Protecting the Space Elevator: Space Debris

Gabriel V. Cummings- Union Hill High SchoolDepartment of Mechanical and Aerospace

EngineeringRutgers University 98 Brett Road,

Piscataway, NJ 08854August 16, 2006

Introduction

The space elevator faces many obstacles: – 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 • 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 (670-1490km) 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 Impactsper year

Space Elevator Impacts

1 micron 105 Billion 2163

1mm 1,050,000 1 every 50 yrs.

1 m 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

• 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

• 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!