Moving at about 28,000 kilometers per hour
through temperatures of up to 3,500 degrees Fahrenheit,
SpaceX's Crew Dragon capsule and the astronauts inside
safely reentered Earth's atmosphere on August 2.
NASA: Welcome back to planet Earth,
and thanks for flying SpaceX.
Narrator: The world nervously
watched the historic launch,
the first from US soil in almost a decade,
on May 30, 2020.
But it's this landing that Elon Musk most feared.
Here's what had to go right
in order to bring Bob Behnken and Doug Hurley home.
There are two main reasons why reentry
is the most dangerous part of the mission:
extreme speed and temperature.
SpaceX and NASA had to think
about these factors in three key ways.
The first pain point was finding
the precise angle for reentry.
Not steep enough, the Crew Dragon would have bounced
right off the atmosphere and back into orbit.
Too sharp or too fast, and the astronauts could have faced
fatal gravitational forces and the spacecraft
could have caused enough drag to break up and disintegrate.
Then, even at the correct angle,
moving at about 25 times the speed of sound
through the atmosphere creates extreme friction,
which produces superheated plasma.
A heat shield has to deflect
and absorb the energy created by the plasma.
At 3,500 degrees, the shield gets hot enough to glow,
but Musk said, due to the Crew Dragon's asymmetric design,
the craft could have over-rotated during reentry
and diverted plasma into launch-escape pods on the side.
If that happened, the ship could have
overheated in some parts
or started wobbling, causing the crew to lose control.
The plasma caused a six-minute communications blackout
between the Crew Dragon and Earth.
NASA: Dragon SpaceX, comm check.
Narrator: So if anything went wrong in that moment,
remote control would have been impossible.
In 2019, auditors listed parachute problems
as a key risk to NASA's commercial crew program.
And the physics turbulence
a space capsule parachute goes through
is one of the most difficult calculations for researchers.
SpaceX and NASA had to design
a completely new system for the Crew Dragon.
After multiple versions and dozens of tests,
the Mark 3 design was approved.
Even so, Musk's worry was that
they might not deploy correctly
or that the system would guide the Crew Dragon
to the wrong splashdown location.
All of these risks were assessed and calculated
"six ways to Sunday," as Musk told Aviation Week,
but they could never be fully done away with.
NASA estimated that there was a one in 276 chance
of this mission being fatal, but both Behnken and Hurley
told us they were comfortable with those odds.
Luckily, that bet paid off.
We can officially call this historic mission a success.
And SpaceX is set to fly the same Crew Dragon
back into space with four astronauts in spring of 2021.