Night takeoff of the American Space Shuttle. 3D illustration. |
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Ever since Sputnik launched in 1957, humankind has been reaching deeper into the stars with technological advances and interstellar missions.
Dr. John Junkins, inspired by the space race and a prominent aerospace engineer T.N. Edelbaum, set out to answer a question Edelbaum posed over 50 years ago, how many impulses?
Meaning, how many velocity impulses – and in what direction and at what time – must be used to allow a spacecraft to “fly” from its starting point to reach a specified destination with a minimum total impulse.
The answer to a 50-year question
“How do you optimally fly from A to B?” asked Junkins, who was recently awarded a 2020 Texas A&M Engineering Experiment Station Research Impact Award for his contribution to the development of his space navigation and control research. “That's really the kind of problems I'm dealing with in this research, and those are tough problems that require us to combine judicious control forces with gravitational field effects to fly from one moving object to another.”
Junkins serves as Regents Professor, Distinguished Professor and holder of the Royce E. Wisenbaker Chair in the Department of Aerospace Engineering at Texas A&M University. He is also director of the Hagler Institute for Advanced Study and a member of the National Academy of Engineering.
Prior to Junkins' and his team’s recent work, there was no rigorous process to answer Edelbaum’s question, which arises in virtually every space flight mission.
Additionally, recent advances in low-thrust propulsion means that some spacecrafts are literally propelling for decades of powered flight between objects separated by many astronomical units and, thus, the trajectory design problems are getting more difficult as a consequence.
Working alongside Dr. Ehsan Taheri, an adjunct assistant professor in the department, Junkins’ formulations and algorithms led to a new way to determine continuous thrust minimum fuel orbit transfers. By varying the theoretical maximum thrust allowed by x amount, their approach ultimately revealed the solution for any maximum thrust level. As the theoretical maximum thrust is allowed to approach infinity, longer coasts appear between ever shorter optimal thrust arcs. The limiting case is the answer to Edelbaum’s optimal impulse question for any feasible orbit transfer.
This research, published in a special edition of the Journal of the Astronautical Sciences dedicated to the “50 glorious orbits” of Junkins’ career to date, also helped to earn him the Robert H. Goddard Astronautics Award from the American Institute of Aeronautics and Astronautics in May 2019.
“The work Taheri and I did extended and unified existing methodology,” Junkins said. “And it’s really amazing that many researchers and flight control engineers worked on this for a half century. And, even though I was born a bit too late to be a key player in the Apollo program during Edelbaum’s time, I wasn't born too late to bring closure to an important question he raised and, in the process, established new tools to design space missions optimally and with computational efficiency.”
Developing the next generation
And while his research impacts are numerable and transformational, it is the development of young collaborators and mentees that Junkins places the greatest pride in.
“The basic and applied research I do is very important to me, obviously, I just love this stuff,” he said. “But putting that aside, I consider the development of Ehsan Taheri – through our collaboration – much more important than the specific results we documented in the paper. Because he is a young man and 30 years from now, he will have done all kinds of things that utilize this work and approaches we developed, hopefully affecting many future missions.”
Junkins has mentored more than 50 doctoral students and two dozen post-doctoral collaborators, more than half of which have gone on to become professors and mentors of their own. With each mentee and each day at Texas A&M, Junkins lives out his philosophy that developing people lies at the heart of his approach to academic research and impact.
“The cascade effect of being an effective research mentor is of fundamental importance,” Junkins said. “I've seen virtually all of the young researchers I have mentored develop in ways that went far beyond what I could foresee during the time they worked with me and so many pleasant surprises emerged. Seeing former collaborators build on their work with me is very gratifying. And it is especially rewarding when I see former students mentoring additional generations of bright young engineers.”
Dr. John Junkins, inspired by the space race and a prominent aerospace engineer T.N. Edelbaum, set out to answer a question Edelbaum posed over 50 years ago, how many impulses?
Meaning, how many velocity impulses – and in what direction and at what time – must be used to allow a spacecraft to “fly” from its starting point to reach a specified destination with a minimum total impulse.
The answer to a 50-year question
“How do you optimally fly from A to B?” asked Junkins, who was recently awarded a 2020 Texas A&M Engineering Experiment Station Research Impact Award for his contribution to the development of his space navigation and control research. “That's really the kind of problems I'm dealing with in this research, and those are tough problems that require us to combine judicious control forces with gravitational field effects to fly from one moving object to another.”
Junkins serves as Regents Professor, Distinguished Professor and holder of the Royce E. Wisenbaker Chair in the Department of Aerospace Engineering at Texas A&M University. He is also director of the Hagler Institute for Advanced Study and a member of the National Academy of Engineering.
Prior to Junkins' and his team’s recent work, there was no rigorous process to answer Edelbaum’s question, which arises in virtually every space flight mission.
Additionally, recent advances in low-thrust propulsion means that some spacecrafts are literally propelling for decades of powered flight between objects separated by many astronomical units and, thus, the trajectory design problems are getting more difficult as a consequence.
Working alongside Dr. Ehsan Taheri, an adjunct assistant professor in the department, Junkins’ formulations and algorithms led to a new way to determine continuous thrust minimum fuel orbit transfers. By varying the theoretical maximum thrust allowed by x amount, their approach ultimately revealed the solution for any maximum thrust level. As the theoretical maximum thrust is allowed to approach infinity, longer coasts appear between ever shorter optimal thrust arcs. The limiting case is the answer to Edelbaum’s optimal impulse question for any feasible orbit transfer.
This research, published in a special edition of the Journal of the Astronautical Sciences dedicated to the “50 glorious orbits” of Junkins’ career to date, also helped to earn him the Robert H. Goddard Astronautics Award from the American Institute of Aeronautics and Astronautics in May 2019.
“The work Taheri and I did extended and unified existing methodology,” Junkins said. “And it’s really amazing that many researchers and flight control engineers worked on this for a half century. And, even though I was born a bit too late to be a key player in the Apollo program during Edelbaum’s time, I wasn't born too late to bring closure to an important question he raised and, in the process, established new tools to design space missions optimally and with computational efficiency.”
Developing the next generation
And while his research impacts are numerable and transformational, it is the development of young collaborators and mentees that Junkins places the greatest pride in.
“The basic and applied research I do is very important to me, obviously, I just love this stuff,” he said. “But putting that aside, I consider the development of Ehsan Taheri – through our collaboration – much more important than the specific results we documented in the paper. Because he is a young man and 30 years from now, he will have done all kinds of things that utilize this work and approaches we developed, hopefully affecting many future missions.”
Junkins has mentored more than 50 doctoral students and two dozen post-doctoral collaborators, more than half of which have gone on to become professors and mentors of their own. With each mentee and each day at Texas A&M, Junkins lives out his philosophy that developing people lies at the heart of his approach to academic research and impact.
“The cascade effect of being an effective research mentor is of fundamental importance,” Junkins said. “I've seen virtually all of the young researchers I have mentored develop in ways that went far beyond what I could foresee during the time they worked with me and so many pleasant surprises emerged. Seeing former collaborators build on their work with me is very gratifying. And it is especially rewarding when I see former students mentoring additional generations of bright young engineers.”