Two days into their mission, the Polaris Dawn crew are preparing for a highlight of their mission on Thursday, with Jared Isaacman and Sarah Gillis due to step outside Dragon Resilience for the first EVA by commercial astronauts. The spacewalk, which marks another milestone in the development of the commercial space industry, is due to begin at approximately 06:23 UTC.
Polaris Dawn is the first of three planned missions in Jared Isaacman’s Polaris Program. Much like NASA’s Project Gemini in the mid-1960s did for the Apollo program, this aims to build experience and develop techniques and technologies for future commercial missions to the Moon, Mars, and beyond.
The Polaris Dawn mission marks the third flight of SpaceX’s Crew Dragon Resilience, which previously flew the Crew-1 and Inspiriation4 missions — the latter of which was the first fully commercial space mission, also funded and flown by Jared Isaacman.
Having finally lifted off on Tuesday, Polaris Dawn began its mission by flying higher than any human spaceflight since Apollo 17 returned from the Moon in 1972. Resilience was initially placed into a 190-by-1,200-km orbit, completing several revolutions before raising the apogee — the highest point of its trajectory — to 1,400.7 km. In this orbit the spacecraft passed through Earth’s radiation belts, including the South Atlantic Anomaly, allowing the effects on the crew and the Dragon vehicle to be studied.
With the high-altitude portion of the mission complete, Resilience lowered its apogee to about 700 km in preparation for Thursday’s spacewalk. This will be the first time a spacewalk has been carried out during a commercial mission or by a commercial astronaut, with both Isaacman and SpaceX’s Sarah Gillis expected to exit the capsule to test their spacesuits in the vacuum of space. The two other crewmembers, Scott Poteet and Anna Menon, will remain aboard Dragon but will still be exposed to the vacuum, as Dragon lacks an airlock so the whole capsule will be depressurized during this phase of the mission.
Spacewalks, or Extra-Vehicular Activities (EVAs), are an integral part of long-duration space missions, allowing astronauts to inspect and carry out repairs on the exterior of their spacecraft, as well as to explore their destinations once they arrive and in the future to establish bases on the Moon and Mars. The principal objective of Polaris Dawn’s EVA is to evaluate how SpaceX’s spacesuits perform outside of the capsule.
These are the same spacesuits that the crew donned for launch, and will wear again for re-entry. They have been adapted from SpaceX’s standard launch and entry suits with changes including the addition of a new thermal garment to help regulate temperatures; the provision of a heads-up display with pressure, temperature, and humidity data; and the use of new materials and semi-rigid rotator joints to improve mobility.
The Dragon spacecraft itself has also been modified to support the EVA, with the capsule’s life support systems in particular requiring a number of upgrades. Additional oxygen is being carried, which will be supplied to the astronauts’ suits while Resilience is depressurized. A nitrogen repressurization system has also been added to bring the spacecraft back up to pressure once the spacewalk is completed. Additional sensors are being carried, and the spacecraft’s forward hatch has been upgraded including the addition of a motor to help the crew open and close it.
On-orbit preparations for the EVA began almost as soon as Resilience arrived on orbit, with the cabin pressure being slowly decreased to 59.6 kilopascals (8.65 psi) and the proportion of oxygen increased. This facilitates pre-breathing, which helps to ensure there are no nitrogen bubbles in the crew’s bloodstream when the spacecraft is fully depressurized, which could result in decompression sickness.
During the second day of the flight, the astronauts were expected to test their spacesuits inside the spacecraft, including pressurizing them to check that they worked as expected. This informed the final decision to go ahead with the spacewalk.
The hatch of Crew Dragon Resilience, including the Skywalker mobility aid. (Credit: SpaceX)
The final step to prepare for the EVA will see the crew don their suits which will transition to 100% oxygen for the final stage of pre-breathing. With this complete, Dragon will be fully depressurized, and the first spacewalker will open the capsule’s forward hatch. A new structure, which SpaceX has named Skywalker, has been attached around the hatch to provide hand and foot holds to aid movement.
Although two astronauts will be performing this EVA, only one will be outside of the spacecraft at any given time. The first astronaut will exit the spacecraft and perform a series of planned tests on their spacesuit, focusing on mobility. This will gather data to help SpaceX assess the suits’ performance and refine the design for future missions. The second spacewalker will close the hatch after re-entering at the end of their test sequence, and Dragon will then be repressurized.
The spacewalkers will remain tethered to Dragon, with an umbilical providing oxygen rather than the crew carrying this with them. From depressurisation to repressurisation the process is expected to take about two hours.
While this spacewalk marks a significant milestone for commercial spaceflight, it is one of several objectives for the Polaris Dawn mission. In addition to the high-altitude tests completed earlier in the flight, it is also carrying out a number of experiments to study how the crew is affected by being in space and testing optical communications through SpaceX’s Starlink satellites.
Two further Polaris missions are expected to follow. Polaris II will be another Dragon mission, building on experience gained with Polaris Dawn. Its objectives have not yet been made public, although the program did previously engage with NASA about the possibility of using this mission to service and reboost the Hubble Space Telescope. While this seems unlikely to be approved, it does show the ambition of Polaris to take rapid strides forward.
The third Polaris mission, Polaris III, is currently expected to be the first crewed flight of SpaceX’s Starship, currently under development at Starbase in Boca Chica, Texas.
Polaris fills a similar role for SpaceX in the commercial sector that Project Gemini did for NASA during the race to the Moon in the 1960s. Across two uncrewed and 10 crewed missions, Gemini allowed NASA to test and practice operations that would be needed if they were to meet President Kennedy’s goal of landing a man on the moon by the end of the decade. The program included the first U.S. spacewalk, which Ed White made in June 1965 — three months after Soviet cosmonaut Alexei Leonov had become the first human to walk in space.
Gemini also pioneered many techniques that we now take for granted in the course of spaceflight, including the first rendezvous in orbit between two crewed spacecraft and a series of docking tests where the Gemini spacecraft mated with target vehicles based on the Agena rocket stage, whose engines were then used to raise and lower the orbit of the combined vehicle. Gemini also twice set new records for the longest-duration spaceflight, with Gemini VII remaining in orbit for almost two weeks to demonstrate that astronauts could safely remain in space long enough to reach the Moon and return to Earth.
Gemini VII seen in orbit from Gemini VI-A in December 1965 (Credit: NASA)
The Polaris Program will not need to repeat all of these missions. Dragon has already routinely demonstrated its ability to perform rendezvous and docking maneuvers in the course of its missions to the International Space Station — carrying both crew and cargo to the outpost. Likewise, the advent of space stations has pushed the boundaries of long-duration spaceflight far beyond what would be possible with a capsule in solo flight. From 1994 to 1995, Russian cosmonaut Valeri Polyakov completed a 437-day stay aboard the Mir space station.
Despite this, SpaceX’s mission statement of “making human life interplanetary” will bring new challenges and new problems to be solved. Polaris is helping to tackle these in much the same way that Gemini helped pave the way for Apollo to land humans on the moon 55 years ago.
(Lead image: Render of an EVA in progress from Crew Dragon. Credit: Polaris Program)
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