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By NASA
5 Min Read NASA’s X-59 Moves Toward First Flight at Speed of Safety
NASA’s X-59 quiet supersonic research aircraft is seen at dawn with firetrucks and safety personnel nearby during a hydrazine safety check at U.S. Air Force Plant 42 in Palmdale, California, on Aug. 18, 2025. The operation highlights the extensive precautions built into the aircraft’s safety procedures for a system that serves as a critical safeguard, ensuring the engine can be restarted in flight as the X-59 prepares for its first flight. Credits: Lockheed Martin As NASA’s one-of-a-kind X-59 quiet supersonic research aircraft approaches first flight, its team is mapping every step from taxi and takeoff to cruising and landing – and their decision-making is guided by safety.
First flight will be a lower-altitude loop at about 240 mph to check system integration, kicking off a phase of flight testing focused on verifying the aircraft’s airworthiness and safety. During subsequent test flights, the X-59 will go higher and faster, eventually exceeding the speed of sound. The aircraft is designed to fly supersonic while generating a quiet thump rather than a loud sonic boom.
To help ensure that first flight – and every flight after that – will begin and end safely, engineers have layered protection into the aircraft.
The X-59’s Flight Test Instrumentation System (FTIS) serves as one of its primary record keepers, collecting and transmitting audio, video, data from onboard sensors, and avionics information – all of which NASA will track across the life of the aircraft.
“We record 60 different streams of data with over 20,000 parameters on board,” said Shedrick Bessent, NASA X-59 instrumentation engineer. “Before we even take off, it’s reassuring to know the system has already seen more than 200 days of work.”
Through ground tests and system evaluations, the system has already generated more than 8,000 files over 237 days of recording. That record provides a detailed history that helps engineers verify the aircraft’s readiness for flight.
Maintainers perform a hydrazine safety check on the agency’s quiet supersonic X-59 aircraft at U.S. Air Force Plant 42 in Palmdale, California, on Aug. 18, 2025. Hydrazine is a highly toxic chemical, but it serves as a critical backup to restart the engine in flight, if necessary, and is one of several safety features being validated ahead of the aircraft’s first flight.Credits: Lockheed Martin “There’s just so much new technology on this aircraft, and if a system like FTIS can offer a bit of relief by showing us what’s working – with reliability and consistency – that reduces stress and uncertainty,” Bessent said. “I think that helps the project just as much as it helps our team.”
The aircraft also uses a digital fly-by-wire system that will keep the aircraft stable and limit unsafe maneuvers. First developed in the 1970s at NASA’s Armstrong Flight Research Center in Edwards, California, digital fly-by-wire replaced how aircraft were flown, moving away from traditional cables and pulleys to computerized flight controls and actuators.
On the X-59, the pilot’s inputs – such as movement of the stick or throttle – are translated into electronic signals and decoded by a computer. Those signals are then sent through fiber-optic wires to the aircraft’s surfaces, like its wings and tail.
Additionally, the aircraft uses multiple computers that back each other up and keep the system operating. If one fails, another takes over. The same goes for electrical and hydraulic systems, which also have independent backup systems to ensure the aircraft can fly safely.
Onboard batteries back up the X-59’s hydraulic and electrical systems, with thermal batteries driving the electric pump that powers hydraulics. Backing up the engine is an emergency restart system that uses hydrazine, a highly reactive liquid fuel. In the unlikely event of a loss of power, the hydrazine system would restart the engine in flight. The system would help restore power so the pilot could stabilize or recover the aircraft.
Maintainers perform a hydrazine safety check on NASA’s quiet supersonic X-59 aircraft at U.S. Air Force Plant 42 in Palmdale, California, on Aug. 18, 2025. Hydrazine is a highly toxic chemical, but it serves as a critical backup to restart the engine in flight, if necessary, which is one of several safety features being validated ahead of the aircraft’s first flight. Credits: Lockheed Martin Protective Measures
Behind each of these systems is a team of engineers, technicians, safety and quality assurance experts, and others. The team includes a crew chief responsible for maintenance on the aircraft and ensuring the aircraft is ready for flight.
“I try to always walk up and shake the crew chief’s hand,” said Nils Larson, NASA X-59 lead test pilot. “Because it’s not your airplane – it’s the crew chief’s airplane – and they’re trusting you with it. You’re just borrowing it for an hour or two, then bringing it back and handing it over.”
Larson, set to serve as pilot for first flight, may only be borrowing the aircraft from the X-59’s crew chiefs – Matt Arnold from X-59 contractor Lockheed Martin and Juan Salazar from NASA – but plenty of the aircraft’s safety systems were designed specifically to protect the pilot in flight.
The X-59’s life support system is designed to deliver oxygen through the pilot’s mask to compensate for the decreased atmospheric pressure at the aircraft’s cruising altitude of 55,000 feet – altitudes more than twice as high as that of a typical airliner. In order to withstand high-altitude flight, Larson will also wear a counter-pressure garment, or g-suit, similar to what fighter pilots wear.
In the unlikely event it’s needed, the X-59 also features an ejection seat and canopy adapted from a U.S. Air Force T-38 trainer, which comes equipped with essentials like a first aid kit, radio, and water. Due to the design, build, and test rigor put into the X-59, the ejection seat is a safety measure.
All these systems form a network of safety, adding confidence to the pilot and engineers as they approach to the next milestone – first flight.
“There’s a lot of trust that goes into flying something new,” Larson said. “You’re trusting the engineers, the maintainers, the designers – everyone who has touched the aircraft. And if I’m not comfortable, I’m not getting in. But if they trust the aircraft, and they trust me in it, then I’m all in.”
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Last Updated Sep 12, 2025 EditorDede DiniusContactNicolas Cholulanicolas.h.cholula@nasa.govLocationArmstrong Flight Research Center Related Terms
Armstrong Flight Research Center Advanced Air Vehicles Program Aeronautics Aeronautics Research Mission Directorate Ames Research Center Glenn Research Center Langley Research Center Low Boom Flight Demonstrator Quesst (X-59) Supersonic Flight Explore More
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By NASA
Advancing Single-Photon Sensing Image Sensors to Enable the Search for Life Beyond Earth
A NASA-sponsored team is advancing single-photon sensing Complementary Metal-Oxide-Semiconductor (CMOS) detector technology that will enable future NASA astrophysics space missions to search for life on other planets. As part of their detector maturation program, the team is characterizing sensors before, during, and after high-energy radiation exposure; developing novel readout modes to mitigate radiation-induced damage; and simulating a near-infrared CMOS pixel prototype capable of detecting individual photons.
Single-photon sensing and photon-number resolving CMOS image sensors: a 9.4 Mpixel sensor (left) and a 16.7 Mpixel sensor (right). Credit: CfD, RIT Are we alone in the universe? This age-old question has inspired scientific exploration for centuries. If life on other planets evolves similarly to life on Earth, it can imprint its presence in atmospheric spectral features known asbiosignatures. They include absorption and emission lines in the spectrum produced by oxygen, carbon dioxide, methane, and other molecules that could indicate conditions which can support life. A future NASA astrophysics mission, the Habitable Worlds Observatory (HWO), will seek to find biosignatures in the ultraviolet, optical, and near-infrared (NIR) spectra of exoplanet atmospheres to look for evidence that life may exist elsewhere in the universe.
HWO will need highly sensitive detector technology to detect these faint biosignatures on distant exoplanets. The Single-Photon Sensing Complementary Metal-Oxide-Semiconductor (SPSCMOS) image sensor is a promising technology for this application. These silicon-based sensors can detect and resolve individual optical-wavelength photons using a low-capacitance, high-gain floating diffusion sense node. They operate effectively over a broad temperature range, including at room temperature. They have near-zero read noise, are tolerant to radiation, and generate very little unwanted signal—such as dark current. When cooled to 250 K, the dark current drops to just one electron every half-hour. If either the read noise or dark current is too high, the sensor will fail to detect the faint signals that biosignatures produce.
A research team at the Rochester Institute of Technology (RIT) Center for Detectors (CfD) is accelerating the readiness of these SPSCMOS sensors for use in space missions through detector technology maturation programs funded by NASA’s Strategic Astrophysics Technology and Early Stage Innovations solicitations. These development programs include several key goals:
Characterize critical detector performance metrics like dark current, quantum efficiency, and read noise before, during, and after exposure to high-energy radiation Develop new readout modes for these sensors to mitigate effects from short-term and long-term radiation damage Design a new NIR version of the sensor using Technology Computer-Aided Design (TCAD) software SPSCMOS sensors operate similarly to traditional CMOS image sensors but are optimized to detect individual photons—an essential capability for ultra-sensitive space-based observations, such as measuring the gases in the atmospheres of exoplanets. Incoming photons enter the sensor and generate free charges (electrons) in the sensor material. These charges collect in a pixel’s storage well and eventually transfer to a low-capacitance component called the floating diffusion (FD) sense node where each free charge causes a large and resolved voltage shift. This voltage shift is then digitized to read the signal.
Experiments that measure sensor performance in a space relevant environment use a vacuum Dewar and a thermally-controlled mount to allow precise tuning of the sensors temperature. The Dewar enables testing at conditions that match the expected thermal environment of the HWO instrument, and can even cool the sensor and its on-chip circuits to temperatures colder than any prior testing reported for this detector family. These tests are critical for revealing performance limitations with respect to detector metrics like dark current, quantum efficiency, and read noise. As temperatures change, the electrical properties of on-chip circuits can also change, which affects the read out of charge in a pixel.
The two figures show results for SPSCMOS devices. The figure on the left shows a photon counting histogram with peaks that correspond to photon number. The figure on the right shows the dark current for a SPSCMOS device before and after exposure to 50 krad of 60 MeV protons. Credit: CfD, RIT The radiation-rich environment for HWO will cause temporary and permanent effects in the sensor. These effects can corrupt the signal measured in a pixel, interrupt sensor clocking and digital logic, and can cause cumulative damage that gradually degrades sensor performance. To mitigate the loss of detector sensitivity throughout a mission lifetime, the RIT team is developing new readout modes that are not available in commercial CMOS sensors. These custom modes sample the signal over time (a “ramp” acquisition) to enable the detection and removal of cosmic ray artifacts. In one mode, when the system identifies an artifact, it segments the signal ramp and selectively averages the segments to reconstruct the original signal—preserving scientific data that would otherwise be lost. In addition, a real-time data acquisition system monitors the detector’s power consumption, which may change from the accumulation of damage throughout a mission. The acquisition system records these shifts and communicates with the detector electronics to adjust voltages and maintain nominal operation. These radiation damage mitigation strategies will be evaluated during a number of test programs at ground-based radiation facilities. The tests will help identify unique failure mechanisms that impact SPSCMOS technology when it is exposed to radiation equivalent to the dose expected for HWO.
Custom acquisition electronics (left) that will control the sensors during radiation tests, and an image captured using this system (right). Credit: CfD, RIT While existing SPSCMOS sensors are limited to detecting visible light due to their silicon-based design, the RIT team is developing the world’s first NIR single-photon photodiode based on the architecture used in the optical sensors. The photodiode design starts as a simulation in TCAD software to model the optical and electrical properties of the low-capacitance CMOS architecture. The model simulates light-sensitive circuits using both silicon and Mercury Cadmium Telluride (HgCdTe or MCT) material to determine how well the pixel would measure photo-generated charge if a semiconductor foundry physically fabricated it. It has 2D and 3D device structures that convert light into electrical charge, and circuits to control charge transfer and signal readout with virtual probes that can measure current flow and electric potential. These simulations help to evaluate the key mechanisms like the conversion of light into electrons, storing and transferring the electrons, and the output voltage of the photodiode sampling circuit.
In addition to laboratory testing, the project includes performance evaluations at a ground-based telescope. These tests allow the sensor to observe astronomical targets that cannot be fully replicated in lab. Star fields and diffuse nebulae challenge the detector’s full signal chain under real sky backgrounds with faint flux levels, field-dependent aberrations, and varying seeing conditions. These observations help identify performance limitations that may not be apparent in controlled laboratory measurements.
In January 2025, a team of researchers led by PhD student Edwin Alexani used an SPSCMOS-based camera at the C.E.K. Mees Observatory in Ontario County, New York. They observed star cluster M36 to evaluate the sensor’s photometric precision, and the Bubble Nebula in a narrow-band H-alpha filter. The measured dark current and read noise were consistent with laboratory results.
The team observed photometric reference stars to estimate the quantum efficiency (QE) or the ability for the detector to convert photons into signal. The calculated QE agreed with laboratory measurements, despite differences in calibration methods.
The team also observed the satellite STARLINK-32727 as it passed through the telescope’s field of view and measured negligible persistent charge—residual signal that can remain in detector pixels after exposure to a bright source. Although the satellite briefly produced a bright streak across several pixels due to reflected sunlight, the average latent charge in affected pixels was only 0.03 e–/pix – well below both the sky-background and sensor’s read noise.
Images captured at the C.E.K. Mees Observatory. Left: The color image shows M36 in the Johnson color filters B (blue), V (green), and R (red) bands (left). Right: Edwin Alexani and the SPSCMOS camera (right). Credit: : CfD, RIT As NASA advances and matures the HWO mission, SPSCMOS technology promises to be a game-changer for exoplanet and general astrophysics research. These sensors will enhance our ability to detect and analyze distant worlds, bringing us one step closer to answering one of humanity’s most profound questions: are we alone?
For additional details, see the entry for this project on NASA TechPort.
Project Lead(s): Dr. Donald F. Figer, Future Photon Initiative and Center for Detectors, Rochester Institute of Technology (RIT), supported by engineer Justin Gallagher and a team of students.
Sponsoring Organization(s): NASA Astrophysics Division, Strategic Astrophysics Technology (SAT) Program and NASA Space Technology Mission Directorate (STMD), Early Stage Innovations (ESI) Program
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Last Updated Sep 02, 2025 Related Terms
Astrophysics Science-enabling Technology Space Technology Mission Directorate Technology Highlights Explore More
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