The robust Falcon Heavy was set to launch the U.S. Space Force’s robotic X-37B space plane from Florida on Monday night, December 11, known as USSF-52. However, SpaceX announced a scrub about 30 minutes before the planned liftoff time of 8:24 p.m. EST (0124 GMT).

“Tonight’s Falcon Heavy launch is postponed due to a ground-side issue; the vehicle and payload are in good condition. The team is preparing for the next launch opportunity for the USSF-52 mission, now scheduled for tomorrow night,” stated SpaceX on X (formerly known as Twitter).

— SpaceX (@SpaceX) December 12, 2023

USSF-52 marks the seventh launch for the reusable, 29-foot-long (8.8 meters) X-37B, primarily a testbed for new instruments and technologies, with most mission details classified.

While the first five X-37B missions launched atop United Launch Alliance Atlas V rockets, the most recent one, concluding in November 2022 after 908 days in orbit, used a SpaceX Falcon 9.

USSF-52, the first X-37B mission aboard a Falcon Heavy, aims to propel the space plane to higher orbits. The mission goals include “operating in new orbital regimes, experimenting with space domain awareness technologies, and investigating the radiation effects on NASA materials,” stated Space Force officials in a recent release.

One aspect of the mission involves exposing plant seeds to the harsh space environment for a NASA radiation experiment.

Falcon Heavy, introduced in February 2018, famously sent SpaceX founder Elon Musk’s Tesla Roadster into orbit around the sun on its debut flight. The rocket has completed eight flights to date, including four this year. Its latest launch occurred in October 2022, sending NASA’s Psyche asteroid probe into space.

Originally slated for Sunday (Dec. 10), the X-37B Falcon Heavy launch was postponed a day due to weather concerns.