Boeing's CST-100 commercial crew concept. Photo Credit/Boeing

NASA selected four companies on Monday for additional funding under the agency’s Commercial Spaceflight Development Program to accelerate work on multiple spacecraft capable of transporting astronauts to and from the International Space Station.

The awards under the second round of Commercial Crew Development funding totaled nearly $270 million.

The space agency is hopeful that at least one U. S. company  will be capable of transporting astronauts and other passengers to Earth orbit by the middle of the decade. With NASA’s shuttle nearing retirement, the space agency plans to pay the Russians to provide the transportation until U. S. companies are available.

NASA’s selections include:

* The Boeing Co., of Houston, $92.3 million to continue design work on the CST-100, including integration of the spacecraft with prospective launch vehicles; development of the launch abort engine and other systems leading to a preliminary design review.

* Sierra Nevada Corp., of Louisville, Colo., $80 million, to mature the Dream Chaser crew transportation system with a focus on high risk systems also leading to a PDR.

Sierra Nevada's Dream Chaser space plane. Photo Credit/Sierra Nevada

*SpaceX, of Hawthorne, Calif., $75 million, for development of a side mount launch abort system engine and crew accommodation development for the Dragon capsule.

The SpaceX Dragon concept. Photo Credit/SpaceX

* Blue Origin, of Kent, Wash., $22 million for space vehicle development through system requirements review as well as ground and flight testing of a pusher escape system, engine pump and thrust chamber testing.

The awards are intended to support development through next May. NASA intends to host an additional competition open to the four companies and others to nurture end-to-end spacecraft development, said Phil McAlister, NASA’s acting director of commercial spacecraft development.

NASA announced the latest competition in October, drawing 22 proposals by the Dec. 13 submission deadline. In addition to the four companies selected, NASA carried out an in depth assessment of proposals from ATK Aerospace, Excalibur Almaz, Orbital Sciences Corp. and United Launch Alliance.

“We considered how far each company would progress technically under its proposed efforts, and specifically the degree to which each company could accelerate the development of its own concepts and accelerate the availability of a U. S. commercial crew  transportation system,” said McAlister. “We also considered the viability of the company’s business approach to support and carry out its technical development plan.”