A SpaceX Falcon Heavy lifts off from Launch Complex 39A June 25 on the Space Test Program 2 mission. Credit: NASA/Joel Kowsky

WASHINGTON — A SpaceX Falcon Heavy lifted off early June 25 carrying two dozen small satellites on a mission to demonstrate the rocket’s capabilities for the U.S. Air Force.

The Falcon Heavy lifted off at 2:30 a.m. Eastern from Launch Complex 39A at the Kennedy Space Center. The launch took place three hours into a four-hour launch window, delayed by a problem with a ground hydraulics system.

The rocket’s two side boosters made synchronized landings on neighboring pads at the former Launch Complex 13 at Cape Canaveral Air Force Station, several kilometers to the south of the launch site. Both side boosters also flew on the previous Falcon Heavy mission, launching the Arabsat-6A satellite in April.

The rocket’s center booster attempted a landing on a droneship more than 1,200 kilometers from the launch site in the Atlantic Ocean. Video from that droneship show it crashing in the ocean near the ship, which was unharmed.

SpaceX had warned that the center core booster landing would be difficult given its high-speed reentry. “Odds of center core surviving are about 50% [in my opinion], as it’s coming in about 4 times faster than a rifle bullet,” tweeted SpaceX Chief Executive Elon Musk several hours before the launch.

“Center core RUD,” or “rapid unscheduled disassembly,” Musk tweeted after the launch. “It was a long shot.

SpaceX, which has made landings of Falcon 9 first stages routine in recent years, has been unable to return the center booster on the three Falcon Heavy launches to date. The booster just missed the droneship on the rocket’s inaugural launch in February 2018. The booster did land on the droneship on the Arabsat-6A mission in April, but toppled in heavy seas before crews could secure the stage to the ship’s deck.

The company did achieve another milestone with the launch, though. SpaceX reported a ship equipped with a large net caught one of the two payload fairing halves, part of a long-running effort to catch and eventually reuse those components.

Falcon Heavy STP-2 time lapse
A time lapse of the Falcon Heavy launch, showing the rocket ascending from Launch Complex 39A and the two side boosters returning several kilometers away at Cape Canaveral Air Force Station. Credit: Craig Vander Galien

The rocket lifted off to start the Space Test Program (STP) 2 mission for the Air Force’s Space and Missile Systems Center. The rocket carried 24 satellites, with a total mass, including adapters, of 3,700 kilograms.

Deployment of the satellites started less than 13 minutes after liftoff, shortly after the second stage completed its first burn and reached orbit. The final payload was scheduled for release more than three and a half hours after liftoff, after three additional burns of the rocket.

The satellites are primarily science and technology demonstration missions for various organizations, including the Defense Department, NASA, NOAA and several universities. The include the six satellites of the COSMIC-2 system, developed by NOAA and Taiwan to collect GPS radio occultation data for weather forecasting, and NASA’s Green Propellant Infusion Mission, to test a new non-toxic or “green” propellant for satellites.

The Orbital Test Bed satellite, built by General Atomics Electromagnetic Systems (formerly Surrey Satellite Technology U.S.), carries several experiments, including NASA’s Deep Space Atomic Clock. That experiment will test the performance of a miniature but highly accurate clock that could aid in navigation for future deep space missions. The satellite is also carrying a payload from Celestis, a company that offers space memorial services, with cremated remains from more than 150 people.

The largest satellite on the mission, and the last to be deployed from the upper stage, is the Demonstration and Science Experiments (DSX) satellite from the Air Force Research Laboratory. Placed into an orbit of 6,000 by 12,000 kilometers, DSX will study the space radiation environment with various sensors, including the Space Environment Testbeds experiment from NASA.

While deploying the various satellites, STP-2 is intended to demonstrate the performance of the Falcon Heavy vehicle. The company described is as “among the most challenging launches in SpaceX history” because of the number of upper stage burns and deployments. The Air Force also planned to use the launch to gain experience with reused boosters.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...