A year ago SpaceX launched its Falcon Heavy rocket for the first time. Millions tuned in as Elon Musk's space company moved to number one on the list of the world's most powerful rockets.

Falcon Heavy's maiden launch was nearly flawless. The only blemish was when one of its three boosters crashed into the ocean, rather than gently coming to a landing on a company barge.

Yet, even after Falcon Heavy succeeded, critics focused on the market for the massive rocket's services. Department of Defense applications of Falcon Heavy were apparent. But even the prospect of lucrative military contracts was not enough to convince some within the space industry that Falcon Heavy would generate solid revenue for SpaceX.

Skeptics pointed to the slowing market for large communication satellites and the need for U.S. Air Force certification to fly national security missions. They said these were two reasons SpaceX would not be able to fill Falcon Heavy's manifest.

With the test flight under its belt, the rocket needed "to get some commercial customers," Dr. Greg Autry told CNBC. Autry is a professor at USC's Marshall School of Business, as well as the director of the Southern California Commercial Spaceflight Initiative.

"The lone test flight was incredible but not enough to prove for someone to put an expensive payload on board," Autry said of Falcon Heavy. "SpaceX needs to prove it's a reliable vehicle."

Orders did arrive in the past year and, even before a second flight, Air Force certification came with them. The manifest for Falcon Heavy has grown to five contracted missions, including three commercial missions. While only one has a known price tag – a $130 million contract to launch the Air Force Space Command-52 satellite – the rocket's manifest is worth somewhere between $500 million and $750 million, given the price range per launch.

That means Falcon Heavy has enough contracts to cover the cost of its development, which was more than $500 million, Musk noted last year, with the all funding coming from inside SpaceX.

Chad Anderson, CEO of Space Angels, which invests in space projects, told CNBC some people in the industry doubted the concept of reusability, or launching, landing and launching again, which has become a trademark for SpaceX. Last year, SpaceX became the first company to launch and land the same orbital rocket three times. That's in part due to the increased power and reliability of the company's evolved Falcon 9 rocket, which Musk said is "capable of at least 100 flights."

And the criticisms of Falcon Heavy are starting to sound familiar. "There's a recurring pattern here," Anderson said, "It's the same tired, old arguments we're seeing applied to Falcon Heavy."

The lack of competitive rockets is also a boon for Falcon Heavy. The only operational rocket that compares is United Launch Alliance's Delta IV Heavy and it's retiring soon. NASA's Space Launch System (or SLS) and Blue Origin's New Glenn are possible new entrants in the market of heavy lift vehicles but neither rocket is expected to launch before 2021. The Ariane 6 rocket is supposed to launch next year but a French auditor published a blistering assessment of the European rocket that found Ariane 6 will not be a competitive or sustainable option.