Why is Falcon Heavy different from other SpaceX rockets?

The company’s workhorse is the Falcon 9 rocket, which first launched in 2010. The first stage of the Heavy essentially consists of three Falcon 9 first stages bound together. The second stages of the two rockets are identical.

The additional thrust allows the Heavy to propel 140,000 pounds to low-Earth orbit, nearly three times what the Falcon 9 can lift.

How does this Falcon Heavy differ from the first one?

On the test flight, the two side boosters were older versions reused from earlier flights. (SpaceX’s best innovation to date is landing the booster stage of its rockets and launching it again; traditionally, rockets have been one-use throwaways, with the booster stages dropped into the ocean.)

For this one, the side boosters had never before been used. They were the latest version of the rocket, called “Block Five.” (“Block” is what rocket companies call a major upgrade.) That boosts the thrust and how much the Falcon Heavy can carry.

Why did the second Falcon Heavy flight take so long?

Even though the first Falcon Heavy flight appeared to be nearly flawless, SpaceX probably made adjustments. That, after all, is the reason a rocket company performs a test flight for a new rocket design.

SpaceX also has had a backlog of Falcon 9 missions to fly. It launched 20 Falcon 9 missions in 2018, more than in any previous year, in addition to the one Falcon Heavy launch. The company was also busy at work developing its Crew Dragon capsule for taking NASA astronauts to and from the International Space Station.

The market for the Falcon Heavy is also much smaller than once envisioned. When Mr. Musk first announced the rocket in 2011, he said he expected that there would be a 50/50 mix between the Falcon 9 and the Falcon Heavy. In the years since, improvements have made the Falcon 9 more powerful, and miniaturization of electronics has shrunk the size of many satellites.