A man for his times: then and now

The history of Zucrow Labs is the history of a moment and a man. “Cometh the hour, cometh the man,” is the classic adage, and in this case the hour was the need for rocket propulsion systems at the birth of the space age, and the man was Maurice J. Zucrow.

On the Labs’ 75^th anniversary in 2024, it’s hard not to pay tribute to the man who joined the Purdue University faculty in the School of Aeronautics and Astronautics in 1946. In 1948, he wrote the seminal and definitive book on jet propulsion, “Principles of Jet Propulsion and Gas Turbines,” essentially laying out the fundamentals of rocket science. This was followed quickly by the construction of the Rocket Propulsion Laboratory to support his research.

In the decades since, Purdue has become synonymous with aviation propulsion and space flight. From Amelia Earhart to the first and last men on the moon, to the development of the Space Shuttle main engines, Zucrow works with government entities, corporations, defense, academic institutions and more, welcoming everyone from Wernher von Braun to Elon Musk.

Set on more than 24 acres, Zucrow Labs retains its mantle of preeminence today as the largest academic propulsion lab in the world, with active research programs in rockets, turbines, compressors, energetic materials, fluid mechanics, hypersonics and all kinds of combustion.

If it propels the world forward, you’ll find it at Zucrow.

One-of-a-Kind

A remarkable man, Zucrow was born in Kyiv, Ukraine, in 1899 and emigrated with his family from there to London in 1900. He grew up in a tough but close-knit neighborhood in the East End, became a boxer and excelled in school. He immigrated to the U.S. in 1914 and started on his precocious path, entering Harvard in 1919 and becoming the first to graduate with a bachelor’s degree in engineering from that school. He was also the first student to receive a PhD from Purdue’s College of Engineering, completing his dissertation in mechanical engineering in 1928.

Following his studies at Purdue, Zucrow spent 17 years in the aerospace industry, most notably as lead engineer at Aerojet for new, groundbreaking rocketry projects like jet-assisted takeoff, rocket engines for aircraft, rocket propulsion for early ballistic missiles and “sounding” rockets, which carry instrumentation into space for research.

In 1946, he returned to academia at Purdue. After building the Rocket Propulsion Lab for his work, Purdue then constructed the Combustion Laboratory in 1952, the Gas Turbine Laboratory in 1954, and in 1965, the High Pressure Rocket Research Laboratory, which turned out to be the culmination of Zucrow’s career, as he retired a year later. Zucrow passed away in 1975.

The accolades reflect his impact. Among many instances of recognition: election to the Board of Directors of the American Rocket Society in 1957, the Distinguished Civilian Service Award from the Department of the Army in 1967, and an honorary doctorate from Purdue in 1970.

Dawn of the Space Age

It was a momentous time in 1946, when Zucrow returned to Purdue. While the start of the Space Age is often dated by the Soviet Union’s Oct. 4, 1957, launch of Sputnik, the decisive research into propulsion and rocket technology that was the sina qua non for orbital journeys was proceeding apace in the decade prior to that stunning feat.

The operational capabilities of the rocket-propelled V-2 during World War II demonstrated the possibility for space flight. Recognizing the potential of jet propulsion, legendary Purdue Engineering Dean A. A. Potter and President Fredrick Hovde — who, during World War II, had been the U.S. chief of rocket ordinance research, for which he received the President’s Medal for Merit — searched for the top person in the field to teach and oversee a research program. Zucrow fit the bill and accepted the offer to come to West Lafayette.

After his hiring, the first order of business was constructing a large physical facility with enough space for the analytical and experimental programs. Purdue was assisted by a grant from the Office of Naval Research; its $20,000 award was matched by the Purdue Research Foundation to construct a new rocket facility, the Rocket Propulsion Laboratory.

The facility was set in a farmer’s field at the southwest edge of campus. Adjacent to Purdue Airport, the country’s first university-owned airport, the lab had space for two rocket motor firing cells, a control and instrument room, a machine shop for building rocket motors, a chemistry lab and graduate student desks. There was no electric power; the juice came from a four-cylinder diesel electrical generator set, which was war surplus from the Navy.

There was also no phone service to the remotely located lab. Communication with Zucrow's office in the AeroSpace Sciences Laboratory a mile away was jerry-rigged via an army field telephone, which was operated by hand crank and also war surplus. Lines were strung on fence posts.

The Rocket Propulsion Laboratory was connected with Purdue power, water and phone service in 1951. Additional test cell space enabled expansion, from initial work on the effects of high chamber pressure operation on performance and heat transfer to ignition characteristics of propellants and droplet combustion. The techniques for obtaining rocket propellant ignition delays developed at Purdue became the industry standard for many years.

One Lab after Another

The Combustion Laboratory was built in 1952, providing space for three test cells and control rooms, as well as on-site office space for Zucrow, his assistants, secretaries and graduate students. An instructional classroom served the growing number of graduate students now in the program. The lab was extensively remodeled in 1955, extending the test cell wing with four additional test cells and control rooms, and adding a new wing to the building.

The Gas Turbine Laboratory, completed in 1954, provided space for an enlarged machine shop, three gas turbine component test cells and control rooms, two Navy surplus high-pressure air compressors, a welding shop and an experimental equipment assembly room.

The High Pressure Rocket Research Laboratory, built in 1965, was designed to accommodate experimental rocket motors. Liquid nitrogen stored in a large cryostat was pumped to a high pressure and then evaporated to pressurize the rocket motor propellant tanks. High pressure propellant tanks and all necessary propellant piping were installed in the test cell building. Over the years, this building also hosted active gas turbine research programs led by professors Arthur Lefebvre and Mac Mellor. In the early 2000s, professors Steve Heister and Jay Gore secured $2 million from the Indiana Economic Development Corp. (IEDC) to modernize the High Pressure Laboratory and revitalize both rocket and air-breathing propulsion research at Zucrow. 

The largest expansion in Zucrow’s history occurred in 2015-2017 with construction of the High Pressure Combustion Laboratory (ZL8), adding five new high-pressure combustion test cells, a state-of-the-art laser diagnostic lab, a 1,500-degree-Fahrenheit air heater, and additional control rooms, offices and workshops.

From Potholes to Lasers

At this point, the facility was unrecognizable from its 1948 origins.

“When I became director of the Labs, you had to drive under a one-lane railroad bridge and turn onto a pothole-filled road to get here,” said Robert Lucht, Ralph and Bettye Bailey Distinguished Professor of Mechanical Engineering and director of Zucrow Labs. “Beginning in 2015, Zucrow Labs became a permanent construction site. The first thing we did was repair the road and replace the railroad bridge so trucks could get in. This began a building spree that has continued right to the present day.”

Lucht isn’t exaggerating. “In 2017, we opened the High Pressure Combustion Laboratory. In 2020, we expanded and built two new modern test cells for compressor research in ZL1 and established a state-of-the-art facility for synthesis of advanced energetic materials in ZL4,” he said. “In 2021, as part of the new Discovery Park District, Saab opened a factory right next door, manufacturing fighter jet airframes; Rolls-Royce erected an office building nearby and has a hybrid engine testing facility under construction. In 2023 we opened the Hypersonics and Applied Research Facility (HARF), a first-of-its-kind, $41 million research facility with hypersonic wind tunnels, shock tubes, manufacturing labs and secure entry for national defense research.”

The biggest bangs take place in the High Pressure Combustion Laboratory, a complex that offers state-of-the-art test cells for research and access to rocket engines, gas turbines and other propulsion equipment. A climate-controlled Laser Diagnostics Lab, built next to each test cell, employs laser diagnostics to measure and characterize propulsion flow fields.

Small-scale combustion facilities allow a group of very active researchers to develop and test new forms of energetic materials, like propellants and explosives. Zucrow Labs also features very active programs in air-breathing propulsion, including compressors, turbines, combustion of carbon-free fuels and advanced combustion technologies, including rotating detonation engines, ramjets and scramjets. Test cells for both air-breathing and rocket propulsion components — compressors, turbines and combustors — can accommodate experiments at realistic pressures and power levels, along with workshops to help researchers experiment with their designs. Control rooms with thousands of channels of data acquisition enable researchers to analyze their work. Fully stocked machine shops let students custom-build their experiments.

Today, Zucrow Labs remains at the forefront of creating and refining the “fundamentals of rocket science that first empowered the U.S. to build ballistic missiles for the Cold War and civilian rockets for space exploration,” said Mike Smith, a professor of history in Purdue’s College of Liberal Arts and author of “The Rocket Lab: Maurice Zucrow, Purdue University, and America’s Race to Space,” the story of Zucrow’s life and times.

Newest Lab

On Manufacturing Day on Oct. 4, Eckhard Groll, the William E. and Florence E. Perry Head and Reilly Professor of Mechanical Engineering; Arvind Raman, the John A. Edwardson Dean of the College of Engineering and the Robert V. Adams Professor in Mechanical Engineering; and Bill Crossley, the Uhrig and Vournas Head of Aeronautics and Astronautics, cut a ceremonial ribbon at the dedication of the new $73 million High-Speed Propulsion Lab, otherwise known as ZL9.

The scale of ZL9 dwarfs the facilities in ZL8 and features a new, high-pressure air plant that represents an order-of-magnitude increase in capabilities compared to the old air compressor system. ZL9 features new testing capabilities for innovative research in rocket combustion and gas turbine engines, continuing Purdue’s history of world-class research and development in those areas at a scale only found in government or large defense contractor facilities. The new lab will augment Purdue’s advanced propulsion testing and research prowess.

“There is no other university-affiliated institution that can manufacture and then test propulsion technologies, including hypersonic technologies, at flight-relevant scales and conditions all in the same place,” Raman said.

The Greatest Legacy

Zucrow’s primary discoveries came from studying propellant mixtures, fluid flow, high pressures and heat exchangers to improve the efficiencies of rocket engines. He proved the advantages of high-pressure combustion for rocket engines to increase their carrying capacity and range. But these advances were also the results achieved through the efforts of his student teams.

Today, Zucrow Labs remains at the forefront of research, experimentation and real-world development in many critical areas for space exploration and national security. As vital as that is, so is its contribution to young learners, the men and women who will execute on those challenges for technological superiority and national security in the days and years to come.

During the time that Zucrow was at the helm, his “greatest legacies were his students: 27 PhD graduates and some 250 MS graduates,” Smith said. “They were mechanical engineers and aeronautical engineers, with expertise in jet propulsion, like turbojets and rockets, and in nuclear propulsion.”

Zucrow was outgoing but tough, according to Smith, who said that he had a great sense of humor and cared for his colleagues and students, yet never spared them sharp and constructive criticism. He demanded precise and impeccable writing and speaking skills. He guided students with the theoretical basics, to “act on truth,” and then let them “learn by doing.” He created a laboratory and support system for his graduate students to learn on their own, make mistakes and overcome them, and support each other as classmates and mentors. He taught them to prepare for a full-bodied professional career from the start. And he helped them get jobs.

Smith cites some student accomplishments. “Bruce Reese directed technical development of the NIKE anti-ballistic missile for the Kennedy administration. Col. Walter Moe managed the transfer of the Apollo program’s Saturn F-1 engines from the Air Force to NASA,” he said. “At the Rocketdyne Corporation, Stanley Gunn helped prove the viability of the Saturn’s J-2 liquid-hydrogen engines, and was lead engineer for nuclear rocket propulsion. J.P. Sellers helped redesign and improve the Saturn F-1 and J-2 engines, which worked 100% in the Apollo missions. Bob Osborn helped prove the viability of the solid-rocket boosters for the Shuttle.”

From the Students

Purdue is known as the “Cradle of Astronauts” because of its many contributions to the U.S. space program, including supplying it with 27 astronauts, like Neil Armstrong and Gus Grissom. Many of these luminaries of the astronaut fraternity and sorority have passed through the Labs.

NASA astronaut Jerry Ross said this of his time at Zucrow: “I knew that it was Purdue engineers and scientists that were involved in our country’s very early parts of the space program efforts, so I decided that I was going to go to Zucrow Labs, that I was going to become an engineer and I was going to get involved in our country’s space program.”

Another NASA astronaut, Loral O’Hara, had this to say: “The work that I got to do at Zucrow designing, building and testing hardware was the first time that I really got to take a project from the initial concept stage all the way through to test, so that was really cool. I really enjoyed doing that, and that’s actually what set the stage for the rest of my career.”

Today’s students are continuing that enthusiasm that underpins the American space program.

“At Zucrow, we cover it all,” one said. “We work on gas turbine combustors, compressors, liquid and solid rocket engines, rotating detonation engines, engines that sound like elephants and detonation experiments that rattled the windows.”

Added another, “All this takes place in an environment that allows us to design, build and operate our own experiments. This is something you can’t find at other university labs.”

Said another, “When I go to interviews, I’m never asked about my GPA, I’m never typically asked about what I do in my classes. I’m asked what I do on this rocket team. How did my last test operation go. The training Zucrow gives you is like nothing else. There’s nothing else in the country like this.”

It’s all part of the Purdue ethos: the persistent pursuit of the next giant leap.

“My mission in life is to enable us to get off this rock,” explained a Zucrow student. “I want to be part of that effort to design the rocket that will get us there and hopefully beyond.”

That’s what Maurice Zucrow meant when he said of his labs, “These laboratories are the keys for opening those new frontiers so necessary to the healthy development of our society.”

Purdue President Mung Chiang put it this way, at a 75^th anniversary dedication ceremony: “We dedicate here today, as Dr. Zucrow dedicated his team in 1946. And we dedicate ourselves to the everlasting journey to create and disseminate knowledge. We dedicate our support to the talents of Boilermakers, and we dedicate to propel Purdue Engineering to the pinnacle of research excellence.”