L5 Society at UT Austin

Gerard O'Neill's advocacy for settling the High Frontier inspired the formation of the L5 Society in 1975, and was soon reflected at UT Austin and McDonald Observatory in West Texas. As described in The Visioneers, The University of Texas in Austin, for instance, hosted an active chapter that met regularly. Harlan Smith, an astronomy professor with a passion for popularizing science, was a member and later served on L5’s board of directors. Another member, Deborah Byrd, soon started writing and producing StarDate, an Austin-based telephone message service that, in 1978, became a nationally syndicated radio segment on space and astronomy topics. ... It is difficult to construct an exact and detailed demographic picture of the L5 Society’s membership. But evidence shows that it was especially strong in California, Washington, Texas, and Arizona, states that were part of the postwar “Gunbelt,” where the nation’s defense contractors were concentrated. As one would expect, there were more extensive pockets of support near universities and centers of aerospace activity. [1]

Many from that era remember The High Frontier, the Whole Earth Catalog, StarDate, and Music from the Hearts of Space. Dave Ahl's Creative Computing can easily be added to that list. All very useful to keep in mind in the context of the HRC DEC-10 from 1975 to 1982.

Interesting list of L5 members on the upper-left, including UT and McDonald Observatory's Harlan Smith.

Classic image of the interior of an O'Neill Cylinder.

[1] McCray, W. Patrick. The Visioneers: How a Group of Elite Scientists Pursued Space Colonies, Nanotechnologies, and a Limitless Future. Princeton: Princeton University Press, 2012.

[2] O’Neill, Gerard K. The High Frontier: Human Colonies in Space. New York: William Morrow & Co., 1977.

[3] The L5 Society was directly inspired by Gerard O'Neill and founded in 1975 by the Hensons in Tucson. The Visioneers gives an interesting description, The Hensons were an energetic and opinionated (some detractors also used words like aggressive and abrasive) couple who shared a pronounced enthusiasm for science fiction writers like Heinlein, Clarke, and Asimov. Like many other young American couples their age, the Hensons, whether for philosophical or financial reasons, strove to be more self-sufficient. Their rambling house, located just off the university campus, had a large garden and was home to an array of chickens, goats, and rabbits. The Hensons’ house offered visitors unconventional entertainment options. A network of underground tunnels ran beneath it and, instead of a television, the Hensons built a Tesla coil that created entertaining displays of electrical sparks. Meanwhile, the open desert spaces around Tucson allowed them to indulge a fondness for recreational explosives by reenacting scenes from Tolkien’s Lord of the Rings with homemade pyrotechnic devices. [1]

[4] Both the L5 Society, active from the mid-70s through the 1980s, and Music from the Hearts of Space, launching on KPFA in 1973 and nationally in 1983, emerged from the same countercultural and futurist West Coast milieu. The ethereal, expansive electronic and ambient soundscapes curated by host Stephen Hill provided an unofficial sonic backdrop for the burgeoning space migration, orbital settlement, and futurist philosophy championed by L5 activists. Listeners of late-night public radio in the 1970s and 1980s frequently overlapped with early space colonization advocates, blending atmospheric listening habits with high-tech optimism about Lagrange point habitats.

[5] For a fictional idea of life on the High Frontier, especially in O'Neill Cylinders, two intertwined scifi collections are highly recommended. Bruce Sterling's Schismatrix collection, and William Gibson's Sprawl collection, Neuromancer and Mona Lisa Overdrive in particular. There are intentional connections between the worlds in both collections, especially with regard to the construction and centuries-long evolution of O'Neill Cylinders, with the Schismatrix stories set in the far-future, long after the near-future Sprawl stories. Sterling is an Austinite, and Gibson a repeat guest. A good question is how much contact there was with the UT Austin L5 Society. It's even possible that Sterling was to some extent aware of Decwar, as he was an early personal computer and BBS user, as discussed in 1992's The Hacker Crackdown.

[6] Additional note, a week later. Was reading the appendix of O'Neill's High Frontier and found the following. Anyone remotely associated with UT aerospace knows about Hans Mark's role after his 1984 arrival in Austin. He is the aerospace counterpart to Harlan Smith in UT astronomy. In September 1974 I gave a colloquium-lecture at Ames, and for the first time met the director of the laboratory, Dr. Hans Mark (later Undersecretary of the Air Force in the Carter Administration).  Dr. Mark, a physicist who spent the early part of his career in nuclear physics of a military nature, has the reputation of working at least six days a week, of always arriving at work at 7:30 A.M., and of leaving the laboratory in the evening only long after everyone else but the night shift has gone.  It was a pleasure to talk to him, and we soon arranged that we would "bootleg" a brief but intense research effort on space colonization by choosing that as the topic of the 1975 NASA Ames/Stanford University Summer Study.  That study, one of an annual series supported by NASA and held in cooperation with the American Society of Engineering Education, was already funded, and the director of the laboratory was free to choose its topic each year.

Symbolic Interactive Matrix Processing Language and MATLAB

Student oriented software became a focus at UT from 1971, championed by faculty such as John Allen, Joseph Lagowski, and George Culp. The efforts centered in the Project Computer-Based Education office in the aerospace building, still referred to as the Engineering Sciences Building at the time but changed to WRW soon after. The project was a high-level initiative at UT Austin, researching how students learn through computer-assisted instruction and designed as a five-year curriculum development effort, 1971 through 1975, involving seventy-five professors and over 4,000 students in the creation of classroom modules. 

Probably the most significant artifact of the instructional ecosystem was the Symbolic Interactive Matrix Processing Language, or Simple, a direct ancestor of the commercial Matlab environment still common in engineering today. Conceived as a conversational, matrix-oriented programming language, Simple was designed as a bridge for beginners in engineering who needed to work with sophisticated matrix calculations despite minimal prior computational experience. The focus was on computer-based teaching techniques in undergraduate science and engineering education and transforming the teaching of linear algebra and numerical analysis. It was generally used via remote terminals, specifically acoustically coupled Datapoint terminals and standard teletypes, which allowed students to bypass the delays of traditional batch computing. It included a Teach command that was central to the instructional shift, providing self-paced, inquiry-based documentation that enabled students to obtain quick results and proceed at their own rate. For the mature user in aerospace or structural engineering, Simple provided rigorous tools for complex operations, including essential matrix decompositions. By accommodating both batch and timesharing modes, Simple ensured its own survival and grounded high-level engineering research in a versatile, interactive everyday tool. 

The workaday success of Simple and Matlab has demonstrated the real-world value of this type of code. Despite a distinct lack of glamour and hype, they endure because they reflect a deep connection between engineering and computational modeling and simulation. This special corner of the software world and its particular links to the engineering world are well worth further exploration. A quote from Matlab’s creator Cleve Moler captures this, here he's discussing the course he taught at Stanford circa 1980. 

The computer science students and numerical students were not very impressed. This was not a sophisticated language, they were taking courses from Don Knuth and John McCarthy, and so on, who did real computer science. There was not much mathematics going on here, these algorithms were old, traditional algorithms, there was no convergence theory, no partial differential equations, this was not the usual fare for the graduate course in matrix computation. The other half of the students in that class were students that had come from various departments in engineering, electrical engineering, mechanical engineering, nuclear engineering, they knew about matrices, they’d used matrices a lot in their theoretical work, many of their textbooks described things in terms of matrices. They had done computation with matrices using Fortran. Some of them knew about LINPACK and EISPACK, when they saw MATLAB they thought this was terrific.

Moler created Matlab in the mid seventies at the University of New Mexico in Albuquerque and it would be good to learn how much influence Simple had on the beginnings of Matlab. There were definite connections between UT and New Mexico, particularly in the context of White Sands and Los Alamos. 

Aerospace building before it was renamed WRW. Engineering Laboratories, completed 1960. Home of Project Computer-Based Education.

Former site of WRW, lower center.

[1] Oral History Interview with Cleve Moler.

[2] 1972 Project C-BE article in the Alcade.

[3] 1976 Creative Computing article mentioning Project C-BE.

Houston and Austin

The subsurface modeling techniques developing in Houston were naturally addressed as part of David Young’s UT Austin course on numerical analysis, where Mary Wheeler first began working with them on the UT CDC 1604 in the early sixties. Dynamic partial differential equations are used to model transient time-varying physical processes, with the classic example being the two-dimensional heat flow equation. In the realm of computational geosciences, these equations are used to model and simulate transient fluid flow and transport through porous media, predicting how oil, gas, or groundwater move over time. Solving these massive, multidimensional time-dependent equations with early computers was difficult until the Alternating Direction Implicit method was created to break them down into simpler, one-dimensional steps. Wheeler dedicated her 1963 master's thesis at UT to rigorously analyzing the mathematical properties of ADI, which had been developed a decade earlier by Douglas, Rachford, and Donald Peaceman at Exxon precursor Humble Oil to solve PDEs on the severely memory-constrained IBM CPC. [1][2]

Wheeler's work at UT served as an introduction to Henry Rachford and Jim Douglas, both of whom had transitioned from Humble Oil to Rice and made it a center for the computational modeling and simulation associated with the oil industry. Rachford served as Wheeler's doctoral advisor at Rice. Under his guidance, she moved into the field of subsurface flow problems, discovering a passion for environmental applications that would define her career. Her work at Rice was also guided by Douglas, who recognized her analytical skills and became a lifelong mentor. They were establishing the computational foundations for simulating fluid flow in underground porous media and their mentorship was the defining influence on Wheeler's career trajectory and research philosophy. She frequently cited them as the fathers of the field who taught her the importance of combining theoretical depth with practical utility. Together, this group became one of the most influential teams in numerical analysis during the seventies, coauthoring significant papers, such as research on superconvergence and procedures for flux modeling. 

These were important connections between computing at UT Austin, Exxon, Rice, and Houston. Mary Wheeler became involved at UT in the early sixties before moving to Rice, and then returning to UT in the nineties. Another sign was the story of how Humble Oil donated its IBM CPC to UT in 1958. UT’s Al Matsen was a consultant for Exxon Houston and New Jersey for over thirty-five years. The CPC was a landmark gift and a direct result of Matsen’s extensive ties. To bypass bureaucratic paperwork, Matsen, his graduate students, and other faculty physically carried the heavy components into Welch Hall and installed it themselves. Exxon had acquired the CPC in 1952 and used it heavily for creation of the ADI techniques. 

The history of SOR Successive Over-Relaxation and the work of David Young at TRW and UT was focused on fluid and heat flows for atmospheric reentry vehicles. At the same time, ADI and the work of Peaceman, Rachford, and Douglas in Houston was focused on fluid and heat flows for the oil industry. The nature of the modeling and the computing hardware was similar, the approaches involved in ADI and SOR were complementary. Mary Wheeler was a direct bridge between the two, beginning with David Young in Austin in the early sixties, moving over to Houston and ADI for several decades, then returning to Austin in the nineties.

Mary Wheeler

Henry Rachford and the IBM CPC at Exxon precursor Humble Oil in Houston, circa 1953.

David Young

[1] Wonderful retrospective about Rachford, Douglas, Peaceman, and ADI in Houston. 

[2] Retrospective on Mary Wheeler's career.

[3] Numerical Linear Algebra special edition dedicated to David Young. Note especially the context around Charles Warlick.

David's first job after graduating from Harvard was as an Applied Mathematician in the Computing Laboratory of the Aberdeen Proving Ground, Maryland, during 1950–1951. His fellow co-workers included Samuel Conte, Charles Warlick, and Mario Juncosa, among others. During this time, David and Mildred purchased their first new house, and had their first son, William David. At that time, Aberdeen Proving Ground contained one of the largest collections of electronic computers in the U.S. They were employed in the Ballistics Research Laboratory, primarily for the calculation of bombing and firing tables. Some of the computers that were being used at BRL included the ENIAC, which was the first general- purpose electronic computer, the ORDVAC, which was designed by John von Neumann who often visited Aberdeen Proving Ground, the EDVAC, which was a rotating drum computer, and a Bell Laboratory paper tape-driven computer. David Young and Charles Warlick worked on the ORDVAC computer using Richardson's method on a 21 x 21 grid, which required writing a tricky computer program, at that time, because the machine had a total memory of only 1024 40-bit words with no external memory. 

The University of Texas in Austin wanted to establish a Computation Center. Professor Robert Greenwood, and others from the Department of Mathematics, wrote to David, inviting him to come to Texas. At first, David dismissed the offer, because he considered Texas to be an outback area of the country. Eventually, he decided to go and take a look for himself. He was pleasantly surprised to find that Austin was quite a nice city, with a river, hills, and oak trees, as well as having a good university. Lou Ehrlich followed David from Maryland to California to Texas, and became his first PhD student in 1963. In the summer of 1958, David moved his family to Austin-he would spend the rest of his career there. David and Mildred's third child, Carolyn Ellen, was born in Austin.

In the Fall of 1958, David brought Bob Gregory to Texas to join him as a member of the mathematics faculty, and to help him set up the Computation Center-which was almost non-existent. David, Bob, and a secretary shared an office next to the computer room. The first computer was an IBM 650 Magnetic Drum Data Processing Machine, which was the world's first mass-produced computer. During the next several years, Young and Gregory purchased new computers, expanded the staff, and designed a new building for the Center, which was built partially underground near the University tower. In 1965, David asked Charles Warlick to move to Austin, and to help him run the expanding operations of the Computation Center.

Under David's leadership, The University of Texas not only built a new Computation Center building, but also acquired two large supercomputer systems-the CDC 1604 computer in 1960, and the CDC 6600 computer in 1966. Gregory was particularly interested in the CDC computers because of their long 60 bit word length. Based on his reputation, David obtained the first $400,000 grant, from the National Science Foundation, toward the purchase of the CDC 1604 computer, which was one of the first transistorized computers. The CDC 6600 supercomputer, which was one of the largest and fastest computers at that time, was purchased with the help of the first NSF million dollar equipment grant.

Tape Bridge Into The DEC-10

The skeleton of the Decwar-playing robots is turning out to have other uses. It's now also the skeleton of an automated Tape Bridge between the local system and the DEC-10, in action within Project UTEXAS as tape.py in the msc folder.

The tape.py code automatically copies files from the local filesystem into the DEC-10 filesystem. It's as quick and simple as possible, for doing fast iterations around editing local files using modern tools and then smoothly syncing those edits onto the DEC-10. It's almost a fully automated filesystem sync between the local system and the DEC-10, and in fact could be made into such by scheduling periodic runs. It runs in the Docker container where the DEC-10 lives. The container is effectively an intermediary environment between the local system and the DEC-10. The local files are available live within the container and tape.py sees and copies them there. To use tape.py, work within a terminal session connected to the container. To schedule periodic runs for example, do that in the container, not in the local system. This is necessary because the tape drive and the mounted tape live in the container as part of the DEC-10, not in the local system. In other words, the hardware is in the container. The tape exists as a .tap file within the container's environment, and meanwhile the local system is simply a place for using modern tools to edit source code.

Execution begins in the container, where tape.py creates a temporary folder and copies in all necessary files. It then executes back10, named after the DEC-10 backup utility, to convert the temporary folder into a tape image with the TOPS-10 tape format. This step generates a standard tape archive .tap file and verifies its integrity by listing its contents. If tape.py is executed with a --simple argument it terminates here, leaving the tape ready for use, and this is in fact the route taken during startup of the container when the tape is initially mounted on the drive. There is one tape mounted on the drive from container startup onwards. What tape.py can do at any time is replace the contents of the tape. One tape, many writes to it, many restores from it within the DEC-10. This one tape is the bridge between the local filesystem and the DEC-10, and many files can pass over it at various times during its lifetime. More tape drives and tapes are possible. One alone is minimalist simplicity.

When not in --simple mode the code transitions into the restoration phase, utilizing the pexpect library to establish a programmatic telnet connection to the DEC-10. With pexpect, the code sends text and monitors terminal output for expected responses. To the DEC-10 the code is indistinguishable from a human user telnetting in. The code is a robot and the overall setup is a kind of Turing Test. As long as the robot acts like a human, everything is fine. This system was developed from late 2024 for the Decwar-playing robots. The full Decwar robots are more complex, but the essential skeleton was directly adapted into tape.py in roughly an hours work. The robot opens a telnet connection and logs in, then uses the standard TOPS-10 tape utility BACKUP to restore from the tape. The tape.py code here is actually a guide on how to use BACKUP, for whenever a restore needs to be done manually. It then gracefully logs out and closes the telnet connection.

1978 UT Austin Decwar and TOPS-10

The UT Austin Decwar coders had to use MACRO-10 assembly to invoke specific TOPS-10 Unimplemented User Operations. UUOs acted as traps or interrupts that suspended user-level execution and called the TOPS-10 monitor. The monitor would then assert exclusive access over the magnetic-core memory high segment, queuing any other player-jobs attempting to write to the lists until the holding job issued an unlocking UUO. In other words, in order to use the shared memory linked lists for attack and radio messages, player-jobs had to call TOPS-10 directly via assembly code. This is the root reason that assembly code became essential for Decwar, and code in pure Fortran was simply no longer feasible. It unlocked the full potential of the DEC-10, and at the same time forever bound the code to TOPS-10. 

There was very little separation between the game and the operating system, and little hope of moving the code to even a sibling environment such as the DEC-20 and its TOPS-20 operating system. Even though TOPS-20 ran on the same 36-bit hardware, it was derived from BBN's TENEX operating system rather than TOPS-10, and it used a completely different system-call architecture known as Jump to SYStem instead of UUOs. While TOPS-20 did include a compatibility emulation library called PA1050 designed to intercept and translate old TOPS-10 UUOs into JSYS calls, this emulator had severe limitations. The PA1050 emulator was completely incapable of translating the direct physical segment locks and atomic inter-job synchronization routines that Decwar used to protect its message queues. Because the emulator relied on virtual memory page-mapping structures rather than static core segment locks, the Decwar binary simply could not run on TOPS-20 without a complete rewrite of its underlying assembly code.

The cancellation of the PDP-10 product line by DEC in 1983, and the demise of DEC itself in 1998, seemed to permanently strand the UT Austin Decwar code on an obsolete architectural island. But in another of its surprising near-death experiences, the UT code has survived and flourished in new forms far tougher and more survivable than before, through the physical and digital preservation efforts led by Obsolescence Guaranteed. The mid 2020s saw a spectacular revitalization of this ecosystem. Rather than treating historical computing as dead artifacts meant only for museums, Obsolescence Guaranteed, an informal group of computer history hobbyists and engineers, has focused on creating computer time capsules. By building affordable, fully functional hardware replicas of the classic DEC lineup, including the PiDP-1, PiDP-8, PiDP-11, and PiDP-10, they allow modern users to directly experience the tactile and interactive realities of the mainframe era.

For Decwar, the PiDP-10 replica is one form of resurrection. The PiDP-10 is a scaled-down, desktop-sized physical reproduction of the original PDP-10 KA10 front panel. It features an active array of 74 functional switches and 124 indicator lamps, driven by modern LEDs, that accurately reflect the machine's internal state. Inside this console beats a dual-hearted system: a modern Raspberry Pi that runs a physical Linux kernel concurrently with a cycle-accurate PDP-10 emulator based on Bob Supnik and Richard Cornwell's SIMH engine. Physical switch toggles on the front panel trigger interrupts on the Raspberry Pi, altering register states in the PDP-10, while memory writes are translated in real-time to illuminate the physical LEDs. 

Another more permanent and accessible resurrection is represented by Docker. The UTEXAS DECWAR 2.3 Source Distribution Tape Reconstruction is a digital time capsule containing both the source code and the TOPS-10 environment. Docker excels at creating reproducible, automated build pipelines. A Docker image encapsulates the underlying SIMH emulator, the TOPS-10 operating system, and the SDT virtual tape into a single, isolated package. This guarantees that anyone can instantly spin up the living environment as it existed on the HRC DEC-10 in 1982, without worrying about local hardware dependencies or host operating system characteristics. In fact, running in the Cloud is no different than running on local hardware. The preservation efforts go far beyond running a single standalone mainframe. The ARPANET Reconstruction Project aims to revive the ancestral Internet using Old Bits wherever possible. For UT Austin this would mean containers for the HRC DEC-10, Painter Hall DEC-20, and ARPANET IMP, with various connections through telnet and FTP links. Docker, especially using Docker Compose, is explicitly designed to orchestrate multi-node, networked applications. Instead of a user manually launching and configuring separate environments for mainframes and IMPs, a containerized setup can automatically spin up each historical machine in its own isolated container and seamlessly manage the networking between them. Placing the SIMH PDP-10 engine, historical tape images, and disk images inside a container shields users from the friction of modern software dependencies. They don't need to compile code or configure environments, but can simply start containers and immediately telnet into an Old Bits environment.

Bob Hysick at work in the HRC DEC-10 offices, quite possibly on Decwar.

Robert Schneider on the left on the evening The Soul Of An Old Machine, 1982. Robert played an important role with the code.

Tommy Loomis to the right on the same evening, also an important coder.

Rick Watson on the right, also important for the code.

[1] As always, thank you to Richard Denney and Clive Dawson for much of this material.