Despite potential funding troubles, a new sense of optimism is surrounding NASA's Commercial Crew Program (CCP) to transport crews to and from the International Space Station (ISS) by 2017.

A mockup of Boeing's CST-100 entry for the CCP is undergoing internal evaluation by astronauts. The Apollo-shaped capsule has met eight of 19 milestones outlined under Boeing's $460 million NASA Commercial Crew Integrated Capability agreement, as the company aims for a critical design review (CDR) in the spring of 2014 and an unpiloted flight test in 2016. In parallel, Boeing is working under a $10 million, first-phase contract to certify the spacecraft's safety and performance for a piloted demonstration mission to the ISS in 2017.

Last week, the House Appropriations Committee approved $500 million and Senate appropriators $775 million for commercial crew development as part of NASA's 2014 budget. The first figure is well below the Obama administration's $821 million request, a figure NASA Administrator Charles Bolden has characterized as essential to meet the 2017 objective. Nonetheless, agency and company managers believe legislators are losing their skepticism over a program that has so far committed $1.4 billion to funding competing vehicle designs from SpaceX, Sierra Nevada, Boeing and others.

“We have a program, and it is executing,” said Kathy Lueders, NASA's deputy CCP manager. “I think Congress can recognize that and fund it appropriately.”

“It's still a draft,” echoed John Mulholland, Boeing program manager for commercial programs, speaking about the House and Senate spending bills. “I think they will come up with a number that NASA can use.”

The two CCP officials spoke July 22 as a second round of internal capsule evaluations by astronauts got underway, the first in a new, full-sized mockup of the CST-100, which is designed to carry up to seven astronauts or combinations of crew and cargo to the ISS. Boeing unveiled the mockup at the company's Houston Products Support Center.

“It's an American vehicle, it's an upgrade,” said NASA astronaut Serena Aunon, following her favorable evaluation of the seating, instrument panel, lighting and other internal features while dressed in a bulky space shuttle Advanced Crew Escape Suit (ACES). Without a U.S. alternative, Aunon and her U.S., Canadian, European and Japanese colleagues are stuck with Russia's three-person Soyuz as the only means of transportation to the ISS following the shuttle's 2011 retirement.

The evaluations collected this week could lead to modifications that would undergo a final round of astronaut assessments prior to the CDR, said Chris Ferguson, Boeing's director of crew and mission operations and a former shuttle commander.

Boeing has leaned hard on a half-century of prior spaceflight experience and borrowed from its success with commercial airliner production to tame CST-100's development costs. The capsule's outer mold line, for instance, closely resembles that of Boeing's losing design in the competition with Lockheed Martin for NASA's Orion crew exploration vehicle.

“There's not a whole lot of new technology,” Ferguson said. “A lot of it is state-of-the-art, a lot of it is off-the-shelf.”

While the CST-100 control panel layout is considered proprietary, pilot astronauts will board with electronic flight bags—tablet computers that serve as electronic instrument management devices, eliminating the paper-based reference materials of the space-shuttle era. Any switches, or knobs, serve a backup control function, Ferguson said.

The soft blue tones of internal illumination come from the Boeing Sky Interior light-emitting diode scheme introduced on later models of the 737.

While Boeing is comfortable with the ACES as a flight pressure suit for crewmembers, the company has agreed to listen to competing proposals before selecting a vendor.

Boeing is working toward the “rent-a-car” rather than the “taxi” model for commercial crew operations, meaning that NASA personnel—rather than company astronauts—would fly the CST-100. A United Launch Alliance Atlas V with a dual-engine Centaur upper stage will propel astronauts into orbit from Cape Canaveral on initial missions, though Boeing's design will accommodate other launch vehicles that demonstrate equal reliability, according to Mulholland.

Flight crews will likely spend about 2.5 hr. in the Boeing spacecraft prior to liftoff, comparable to shuttle operations. Boeing is planning a Flight Day One rendezvous and docking capability with the space station, rather than the shuttle's Day Three berthing. Russia introduced a Day One, four-orbit, rendezvous-and-docking profile earlier this year.

Boeing's customer base could expand to wealthy space tourists working through Space Adventures Ltd., or Bigelow Aerospace, which is developing a line of inflatable space stations for industrial and foreign government users.

Additionally, NASA may want to consider CST-100 “sortie missions” that would dispatch teams of astronauts to the ISS, trained for compressed spacewalk campaigns that would lift the external repair and maintenance burden from long-duration crews focused primarily on research, Ferguson suggested.