On Tuesday afternoon, the company will test fire the engines on its newest rocket at the Kennedy Space Center in Cape Canaveral, Florida, according to news reports. The test was originally scheduled for last Thursday, but was delayed first to Friday, then to Monday, and now to Tuesday for unspecified reasons. Visible vapors around the rocket and launch pad last week indicated the rocket had been fueled up.

SpaceX did not immediately return Fortune‘s request for comment on the planned test and last week’s delays.

According to SpaceX, the Falcon Heavy is the most powerful rocket in operation. It has more than 5 million pounds of thrust, equivalent to 18 747 aircraft. With 27 engines and three cores to get the rocket off the ground, it is capable of carrying more than 140,000 pounds of cargo to low-Earth orbit. The cores are designed to be re-used, making the rocket much more cost effective.

This rocket has been in the works for a while, with its first test flight originally scheduled for 2013. SpaceX and Tesla CEO Elon Musk said the company’s initial hopes for the technology were too high. It’s been trying to manage expectations for its launch since July, when he said he only hoped the test launch wouldn’t cause launch pad damage.

Still, Musk drew attention to the launch with the announcement that the cargo of the initial launch would be his own Tesla Roadster, playing David Bowie’s “Space Oddity” on repeat as it heads towards Mars.