Artemis II crew prepare to strap in for descent to Earth after final checks

cynthia II crew prepares for re-entry on endure replete(p) daytime in space

Artemis II splashdown: Why Orion’s re-entry is so high risk

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There are a few ways to watch the crew return to Earth tonight:

Arguably the most dangerous part of the Artemis II mission will be re-entering the Earth's atmosphere at around 32 times the speed of sound — almost 40,000 km/h. That's nearly 10,000 km/h faster than the space shuttles flew upon re-entry.

When a vehicle travelling at this hypersonic speed hits the Earth's atmosphere, air molecules around it are compressed and heated, causing friction so great that it forms a bubble of hot plasma reaching temperatures of 2,760 C that surrounds the craft for many minutes.  

The astronauts will be protected from the extreme heat of re-entry by a heat shield. 

When the Orion returned from its first, unmanned, flight, the heat shield was found to be cracked and broken. But after consultation with engineers, spaceflight officials and outside experts, NASA said it was confident the mission would be safe and the shield design was not changed. 

An intense investigation tested the capsule to see what would happen if even more of the heat shield broke off and found Orion would remain solid.

Once the world's most powerful rocket splashes down into the ocean, it will likely never be seen again. 

The SLS is a disposable rocket — everything is thrown away except for the tiny crew capsule. That's like buying a new car and driving it until it runs out of gas, then crushing it and only keeping the steering wheel. 

If you want to take another drive, you have to buy a new car — and each one costs more than $4 billion US ($5.5 billion CAD).

Tonight's re-entry has been top of mind for the mission pilot for years.

"I've actually been thinking about entry since April 3, 2023, when we got assigned to this mission," Glover said when asked how he was feeling about the return to Earth.

"There's so many more pictures, so many more stories and, gosh, I haven't even begun to process what we've been through. We've still got two more days, and riding a fireball through the atmosphere is profound as well."

This morning we spoke to Canadian astronaut David Saint-Jacques about what it's like to come back to Earth — and what the Artemis II crew will experience tonight, both physically and emotionally.

"Right now they're literally falling back to Earth, they've been falling for four days, accelerating the whole way … and then they'll turn into a fireball as the atmosphere slows them down," said Saint-Jacques, who spent 204 days on the International Space Station in 2019.

The Artemis II crew's capsule will reach speeds of over 38,000 km/h and temperatures of around 2,700 C this evening. But Saint-Jacques said they won't notice the speed until they start to slow down — by which time they're buckled up like a kid in a car seat.

"They're strapped in, all curled up in a fetal position and they've got their back to the Earth … and then someone is braking. So they kind of squish into their seat [due to] the pressure," he said.

"It feels like, suddenly, you get to meet your good friend gravity again."

Before re-entry, the astronauts will finish their final checks, review emergency protocols and secure items in the craft — and take the chance to enjoy the view of Earth one last time, he said. Seeing the planet from space can change a person, Saint-Jacques said.

"The Earth is beautiful, graceful, the only kind of really living thing out there … it rekindles your love for the planet and makes it very clear that we're all Earthlings at the end of the day," he said.

Saint-Jacques said he'll breathe a sigh of relief once the crew is back on the ground.

"These are all my friends up there. So, this is the mission of my buddies … Jeremy's kids once all babysat my kids, our families were intertwined," he said.

NASA just gave us some anticipated speed numbers via flight dynamics, though the figures won’t be official until after the astronauts get home.

It's anticipated the capsule's maximum speed will occur around the same time as the astronauts enter a six-minute communications blackout as they shoot through Earth’s atmosphere — around 7:54 p.m. ET. 

It's predicted at this point they will be travelling at 39,688 km/h, or close to Mach 33. That's just 209 km/h short of the speed record set by Apollo 10 in 1969 after Tom Stafford, John Young and Eugene Cernan returned from their trip around the moon. 

Less than 2½ hours to go until splashdown. The crew has finished their final leak checks on their launch and re-entry suits and will soon strap themselves into their seats inside the capsule.

All four crew members took turns Wednesday testing and evaluating the "orthostatic intolerance garment," which is designed to apply lower-body compression, help them maintain proper blood pressure and circulation and stave off dizziness and fainting as they return to the pull of Earth's gravity. 

"It was important to get this and try this out … so that the crew has an understanding of what it's like to put this on on entry day," Henfling said.

Artemis II splashdown: Why Orion’s re-entry is so high risk

There's only 13 minutes between "entry interface" — when the Orion capsule begins to enter the Earth's atmosphere — to splashdown. But a lot happens in that short period of time.

NASA laid out the key steps to the crew's return to Earth at a news conference on Wednesday. 

About 42 minutes before splashdown, the crew module and the service module will separate. The crew will then conduct one final burn, called the crew module raise burn, and complete a number of roll manoeuvres. 

The Orion will then plunge into the Earth's atmosphere at an altitude of 400,000 feet (122,000 metres) at speeds of about 40,000 km/h. At this point, the capsule will be about nearly 3,200 kilometres away from the landing site — closer to Hawaii than the California coast.

"That's when the fun really begins," Rick Henfling, Artemis II's entry flight director, said on Wednesday.

Twenty-four seconds after the Orion enters Earth's atmosphere, Henfling said, there will be a six-minute communications blackout as hot plasma builds up around the spacecraft, interfering with telemetry transmitters. By the time the crew can contact Houston again, Orion will be at 150,000 feet (45,700 metres) and falling rapidly toward sea level.

Two drag chutes will deploy at about 22,000 feet (6,700 metres) to slow Orion down to about 320 km/h, followed by the three main parachutes at 6,000 feet (1,800 metres). These orange chutes should slow the crew down "to a gentle 20 m.p.h. [32 km/h] splashdown in the Pacific Ocean" off San Diego, Henfling said.

NASA has said those watching from the ground in San Diego likely won't see the spacecraft hurtling across the sky, but that doesn't mean they won't experience anything at all. 

The U.S. Geological Survey is expecting a sonic boom as the Orion breaks into Earth's atmosphere that "could potentially be felt and heard" throughout southern California between 8:00 and 8:15 p.m. ET.

There are a few ways to watch the crew return to Earth tonight:

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