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By NASA
2 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Artist concept highlighting the novel approach proposed by the 2025 NIAC awarded selection of the TFINER concept.NASA/James Bickford James Bickford
Charles Stark Draper Laboratory, Inc.
The Thin-Film Nuclear Engine Rocket (TFINER) is a novel space propulsion technology that enables aggressive space exploration for missions that are impossible with existing approaches. The concept uses thin layers of energetic radioisotopes to directly generate thrust. The emission direction of its natural decay products is biased by a substrate to accelerate the spacecraft. A single stage design is very simple and can generate velocity changes of ~100 km/s using a few kilograms of fuel and potentially more than 150 km/s for more advanced architectures.
The propulsion system enables a rendezvous with intriguing interstellar objects such as ‘Oumuamua that are on hyperbolic orbits through our solar system. A particular advantage is the ability to maneuver in deep space to find objects with uncertainty in their location. The same capabilities also enable a fast trip to the solar gravitational focus to image multiple potentially habitable exoplanets. Both types of missions require propulsion outside the solar system that is an order of magnitude beyond the performance of existing technology. The phase 2 effort will continue to mature TFINER and the mission design. The program will work towards small scale thruster experiments in the near term. In parallel, isotope production paths that can also be leveraged for other space exploration and medical applications will be pursued. Finally, advanced architectures such as an Oberth solar dive maneuver and hybrid approaches that leverage solar sails near the Sun, will be explored to enhance mission performance.
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Last Updated May 27, 2025 EditorLoura Hall Related Terms
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By NASA
6 Min Read A Defining Era: NASA Stennis and Space Shuttle Main Engine Testing
The numbers are notable – 34 years of testing space shuttle main engines at NASA’s Stennis Space Center near Bay St. Louis, Mississippi, 3,244 individual tests, more than 820,000 seconds (totaling more than nine days) of cumulative hot fire.
The story behind the numbers is unforgettable.
“It is hard to describe the full impact of the space shuttle main engine test campaign on NASA Stennis,” Center Director John Bailey said. “It is hundreds of stories, affecting all areas of center life, within one great story of team achievement and accomplishment.”
NASA Stennis tested space shuttle main engines from May 19, 1975, to July 29, 2009. The testing made history, enabling 135 shuttle missions and notable space milestones, like deployment of the Hubble Space Telescope and construction of the International Space Station.
The testing also:
Established NASA Stennis as the center of excellence for large propulsion testing. Broadened and deepened the expertise of the NASA Stennis test team. Demonstrated and expanded the propulsion test capabilities of NASA Stennis. Ensured the future of the Mississippi site. The first space shuttle main engine is installed on May 8, 1975, at the Fred Haise Test Stand (formerly A-1). The engine would be used for the first six tests and featured a shortened thrust chamber assembly.NASA Assignment and Beginning
NASA Stennis was not the immediate choice to test space shuttle main engines. Two other sites also sought the assignment – NASA’s Marshall Flight Center in Alabama and Edwards Air Force Base in California. However, following presentations and evaluations, NASA announced March 1, 1971, that the test campaign would take place in south Mississippi.
“(NASA Stennis) was now assured of a future in propulsion testing for decades,” summarized Way Station to Space, a history of the center’s first decades.
Testing did not begin immediately. First, NASA Stennis had to complete an ambitious project to convert stands built the previous decade for rocket stage testing to facilities supporting single-engine hot fire.
Propellant run tanks were installed and calibrated. A system was fashioned to measure and verify engine thrust. A gimbaling capability was developed on the Fred Haise Test Stand to allow operators to move engines as they must pivot in flight to control rocket trajectory. Likewise, engineers designed a diffuser capability for the A-2 Test Stand to allow operators to test at simulated altitudes up to 60,000 feet.
NASA Stennis teams also had to learn how to handle cryogenic propellants in a new way. For Apollo testing, propellants were loaded into stage tanks to support hot fires. For space shuttle, propellants had to be provided by the stand to the engine. New stand run tanks were not large enough to support a full-duration (500 seconds) hot fire, so teams had to provide real-time transfer of propellants from barges, to the run tanks, to the engine.
The process required careful engineering and calibration. “There was a lot to learn to manage real-time operations,” said Maury Vander, chief of NASA Stennis test operations. “Teams had to develop a way to accurately measure propellant levels in the tanks and to control the flow from barges to the tanks and from the tanks to the engine. It is a very precise process.”
NASA Stennis teams conduct a hot fire of the space shuttle Main Propulsion Test Article in 1979 on the B-2 side of the Thad Cochran Test Stand. The testing involved installing a shuttle external fuel tank, a mockup of the shuttle orbiter, and the vehicle’s three-engine configuration on the stand, then firing all three engines simultaneously as during an actual launch.NASA Testing the Way
The biggest challenge was operation of the engine itself. Not only was it the most sophisticated ever developed, but teams would be testing a full engine from the outset. Typically, individual components are developed and tested prior to assembling a full engine. Shuttle testing began on full-scale engines, although several initial tests did feature a trimmed down thrust chamber assembly.
The initial test on May 19, 1975, provided an evaluation of team and engine. The so-called “burp” test did not feature full ignition, but it set the stage for moving forward.
“The first test was a monstrous milestone,” Vander said. “Teams had to overcome all sorts of challenges, and I can only imagine what it must have felt like to go from a mostly theoretical engine to seeing it almost light. It is the kind of moment engineers love – fruits-of-all-your-hard-labor moment.”
NASA Stennis teams conducted another five tests in quick succession. On June 23/24, with a complete engine thrust chamber assembly in place, teams achieved full ignition. By year’s end, teams had conducted 27 tests. In the next five years, they recorded more than 100 annual hot fires, a challenging pace. By the close of 1980, NASA Stennis had accumulated over 28 hours of hot fire.
The learning curve remained steep as teams developed a defined engine start, power up, power down, and shutdown sequences. They also identified anomalies and experienced various engine failures.
“Each test is a semi-controlled explosion,” Vander said. “And every test is like a work of art because of all that goes on behind the scenes to make it happen, and no two tests are exactly the same. There were a lot of knowledge and lessons learned that we continue to build on today.”
NASA Stennis test conductor Brian Childers leads Test Control Center operations during the 1000th test of a space shuttle main engine on the Fred Haise Test Stand (formerly A-1). on Aug. 17, 2006.NASA Powering History
Teams took a giant step forward in 1978 to 1981 with testing of the Main Propulsion Test Article, which involved installing three engines (configured as during an actual launch), with a space shuttle external tank and a mock orbiter, on the B-2 side of the Thad Cochran Test Stand.
Teams conducted 18 tests of the article, proving conclusively that the shuttle configuration would fly as needed. On April 12, 1981, shuttle Columbia launched on the maiden STS-1 mission of the new era. Unlike previous vehicles, this one had no uncrewed test flight. The first launch of shuttle carried astronauts John Young and Bob Crippen.
“The effort that you contributed made it possible for us to sit back and ride,” Crippen told NASA Stennis employees during a post-test visit to the site. “We couldn’t even make it look hard.”
Testing proceeded steadily for the next 28 years. Engine anomalies, upgrades, system changes – all were tested at NASA Stennis. Limits of the engine were tested and proven. Site teams gained tremendous testing experience and expertise. NASA Stennis personnel became experts in handling cryogenics.
Following the loss of shuttles Challenger and Columbia, NASA Stennis teams completed rigorous test campaigns to ensure future mission safety. The space shuttle main engine arguably became the most tested, and best understood, large rocket engine in the world – and NASA Stennis teams were among those at the forefront of knowledge.
NASA conducts the final space shuttle main engine test on July 29, 2009, on the A-2 Test Stand at NASA Stennis. The Space Shuttle Program concluded two years later with the STS-135 shuttle mission in July 2011.NASA A Foundation for the Future
NASA recognized the effort of the NASA Stennis team, establishing the site as the center of excellence for large propulsion test work. In the meanwhile, NASA Stennis moved to solidify its future, growing as a federal city, home to more than 50 resident agencies, organizations, and companies.
Shuttle testing opened the door for the variety of commercial aerospace test projects the site now supports. It also established and solidified the test team’s unique capabilities and gave all of Mississippi a sense of prideful ownership in the Space Shuttle Program – and its defining missions.
No one can say what would have happened to NASA Stennis without the space shuttle main engine test campaign. However, everything NASA Stennis now is rests squarely on the record and work of that history-making campaign.
“Everyone knows NASA Stennis as the site that tested the Apollo rockets that took humans to the Moon – but space shuttle main engine testing really built this site,” said Joe Schuyler, director of NASA Stennis engineering and test operations. “We are what we are because of that test campaign – and all that we become is built on that foundation.”
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Last Updated May 19, 2025 EditorNASA Stennis CommunicationsContactC. Lacy Thompsoncalvin.l.thompson@nasa.gov / (228) 688-3333LocationStennis Space Center Related Terms
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By NASA
During the Piston Powered Auto-Rama at the I-X Center in Cleveland on Monday, March 31, 2025, NASA Glenn Research Center’s Salvadore Oriti, right, discusses the technology behind free-piston Stirling cycle machines. Credit: NASA/Kristin Jansen NASA Glenn Research Center’s work in power and propulsion was on full display at the Piston Powered Auto-Rama at the I-X Center in Cleveland, March 28-30. The event is the largest indoor showcase of cars, trucks, motorcycles, tractors, and other engine-powered vehicles.
Center staff introduced guests to NASA’s Stirling engine technology, a free-piston Stirling power convertor that set records for accomplishing 14 years of maintenance-free operation at NASA Glenn in 2020. Attendees also explored how NASA is using space nuclear power to reach the deepest, dustiest, darkest, and most distant regions of our solar system through radioisotope power systems.
More than 57,500 people attended the event.
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By NASA
2 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
NASA’s X-59 quiet supersonic research aircraft sits on a ramp at Lockheed Martin Skunk Works in Palmdale, California, during sunset. The one-of-a-kind aircraft is powered by a General Electric F414 engine, a variant of the engines used on F/A-18 fighter jets. The engine is mounted above the fuselage to reduce the number of shockwaves that reach the ground. The X-59 is the centerpiece of NASA’s Quesst mission, which aims to demonstrate quiet supersonic flight and enable future commercial travel over land – faster than the speed of sound.Lockheed Martin Corporation/Garry Tice The team behind NASA’s X-59 completed another critical ground test in March, ensuring the quiet supersonic aircraft will be able to maintain a specific speed during operation. The test, known as engine speed hold, is the latest marker of progress as the X-59 nears first flight this year.
“Engine speed hold is essentially the aircraft’s version of cruise control,” said Paul Dees, NASA’s X-59 deputy propulsion lead at the agency’s Armstrong Flight Research Center in Edwards, California. “The pilot engages speed hold at their current speed, then can adjust it incrementally up or down as needed.”
The X-59 team had previously conducted a similar test on the engine – but only as an isolated system. The March test verified the speed hold functions properly after integration into the aircraft’s avionics.
“We needed to verify that speed hold worked not just within the engine itself but as part of the entire aircraft system.” Dees explained. “This test confirmed that all components – software, mechanical linkages, and control laws – work together as intended.”
The successful test confirmed the aircraft’s ability to precisely control speed, which will be invaluable during flight. This capability will increase pilot safety, allowing them to focus on other critical aspects of flight operation.
“The pilot is going to be very busy during first flight, ensuring the aircraft is stable and controllable,” Dees said. “Having speed hold offload some of that workload makes first flight that much safer.”
The team originally planned to check the speed hold as part of an upcoming series of ground test trials where they will feed the aircraft with a robust set of data to verify functionality under both normal and failure conditions, known as aluminum bird tests. But the team recognized a chance to test sooner.
“It was a target of opportunity,” Dees said. “We realized we were ready to test engine speed hold separately while other systems continued with finalizing their software. If we can learn something earlier, that’s always better.”
With every successful test, the integrated NASA and Lockheed Martin team brings the X-59 closer to first flight, and closer to making aviation history through quiet supersonic technology.
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Last Updated Mar 26, 2025 EditorDede DiniusContactNicolas Cholulanicolas.h.cholula@nasa.gov Related Terms
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By NASA
6 Min Read NASA Stennis Flashback: Learning About Rocket Engine Smoke for Safe Space Travel
An image shows engineers at an early version of the test stand at the Diagnostic Testbed Facility. From 1988 to the mid-1990s, NASA Stennis engineers operated the facility to conduct rocket engine plume exhaust diagnostics and learn more about the space shuttle main engine combustion process. Credits: NASA/Stennis NASA’s Stennis Space Center near Bay St. Louis, Mississippi, is widely known as the nation’s largest rocket propulsion test site. More than 35 years ago, it also served as a hands-on classroom for NASA engineers seeking to improve the efficiency of space shuttle main engines.
From 1988 to the mid-1990’s, NASA Stennis engineers operated a Diagnostic Test Facility to conduct rocket engine plume exhaust diagnostics and learn more about the space shuttle main engine combustion process. The effort also laid the groundwork for the frontline research-and-development testing conducted at the center today.
“The Diagnostic Test Facility work is just another example of the can-do, will-do attitude of the NASA Stennis team and of its willingness to support the nation’s space exploration program in all ways needed and possible,” said Joe Schuyler, director of the NASA Stennis Engineering and Test Directorate.
The Diagnostic Test Facility work is just another example of the can-do, will-do attitude of the NASA Stennis team…
joe schuyler
NASA Stennis Engineering and Test Directorate Director
Tests conducted at the Diagnostic Testbed Facility played a critical safety role for engine operations and also provided a real-time opportunity for NASA Stennis engineers to learn about exhaust diagnostics. NASA/Stennis An image shows the Diagnostic Testbed Facility test stand data acquisition trailer. NASA/Stennis The Need
Envision a rocket or space vehicle launching into the sky. A trail of bright exhaust, known as the engine plume, follows. As metals wear down in the engines from the intense heat of the combustion process, the flame glows with colors, some visible, such as orange or yellow, and others undetectable by the human eye.
The colors tell a story – about the health and operation of the engine and its components. For space shuttle main engines, which flew on multiple missions, engineers needed to understand that story, much as a doctor needs to understand the condition of a human body during checkup, to ensure future engine operation.
Where better place to study such details than the nation’s premier propulsion test site? Paging NASA Stennis.
An image shows the rocket motor and thruster at the Diagnostic Testbed Facility. NASA/Stennis An image shows the Diagnostic Testbed Facility blended team of NASA personnel and contractors. Kneeling, left to right, is Brantly Adams (NASA), Felix Bircher (Sverdrup Technology), Dennis Butts (Sverdrup Technology), and Nikki Raines (Sverdrup Technology). Standing, left to right, NASA astronaut John Young, Greg Sakala (Sverdrup Technology), Barney Nokes (Sverdrup Technology), John Laboda (Sverdrup Technology), Glenn Varner (NASA), Stan Gill (NASA), Bud Nail (NASA), Don Sundeen (Sverdrup Technology), NASA astronaut John Blaha.NASA/Stennis The Facility
NASA Stennis has long enabled and supported innovative and collaborative work to benefit both the agency and the commercial space industry. When NASA came calling in the late 1980s, site engineers went to work on a plan to study space shuttle main engine rocket exhaust.
The concept for an enabling structure about the size of a home garage was born in October 1987. Five months later, construction began on a Diagnostic Testbed Facility to provide quality research capabilities for studying rocket engine exhaust and learning more about the metals burned off during hot fire.
The completed facility featured a 1,300-square-foot control and data analysis center, as well as a rooftop observation deck. Small-scale infrastructure was located nearby for testing a 1,000-pound-thrust rocket engine that simulated the larger space shuttle main engine. The 1K engine measured about 2 feet in length and six inches in diameter. Using a small-scale engine allowed for greater flexibility and involved less cost than testing the much-larger space shuttle engine.
An image shows Sverdrup Technology’s Robert Norfleet as he preps the dopant injection system for testing at the Diagnostic Testbed Facility. The goal of the facility was to inject known metals and materials in a chemical form and then look at what emissions were given off. During one test, generally a six or 12 second test, operators would inject three known dopants, or substances, and then run distilled water between each test to clean out the system.NASA/Stennis An image shows engineers Stan Gill, Robert Norfleet, and Elizabeth Valenti in the Diagnostic Testbed Facility test control center. NASA/Stennis The Process
Engineers could quickly conduct multiple short-duration hot fires using the smaller engine. A six-second test provided ample time to collect data from engine exhaust that reached as high as 3,900 degrees Fahrenheit.
Chemical solutions simulating engine materials were injected into the engine combustion chamber for each hot fire. The exhaust plume then was analyzed using a remote camera, spectrometer, and microcomputers to determine what colors certain metals and elements emit when burning.
Each material produced a unique profile. By matching the profiles to the exhaust of space shuttle main engine tests conducted at NASA Stennis, determinations could be made about which engine components were undergoing wear and what maintenance was needed.
We learned about purging, ignition, handling propellants, high-pressure gases, and all the components you had to have to make it work…It was a very good learning experience.
Glenn Varner
NASA Stennis Engineer
The Benefits
The Diagnostic Testbed Facility played a critical safety role for engine operations and also provided a real-time opportunity for NASA Stennis engineers to learn about exhaust diagnostics.
Multiple tests were conducted. The average turnaround time between hot fires was 18 to 20 minutes with the best turnaround from one test to another taking just 12 minutes. By January 1991, the facility had recorded a total of 588 firings for a cumulative 3,452 seconds.
As testing progressed, the facility team evolved into a collection of experts in plume diagnostics. Longtime NASA Stennis engineer Glenn Varner serves as the mechanical operations engineer at the Thad Cochran Test Stand, where he contributed to the successful testing of the first SLS (Space Launch System) core stage onsite.
However, much of Varner’s hands-on experience came at the Diagnostic Test Facility. “We learned about purging, ignition, handling propellants, high-pressure gases, and all the components you had to have to make it work,” he said. “It was a very good learning experience.”
An image shows the Diagnostic Testbed Facility team working in the test control center. Seated, left to right, is Steve Nunez, Glenn Varner, Joey Kirkpatrick. Standing, back row left to right, is Scott Dracon and Fritz Policelli. Vince Pachel is pictured standing wearing the headset. NASA/Stennis The physical remnants of the Diagnostic Testbed Facility are barely recognizable now, but that spirit and approach embodied by that effort and its teams continues in force at the center.
joe schuyler
NASA Stennis Engineering and Test Directorate Director
The Impact
The Diagnostic Testbed Facility impacted more than just those engineers involved in the testing. Following the initial research effort, the facility underwent modifications in January 1993. Two months later, facility operators completed a successful series of tests on a small-scale liquid hydrogen turbopump for a California-based aerospace company.
The project marked an early collaboration between the center and a commercial company and helped pave the way for the continued success of the NASA Stennis E Test Complex. Building on Diagnostic Testbed Facility knowledge and equipment, the NASA Stennis complex now supports multiple commercial aerospace projects with its versatile infrastructure and team of propulsion test experts.
“The physical remnants of the Diagnostic Testbed Facility are barely recognizable now,” Schuyler said. “But that spirit and approach embodied by that effort and its teams continues in force at the center.”
Additional Information
NASA Stennis has leveraged hardware and expertise from the Diagnostic Testbed Facility to provide benefit to NASA and industry for two decades and counting.
The facility’s thruster, run tanks, valves, regulators and instrumentation were used in developing the versatile four-stand E Test Complex at NASA Stennis that includes 12 active test cell positions capable of various component, engine, and stage test activities.
“The Diagnostic Testbed Facility was the precursor to that,” said NASA engineer Glenn Varner. “Everything but the structure still in the grass moved to the E-1 Test Stand, Cell 3. Plume diagnostics was part of the first testing there.”
When plume diagnostic testing concluded at E-1, equipment moved to the E-3 Test Stand, where the same rocket engine used for the Diagnostic Testbed Facility has since performed many test projects.
The Diagnostic Testbed Facility thruster also has been used for various projects at E-3, most recently in a project for the exploration upper stage being built for use on future Artemis missions.
In addition to hardware, engineers who worked at the Diagnostic Testbed Facility also moved on to support E Test Complex projects. There, they helped new NASA engineers learn how to handle gaseous hydrogen and liquid hydrogen propellants. Engineers learned about purging, ignition, and handling propellants and all the components needed for a successful test.
“From an engineering perspective, the more knowledge you have of the processes and procedures to make propulsion work, the better off you are,” Varner said. “It applied then and still applies today. The Diagnostic Testbed Facility contributed to the future development of NASA Stennis infrastructure and expertise.”
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Last Updated Feb 25, 2025 EditorNASA Stennis CommunicationsContactC. Lacy Thompsoncalvin.l.thompson@nasa.gov / (228) 688-3333LocationStennis Space Center Related Terms
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