Update Wednesday, Dec. 9 at 4:27 p.m. EST: The launch is now on "hold," and now anticipated to take place at 5:40 p.m. EST.

Update Wednesday, Dec. 9 at 4:02 p.m. EST: SpaceX is getting ready to launch again any minute. A livestream is below.

Update Tuesday, Dec. 8 at 5:41 p.m. EST: An automatic engine abort with 1 second to go before launch prevented a test flight from taking place Tuesday. This page will be updated if SpaceX says it will re-attempt a launch.

SpaceX plans to test its enormous Starship prototype over Boca Chica, Texas, on Tuesday (Dec. 8).

Starship is SpaceX's big, shiny rocket standing 160 feet (49 meters) tall and 30 feet (9 m) wide. Unlike the Crew Dragon, which is currently docked to the International Space Station, or the company's fleet of more standard rockets, Starship hasn't been built to serve a specific space agency or private customer's needs. Instead, it's designed to further CEO Elon Musk's stated goal of delivering large numbers of people or heavy payloads to the moon and eventually Mars — a goal NASA supported earlier this year with a $135 million investment, Spaceflight Now reported. The anticipated test will mark the first opportunity to see a completed Starship prototype in action.

Related: Here's every spaceship that's ever carried an astronaut into orbit

Today's 41,000-foot (12,500 m) test flight will top out slightly below the 50,000 feet (15,240 m) Musk initially projected, Dave Mosher reported for Business Insider. There's no official start time, but SpaceX said in the caption of a livestream posted to YouTube that if the flight doesn't take place by 5 p.m. CST it will likely be bumped to Wednesday (Dec. 9) or Thursday (Dec. 10). Spaceflight Now reporter Stephen Clark tweeted to point out that a NASA surveillance plane will be in the area around 3 p.m. CST, making that a plausible launch window.

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SpaceX has previously tested a Starship prototype, Starship Serial Number 4 (SN4), which exploded just after an engine test. This test of Starship Serial Number 8 (SN8) will take the rocket high into the atmosphere, turn it on its side, then have it attempt to right itself again for a landing. SpaceX has cautioned that a total success, including a safe landing, is unlikely, and that a failure at some stage would be normal for a test flight.

Several YouTube channels are livestreaming the launch site. The stream below includes a checklist of steps SpaceX will take before launch, giving viewers clues as to when the test might occur.

Originally published on Live Science.