A picture of Blaise Gassend
Notes from the Third Annual Space Elevator Conference

Slashdot

To my great surprise, this page got slashdotted. It was neet to bump into people I know and have them tell me they saw me on slashdot.

If I had known that so many people would see this page, I would have at least read the notes over before posting them. In response to the slashdotting, a number of people pointed out fixes that I have incorporated below. I would like to thank Jim Van Zandt and Monte Davis, who probably spent more time reading the notes and correcting than I spent writing them.

I integrated the comments with as little effort as possible. Jim sent a diff file, so I just diffed (and checked that the changes were apropriate). Monte sent comments per speaker, so I just added "Monte Davis adds" lines everywhere.

Related Links

The slides from the conference have been posted by ISR. And my papers can be found here.

Introduction

Here are my notes from the Third Annual Space Elevator Conference. It was quite a fun conference to attend. It was interesting to see how more and more independent people are starting to seriously look at aspects of the space elevator. Ben Shelef is looking at deployment scenarios, and chatting with him, I found that we have been doing a lot of thinking along common lines. Larry Bartosek has been doing some really interesting work on designing the drive elements of a climber. Lots of other interesting things are going on of course, see below.

As usual, the big hurdle is the materials for the space elevator. So far no breakthrough, I think we are still at 3.5 GPa. Individual nanotubes have been better characterized, and strengths of 150 to 200 GPa are typical, now we just (big just, I'll admit) need to figure out how to make a good composite out of them. So far, it appears that very small imperfections in a fiber will cause failure. Quality control on the ribbon material is going to be a key issue. Ben Shelef and I both suggested methods by which we could avoid splicing the ribbon in space.

Some other issues caught my mind. The number of impacts by 10 to 100 micron particles is a few impacts per year and per square meter of ribbon. This number isn't new, but it came up a couple of time during the conference. It underlines how important transferring the load between broken fibers is. Another interesting issue is how twisting motion in the ribbon can cause the ribbon's temperature to vary between 100 and 300 K in a matter of seconds depending on the angle of incidence of the Sun on the ribbon. This could have some annoying dynamic and fatigue issues. Finally, I am still eager to find out if the interconnects will be able to handle the large amount energy that is dissipated when a fiber snaps.

I'm not so interested in the political and economic side of things, but there were plenty of talks along these lines. Not much evolution since last year, though. For now, ISR has a couple of million dollars promised to it, but they are still trying to get it from Marshall Flight Center. That may explain why the space elevator doesn't currently have a prominent place on the ISR website, and why things have been moving slowly since the previous conference.

Day 0: Sunday June 27th 2004

Nice slow first conference day. The registration desk opened at 5pm, and by 6pm twenty to thirty people were assembled for an informal ice breaker. I enjoyed the opportunity to see a lot of faces that were in Santa-Fe, and I was happy to be recognized by most of the ISR and Los Alamos folks. I also bumped into Ben Shelef, who seems to be doing a lot of interesting analysis in his free time. We discovered that we have been doing a lot of thinking in similar directions, and both of us have been frustrated at not having anybody to bounce ideas off. This might be the start of an interesting collaboration...

Day 1: Monday June 28th 2004

I picked up a copy of the Space Elevator Challenge 2010, an X-Prize like challenge to help in space development. The goal is to have a 250 kg climber climb a 16 km tether.

Introductory comments by Brad Edwards and Bryan Laubscher

Brad mostly talked about conference organization issues.

Brian started by explaining why we need to start thinking about design and engineering of an SE as soon as possible: so that we can start building as soon as the SE becomes technically feasible.

SE very much like the transcontinental railroad. Construction of transcontinental railroad started as soon as the necessary surveying had been completed. A number of differences though. The railroad was not completely unproven technologically and economically. With the SE, we can do small scale demonstrations, but the full scale implementation is fundamentally different from any small scale testing. Like the railroad, the SE would be a paradigm shift in transportation. It would reduce costs, increase launch rate and reduce risk.

At LANL, Brian's hierarchy is behind him and he has been given money to write grants. Next conference with a SE flavor is the Space Exploration conference in New Mexico, in April 2005.

Keynote speaker, John Mankins

Projector died. Talk went on without it.

Monte Davis adds: "Orchard" metaphor for NASA today: planting, culling and pruning (through "spiral development" process) -- keep our eyes on the fruit, not on maximizing the number or size of trees

Projector came back up.

Lots of budget talk that I would do a horrible job of writing up.

Rodney Andrews, Carbon Nanotube Polymer Composites: A Review

Monte Davis adds: alignment of fibers should be within 5% -- beyond that, stress generates new defects. Conductivity *does* go up with strength in "traditional" carbon fiber, but may be uncorrelated or even inversely correlated in CNTs.

Nicole West, Material Analysis of the Space Elevator Ribbon at Selected Altitudes.

Monte Davis adds: atomic oxygen concentration peaks at 80-120 km

Ian Kinloch, A Direct Process for Spinning Fibers from carbon nanotubes

Monte Davis adds: we get large variations in spun-fiber diameter, length and mechanical properties -- but old hands in the business tell us that's quite typical for experimental fiber

Bryan Laubscher, Space Solar Power for Powering a Space Elevator

Harold Bennett, Powering the Space Elevator Using a 0.2 - 1.0 MW

Monte Davis adds: ideally, adaptive optics should be able to get 96% of FEL output power through the atmosphere

Blaise Gassend, Exponential Tethers for Accelerated Elevator Deployment

My talk went great!

Steven Patamia, Analytic Model of Real-Time Large-Scale Elastic Dynamics of a Single-Cable Space Elevator

Ben Shelef, The Power System for the Climbers

Great talk, I was paying too much attention and forgot the notes.

Monte Davis adds: 20-ton climber at 100m/sec: near earth, that's 20 MW or four locomotives' worth Can't dump waste heat into ribbon -- contact area too small and transient Why climb the ribbon at all? Consider a continuous feed of ribbon from the base, pulled out by centrifugal force -- high ribbon consumption, but you get *all* your lift energy -- altitude as well as orbit velocity -- from the angular momentum of the earth-SE system.

John Spadaro, Talking about Electrical Characteristics

Sven BilÚn, AIAA Space Tethers Technical Committee

Ken Davidian, Centennial Challenges Programmatic Overview

Ben Shelef, Segment Based Ribbon Architecture

Ben Shelef, LEO based deployment

Cool talk, he's clearly done his homework.

Marvin Bumgardner, Analysis of Forces and Environmental Conditions in the Operating Regions of the Space Elevator

Joe Gardner, Man-made Satellites: A Predictable Threat to the Space Elevator Ribbon

Dan Dzierski, Orbital Debris: A Case Study in Debris Encountered by the Space Elevator

Day 2: Tueday June 29th 2004

Brian Chase, The Political and Legislative Landscape

Monte Davis adds: Bush's Moon/Mars proposal represents good news (openness to big initiatives in space) and bad news (decision makers may not be open to your alternate/competing big initiative). Get good information into the stake holders' hands... and get *samples* of best current ribbon candidates into their hands.

Darel Preble, Clean Power; Space Solar Power; Why the SunSat Act

James Gardner, Building a Sustainable Political Consensus for Construction of a Space Elevator

This talk was done with James over the phone.

Bradley Edwards: Design an Development of a Prototype Climber

Monte Davis adds: in climber design, "everything is exponentially dependent on everything else". [my comment: CNTs may tame the ugly exponential of the thickness and taper ratio... once built, the SE removes the ugly exponential of the rocket equation... and Brad's done a great job with the bonded-tape "bootstrap" method, but ugly exponentials keep trying to sneak back in with every extra pound, kW, or day of construction time on the initial "spider" climbers as we see here]

Larry Bartosek, A Preliminary Ribbon Climber Mechanical Design with Focus on Tribology and Fatigue

Monte Davis adds: Steel is a "magic metal" for fatigue resistance. It heals microcracks in use, so for many purposes you can assume infinite lifetime. BUT-- it's heavy, so you think of lighter non-ferrous metals. No one has ever asked non-ferrous metal rollers to turn that often, so no fatigue data anywhere near our needs. Everything about the drive train depends sensitively on coefficient of friction

Gary Campbell, A Tropopause Way Station and a Mirror Solar Power System for the Climbers: A Refinement of the Space Elevator Concept.

Anders Jorgensen, Space Elevator Radiation Hazards and how to Mitigate them

Didn't take very good notes here, but the bottom line is that this is a massive issue for the transport of humans.

Monte Davis adds: so far only 21 Moon-bound astronauts have passed through the Van Allen belts -- and they were going 36,000 kph ( <30 min. exposure). If SE is going 200 kph, exposure becomes very serious. Very rough calculations suggest SE occupant going to GEO would need 10-12 INCHES of aluminum to keep whole-body dose down to Apollo astronaut levels.

Matthew Cummings, DoD Space Test Program

Blaise Gassend, Non-Equatorial Space Elevators

My talk went great!

Brad Edwards, Current Status of ISR's Space Elevator Program

Monte Davis adds: "Current Status...": pushing hard for 10-20 GPa in bulk in 2005 Risks of "analysis inertia": so many dependencies that you may stop looking at innovation because its effects would ripple too far

Bryan Laubscher, Space Elevator Systems Level Analysis

Michael Laine asked a question about whether a speaker from the previous conference had had some results. It transpires that there seems to be a breakthrough, but it won't be public for a few months. Intriguing...

Peter Swan, Architectural View - 1 Space Elevator

I have trouble doing justice to these architectural talks in my notes; they make me zone out...

Darilyn Dunkerly, Space Elevator Engineering Knowledge Base (SEEK)

(...)

Laura Pullum, Resolving Cognitive Conflict During the Technology Development Process for the Space Elevator

(...)

Monte Davis adds: Get those responsible for various subsystems to agree on relative priorities: difficult, but vital

Eric Westling, The Scaling of the Space Elevator

(...)

Monte Davis adds: one vivid example of scalability + leverage: adding two 200-ton SEs gives you 200x the cargo capacity of initial 20-ton SE for only 2.67 times the investment

Mervyn Kellum, Solar Power Satellite Systems with a Space Elevator

Andrew Price, Branding the Space Elevator

Check out http://www.healthspace.ca/spacebridge/danglingparticiple for his blog.

Bryan Laubscher, Science on a Space Elevator

Robert Munck, Educating the Public about the Space Elevator

Great talk, full of insight, easy to follow and well presented.

Day 3: Wednesday June 30th 2004

Derek Shannon, The Sideways Space Elevator

Bryan Laubscher, Defense of a Space Elevator Abstract

Dr. Anthony Yancey, Carbon Nano Technology - An Occupational Medicine Perspective

(...)

Ron Morgan, What we Know about the Health Effects of Carbon Nanotubes

Steven Sullivan, Talking about his company's (NanoSource, Inc.) nanotube process.

Looks really cool, but I see a lot of hurdles to feasibility. I asked the guy a bunch of questions at the end, but didn't get enough data to determine whether this has been studied well enough or not.

Panel Discussion

Panel made up of Brad Edwards, Tom Rogers, Robert Sackheim, Donna Shirley, Paul Spudis, George Whitesides.

Brad

Tom

George

(...)

Robert

(...)

Donna

Did a poll of how many people in the room are related to NASA projects. Only 3 or 4 were.

Paul

Missed the first few minutes.

Question session