Early Tuesday morning, four commercial astronauts took to the skies from Cape Canaveral, Florida, aboard a SpaceX Falcon 9 rocket, beginning a historic mission.
Four astronauts — Jared Isaacman, Kidd Poteet, Sarah Gillies, and Anna Menon — will spend five days in a SpaceX Crew Dragon capsule orbiting Earth. But they're not there for a fun cruise: They'll be hard at work conducting a variety of tests and experiments.
One of the most ambitious of these tests is the first commercial spacewalk — or extravehicular activity (EVA) — using SpaceX's newly developed spacesuits, scheduled for 2:23 a.m. ET Thursday. A second opportunity will be Friday at the same time if the spacewalk is delayed for some reason.
Spacewalking is a dangerous endeavor even for professional astronauts, let alone civilians.
“A spacewalk is a risky adventure, but again, we’ve done all the preparation: We’ve done capsule tests, we’ve done suit tests, we’ve done hyperbaric chamber tests, we’ve done all the work to really prepare for this,” said Bill Gerstenmaier, a SpaceX engineer who served as NASA’s chief of human spaceflight until 2020. “We were kind of building on what NASA’s legacy was.”
But spacewalking will not be like what we are used to.
History of spacewalks
On March 18, 1965, Soviet cosmonaut Alexei Leonov exited the Voskhod 2 capsule and performed the first spacewalk. But this things didn't go quite as planned.
After floating in space for about 10 minutes, Leonov returned to the capsule, which had an inflatable airlock. However, he soon realized that his suit had become stiff and bloated; he could not fit through the door. The only thing he could do to reduce the amount of air in the suit was to bleed a little at a time, although this presented the danger of potential oxygen starvation.
He did not report this to officials on the ground, but he managed to carry out his plan and return to the safety of the capsule.
WATCH | Alexei Leonov's First Spacewalk:
The first American spacewalk, on June 3, 1965, was a little different. Ed White was the astronaut who made the attempt. However, instead of an airlock, the entire Gemini IV capsule had to be depressurized, exposing White and fellow astronaut James McDivitt to the vacuum of space.
Today, astronauts on the International Space Station (ISS) wear a bulky spacesuit with a self-contained life support unit that allows them to move around the outside of the 109-meter-long laboratory. To keep from floating away into space, they are tethered to various rails around the station.
The Polaris Dawn crew will follow White's Gemini IV spacewalk. The entire capsule will be depressurized, exposing all four astronauts to the vacuum of space. Isaacman and Gillis will then conduct an expected 15- to 20-minute spacewalk while attached to a short tether.
Under pressure
Of course, space is dangerous. It's not so much that it's trying to kill us, but that our bodies are made for Earth and Earth alone, which is why going into the vacuum of space is so difficult.
For example, the normal air we breathe is 78 percent nitrogen and 21 percent oxygen (with one percent other gases). Astronauts in spacesuits cannot breathe this way for a couple of reasons: one is the risk of low oxygen levels, and the second is difficulty moving due to the pressure difference between the suit and the vacuum of space.
Instead, they breathe pure oxygen, which also helps them avoid depressurization disease.
“When we do spacewalks on the International Space Station, we pre-breathe to reduce the amount of nitrogen in our bodies,” said retired Canadian astronaut Dave Williams, who is not only a doctor himself but also holds the Canadian record for most spacewalks, totaling 17 hours, 43 minutes.
“In some cases, it could happen overnight. In other cases, it could happen in a couple of hours. But the Polaris Dawn crew, all four crew members, will have to go through the same pre-launch training because the entire spacecraft is going to be sent into a vacuum.”
Pre-flight preparation for Polaris Dawn begins on the day of arrival in space and continues until the hatch is opened on the third day of the flight for a spacewalk.
While this is a test, it's not as if the suits haven't been thoroughly tested here on Earth.
“[They] “We’ve been doing a lot of testing over the years … to minimize the risk of bubbles forming in the bloodstream, which happens to people who dive pretty deep and then decide to come up quickly — what divers call the caissons,” said Emmanuel Urquieta, vice chair of the department of aerospace medicine and an associate professor of medicine at the University of Central Florida.
Decompression sickness, or venous gas embolism (VGE), refers to bubbles that can form in the bloodstream of astronauts on spacewalks, for the same reason that divers are at risk. The spacecraft is pressurized to sea level, or about 14.7 pounds per square inch absolute (psia), which is the absolute zero pressure that occurs in a perfect vacuum. During spacewalks, their suits are pressurized well below that, with NASA astronauts are under 4.3 pounds per square inch of pressure.
But what happens if the Polaris Dawn astronauts actually get decompression sickness?
Urquieta said that if someone experiences a mild case of decompression sickness during a dive — like joint pain — the diver is transferred to a pressure chamber, where the pressure is gradually increased and then gradually reduced to sea level. This could theoretically be done on the SpaceX Crew Dragon, where they close the hatch and perform the same task.
“So even if it were a worst-case scenario, there is the ability to treat this case in space,” he said. “Again, all of these things have been thought through [about] over the years and historically with other vehicles.”
Both Urquieta and Williams are confident that the suit's testing will be successful, and that the suit is just the first iteration of future suits that will likely eventually lead to NASA's own life support suit.
For Williams, once an astronaut, always an astronaut: He offers his help.
“If anyone wants to call me,” he said, “I'll be happy to go and evaluate all kinds of suits.”