SpaceX has completed joining the bottom and top halves of the Starship orbital-scale prototype it’s building in Boca Chica, Texas. The gleaming silver spacecraft, which is the “Mk 1” prototype that SpaceX will use for high-altitude testing, using three of the Raptor engines that will ultimately power the production version, saw its bottom and top halves mated on Friday ahead of an update that SpaceX CEO Elon Musk will deliver on Saturday about the Starship program’s progress to date and next steps.

The prototype sports a slightly different design than we’ve seen in concept renders for the spacecraft, with two bottom fins and two fins near the top of the nose of the ship. These are designed to be used to help maneuver the vehicle during flight, especially during its controlled descent as it returns to Earth after missions, as Starship is intended to be a fully re-useable space vehicle. That reusability, along with the reusability of the Super Heavy booster being developed to propel it and its cargo to space, are key to SpaceX’s goals of eventually making humans truly multi planetary, and achieving some of the company’s more ambitious near-term goals, like achieving a permanent human presence on Mars.

Musk also shared photos of the three Raptor engines that will be installed on the Starship Mk1 prototype. Starship’s first prototype to fly was a subscale demonstration and testing vehicle codenamed “Starhopper,” which had only one Raptor engine and topped out at around 500 feet, as intended. The Mk1 will aim to reach as high as 63,000 feet in its own testing, which Musk has previously said should take place this year.

We’ll find out more about what’s next for the Starship program tomorrow, so check back right here on TechCrunch for updates live from Texas.