SpaceElevatorEnvironment

Title: Environment
[Cover Img]	About: Moderator: Brad Edwards Created: July 6, 2008 Modified: July 25, 2008	Tags: This is a collaborative article Discipline(s): Wiki, Engineering

 

The Environment

The elevator stretches from the Earth to high orbit - passing through Earth weather, the ionosphere, radiation belts and out beyond the Earth's magnetosphere. In each of these environments there are concerns and hazards for the space elevator and a complete understanding is required to be able to produce a viable design.

Hazard	Impact	Details / Solutions
Lightning	Severed ribbon	Solution: Anchor location in lightning-free zone
Wind	dynamic destruction of the ribbon	Solution: Anchor location where limited wind, ribbon design
Radiation 1	ribbon degradation	Solution: Select CNTs and other materials for ribbon that are radiation resistant
Radiation 2	hazard to electronics and cargo	Solution: May be able to ascend at a higher speed and use shielding (passive and active) to get radiation to acceptable levels
Debris	ribbon destruction	Solution: Ribbon design with a width larger than a meter insures only a small part of the ribbon will be damaged by any impact. The ribbon design also isolates damage along the length of the ribbon. Active avoidance limits impacts larger than 1 cm.
Meteors	ribbon destruction	Same as for debris though lower flux and active avoidance can not be used.
Earth's magnetic field	Current generation in ribbon	Ribbon is geosynchronous so only flucuations in the magnet field will create any current and this is small
Interplanetary magnet field	Current generation	The ribbon travels quickly through the interplanetary magnetic field but the field is too weak to generate and substantial current.
Solar wind/particles	ribbon degradation	same as radiation above
Gravitational influence	ribbon oscillation	The Moon and sun will both exert a gravitational pull on the ribbon at a roughly 24 hour period. The natural frequency of the ribbon is about 7.2 hours and there will be little coupling
Thermal cycling	ribbon wear and oscillation	Each day the lower end of the ribbon will go in and out of the Earth's shadow. This will change the temperature and length of the ribbon
Atomic oxygen	ribbon destruction	Solution: Coating the affected section of the ribbon with an oxygen resistant material

Major Work Items Required

• Experimental tests of ribbon in atomic oxygen
• Radiation protection for humans in transit
• Detailed modeling of ribbon degradation lifetime

Additional Work Needed

Item	Notes	Completed and Ongoing Efforts
Full characterization of environmental effects	The environment will play a big role in the performance of the space elevator. Each of the items above has the potential to take down the space elevator if we do not design the system correctly. The starting point is to know as much as possible about everything that can threaten the elevator. This is a big task. What we need is people to sign-up to take each of the environmental effects above, start with what has been done and and expand it. COllect all relevant information and form a consistent picture of the environmental component and how it threatens the elevator. The next stage is to for a plan to mitigate the problem. All of the environmental factors have been discussed but some such as the orbital debris are changing and others we need more detailed work such as information on metal coating the ribbon initially and in place. Some of the items above are pretty straightforward and others are nasty little buggers. Have fun.	The Space Elevator by Edwards, Westling
Detailed model of damage extent and flux due to meteors	This is similar to the orbital debris problem but covers natural meteors that can't be tracked and can come in any size and flux. First we need more information on the flux of meteors in the vicinity of Earth, the period, flux and particle size. Then we need to determine if any of the known meteor showers is a serious threat	File:The Leonids and the SE.odt by Edwards
Thermal modeling of the ribbon during transition between sun and shadow	The elevator is a unique system in terms of the day and night aspects. Some parts of the ribbon see day and night (the bottom) others will rarely ever see even a fleeting night (the top) and then the middle of the ribbon will see fast sunrises and sunsets many with odd length nights. The question is what happens when the shadow races up or down the ribbon. How much will it expand and how will it affect the ribbon? The thermal expansion is expected to make the ribbon grow by a few kilometers over tens hours and we will need to how how to deal with it. First we need information, then some calculations and then a full FEA analysis.	None at this time

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