Measurement is the first step to success. If you can’t measure something accurately, it can’t be understood or improved. That is especially true for the spacecraft rockets and engines designed to operate under extreme temperatures and pressures at liftoff, or space stations the size of a six-bedroom house that must support people living and working in space for years.
NASA’s Marshall Space Flight Center in Huntsville, AL, understands the importance of measurement accuracy. The center specializes in hardware testing of systems for the Space Launch System — the most powerful launch vehicle ever built that will carry humans to deep space and ultimately on a journey to Mars — as well as other spacecraft.
Researchers at the Metrology and Calibration Laboratory (MCL) at Marshall make sure every instrument that takes measurements during tests for the International Space Station (ISS), the Space Launch System (SLS), or other NASA programs is accurate. About 96 percent of Marshall’s measurement and test equipment is calibrated through the lab in support of center operations, research and development, manufacturing, and testing for NASA projects.
“For hardware to work successfully in space, it has to be tested on Earth — sometimes in harsh environments,” said Gary Kennedy, technical representative for the Marshall Metrology and Calibration program. “That means the success of the hardware in space can be traced back to our laboratory and the accurate data made during a test.”
Equipment that takes quantitative measurements is being used to test critical elements of the SLS and the ISS. Hardware such as the liquid oxygen tank, liquid hydrogen tank, thermal protection system, and the intertank for the SLS are calibrated at the MCL prior to testing, and will be evaluated after testing for comparison. This same calibration process is used to manufacture and test the life support systems on the space station, such as the Environmental Control and Life Support System, which provides air and water for the station crew.
Marshall’s laboratory is responsible for ensuring that measurement and test equipment used by its customers are calibrated accurately and have traceable measurements to a national metrological institute. A Consensus Standard, or an Intrinsic Standard, makes certain that the type of measurement made at Marshall will be the same measurement made at another NASA center.
The MCL continually works with Marshall and other NASA customers to develop the most technically advanced measurement concepts and processes to successfully accomplish NASA objectives. Its personnel calibrate all types of measurement and test equipment, from specialized equipment for research and development, to common equipment for everyday operations and manufacturing. These capabilities include mechanical, electrical, pressure, force, and flow, along with other disciplines in 15 areas to perform more than 1,500 different types of calibration processes. For several of these unique and critical calibration processes, the lab has the only known capability in NASA, and in some cases, the only capability in the country.
NASA and Department of Defense Services branches conduct calibrations to ensure research and operations work safely and correctly. “Calibrations are only as good as the measurements and data collected,” explained Kirk Foster, manager of the MCL. “Without proper and accurate measurements, none of NASA’s missions could be successfully accomplished.”
Simulating the Solar and Space Environment
Inside Building 4605 at Marshall is the High Intensity Solar Environment Test system (HISET), the only place on Earth where spacecraft systems and materials can simultaneously be subjected to the vacuum, temperatures, solar photons, and electrons and protons of solar winds like they will encounter in space.
“Space doesn’t just throw one thing at you at a time and let you deal with it,” said Todd Schneider, a physicist in the Environmental Effects Branch of Marshall’s Materials and Processes Laboratory. “Space throws heat, it throws cold, it throws radiation, UV, plasma and more, all at one time. And there are synergistic effects.”
Schneider is the principal investigator for HISET, which was created in part to test components of a Solar Wind Electrons Alphas and Protons sensor package for NASA’s Solar Probe Plus. That mission, planned for launch in 2018, will send a spacecraft closer to the Sun than ever before — within about 3.9 million miles. The instrument payload must endure heat of about 2,500 °F, as well as streams of charged particles and blasts of radiation as it sends information back to Earth.
Researchers can place a test object inside the 4-by-8-foot, cryogenically cooled vacuum chamber, seal it, and then focus carefully controlled “sunlight” and charged particles on an object as though it were in orbit around Earth, Mercury, or Mars; as though it were traveling near the edge of the solar system; or nearing the blazing corona of the Sun.
“Our team is all about simulating the space environment on the ground,” Schneider said. He works among NASA experts in ultraviolet, visible, and infrared radiation; charged particles; the dust of lunar and other extraterrestrial environments such as Mars; the impact of micrometeoroids and orbital debris — everything that astronauts or equipment will encounter traveling in space.
HISET’s unique capabilities are being used for materials testing for the Lightweight Integrated Solar Array and Transceiver (LISA-T), a thin-film solar cell and antenna structure that would be stowed for launch and deployed in orbit to provide power and communication for small satellites without the need for solar tracking systems.
The NASA space environment expertise is used by the Department of Defense and other federal agencies; the Smithsonian Astrophysical Laboratory and other research organizations; and for commercial aerospace interests, such as makers of communications or other satellites. Schneider said that at any given time, as much as half their testing is for commercial customers. The Space Environmental Effects team also tests metals and materials used on the International Space Station.
“This is a one-stop shop for a whole suite of research,” Schneider explained. “There is a wide, wide array of test capabilities here within a five-block radius.”
Many of the materials, instruments, components, and spacecraft being tested are fragile to begin with, he said, and become more so as they are subjected to the radiation, temperatures, and other conditions of simulated space. The less travel required for rounds of testing, the better for high-fidelity results, schedules, and budgets.
Rocket Fuel Pump Tests Pave the Way to Mars
NASA Marshall was the site for testing a 3D printed rocket engine turbopump with liquid methane that could power spacecraft to Mars. “This is one of the most complex rocket parts NASA has ever tested with liquid methane, a propellant that would work well for fueling Mars landers and other spacecraft,” said Mary Beth Koelbl, manager of the Propulsions Systems Department at Marshall. “Additive manufacturing, or 3D printing, made it possible to quickly design, build, and test two turbopumps with identical designs that worked well with both liquid methane and liquid hydrogen propellant.”
A turbopump is complex because it has turbines that spin fast to drive the pump, which supplies fuel to the engine. During the full power test, the turbines generated 600 horsepower and the fuel pump operated at more than 36,000 revolutions per minute, delivering 600 gallons of semicryogenic liquid methane per minute — enough to fuel an engine producing over 22,500 pounds of thrust. Three other tests were completed at lower power levels. Hydrogen turbopump component testing and testing with a liquid oxygen/liquid hydrogen breadboard engine were completed in 2015. These tests, along with manufacturing and testing of injectors and other rocket engine parts, are paving the way for advancements in 3D printing of complex rocket engines, and more efficient production of future spacecraft including methane-powered landers.
“Methane propulsion and additive manufacturing are key technologies for the future of exploration including NASA’s journey to Mars,” said Graham Nelson, a Marshall propulsion engineer who helped with the testing. “We’re excited to complete testing that advances both these technologies at the same time, and improves the capabilities of future missions.”
Testing ensures 3D printed parts operate successfully under conditions similar to those in landers, ascent vehicles, and other space vehicles. Test data are available to American companies working to drive down the cost of using this new manufacturing process to build parts that meet aerospace standards. All data on materials characterization and performance are compiled in NASA’s Materials and Processes Technical Information System (MAPTIS), which is available to approved users.
- NASA Marshall Space Flight Center
- Watch a video of the rocket fuel pump being tested.
- LISA-T Project
- Solar Probe Project
- MAPTIS Test Data Program