WASHINGTON — Human missions to Mars are possible in the 2030s without significant increases to NASA’s current budget, according to an internal Jet Propulsion Laboratory study discussed at a recent closed-door workshop here.

The study, not yet publicly released, found that with the development of a few key technologies, including some NASA is already pursuing, the space agency could carry out a human mission to orbit Mars in 2033 and a Mars landing mission as soon as 2039.

A cost estimate prepared for JPL by the Aerospace Corp. of El Segundo, California, found that those Mars missions, as well as a series of precursor missions in cislunar space, could be done within NASA’s current budget plus increases for inflation, provided NASA ended its participation in the International Space Station in 2024.

“Not only did we see a reasonable example of a series of missions that would enable humans to get out to Mars, we saw the cost analysis,” Bill Nye, chief executive of the Planetary Society in Pasadena, California, said in an April 2 briefing here about the workshop. “There’s no ‘Kennedy moment’ involved, there’s no extraordinary demand for doubling of the NASA budget.”

The JPL study was discussed at the “Humans Orbiting Mars” workshop held by the Planetary Society at George Washington University March 31 and April 1, marking the first time it was formally discussed outside of the group who developed it. The invitation-only meeting brought together people from NASA, industry, and other organizations to discuss the proposal and how to implement it.

Stanford University professor Scott Hubbard, who chaired the workshop, said the study was a response both to NASA’s current Mars exploration plans and a report on the topic by a National Research Council (NRC) committee published last year. NASA’s plans, he said, lacked clarity, while the NRC report required unrealistic budget increases to get to Mars before midcentury. “Neither of those answers were acceptable,” he said.

Hubbard and other workshop participants declined to offer many details about the study, saying the report would not be ready for public release until later this year. However, based on the broad outlines discussed here, the concept makes use of both the Space Launch System heavy-lift rocket and the Orion spacecraft currently under development by NASA.

After the initial series of SLS/Orion missions already planned by NASA, the concept would feature crewed “Mars sims” — or simulations — in cislunar space in 2025 and 2027. Those missions would test technologies needed for the Mars missions, including a habitat module and solar electric propulsion. Robotic missions around the same time would test entry, descent and landing technology for future Mars landers.

That would be followed in 2033 by the launch of a human mission to Mars orbit. That spacecraft would remain in Mars orbit for a year, possibly landing on either or both of the planet’s moons, but not on Mars itself. A crewed “short stay” mission to the surface of Mars would follow in 2039.

The architecture does not make explicit use of NASA’s Asteroid Redirect Mission (ARM), which the agency has pitched as its next major step towards a human Mars mission. However, workshop co-chairman John Logsdon, director emeritus of George Washington University’s Space Policy Institute, said that ARM will demonstrate some technologies, most notably solar electric propulsion, that are needed in this approach.

“If one doesn’t do ARM, that system will have to be developed anyway,” Logsdon said of solar electric propulsion. “Given what NASA is allowed and not allowed to say about its long-term plans, ARM is the best mission NASA can come up with in the current context.”

Hubbard said that to meet the schedule laid out in the study, NASA would have to adopt the overall framework as soon as possible. “It’s not too early to start,” he said. “I would encourage the administration and Congress to think about this strategic framework in the current budget cycle.”

Logsdon, though, acknowledged that it is unlikely that the Obama administration will adopt this architecture or any alternative to its current approach during its remaining time in office. “It really is an issue for the next president,” he said.

Nye said the Planetary Society would continue to discuss this concept as part of a renewed interest in human spaceflight by the organization, best known for promoting robotic exploration of the solar system.

“When I first took this job, I was under a lot of pressure to criticize the Space Launch System,” Nye said. “But it’s in the works, and the people doing it seem to know what they’re doing, and it really would be a great thing.”

Nye stopped short of formally endorsing the JPL study, but suggested his organization’s willingness to sponsor a workshop to discuss it was evidence that he felt it was worth pursuing. “I say this about the Planetary Society: We are not crazy. We are not pie in the sky,” he said. “You’ve got to do what’s possible within the budget that’s possible.”