WASHINGTON (Army News Service) -- Retired Army colonel and astronaut Timothy Kopra discussed his experiences on the International Space Station on Tuesday, Sept. 13, during a Facebook Live hosted by ABC News.

Joining him for the broadcast from the "Moving Beyond Earth" exhibit at the Smithsonian National Air and Space Museum, was Secretary of the Army Eric Fanning, who served as moderator during the discussion, taking questions from an ABC News studio audience and Facebook.

Kopra returned from his second mission on the International Space Station earlier this year, on June 18.

SPACE FOOD VS. MRES

One of the most challenging issues with space travel is how to get sufficient amounts of food and water into space for the astronauts to consume during often lengthy journeys. Unsurprisingly, the topic generated a number of questions from the live stream audience.

Processed and dehydrated food in space is well balanced and healthy, Kopra said, but it "clearly would be healthier if we could grow our own."

During his own space missions, Kopra said, they opted to grow inedible flowers, but on previous space missions that he had not taken part in, astronauts had grown lettuce in the space station. He told Fanning the astronauts reported that lettuce grown in space tasted pretty good.

Asked how astronaut food compared to Army food, specifically "meals, ready-to-eat," or MREs, Kopra said both are OK. He had consumed MREs for five months during Operation Desert Storm. An MRE, he said, wasn't "necessarily your favorite, but it was good."

The differences between dining on Earth and in space go beyond the food itself, Kopra said. In space, astronauts must be very careful when eating dinner in zero gravity, because things can float off and "make a big mess" in the space station. One of the joys of coming back to Earth, he said, was not having to worry about that.

Everything needed for life on the space station, including water, is brought from Earth, he said. With no way to procure more water, the space station's atmosphere is recycled to produce water. Even urine and sweat are recycled and purified for drinking.

KEEPING IN TOUCH

Kopra made it clear that his family was the thing he missed most, emphasizing that NASA did a remarkable job of connecting him with his loved ones.

"NASA does a great job of keeping family in touch," he said. "They have an Internet protocol telephone so you can call your family, and there's a video teleconferences once a week with the family."

Asked about what his family thinks of him being in space, he replied, "They think it's cool but they're nonplused. It's business as usual for them," since he has been in the astronaut program since 2000.

He added that he has two children; a son who is a cadet at the U.S. Military Academy, West Point, New York, and daughter who is attending Princeton University.

MISSING GRAVITY

Asked what he missed about Earth during his time in space, Kopra made it clear that he missed his family the most, but gravity was a close second. Working in zero gravity is a real challenge, he said, because everything must be done so meticulously.

"Not having to worry about that level of detail [now] is really a blessing," he said. "So I'm glad to be back."

Returning to Earth gravity after both missions was also hard, he admitted.

"Your body adapts to space," he said. "It loves zero gravity and doesn't like 1-G when you get back, so the first day is very rough. After two weeks, strength and balance return, and recovery comes quickly."

Kopra said he also missed the fresh smells of Earth.

"When we landed in Kazakhstan and opened the hatch, the smell of all that grass was almost overpowering," he said.

INTERCONNECTED

"How are sunsets different in space?" asked Fanning.

The views from space can leave you with a sense of how interconnected everything is, Kopra said, and the views of phenomena like the rising and setting sun and the coral reefs in the Bahamas can be awe-inspiring.

"You see ships going through the Suez and Panama Canals, you see the contrails of planes, you see the roads of different cities connecting each other," he said.

"Even more dramatic is seeing how black it is beyond our planet, so it really makes you recognize that we're alone," he said.

ON BECOMING AN ASTRONAUT

It takes a lot of hard work to become to make the space program, but joining the Army doesn't hurt. So far, around 20 or so Soldiers have become astronauts. Kopra recommended that young people who are interested in becoming astronauts focus on excelling in subjects like take math, science and engineering.

When Kopra returned to Earth from his last mission, his replacement to command the International Space Station was another Soldier, Jeffrey Williams, who happened to set a U.S. record for the most cumulative days in space, 534. He returned just last week, beating Astronaut Scott Kelly's record.