Deng Qingming, a Chinese taikonaut and native of Jiangxi province in East China, has served as a backup space crew member for 23 years. He continues to stand ready at his post, available to join a mission at any time, state broadcaster CCTV reported on Monday.

Deng, aged 55, has never been to space. He was a backup crew member for the Shenzhou-9, Shenzhou-10 and Shenzhou-11 missions.

Of China's first group of 14 trainees for the space program, he was among the six who never made it onto the crew. Five of his peers retired in 2014 without a space flight, making Deng the last man standing, with feet firmly on ground.

"Being backup doesn't mean you don't need to work. I must watch closely in the control center and offer all I know about the mission and the spacecraft in case of emergency," Deng said during an interview. "Only when the crew returns to Earth will my mission be complete."

"Be it a crew or backup, it is our job," Chen Quan, one of Deng's retired peers, told Deng during his retirement ceremony. "Don't give up!"

Deng never forgot those words. No matter how difficult the road to space flight is, he never once thought of giving up. At the end of every mission, he would quickly clear his mind of distractions and welcome new challenges with a positive attitude.

In 2013, Deng discovered a tiny kidney stone. While this is not a condition of immediate concern under normal circumstances, it is different for astronauts, who must maintain a rigorous standard of personal health.

Deng underwent two surgeries, the first unsuccessful. After suffering from hematuria for almost 2 months with a tube placed inside his kidney, the stone was finally removed, reigniting his dream.

When training for Shenzhou XI, scheduled to be launched in 2016, Deng along with crew member Chen Dong were confined in a spacecraft simulator no bigger than 10 square meters for 33 days. They had no showers, ate space food exclusively and endured loud noise and piercing light as they tried to sleep.

On the day of the announcement, however, he was not selected.

"They trained as hard as we did, and they are as good as we are. They just didn't have the opportunity," said Jing Haipeng, who has flown on three missions -- Shenzhou VII, Shenzhou IX and Shenzhou XI.

"They spent their best years preparing and waiting. They have lived up to their oath they took when joining up. They are heroes of our country, too!" Jing said.

"The success of the mission comes before my personal wishes," said Deng, who to this day still firmly believes he has a chance at a mission and works as hard as any of his teammates.

Deng's passion has inspired his daughter Deng Manqi, who now works for ground control in Beijing.

"My father is the most hardworking, most selfless person I've ever encountered. My dear dad, you will always be the greatest hero in my eyes," Manqi said in a letter to her father. "Our life and dreams will go on. It's my privilege to work with you."

Deng Qingming, along with Li Qinglong, Wu Jie, Chen Quan, Zhao Chuandong and Pan Zhanchun, have dedicated over two decades of their life in regular training to ensure they would be ready at a moment's notice if the country called upon them, knowing their chances of taking part in a mission diminished every day as they aged.

Many have since retired from active services and been transferred to support posts at the Astronaut Center of China.

However, those unsung heroes have no regrets, demonstrating absolute dedication to the solemn pledge they made over 20 years ago.