WASHINGTON — While NASA argues there is a growing consensus that the agency’s long-term human spaceflight goal should be landing people on Mars, a recent conference suggested there is less agreement about exactly how NASA should accomplish that goal.
Speaking at the Humans To Mars Summit here May 5, NASA Administrator Charles Bolden argued there was now widespread agreement with NASA’s plans to send humans to Mars as soon as the 2030s, a goal established by President Obama in an April 2010 speech.
“There is a new consensus that’s emerging around this timetable and around this goal,” Bolden said. “There is also a consensus emerging around NASA’s plan for going there. This plan is clear, this plan is affordable, and this plan is sustainable.”
Few attendees of the three-day conference, organized by the advocacy group Explore Mars, Inc., disagreed with the overall goal. There was less evidence of consensus, though, about how to accomplish it.
NASA has been deliberately vague about how it intends to send humans to Mars. Agency officials said earlier this year it would be some time before they would be ready to revise the latest detailed Mars mission architecture, last updated in 2009.
NASA has talked about performing human missions in cislunar space, which the agency has dubbed the “proving ground,” to gain experience before human missions to Mars. However, NASA hasn’t discussed specific missions beyond a potential crewed mission in the mid-2020s to an asteroid redirected into lunar orbit as part of the Asteroid Redirect Mission.
“NASA does not have any official plan beyond 2021,” said Josh Hopkins, a Lockheed Martin space exploration architect, during a conference session May 6.
Some in Congress have become impatient with NASA’s lack of specifics. Several versions of NASA authorization legislation in the House, including one approved by the House Science Committee April 30, would require NASA to develop and regularly update a “roadmap” for human missions to Mars’ surface.
The Senate has yet to take up those bills or develop their own, but one staff member said there’s a similar desire there for a long-term Mars exploration strategy. “I do think there’s a lot of interest in doing something,” said Nick Cummings of the Senate Commerce Committee in a May 5 conference talk, although he added the Senate might seek that information through a series of hearings rather than a formal report.
There is, however, no shortage of ideas of how to carry out those missions. “We don’t lack for architectures,” said Firouz Naderi, director of the Jet Propulsion Laboratory’s Solar System Exploration Directorate, in a conference presentation May 6. “There are quite a few of them out there. So, do we really need another one?”
Naderi and his team think so. At the conference, they discussed a plan for human Mars exploration they recently developed that they conclude would allow for a human mission to the Martian moon of Phobos in 2033 and a landing on Mars in 2039. That concept, they argued, could fit into NASA’s existing budget for human spaceflight, provided that budget kept pace with inflation.
“We’re going to do it in an architecture that is as simple as necessary,” Naderi said. That included, he said, minimizing the number of components of the mission plans, and avoiding the use of so-called “exotic technology,” like nuclear thermal propulsion.
The human mission to Phobos requires four SLS launches spread out over several years, according to the JPL’s Hoppy Price, the chief architect of the plan. The first SLS would launch a tug, propelled by solar electric propulsion (SEP), to send transfer stages on a multi-year trip to Mars orbit. A second SLS would also carry a SEP tug to send a habitat module to land on the surface of Phobos.
A third SLS launch would place into Earth orbit a habitat module and a Mars orbit insertion stage. The final SLS, launched shortly after the habitat module, carries an Orion spacecraft with a four-person crew and an upper stage. After the Orion docks with the habitat module, its upper stage sends the spacecraft “stack” to Mars.
Once in Mars orbit, the Orion undocks from the habitat and docks with a transfer stage to take it to Phobos, where it docks with the Phobos habitat. The crew would remain there for 300 days before flying back to the habitat module, attached to another transfer stage for the return to Earth.
A similar approach could be used for a “short-stay” Mars landing mission, where a two-person crew would spend about three weeks on the Martian surface. That mission concept requires six SLS launches to accommodate the lander and additional transfer stages.
JPL asked the Aerospace Corp., which performed cost estimates of Mars mission architectures in a National Research Council human spaceflight report published last year, to do a similar “sanity check” on their plan, said JPL’s John Baker. That analysis found the program fit within an inflation-adjusted NASA budget if the International Space Station is retired in 2024, and fits except for a small peak in latter half of the 2020s if the ISS is extended to 2028.
“In conclusion, we believe that Mars is possible and in a time horizon of interest,” Baker said, provided there is a “clearly articulated” strategy and a budget adjusted for inflation.
Naderi said his presentation was the first time the concept was publicly presented, although it was briefed to participants of the invitation-only Humans Orbiting Mars workshop here a month ago. He said after his talk that his team has started a second study to refine the concept.
Baker acknowledged that this concept is not the final word on human Mars exploration. “We know that what we’re showing you here is not what ultimately is going to fly to Mars,” he said. “There will be lots of incarnations and lots of iterations.”
While there is no consensus now on adopting either JPL’s approach or an alternative model for sending humans to Mars, one expert believes there’s a limited time to adopt one, even though such missions are two decades into the future.
“I think we have a window of opportunity to build a consensus for a long-term, cost-constrained, executable humans to Mars program,” said Scott Hubbard, a professor of aeronautics and astronautics at Stanford Univeristy and former director of NASA’s Mars exploration program.
Hubbard cited, as evidence of that window, increased public interest in Mars exploration along with the opportunities presented by international cooperation and the growing capabilities of commercial ventures. However, he warned that window of opportunity could close if the Mars exploration community doesn’t develop a credible approach in the near future.
“If you don’t have a plan to use that funding that is clear and is costed and is executable,” he warned, “other people will make demands for that funding and we will once again be 30 years away from humans on Mars.”