You can't use Starliner spacesuits in a SpaceX capsule: These images show why

The two astronauts who flew a balky Boeing Starliner capsule to the International Space Station in June will come home in February aboard a different spacecraft – and they’ll be wearing different spacesuits.

Astronauts Sunita "Suni" Williams and Barry “Butch” Wilmore arrived at the space station June 6 aboard the Starliner, which developed helium leaks and thruster problems but was able to dock safely.

Citing safety concerns, NASA announced on Aug. 24 that the two astronauts would stay aboard the station until February and return in a SpaceX Dragon capsule. The Dragon will launch Sept. 24. The Starliner was brought down uncrewed on Sept. 7.

The Starliner and SpaceX capsules are not alike in design and require specially made spacesuits to operate them. Those differences are intentional , NASA has said.

How are Starliner, SpaceX suits different?

“From a suit standpoint, they’re really not interchangeable,” Joel Montalbano, deputy associate administrator of NASA’s Space Operations Mission Directorate, said on a media conference call Aug. 14.

“You can’t have a Boeing suit in a SpaceX, or a SpaceX suit in a Boeing vehicle. So that would not be the plan,” Montalbano said in response to a question about modifying suits for transfer flights.

Astronauts wear what’s called IVA – for Intra-Vehicular Activity – spacesuits for a spacecraft launch, flight and reentry. They’re worn to protect astronauts in case of an emergency, such as a loss of cabin pressure or temperature changes.

Those suits are different from EVA – for Extra-Vehicular Activity – spacesuits that offer a much higher level of protection. They’re designed to be worn during spacewalks or on the surface of celestial bodies.

Why are the two spacesuits so different?

It starts with the spacecraft.

"Suits for different providers are not designed to be compatible outside of their own spacecraft, as each suit design must match its respective system," NASA told USA TODAY.

The Boeing Starliner and the SpaceX Dragon were developed under NASA's Commercial Crew program . That agreement gives NASA "the ability to purchase astronaut transportation from Boeing and SpaceX as a service on a fixed-price contract." It also lets the space agency focus on building spacecraft for deep-space missions, NASA says.

NASA wanted " two very different spacecraft , with different procedures and teams to support them," space.com reported.

"This has really been our goal all along, to have two dissimilar systems , Starliner and Dragon," said Steve Stich, program manager for NASA's Commercial Crew Program, in a news conference about the Boeing Starliner on March 22.

Under Commercial Crew, NASA allows companies to design and build components without line-by-line oversight. This lets companies innovate, as long as they meet NASA's broad requirements and safety standards , the Economic Times reported.

"The requirements were written to give companies maximum flexibility to design their best systems to meet the needs of their spacecraft while still meeting NASA’s needs for crew safety and related criteria," NASA says.

Boeing and SpaceX have different designs for their spacecraft . The respective IVA spacesuits needed to operate the craft are specially tailored with exclusively different fittings, including restraints, life-support connections and communications. Other differences include audio and cooling connection ports, helmet styles and materials, NASA said.

That's why astronauts in Starliner suits can't simply board a SpaceX craft and receive the same protection as their SpaceX-suited companions. NASA will send SpaceX spacesuits to Williams and Wilmore.

Different systems can provide extra safety

Though it may appear contradictory, having different systems in space can provide extra margins of safety.

Most systems on crewed and uncrewed NASA spacecraft are redundant . "In the event of a device failure, there is a backup system to compensate ," the space agency says.

But as more nations start to explore space and more spacecraft are launched, ordinary redundancy may not be enough. Instead, dissimilar redundancy can be used. The difference is like this:

◾ Redundancy is two of the same systems performing the same function in the same way.

◾ Dissimilar redundancy is two independent systems performing the same task in two different ways. If one system fails, the other can be used, and it's less likely it will fail like the system it's replacing.

"We've seen the importance of having this dissimilar redundancy," Stich said at the news conference. "It's always tough to fly into space. Having that second transportation system is hugely important to us."

Source: USA TODAY Network reporting and research; NASA; JPL; space.com; Reuters; futurism.com

This article originally appeared on USA TODAY: You can't use Starliner spacesuits in a SpaceX capsule: These images show why