Can private-sector space business be profitable, or is it just an exciting way for billionaires to live out their fantasies?

The latest SpaceX rocket is sitting on a launch pad in Cape Canaveral, Florida, carrying 11 Orbcomm communications satellites—and a lot of Elon Musk’s biggest aspirations.

Lift-off is expected just after 8:30 p.m. EST. You can watch a live video of it at SpaceX’s website.

Tonight’s launch may be the most significant test of the company since the 2008 flight of the first Falcon rocket from a Pacific atoll that essentially saved the company from failure. Here’s why:

Return to flight

Since the company’s June mission to the International Space Station ended in an explosive failure, SpaceX has been forced to delay its commercial manifest, costing it and its clients millions of dollars. None of that appears to have fazed its investors.

But the company’s return to flight has been expected and delayed many times since, and today’s launch marks one of the last opportunities to do so this year. SpaceX has three more launches scheduled in quick succession after this one, including tests of its program developing a human-carrying spacecraft for NASA. Further problems tonight would mean more big delays and increased political pressure on the company as it tries to prove itself for large government contracts.

Billionaire battles for reusable rockets

Blue Origin, the space company founded by Amazon CEO Jeff Bezos, recently demonstrated that its New Shepherd rocket could fly a capsule 100 km up to the edge of space and then return to land vertically on a launch pad. It represents the latest step in the race for reusable rockets that could save millions of dollars per launch—a race that heretofore SpaceX had led, in court and in demonstrations at test sites and with a series of near-miss attempted landings on a sea-going platform.

Musk, who sent both congratulations and jibes Bezos’s way after the Amazon honcho humble-bragged his rocket’s achievements, clearly wants to settle the matter by making SpaceX the first space company to land an operational rocket: He delayed today’s launch 24 hours to get an extra 10% shot at a successful touchdown:

(Full disclosure: I have some credibility on the line, too.)

Height matters

One under-appreciated aspect of today’s flight but no less important is a plan to test the ability of SpaceX’s second-stage rocket to bring satellites to geosynchronous orbit. Satellites in that orbit, 36,000 kilometers above the earth, appear to stay in one spot from the ground, making it a very useful place to put a communications satellite.

SpaceX originally planned to use this launch to fly a satellite there for SES, a European company that plays a major role in space communications industry. Instead, after delivering Orbcomm’s satellites, it will perform a demonstration flight to “further validate the second stage relight system” needed to carry satellites into geosynchronous orbit. This is important not just for convincing a major commercial client, but also the US military, which needs SpaceX to take on such missions.