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 August 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 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 210km 2 The 999 space intervals between fibers account for almost 95% of area Area is only 10km 2 without the spaces Very small in comparison to Earth (509,600,000km 2 ) (Surface Area space elevator/Earth) 1/2,500,000 at 210km 2 1/50,000,000 at 10km 2

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 Magnitude calculates the size range of an object H represents magnitude The scale ranges from 3.0 ( km) 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 MeteorEarth Impacts per year Space Elevator Impacts 1 micron105 Billion2163 1mm1,050,0001 every 50 yrs. 1 m401 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 microns in diameter To strengthen the overall design, two cross section fibers of microns These would run every 100 meters From km, 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 Baalke, Ron. "Arecibo and Micrometeors." 28 May July "Bond Albedo, Near Earth Asteroids, Radar Astronomy." Wikipedia. 15 Aug Aug Briley, Mike. "Micrometeorites." University of Wisconsin. July Edwards, Bradley C., and Eric A. Westling. The Space Elevator: a Revolutionary Earth-to-Space Transportation System. New York, Nelson, Stephen A. "Meteorites, Impacts, and Mass Extinction." 20 Apr Tulane University. July Yeomans, Don. "Absolute Magnitude (H)." NASA. Aug NASA. July Yeomans, Don. "NEA Discovery Statistics." NASA. Aug July 2006.

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!