The next space superpower?

China entered the space race late but it's now a force to be reckoned with. In a world exclusive, CNN sits down with three of the country's top astronauts and takes you inside its secretive space program.

Inside Space City

If you stumbled into Space City, you probably wouldn't realize what it was.

The sprawling complex in the north west of Beijing shares the same nondescript character of government compounds throughout China.

But look closer. Guard posts over here; military sentries checking IDs over there.

This is no ordinary facility. Space City is home to the Chinese government's most ambitious and expensive mega-project ever. They've dubbed it "Project 921," the manned-space program.

And foreign journalists are almost never let in.

After more than a year of phone calls and faxes, here we are, inside the simulation room of the astronaut training center.

The astronauts stride into the room according to rank: Nie Haisheng, Zhang Xiaoguang and Wang Yaping.

They're three of China's best-known astronauts and the crew of the 2013 Shenzhou-10 mission, China's longest manned spaceflight yet.

They're roughly the same height and build in their blue jumpsuits and black military boots.

That's no accident. Chinese astronauts are all People's Liberation Army pilots and officers, they have university degrees, they are Communist Party members. And they need to be around the same height and under a certain weight.

You don't need to be superhuman to be an astronaut, says Commander Nie.

"We are just ordinary people," he says, "But, yes, certain aspects make us more suitable to fly space missions."

China's space program was first announced in the early 1970s, but the chaos of the Cultural Revolution stopped it in its tracks.

The program accelerated again in the early 1990s and space administrators picked two classes of astronauts in 1998 and 2010.

All of the crew of the 15-day Shenzhou-10 mission was passed over for missions at least once.

"When I wasn't selected for a mission, there was nothing I could do about it, so I just kept looking forward," says Zhang.

Zhang is the self-described joker of the group, able to lighten the mood during high-pressure situations. Still, he says he had to live through years of disappointments.

"I trained in this simulator for 15 years and I was in space for 15 days. So literally a day in space was a result of a year of training on the ground."

Perhaps the most famous of the group is Wang Yaping. She conducted a live space lecture for 60 million students across China during the mission.

"I remember, I watched the launch of the first Chinese astronaut into space with my fellow pilots," says Wang, who flew a transport plane for the PLA.

"I saw the fireball come out of the rocket and a thought just popped into my head: 'The first Chinese man just flew into space. When will the first female astronaut from China get there?'"

After years of training, you would think that it is all about the mission. But what happens when the space lectures and experiments are over?

"We really enjoyed the zero gravity situation in our spare time," says Wang. "It allowed us to practice tai chi upside down, it allowed us to float around like fish."

Race to the stars

China's space program started late and is only now passing milestones the U.S. and Russia clocked years ago.

But, with the backing of the highest echelons of the Chinese Communist Party, it's going into space at a time when other world powers have scaled back on space exploration because of budget restraints or shifting priorities.

U.S. space technology is still "hands down the best in the world," says Joan Johnson-Freese, a professor at the U.S. Naval War College, but she says the U.S. lacks the political will to fund an ambitious manned spaceflight program, China's is the pride of the nation.

"It would cost the US $140 billion for a true moon and Mars exploration mission but sticker shock would kill it instantly," she says.

"In terms of perception, America has already ceded its leadership in exploration to China."

Inside Space City, Commander Nie -- who leads the manned space mission -- is more diplomatic.

"The United States and Russia started their programs early. They are the pioneers," he says.

"Our space development is not because of some space competition or trying to overtake anyone."

But the modern race to the stars is not just about money, it's driven by technological advances and cooperation.

The International Space Station (ISS) houses a veritable United Nations in space with 15 countries contributing including the U.S., Russia and Japan.

But not China.

China's 21 astronauts are locked out of the ISS, largely because of pressure from U.S. legislators.

In 2011, Congress banned NASA from working bilaterally with anyone from the Chinese space program on national security concerns.

But a recent exhaustive report for the U.S.-China Economic and Security Review Commission says China's improving space capability "has negative sum consequences for U.S. military security."

"China is viewed as a foe, it is viewed as a government that seeks to take our intellectual property, national secrets and treasure and thus Congress is not willing to partner with them," says CNN space and aviation analyst Miles O'Brien.

"I think it is ultimately a mistake."

The Chinese government says its space program is peaceful and already cooperates with other nations.

The crew of the Shenzhou-10 seem keen to work with NASA.

"As an astronaut, I have a very strong desire to fly space missions with astronauts from other countries. And I look forward to the opportunity go to the International Space Station," says Nie.

He says foreign astronauts are welcome to visit China's own space station once it is launched.

The Chinese expect to finish their space station by 2022 -- around the time the International Space Station runs out of funding, potentially leaving China as the only country with a permanent presence in space.

"They are on a slow steady campaign. I think in the end, tortoise versus hare style, they will probably win," says O'Brien.

'Long March' into space

On October 15 2003, when China became the third nation to put a man into orbit, it wanted its entry to this elite club of space powers broadcast live to the world.

In the event, China lost its nerve and cut the feed. It needn't have worried -- the launch went off without a hitch.

A Long March 2F rocket carrying Chinese astronaut Yang Liwei in the cabin of the Shenzhou-5 spacecraft soared into the atmosphere.

The next morning, his acorn-shaped capsule landed with a thud on the grasslands of Inner Mongolia.

Yang's 21-hour space flight transformed him into an instant hero for millions of Chinese and made the world take China's long-held space ambitions seriously for the first time.

Since then, Chinese astronauts have walked in space, launched an orbital space lab and sent a lunar probe to the moon in what is arguably the boldest space program in the world.

Commander Nie says Chinese people have yearned to fly into space since ancient times, giving China's accomplishments a "bigger and deeper meaning."

"We have many beautiful legends about this dream," he says.

Chinese folklore tells of Chang'e, a young fairy who flew to the moon, and Wan Hu, who attempted to blast off 500 years ago by sitting on a bamboo chair rigged with two kites and 47 rockets.

As 2015 unfolds, China is building a heavy-lift rocket, planning a second robotic mission to the moon and constructing a 60-ton space station.

But its path to the stars has not been hitch free.

China has so far avoided fatal accidents like the Challenger and Columbia disasters that killed 14 U.S. astronauts, but in 2007, it shot down one of its weather satellites 530 miles above the earth.

The strike, which resulted in tens of thousands of pieces of debris, has forced the ISS to maneuver several times to avoid collisions -- a scenario that played out to dramatic effect in the Oscar-winning movie "Gravity."

China's heavy lift Long March 5 rocket, which it needs to launch the space station, has been subject to delays, and a new spaceport on the island of Hainan has yet to go into operation.

These delays could potentially hamper its ambitions as other nations try to match or surpass China's accomplishments -- in what some observers are calling an Asian space race.

China's current space program doesn't commit to it, but many believe a manned mission to the moon is on the table, and after India successfully orbited Mars in 2013, China may also have the Red Planet in its sights.

"They don't rush, they are very cautious but China is in this for the long term," says Johnson-Freese, at the U.S. Naval War College.

Over the moon

In December 2013, the Chang'e-3 spacecraft landed on the moon and released a gold-colored, six-wheeled, lunar buggy named "Jade Rabbit" for a three-month mission to study the moon's crust for resources.

While it made China only the third nation to soft land on the moon after the U.S. and former Soviet Union, the mission was not entirely successful.

The plucky explorer suffered from technical malfunctions but it captured the hearts of millions of Chinese, who followed the rover's ups and downs on its own social media account.

It also drew the attention of security experts, who say the country's lunar exploration program could mean a future of Chinese dominance over the moon's resources.

These include water (probably) and Helium 3 -- a clean-burning fuel that could potentially offer an alternative to nuclear power.

The substance, which accumulates on the surface of the moon, has been used as a justification for lunar exploration by both the U.S. and China, says researcher Kevin Pollpeter at the University of California -- San Diego, although such technology is decades away if possible at all.

When asked if China is preparing to put a man on the moon, Commander Nie laughs and won't be drawn on whether this is the ultimate goal of its space program.

For now, the focus, he says, is on launching the Tianggong-2, an experimental lab, and preparatory work for the space station.

But many space analysts think China is capable of pulling off such a feat.

The next step in its lunar exploration program is a robotic mission, which will land on the moon to collect samples and take them back to Earth. It's expected to take place in 2017.

If successful, it would serve as a proof of concept for a manned mission, as well as deepen China's knowledge of lunar science.

"China is following the Apollo playbook," says Johnson-Freese at the U.S. Naval College -- in reference to the U.S. manned spaceflight program that put the first man on the moon.

"It wants a high-prestige achievement that allows the Chinese government to say to its people 'Look, this is what the Communist Party has done for you.'"