In testimony (PDF) Wednesday before the Senate Commerce, Science, and Transportation Committee's Subcommittee on Science and Space, Bolden said commercial space flights may not begin until 2017, two years after an original target of 2015, due to the current funding schedule.
Still, he cited the successful completion of the space shuttle program and NASA's work at the International Space Station as highlights in a year that some might consider bumpy for the space agency.
[ Learn more about NASA's short-term space exploration goals in NASA's Newest Mars Rover Prepares For Close-Up. ]
NASA this year has faced budget cuts as well as criticism for lacking the technological capability to enact its future space exploration plans.
Bolden, however, was optimistic about the next steps for NASA to send people and technology into space, and said the investment the agency is putting in this area also will benefit national security and the U.S. economy.
"By investing in space technology research, NASA can be a significant part of the solution to our nation's economic, national security, and geopolitical challenges," Bolden told the committee, saying the Space Technology program will "act as a catalyst for innovation throughout America's aerospace industries, and it will create new, high-technology jobs and innovations in manufacturing that will guarantee American leadership in the new technology economy."
One aspect of NASA's plans is the Commercial Crew Program (CCP), a partnership between NASA and the private sector to enable commercial space flight. NASA will put out a final RFP by the end of the year to develop a complete end-to-end crew transportation and rescue system design that includes spacecraft, launch vehicles, launch services, ground and mission operations, and recovery, Bolden said.
The NASA official appealed to the Senate to approve NASA's budget request of $850 million for the CCP, saying that it would allow for the first flights to the ISS in 2016. However, the $500 million in funding that's been allotted from the NASA Authorization Act would push those flights up to 2017.
"A reduction in funding from the president's request could significantly impact the program's schedule, risk posture, and acquisition strategy," he said.
NASA also is working on sending astronauts deeper into space than they went with the space shuttle--indeed, further than they've gone since the Apollo-17 lunar landing in December 1972, according to Bolden.
To that end, the agency "is aggressively moving forward" with its next-generation astronaut spacecraft and launch system, the Orion Multi-Purpose Crew Vehicle (MPCV) and Space Launch System (SLS), he said.
The MPCV is meant to transport crew from Earth to destinations, such as Mars and near-Earth asteroids, that go beyond the low orbits near Earth that most space missions have traveled to. It should provide all the services necessary to support up to four people for up to 21-day missions.
For longer missions, such as those to asteroids or to other planets, NASA plans to add a space-habitation module to the craft to allow for long-duration habitation in space.
NASA plans to test both aspects of the system without a crew in 2017; a crewed test flight is scheduled for 2021, Bolden said.
Bolden also highlighted other space technologies NASA seeks to develop to facilitate these next-generation space travel plans. The agency has invested $175 million in a series of advancements to this end, including a space-based high-speed optical communications system, a deep-space atomic clock, and a space solar sail.