Despite facing a setback in early September, Elon Musk's SpaceX isn't scrapping its plans to kickoff manned missions to the International Space Station and beyond.

Yet the private spaceflight company is confronting another issue: a NASA advisory panel has questioned SpaceX's unorthodox fueling process, raising strong warnings on potential spacecraft hazards in the future.

Unconventional Fueling Process

Once its manned mission plans are set into motion, SpaceX will lift off passengers between Earth and the International Space Station aboard the Crew Dragon spacecraft.

However, unlike typical procedures, the company will fuel the Crew Dragon while passengers are inside the vehicle, according to The Wall Street Journal.

Indeed, SpaceX sets itself apart from its rivals in the "innovative" way it fuels its rockets. The company uses a supercooled substance — a chilled liquid oxygen — to allow more fuel in the tank and carry more weight into orbit.

Because of this unconventional method, the spacecraft must be fueled a few minutes before launch so that the supercooled substance does not warm up. This means that future astronauts would have to be inside the vehicle prior to fueling.

"It's a deviation from the norm," says Dr. John Logsdon, founder of the Space Policy Institute at The George Washington University. "[T]hat's bound to raise concerns."

On Nov. 4, NASA released a letter from Dec. 9, 2015 in which the International Space Station Advisory Committee raised the fueling process issue and requested details from NASA's officials.

The letter, which was signed by Lt. Gen. Thomas Stafford, mentions that fueling a rocket with passengers aboard "is contrary to booster safety criteria that has been in place for 50 years."

Analysts say the panel's concerns could delay the launch of the manned Crew Dragon spacecraft, which was expected to lift off in 2017.

SpaceX's Answer

A spokesperson from SpaceX has told NASA that the company designed a reliable launch and fueling process that reduces "the duration and number of personnel exposed" to the dangers of launching a rocket.

Furthermore, despite criticisms, SpaceX confirmed that it will continue its work with the space agency to show that controls are in place for operations and the verifications match the requirements imposed by NASA.

Currently, the space agency pays Russia $71 million per seat to use the Soyuz spacecraft to ferry astronauts to the space station.

Meanwhile, two months after SpaceX's tragic Falcon 9 rocket incident, a rigorous review process has pinpointed the problem that likely caused the explosion: a helium tank failure during fueling procedures.