By JOHN SCHWARTZ


The United States space agency has named a new rocket Ares, as in the god of war - and its life has been a battle from the start.

Ares I is part of a new system of spacecraft being designed by the National Aeronautics and Space Administration to replace the nation’s aging space shuttles. The Ares I and its Orion capsule, along with a companion heavy-lift rocket known as the Ares V, are meant for travel to the moon and beyond.

Technical troubles have dogged the design process for the Ares I, the first of the rockets scheduled to be built, with attendant delays and growing costs. Some critics say there are profound problems with the rocket’s design, while other observers argue that technical complications crop up in any spacecraft development program of this scope.

The issues have become a focus of the presidential transition team, and the space program could undergo a transformation after Barack Obama takes office. During his campaign,

Mr.Obama expressed support for NASA and criticized the five-year gap between the scheduled end of the space shuttle program in 2010 and the planned debut of the first components of the new system, which NASA has given the overall name Constellation, in 2015.

But NASA will be competing for money as the new administration faces urgent and expensive crises.

The Obama team is looking into whether increased financing could narrow the five-year flight gap by speeding development of the new spacecraft. It has asked what the costs and consequences might be of continuing to fly the shuttles for one or two more flights. The transition team has also asked whether the development program is truly in trouble and, if so, whether the Ares I should be modified or replaced by rockets used by the Air Force to launch satellites, or the Ariane 5 rocket from Europe.

A spokesman for the transition team, Nick Shapiro, said that“the role of the agency review teams is not to make recommendations on any of the issues they are reviewing. They are fact-finding and preparing the full range of options for consideration by the incoming appointees.”

Nonetheless, tensions have risen between the incoming administration and the management of NASA, whose administrator, Michael D.Griffin, is fighting to keep the program on course. If he is not reappointed by Mr.Obama, his term will end January 20.

President Bush announced the new direction for the space program in January 2004, nearly a year after the loss of the shuttle Columbia underscored the risks inherent in the spacecraft - especially the potential for debris to strike it during launching. In 2005, NASA announced the Constellation program, with the Orion capsule that would ride atop the Ares I, out of the way of launch debris.

The Ares rockets are very different - both from the shuttle and each other. Ares I uses as its first stage a lengthened solid rocket booster like the ones used by the shuttle. The second stage will burn liquid hydrogen and liquid oxygen, as the shuttle’s main engines do. Atop the stack will sit the Orion. The first test of an unmanned Ares I could take place in summer.

The design process has run into technical problems. Orion is far heavier than the Apollo capsule that preceded the shuttle, and weight issues have required redesigns of both the capsule and the rocket. Engineers have also had to come up with ways to dampen potentially dangerous vibrations as the solid rocket engine empties.

Some in the development program have complained that it is run in a way that stifles dissent and innovation. Jeffrey Finckenor, an engineer who left NASA last year, sent a goodbye letter to colleagues that expressed his frustrations with the program.“At the highest levels of the agency, there seems to be a belief that you can mandate reality,”he wrote,“followed by a refusal to accept any information that runs counter to that mandate.”

NASA officials say the Constellation program is actually coming along well. In an interview in November, Mr.Griffin said,“I can’t imagine somebody thinks you’re going to develop a new space transportation system and encounter no challenges.”The ones NASA is encountering, he said, are“routine in the extreme.”