“We believe the existing program is a fine program,” he said.

The panel issued a 12-page summary last week, and Mr. Augustine said it would try to complete the report this month.

Committee members agreed with Mr. Augustine on a central conclusion of the panel: NASA needs about $3 billion more a year  increasing the spending over the next decade on human spaceflight to $130 billion from $100 billion  or it will not be able to accomplish the goals of Constellation or any alternative program.

Without an increase, Mr. Augustine said, NASA could continue to operate the International Space Station and develop some new technology, but it would not get out of Earth orbit for the foreseeable future. “It will be a program that will inspire very few people,” he said.

A smaller increase of $1.5 billion a year was also insufficient, the panel concluded.

In addition, it said that none of the options appreciably shortens the gap between the retirement of the shuttles  when the United States will rely on Russia for transportation to and from the International Space Station  and the development of the Ares I.

The Ares, the first of the Constellation rockets, will not be ready for use until at least 2015, and the panel predicted that the schedule would slip to 2017.

Mr. Augustine, who spent two hours before the House committee, will be questioned by the Senate Commerce, Science and Transportation Committee on Wednesday.

Also testifying to the House committee on Tuesday were Michael D. Griffin, the former NASA administrator who stepped down in January with the change in administrations, and Joseph W. Dyer, a retired vice admiral who is chairman of the aerospace advisory panel at NASA.