On Tuesday, hundreds of Mars enthusiasts are gathering in Washington, DC to celebrate the red planet at the annual Humans to Mars conference. Buzz Aldrin will discuss his “cycler” plan for going to Mars. Andy Weir, author of The Martian, will be on hand to sign books and talk about his vision for Mars exploration. And representing NASA by giving the plenary speech, NASA Deputy Administrator Dava Newman will update the gathering about the Journey to Mars.

Since the conference is more or less a conclave of Mars devotees, there will probably be few hard questions asked about the feasibility of NASA's plans. But those hard questions are coming, and it’s not clear that NASA has the answers. Although space has not been an issue in the presidential election, whether a Republican or Democrat is elected this fall, a transition team will review the panoply of government spending, including NASA’s human exploration programs. Among those questions that will be asked are these: What is the plan for NASA to get to Mars? And can the space agency make it there within a reasonable budget?

In late April, Newman was asked these very questions at a meeting of the Federal Aviation Administration’s Commercial Space Transportation Advisory Committee. The FAA regulates commercial space launches, and Newman had given the standard speech about NASA’s activities. During a Q&A period, Newman took a question from Jeff Greason, a rocket scientist who founded XCOR and is now a consultant with Agile Aero, about the viability of the Mars plan.

The question was not in any way malicious. Rather, Greason is well steeped in both the aerospace and political challenges facing NASA as the agency seeks to extend the human presence in the solar system. In 2009, after President Obama came into office, Greason served on the blue-ribbon Augustine committee that reviewed NASA’s activities. At the end of its deliberations, the committee urged the president and Congress to give NASA a clear human spaceflight goal and funding to achieve that goal.

Since 2009, Greason has watched with dismay as DC has put NASA on a “Journey to Mars.” To be clear, this is an ambitious goal worthy of a great nation. The problem is that Washington has not provided the funding to carry out those goals, and it has played politics with the funding it has provided. With his question, Greason wanted Newman to explain more about the plan because, in his words, ”I have not yet seen a plan. There are a lot of slides, but in terms of how we might actually get all the way to boots on the ground, with a series of steps that fits within some kind of budget wedge, I haven’t seen that.”

Newman’s answer to Greason, transcribed below, is worth reading in full:

OK, well, download the October 2015 is our plan. So download that one. That’s where to start. And that’s the high level. That is the high-level plan. But it has details in there. And after that, since there’s all three phases—space station, cislunar, and Mars—then right now what we’re working, if you go one level deeper, that’s our Evolvable Mars campaign. And what we’re really working right now is the cislunar piece to put, you know, more substance, more meat on the bones. We get there first. Mars orbit, Mars surface—those are a little bit further down the road. So we really know what we’re doing in low-Earth orbit, that’s a lot of... that’s what we’re working right now. So two things to kind of take a look at—please read it. If everyone’s read it and looked at all the details, then you—OK, we can have a conversation, then you can criticize. But we do have a plan and a strategy—and do read it. And we’d love to discuss it with everyone as well. It’s my job to get out here and communicate it, make sure it’s clear, and hopefully we’ve been doing it a little bit differently. The horizon goal is Mars. Let’s get there, then kind of back it out. What are the requirements? And then let’s back that out and talk about it in our three phases so that we can be as concrete and as clear as possible. It does have some flexible architecture in there. That bothers some people; it doesn’t bother me at all. I’m a systems engineer. But again, so those are the things we can engage in and discuss in terms of some flexibility in the architecture. It’s not a point solution. It’s not a point source design. And no, we’re not telling you where we’re going because, actually, the world—a lot of people, we get data every day from, you know, Curiosity and Maven, and so I’m not going to tell you exactly where we are going to land on Mars. We had a great workshop, right? We opened it up to bring engineers and scientists together to start talking about that a lot. So there are things that are evolving, of course, as they should. So we can be as well informed as we can about some of those things, some of those details. Thank you very much, though.

There's no question that Dava Newman is a very smart person. She is a highly respected scientist who was a professor of aeronautics and astronautics at the Massachusetts Institute of Technology before coming to NASA. She also is not entirely new to the job as deputy administrator, having been with the agency for a year as of May 15. So it's difficult to explain her meandering response to a straightforward, valid question.

These are questions NASA ought to be striving to clearly answer, because they’re exactly the kinds of things a presidential transition team will be asking about at the end of this year. It is one thing to bluff the media and hold NASA “social” events where space enthusiasts are shown hardware and dazzled by astronauts and senior NASA scientists. Newman also will undoubtedly get a rousing roar of approval after her speech to the Humans to Mars conference today.

But it is quite another to explain plans, gap analyses, and budgets to aerospace officials. It is not inconceivable that Greason will be back, in some capacity, to review NASA’s Journey to Mars for the next presidential administration. And if not him, there will be others in the aerospace industry skeptical about the “meat on the bones” of NASA’s Journey to Mars.

The plan isn’t much of a plan

Greason had, in fact, seen the documents (the October 2015 plan and Evolvable Mars Campaign ) to which Newman referred in her response. Nonetheless, he went back and reviewed them after a request from Ars. “The basic problem is not that this is a good plan or a bad plan but that it really lacks many of the elements a plan would contain,” Greason concluded. “ As a result, I am left with more questions than answers.”

Greason said the documents do not make it clear what the overall goal of the Journey to Mars is: Flags and footprints? A base? Human settlement? “If you don't know why we're doing it, it's hard to know whether it is worth doing,” he said.

The plan also does not specify the research and development funding needed to address the current gaps in knowledge required to get to Mars. For example, a variable-gravity research facility in low-Earth orbit and some kind of facility for long-term exposure of biological specimens in cislunar space would probably prove useful. Laying out these gaps now would drive procurements and budget requests, he said.

Greason agreed with Newman that it was not a defect of the plan that it had not yet identified an exact destination or mission architecture. At a similar point in the Apollo planning, for example, architectures for reaching the Moon included direct ascent and Earth-orbit rendezvous. A lunar orbit rendezvous wasn't even in the trade space. “But a plan would at this point have the expected alternative architectures laid out so they could be traded," he said. "There are many ways to get to Mars, and we probably need added R&D to pick which one or ones are viable within budget limits.”

It's worthy for NASA to be thinking about going to Mars. It's great that there is a passionate group of people gathering in Washington, DC to share their enthusiasm for the red planet this week. But if we want NASA landings on Mars to be more than the stuff of science fiction, the space agency had better figure out how to credibly explain all of this to transition teams this fall.