Dream Chaser is a private spacecraft from Sierra Nevada Corp. that will bring cargo to the International Space Station in the 2020s. Its first two resupply flights to the ISS will lift off on Atlas V rockets from United Launch Alliance in 2020 and 2021. Dream Chaser flight tests continue and the spacecraft prototype had a successful free flight in November 2017.

The spacecraft was originally targeted to carry people, but lost out to both SpaceX and Boeing in 2014 during the last contract award of the Commercial Crew Program. In 2016, NASA selected Dream Chaser to fly six cargo missions to the International Space Station by 2024. The agency also selected SpaceX and Orbital ATK spacecraft at the same time.

Dream Chaser looks a bit like a stubby version of the space shuttle; it is based on NASA and Russian designs. The spacecraft is about 30 feet (9 meters) long and can carry up to 12,125 lbs. (5,500 kilograms) of cargo up to the International Space Station. The spacecraft has a wingspan of roughly 23 feet (7 meters), about half the wingspan of a small business aircraft called Learjet 45, according to Business Insider.

Dream Chaser's design is based mainly on the HL-20 — a NASA spacecraft design from the 1980s that was itself based on a Soviet spacecraft called the BOR-4. But the HL-20 design was never used for space. A company called SpaceDev resurrected the design prior to being purchased by Sierra Nevada Corp. in 2008.

According to Ars Technica, in 2006 SpaceDev signed a licensing agreement with NASA to reuse HL-20 for the Dream Chaser concept. Despite the agency heritage, SpaceDev failed to get funding under the initial NASA Commercial Orbital Transportation Systems (COTS) program to fund commercial spacecraft.

SpaceDev, however, continued work with NASA under a non-reimbursable Space Act agreement in 2007. That same year, it signed a memorandum of understanding with United Launch Alliance to put Dream Chaser on an Atlas 5 rocket. When Sierra Nevada purchased SpaceDev, it intended to use Dream Chaser for astronaut flights to the International Space Station.

In August 2012, Sierra Nevada was one of three companies that received money under the Commercial Crew Integrated Capability (CCiCap) award. CCiCap was the third phase of commercial crew development. It was supposed to help companies in the latter stages of spacecraft work to get their ships ready for flight. Sierra Nevada's contract, which was worth up to $212.5 million, paid out money as the company progressed through certain milestones. 

The company also passed several major tests in 2012, most notably a "captive carry" flight test where it rode below a helicopter. The spacecraft did a single glide test in 2013 where it was released from a helicopter and arrived at the runway, only to skid off and cause damage to the vehicle.

"We had a successful approach to the runway. The vehicle flared on cue and the speeds were perfect," said Mark Sirangelo, corporate vice president and head of Sierra Nevada Corporation's (SNC) Space Systems based in Louisville, Colo., in a Space.com interview in October 2013.

"We hit the centerline exactly where we needed to be. On approach and landing, the left main gear did not deploy satisfactorily," he added. 

In September 2014, NASA announced the next and final phase of the commercial spaceflight program would see SpaceX's Dragon and Boeing's CST-100 spacecraft funded for the Commercial Crew Transportation Capability (CCtCap). Crewed flights to the International Space Station are expected starting in 2018.

Sierra Nevada filed a protest Sept. 26, 2014, that temporarily halted work on commercial crew endeavors. The company said that Dream Chaser's technical concept was equally as mature as at least one of the rival companies, and that there were "serious questions and inconsistencies in the source selection process."

While the U.S. government allowed work to continue on commercial crew, its General Accountability Office reviewed the company’s protest. In January 2015, the office said it would rule against Sierra Nevada

"GAO disagreed with Sierra Nevada's arguments about NASA's evaluation, and found no undue emphasis on NASA's consideration of each offeror's proposed schedule, and likelihood to achieve crew transportation system certification not later than 2017," part of the statement read.

In early 2016, NASA announced that Sierra Nevada (along with SpaceX and Orbital ATK) would all be listed as possible providers for cargo missions to ISS before 2024.  The NASA contract also triggered a $36 million investment by the 22-nation European Space Agency in January 2016. At the time, ESA said it would build the first flight model of the International Berthing and Docking Mechanism (IBDM). Dream Chaser will use IBDM to attach itself to the space station. 

In July 2017, Sierra Nevada Corp. and United Launch Alliance signed an agreement to fly Dream Chaser to the ISS on Atlas V rockets. The first two flights (the ones covered under the agreement) are expected 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.

Dream Chaser successfully performed a captive carry flight in August 2017, flying with the help of a helicopter over California's Mojave Desert. The test flight successfully brought Dream Chaser to an altitude of about 12,500 feet (3,810 meters), or about a third of the altitude of a typical commercial airplane flight. [Video: Watch Sierra Nevada's Dream Chaser Captive Carry Test]

"The captive carry is part of a series of tests for a developmental space act agreement SNC has with NASA's Commercial Crew Program," NASA officials wrote in a video description at the time. "The data from the tests help SNC validate the aerodynamic properties, flight software and control system performance of the Dream Chaser."

Three months later, Dream Chaser made a successful free-flight test above Mojave after being carried up into the air with a helicopter. "The Dream Chaser had a beautiful flight and landing!" Sierra Nevada representatives announced on Twitter in November 2017.