Polaris Dawn astronauts reach record high orbit above Earth

Four private astronauts aboard an ambitious space mission led by a billionaire entrepreneur traveled farther from Earth on Tuesday than any other human being in more than half a century.

Two of them, Sarah Gillis and Anna Menon, have now gone farther from the planet than any other women.

The mission, named Polaris Dawn, lifted off through a break of favorable weather before sunrise Tuesday. The flight had been grounded for nearly two weeks by unsettled weather in and around Florida.

The astronauts, flying an elliptical path around Earth in a SpaceX Crew Dragon capsule, looped outward as far out as 755 miles above the planet's surface. The mission's orbits were carefully planned to reduce the hit of radiation the crew would absorb, and to minimize the chances of being struck by tiny bits of rock crisscrossing the solar system.

The journey Tuesday was only a small fraction of the nearly quarter-million miles that NASA's Apollo astronauts traveled to the moon. But after the last mission going there in 1972, humanity has stayed close to our planet, not venturing beyond orbits a few hundred miles up.

The Polaris Dawn mission, led by Jared Isaacman, founder of the payment services company Shift4, is a collaboration with SpaceX, the rocket company founded by Elon Musk. It is the first of three missions designed to spur technological advances needed for Musk's ambition to eventually send people to Mars.

That includes the mission's most daring moment, scheduled for Thursday: a spacewalk.

On Tuesday after 8 p.m. Eastern time, the spacecraft performed a maneuver to add some bragging rights.

The thrusters on the Crew Dragon spacecraft fired for about 8 minutes to push the farthest point of the spacecraft's orbit outward by another 125 miles or so. Polaris Dawn was now flying higher than the 853-mile altitude that NASA astronauts Pete Conrad and Richard Gordon reached during the Gemini XI mission.

That had remained the record distance for astronauts on a mission that did not head to the moon.

In addition to Isaacman, the crew consists of Scott Poteet, a retired U.S. Air Force lieutenant colonel and pilot who is a longtime friend of Isaacman's, and two SpaceX employees: Menon, a lead space operations engineer, and Gillis, an engineer who oversees astronaut training.

After reaching the high orbit, another thruster firing will drop the spacecraft to a lower orbit and the crew will prepare for the spacewalk. It is scheduled for Thursday, the third day of the mission, although a time has not yet been announced.

Preparations for the spacewalk began almost as soon as the astronauts reached orbit, albeit imperceptibly. The atmospheric pressure within the Crew Dragon capsule -- initially 14.5 pounds per square inch, the same as the surface of Earth -- will gradually be lowered to 8.65 psi. That helps to remove nitrogen from the bloodstream of the astronauts and lower the possibility of decompression sickness, or "the bends," similar to what happens to divers who return too quickly to the surface.

The four crew members will put on their spacesuits, and all of the air will be let out of the capsule. The hatch will then be opened and the inside of the spacecraft will become part of the vacuum of outer space.

Only two people -- Isaacman and Gillis -- are to leave the capsule to do the walk.

The main goal of the spacewalk is to test the spacesuits, which SpaceX developed for this flight. The spacesuits are an evolution of those worn on earlier SpaceX missions, adding capabilities like protection against micrometeoroids and temperature controls for the astronauts.

Poteet and Menon will remain inside the capsule, keeping an eye on the displays and managing the umbilical cords that provide air, power and other life-support needs to the astronauts.

After Isaacman and Gillis return inside and close the hatch, the inside of the capsule will be repressurized.

The entire endeavor is expected to take about two hours.

Before and after the spacewalk, the crew will conduct about 40 experiments, including obtaining MRIs of the astronauts' brains and trying to take X-ray images without an X-ray machine by using the natural showers of radiation that stream through outer space.

The crew spent about 3 1/2 hours on those research activities Tuesday, according to an update posted to the mission's account on the social platform X in the evening. That included testing of communications with the ground using SpaceX's Starlink system.

The mission is also raising money for St Jude Children's Research Hospital in Memphis, Tennessee.