WASHINGTON — House Science and Technology Committee Chairman Bart Gordon (D-Tenn.) has drafted a new version of the three-year NASA authorization bill the panel approved in July that recommends substantive changes to the original measure, including more money for commercial space taxis and robotic exploration precursor missions called for in a companion measure approved by the full Senate in August.

“This is House compromise language, with bipartisan support,” Gordon said in a Sept. 23 statement. “It reflects months of discussion and input from many Members. As a result, we believe we have a bill that both builds on and improves on H.R. 5781, the NASA Authorization Act that was marked up by the Science and Technology Committee earlier this year. Moreover, we believe this compromise helps move the discussion about the future of NASA closer to a final product.”

Gordon’s revised legislation, which aides said could go to the House floor this week as a substitute to H.R. 5781, increases proposed funding levels for NASA commercial crew taxis to $1.2 billion over three years. That figure is still $400 million shy of the Senate’s $1.6 billion recommendation for commercial crew and cargo initiatives, but represents a sizeable increase over the original $464 million through 2013 recommended in H.R. 5781.

Gordon’s substitute legislation also calls for initiating a robotic precursor program in 2011, recommending $50 million annually through 2013. The earlier House proposal sought to delay funding for robotic precursor missions, calling for just $5 million in 2013 to initiate the program.

The revised bill also directs NASA to begin planning a new space launch system for exploration beyond low Earth orbit that by the end of 2016 can provide “assured government back-up access” to the international space station should commercial cargo or crew services be unavailable. However, the new language would prevent the government-owned capability from competing with commercial space providers for routine cargo and crew delivery services.

Although the revised House bill puts no timetable on developing the heavy-lift capability for missions beyond the space station, it calls for the new exploration architecture to “provide a scalable capability of lifting payloads of at least 130 metric tons into low Earth orbit on a single launch vehicle with an upper stage in preparation for transit for missions beyond low-Earth orbit.” It also directs NASA to leverage space shuttle technologies as well as its $10 billion investment in the Moon-bound Constellation program the White House seeks to abandon.

The Senate’s version of the NASA authorization bill, S. 3729, calls for starting development in 2011 of a space shuttle-derived launcher initially capable of lifting between 70 metric tons and 100 metric tons to low Earth orbit by the end of 2016. The Senate language directs that the vehicle be designed to accommodate upgrades that would enable it to deliver 130 metric tons to orbit.

Gordon’s original bill called for funding a government-owned rocket and spacecraft capable of delivering astronauts to the space station by the end of 2015.

The revised House language authorizes the additional launch-on-need shuttle flight adopted in the Senate bill and calls for $2.67 billion for NASA’s proposed space technology program, including $1.9 billion over three years for exploration technology development. It also authorizes $45 million through 2013 for a commercial suborbital research program involving reusable rockets to support science, technology development and education, according to the bill summary.