Ars Technica had the opportunity to tour NASA’s Jet Propulsion Laboratory in California this week, dressing up for a clean space sneak peek at the Psyche spacecraft, which is now nearing completion. This ambitious mission, named after the self-proclaimed asteroid it will explore, is to be launched in August on a Falcon Heavy rocket. Scientists hope that learning more about this unusual asteroid will advance our understanding of planet formation and the earliest days of our solar system.
Discovered in March 1852 by the Italian astronomer Annibale de Gasparis, 16 Psyche is an M-type asteroid (meaning it has a high metallic content) orbiting the Sun in the main asteroid belt, with an unusual potato-like shape. The long-standing preferred hypothesis is that Psyche is the bare metallic core of a protoplanet (planetesimal) from the earliest days of our solar system, with the crust and mantle removed by a collision (or multiple collisions) with other objects. In recent years, researchers have concluded that the mass and density estimates do not agree with a completely metallic residual core. Rather, it is more likely a complex mixture of metals and silicates.
Alternatively, the asteroid could once have been a mother body for a particular class of rocky iron meteorites, one that broke up and re-accredited to a mixture of metal and silicate. Or maybe it’s an object like 1 Ceres, a dwarf planet in the asteroid belt between Mars and Jupiter’s orbit – except 16 Psyche may have experienced a period of iron volcanism while it cooled, leaving highly enriched metals in these volcanic centers.
Scientists have long suspected that metallic nuclei lurk deep inside terrestrial planets like Earth. But these nuclei are buried too far under rocky mantles and crusts for scientists to figure out. As the only metallic nucleus-like body discovered, Psyche provides the perfect opportunity to shed light on how the rocky planets of our solar system (Earth, Mercury, Venus and Mars) may have been formed. NASA approved the Psyche mission in 2017 and intended to send a spacecraft to orbit the asteroid and collect important data about its characteristics.
“Our understanding of what Psyche can be has not changed much over the last few years,” Linda Elkins-Tanton of Arizona State University, chief investigator of the Psyche mission, told Ars. “It must have a large metal content, but we never really knew how much. It could be part of a metal core on a tiny planet from early in the solar system, or it could be something that never melted and was formed. A core, but there is metal mixed in, like pebbles with the rock. We do not really know until we get there. “
Several instruments will be aboard the Psyche spacecraft to collect the valuable scientific data. There is a multispectral imager that is capable of producing images in sufficiently high resolution for scientists to see the difference between the asteroid’s metallic and silicate (mineral) constituents. The job of mapping the asteroid’s composition and identifying all the elements falls to a gamma ray and neutron spectrometer. There is also a magnetometer that will measure and map any remnants of a magnetic field. Finally, a microwave radio telecommunication system will also be able to measure the asteroid’s gravitational field and get clues about its internal structure.
The chassis, designed by a satellite company called Maxar Technologies, was delivered in April last year. It is roughly the size of a van and was built primarily of commercial, off-the-shelf technology. “Once in space, the spacecraft will use an innovative means of propulsion, known as Hall thrusters, to reach the asteroid,” Ars Senior Space Editor Eric Berger wrote last year. “This will be the first time a spacecraft has ventured into deep space using Hall thrusters, and without this technology the Psyche mission would probably not take place – certainly not at its cost of just under $ 1 billion. ” Here’s a little more from Berger about this innovative approach:
Engines powered by chemical propulsion are great for getting rockets off the earth’s surface when you need a powerful burst of energy to break out of the planet’s gravitational well. But chemical rocket engines are not the most fuel efficient machines in the world as they suck fuel. And once a spacecraft is in space, there are more fuel-efficient ways to move around. NASA has experimented with [solar electric propulsion] technology for a while. The space agency first tested electric propulsion technology in its Deep Space 1 mission, launched in 1998, and later in the Dawn mission in 2007, which visited Vesta and Ceres in the asteroid belt.
These spacecraft used ion thrusters. Hall thrusters, on the other hand, use a simpler design with a magnetic field to limit the flow of propellant. These thrusters were invented in the Soviet Union and later adapted for commercial purposes by Maxar and other companies. Many of the largest communications satellites in geostationary orbit today, such as those providing DirecTV, use Hall thrusters for station teams.
The use of Hall thruster-based technology enabled mission scientists and engineers to design a smaller and more affordable spacecraft. Each of the Hall thrusters on the Psyche will generate three times as much pressure as the ion thrusters on the Dawn spacecraft and can handle twice as much power. This will allow the spacecraft to reach the Psyche asteroid, located in the main belt, in January 2026 after a 3.5-year journey.
The Psyche team tested the two solar panels in March, attaching the arrays to the spacecraft’s body and unfolding them lengthwise before storing the panels until launch in August. The five-panel, cross-shaped solar panels are the largest installed at JPL, measuring 800 square feet (75 square meters). They are specially designed to operate in low light, far away from the sun.