Day and night, warplanes take off from the USS Eisenhower for Iraq or Syria. But below deck on the vast aircraft carrier, the fight against the Islamic State group (IS) feels a world away.

Beneath the roar of fighter jets soaring into the sky some 5,000 people, including 1,000 women, provide everything from a dentist's clinic to the daily newspaper to ensure the 200 pilots on board are in top form for their missions.

A host of specialists take care of aircraft maintenance, weapon preparation and the nuclear reactors that power the warship.

But in the labyrinthine corridors, where the air is muggy with fuel fumes and sweat, young sailors run a bustling city.

Some barely out of their teens, they work in the huge kitchens, chapel, desalination plant, medical centre -- and hair salon.

For roughly seven months they labour seven days a week with little time off and rarely a chance to see the light of day.

Come nighttime, they share huge barracks where only small blue curtains around each bunk bed offer a semblance of privacy.

Andrew Garcia, who joined the navy to travel and learn a skill, is the ship's radiologist and spends his time examining injuries from hands trapped in the vessel's heavy doors or tumbles down the steep and narrow staircases between decks.

He shrugs off a question on how it feels to be part of the battle against IS, saying he is "just providing the help needed on board".

The 26-year-old, who carries out up to 30 X-rays a day, said he enlisted "to see other things," quipping: "I'm happy even though all I see is mostly water".

In the waste treatment room, beads of sweat cling to 36-year-old NCO Jamalli Hill. He pledged in 2004 to serve 20 years both for the experience and to save up the money he needs to open his own air conditioning business.

In the meantime, along with 16 underlings who work eight-hour shifts, he spends his time crushing or incinerating garbage in temperatures well over 30 degrees Celsius (86 degrees Fahrenheit) and set to rise further when the carrier reaches the Gulf.

- 'I keep them happy' -

The mammoth vessel regurgitates 1.2 tonnes of plastic per day, which is melted down into huge slabs to be processed on land, as well as 1.8 tonnes of metal which is finely ground up. Food scraps and paper are also ground up and discharged into the sea.

"It's a dirty job but a necessary one to keep the boat clean and sanitary," Hill says.

As for Inherent Resolve, the current operation against IS, it passes him by.

"I'm not sure what (the pilots) do when they fly, but if I take care of my end and they take care of their end, it all comes together," he says.

It's a philosophy shared by hazel-eyed Christine Smith, 25, who signed up for five years in 2013 because she loved to swim, though here she spends her days behind the counter of the onboard Starbucks.

Her minuscule coffee kingdom sits in a corner of the main dining hall, two decks below sea level but not far enough down to escape the roar of engines at each arrival or departure flight.

"Obviously they don't tell us what we are doing. But I'm sure we're accomplishing something," she said, adding that she takes pride in her job. "I keep them awake. People come here, exhausted, and I make them happy."

Minutes later, however, the voice of Captain Paul Spedero, commanding officer of the Eisenhower, resounds throughout the boat on loud speakers.

"We conducted a hundred missions last week, with several very effective strikes in Iraq and Syria," he announces, before praising the "sailor of the day" and bringing news to warm the hearts of the crew, fed up with eating frozen food.

A provisions ship is on its way, and salads and fresh fruit will be on the menu "in the next few days".