A letter to President Obama from a bipartisan group of 62 members of the U.S. House of Representatives proposes a compromise plan to immediately develop a heavy-lift rocket, saying it would preserve jobs and America's leadership in human spaceflight.

NASA hopes to develop a heavy-lift rocket with a new first stage engine at least half the size of the F-1 engine, which powered the Saturn 5 rocket on moon missions. This file photo shows an F-1 engine in ground testing in the 1960s. Credit: NASA/MSFC

The letter, dated June 22, calls for NASA to start developing a new heavy-lift propulsion system immediately, leveraging five years of work and $10 billion invested in the Constellation program before President Obama ordered its cancellation earlier this year.

"We support the immediate development and production of a heavy-lift launch vehicle that, in conjunction with the Orion Crew Exploration Vehicle, may be used for either lunar or deep-space exploration to an asteriod and beyond, as you said in Florida," the lawmakers wrote to President Obama.

During a visit to the Kennedy Space Center in April, the president unveiled plans to select a heavy-lift rocket design by 2015, leading to human expeditions to asteroids in the 2020s and eventually Mars as soon as the 2030s. President Obama also used the speech to announce the Orion capsule, originally designed to go to the moon, would be a lifeboat for the International Space Station.

Both announcements came after members of Congress criticized the Obama administration's NASA policy, which initially contained no timetable for human exploration beyond low Earth orbit and completely scrapped the Orion capsule.

Heavy-lift rockets are a critical piece for any space exploration architecture beyond Earth orbit.

"I urge the president to embrace these core principles to ensure continued U.S. leadership in space," said Rep. Frank Wolf, R-Va., the ranking member of the House Appropriations Committee's subcommittee overseeing NASA. "The immediate development of a heavy-lift rocket and crew capsule to take American astronauts beyond low Earth orbit is something that all supporters of NASA can unite behind."

Tuesday's letter, heralded as a compromise by its signers, indicates there is still considerable bipartisan concern over the White House's plans for NASA.

"We hope the administration is willing to work with us on the compromise," said Rep. Gene Green, a Democrat from Houston. "It is an important step in ensuring we save our valuable workforce and keeps America as the leader in space exploration."

Signed by 37 House Republicans and 25 Democrats representing 18 states, the letter says expediting the design and development of a heavy-lift rocket would save jobs, capitalize on lessons learned in the Constellation program, and ensure the country remains at the forefront of space exploration.

Artist's concept of the Ares 5 rocket, the heavy-lift rocket of the Constellation program. Credit: NASA/MSFC

"This would provide operational flexibility while ensuring our taxpayers' investments have not been made in vain," the representatives wrote.

The lawmakers claim a heavy-lift rocket could be ready within six years with no increase to NASA's exploration topline budget.

"With no significant technological breakthroughs on the horizon in regard to heavy-lift propulsion needs, we see no reason to prolong a decision that will result in the loss of a highly-experienced and motivated workforce," the lawmakers wrote.

NASA is already seeking advice from industry on heavy-lift rocket concepts. The next-generation launcher would likely be powered by a massive kerosene-fueled rocket engine, but other options are still on the table.

Sen. Bill Nelson, D-Fla., wants to continue development and testing of the solid-fueled Ares rocket, which he says is key to keeping skilled defense workers employed. The Ares 1 and Ares 5 rockets, which would burn solid and hydrogen propellants, would be shelved under Obama's plan.

Tuesday's letter did not mention commercial crew transportation to low Earth orbit, another major policy shift under President Obama's budget request.