SpaceElevatorDeployment

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Title: Space Elevator Deployment

[Cover Img]

About:

  • Moderator: Brad Edwards
  • Created: July 6, 2008
  • Modified: July 26, 2008

Tags:

  • This is a collaborative article
  • Discipline(s): Wiki, Engineering

Contents

The Deployment

Deploying the ribbon takes innovation and care. The ribbon can not be simply thrown up into space neither can it be blindly dropped down from orbit. The deployment spacecraft is to deliver the first ribbon then climbers will build up and strengthen the ribbon to the point where it is usable.


Dimension
Spacecraft Mass 80 tons Launched in sections to LEO, combined then moved to GEO. Roughly half of the launched mass is ribbon, 1/3 spacecraft and remainder fuel.
Mass of first ribbon 40 tons Launched in two separate spools, ribbon is full length but a total of 20 cm wide
Spacecraft propulsion MPD Electromagentic with very high ISP File:AdvancedPropMod.ods
Power source MW of beamed power Power for MPD is beamed up from the ground using the same power systems as planned for the climbers but located at distributed points around the equator
Deployment time for first ribbon 2 weeks This is determined by the maximum speed of the spools and rollers on the spacecraft. The deployment and expansion must be done quickly to minimize possible impacts and degradation
First climber size 1 ton
Number of construction climbers 280 Climbers grow in size as the ribbon grows and can support more
Construction time 2.5 years This is for the first stable elevator with 20 ton maximum mass climbers. A system capable of carrying a 100 ton climber would take an additional year to construct.
DeploySC.jpg


The working climber design is File:Deployment Spacecraft.dxf. Notes on the design are located File:DeploySpacecraftnotes.odt here.

Alternative Designs

  1. Exponential Tether Deployment by Blaise Gassend:[[1]] Work Space to Develop the Exponential Tether Deployment

Status

Large Spacecraft have been built and operated Need additional work on launching first ribbonInclude images and videos Include design write-ups

The deployment spacecraft should be largely built with conventional satellite technology.

Major Work Items


Additional Work Needed

Item Notes Completed and Ongoing Efforts
Overall system engineering We are now in the age of space engineering but still on a learning curve. The deployment spacecraft is simple in some respects and complex in others. It largely has one task in Earth orbit - deploy the first ribbon. However, there is a lot of complexity to this task and we need it defined. There is lots on satellite hardware out there and David Lang has done dynamics modeling of the ribbon deployment with various factors. We need someone to sit down and really examine the overall design of the spacecraft.
Categorize available electromagnetic propulsion systems of the size required The Magnetohydrodynamic propulsion system has been baselined and systems near what is needed have been built (Russian and Princeton). This may not be the only viable system and we would like to have an understanding of the options. What we need is to fully define the potential systems including performance, mass, maturity, cost, etc. and how it may function in the overall system.
Examine large scale ribbon spooling techniques This will be a large spool of ribbon we launch - 20 tons. It is likely not the largest textile spool ever made but probably close. The question is what kinds of stresses are found in this spool and what issues do we have in launching it? What is the best technique for spooling and unspooling a ribbon? Is it possible that we will need to split the ribbon into smaller spools say 4 tons each? These are the types of questions that we need to address.
Ribbon deployment The deployment spacecraft heads up to GEO and begins deploying the first ribbon. David Lang has created dynamics simulations of the ribbon deployment that are pretty complete. Thes simulations need to be combined with the reality of teh system. The ribbon needs to be deployed within a specific speed range and this will change during the course of deployment. A certain amount of ribbon needs to be thrown out from the climber before it will be stable, initial calcualtions have this length around a kilometer but these need to be done in detail. If multiple ribbons are deployed what are the issues with joining them? The whole ribbon deployment is critical and we need a detailed picture of what we will be dealing with.
Overall structure design Just like the climber structure effort, this one is pretty open. We need to deal with the ribbon deployment and that will give us an artificial gravity effect. We will possibly need more than one array for receiving power from Earth (yes, we are talking about power beaming to the deployment spacecraft). The structure is primarily designed to carry the massive spools into orbit, the fuel and do this with minimal mass.
Retrieving the end of the ribbon at Earth Imagine a ball on a string being lowered from the sky - that is the end of the first ribbon coming in. It may come in at 50 mph, it may be electrically charged, we will likely have flashing lights and a radar beacon on it as well as floats because it will probably be dropped into the Pacific Ocean. This end needs to be picked up and taken to a waiting anchor station where it can be attached. It could pull back up, it could whip in the wind, it could continue to come down and lay kilometers of ribbon in the ocean before it begins to lift back up. We need someone to think through scenarios and lay out how they can be dealt with.
Operations We need a complete plan for the deployment from launch through satellite shutdown as a dead weight at the end of the first space elevator. This is to include a time schedule based on what is already known and work in the above tasks. When does the MPD fire and how long for optimal energy efficiency? At what orbit is the spacecraft first placed - GEO or above GEO? when does the ribbon deploy and how fast in relation to the orbit change and MPD firing? How do operations change when the end touches down at Earth?

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