This is the latest salvo from the Space Frontier group, urging Congress to take the money currently allocated towards finishing the Shuttle missions (approximately $20 billion, according to them) and redirect it towards commercial development of space.

It’s hard to argue with that logic.  I was a fan of the shuttle for a long time, not so much because I thought the Shuttle was the be-all and end-all of space delivery systems, but it was SOMETHING that kept a US presence in space.  But the Columbia disaster really changed my mind.

I wonder what LiftPort and/or Brad Edwards could do with $20 billion…

This is from Andy Price’s email list;

As the editor for the American Astronautical Society’s bimonthly publication Space Times, and a regular recipient of the e-mail traffic you sponsor on carbon nanotubes and space elevators, I’d like to offer you and the members of your group the opportunity to submit an article/s for our magazine.  This is an incredibly important subject, and I’d be willing to consider an entire issue dedicated to the topic if you or your associates had the interest.

I’ve attached a copy of our article submission guidelines as well as a PDF of our March/April issue.  Thank you for your consideration, and best of luck in the continuing quest to turn “The Fountains of Paradise” into a reality!

Jonathan Krezel
Editor
Space Times

I’ve attached their article submission guidelines here and a pdf (Bob Munck alert) of their March/April 2006 issue here.

A couple of people have already stepped up to volunteer articles and I’m trying to come up with a way that I can contribute as well.  If anyone is interested in contributing, please contact Andy at aprice(AT)healthspace.ca.

Dr. Bradley Edwards has recently set up a new personal webpage.  You can find it here.

Aviation Week & Space Technology has a recent article about On-Orbit Automation; efforts being made to robotically repair and refuel satellites.  At the National Space Society’s Space Elevator Special Interest Chapter, they have a copy of the article.  As they point out, this type of technology will play a significant role in Space Elevator development.

Zhiping Xu, Lifeng Wang and Quanshui Zheng propose that “condensed multiwalled carbon nanotubes (CMWNTs) can greatly enhance intershell shear strengths by several orders, and can simultaneously generate higher tensile strengths and moduli respectively than those of ordinary CNTs…It is believed that CMWNTs featured with those properties can be taken as excellent candidates of super fibers for creating space elevators.”  You can find the details here.

In the June 10th-16th issue of The Economist (the issue with picture of Zarqawi on the cover), there is a fine article summarizing the current status of the space elevator project.  This article is also available online here.

The estimable Jim Dempsey (again, via Andy Price) weighs in on the Pugno controversy and Dr. Brad Edwards comments on it.  Writes Mr. Dempsey;

Brad, your response was a good “well wait a minute” response. In particular, from my unfounded point of view, I key in on your statement:

– assumes that all CNTs will be damaged (it appears to be on a 100 nm length) and that
– none of them interact with each other in a supportive manner.

One of the major factors in building suitable SE tether material is in obtaining adequate supportive interaction without the expense of unwieldy excess mass. Anyone familiar with traditional cordage understands that supportive interaction is the key element in constructing a reliable defect tolerant cord (tether in this case).

As a thought experiment assume one were to produce 100,000KM long SWNT.  Assume you were to somehow clamp only the ends of the bundles. Given this scenario (and excluding Van der Vaal’s or electrostatic interaction) any defect subsequently introduced into a given SWNT in the bundle would weaken the bundle by one SWNT capacity. It is a virtual certainty that given the length of each SWNT this unsupportive bundle would quickly degrade. By the introduction of a suitable supportive interaction mechanism, the load bearing capacity of a damaged SWNT can bypass the local of the defect. In reading Pugno’s paper there appears to be no anticipation that a suitable supportive interaction mechanism could be found any time soon.

I am optimistic. I believe the problem is solvable, I believe it will be solved; I believe it will be solved within 5 years. But what would I know; I am not a molecular chemist.

If I “were” a molecular chemist, I would be a brash molecular chemist, I would buck the establishment, I would not be afraid to say “why not”.

I would take what little I do know, and inject this knowledge into an unrestricted pool of properties and characteristics, then draw upon this to produce subsequent precursor knowledge which goes back in the knowledge pool, and repeat the process until the solution is found.

Our current problem of finding the ideal (an acceptable) supportive interaction mechanism could potentially be an ideal candidate for genetic programming (see: http://www.genetic-programming.com/johnkoza.html).

What we know is:

Using an Atomic Force Microscope you can place and move about individual atoms on a flat crystalline surface.

We know that a supposedly flat crystalline surface at the atomic scale is bumpy.

We know that given different specimen atoms for a given surface will have different affinities to “stick” within depressions of the bumpy surface.

Given this knowledge:

I would begin experimentation with a graphene planar surface.  The experimentation preferably could be performed by way of genetic programming as it would be much faster and more comprehensive than physical lab work.

The elusive prey would be that which causes good “stiction”.  Something that “falls” deep into the surface but does not penetrate the surface. The test subjects need not be limited to atomic (ionic or charge neutral) selections but would also include molecular forms.

Next, with this reasonably large collection of potential candidates, reconfigure the simulation (or lab tests).

Then experiment with “dusting” the SWNT and bundling the SWNT to determine an optimal candidate and dusting density which produces good protection against slippage between SWNT and who’s dusting density is commensurate for the anticipated probability of environmental damage to the SWNT.

Added to the mix I would experiment with collecting various numbers of said dusted SWNT bundled and held together with a cladding.  The purpose of this cladding is not to add tensile strength but to ensure a tight binding of the SWNT bundles such that the stiction from the dusting can do its work.

The said above dusted, bundled and cladded SWNT’s would be produced in large quantities and would exhibit the mechanical and processing properties of micro fibers. Call these DBCSWNT (Dusted, Bundled, Cladded SWNT).

The above DBCSWNT would be placed en mass into a binding mixture of PET or PET-like agent and drawn many times to ensure good alignment and packing density of the DBCSWNT. Then after evaporation of solvent and curing of binder the end result is a thread of any desired length and diameter. The cross section of which need not be circular. Hexagonal cross section might be a better choice.

These threads would then be twisted or braided into larger diameter cordage (fractional mm) which is finally incorporated into the ribbon.

To date, and without being privy to what is being done, experimentation is being performed by placing the SWNT directly into the PET or PET-like agent, i.e. the stiction dusting and cladding steps above are omitted. It is my gut feel that the key to or breakthrough to manufacturing suitable tether material is in the stiction dusting and cladding components of the above mentioned process. But then, what to I know, I am not a molecular chemist.
 
Jim Dempsey

Michael Laine, Founder and President of the LiftPort Group, will address the Bay Area Future Salon on June 22nd.  Details can be found here.

At The Oklahoman, Jim Stafford tells his readers about the Space Elevator.

Further thoughts from Dr. Edwards (again via Andy Price) on the Pugno study:  

“The supportive interaction between the CNTs already exists in several forms:
1) van de Walls forces
2) physical “knotting” or twisting like cotton or any other fiber and
3) functionalized nanotubes

Any one of these could be used to cross link CNTs and effectively transfer loads and greatly reduce the overall strength reduction of any weak CNT.  There are a couple other options as well, but these have been shown to work.  By not including this in a discussion of a macroscopic material, Pugno is insuring that the material will fall apart.  Compare a raw mat of cotton to a spun cotton thread – the performance is a little different.  I can assure everyone that raw cotton fibers are not perfect throughout their length (much less so than quality CNTs) but strong threads can still be made from them.”

Forwarded from Andy Price, and with the kind permission of Dr. Edwards, following are his initial thoughts on the Pugno study;

“The paper by Pugno has been beaten around a bit.  I just read the paper, very interesting.  Let me run through a few thoughts on it.

I start off worrying when someone creates his own theory and simulation to model everything from nanoscale to megascale (nanotubes to Earth) especially when there are plenty of molecular models out there.  But having said that, let me assume his simulation is perfect for a nanotube.  He appears to have scripted the paper to claim the cable will break (he repeats this claim at least four times throughout the paper often with the note that it is his opinion) – a second worry when an author appears to be trying to prove a conclusion.  Here are a few notes I made on his discussion:
– references and then ignores coatings to eliminate atomic oxygen erosion.
– states radiation damage will cause defects but doesn’t discuss the amount.  Damage seen in experiments is minimal for carbon fibers in the radiation fields around Earth.
– I may be wrong but it appeared to me that Pugno was using a macroscopic model to represent a damaged nanotube as a solid tube with a physical hole in it.  He certainly discusses this and then discusses missing bonds so I would be curious to know which one he went with.  I will need to look at this again.
– uses an erroneous theoretical maximum of 100GPa for the tensile strength of CNTs.  CNTs have been measured at strengths from 150GPa to 200 GPa and he references one that is at 109GPa.  His final 30GPa is directly related to this.
– uses the strength of long CNT bundles to prove his arguments.  CNT bundles are not a valid comparison because they can have very short CNTs and limited interaction.
– assumes that all CNTs will be damaged (it appears to be on a 100 nm length) and that none of them interact with each other in a supportive manner.
This is from a quick read of the paper but essentially as far as I understand, Pugno makes some poor assumptions to argue that there will be damage to all the CNTs in a ribbon, calculates that each CNT will degrade 70% and then jumps to the conclusion that the ribbon will degrade 70%.  As far as I can tell he doesn’t look at or consider the structure of the CNT threads, the interactions of the CNTs, real defect type and frequency, techniques to reduce defects in production, the real defect production rates in space, the maximum measured CNT strengths, …  The paper didn’t strike me as very good scientific work.
Having said all of this, people will view my remarks as biased – a reasonable assumption.  I have attempted to be objective because I would like to know the answers as well.  I would like to request that others examine this material as well.
I applaud the attempt to examine the materials issue, but don’t think Pugno has provided a good analysis in this paper.”

Thank you Andy and Dr. Edwards.