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The mission that will crash into an asteroid so we will hopefully never have to live inside a scene from Deep Impact is now heading out on its collision course.
NASA’s DART (Double Asteroid Redirection Test) mission took off at 1:20 a.m. and is now en route to the asteroid Didymos and its orbiting moonlet. Though neither of these asteroids is threatening to Earth, the moonlet Dimorphos is thought to be the more likely size of an asteroid that could be a hazard. DART will smash its face into Dimorphos to shift its orbit around Didymos enough so it can be measured by telescopes back on Earth.
The spacecraft is being propelled there (obviously on a one-way journey) by Redwire, the same company that created a sci-fi method of using lunar regolith to 3D-print just about anything astronauts need right on the Moon. Redwire collaborated with NASA and the Johns Hopkins University Applied Physics Lab (APL) to design the solar arrays DART will get all its power from, as well as the sensors and electronics processing unit that will guide it to its target.
“Designing instruments for DART was a long and involved process,” scientist Geoff Carter, who was involved in bringing this mission to life, told SYFY WIRE. “We had to determine how much power the mission will need at the end of its life, so we had to take into account degradation factors like radiation, atomic oxygen, and micrometeoroid debris.”
DART’s ROSA (roll-out solar arrays) arrays first proved they would hold up in space in an ISS experiment, and its sun sensor system was inherited from the Parker Solar Probe, with the same Digital Sun Sensor Heads. Its processor was upgraded to handle five of those heads instead of the two Parker is equipped with. The size of the array depended on everything Carter mentioned, but especially the amount of power required for the mission, factoring in some extra just in case. Something too far from Earth for human repair has to have backup.
There was another thing that would ultimately determine the dimensions of the spacecraft—its stowed size. It had to be compact enough to fit in the fairing of the rocket that would launch it out of the atmosphere. After both the stowed and unfurled size for DART were figured out, it was put through a series of rigorous analyses and tests to be sure it will survive both the launch and the flight to Didymos. Whether stowed or deployed, it needed to be strong enough, stiff enough and flexible enough to withstand a brutal launch and exposure to outer space.
“I feel that our biggest challenge during this build was performing the environmental testing,” Carter said. “We had to get all the hardware, mechanisms and solar cells to extreme mission critical temperature limits and prove they would function correctly both stowed and deployed.”
Test launching also meant simulating the intense vibrations and heat the spacecraft would experience on its rocket multiple times, but it always passed. DART will then be free to spread its 28-foot solar arrays once in space. Flexible Array Concentrator Technology (FACT) modules make up these arrays. These next-gen solar cells are highly efficient and tricked out with reflectors to capture more solar energy. The reflectors will unfold with the wings and, because of their unique shape, be able to send more sunlight to the cells for maximum power.
What about space GPS? This is where DART's sun sensor and star trackers come in, keeping one proverbial eye on the sun and watching out for certain stars with another, so it will know where it is in space. It also has an autonomous SMART Nav system created by scientists at NASA’s Jet Propulsion Lab (JPL) and the Johns Hopkins APL, which will kick in when the spacecraft has 4 hours to go until impact. That is also when its DRACO camera will switch on to locate Didymos and Dimorphos. It should be able to see Dimorphos an hour before its first and final impact.
The ROSA tech used on DART won’t stop there. Carter looks forward to powering future missions with those next-gen solar arrays.
"We will continue to use the same tech on other current and future missions like Ovzon and PPE (NASA’s Power and Propulsion Element for lunar orbit),” he said. “The ISS ROSA arrays that were installed this year used all the same tech as well. They were very successful. We are building 4 more ISS ROSA arrays for delivery.”
Planetary defense is about to be a thing. DART will travel 6.8 million miles and reach the binary asteroid system almost a year from now, and when it does, we can only hope Krispy Kreme releases special donuts again.