SEATTLE — NASA has signed a deal with Alliant Techsystems (ATK), the company that provided the space shuttle fleet’s solid-rocket boosters, to help develop a new vehicle that could launch astronauts into orbit by 2015, the space agency announced Sept. 13.

The new NASA deal with Utah-based ATK is an unfunded Space Act Agreement to work together on the company’s Liberty rocket. While NASA will not give ATK any money in the deal, the agency will provide expertise that could help ready the rocket for operational flights in the next four years, officials said.

“This agreement will provide the opportunity to look at the Liberty system to understand its design solution and risks, its capabilities and how it could be used to fly our NASA crew,” Ed Mango, NASA’s commercial crew program manager, said in a statement.

Under the agreement, which runs through next spring, 12 to 24 full-time NASA employees will help assess and develop Liberty, Mango told reporters Sept. 13.

For 30 years, ATK provided the reusable twin solid-rocket boosters that launched NASA’s space shuttles to low Earth orbit.

The company also was tapped to develop the first stage of NASA’s Ares 1 rocket, which would have launched astronauts under the agency’s Moon-oriented Constellation program. The engine the company built is similar to the shuttle’s boosters, officials said.

The Ares 1 project was scrapped when President Barack Obama canceled Constellation last year  and directed NASA to work toward getting humans to an asteroid by 2025. But ATK is not letting the work it did for Ares 1 go to waste. The company has teamed up with the European aerospace firm Astrium to build Liberty. The rocket will incorporate the Ares 1 engine as a first stage and Astrium’s Ariane 5 rocket as a second stage.

Liberty will stand about 91 meters tall, and will be able to launch payloads of up to 20,185 kilograms, ATK officials have said.

ATK and Astrium hope that NASA eventually selects Liberty to launch its crews to low Earth orbit. Under its Commercial Crew Development (CCDev) program, the space agency is seeking to spur the capabilities of U.S. private spaceflight companies.

After the retirement of NASA’s space shuttle program in July, NASA became dependent on Russian Soyuz vehicles to ferry astronauts to and from the international space station. CCDev aims to shift this taxi role to private companies by the middle of the decade.

A number of private spaceflight firms are hoping to score deals with NASA to transport its astronauts. The space agency has granted a handful of them development money in the last several years during two rounds of CCDev funding.

ATK and Astrium put Liberty forward for the second round of funding, announced this past April. The rocket did not get any money. But the Space Act Agreement announced Sept. 13 shows that NASA is still interested in helping Liberty along, Mango said.

The overall aim of CCDev, he added, is to help develop several different viable U.S.-led systems that could launch NASA astronauts to space.

“We’re very interested in helping ATK and their partners,” Mango said. “We encourage them to go work with spacecraft providers, create those partnerships and then come forward and say now they have a solution.”

Though the Ariane 5 currently launches unmanned payloads, both components of Liberty were designed with a crew-carrying capability in mind, ATK officials said. That should give the rocket a leg up on other launch vehicles hoping to score a NASA crew-carrying contract, they said.

“I believe that we are ahead of all systems, so we can be ready when the space vehicles are ready to fly,” said Kent Rominger, vice president of strategy and business development at ATK.

Several different aerospace firms are developing crew-carrying spacecraft. Rominger said ATK is in discussion with many companies about providing their launch services.

“We’re talking to everybody that we can,” Rominger said. “We’ve had a real good reception from the folks out there.”

Rominger estimated that Liberty could begin crew-carrying operations by 2015. The rocket also could be used to launch satellites and other unmanned cargo, he said.