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As SpaceX engineers put together the first model of the company’s new Falcon Heavy rocket, officials have not ruled out flying a paying customer’s satellite aboard the maiden flight of the humongous launcher scheduled later this year, the company’s president told Spaceflight Now.

The long-awaited Falcon Heavy rocket could blast off on its first flight as soon as November from launch pad 39A at NASA’s Kennedy Space Center in Florida, returning the storied Apollo- and shuttle-era launch complex to service for the first time since the last space shuttle mission took off in 2011.

The destination and passenger for the Falcon Heavy’s first flight remains undecided, said Gwynne Shotwell, SpaceX’s president and chief operating officer.

“There have been a number of customers interested in flying on that (mission),” Shotwell said in an interview with Spaceflight Now. “We’re trying to balance, does it make sense for this to just be our mission, so we own it completely?”

SpaceX officials have previously said the first launch of the Falcon Heavy will be strictly a test flight, but Shotwell said the company’s growing customer base has signaled a desire to fly a satellite on the mission.

She said SpaceX will make the first Falcon Heavy launch “useful” by proving its capabilities to future customers, such as heaving a hefty payload to geostationary transfer orbit, the targeted drop-off orbit for communications satellites heading for stations 22,300 miles (nearly 36,000 kilometers) over the equator.

“Regardless of whether we fly a customer or a purely demonstration mission, we’ll make that mission useful, whether it’s to demonstrate something for a GTO (geostationary transfer orbit) capability for our commercial customers, or whether it’s to demonstrate some requirement for national security space,” Shotwell said.

Some national security satellites that could fly on Falcon Heavy rockets in the future need boutique services not yet demonstrated by SpaceX. For example, top secret spacecraft designed to eavesdrop on communications must be directly inserted into a circular geostationary orbit 22,300 miles up, bypassing the egg-shaped lower-altitude transfer orbit used by commercial satellites.

The Delta 4-Heavy rocket built by rival United Launch Alliance currently is the only U.S. launcher capable of delivering those satellites to orbit, along with massive National Reconnaissance Office spy satellites fitted with telescopes and cameras to look down on Earth.

SpaceX has delayed Falcon Heavy rocket’s debut several times, pushing its maiden flight back from an original target in 2013 until late this year. The company also switched the Falcon Heavy’s first launch site from Vandenberg Air Force Base, California, to pad 39A at Kennedy.

At least one customer has bolted to rival Arianespace in the wake of the Falcon Heavy delays.

Broadband Internet provider ViaSat switched one of its heavier 14,000-pound (6,400-kilogram) satellites from the Falcon Heavy to the Ariane 5 rocket earlier this year, but it committed to flying a future spacecraft on the Falcon Heavy once the rocket is operational.

The Falcon Heavy is made by combining three of SpaceX’s Falcon 9 first stage rocket boosters to generate three times the Falcon 9’s liftoff thrust with 27 Merlin 1D engines. A standard Falcon 9 second stage, powered by a single Merlin 1D engine, will fire multiple times to put Falcon Heavy payloads into orbit.

SpaceX ordered the latest Falcon Heavy delay in the wake of a Falcon 9 launch failure last year. The company sidelined work on the triple-body rocket to focus engineers on recovering from the failure, and finishing development of an upgraded version of the Falcon 9 with higher-thrust engines and a modified, super-chilled liquid propellant mix.

Shotwell said one of the booster cores destined to fly on the first Falcon Heavy launch is already under construction at SpaceX’s headquarters in Hawthorne, California. Once complete, the 15-story-tall boosters will go to SpaceX’s test site in McGregor, Texas, for qualification testing.

“I think all three are built this summer,” she said. “They should get through Texas testing, and they should be at the launch site in the fall timeframe at 39A.”

The launch preparations in Florida will culminate with a hold-down firing of all 27 first stage engines, the first time SpaceX will analyze how the engines operate in unison, according to Shotwell.

Pad 39A will be the base for Falcon Heavy operations at Cape Canaveral. There are no plans to convert SpaceX’s nearby Complex 40 launch facility, the Falcon 9’s current launch pad, for the larger three-core booster, Shotwell said.

“Right now, I actually don’t see a need to fly Falcon Heavy from (pad) 40,” she said.

The Falcon Heavy’s three kerosene-fueled boosters will generate more than 5.1 million pounds of thrust at sea level, and the rocket stages mounted side by side will give the 229-foot-tall (70-meter) rocket a span of 40 feet (12.2 meters).

“There’s quite a high pucker factor about Falcon Heavy,” said Elon Musk, SpaceX’s billionaire founder and CEO, in a press conference after the company’s last launch April 8.

“Maybe we should have named it the Falcon 27,” he joked. “We thought maybe that people might balk at that.”

SpaceX estimates the Falcon Heavy can carry 48,940 pounds (22,200 kilograms) to geostationary transfer orbit, the destination that will likely bring the company the most revenue. That is more than ULA’s Delta 4-Heavy and Europe’s Ariane 5, the rockets currently hauling the world’s heaviest satellites to such an orbit.

That figure assumes SpaceX throws away the Falcon Heavy’s two side-mounted boosters and central core stage. For most Falcon Heavy flights, SpaceX intends to steer the boosters back to landing pads near the launch site, while the core stage will arc toward an ocean-going landing platform hundreds of miles downrange in the sea.

Those maneuvers require SpaceX hold a fuel reserve, reducing the mass the rocket can carry into orbit.

Recovering the Falcon Heavy’s first stage boosters for potential reuse carries a performance penalty.

Setting aside propellant for the landing maneuvers cuts the Falcon Heavy’s lift capacity to geostationary transfer orbit to about 17,637 pounds (8,000 kilograms), less than offered by Europe’s existing Ariane 5 and planned Ariane 6 rockets, SpaceX’s rivals in the commercial market.

The Falcon Heavy’s actual performance figures can only be confirmed after a flight, but Musk said on Twitter this weekend that another thrust upgrade to the Merlin 1D engine planned for introduction on the Falcon 9 later this year will improve SpaceX’s lift capacity.

The updated figures published on SpaceX’s website reflect the anticipated improvement.

Ariane’s performance to geostationary transfer orbit is skewed higher by the location of it’s launch site near the equator in French Guiana, meaning communications payloads end up closer to their operational orbits after their deployment from a rocket’s upper stage.

SpaceX’s updated pricing and performance chart shows a Falcon Heavy rocket lofting up to 8 metric tons to geostationary transfer orbit sells for $90 million. The performance figure assumes SpaceX recovers the boosters, but the price does not factor in reuse.

Arianespace intends to sell the most powerful variant of the next-generation Ariane 6 rocket — the Ariane 64 with four solid rocket boosters — for 90 million euros, or about $103 million, a price to be typically split between two customers per mission once the new launcher enters service in 2020.

ULA hopes to sell the base version of its new Vulcan rocket, set for a maiden mission by the end of 2019, for less than $100 million.

Both the Ariane 6 and Vulcan rockets will be fully expendable at first, but ULA is working on a concept to retrieve the Vulcan’s first stage engines by helicopter for refurbishment and reuse some time in the 2020s.

The first flight of the Falcon Heavy is highly anticipated by commercial satellite operators, scientists and space exploration enthusiasts. It is also important for SpaceX’s bottom line and corporate mission, giving the company access to all of the lucrative military and commercial launch markets and making interplanetary flights possible.

“We’ll do something useful with it,” Shotwell said. “I’m just not sure we’re going to fly a payload yet or not, but there has been some interest.”

SpaceX aims to launch an uncrewed “Red Dragon” capsule to Mars aboard a Falcon Heavy rocket as soon as May 2018.

The first Falcon Heavy flight “is going to be an important mission for showing that we can do the biggest satellites in the world, and then some,” Musk said April 8. “If it reaches orbit, it’ll be the biggest rocket to reach orbit, by thrust, since the space shuttle and Saturn 5, and it’ll be the biggest rocket operating today until SLS is active,” he said, referring to NASA’s Space Launch System.

Falcon Heavy’s challenges are not lost on Musk.

The last rocket to fly with so many engines firing simultaneously was Russia’s doomed N1 moon rocket, the Soviet-era answer to NASA’s Saturn 5, which flew four times and never made it out of the atmosphere.

“There are a lot of engines to work simultaneously, and you have three times as many separation events,” Musk said. “It’s a lot trickier of a proposition than Falcon 9, but the payload capabilities are amazing, and it’s got a lot of potential, particularly for doing the heavy high-altitude geostationary satellites that currently can only be flown by Ariane, if it’s a really heavy satellite.”

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Follow Stephen Clark on Twitter: @StephenClark1.