NASA John H. Glenn Research Center at Lewis Field is a NASA center within the cities of Brook Park and Cleveland between Cleveland Hopkins International Airport and the Rocky River Reservation of Cleveland Metroparks, with a subsidiary facility in Sandusky, Ohio. Its director is James A. Kenyon. Glenn Research Center is one of ten major NASA facilities, whose primary mission is to develop science and technology for use in aeronautics and space. As of May 2012, it employed about 1,650 civil servants and 1,850 support contractors on or near its site.

In 2010, the formerly on-site NASA Visitors Center moved to the Great Lakes Science Center in the North Coast Harbor area of downtown Cleveland.

The installation was established in 1942 as part of the National Advisory Committee for Aeronautics (NACA) and was later incorporated into the National Aeronautics and Space Administration as a laboratory for aircraft engine research.

It was first named the Aircraft Engine Research Laboratory after funding was approved in June 1940. It was renamed the Flight Propulsion Research Laboratory in 1947, the Lewis Flight Propulsion Laboratory (LFPL) in 1948 (after George W. Lewis, the head of NACA from 1919 to 1947), and the NASA Lewis Research Center in 1958.

On March 1, 1999, the center was officially renamed the NASA John H. Glenn Research Center at Lewis Field, in honor of John Glenn, who was a fighter pilot, astronaut (the first American to orbit the Earth) and a politician.

As early as 1951, researchers at the LFPL were studying the combustion processes in liquid rocket engines.

The 6,400-acre (2,600 ha) NASA John H. Glenn Research Center at the Neil A. Armstrong Test Facility or just Neil A. Armstrong Test Facility, formerly the NASA John H. Glenn Research Center at Plum Brook Station or just Plum Brook Station, in southern Erie County, Ohio, near Sandusky, is also part of Glenn (41°20′59.4″N 82°39′01.8″W / 41.349833°N 82.650500°W / 41.349833; -82.650500). It is located about 50 miles (80 km) from the main campus. It specializes in very large scale tests that would be hazardous on the main campus.

As of 2015, the station consisted of five major facilities:

• B-2 Spacecraft Propulsion Research Facility
• Combined Effects Chamber
• Cryogenic Components Laboratory: slated for demolition
• Hypersonic Test Facility
• Space Power Facility

The Plum Brook Reactor was decontaminated and decommissioned under a 2008 cost-plus-fee contract valued at more than $33.5 million.

In 2019 the U.S. senators from Ohio, Rob Portman and Sherrod Brown, proposed to rename Plum Brook Station after Neil Armstrong. The legislation was signed into law on December 30, 2020, and Plum Brook Station was renamed the Neil A. Armstrong Test Facility.

The B-2 Spacecraft Propulsion Research Facility is the world's only facility capable of testing full-scale, upper-stage launch vehicles and rocket engines under simulated high-altitude conditions. The Space Power Facility houses the world's largest space environment vacuum chamber.

The icing Research Tunnel is a wind tunnel capable of simulating atmospheric icing condition to test the effect of ice accretion on aircraft wings and body as well as to test anti-icing systems for aircraft.

The Zero Gravity Research Facility is a vertical vacuum chamber used for dropping experiment payloads for testing in microgravity. It enables the investigation of the behavior of components, systems, liquids, gases, and combustion when dropped in vacuum.

The facility consists of a concrete-lined shaft, 28 feet (8.5 m) in diameter, that extends 510 feet (160 m) below ground level. An aluminum vacuum chamber, 20 feet (6.1 m) in diameter and 470 feet (140 m) high, is contained within the concrete shaft. The pressure in this vacuum chamber is reduced to 13.3 newtons per square meter (1.3×10atm) before use.

The facility also includes a smaller drop tower with a free fall time of 2.2 seconds and a much lower cost per drop. It is used for the Dropping In Microgravity Environment (DIME) educational program.

The facility was designated a National Historic Landmark in 1985. It has been the world's largest microgravity facility since the 2003 closing of the Japan Microgravity Centre.

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NASA Glenn does research and technology development on jet engines, producing designs that reduce energy consumption, pollution, and noise. The chevrons it invented for noise reduction appear on many commercial jet engines today, including those used on the Boeing 787 Dreamliner.

The Glenn Research Center, along with companies it has hired, are credited with the following:

• The liquid hydrogen rocket engine, which Wernher von Braun called the critical technology that allowed the Apollo Moon landings.
• The Centaur upper-stage rocket
• The gridded ion thruster, a high-efficiency engine for spaceflight. A Glenn-derived ion engine was used on the NASA probe Deep Space 1.
• The Electrical Power System for Space Station Freedom. A slightly modified version is used on the International Space Station.
• The Universal Stage Adapter for the planned Block 1B iteration of the Space Launch System (SLS).

NASA Glenn's core competencies are:

• Air-breathing propulsion
• Communications technology and development
• Space propulsion and cryogenic fluids management
• Power, energy storage, and conversion
• Materials and structures for extreme environments

The Glenn Research Center is home to the Lewis' Educational and Research Collaborative Internship Program (LERCIP). It provides internships for high school and college students and high school teachers. The high school program is an eight-week internship for sophomores and juniors with interests in science, technology, engineering, math, or professional administration. The college level consists of a 10-week internship and is open to college students at all levels. Only residents of the Cleveland area are eligible for high school LERCIP, but college LERCIP is open to students nationwide. Interns work closely with their NASA mentors and are involved in the daily activities of the center. They are expected to be available to work 40 hours a week for the duration of the internship. The LERCIP Teacher program is a 10-week internship for educators in STEM fields.

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The Dropping In Microgravity Environment is an annual contest held yearly by the center. Teams of high school students write proposals for experiments to be performed in the Drop Tower. The winners travel to the center, perform their experiments, and submit a research report to NASA.

After 2004, NASA had been shifting its focus towards space exploration as mandated by the Vision for Space Exploration. Because of this, it was perceived by some that regional NASA centers like Glenn, which focus on research and technology, were becoming more and more marginalized in terms of resources and relevance. However, on May 13, 2006, it was announced that NASA Glenn Research Center had secured management of the Crew Exploration Vehicle's service module, which promised to generate billions of dollars and hundreds of jobs for the center. This work secured the center's future in the near term, and signalled a shift in priority for the center from aeronautical research to space exploration, aligning itself closer with NASA's new mission.

Another change of direction created uncertainty in 2010, however, when President Obama and Congress declared the end of the Vision for Space Exploration and sought to chart a new course for human space flight and NASA. However, the 2015 budget for NASA made substantial increases to projects in which the Research Center participates, such as aeronautics research, planetary science and space technology, and some of that funding was expected to flow down to the center.

The Visitor Center closed in September 2009 with many displays shifted to the Great Lakes Science Center, and new ones created there. This move was done to reduce the public relations budget and to provide easier access to the general public, especially the under-served community. It was hoped that putting the displays at the much more visited science center will bring the NASA Glenn facility more public exposure. In fact, this proved true: compared to the 60,000 visitors per year at its former site, the Glenn Visitor Center enjoyed 330,000 visitors in the first year at the Great Lakes Science Center. The new display area at the science center is referred to as the Glenn Visitor Center.

The NASA Glenn Research Center also offers public tours of its research facilities on the first Saturday of each month. Reservations must be made in advance.

• NASA Environmental Management System

• NASA.gov: official Glenn Research Center website Archived 2021-12-06 at the Wayback Machine
• NASA Glenn Visitor Center Archived 2021-11-22 at the Wayback Machine
• Engines and Innovation: Lewis Laboratory and American Propulsion Technology (NASA SP-4306, 1991) Archived 2021-03-07 at the Wayback Machine—The whole book, including photos and diagrams in on-line format.
• Historic American Engineering Record documentation, filed under Cleveland, Cuyahoga County, OH:
  • HAER No. OH-124, "Rocket Engine Testing Facility, NASA Glenn Research Center", 14 photos, 12 measured drawings, 24 data pages, 3 photo caption pages
  • HAER No. OH-132, "Altitude Wind Tunnel, NASA Glenn Research Center at Lewis Field", 120 data pages
  • HAER No. OH-133, "Space Power Chambers, NASA Glenn Research Center at Lewis Field", 106 data pages
  • HAER No. OH-134, "Altitude Wind Tunnel Support Buildings, NASA Glenn Research Center at Lewis Field", 93 data pages
  • HAER No. OH-136, "Glenn Research Center, Propulsion Systems Laboratory No. 1 and 2, John H. Glenn Research Center, 21000 Brookpark Road", 137 data pages