Simulation of spacewalks underwater is a normal practice among astronauts, but NASA’s Extreme Environment Mission Operations (NEEMO) 18 mission team does more than pretend they are on an asteroid away from Earth this time around.

In a nine-day exploration program that began on July 21, NEEMO 18 astronauts will simulate communications with people on Earth while in deep-space operations to remote celestial bodies such as Mars, expecting a communication delay of 10 minutes with Mission Control as opposed to seconds with International Space Station.

The astronauts discussed their activities with the press via live satellite interview on July 23.

"We have to take this time delay into account in the operations concept and even the design of those spacewalks," said astronaut Thomas Pesquet of the European Space Agency (ESA).

The NEEMO 18 mission is commanded by astronaut Akihiko Hoshide from the Japan Aerospace Exploration Agency and supported by crewmembers-astronauts Mark Vande Hei and Jeanette Epps of NASA, and ESA’s Pesquet.

They live at the Aquarius Reef Base laboratory that is 62 feet beneath the Atlantic Ocean’s surface. The laboratory is an undersea research habitat of the Florida International University and is around six miles off the shore of Key Largo in Florida.

The NEEMO 18 mission has its crewmembers testing the training techniques and technologies for use on board the International Space Station and long-term missions.

"We'll be testing out those tools if we did go to an asteroid," Epps said.

For instance, Hoshide and Epps conducted a simulated spacewalk the second day underwater, testing tools and procedures they may make use of in an exploration to distant celestial bodies. Epps revealed having communication challenges with the activity, saying she has to understand exactly what her team wants her to do and she has to show them, too, what she’s seeing exactly.

Malfunctions also come with the territory, according to the other astronauts.

"Thomas and I were supposed to spend the entire time doing experiments, while Aki and Jeannette were doing the spacewalk, but because of the communications problems, I had to abort my science," Vande Hei said.

Technicians who have a broad understanding, experience and knowledge in working at undersea laboratories accompanied the astronauts at NEEMO 18 mission.

"We just do the mission but without their help we can’t do anything,” said Hoshide of the technicians behind the scenes.

NASA’s NEEMO 18 mission will also conduct studies on habitability, behavioral health and performance and human health issues.