It's been a momentous Saturday for SpaceX, and for the future of crewed voyages into space.

At 2:49 a.m. ET, the American aerospace company founded by Elon Musk staged its first launch of Crew Dragon. It's big news because this is the first time a commercial interest has launched a spacecraft that was built to carry humans.

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American spaceflight has traditionally been the domain of NASA, but the past decade has seen a gradual shift toward having commercial interests share the responsibility. SpaceX and Boeing are leading that charge, so the successful Crew Dragon launch represents a major milestone moment.

It's still just a first step, however. Although the Dragon capsule itself is designed to carry a crew of up to seven astronauts skyward, the one that launched on Saturday -- Demo-1 is its designation -- is more of a test run: it's carrying a few hundred pounds of cargo, plus a sensor-filled dummy named "Ripley."

NASA administrator Jim Bridenstine hailed the launch as a "new era in spaceflight."

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He added: "We are looking forward to being one customer of many customers in a robust commercial marketplace in low-Earth orbit, so we can drive down costs and increase access in ways that, historically, have not been possible."

The cost savings Bridenstine mentioned are very real. After NASA retired its shuttle fleet in 2011, the U.S. has relied on Russia to bring astronauts to and from the International Space Station. Hitching a ride on a Russian Soyuz rocket costs roughly $80 million per seat, compared to the $51 million cost to fly on a SpaceX or Boeing vehicle.

Bridenstine's comments don't make it very clear, but NASA is closely involved with the U.S. development of commercial spaceflight. The agency's influence shapes various aspects of third-party planning, including design, safety, and funding, under its Commercial Crew Program.

Now that Demo-1 is in space, the next phase of its mission begins. Early on Sunday morning, the capsule will dock with the ISS to drop off its cargo. After that, Demo-1 will detach and begin its return trip to Earth.

Assuming everything goes well for Demo-1, the first Crew Dragon launch to carry actual humans into space could come as soon as summer 2019.