Originally Published: 11 DEC 23 11:07 ET

Updated: 11 DEC 23 20:23 ET

By Jackie Wattles, CNN

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(CNN) — SpaceX has postponed the next launch of its Falcon Heavy rocket until at least Tuesday evening, delaying the latest mission of a mysterious space plane that remains one of the US military’s most fascinating projects as the country races to journey deeper into the cosmos.

The secretive X-37B robotic spacecraft was set to take off aboard a SpaceX Falcon Heavy rocket at 8:14 p.m. ET from NASA’s Kennedy Space Center in Florida on Monday. But the company said Monday evening that it was pushing back the launch “due to a ground side issue” — indicating a problem with the rocket’s launchpad or fueling systems, according to a social media post from SpaceX.

The company said it is now working toward lifting off at the next available launch opportunity, which is Tuesday at 8:14 pm ET.

Resembling a miniature NASA space shuttle with the windows blacked out, the reusable X-37B space plane is set to begin its seventh experimental mission.

Many of the X-37B’s mysterious tasks have been classified, but the US Space Force did provide a few details about the goals for this uncrewed mission.

What X-37B is doing

The space plane makes it possible for the United States to carry out experiments to better understand how to improve ongoing and upcoming space operations and push the boundaries of what’s possible, according to a statement by Gen. B. Chance Saltzman, chief of space operations for the US Space Force.

Among the research on board will be a NASA experiment that aims to find ways to sustain astronauts on future deep-space missions. Called Seeds-2, it will “expose plant seeds to the harsh radiation environment of long-duration spaceflight” and build on previous research carried out on X-37B missions.

The experiments also “include operating the reusable spaceplane in new orbital regimes, experimenting with future space domain awareness technologies, and investigating the radiation effects on materials provided by NASA,” according to the US Space Force.

Orbital regimes are areas of space where different celestial bodies have the biggest gravitational influence. If Earth’s gravity is dominant, for example, it’s called the “geocentric regime.” And our entire solar system is part of the “solar regime,” where the sun is the biggest gravitational source, the US Space Force “Spacepower” publication explains.

By “new orbital regimes,” the military likely is referring to the fact that the X-37B can be placed much deeper into space than previous missions — perhaps even to the “cislunar regime,” which is defined as the gravitational system that includes Earth and the moon.

A powerful ride

The launch will mark the first time that the space plane has hitched a ride on a SpaceX Falcon Heavy, which was briefly the most powerful operational rocket in the world after its debut in 2018.

The rocket looks like three of the company’s Falcon 9 rockets strapped together, with the two boosters on each side providing additional thrust and power.

Previously, the X-37B has launched on the SpaceX Falcon 9 vehicle and the Atlas V rocket built by United Launch Alliance, a Lockheed Martin-Boeing joint venture.

The Falcon Heavy produces more thrust than both of those rockets combined.

Space technology innovations

It’s not clear how long the spacecraft will spend orbiting Earth for this stint, though historically each X-37B flight has been increasingly longer than the last.

The last trip to orbit for the autonomous X-37B concluded in November 2022, after the spacecraft logged nearly 909 days in space. During that sixth mission, as previously reported by CNN, the space plane carried experimental technology designed by the US Navy to convert solar energy and transmit it back to the ground, according to the military.

In August 2020, the X-37B won the prestigious Robert J. Collier Trophy, which honors aerospace achievements, besting the Hubble Space Telescope. (The James Webb Space Telescope won the prize most recently.)

“Sophisticated and uncrewed, the X-37B advances reusable spaceplane technologies and operates experiments in space that are returned for further examination on earth,” said Barbara Barrett, secretary of the US Air Force in a statement at the time.

The X-37B has already spent more than 3,700 days in space on prior uncrewed missions.

The-CNN-Wire

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