Protecting the Space Elevator: Space
Debris
Gabriel V. Cummings- Union Hill High School
Department of Mechanical and Aerospace Engineering
Rutgers University 98 Brett Road, Piscataway, NJ 08854
August 16, 2006
Introduction
The space elevator faces many
obstacles:
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Lightning strikes
Atomic oxygen
Induced oscillations
Strong winds
Meteor impacts
Most severe problem: Meteor strikes
– Could destroy single or multiple
Carbon nanotube fibers
– Many larger than the 10-40 micron
diameter of each fiber
– Complete elevator failure
– Loss of billions of research money
Presentation Objective
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Discuss the threat of meteors hitting space elevator
Talk about impact probability and surface area
Propose various meteor detection systems
Present ideal design for ribbon
Discuss solutions for protecting the structure
Surface Area
• The space elevator’s total surface area is about
210km2
• The 999 space intervals between fibers account
for almost 95% of area
• Area is only 10km2 without the spaces
• Very small in comparison to Earth
(509,600,000km2)
• (Surface Area space elevator/Earth)
• 1/2,500,000 at 210km2
• 1/50,000,000 at 10km2
Meteors and Mircometeors
– Nearly 300 Million meteors hit earth everyday
– About 105 Billion meteors strike Earth each year
– Almost 40 meteors a meter or larger enter the atmosphere
a year
– Larger sizes are far less frequent but are more dangerous
– They are easier to detect because of size
– Nearly all meteors that impact the Earth are of a
microscopic size
– 1 micro gram in weight
– The fastest micrometeors have as much energy in
them as a 22 caliber bullet
– Very hard to detect, because of their microscopic
size and high velocity
– If they come at an angle, it could destroy more than
one fiber
Artificial Satellites
• About 2,500 working and nonfunctioning
satellites orbit the planet
• In total, there are over 8,000 pieces of
artificial debris
• They are bound to strike the space
elevator because of their orbits
• Tracking them is important
• Base of elevator should have ability to
move in order to avoid a collision
Radar
• Powerful radars could detect objects as small as
1cm or less
• Until recently, radar only picked up meteors as
noise
• The Arecibo observatory uses a 430 megahertz
detection system to record micro meteorites as a
velocity
• It is one of the only systems currently available
with the ability to track micro meteors
• Could detect objects of nearly every size
Satellites
• Satellites can be used to monitor space
for any debris coming towards the
elevator
• Provide a rough estimate on their distance
and amount of time before an impact
• Better then earth based telescopes since
their observations are not distorted by
the atmosphere
• Increasing the number of observational
satellites is a must for safeguarding the
elevator
Albedo’s and Magnitude
• Albedo is the ratio of the light
reflected by an object over the
amount of light that is absorbed by
it
• it is measured from 0-1, zero is
very dull and one is very bright
• Comet’s are about 0.6 and
asteroids are near 0.05-0.25
• Magnitude calculates the size range
of an object
• H represents magnitude
• The scale ranges from 3.0 (6701490km) to 30 (3-6m)
• When Albedo's and Magnitude are
combined to give an approximation
of a projectiles size
Detection Programs
• Many programs exist to search for
Near Earth Objects
• NASA’s Near and MIT’s LINEAR
programs are used to protect the
Earth from these deadly asteroids
• Currently, they are used to find NEO’s
larger then 1km
• In order to benefit the space elevator
as well, the search range would have
to be decreased
• More geared for larger objects
Impact Probability
Size of Meteor
Earth Impacts
Space Elevator Impacts
per year
1 micron
105 Billion
2163
1mm
1,050,000
1 every 50 yrs.
1m
40
1 every 62,500 yrs.
Space Elevator Headquarters
• Bases would analyze
accumulating detection data
• It would come from NASA,
radars, satellites, and other
programs
• Determines the severity of an
impact
• Proposes appropriate action
• Control center at the foot of the
space elevator
Ribbon Design
• Ribbon is about a meter by
100,000km
• Made up of 1000’s of Carbon
nanotube fibers 10-40 microns in
diameter
• To strengthen the overall design,
two cross section fibers of 10-20
microns
• These would run every 100 meters
• From 500-1700km, double the width
of the fibers, since this is the range
where most meteors are located
• This would allow the ribbon to
handle more strikes
• Also increases the critical size of a
meteor hitting the space elevator
Armed Satellites
• Each of them is responsible for a certain
area around the elevator
• Armed with lasers
• Would destroy oncoming meteors before they
become a hazard
• Never to be pointed towards the elevator or
the Earth
• Only act under the control of the space lift’s
command center
Heat Energy Field
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It’s a very futuristic technology, possibly taking years to develop
It would surround the entire structure, using a solar power energy source
This is possible since Carbon nanotubes are good conductors of heat
This energy would disintegrate any micro meteors before they get close to the
space elevator
• Similar to the meteors burning up in the Mesosphere
Conclusion
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I discussed the threat space debris had on the space elevator
adequate detection and protection systems
Impact Probability
Surface Area ratios
And lastly, the idea that the space elevator is a realistic goal for the
future
Works Cited
• Works Cited
• Baalke, Ron. "Arecibo and Micrometeors." 28 May 1997. July 2006
<www.meteorobs.org/maillist/msg04686,html>.
• "Bond Albedo, Near Earth Asteroids, Radar Astronomy." Wikipedia. 15 Aug. 2006.
15 Aug. 2006 <www.wikipedia.org>.
• Briley, Mike. "Micrometeorites." University of Wisconsin. July 2006
<www.astro.wsu.edu/wortney/astro/html/meteor.html>.
• Edwards, Bradley C., and Eric A. Westling. The Space Elevator: a Revolutionary
Earth-to-Space Transportation System. New York, 2002.
• Nelson, Stephen A. "Meteorites, Impacts, and Mass Extinction." 20 Apr. 2006.
Tulane University. July 2006 <www.tulane.edu>.
• Yeomans, Don. "Absolute Magnitude (H)." NASA. Aug. 2006. NASA. July 2006
<www.neo.jpl.nasa.gov/glossary/h.html>.
• Yeomans, Don. "NEA Discovery Statistics." NASA. Aug. 2006. July 2006
<www.neo.jpl.nasa.gov/stats>.
Acknowledgements
• First and foremost, I would like to thank Professor Haym Benaroya for allowing
me to conduct my research with him, and for showing me the importance of the
space elevator
• Yuriy Gulik, for all of his help with the computer technology for my project
• Dan, Josh, Sergey, and Adaleena for keeping me entertained while I was
conducting my research
• And to everyone else who helped make this presentation possible, Thank You!