What to know before SpaceX attempts to launch Falcon Heavy – Elon Musk’s most powerful rocket

SpaceX plans to make its most ambitious launch to date on Tuesday afternoon and send its Falcon Heavy rocket beyond Earth's atmosphere.

If its launch is successful, Falcon Heavy would become the most powerful rocket in use today — for a fraction of the cost of any comparable rocket ever built. Standing more than 21 stories tall, Falcon Heavy is a behemoth of engineering and will fly unmanned.

Such a complex machine has many people in the space industry anxious about whether the rocket will even get off the ground in one piece. SpaceX CEO Elon Musk has noted previously that failure is a possibility, saying there is a "lot that can go wrong" during a first attempt.

Here's what you need to know as SpaceX prepares to make history.

"This is, in many ways, the most significant launch since the first shuttle launch nearly four decades ago," prominent space investor Dylan Taylor told CNBC.

Delays have plagued the development of the Falcon Heavy, a rocket that some in the space industry thought may never see launch day. Musk unveiled the rocket in 2011, promising the inaugural launch would happen as early as 2013.

Now, seven years and many testing delays later, Falcon Heavy is in place at NASA's Kennedy Space Center in Cape Canaveral, Florida, with SpaceX aiming to launch from pad 39A at 1:30 p.m. ET on Tuesday. SpaceX will have until 4 p.m. to attempt a launch, or the mission will be pushed to the following day.

The rocket completed a static fire test on Jan. 24, when Falcon Heavy successfully ignited its engines while strapped to the launch pad. That test was one of the final benchmarks clearing the rocket for launch.

SpaceX built Falcon Heavy out of three of the company's Falcon 9 rockets — a system that has now completed dozens of successful launches over the last few years. The three cores stand side by side to create a 27-engine colossus. Musk has said the central core needed "to be buffed up a lot" but the Falcon 9 cores on each side "use most of the same airframe."

At liftoff Falcon Heavy will create a combined 5 million pounds of thrust — or the equivalent of about 18 Boeing 747 airplanes at takeoff. Musk has called it the "most powerful rocket in the world by a factor of two," and its payload is estimated to be nearly three times that of the former space shuttles, as well as the currently operating Delta IV Heavy and Ariane 5 ES rockets.

Falcon Heavy is "guaranteed to be exciting, one way or another," Musk said in a tweet.

Musk's space company operates differently than any other by recovering the largest part of its Falcon 9 rockets — the first stage. After pushing the upper stage pieces beyond the Earth's atmosphere, the Falcon 9's first stage rotates and returns to land upright on either a concrete pad or one of its autonomous drone ships.

SpaceX plans to use that same technology for Falcon Heavy and make the rocket largely reusable.

"If things go perfectly, all three rocket booster cores will come back and land," Musk tweeted.

The two side boosters will break away first, returning to land at Cape Canaveral in what Musk has called "synchronized aerobatics." The central booster will land a few minutes later on a SpaceX drone ship off the Florida coast.

Musk is even considering modifying the typically expendable upper stage for return as well. The upper stage gives the payload a final push into orbit, but Musk says he wants to bring it back to give Falcon Heavy "full reusability."

"Odds of success low, but maybe worth a shot," Musk tweeted.

Although the Falcon Heavy was built using the first stages of three used Falcon 9 rockets, which cost around $62 million each, SpaceX says the Falcon Heavy pricing starts at $90 million per launch. That's a fraction of the cost of any existing heavy rocket competitor, such as United Launch Alliance's Delta IV Heavy rocket which costs upward of $400 million per launch.

"Falcon Heavy has the potential to launch astronauts — not only into orbit, but to deep space — flying onboard a truly commercial rocket for the first time ever. This is a crucial milestone for the industry," Taylor said.

NASA is currently building a rocket called the Space Launch System that would be more powerful than Falcon Heavy and capable of lifting about twice as much into orbit. But that giant remains several years from its inaugural launch, and NASA's development costs continue to skyrocket. Most recently, NASA estimated that an SLS launch would cost at least $1 billion — or 10 times that of Falcon Heavy.

For the demonstration flight Falcon Heavy will not carry a commercial payload or even the large block of concrete typical of these test flights. Instead, Musk decided to put his cherry red Tesla Roadster on top of the rocket. Musk, who is also the CEO of Tesla, said the car "will be in deep space for a billion years or so if it doesn't blow up on ascent."

Musk explained the unusual payload further when he was asked by a follower on Twitter.

"I love the thought of a car drifting apparently endlessly through space and perhaps being discovered by an alien race millions of years in the future," Musk tweeted in response.

Watch SpaceX attempt to launch Falcon Heavy live on CNBC.com on Tuesday.