A team of Purdue students has produced a feasibility study about a plan proposed by former NASA astronaut Buzz Aldrin to create a new class of spacecraft that could enable humans to travel routinely in space and colonize Mars.

Aldrin, the second human to walk on the Moon, is proposing an approach hinging on new spacecraft that would perpetually cruise between Earth and Mars. The “cycler” vehicles would ferry people and materials between the two planets, enabling earthlings to explore, commercially develop, and eventually colonize the red planet.

The plan was outlined in a 2013 book by Aldrin that envisions human colonization in steps, first developing an infrastructure of spacecraft and other hardware and eventually sending people to the Martian moon Phobos before colonizing Mars.

“Dr. Aldrin’s plan is very ambitious but doesn’t really have a lot of numbers: How much does everything weigh? How many rocket boosters are you going to need? How much food will you need? The technical details, the numerical results. That’s what I asked my design team to figure out,” says James Longuski, professor of aeronautics and astronautics.

The findings are detailed in a 1,068-page report and also described in a film, both produced by the students and posted online at https://engineering.purdue.edu/AAE/Academics/Courses/aae450/2015/spring. The team of 51 students completed the project while taking a senior design course, AAE 450, or Spacecraft Design.

“It’s a life-changing experience to work on something like this,” says Stephen Whitnah, a senior and the team’s project manager. “In the end it was a student-run and -directed project, which is one of the most important takeaways. Everyone was really dedicated to this project.”

Tom Shih, professor and head of the School of Aeronautics and Astronautics, says: “The human spirit is such that people do have dreams of understanding more about the universe. I think this opportunity to work with Buzz Aldrin and his vision is something that excites our students, it’s something that inspires our students, and so I think it is a great opportunity for them.”

Incremental steps

Aldrin’s plan calls for a gradual development of infrastructure and experience in space, eventually sending 18 people every two years for the next several cycles to build up a large colony on Mars.

Longuski says, “In order to be ready to go to Mars, we need more experience in space, we need to test things out in low Earth orbit. Then, we want to go to an asteroid, places near the Earth’s moon, the so-called Lagrange points, and from there go on to Phobos and to Mars.” The timeline calls for a colony on Phobos by 2038 and on Mars by 2040.

Whitnah says, “Humans have done a lot of research in low Earth orbit and now we have to move up to the moon and Mars. But this time we go to stay. We want to establish a continuing, permanent presence, which I think is the important thing.”

The team was broken into disciplinary specialities such as propulsion, mission design, communications, aerodynamics and structures.

Advisor and doctoral student Sarag Saikia said the space program and other ambitious big-science projects help to inspire the next generation of researchers.

“The students learned many lessons about how to work as a team. And these are lessons that apply to any big engineering project,” Saikia says.

Teaching assistant and doctoral student Peter Edelman says the student team worked unusually well together, avoiding the usual interpersonal conflicts that often bedevil large teams.

“This is probably the biggest senior design course that Purdue has ever had, and I was very impressed with how they worked together,” Edelman says. “It was a daunting assignment. All the different groups had to collaborate in order to succeed, and they did a very good job. In one semester they wrote a giant, 1,000-page report and they produced a great movie.”

The findings were presented to Adrin at an April 23 Purdue event. Aldrin told the team he was impressed with the way they worked out the specifications. “The way things were organized to carry those out to conclusions went considerably beyond my ability to look at the details,” he told the team. “I’m learning quite a bit from what you have done.”

Exploring economies

Findings showed the plan will have to be scaled down for it to be economically feasible.

“It’s a very aggressive program,” Longuski says. “If you compared it to the Apollo moon program, it’s about three Apollo programs in terms of expense.”

Current NASA funding amounts to about one-quarter the size of the Apollo program.

“So, it would probably be economically unfeasible,” Longuski says. “I think what we should do next is go back and rescale the problem, bring it down to a level that is economically feasible. We’ve learned all of the right issues, so changing the specifications is not going to be difficult for us to accomplish.”

Related research at Purdue is ongoing

“We will continue to do research in this area at the doctoral level,” Saikia says. “We are not interested only in Dr. Aldrin’s plan. We are interested in all plans that have been proposed, and we can incorporate all the concepts and technologies that will help evolve the plan to go to Mars. And Dr. Aldrin’s plan is one of the best.”

Longuski and Aldrin have a history of working together that goes back to the 1980s. They met when Longuski was working at the Jet Propulsion Lab in Pasadena, California.

“He came there to try out a new idea of putting spacecraft in orbit around the sun and it would visit the Earth and Mars but without stopping at either,” Longuski says. “He wanted to know how the numbers worked on that. I was working on mission design and knew how to do these kinds of calculations. I worked out the basics of how the Aldrin cycler works and my colleague at JPL, Dennis Byrnes, worked out the optimal solution of how that’s all done.”

The three authored a paper on the research that was published in 1993 in the Journal of Spacecraft and Rockets.

“We have continued to work together over the years and now Dr. Aldrin is working very closely with me, my research group and my senior design team,” Longuski says.

Cyclers would take advantage of the gravitational forces that are exerted by the sun, the planets and their moons, which provide “gravity assists” to passing spacecraft. As a spacecraft travels close to a planet, its flight path is bent, causing it to whip around the planet while boosting its speed. The path is commonly called a “slingshot” trajectory, which enables a spacecraft to achieve the proper speed and heading.

The cycler spacecraft would have to encounter Mars and Earth at precisely the right distance and speed. If a cycler approached Mars too fast or at the wrong distance, too much propellant would be needed for steering rockets and it would be more difficult for “taxi” spacecraft to dock with the cyclers as they sped by.

A cycler might fly past the Earth at about 21,000 kilometers per hour, or roughly 13,000 miles per hour. Small taxi spacecraft carrying people and supplies would have to rendezvous with the speeding cycler.

“This is sort of like a bus that doesn’t stop,” Longuski says. “When it comes by, you have to run alongside of it and grab on.”

Whether the plan is adopted, the experience has accomplished one goal: to inspire the next generation of space explorers.

“Recently I was at the Air and Space Museum in Washington, D.C., and I saw children running up to the Apollo 11 capsule, so excited, the inspiration in their eyes,” Whitnah says. “Then I remembered that was once me, and this experience is an extension of that.”