This article was originally published in the December 17, 2018, issue of SpaceNews.
Sometime in 2028, competing for attention alongside a presidential election and the return of the Summer Olympics to Los Angeles, NASA will return humans to the surface of the moon.
A lunar landing module will exit the cluster of modules in an elliptical orbit around the moon, called Gateway, and descend. One stage will take the module to a low lunar orbit and then separate, after which the descent module will handle the rest of the journey to the lunar surface. A team of up to four people will spend days – perhaps up to two weeks – on the surface before boarding the uplift module, which will take them back to the Gateway.
At least that's NASA's plan for now. One year after President Donald Trump formally ordered NASA to return humans to the Moon in the SPD 1, the agency developed the outlines of a plan to implement it, emphasizing the language of policy to do so it. "Sustainable" and with international and commercial partners. But as the agency describes two of the plan's major elements, the Gateway and a "human-class" lunar landing module are still struggling to sell the proposal to its various stakeholders, including its own consultants.
Three phases for the moon
When NASA began implementing SPD-1, it made use of something it had already proposed: a Cislunar habitat called the Deep Space Gateway. Under previous plans by the Journey to Mars agency, Deep Space Gateway intended to test technologies needed for future human space missions, including proposed Mars expeditions to the 2030s. After the SPD-1 came into force, Deep Space Gateway was renamed Lunar Orbiting Platform-Gateway, which is somewhat cumbersome, focusing on supporting the robotic and human exploration of the moon. (Today, NASA simply refers to the facility as the Gateway.)
But while the Portal could be reused to support the human exploration of the moon, NASA could not get to the surface. Internally, the agency began to study concepts for lunar system designs and put efforts in motion to solicit industry proposals to study how to get the astronauts out of the Portal.
There was no shortage of ideas. For example, Lockheed Martin unveiled in October its concept of a large lunar module based on previously developed designs for Mars. Its lunar landing module was a single-stage vehicle, capable of leaving the Portal to the Moon and returning without discarding the stages. The company envisioned a propellant deposit in the same orbit as the Portal – eventually using water obtained from lunar ice deposits converted into liquid hydrogen and oxygen – to replenish the module.
Lockheed's concept was great: 62 tons when fully fueled and 22 tons when empty. The vehicle was 14 meters high, requiring astronauts in the habitat module at the top of the probe to use what the company called a "simple platform lift" to reach the surface.
NASA, however, is moving in a different direction. Even at its best, a single stage lunar module would weigh about 50 full metric tons, said Jason Crusan, director of NASA's Advanced Exploration Systems division, in a December 7 presentation to the Council's Human Exploration and Operations Committee Advisory Board of NASA (NAC).
"If you made a single-stage landing, there is not a launch vehicle that he can fit in," he said. Even the future version of the 1B Block Release System, he said, can only put 45 metric tons on a trajectory to the moon.
A two-stage approach, consisting of a descent module and a rise module, would still require the descent module to weigh between 32 and 38 metric tons. That could fit into an SLS, noted Crusan, but there are no other vehicles that exist now or that NASA expects to be available in the near future. However, the uphill module, weighing from 9 to 12 tonnes, could fit in several commercially available vehicles.
What NASA now considers the best option for a lunar landing module is a three-stage approach, which adds a transfer vehicle beyond the rise and fall modules. "By going into this three-stage architecture, it opens up much more commercial space," Crusan said. That means more flexibility in how each step, now small enough to fit in commercial vehicles or be co-manifested in SLS / Orion missions, hits the moon.
However, they arrive there, the three stages would be integrated in the Gateway, with the astronauts embarking in the lander there. The transfer vehicle would take the probe from the Gateway's nearly rectilinear halo orbit, an elliptical orbit somewhere between 1,000 and 70,000 kilometers above the moon, to a low circular orbit perhaps 100 kilometers high. The up and down stages descended to the lunar surface, and at the end of the mission, the rise stage would fire its engines to return directly to the Portal.
This approach would allow the uplift stage and the transfer vehicle to be reusable, another selling point for the overall architecture. The descent stage would be left behind on the moon, so a new one would be needed for each mission. But Bill Gerstenmaier, NASA's associate administrator for human exploration and operations, suggested that uplink engines could also be used for landing. "All you are using for the descent vehicle are the propellant tanks," he told a meeting of NASA's Advisory Council on Dec. 10.
Crusan said an effort to solicit studies of the lunar concept sector, once planned for the summer but suspended as the agency refined its thinking on lunar platforms, could be restarted by the end of the year. "We want industry studies to be conducted as quickly as possible," he said.
At that meeting of the human operations and exploration committee, some members wondered why the lunar module, even the three-stage concept currently preferred by NASA, required the use of the Gateway. The landing elements could not dock and then meet an Orion spacecraft without the need for the Gateway, one person asked.
"Gateway offers a safe haven capacity for us," Gerstenmaier told the committee on Dec. 6. "Gateway is also providing a meeting destination, so there is no critical time associated with those three elements that come together. They can be launched months apart, years apart. "
The committee, however, is not the only group raising questions about Gateway or NASA's global lunar plans. At a meeting of the National Space Council (UAG) Users Advisory Group on November 15 at NASA headquarters, Tom Cremins, an associate director of strategy and plans, gave an overview of what NASA planned to accomplish by 2028 under its architecture operation. bulleted list that included human landing on the moon.
This approach was very slow for some members of the advisory group. "Personally, I think 2028 for humans on the moon 10 years from now. It looks like it's so far away, "said Eileen Collins, a former astronaut. "We can do this sooner."
"This does not seem to have a sense of urgency," said Harrison Schmitt, an Apollo 17 astronaut. "I think there should be a sense of urgency."
Some members of the advisory group have focused their criticisms on the Portal itself. "Why would you want to send a team to an intermediate point in space, get a probe there and get off?" Asked Buzz Aldrin, who called the Gateway concept "nonsense."
Later that day, Mike Griffin, the former NASA administrator, spoke to the UAG. While he was there in his current position as undersecretary of defense for research and engineering, committee members could not resist asking for his thoughts on NASA's plans, knowing his reputation for speaking his mind.
Griffin lived up to that reputation. "I think 2028 is so late to need or be worthy to be on the table," he said, emphasizing that he was offering his personal opinion. "The architecture that was put into play, putting a Gateway before the boots on the moon, is from the point of a space systems engineer – that was the only thing in life I've ever been good at – a stupid architecture."
The Portal, he said, would only be useful when there were installations on the moon producing propellant that could be transported to the Portal, now serving as a warehouse. "We must be, with all deliberate speed, returning to the Moon and learning to utilize the resources of our object closest to Earth's orbit. In my opinion."
Despite criticism at the meeting of members and guests, UAG members said they were not necessarily opposed to the Portal itself. "There were some difficult questions" about Gateway, said Eric Stallmer, president of the Space Flight Federation and a member of the group, during a panel session at the SpaceCom Expo conference in Houston on 28 November. slideware. We want to see more hardware.
But, they later asked if Gateway was the right plan for NASA, Stallmer and other UAG members on the panel were punished. "That's not for us to decide," he said.
"My personal opinion is that I do not know," said former astronaut Pam Melroy. "I do not feel like I have enough information to know if it's the right thing or not."
Even the proponents of the Gateway struggled to reach out to outlets for it. During the NAC's human operations and operations committee meeting, members who said they liked the Gateway struggled to craft reasonings that could be easily understood outside the agency.
Ken Bowersox, chairman of the committee, offered an explanation of how the Gateway helped NASA prepare for exploration beyond the moon, even if it was not the most efficient way to get to the moon. "But just trying to do that, I spent 30 seconds, "he said after spending about a minute describing. "I've already lost half the people I try to talk to."
"Gateway is not a very short sound," Crusan said. "The value of building critical infrastructure off the planet is not something you can explain in two or three sentences."
When the NASA Advisory Committee met at NASA headquarters on Dec. 10, the agency's leadership went to the offensive to create support for Gateway, emphasizing sustainability over time.
"There have been some criticisms of the Gateway," acknowledged NASA administrator Jim Bridenstine. "What we are doing here at NASA is following Space Policy Directive 1" and its emphasis on sustainability and partnerships, he argued. In this approach, the Gateway becomes a "reusable command module" that directs activities on the lunar surface. "The Gateway glory is that it's this command module."
Gerstenmaier showed a chart later in the meeting comparing Gateway's approach to the "Apollo-style" alternative to go directly to the moon. The latter approach, he argued, lacks reuse and does not build infrastructure that can make that exploration more sustainable. It also limited opportunities for international and commercial partnerships.
"Depending on who you're talking to, they think it can be done faster," he said of a direct return to the moon that does not develop a Portal. Gateway's advantage, he said, was its sustainability and flexibility. "It is seen as not ideal for any specific location on the Moon, but gives the entire lunar surface to you."
"There are people who say we need to get there, and we need to get there tomorrow," Bridenstine said of those pushing for an immediate and direct return to the moon. "I'd say we got there in 1969. This race is over and we won. The time is now to build a sustainable and reusable architecture. "
This approach, he said, would allow the US to return to the moon with international and commercial partners. "The next time we go to the moon, we will have American boots on the moon with the American flag on their shoulders, and they will stand side by side with our international partners who have never been to the moon before," he said. "That's the American leadership."
As the board meeting progressed, members suggested possible additional studies for the Gateway concept, perhaps in cooperation with the National Academies or with the UAG of the National Space Council. "It would be wise to maybe convene a workshop – perhaps the National Academies or someone else – in a short time, where people will stand or fall silent on coherent alternative plans?" Asked Alan Epstein, representing the National Academy of Aeronautics and Space at the Academy. Edge.
Bowersox, however, noted that his committee, having plunged into technical training on its attributes, liked the idea of the Portal. "I tried to encourage someone to say no," he said of their deliberations. "I could not get anyone."
As Bowersox put it during his committee's previous meeting, "It takes time to grow in you."