So, NASA's proposed Ares rockets are not the only way to get people and cargo to the moon.

The space agency has invested billions of dollars, years of engineering and its political muscle to argue that there is only one way: NASA's way.

Not true. The leaders of America's top space-launch companies and even the head of NASA's shuttle program told a presidential commission last week about several viable options for launching the Orion spacecraft and its astronauts into Earth orbit, where they could hook up with another spacecraft for a ride to the moon. Ares is one option, but it's not the only one.

NASA says it studied all of these options years ago. Experts looked over data about cost, power and safety. The government team determined that two new rockets (relying partly on re-engineered shuttle components) were the best answer to President George W. Bush's call to replace the shuttle and return humans to the moon.

Administrator Mike Griffin went further, saying the Ares system was the only way and enlisting his deputies to pound that point home at every turn. Anyone selling an alternative was foolhardy or maybe bitter about not winning the work.

With the Ares I crew-launching rocket destined to end up over-budget and behind schedule, more and more experts and observers are reconsidering other options.

Chief among them: leveraging the $4 billion investment of the Air Force, The Boeing Co. and Lockheed Martin Corp. in the Delta IV and Atlas V rockets that have launched military, science and commercial spacecraft for five years now. Those rockets could be modified to carry Orion to orbit, too, perhaps saving money and time, as well as shoring up demand for two rockets the U.S. says are critical to national security.

Rocket operator United Launch Alliance and respected independent analysis group Aerospace Corp. say the Delta IV could do the job now assigned to Ares I.

Both agree a Delta IV crew-launcher would cost less than sticking with Ares I. Aerospace says it could take a few years longer to ready the Delta for human flights.

So, whom to believe? Which system would work better? Engineers and advocates of every possible alternative are passionate about their concepts. It's important to remember, however, that some have billions of dollars worth of government contracts at stake. Others have personal pride.

The committee President Barack Obama assigned to study human spaceflight plans should carefully review the data with an independent eye. It's important that the contentions and assertions of all sides be treated with respect -- and with skepticism. The pushers of various spaceflight systems throughout the short history of the program often overstate capabilities, understate costs and rattle off impossibly optimistic schedules in order to sell their ideas.

Certainly, Ares appears capable of launching the Orion spacecraft. A heavier-lift version of Ares appears capable of launching the heavy equipment that must go along on the trip. The Delta proposal pitched by United Launch Alliance boss Mike Gass also seemed viable, as did some others.

Gass made the best point during the first public meeting of the presidential committee: Let's get the performance data on the table and compare launch systems, apples-to-apples, he said. Let's do it with independent reviewers and identify the best plan for the United States of America.