SpaceX's Falcon Heavy rocket has lifted off again, this time embarking on what the company calls one of the most challenging launches in its history. With a slew of government satellites and important spacecraft onboard, the world's most powerful operational vehicle took off into the night sky for the first time, on a mission to deliver payloads into three different orbits.

"This will be our most difficult launch ever," said SpaceX CEO Elon Musk on Twitter leading up to today's STP-2 mission. The launch tasked the Falcon Heavy vehicle with completing four separate upper-stage engine burns, three different payload deployments and then fire the engines on the three separated boosters to bring them safely back down to Earth.

Adding another layer of complexity is the fact that the side boosters used for today's mission, or two of the three boosters making up the Falcon Heavy's first stage, flew in an earlier mission in April, making this the first mission to reuse side boosters from an earlier Falcon Heavy flight. That April mission was the first time SpaceX managed to recover all three boosters, with only two of the three recovered during Falcon Heavy's first outing in 2018.

This was again the story today. As Musk said on Twitter just before the launch, retrieving the center core was always going to be a tough ask, owing to the bigger thrust needed to lift the large array of payloads into space and therefore the higher velocities upon its return.

"Odds of center core surviving are about 50 percent in my opinion, as it's coming in about four time times faster than a rifle bullet," he wrote.

The two side boosters came down safely at Cape Canaveral, but the center core narrowly missed the landing on SpaceX's drone ship on the Atlantic Ocean, and exploded on impact with the water.

The mission's success is significant for SpaceX, as it is the first time the US Department of Defense has sent satellites to orbit using the company's much-vaunted Falcon Heavy vehicle. The US Air Force is working toward certifying the rocket for its National Security Space Launch program, through which it intends to ensure access to space for the US government.

Among the 24 satellites onboard were payloads from the National Oceanic and Atmospheric Administration, US-based universities, DoD research labs and NASA. Those from NASA include a fridge-sized atomic clock to improve navigation of its spacecraft, a pair of satellites hoped to improve communication, and a new demonstrator spacecraft to test out a new peach-colored propellant.

Also packed into the Falcon Heavy's nosecone ahead of the launch was the LightSail 2 CubeSat, a tiny, sail-equipped spacecraft that will be propelled by photons from starlight. Developed by Bill Nye's Planetary Society, the CubeSat will remain in the Earth's orbit but hopefully harness these solar photons to sail away into larger and larger loops around the planet.

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