The Psyche spacecraft chassis was delivered to the Jet Propulsion Laboratory in late March 2021.
NASA / JPL-Caltech
Components, including scientific instruments, will be added to the chassis over the next 12 months.
Once completed, the spacecraft will be shipped to Cape Canaveral, Florida for launch with a SpaceX Falcon 9 rocket.
NASA / JPL-Caltech
Artist's impression of the Psyche spaceship at the Psyche asteroid.
SSL / ASU / P. Rubin / NASA / JPL-Caltech
A satellite company called Maxar recently shipped a piece of spacecraft the size of a passenger car to NASA's Jet Propulsion Laboratory in California. This chassis will serve as the backbone for a robotic spaceship exploring a metallic asteroid for the first time. This ambitious mission, named Psyche after the asteroid of the same name that it will explore, is slated to launch next summer with a Falcon 9 rocket.
Once in space, the spaceship will use an innovative propulsion device known as Hall thrusters to reach the asteroid. This will be the first time a Hall-powered spaceship has ventured into space, and without this technology, the Psyche mission would likely not take place – least of all at the cost of less than $ 1 billion.
For David Oh, the large, box-shaped chassis is one of those "full circle moments" in life. More than two decades ago, he was a graduate student at the Massachusetts Institute of Technology on Hall Thruster Technology. He then worked for Space Systems / Loral, which initially transferred the propulsion technology to large commercial satellites and was later taken over by Maxar.
After working on the first launches of commercial Hall-powered satellites, Oh left the private sector in 2003 to go to NASA's Jet Propulsion Laboratory, where he has since worked on a number of missions, including the Curiosity Flight red planet in 2011. Now he serves as technical director for the psyche mission.
"I've been working on electric propulsion for more than two decades," he said in an interview.
And now the Hall thruster technology Oh worked on as a PhD student is going to take NASA to a whole new place, Psyche. No spaceship has ever visited a world like this, which is about 60 percent metal. We really have no idea what it's going to look like.
Chemical propelled motors are great for removing rockets from the surface of the earth when you need a powerful burst of energy to break out of the planet's gravitational well. However, chemical rocket engines are not the most economical machines in the world because they use propellants. And once a spaceship is in space, there are more economical means of moving around.
One of these is solar electric propulsion, which uses solar panels to extract energy from the sun, which in turn ionizes and accelerates a gas – typically xenon – to create a thrust. It's not a huge boost. It's actually extremely easy. Each of the engines of the Psyche mission achieve roughly the same force as two or three quarters in the palm of your hand. But because they are so economical in fuel consumption, solar electric engines don't burn for a few minutes. They burn for months and produce a steady acceleration.
NASA has been experimenting with this technology for some time. The space agency first tested electric propulsion technology on its Deep Space 1 mission, launched in 1998, and later on the Dawn 2007 mission, which visited Vesta and Ceres in the asteroid belt.
These spaceships used ion thrusters. In contrast, Hall thrusters use a simpler design with a magnetic field to restrict the flow of propellant. These engines 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, e.g. B. those supplying DirecTV use Hall thrusters for deployment.
But now they are being used for a space mission for the first time. NASA and Maxar believe the technology is ready, but it has yet to be tested in a new environment.
"Going beyond Earth orbit is always a big deal," said Robert Curbeam, a former astronaut who is senior vice president at Maxar. "If you move further away from the sun, you will generate less power from the solar panels. The radiation environment will be different. And the question arises as to whether we can keep these engines pulsing for that long."
If NASA had tried to develop the chemical-powered Psyche mission, it would have used about five times as much fuel. That mass would have made the psyche even bigger than the Cassini probe that NASA used to explore the Saturn system from 2004 to 2017, Oh said. The Cassini mission cost approximately $ 4 billion, a budget that NASA reserves only for the highest priority "flagship" missions. NASA only flies one or two of these in a decade, and the scientists behind Psyche, led by Lindy Elkins-Tanton of Arizona State University, knew they wouldn't get that designation.
The use of Hall thruster-based technology enabled the mission's scientists and engineers to design a smaller and more affordable spaceship. Crucially, NASA was able to purchase a spacecraft chassis from Maxar that was largely made from off-the-shelf commercial technology. Had NASA and the Jet Propulsion Laboratory developed this technology themselves, it would have cost billions of dollars and would have taken years longer.
Each of the Hall thrusters on Psyche generates three times as much thrust as the ion thrusters on the Dawn spaceship and can handle twice as much power. In this way, after a 3.5-year journey, the spaceship can reach the psyche asteroid in the main belt in January 2026.
Psyche is still a big spaceship with big solar panels to collect sunshine in the asteroid belt.
Instead of doing a large burn as the starship approaches Psyche – as is common with a chemically powered vehicle – it will drink xenon fuel and return to orbit around the asteroid. Over time, the spaceship is getting closer and closer, always trying to find a stable orbit around the asteroid, which has a strange shape and an uneven gravity field. Fuel-saving engines help with this.
By the end of this 21 month period, the spaceship will finally be approximately 100 km from the surface of the psyche, which is approximately 220 km in diameter. In this lowest orbit, Psyche will use a spectrometer to map the various elements that make up Psyche and answer the question of what exactly metallic asteroids are made of.
Oh said he was dying to know if Psyche could be at the core of something that could have become a planet in the early days of our solar system, but ultimately didn't. If so, we could learn a lot more about the core of our own world, the earth. In addition, the results of this mission will better educate scientists and entrepreneurs about the potential riches of metallic asteroids, which could be critical to human habitation in space decades from now.
Listing image from NASA