The panel is led by former aerospace executive Norman Augustine
Engineers developing Nasa's new rockets have denied that the agency's human spaceflight plans are too expensive, too risky and subject to long delays.
The US space agency has already spent four years developing its next-generation rockets, called Ares.
The engineers defended their work before a presidential panel tasked with reviewing Nasa's plans beyond 2010, when the shuttle is due to be retired.
They said Ares was the safest, fastest way to get Americans back into space.
Critics have asked questions about the technical scope of the next-generation human spaceflight programme, known as Constellation, and Nasa's ability to manage its cost.
Some have called for the Ares launchers to be scrapped in favour of adapting existing rockets.
"We have done what we said we would do and we are well on the way to our first test flight," said Steve Cook, head of the Ares project office at Nasa's Marshall Space Flight Center in Huntsville, Alabama.
Speaking during a public hearing, Mr Cook dismissed suggestions by some that the space agency was on a flawed path with Ares.
"There have been several outside reviews since we began," he explained.
Constellation calls for a class of rockets known collectively as Ares
Other officials told the panel they were working to solve technical challenges with the new system, including a slim possibility that powerful energy waves created during a launch could injure astronauts or make it impossible for them to perform basic tasks.
Norman Augustine, chair of the review committee and former chief executive of aerospace giant Lockheed Martin, said members would offer broad options to President Obama.
Those could range from continuing to fly the space shuttle to moving forward with the Constellation programme without any changes, he said.
"We will not be in the tweaking business," Mr Augustine said during a news conference.
Under a $35bn (£21bn; 24bn euros) plan put in place under former President George W Bush, Nasa is working to retire the shuttle fleet by the end of 2010 and to fly its new Ares-Orion system by 2015.
President Obama appointed the Augustine committee in May to gather information from space agency officials, scientists, the aerospace industry and from Congress about the best future course for US manned space flight.
Engineers said that Nasa planned to launch a test version of the Ares I rocket by October 31.
Under current plans, Ares I would launch astronauts in Orion, an Apollo-like capsule that is being designed to carry crew to the Moon and other destinations.
Work is not as far along on a larger rocket called Ares V, which would lift heavy payloads into orbit for a mission to the Moon and an eventual trip to Mars.
Mike Griffin says that a safe, robust system cannot be built "on the cheap"
Former Nasa Administrator Michael Griffin met with the panel privately before Wednesday's hearing. In a letter addressed to Mr Augustine, Dr Griffin said the Constellation programme was being subjected to "broad but shallow criticism" when Nasa needed continuity in its planning.
"Do not close off options. Do not allow the parochial voices of the small-minded, the self-interested, and the uninformed to prevail. Choose the future," the former space agency chief wrote in the letter.
He said that the space agency's funding had been in decline since the Clinton Administration, yet, he added: "No essential mission responsibility has been removed from Nasa as a result. Indeed, tasks have been added.
"This strategy cannot work. A safe and robust human spaceflight programme cannot be built 'on the cheap'."
Dr Griffin led Nasa from April 2005 to January 2009. In April, Dr Griffin took up the post of professor of mechanical and aerospace engineering at the University of Alabama in Huntsville.