John C. "Jack" Marshall relives early AEDC days

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Jack Marshall can remember spending his childhood craning his neck to watch airplanes flying over his house near Detroit, Mich., on their way to the major cities in the Eastern U.S.

Coupled with his intense joy at taking things apart just to see how they worked and then trying to put them back together again, is it any wonder that he sought an education and career in aeronautical engineering?

When Marshall was in junior high his parents read an article about a West Coast school that was touted to have a great engineering curriculum. So they sent for a catalog from the California Institute of Technology. Marshall then planned his high school studies around the institute's entrance requirements.

He entered Caltech in the fall of 1945 and received a bachelor's in mechanical engineering in June 1949. Two years of graduate study at Caltech brought him a master's in aeronautics in June 1951.

"During my final year of study, I began to wonder what I was going to do with all this great education," he commented. "I certainly didn't want to be at a drafting board designing aircraft pieces, as I saw so many engineers doing in the aircraft industry."

He jokingly says, "As if on command, I attended a presentation about AEDC given by John Wild of ARO, Inc., and then Maj. Bernard Marschner of AEDC. It was as if they knew I was looking for them."

The following day, he had an interview with Wild and a few months later, July 5, 1951 to be exact; Marshall began work as an engineer in the Propulsion Wind Tunnel (PWT).

Marshall said his career at AEDC can be classified has having three distinct periods. The first of the three was in preparation for, and carrying out, the initial operation of the 16-foot transonic (16T) wind tunnel.

16-foot transonic wind tunnel

His first major assignment (in 1952) was as a part of the team that designed, built and operated the one-foot transonic (1T) tunnel. The project had a code word PEEWEE that was used for expediting shop work and purchase requests and for many years, he said, people around AEDC called the wind tunnel PEEWEE.

According to an earlier High Mach article, it wasn't a fancy tunnel. It was housed in a little wood and tin building, and some of the crew that ran the first test wondered if the building would take it as the tunnel began rumbling and roaring.

The little wind tunnel that could was tagged PEEWEE because it was only a one-foot model. The purpose was to study the operating parameters of the 16T design and to investigate the effects of different test section wall configurations. Out of this work, Marshall said, came the slant-hole perforated wall that is still in use today.

Around 1955, he joined Bill Wimbrow in establishing the project engineering section that would handle aerodynamic tests in 16T.

"We prepared a host of standard forms for assisting the project engineer in setting up a test project, and organized all the information into a Project Engineer's Procedure Manual," he said. "Although the forms changed regularly as times created new methods and systems, this manual was still in use as a general guideline when I retired in 1984."

The second phase of Marshall's AEDC career began in 1961.

Low density, high Mach number wind tunnel (LORHO

At that time, he explains, the Air Force was considering developing a set of large test units to study flow at very high speeds and very high altitudes--conditions that would be encountered when re-entering Earth's atmosphere from space flight.

Bill Wimbrow was to head up the branch to carry out the research needed to design such facilities, and Marshall joined him as supervisor of a section to investigate the aerodynamic operating parameters of what was to be called the LORHO wind tunnel. The LORHO program came to an end in the late 1960s.

"We designed, built and operated a model of such a facility to evaluate the operating performance and to investigate the test environment," Marshall said.

"During this period, I did perhaps my best personal effort in an analytical sense by creating a computer code to define the testing environment."

This code, he said, calculated the flow from the initial reservoir at high pressure and temperature through the nozzle and into the test section. Both chemical dissociation and thermal vibration non-equilibrium effects were modeled.

"Bill MacDermott did some exotic measurements of the flow in the wind tunnel, and we found quite good agreement with the results of my code," he said. "My code was later adapted to predict flow properties in the arc-powered facility to study ablation."

The third and final phase of Marshall's AEDC career started in November 1967.

4-foot transonic wind tunnel

In response to an Air Force need to improve the delivery of weapons from aircraft to ground targets, a new test facility was being prepared for the express purpose of running tests on the separation of weapons from aircraft.

"This was to be called the 4-foot transonic (4T) wind tunnel," he said. "It was to include a Captive Trajectory Support (CTS) system which would determine the weapon trajectories online as the test was run."

He essentially remained in the same role for the rest of his time at AEDC.

"We tested just about all the Air Force weapons with most of the operational aircraft in those years," he explained. "We had such a significant part in the development of the new F-16 airplane that I was invited to the roll-out ceremony in Fort Worth, Texas when the plane was officially presented to the Air Force and the public."

According to Marshall, there were two fairly significant additions to the test capability during his years here.

First, the capability of doing Free-Drop separation tests requiring special model design and tunnel operation procedures was added. Second, the CTS were computerized so that the wind tunnel and the data reduction process were integrated to produce weapon trajectories "on the fly."

"This produced a significant increase in data output," he commented. "I gave quite a few papers on our test work and attended a number of technical sessions during this time period, and thus became fairly well known in the aerodynamic testing community--even internationally."

After his retirement from AEDC in 1984, Marshall moved to Fort Walton Beach, Fla. In his work with 4T, he had made many friends at Eglin AFB, so he felt it was a fruitful place to find a new job. He took a position with General Research Corp., doing engineering support for various offices in the Air Force Armament Laboratory.

 He spent one year with them writing technical proposals, followed by two years as the field manager on a technical support contract at Eglin.

The rest of his time with General Research Corp. was spent mainly developing computer simulations of missile flight to study guidance and control issues and to evaluate missile intercept techniques against incoming ballistic missiles.

"This was a fun time for me," he said. "I had no supervisory responsibilities and could follow whatever path seemed to me to lead to a desired answer. It all came to an end when the cold war ended and the DoD research and development budget got cut. No enemy; no need to do research."


During the interview process Marshall was asked what he considered his best time at AEDC and without hesitation said, "Just being a part of all the interesting things going on there, especially in the early years. Everything was new. We were on the cutting edge of supersonic flight and the space age."

Marshall also thought one of the great strengths of AEDC over the years has been the quality of the people there, both Air Force and contractor.

"Not only were they talented in their fields, but they were willing to try new ways. And they did it with success," he said. "As a result, AEDC achieved a world-wide reputation for excellence. We were the leaders."

He was also asked the "AEDC-typical" question, why is AEDC unique?

"AEDC was born of the need for uniqueness," he said. "General Arnold had the foresight to recognize the U.S. couldn't get a leg up on the rest of the world unless we went beyond the ordinary."

He continued, "No commercial outfit could afford to build and operate the kinds of facility that would lead us into the jet age -- and make us leaders. The things that AEDC was envisioned to do were the definition of unique. AEDC has remained viable by continuing to look for unique ways to add to the national research and development effort. Let's hope that it remains unique in the future."

To caveat that sentiment, when asked if he thought AEDC would exist in 50 years Marshall offers a different perspective.

"That depends on the will and foresightedness of the Air Force and the government," he explained. "There will always be a need for research and development. Whether those in charge of AEDC will be able to adapt to the changes in the research and development needs -- and in a timely fashion -- will tell the tale."

Marshall has three children from a previous marriage, all of whom live in Tennessee; the oldest, a daughter Dana, is married and lives on a farm near Estill Springs. The only son, Tyler, is a civil engineer who graduated from Tennessee Tech. and still lives in Cookeville. Before entering Tennessee Tech. Tyler worked as a draftsman and engineer's assistant for the contractor that built ASTF.

The youngest child, a daughter Kimberley, lives in Tullahoma, and her son is a member of the Tennessee National Guard. Marshall currently lives in Florida with his wife Judith, who is a nurse.