Space six crew, dragon capsule and the astronauts inside safely reentered Earth's atmosphere on August 2nd.

Welcome back to planet Earth.

Thanks for flying space.

Six.

The world nervously watched the historic launch, the first from US soil in almost a decade on May 30th 2020.

But it's this landing that Elon Musk most feared.

Here's what had to go right in order to bring Bob Benk in and Doug Hurley home.

There are two main reasons why reentry is the most dangerous part of the mission.

Extreme speed and temperature.

Space six 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 to 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 3500 degrees, the shield gets hot enough to glow.

But Musk said, due to the crew dragons 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 Dragon Space six com check.

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.

Space six and NASA had to design a completely new system for the crew dragon.

After multiple versions and dozens of tests, the Mark three 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 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 Banken 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 Space six is set to fly the same crew dragon back into space with four astronauts in spring of 2021.