It may only be roughly a 16-minute journey from when the Artemis II crew begin their re-entry into Earth’s atmosphere to hitting the Pacific Ocean, but there are a lot of moving parts to what is widely considered the riskiest phase of the mission. Separating from the service module Before entering the Earth’s atmosphere, the capsule holding the crew has to separate from the European service module, which means all of the solar panels, engines, radiators and even the oxygen and water tanks will be removed. That’s because the module doesn’t have a heat shield. Only the crew capsule has enough protection to withstand the intense heat when blasting through the Earth’s atmosphere. There are 12 thrusters that help orient Orion to make sure it is roughly 120 kilometers above the Earth’s surface. Entering Earth’s atmosphere With the service module left behind, the crew capsule then begins entering the Earth’s atmosphere at approximately 40,000 km/h. As air compresses in front of the capsule, it creates a plasma fireball where temperatures can reach 2,700 C , roughly half the temperature on the surface of the sun. Orion uses an ablative heat shield which works by absorbing the impact of the condensed air collecting in front of it. As it burns, chars and flakes, it carries heat away with the material itself. As the Orion capsule hurtles towards Earth, the plasma also blocks all communications with the crew. Then begins the most dangerous phase. “In terms of what keeps me up at night, my blood pressure will be elevated until they’re under parachutes in the water off the West Coast. There’s no plan B there. That is the thermal protection system. The heat shield has to work,” said NASA Administrator Jared Isaacman in a press conference on Tuesday. As the crew capsule is plummeting through the atmosphere, air continues to pile up in front of it, creating drag and decelerating the spacecraft at four times the force of gravity -- that is why crew members will also feel four times heavier than they do on Earth. Parachute Deployment While Orion is still moving at hundreds of kilometers per hour, it will then begin a precise deployment sequence of 11 parachutes. Three are initially released to remove the cover bay that sits over the main parachutes. Then, at roughly 7,600 meters above the Earth’s surface, two drogue shoots are released to slow and stabilize the crew module, before they’re cut free. Lastly, at nearly 3,000 meters before splashdown, three pilot chutes are released, pulling out the three main parachutes, which then slow the spacecraft down to roughly 30 km/h and allow it to become stable and upright for landing. Splashdown in the Pacific Orion is expected to hit the Pacific Ocean nearly 30 kilometers off the coast of California roughly 16 minutes after it entered Earth’s atmosphere. After it hits the water, flotation devices systems will be deployed to keep the capsule upright while recovery teams, consisting of the U.S. Navy, Airforce and NASA, will move in. Divers will help the astronauts from an inflatable front porch and onto helicopters that will then take them to a recovery ship. Orion is then towed into the recovery ship to be taken to the Kennedy Space Center in Florida. Splashdown location is weather dependent Weather conditions are being closely monitored, since NASA says it requires no heavy rain or thunderstorms within several kilometers of the landing site. Paul Delaney, a university professor emeritus of physics and astronomy at York University, said there has to be relatively calm seas, calm winds, and no major rain showers or lightning. “It’s more likely they’ll adjust the landing zone,” said Delaney in a Thursday interview with CTV Your Morning on what would happen if those conditions are not met. “At the moment, the conditions look pretty good, but there is a system relatively close that they’re keeping an eye on,” added Delaney. “They can adjust their entry point to either be a little short of the primary zone or a little further.” “It would really have to be a terrible situation on the ground to even consider putting them into orbit.”
