling between the plamsa and our ribbon. We will have
some charge build up and small current flow but it will be comparable to a
small household battery. One area we need to investigate further is
sprites or breakdown events in the extreme upper atmosphere.
2) In space there are plasmas that can deposit charge on satellites and
our ribbon. As above, the density of this plasma is very low and a small
amount of charge will be collected on our ribbon. We also expect both
positive and negative charge to be deposited on the ribbon which would
reduce teh net charge build-up. If one charge preferentially builds up
this will raise the potential of the ribbon, pushing away more of this
charge and attracting the opposite charge which will limit the net voltage
build-up. The total charge and voltage we expect and the length and
resistance of the ribbon again make the currents much smaller than what
you could get from common small batteries.
3) The third place where currents can be produced is when a wire is
dragged through a magnetic field. This is how commercial electric
generators work. To produce electricity you need a strong magnetic field
and a high velocity. This has been demonstrated on orbital tethers
traveling at 11,000mph through Earth's magnetic field, high voltages have
been produced (1000's of volts). (3a) In our case our ribbon is
essentially stationary relative to Earth's magnetic field so again very
little current will be produced. (3b) The upper end of the ribbon will be
in space and be moving relative to the interplanetary magnetic field but
since this magnetic field is very weak little current is produced here as
If you add up all f these currents and voltages you end up with nothing
that will be problematic with the exception of the lightning. So as long
as we avoid lightning and the storms associated with it we will get very
little current flow or trouble from this area. You can think of most of
this in terms of a conventional TV tower. Related to most of the topics
discussed above (1 and 3a) we will experience the same voltages and
millions times less (due to the relative sizes) current as a TV tower.
Several colleagues had hoped that we might produce electric power from the
ribbon but from what we have found power generation from the ribbon will
take a lot of work and design modifications to produce much of anything.
-Dr. Brad Edwards
- Will an oscillation bring the ribbon down?
There will be a 7 hour natural
frequency which can be actively damped with the anchor station.
- Will radiation degrade the components?
The carbon fiber composites are good for 1,000 years in orbit.
- Will the ribbon effect bird/other species migration?
Unlikely due to the small size and passive
nature of the system.
- What about things hitting the ribbon?
- Will the large amount of orbital debris
be a problem?
Low Earth objects can and will pose a serious
problem. However active avoidance can be used to avoid objects that would cause
damage. On average, an object would have to be avoided every 14 hours.
- Don't all existing satellites cross the Equator, where they could hit the ribbon?
Each and every satellite in Earth orbit (except for those in an exact
geostationary orbit) crosses the equator twice during each and every orbit.
Unless that elevator is really good at dodging, one of these satellites is going to run into it.
We are good at dodging, and we will avoid the satellites. We are tracking them and will
have days to weeks warning. We will move the anchor about a kilometer each day to avoid the debris.
- Is the ribbon in the path
of any existing launch programs?
- Is it
in any existing flight paths?
One of the nice things about our anchor
site is that it is in the middle of nowhere, approximately 400 miles from
shipping or plane routes.
- The Leonids and the Space Elevator
The Leonids are a trail of dust and debris left by the Tempel-Tuttle comet as
it traverses our solar system each 33 years. The last passage was in 1998 and the next is
expected in 2031. The dust and debris left by the comet passage disperses and leaves the
neighborhood of Earth on a timescale of years though some debris always remains. The flux
density of the debris can fluctuate by 10,000 from year to year. The Leonid debris also has
a distribution of debris that includes dust particles and objects up to 10 cm in diameter.
An article published by McNeil, Lai and Murad, Charge Production due to Leonid Meteor Shower
Impact on Spacecraft Surfaces, discusses the impact probability on spacecraft and the details
of the Leonid debris. The flux density from McNeil is shown in figure 1. This flux density
is for a Leonid shower with a peak visual flux of 1000 meteors per hour. The standard peak
is 10 to 20 and the largest in 1966 was 160,000. We can calculate the probability of impact
on the elevator ribbon based on the 1000 peak number and then scale from there.
Objects larger than about 10 cm have a finite possibility of destroying the ribbon. Objects
as large as 5 cm in diameter has a small chance of destroying the ribbon. If we consider a
weighted probability function we might approximate the likelihood of destruction with the
likelihood of impact by a 10 cm or larger object. In our baseline, with densities of 3 gm/cm3
(estimate for the Leonid debris), this relates roughly to a mass of about 1500 gm
(4/3*3.141*5^3*3) or a flux density of 10-17/m2 s. A typical Leonid shower lasts roughly 2 hours
or 7200 s and the total area of the proposed elevator ribbon is 108m2. This gives
us a probability of damage leading to destruction for each annual passage through the Leonid
debris of roughly 1/100,000 for the showers with peak visual rates of 1000/hour. For a more
standard shower the probability would be 50 to 100 times less. For the largest likely event
(possibly in 2031) the probability would go up by 160 to a 1/625 possibility of severe damage.
These are rough estimates and more accurate calculations are required. However, these estimates
indicate that until 2031 the danger is probably minimal. By 2031, modifications and mitigation
techniques could be implemented to improve survivability.
-Dr. Brad Edwards
- What about alternatives?
- Business, Economics, and Politics
- Construction Cost Estimates
How we are going to pay for the elevator
- How will the elevator be funded?
The elevator can be
funded privately, publicly, or with a combination of the two.
- Don't projects of this scope tend to run
As a matter of fact, no, they donít. (The construction
industry would be in perpetual bankruptcy if that were true.) While there is
precedent for space projects running over-budget, we are working to be as honest
as possible with our costing and place contingency costing on items that are
uncertain. As we continue our development we will have a much better handle on
the costs and the budget will change accordingly. The current budget may not
match the end result but once engineering studies are done there is no good
reason why the final budget should not be a firm and realistic one. The other
thing to remember is that cost overruns are often the result of poor planning or
greed. We will do our best to avoid both.
- Why it makes sense to build it, and how it will be used, commercially.
- How will the space elevator make money?
We will earn revenues by transporting goods (and eventually, after thorough
testing, and inevitable future regulation, people) to various departure
points. Because there are so many different uses for the destinations
available - all earth orbits, all la Grange points, the Moon, Mars, Venus,
and the asteroid belts - we feel that the best thing we can do is to let
capitalism determine the uses and markets. Our job will be to transport
mass cargo to those destinations.
We envision certain uses right away: One of my personal favorites is the
Solar Energy Satellites stations, that collect the endless energy of the
sun, and beam it back down to earth. Another one is going to be certain
kinds of Manufacturing - specialty pharmaceuticals and crystal formation
for electronics. The telecommunications industry will expand to a level we
cannot imagine, because of cheap access to space. And that is just the
Use your imagination, if it could be done in space, we will help get it
there. Universities could have their own space program, private companies,
developing nations, even individual people will have the kind of access
that many of us have only been dreaming about.
We will charge by the pound, per load. There will be volume discounts for
larger clients and discounts based on frequency of transit, and early
discounts for clients that jump-start sales. Please call us for pricing -
now - to lock in your price/pound rate and secure your place with a small
deposit. (360 377-0623)
- What will the elevator be used for?
The elevator will be used for launching satellites into all Earth
orbits, spacecraft to other planets, construction of solar power satellites, and
space stations. In the long term our children may even take rides up the
elevator to space.
- Will the number of trips restrict its usefulness?
The shuttle program does less than 10 launches a
year and only to low-Earth orbit, the elevator would be able to launch 5 tons
every day to any orbit or 13 ton payloads every three days. This launch
capability is over forty times the current U.S. launch capability with just the
first cable. We can replicate cables if we choose to multiply our capability.
The elevator will greatly increase our capacity and be much more useful than any
other system out there.
- Environmental Issues
- Would the elevator be susceptible to a terrorist attack?
Yes- so is practically everything. An
attack on the ribbon is unlikely because of the anchor station's isolation and
the relatively small amount of casualties that would result. Its main protection
is being so hard to get to, there is no way to sneak up on it. However if
everyone has equal access to the benefits of the space elevator, there is
substantially less risk.
The anchor is located in the equatorial Pacific 400 miles from any air or shipping lanes.
The ribbon would also have restricted airspace around it. The ribbon and anchor would be
protected like any other valuable piece of property, in this case probably by the U.S. military.
- Carbon Nanotubes - What they are, and how they will be used, commercially
- Products and Services that we will work with, as a means of building awareness for the project, and earning revenues during the 15 year construction process.
- What will the elevator be used for?
As many uses as
existing launch methods currently allow, with many new abilities. Initially, the
space elevator will transport various cargos to orbit, with human transport
coming later. The increased capacity of the elevator will enable much larger
structures to be brought to space than have been previously possible.
- When can I ride it?
Riding the elevator up to a hotel in
the sky is still a ways off. Initially the elevator will just haul cargo; an
additional, stronger ribbon would have to be built for human transport to become
- Anchor Station
How's and Why's of the Anchor Station
- Climbers (Construction and Cargo)
How's and Why's of the Climbers
How's and Why's of the Ribbon
- Evaluation of Ribbon Wear and Tear
- Power Beaming
How's and Why's of the Power beaming system
- Counterweight / Robotic-Human Assembly
How's and Why's of the Counterweight / Robotic-Human Assembly
- Deployment Spacecraft and Deployment Scenario
How's and Why's of the Deployment system
- MPD Propulsion System Definition
- Orbital Debris Issues, Meteors, and Tracking
What is and how to deal with orbital debris and meteors
- Health Issue Research
- Carbon Nanotubes (CNT)
- CNT Composite Research
- Solar Energy Satellite System
Updated: RGM 12/5/2002 5:20:28 PM