BROWNSVILLE — In late 2015 the trucks started rolling, dumping more than 300,000 cubic yards of locally sourced dirt at the future SpaceX launch pad site where S.H. 4 dead-ends at Boca Chica beach in South Texas.

The technical term is “soil surcharging,” a process of compressing the underlying soil in order to stabilize it — in this case to create a suitable foundation for launch-complex structures. That process is now complete, leading to the artificial mesa being leveled by earthmovers.

Once that’s done, SpaceX will install a 95,000-gallon liquid oxygen tank and an 80,000-gallon methane tank that the company has taken delivery on in recent months. The tanks, stored for now at the SpaceX control center area a few miles west of the launch site, will be used to support propellant-loading operations during space vehicle tests beginning sometime in 2019.

In February, SpaceX founder and CEO Elon Musk said tests at Boca Chica would entail “short hopper flights with the spaceship part of BFR.”

BFR stands for Big Falcon Rocket, a fully reusable, two-stage vehicle consisting of a booster and a spaceship. “Hopper flights” refer to SpaceX’s Grasshopper program of low-altitude launch and landing tests of its Falcon 9 rocket at the company’s McGregor test facility.

Musk had been banking on its biggest rocket, the Falcon Heavy, to get humans to Mars, though the focus has shifted to development of the larger, more powerful BFR for Mars flights — an ambitious goal Musk touched on at the Boca Chica groundbreaking ceremony in September 2014.

“It could very well be that the first person that departs for another planet could depart from this location,” he said.

Over the last two years SpaceX, based in suburban Los Angeles, has installed two giant ground-station antennas it acquired from Cape Canaveral in Florida and more than 600 kilowatts of solar arrays to power them. The antennas will be used to track manned Crew Dragon missions to and from the International Space Station as well as flights blasting off from Boca Chica.

“The ongoing construction of our launch pad in South Texas is proceeding well,” said company spokesman Sean Pitt. “SpaceX has now received the final major ground-system tank needed to support initial test flights of the Big Falcon Spaceship.”

Musk estimated initially that the first Boca Chica launch could happen by late 2016. The need for soil surcharging created delays, then in September 2016 a Falcon 9 rocket exploded during a fueling test at Cape Canaveral, destroying the launch pad, which SpaceX had to rebuild.

The company made its first launch from the rebuilt Launch Pad Complex 40 on Dec. 15, 2017, a resupply mission to the ISS using a Falcon 9 rocket and unmanned Dragon capsule. On Feb. 6, SpaceX conducted the maiden launch of the Falcon Heavy rocket from Launch Pad 39a at Cape Canaveral’s Kennedy Space Center.

That’s the same pad from which Apollo 11 departed for the moon on July 16, 1969, four days before Neil Armstrong became the first human to walk on the lunar surface. Last August, SpaceX affixed a walkway to Launch Pad 39a that NASA astronauts will use to board the Crew Dragon capsule for missions to the ISS.

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