Exponential Tether Deployement
The concept of pulling tether up from the ground for the deployment is proposed. The deployment of the initial ribbon from GEO is the same but once the ribbon touches Earth a second ribbon is attached and then a ribbon with a continually increasing cross section is pulled up to GEO. This method has the potential to be much quicker than the baseline method and provide a better quality ribbon in the end - no splicing. The primary issue is that it requires higher strength material.
- Calculations on the basic scenario - already done by Gassend
- Study of safety factor impact
- Study of material strength impact
- Overall system engineering study
- Hardware performance requirements
- Full list of issues.
Blaise, during the deployment phase - prior to climbers ascending this - we may be able to use a ribbon optimized for deployment and only pull up a climber friendly ribbon at the very end. The deployment ribbon for example might have thicker individual threads spaced more widely. These would resist atomic oxygen better. We may also be able to get away with fewer interconnects since this ribbon will only see the environment for a short period of time. These will be a risk trade-off.
The roller/pulley at top will also be an interesting challenge. As you point out, spooling up ribbon at the top will take a lot of energy (Have you run these numbers?). Your second plan to run the ribbon up, over and back down is better from an energy standpoint - and an angular momentum standpoint. Getting it started is a little more tricky though. You need to deploy down a ribbon from GEO then reel it back up and then send the end down. It might be possible to send a smaller ribbon, twice as long and deploy both ends back down then start reeling in and out immediately from the ground. Problem is that this would be a smaller ribbon.