The cargo missions flown by the private Dream Chaser space plane will launch atop United Launch Alliance (ULA) Atlas V rockets, at least at first.

Dream Chaser's builder, Sierra Nevada Corp. (SNC), and ULA have signed an agreement to use Atlas V rockets for the robotic space plane's first two resupply flights to the International Space Station (ISS), representatives of the two companies announced last week. Those missions are scheduled to lift off in 2020 and 2021.

"SNC recognizes the proven reliability of the Atlas V rocket, and its availability and schedule performance make it the right choice for the first two flights of the Dream Chaser," Mark Sirangelo, corporate vice president of Sierra Nevada's space systems business area, said in a statement.

Artist's illustration of Sierra Nevada Corp.'s Dream Chaser space plane atop a United Launch Alliance Atlas V rocket. (Image credit: Sierra Nevada Corp.)

Sierra Nevada has been developing the 30-foot-long (9 meters) Dream Chaser for more than a decade. Like NASA's now-retired space shuttle orbiter, Dream Chaser launches vertically and comes back down to Earth horizontally in a runway landing.

Sierra Nevada is working on both crewed and uncrewed variants of the space plane. In 2016, NASA tabbed the uncrewed Dream Chaser to fly cargo to and from the ISS, under a Commercial Resupply Services 2 contract. (Two other private robotic vehicles, SpaceX's Dragon capsule and Orbital ATK's Cygnus spacecraft, are already flying cargo missions to the orbiting lab for the space agency.)

This United Launch Alliance graphic shows how the Sierra Nevada Corporation's Dream Chaser space plane will launch atop Atlas V rockets to deliver cargo to the International Space Station. (Image credit: United Launch Alliance)

The Atlas V is a workhorse rocket that has launched a number of high-profile payloads over the years, including NASA's New Horizons Pluto probe, Juno Jupiter orbiter and Curiosity Mars rover. The Atlas V has also launched all four missions of the U.S. Air Force's X-37B vehicle — a small, robotic space plane, like the uncrewed Dream Chaser.

An Atlas V will also loft the maiden moon mission of the Peregrine lander, a lunar spacecraft being developed by Pittsburgh-based company Astrobotic. That flight is currently scheduled to take place in 2019.

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