Jim Van Zandt's Home Page

Among my interests are Linux, woodworking, and science fiction. You can reach me by email to: jrvz at comcast dot net.

Space Elevators

Arthur C. Clarke and several other science fiction authors have written about a stationary structure that would let a vehicle climb into space, instead of using a rocket motor. The hitch is that an extremely strong material is needed. Now such a material has been discovered - a carbon nanotube - and people have started engineering work on building what's now called a "space elevator".

I attended the Third Annual Space Elevator Conference in Washington D.C. in June of 2004. The reference design uses a tapered ribbon to optimize the payload for a given mass of ribbon. At the conference, Blaise Gassend pointed out the advantages of a non-tapered ribbon, which could take the form of a continuous loop. For details, see Blaise's page.

Since then, I've realized one could split the elevator up into several loops, connected by pairs of pulleys.

This gives us the advantages of a tapered ribbon: The center loop can be wide to carry its higher load, and the outer loops can be narrower. The lower loops could also be optimized for local conditions - wind, LEO debris, monatomic oxygen, etc. The figure shows only three loops, but you could have as many as necessary.

It also preserves the major advantage of Blaise's proposal: we can do away with the solar-cell powered "climber" able to climb a vertical ribbon at 200 km/hr and go for 100,000 km without major repairs - yet cheap enough to pay for itself with a single trip (remember that all the early climbers don't come back down, but are only added to the counterweight). Instead, the motors for the elevator can stay on the ground where energy is cheap, they can be as heavy as we like, and they can stay in use for years. What goes up with each payload needs to be little more complicated than a clamp.

In each pair of connecting pulleys, the lower pulley would have a generator and the upper pulley a motor. The loops would not have to run at the same speed - probably the lowest loop (which runs partly in the atmosphere) would run the slowest. Just as in a cable car, the loops would never stop moving. (They would store a tremendous amount of kinetic energy, and would take a long time to get up to speed.)

The pulleys would have to be massive to transfer the load - unlike in Blaise's original proposal, where the maximum load on the lower pulley would be only slightly more than the payload weight.

I don't think ribbon tangling should be a problem. The ascending segments would tend to lag (westward) and the descending segments lead (eastward). The same would be true of the reference design, with an ascending climber pulling the ribbon westward and a descending climber pulling it eastward. However, I expect the effect would be much more pronounced with a loop because there is much more mass in the ribbon(s) than the climber(s).

Update 2005-03-19: It turns out Ian Wollard has suggested something similar. http://www.liftport.com has a relevant thread.

If you have comments, please join the discussion on the mailing list: space-elevator@yahoogroups.com

Linux Systems

I have installed Linux on several systems. Here are some descriptions:

• A Dell Latitude X300 notebook
• A Tyan S2466N-4M (dual processor Athlon)
• A Gateway Solo 3350 notebook
• An HP 7270 Pavilion

I spent some time getting Xprint configured so that firefox would print correctly. Here's my description.

I have a nice HP optical USB mouse, but in X it was far too sensitive (3/4 inch of mouse movement to send the screen pointer from one side to the other of my 1280x1024 display). xset could not reduce the sensitivity. The "resolution" value in /etc/X11/XF86Config-4 seems to be ignored for USB mice. Eventually, I found a kernel change at http://novalug.tux.org/video/secrets-of-cinelerra.html. Here's a patch against the 2.6.16 kernel sources. This change also affected gpm, making the mouse in a virtual console too slow. I added "-r 20" to the gpm command line to compensate.

Hardware

Our HP 6P printer started misfeeding paper and leaving black marks on the back of pages. We eventually figured out that the exit rollers had deterioriated and need replacing. Here are the step-by-step instructions.

Software

• transform-0.8.tar.gz (18k) At present, gnuplot only knows about linear and log axes, and with a log axis only the powers of 10 are labeled. I'd like to generalize this, at least for the equivalent of "probability paper" and "weibull plots", and preferably for any reasonable user-supplied function. adapt is a stand-alone program to generate user tic marks for gnuplot, according to these rules:
  • Place no tics or minitics outside the range specified by the user.
  • Don't allow tic labels to overlap.
  • Choose the "simplest" tics to label (i.e. those with the fewest significant digits).
  • Subject to the above, place tics with approximately even density.
  • Ensure the value corresponding to each minitic is obvious.
  • Subject to the above, place enough minitics that the user can easily interpolate to find the value for any point on the graph.
  It relies on a small patch that lets user tics include minitics. Here are some examples: The latter may be compared with the plot in Weibull's paper or with commercial Weibull plotting paper. Eventually I would like to integrate this code into gnuplot.
• autoproject - a script to start a programming project using autoconf, automake, and optionally a command line parser generator:
  • autoproject-0.20.tar.gz (112k) source distribution
  • autoproject-0.14-1.all.deb (72k) Debian package*
  • RPMs are at Hans Ecke's site
• adjtimex - a program to display or set the Linux kernel time variables, and to monitor the systematic drift of the system time and the hardware clock:
  • adjtimex-1.21.tar.gz (61k) source distribution
• Emacspeak is a software package by T. V. Raman that adds speech output to Emacs, allowing a blind person to use it. Since Emacs can act as a shell, this allows access to most functions, not just file editing.

  I wrote the original Emacspeak_HOWTO documentation. It includes instructions on how a blind person can install Slackware Linux. You can also download a plain text version, or a tarball of the html version.

• There is an Emacspeak tutorial. The current version is emacspeak-tutorial-1.0.tar.gz.
• Emacspeak binary packages:
  • emacspeak_24-3_all.deb (1944k) current Debian package*
  emacspeak_26.0-1_all.deb (2078k) draft Debian package*
• Combined Emacspeak speech server package for the DoubleTalk and LiteTalk speech synthesizers from RC Systems, Braille 'n Speak, Braille Lite, and Type 'n Speak devices from Blazie Engineering, Accent, and Apollo 2 speech synthesizers:
  • emacspeak-ss-1.9.1.tar.gz (36k) source distribution (mostly TCL, some C)
  • emacspeak-ss_1.9.1-1_i386.deb (27k) Debian package*
  • Check Matt Campbell's page for RPMs
• Modular Linux device driver for the DoubleTalk PC speech synthesizer from RC Systems:
  • dtlk-1.12.tar.gz (39k) source distribution for 2.0.x kernel
  • dtlk_1.12-2_i386.deb (82k) Debian package*
  • dtlk-1.19.tar.gz (40k) source distribution for driver module for new stable kernel (2.2.x)
  • dtlk-patch-2.2.2 (26k) patch for the new stable kernel sources
  Note that Linux kernel sources 2.2.5 and later have this DoubleTalk PC support built in. You only have to configure it (answer "y" to the question "Double Talk PC internal speech card support?") and rebuild the kernel.
• Emacspeak server for the DECtalk Express (C language). Since Dr. Raman's TCL driver works fine for the DECtalk Express, this was intended primarily as a starting point for other synthesizers. It works with Emacspeak 5.0. In more recent versions of Emacspeak, command names have changed (shorter) and semantics have changed (to support pausing). If you want to write a server for another synthesizer, please check out the emacspeak-ss package first.
  • d-exp-1.10.tar.gz (42k) source distribution
• am-file-dialog - a file selection dialog for Amulet:
  • am-file-dialog-1.1.tar.gz (10k)
• Draft Short Course on Shared Libraries under Linux
• diffsys.c, a function to integrate an ordinary differential equation by the Bullirsch-Stoer method, as described in:

  R. Bulirsch and J. Stoer, "Numerical Treatment of Ordinary Differential Equations by Extrapolation Methods", Numerische Mathematik 8, 1-13 (1966).

  This is my C translation of the Algol program in the paper, along with the two test problems.
• dis86.zip disassembler for '86 architecture object code, under DOS (shareware)

For blindness-related files, please also check the BLinux ftp archive.

Ideas

Here are some things I wish someone would put onto the market:

• Tool tips for hardware. With modern graphical user interfaces (GUIs), one can usually let the mouse hover over a control and get a pop-up "tool tip" that explains that control. I think any hardware device with an alphanumeric display should follow the same philosophy. Take, for example, the radio in my car. If I touch a button with my bare finger, even without pushing it, the radio should be able to detect the change in capacitance. After a certain dalay, it should display a short description of what that button does, for example "toggle between stopping at every channel and stopping only at strong signals".
• Osmotic Power Generation Stations. It takes energy to remove salt from sea water, which is why desalination is expensive. It turns out the process can be run backwards: If you allow salt water and fresh water to mix in a controlled manner, you can get energy out. Quite a bit, actually: the difference in osmotic pressure between sea water and fresh water is about 28 bars, equivalent to a "head" of about 280 m! A river mouth would seem to be a good site for such a power plant. ABB Alstom Power published a study which estimated the price of an osmotic energy power plant at 36 times more than a conventional plant, and concluded it was too expensive. However, with osmotic energy you don't need to buy fuel. They did not quote a break-even time. Also, osmotic energy would not release any global warming gasses or other pollution. Posted 2002-11-30.
• Bolo for police. For non-lethal weapons, the police have rubber bullets and tear gas. While they are useful for crowd control, I don't think they are useful for stopping someone trying to run away. For that, I think the bolo has a lot of potential. One approach would be to simply equip and train policemen to use the traditional bolo (three balls fastened together with cords in the shape of a Y). They're supposed to be a lot easier to master than a lariat. Or, one could develop a modern version. For example: Mount one ball on the muzzle of a firearm like a rubber bullet (note: I don't know if rubber bullets really work this way) and hold the other two out to the left, with the cords stretched between. Fire somewhat to the right of the escapee, at knee height. The momentum given to the first ball soon has to be shared with the other two, so all three fly with one third the velocity of the original ball. Ideally, escapee will be hit by the cord and entangled. There won't be much harm done if the whole arrangement bounces off the ground. On the other hand, it could easily wrap itself around any vertical poles along the way (parking meters, trees, etc.). In selecting the length of the cords, there is a design tradeoff between risk of missing the escapee and risk of entanglement.
• Time coded dyes. A dye that changes color predictably would have many uses. If it were not temperature sensitive, it would be useful for many legal or financial documents:
  • Driver's licences
  • Airline boarding passes
  • Theater tickets
  • Discount coupons
  • Virtually any other document with a future date on it

  A temperature sensitive dye would be useful for many kinds of product expiration notices:

  • Drugs
  • Food
  • Adhesives (to signal the end of the cure time)
  • Wet paint signs that change to something like "probably dry now"
  I don't know enough chemistry to design such a system, but I have given some thought to general principles. A simple system could be based on a slow chemical reaction -- like oxidation of a thin film or the slow developing of a Polaroid picture. A faster transition might be achieved with two competing reactions, where the color change would happen when one reaction ran out of gas. Posted 2002-04-12.
• Barrier Towels. A multi-layer disposable towel with an absorbent layer, a moisture barrier, and layer that provides a good grip. Useful for cleaning up things you really don't want to touch, like bodily fluids. Also good for use with solvents: Apply a small amount of solvent to the towel, smooth it onto the surface to be cleaned, and let it sit for a minute to give the solvent a chance to work. The moisture barrier keeps the solvent from evaporating. Then wipe. Posted 2002-03-20. Update 2002-05-25: Jay Kominek reports pet stores sell something like this. I have not been able to find it there, myself.
• Bordered napkins. Put a fold along two or three edges of a paper napkin so crumbs that hit the napkin don't just slide off onto the floor. Posted 2002-03-20.

Tracy Van Zandt

• She's been doing well.

Last modified: 2006-09-03