After being grounded for six months, Elon Musk’s SpaceX is poised for a dramatic return tonight, launching—and hoping to land—its most powerful rocket yet, at Cape Canaveral in Florida. Slated for 8:33 p.m. ET, the launch will mark SpaceX’s first mission since a June mishap in which a Falcon 9 rocket exploded in flight while ferrying supplies to the International Space Station.
Never one to take the less-ambitious path, the SpaceX will also use the milestone flight to further push the envelope. A series of engine upgrades also makes the Falcon 9 launch the most powerful rocket the company has ever launched. The mission will also test a modified second-stage engine that will eventually allow the Falcon 9 to carry heavier payloads into higher orbits.
But—barring unforeseen calamity—the climax will come several minutes after liftoff, when the company attempts to land the rocket’s first stage on a launch pad at Cape Canaveral. If successful, the effort would mark both the first successful landing of a potentially reusable rocket stage for SpaceX, as well as the company’s first landing on dry land. (SpaceX’s Two previous attempts to land a rocket stage on a floating barge at sea both failed.)
A successful night for SpaceX would also tilt momentum back in its favor, away from surprise rival Blue Origin. Backed by Amazon founder Jeff Bezos, the future space tourism outfit successfully launched and landed a sub-orbital rocket at a secret, Texas facility last month.
Originally scheduled for Sunday evening, the launch was delayed for a day after modeling showed more favorable rocket-landing weather on Monday night, Musk announced in a tweet. However, Orbcomm (“ORBC”)—the communications company whose 11 satellites will ride to orbit aboard the Falcon 9—suggested the delay allowed SpaceX engineers additional time to review data from a test conducted Friday in which the rocket’s engines were fired on the ground to ensure they are working properly.
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That engine test had been previously delayed from Wednesday to Thursday and ultimately Friday, following what Musk described as a problem chilling the rocket’s super-cooled liquid oxygen propellant—one of the many technologies that SpaceX has modified this more powerful Falcon 9 launch. Pushing to Monday not only allowed an extended review of the test data, but also gave the propellant more time to cool.
Though SpaceX’s previous mission ended in a rocket failure and complete loss of its payload, Orbcomm isn’t sweating the delays or the launch pad hiccups. In the rocket launch industry, an occasional failure is part of the cost of doing business. And “return-to-flight” missions such as tonight’s historically have high success rates due to the intense amount of scrutiny placed on them. Orbcomm CEO Marc Eisenberg even told reporters he is confident in the Falcon 9 largely because this mission is so important to SpaceX.
WATCH: For more on SpaceX’s exciting launches, see this Fortune video.
But there is a lot of pressure on SpaceX to right things with a rocket that’s also part test vehicle. If everything goes to plan, the Falcon 9 will place the 11 Orbcomm satellites in orbit roughly 500 miles up; reignite its upgraded, second-stage engine to test what’s needed to carry heavier payloads into higher, future orbits; and land its first stage rocket back at Cape Canaveral, proving that the company has mastered its most difficult step in developing reusable rockets. Such a landing would have a huge financial impact for the company, eventually trimming the current $70-80 million cost of launching a Falcon 9 rocket down to less than $10 million, by some estimates.
Regardless of whether it sticks the landing, a successful launch of Orbcomm’s satellites will put SpaceX back in business at a critical time. Recently certified to launch national security satellites for the U.S. Air Force, SpaceX is eligible for a potentially huge chunk of business from the U.S. government going forward. Over the next few months it also has an International Space Station run and at least two more commercial satellite launches planned.
A second consecutive failure, on the other hand, could seriously shake customers’ confidence in SpaceX and in the Falcon 9, jeopardizing its future launch contracts. With so much hanging in the balance, tonight’s launch could mark a major turning point for the company.