Untangling the Mysteries of Our Solar System

As much as a robotic spacecraft can, Parker Solar Probe personifies APL’s drive to explore uncharted territory. Through six years in space, the historic probe has survived a hostile environment to deliver unprecedented data about the immediate solar atmosphere — and fundamentally change how we understand our star.

The spacecraft, which APL built and operates, accomplished a major milestone on Dec. 24 when it sped a mere 3.8 million miles (6.1 million kilometers) from the Sun’s blazing surface. Just how close is that? If the distance between Earth and the Sun were the length of a football field, the spacecraft would be around 4 yards from the end zone.

Parker will continue to execute flybys, at about the same distance and speed, with several scheduled throughout 2025.

Parker’s orbit was designed to get progressively closer to the Sun to help scientists answer the toughest questions: What heats the corona to over 300 times the solar surface temperature? How is solar wind generated and accelerated to permeate the heliosphere? And how does explosive solar activity energize particles to nearly the speed of light and drive space weather? Now that Parker is at its closest, observations are filling in some of the last missing pieces of these solar puzzles — while sparking questions for future missions to answer and mysteries for the next generations of scientists to solve.

The spacecraft also uncovered new information on the zodiacal cloud, a vast dusty cloud surrounding the Sun that carries essential information on earlier comets and asteroids, resolving the nearly century-old question of dust-free zones around stars.

“Flying through the Sun’s atmosphere is a historic and daring milestone, marking a monumental leap for science. Parker Solar Probe is unraveling enduring solar mysteries, uncovering astonishing phenomena and redefining our understanding of the Sun and its influence across the solar system — a true beacon of a new golden age in space exploration,” said Nour Rawafi, project scientist for Parker Solar Probe at APL.

Survival at the Sun

To ensure the spacecraft could withstand the Sun’s blistering heat, APL engineers constructed a 4.5-inch-thick (11.43-centimeter-thick) carbon-composite shield, designed to protect Parker against temperatures of up to 2,500 degrees Fahrenheit (1,377 degrees Celsius).

The spacecraft’s solar arrays, too, were reimagined to survive the Sun’s blistering conditions. They rely on a first-of-its-kind active cooling system developed by APL, which uses around 1.3 gallons (5 liters) of pressurized water as a coolant, pumped through titanium radiators and powered by the arrays themselves.

Equally ambitious is Dragonfly, the revolutionary small-car-sized, nuclear-powered rotorcraft that was officially confirmed by NASA in April 2024 to study Saturn’s moon Titan. The decision allows the mission team to complete its designs and begin to build and test the spacecraft and its science instruments.

After launch in 2028 and a roughly six-year interplanetary journey, Dragonfly will fly between dozens of landing sites across Titan’s surface in a search for compounds of prebiotic chemistry that advance our understanding of the chemical origins of life. Sampling areas on Titan where organic materials may have mixed with liquid water at the moon’s surface, this revolutionary mission will achieve critical planetary science and astrobiology objectives while advancing aeronautics and exploration technology.

“The Dragonfly mission is an incredible opportunity to explore an ocean world in a way that we have never done before,” said Dragonfly Principal Investigator Elizabeth “Zibi” Turtle of APL. “The team is dedicated and enthusiastic about accomplishing this unprecedented investigation of the complex carbon chemistry that exists on the surface of Titan and the innovative technology bringing this first-of-its-kind space mission to life.”

The APL team that has designed and will build the rotorcraft lander is part of a larger industry–government team managed by APL. The Lab has also built a large Titan environment chamber that has completed commissioning and is being used to ensure the rotorcraft will survive and thrive under Titan’s surface conditions.

The Dragonfly team will also be watching its ocean-world exploration predecessor — NASA’s Europa Clipper, which launched in 2024 — closely. Europa Clipper is the first mission dedicated to conducting a detailed study of a world that likely harbors a salty ocean with twice as much water as Earth beneath its icy crust. Targeting Jupiter’s icy moon Europa, the mission — built in partnership between APL and NASA’s Jet Propulsion Laboratory — aims to study the moon’s composition, geology and interior to understand whether it harbors the water, chemistry and energy to support life.

Among several contributions to the spacecraft design, test and integration phases of the mission, APL built Europa Clipper’s propulsion module and communications system, and delivered — and will operate — the spacecraft’s plasma instrument, both cameras (including the most powerful camera ever slated for the outer solar system) and portions of the imaging spectrometer.

A signature component of the spacecraft is its massive solar array wings. Managed by APL and designed and engineered by Airbus Netherlands B.V., each solar array measures 13.5 feet (4.1 meters) wide and 46.5 feet (14.2 meters) long. Put end to end, they stretch just shy of the length of a basketball court — the largest arrays NASA has ever developed for a planetary mission.

Innovating at Hypersonic Speed

One of APL’s enduring unique qualities is the breadth and depth of expertise that enables innovative and game-changing contributions across such a vast array of domain spaces. It’s what enables the same kind of expertise that lends itself to protecting spacecraft traversing the universe to be applied to challenges much closer to our home planet, such as hypersonic flight. While traveling faster than five times the speed of sound, hypersonic vehicles encounter some extreme conditions.

In 2017, APL researchers dove into a phenomenon called boundary layer transition — whether the air around the surface of a hypersonic vehicle is laminar (moving in a smooth manner) or turbulent (swirling in circles, and associated with up to eight times the heat transfer). On Sept. 2, the Boundary Layer Transition (BOLT) team launched BOLT-1B, the latest test in this effort, and collected vital data on the physics of airflow at hypersonic speeds.

A joint research project conducted by APL, the Air Force Research Laboratory’s Air Force Office of Scientific Research and the German Aerospace Center, the experimental vehicle blasted off aboard a sounding rocket from the Andøya Space facility in Norway, before traveling over the Norwegian Sea at Mach 7.2 — a speed that would allow it to travel from New York City to Washington, D.C., in less than three minutes.

To collect its data, the experiment (designed and built by APL) was loaded with instruments to take more than 400 measurements from strategically and geometrically determined locations across the vehicle. As planned, the test concluded with the BOLT-1B vehicle impacting the ocean approximately 115 miles (185 kilometers) offshore.

“The data we gathered from the flight experiment will be critical for designing hypersonic vehicles, so we can reduce modeling uncertainties and optimize their performance,” said Brad Wheaton, chief scientist with APL’s Vehicle Design and Technologies Group and the project’s principal investigator.

In a collaboration with the Johns Hopkins Whiting School of Engineering (WSE), APL researchers also studied boundary layer transition as a part of a larger effort to explore the future of air-breathing flight in the upper stratosphere, pushing the boundaries of aviation and defense to new heights.

Flying vehicles higher and faster has strategic and operational advantages for both military and civilian applications, including new intelligence, surveillance, and reconnaissance missions, significantly faster international commercial air travel, and potentially providing launch platforms or staging areas for space missions to the Moon and beyond. But the challenges of stratospheric flight require new approaches to vehicle and systems design.

“Maneuverable, sustained flight at ultrahigh altitudes is still an aspiration,” said Melissa Terlaje, the APL Air and Missile Defense Sector strategist. “Significant changes in air pressure and oxygen density in the upper stratosphere and mesosphere all challenge lift, thrust and drag differently than at conventional flight altitudes.”

Such was the charge of the Between Earth and Space (BEAST) team, an APL–WSE collaboration which focused on three critical areas for future vehicles: lift and maneuverability, combustion stability, and thermal management. Supported by the Johns Hopkins SURPASS program, which fosters innovative, multidisciplinary solutions to real-world problems, investigators explored boundary layer transition control in high-speed, high-altitude flight using computational fluid dynamics techniques developed at WSE. They also researched combustion stability for increased thrust with novel bubbly fuel–air mixtures and used APL’s expertise in additive manufacturing and WSE’s materials synthesis techniques to create new types of thermal management across the vehicle body to improve survivability in the upper stratosphere.

Maneuverable, sustained flight at ultrahigh altitudes is still an aspiration. Significant changes in air pressure and oxygen density in the upper stratosphere and mesosphere all challenge lift, thrust and drag differently than at conventional flight altitudes.

— Melissa Terlaje, APL Air and Missile Defense Sector strategist

BEAST was just the start of efforts at the Lab to fly at extremes. Operationalizing extreme altitudes is a critical challenge that APL is uniquely equipped to solve. APL experts are applying what they learned from BEAST to new initiatives that are pushing into parts of the atmosphere where very few things fly today.

Forging the Future of Alloys With Artificial Intelligence

Operating in extreme environments means finding materials that can withstand intense conditions. To meet this need, APL is leveraging artificial intelligence (AI) to discover materials more quickly and efficiently than ever before.

For example, APL leads one project to harness improvements in AI and machine learning to find materials that can withstand extreme heat as components of a hypersonic vehicle. In another effort, researchers are developing an AI model to discover rare-earth free alloys that have good magnetic properties.

APL is also advancing the development of multi-principal element alloys (MPEAs), materials that can perform well in extreme environments. MPEAs contain multiple elements mixed in roughly equal proportions, offering enhanced strength, corrosion resistance and durability over traditional materials like steel or aluminum.

Researchers are using AI and machine learning to sift through vast combinations of elements and alloy compositions to find the optimal mix. The ability to rapidly design, test and iterate on new materials is particularly crucial for industries that operate systems in unforgiving conditions, such as aerospace, national defense and space exploration.

“As the nation faces pressing security challenges, there are increasing operations in austere environments — and those operations require revolutionary new materials,” said Morgan Trexler, who leads APL’s Science of Extreme and Multifunctional Materials program. “We cannot wait decades to discover materials that meet those needs. By infusing AI throughout the discovery process, we can more quickly and intentionally identify materials for complex, specific applications.”

Making Heliophysics Discoveries

In 2024, engineers at APL completed the integration and testing of the Interstellar Mapping and Acceleration Probe (IMAP), launching in 2025.

Led by Princeton University, IMAP will explore and observe our solar neighborhood, decoding the messages in particles from the Sun and beyond. Like a modern-day celestial cartographer, the mission will map the boundaries of the heliosphere — the electromagnetic bubble surrounding the Sun and planets that is inflated by the solar wind and shields our solar system from cosmic radiation.

IMAP will also investigate and chart the vast range of particles in interplanetary space, helping to determine how charged particles from the Sun are energized and how the solar wind interacts with interstellar space at the solar system’s boundary.

Throughout 2024, IMAP’s suite of 10 instruments — along with the spacecraft’s subsystems and components — were run through a gauntlet of tests on the APL campus. Among those instruments is IMAP-Ultra, a particle imager APL designed and built to help us understand how the heliospheric bubble, created by the Sun, protects the solar system. Ultra does so by accurately measuring the energetic neutral atoms formed when charged particles from the solar wind reach the outer heliosphere and interact with neutral particles in interstellar space.

NASA’s Electrojet Zeeman Imaging Explorer (EZIE), slated to launch in March 2025, is an 18-month mission to image the magnetic fingerprint of the electrical currents flowing in the upper atmosphere that are closely tied to the auroras at Earth’s poles.

EZIE features three cubesats, satellites each the size of a small suitcase, that will travel pole to pole to image these magnetic fingerprints and determine how they connect Earth to the rest of the surrounding geospace.

APL leads and manages the mission for NASA. In August 2024, the EZIE team completed its pre-ship review, with NASA confirming the spacecraft and their support systems are ready to move to their eventual launch site. The Jet Propulsion Laboratory built an instrument called the Microwave Electrojet Magnetogram for each of the three satellites, and Blue Canyon Technologies in Boulder, Colorado, built the cubesats.

Mapping the electrojets will give scientists greater insight into the physics of Earth’s magnetosphere, as well as of other magnetized planets in our universe. The mission will also help scientists create better models for predicting space weather — phenomena from auroras to geomagnetic storms fueled by the Sun.

Enabling Student Science

APL researchers also launched an unprecedented outreach campaign in the form of EZIE-Mag, magnetometer kits that allow teachers, students and science enthusiasts to obtain their own measurements, which will be combined with EZIE’s measurements made from space to assemble a clear picture of this vast electrical current circuit.

Before the EZIE spacecraft’s launch, members of the EZIE team at APL will build and distribute around 700 magnetometer kits to students and teachers across the United States.

“EZIE will not just solve decades-old mysteries about how these currents connect Earth to space, but provide students and citizen scientists with an opportunity to participate in a NASA mission through the EZIE-Mag program,” said APL’s Nelli Mosavi-Hoyer, project manager for EZIE.

Extraordinary Achievements at Earth’s Poles

As material advancements push the boundaries of endurance in Earth’s upper atmosphere, APL researchers are also experimenting in the farthest reaches of the Northern and Southern hemispheres. Scientists and engineers ventured to Antarctica to launch the Galactic/Extragalactic ULDB Spectroscopic Terahertz Observatory (GUSTO), which broke the record for the longest flight time by a heavy-lift, long-duration balloon on Feb. 24, after remaining aloft for 57 days and 7 hours.

Launched near McMurdo Station in Antarctica on Dec. 31, 2023, GUSTO — a collaboration between NASA, the University of Arizona, APL, the Netherlands Institute for Space Research (SRON), the Massachusetts Institute of Technology, the Jet Propulsion Laboratory, the Smithsonian Astrophysical Observatory and others — featured a radio telescope suspended in the air from a balloon the width of a football field when fully inflated.

APL managed and operated the mission for NASA, and Lab researchers designed the gondola carrying GUSTO’s payload, which includes a telescope with cryogenically cooled detectors to measure carbon, oxygen and nitrogen emission lines within the interstellar medium — allowing GUSTO to trace the formation and full life cycle of stars.

A 3D chart for a large part of the Milky Way Galaxy will be constructed based on GUSTO’s measurements of these elements, which are critical for life.

GUSTO’s achievement is the latest success for APL’s balloon programs, which allow scientists to perform critical research in a region just below outer space at lower cost.

At Earth’s other pole, new trade, economic and operational opportunities have emerged as the Arctic melts — along with new challenges that could threaten the U.S. border and the region’s fragile ecosystem.

“To effectively respond to incidents and crises and to enhance our situational awareness, we must grow our presence in the Arctic. However, there are a lot of questions about how to do so, including if and where we should build more infrastructure, based on the stability, location and handling of the extremes of the environment,” said Lauren Ice, an APL national security analyst.

To address those challenges, more than 100 APL researchers are collaborating with organizations across the country to develop technology and knowledge for a sustainable and lasting foothold in the region.

To effectively respond to incidents and crises and to enhance our situational awareness, we must grow our presence in the Arctic. However, there are a lot of questions about how to do so, including if and where we should build more infrastructure, based on the stability, location and handling of the extremes of the environment.

— Lauren Ice, APL national security analyst

Using a combination of materials, modeling, AI and sensing expertise, the researchers are collecting data to better anticipate and understand communication challenges, sea-ice melt and movement, and ecosystem changes as temperatures warm. They’ve developed ecofriendly ice-phobic coatings for ships and equipment inspired by proteins found in Arctic cod, compression-resistant dive suits and tools that could one day capture the jags and features of ice cracks to help personnel navigate the melting environment in vehicles and on foot.

“The data we collect now will create a foundation for studies in arctic regions that will help generations to come,” said David Porter, an oceanographer and chief scientist at APL.

Collaborating and Steering Solutions for Critical Space Challenges

Achieving mighty goals such as defending our planet from asteroids or establishing a long-term presence on the Moon requires collaboration across multiple industries and sectors.

In April, APL hosted a Planetary Defense Interagency Tabletop Exercise, bringing together domestic and international leaders to coordinate and evaluate a global response to a simulated asteroid impact threat to Earth.

Representatives from NASA, the Federal Emergency Management Agency (FEMA), the European Space Agency (ESA), the United Nations and other domestic and international agencies were among the participants.

The exercise walked participants through a hypothetical scenario in which astronomers discover an asteroid with a significant chance of impacting Earth 14 years in the future. Many details about the asteroid, including its size and specific impact location, were unknown. The situation required officials to discuss, coordinate and agree on courses of action, including timelines for potential space missions to gather more information about the asteroid and to possibly prevent its impact.

The exercise built on increasing global efforts to prepare to defend the planet if necessary. In 2022, NASA’s Double Asteroid Redirection Test (DART) mission became the world’s first demonstration of technology for defending Earth against potential asteroid impacts. Built and operated by APL for NASA’s Planetary Defense Coordination Office, the DART spacecraft intentionally collided with the asteroid Dimorphos, which posed no threat to Earth, and changed its motion in space.

“DART’s successful impact was a milestone that truly showed how far technology and the nation’s space program have come,” said APL Space Exploration Sector Head Bobby Braun. “As we look to the future of planetary defense, the DART experience will certainly inform our efforts alongside the coordinated plans we build across the government through these exercises. Bringing together a broad range of critical stakeholders is something we do every day at APL — we were pleased to host this exercise.”

Organizers released a report of the exercise, detailing strengths as well as gaps toward which future investments can be targeted. The report will also provide recommendations for future planetary defense exercises.

“This exercise provided our domestic interagency community, as well as key international partners, with a critical opportunity to work together through a very realistic hypothetical scenario,” said Dipak Srinivasan, formulation area manager for APL’s Space Formulation Mission Area. “Everyone involved gained valuable insights to be better prepared for an asteroid threat.”

To align industry collaborators on a venture closer to Earth, APL leads the Lunar Surface Innovation Consortium (LSIC), an element of NASA’s Lunar Surface Innovation Initiative to advance the development of technologies for sustainable operations on the Moon.

The U.S. is not just going back to the Moon, we’re building the testbed for future planetary exploration, including Mars, and we’re assembling the world’s top experts to make it a reality.

— Jamie Porter, LSIC director at APL

And those advancements are coming fast. At the annual LSIC Spring Meeting at APL, experts from government, academia, nonprofit institutions and the private sector engaged in detailed discussions about the technologies they’d need, and hurdles they’d need to jump, to achieve a sustained presence on the lunar surface. Researchers and engineers offered peeks at the not-so-distant future, showcasing mining robots, mini rovers and satellite models. Aerospace company Venturi Astrolab even demonstrated the mobility of its full-scale FLEX rover on campus roads outside the meeting.

“The U.S. is not just going back to the Moon, we’re building the testbed for future planetary exploration, including Mars, and we’re assembling the world’s top experts to make it a reality,” said LSIC Director Jamie Porter, of APL.

Closely tied to LSIC is APL’s lead role in the Defense Advanced Research Projects Agency (DARPA) Lunar Operating Guidelines for Infrastructure Consortium (LOGIC), which aims to advance the development of consensus-driven, community-supported technical standards for the lunar economy. LOGIC is leveraging the results of DARPA’s LunA-10 study — a groundbreaking look at connecting disparate commercial lunar operating systems over the next decade — to accelerate interoperability standards in lunar infrastructure and interface development.

“LOGIC represents an ambitious and transformative vision for lunar commercial development,” said Daniel Meidenbauer, APL LOGIC project manager. “By bringing together diverse expertise from across the nation and the world to address key technical challenges facing the lunar economy, we can create a sustainable infrastructure that will enable us to not only explore our celestial neighbor, but also use it as a platform for commerce.”

And rounding out APL’s leadership of pivotal space initiatives, in 2024 APL hosted its fifth annual Cislunar Security Conference, where leaders from multiple organizations assembled to discuss new and evolving critical challenges in the cislunar domain — the vast region of space from Earth’s geosynchronous orbit to the surface of the Moon and the five Earth–Moon Lagrange points. The event covered topics including position, navigation and timing; space domain awareness; national security; and supporting technologies to enable cislunar operation. Keynote speakers Jim Free, associate administrator for NASA, and Stefanie Tompkins, director for DARPA, spoke on the peaceful, sustainable exploration and utilization of cislunar space.

New in 2024, in partnership with the Johns Hopkins University Whiting School of Engineering, APL hosted a one-day executive course to demystify the complexities of operating in the cislunar domain, including mission orbits, transfers, proximity operations, formation flying and navigation. This course equipped conference participants with a deeper understanding of the evolving cislunar landscape prior to the conference, enabling more robust discourse of these challenges.

Eyes on the Martian Moons

APL delivered a science instrument to the Japan Aerospace Exploration Agency (JAXA) for integration onto JAXA’s Martian Moons eXploration (MMX) mission spacecraft, which aims to characterize and determine the origin of the moons and deliver an actual sample of Phobos to Earth. In March, NASA handed over its Mars-moon Exploration with GAmma rays and NEutrons (MEGANE) instrument, built by APL in collaboration with Lawrence Livermore National Laboratory in California.

The latest in a long line of APL gamma-ray and neutron spectro­meters, MEGANE (the Japanese word for “eyeglasses”) will characterize neutrons and gamma rays emitted from Phobos, letting MMX “see” the elemental composition of the moon’s surface and helping to determine the likely origin of the moon.