Polaris Dawn set to return home after landmark commercial spaceflight

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After a historic mission, the Polaris Dawn mission, flown by Crew Dragon Resilience with private astronauts, is set to splash down off the Florida coast. Polaris Dawn, which made history with the highest altitude attained by a crewed spacecraft since 1972, and the first commercial spacewalk, is to return to Earth early on Sunday, Sept. 15.

The Crew Dragon will splash down off the Dry Tortugas at approximately 3:36 AM EDT (07:36 UTC) on Sunday. Recovery ship Shannon is in the Gulf, while sister ship Megan has returned to Port Canaveral after going to the station the day before. Shannon will be on site for the recovery of this mission.

Some temporary flight restrictions (TFRs) had been issued for the splashdown. These covered areas off of the coasts of Tallahassee, Daytona Beach, Panama City, Pensacola, and Tampa. Sites off Cape Coral and the Dry Tortugas — known as Tortuga — were also under a TFR in the same time range as the others.

The timings of these TFRs vary, but they all covered the early morning hours before dawn. Tortuga and Cape Coral appear to have been activated as possible splashdown sites for this mission. The Tortuga site is now the target for splashdown.

Polaris Dawn crew on orbit, during an event honoring Folds of Honor. (Credit: Polaris Program)

Resilience’s return to Earth will start with the crew spending the last flight day preparing for the deorbit burn and splashdown. All four crew members will don their flight suits, which were the same suits they wore when they launched and when they conducted their historic EVA.

The deorbit process reaches a critical milestone around the one hour and 20-minute mark before splashdown when a fitting known as “the claw” connecting the Crew Dragon return spacecraft to its trunk is separated. The trunk contains solar panels, thermal control, and avionics system components which the spacecraft uses while in orbit.

A photo showing the “claw” between the trunk and the Crew Dragon crew capsule. (Credit: SpaceX)

This is just the first step in a process to transition Crew Dragon from in-space operations to reentry operations. The protective nose cone, which was extended to expose the hatch used during Polaris Dawn’s spacewalk, will be retracted. This is necessary to help protect the spacecraft from the heat of reentry and to optimize the spacecraft’s aerodynamics to allow it to fly through the atmosphere.

The trunk will be jettisoned five minutes before the deorbit burn. This will expose the heat shield for reentry and lower the mass of the spacecraft so that less fuel needs to be expended for the deorbit burn. The burn will begin around 52 minutes from reentry, using Resilience’s Draco thrusters. This burn will last around 15 minutes.

Artist’s impression of Crew Dragon during atmospheric reentry. (Credit: SpaceX)

After the deorbit burn is complete, the Crew Dragon will coast until it hits the upper atmosphere around 12 minutes before splashdown. Once the spacecraft reenters the atmosphere it will endure temperatures of up to 1,930 degrees Celsius. This heating will cause a temporary loss of communications with Resilience due to ionized air around the spacecraft blocking radio signals.

After Resilience gets through maximum heating, it will approach the landing zone. Drogue chutes will deploy to help slow the spacecraft down until it reaches a safe speed to deploy its four main parachutes. Once these chutes deploy, the Crew Dragon will slow down to a safe touchdown speed before splashing down onto the ocean surface.

Splashdown of Crew Dragon Resilience during the private Inspiration4 mission in September 2021. (Credit: SpaceX)

After splashdown, the recovery crew will check the spacecraft for any leaking hypergolic fuel — used by the Draco thrusters — or other hazards. Once the recovery team clears the spacecraft, it will be brought aboard the recovery vessel Shannon. The crew, mission commander Jared Isaacman, pilot Scott “Kidd” Poteet, mission specialist Sarah Gillis, and medical officer Anna Menon will leave Resilience before being transported to shore aboard a helicopter.

The weather criteria for return to Earth is an important reason why the Polaris Dawn mission was delayed from its originally scheduled late August launch. Though Polaris Dawn launched into the same orbital inclination as the International Space Station, it would not be able to dock with the ISS due to not having the docking adapter installed.

The hatch of Crew Dragon Resilience, including Skywalker. It is installed in place of docking equipment for ISS missions. (Credit: SpaceX)

The consumables aboard the spacecraft limited how long Polaris Dawn could stay in orbit, so there needed to be a good forecast for splashdown a few days ahead of launch. These conditions finally lined up for flight on Sept. 10 and Polaris Dawn launched.

The weather requirements for a Crew Dragon landing are exacting. These include no lightning within 10 miles, waves with no greater than a seven-degree slope, and wind speed no greater than 12 miles per hour. In addition, there needs to be less than a 25 percent chance of rain, and at least one-half mile visibility in the daytime or one mile at night.

Tropical outlook at the end of August 2024. The unsettled weather in the Atlantic and Gulf of Mexico delayed Polaris Dawn’s launch. (Credit: NOAA)

There also cannot be more than four degrees of pitch and roll on the recovery vessel where the helicopter is to operate from, and the helicopter must pass a start and hover test to prove its operational capability. The cloud ceiling must be above 500 feet as well.

During the last week of August and the first week of September, conditions in the Gulf of Mexico and the Atlantic Ocean were conducive to storm development. Mission commander Jared Isaacman noted that winds in particular were a problem when he answered a question about the mission’s launch date on the X social media platform.

The seven splashdown sites originally available to the Crew Dragon before this flight. (Credit: NASA)

There have historically been seven sites available for Crew Dragon splashdown off Florida at present. They are off Pensacola, Panama City, Tallahassee, and Tampa on the Gulf of Mexico side and Jacksonville, Daytona, and Cape North — near Cape Canaveral — on the Atlantic side. A site north of Key West known as Tortuga was added for this mission, as was a site off of Cape Coral, near Naples.

However, Crew Dragon splashdowns will move to the West Coast next year. Large debris of the spacecraft’s trunk section, to be expended upon reentry, has been found to survive entry and could pose a risk to people on the ground in the future. With West Coast Dragon splashdowns, the trunk would reenter over the Pacific and its debris would hit open water instead of potentially a populated area.

A cargo Dragon prepares for splashdown in the Pacific Ocean, bringing thousands of pounds of equipment and experiments home from the Space Station. (Credit: SpaceX)

Marine resources will still be needed in the Atlantic to support launch abort emergencies where Crew Dragon might need to splash down somewhere along the flight path. In the meantime, Crew Dragon Resilience is preparing to reenter the atmosphere to conclude its third mission to space.

(Lead image: Polaris Dawn seeing an orbital sunset. Credit: Polaris Program)

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