American engineers at Bell Labs unveiled the first photovoltaic solar cell in 1954. Four years later, National Aeronautics and Space Administration (NASA) launched solar panels into space.
Today, solar panels power the James Webb Space Telescope, which offered the world the most detailed look into the most remote reaches of the universe to date.
NASA launched the Webb Space Telescope on Christmas Day 2021. The telescope uses less power than one might think. In fact, only one kilowatt, equivalent to the power used in microwaving your lunch, is needed to power the device. NASA said Webb will stay energy efficient more than 1 million miles from Earth, reliably powered by photovoltaics.
A 20-foot fold-out solar array is attached to the main observatory of the craft. It will act as the ‘powerhouse’ for the telescope, supplying energy to all its scientific instruments, communications, and propulsion systems. The system is sized at 2 kW to account for the degradation that will occur over time due to the harsh conditions of space.
The array consists of five panels that are connected by hinges for folding into the launch vehicle, the Ariane 5 rocket. The telescope’s onboard battery was designed to only last a few hours, so the unfolding and activation of the array was considered one of the most critical early steps of the telescope’s voyage. A video of the deployment of the fold-out array can be viewed below.
Solar in space
The James Webb telescope is not the only NASA project that relies on photovoltaics to power its systems. Last June, Astronauts Shane Kimbrough of NASA and Thomas Pesquet of the European Space Agency (ESA) completed their spacewalk upgrade of the international space station, installing the iROSA roll-out solar arrays.
It cost about $100 million to install the six arrays. The arrays are expected to add more than 120kW in capacity, which will increase the station’s power generation by 20% to 30%. The solar panels that were replaced were designed for a 15-year service life, but had been continually operating since December 2000. Although they were functioning well, the older arrays were showing signs of degradation, as expected.
Last December, NASA announced it is testing solar-powered electric propulsion systems for asteroid defense. The Double Asteroid Redirection Test (DART) mission will employ roll-out solar arrays and a 6.9 kW gridded ion electric propulsion system to redirect Earthbound asteroids by smashing the small craft into the asteroid.
The craft is designed to propel itself at about 250 miles per hour, guided by an onboard camera and autonomous navigation software, directly into the path of the asteroid. The DART test will make contact with the Didymos system’s moonlet that is headed into orbit in September 2022.
NASA is also using two large cross-shaped PV arrays to power its Psyche mission, which will bring a craft 1.5 billion miles away from Earth to the asteroid Psyche. The mission is to explore a large, metal-rich asteroid with the remote-operated craft.
The Psyche solar array s 37.1 feet long and 24 feet wide on each side when fully deployed. The two cross-shaped arrays fold out from the craft, and represent the largest solar array deployed by the Jet Propulsion Laboratory, said NASA. So large, in fact, that the entire craft could not be unfolded during the test at Arizona State University’s lab in Tempe. ASU has partnered with NASA on this mission, which will observe the suspected unusually high amount of metals in the thickest band of the asteroid.
On Earth, the solar array can generate about 21 kW of electricity, but far away from the sun alongside Psyche, they will only produce 2 kW, about the same energy demand as a hair dryer. Despite this low amount of energy, it will be sufficient to power the planned three-and-a-half-year journey to the asteroid, and the two years of orbiting and observation of the body.
“Even in the beginning, when we were first designing the mission in 2012, we were talking about solar electric propulsion as part of the plan. Without it, we wouldn’t have the Psyche mission,” said Arizona State University’s Lindy Elkins-Tanton, who, as principal investigator, leads the mission. “And it’s become part of the character of the mission. It takes a specialized team to calculate trajectories and orbits using solar electric propulsion.”
The launch is planned for this August, and the Psyche spacecraft may make first contact with the Psyche asteroid in 2026.
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