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IN–SPACE PROPULSION: 

STRATEGIC CHOICES AND OPTIONS 

HEARING 

BEFORE THE

SUBCOMMITTEE ON SPACE 

COMMITTEE ON SCIENCE, SPACE, AND 

TECHNOLOGY 

HOUSE OF REPRESENTATIVES 

ONE HUNDRED FIFTEENTH CONGRESS 

FIRST SESSION 

JUNE 29, 2017 

Serial No. 115–20 

Printed for the use of the Committee on Science, Space, and Technology 

( 

Available via the World Wide Web: http://science.house.gov 
(II) 

COMMITTEE ON SCIENCE, SPACE, AND TECHNOLOGY 

HON. LAMAR S. SMITH, Texas, Chair 

FRANK D. LUCAS, Oklahoma 

DANA ROHRABACHER, California 

MO BROOKS, Alabama 

RANDY HULTGREN, Illinois 

BILL POSEY, Florida 

THOMAS MASSIE, Kentucky 

JIM BRIDENSTINE, Oklahoma 

RANDY K. WEBER, Texas 

STEPHEN KNIGHT, California 

BRIAN BABIN, Texas 

BARBARA COMSTOCK, Virginia 

BARRY LOUDERMILK, Georgia 

RALPH LEE ABRAHAM, Louisiana 

DRAIN LAHOOD, Illinois 

DANIEL WEBSTER, Florida 

JIM BANKS, Indiana 

ANDY BIGGS, Arizona 

ROGER W. MARSHALL, Kansas 

NEAL P. DUNN, Florida 

CLAY HIGGINS, Louisiana 

RALPH NORMAN, South Carolina 

EDDIE BERNICE JOHNSON, Texas 

ZOE LOFGREN, California 

DANIEL LIPINSKI, Illinois 

SUZANNE BONAMICI, Oregon 

AMI BERA, California 

ELIZABETH H. ESTY, Connecticut 

MARC A. VEASEY, Texas 

DONALD S. BEYER, JR., Virginia 

JACKY ROSEN, Nevada 

JERRY MCNERNEY, California 

ED PERLMUTTER, Colorado 

PAUL TONKO, New York 

BILL FOSTER, Illinois 

MARK TAKANO, California 

COLLEEN HANABUSA, Hawaii 

CHARLIE CRIST, Florida 

SUBCOMMITTEE ON SPACE

HON. BRIAN BABIN, Texas, Chair 

DANA ROHRABACHER, California 

FRANK D. LUCAS, Oklahoma 

MO BROOKS, Alabama 

BILL POSEY, Florida 

JIM BRIDENSTINE, Oklahoma 

STEPHEN KNIGHT, California 

BARBARA COMSTOCK, Virginia 

RALPH LEE ABRAHAM, Louisiana 

DANIEL WEBSTER, Florida 

JIM BANKS, Indiana 

ANDY BIGGS, Arizona 

NEAL P. DUNN, Florida 

CLAY HIGGINS, Louisiana 

LAMAR S. SMITH, Texas 

AMI BERA, California, Ranking Member 

ZOE LOFGREN, California 

DONALD S. BEYER, JR., Virginia 

MARC A. VEASEY, Texas 

DANIEL LIPINSKI, Illinois 

ED PERLMUTTER, Colorado 

CHARLIE CRIST, Florida 

BILL FOSTER, Illinois 

EDDIE BERNICE JOHNSON, Texas 
(III) 

C O N T E N T S 

June 29, 2017 

Page 

Witness List ............................................................................................................. 2 

Hearing Charter ...................................................................................................... 3 

Opening Statements 

Statement by Representative Brian Babin, Chairman, Subcommittee on 

Space, Committee on Science, Space, and Technology, U.S. House of Representatives ........................................................................................................... 4 

Written Statement ............................................................................................ 6 

Statement by Representative Ami Bera, Ranking Member, Subcommittee on 

Space, Committee on Science, Space, and Technology, U.S. House of Representatives ........................................................................................................... 8 

Written Statement ............................................................................................ 10 

Statement by Representative Eddie Bernice Johnson, Ranking Member, Committee on Science, Space, and Technology, U.S. House of Representatives .... 12 

Written Statement ............................................................................................ 13 

Witnesses: 

Mr. William Gerstenmaier, Associate Administrator, Human Exploration and 

Operations Directorate, NASA 

Oral Statement ................................................................................................. 15 

Written Statement (shared written statement with Mr. Stephen Jurczyk) .. 17 

Mr. Stephen Jurczyk, Associate Administrator, Space Technology Mission 

Directorate, NASA 

Oral Statement ................................................................................................. 25 

Written Statement (shared written statement with Mr. William 

Gerstenmaier) ................................................................................................ 17 

Dr. Mitchell Walker, Chair, Electric Propulsion Technical Committee, AIAA 

Oral Statement ................................................................................................. 26 

Written Statement ............................................................................................ 29 

Dr. Franklin Chang-Diaz, Founder and CEO, Ad Astra Rocket Company 

Oral Statement ................................................................................................. 36 

Written Statement ............................................................................................ 38 

Mr. Joe Cassady, Executive Director for Space, Washington Operations, 

AerojetRocketdyne 

Oral Statement ................................................................................................. 44 

Written Statement ............................................................................................ 46 

Dr. Anthony Pancotti, Director of Propulsion Research, MSNW 

Oral Statement ................................................................................................. 55 

Written Statement ............................................................................................ 57 

Discussion ................................................................................................................. 64 

Appendix I: Answers to Post-Hearing Questions 

Mr. William Gerstenmaier, Associate Administrator, Human Exploration and 

Operations Directorate, NASA ............................................................................ 82 

Mr. Stephen Jurczyk, Associate Administrator, Space Technology Mission 

Directorate, NASA ............................................................................................... 87 
Page

IV 

Dr. Mitchell Walker, Chair, Electric Propulsion Technical Committee, AIAA ... 94 

Dr. Franklin Chang-Diaz, Founder and CEO, Ad Astra Rocket Company ......... 99 

Mr. Joe Cassady, Executive Director for Space, Washington Operations, 

Aerojet Rocketdyne .............................................................................................. 104 

Dr. Anthony Pancotti, Director of Propulsion Research, MSNW ........................ 107 
(1) 

AN OVERVIEW OF THE NATIONAL 

AERONAUTICS 

AND SPACE ADMINISTRATION BUDGET FOR 

FISCAL YEAR 2018 

THURSDAY, JUNE 29, 2017 

HOUSE OF REPRESENTATIVES, 

SUBCOMMITTEE ON SPACE, 

COMMITTEE ON SCIENCE, SPACE, AND TECHNOLOGY, 

Washington, D.C. 

The Subcommittee met, pursuant to call, at 10:05 a.m., in Room 

2318 of the Rayburn House Office Building, Hon. Brian Babin 

[Chairman of the Subcommittee] presiding. 
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Chairman BABIN. The Subcommittee on Space will now come to 

order. Without objection, the Chair is authorized to declare recesses 

of the Subcommittee at any time. 

Welcome to today’s hearing titled ‘‘In-Space Propulsion: Strategic 

Choices and Options.’’ I would now like to recognize myself for five 

minutes for an opening statement. 

We are on the cusp of a giant leap in space transportation technology. Advances in in-space propulsion systems hold the promise 

of radically altering space exploration. Breakthroughs will allow for 

faster travel, larger payloads, and greater efficiency. All of this will 

allow humanity to access the very farthest reaches of the solar system. This is clearly a subject that excites the imagination. 

NASA has led the way in developing in-space propulsion since its 

inception. The Space Electric Rocket Test, or SERT–1, as well as 

the Deep Space 1 (DS1) and Dawn missions laid the foundation of 

electric propulsion. The Nuclear Engine for Rocket Vehicle Applications program, or NERVA, demonstrated the viability of nuclear 

thermal propulsion. These investments have ensured U.S. leadership in in-space propulsion, which is important for not only civil 

space missions, but also national security missions and commercial 

applications. Commercial in-space propulsion systems, operating at 

kilowatts of power, are a relatively mature technology today: In 

2015 Boeing began offering the first all-electric commercial satellites. 

Because of these successes, we stand on the threshold of a new 

era, one in which in-space propulsion and power systems could 

grow to a scale and sophistication that would support human 

spaceflight and exploration. NASA is currently developing in-space 

power and propulsion systems that are an order of magnitude more 

powerful than modern commercial systems. Originally developed 

for the cancelled asteroid retrieval mission, this system will now be 

appropriately incorporated into NASA’s exploration architecture 

and may be used on NASA’s Deep Space Gateway. 

Similarly, developing this technology has taught us valuable lessons that will inform the next generation of in-space propulsion, 

which will send humans on to Mars. NASA’s Human Exploration 

Mission Directorate is supporting research on three new in-space 

propulsion technologies. These systems operate at hundreds of kilowatts of power which is another ten times more powerful than the 

systems under development for use around the Moon, and could be 

used on a Deep Space Transport system for missions to Mars and 

even beyond. 

The next-generation in-space propulsion technologies under development by three of today’s witnesses will be critical to ensuring 

that the exploration of Mars is possible, sustainable, and affordable. I hope that their testimony can help the Committee better understand the unique mission options that each technology will offer. 

As important as these developments are for the journey to Mars, 

the most exciting payoffs may come from the ability to develop 

these new engines even further. As discussed in NASA’s Technology Roadmaps, scaling up the power levels another order of 

magnitude and building systems that will operate with thousands 

of kilowatts of power will significantly transform how humanity ex-
5 

plores the solar system. These systems could even put the outer 

planets within reach of human explorers. 

To be clear, these developments are not simply about human 

spaceflight; rather it is an across-the-board change in technology on 

par with the jump from sailing vessels and steam-powered ships. 

That long-term vision is still quite a ways off and will require further work, but the promise is utterly exciting. 

Smart investments, focused exploration goals, and constancy of 

purpose will maintain U.S. leadership in not only in-space propulsion, but also space exploration more broadly. 

Our witnesses today can help us better understand how all of 

these efforts fit together. I look forward to hearing about how inspace propulsion can expand our reach. Advancements in these 

technologies will literally open up a universe of possibilities. 

[The prepared statement of Chairman Babin follows:] 
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Chairman BABIN. And I would now like to recognize the Ranking 

Member, the gentleman from California, for an opening statement. 

Mr. BERA. Thank you, Mr. Chairman. 

Chairman BABIN. I’m sorry. Can I—— 

Mr. BERA. Yes, please. 

Chairman BABIN. I’m about to forget our Ranking Member of the 

full Committee. Sorry about that. Go ahead, Mr. Bera. 

Mr. BERA. Although before I read my opening statement, I’m told 

that there’s a group from the Society of Physics students here 

today, and I just want to recognize those students that are here in 

the audience because they’re interning in a variety of places including our own House Science, Space, and Technology Committee, and 

you guys represent the future, and that’s why we do what we do, 

so if you could stand up for a quick second so we can recognize all 

of you. Thank you for being here. 

You know, Mr. Chairman, I think this is a very timely topic, and 

I’m looking across at this distinguished panel. It may take us a 

while to get through all of your statements but I think we’re going 

to be well-educated. 

You know, chemical propulsion remains a critical part of today’s 

human exploration program. The two rocket boosters on NASA’s 

Space Launch System use a solid chemical propellant and SLS’s 

RS–25 core stage rockets utilize liquid chemical propellant. However, relying solely on chemical propulsion for deep space travel 

would result in spacecraft having to carry large amounts of propellant, possibly requiring multiple launches even before a mission 

can be initiated. That is why many experts believe that NASA will 

need advanced propulsion systems to power the agency’s future 

robotic and manned spacecraft. 

NASA is currently using non-chemical in-space propulsion in the 

form of electric propulsion. Electric propulsion is a continuous, lowthrust process and has been used by a few NASA robotic spacecraft, such as the Dawn probe, which has investigated the asteroid 

Vesta and is now orbiting Ceres. 

The Department of Defense space vehicles and commercial satellites also make use of solar electric power, but primarily for orbit 

raising and repositioning. For example, each Advanced Extremely 

High Frequency Space Vehicle, which provides critical global communications to our warfighters, uses solar electric propulsion subsystems. 

Another type of in-space propulsion enabled through the use of 

nuclear reactors was studied to a limited extent in the 1960s. However, engineers found that the amount of shielding needed to protect crew from the dangerous effects of prolonged exposure to radiation generated by the nuclear reactor as well as other technical 

difficulties were challenges that were hard to overcome at that 

time. 

Now that we’re planning on extended human travel into space, 

research into all forms of advanced propulsion technologies, including nuclear fission, is likely to intensify in the years ahead. It’s 

critical that we find ways to reduce the time crew is exposed to galactic cosmic rays and other dangerous deep-space radiation. Significantly reducing mission duration times can only be achieved 

through advanced in-space propulsion. 
9 

As NASA continues to develop our plans on how to send humans 

to Mars and returning them safely to Earth, now is a good time 

to examine the present and future options for in-space propulsion. 

Mr. Chairman, I look forward to hearing from our witnesses 

about different propulsion technologies and the unique characteristics that make them best suited to particular missions in space. 

Thank you, and I yield back. 

[The prepared statement of Mr. Bera follows:] 
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Chairman BABIN. Absolutely. Sorry about the confusion. Now the 

Ranking Member. 

Ms. JOHNSON. Thank you very much. Let me say good morning 

to everyone and welcome our witnesses, and thank you, Mr. Chairman. I appreciate the opportunity to discuss in-space propulsion 

with a wide range of government, academic, and industry experts. 

In-space propulsion will be a critical enabler of our future missions, especially those involving human exploration beyond Earth 

orbit, and I’m delighted that all of the young people of the future 

are here, and I hope that I see the enthusiasm as we have experienced in the past. 

It is important that the Subcommittee assess the state of research and development related to in-space propulsion technologies, 

which NASA, the National Academies, and the NASA Advisory 

Council all consider a priority. Not only is this technology important for NASA and our space program, but it would also have benefits for the commercial sector, which already uses electric propulsion for maintaining commercial satellite positioning. 

Mr. Chairman, I look forward to this hearing from our witnesses 

about the range and types of in-space propulsion technologies being 

studied and the progress of the research and development into 

each. When we consider progress, we also need to understand 

whether sufficient resources are being invested to make sure the 

technologies will be ready when NASA needs them. It is important 

to note that the budget for NASA’s Space Technology Mission Directorate, which includes work on in-space propulsion, has been relatively flat. Can we achieve the milestones for the needed technology development on a flat budget? 

Mr. Chairman, our investments in research and development of 

enabling technologies such as in-space propulsion are our seed corn 

for achieving our goals for space exploration. It is our job to ensure 

that we make the needed investments will yield us the kind of results we seek. 

I thank you, and yield back. 

[The prepared statement of Ms. Johnson follows:] 
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Chairman BABIN. Thank you. 

Let me introduce our very distinguished panel of witnesses 

today. The first one I’d like to introduce is Mr. Bill Gerstenmaier, 

Associate Administrator of the Human Exploration and Operations 

Directorate at NASA. Mr. Gerstenmaier provides strategic direction 

for all aspects of NASA’s human exploration of space and crossagency space support functions including programmatic direction 

for the operation and utilization of the International Space Station. 

He holds a bachelor of science in aeronautical engineering from 

Purdue University, and a master of science in mechanical engineering from the University of Toledo. Welcome. 

Next I’d like to introduce Mr. Stephen Jurczyk, our second witness today, Associate Administrator of the Space Technology Mission Directorate at NASA. As Associate Administrator, he manages 

and executes the space technology programs focusing on infusion 

into the agency’s exploration and science mission needs, proving 

the capabilities needed of the greater aerospace community and developing the Nation’s innovation economy. Mr. Jurczyk is a graduate of the University of Virginia, where he received a bachelor of 

science and a master of science in electrical engineering. We welcome you. 

Our third witness today is Dr. Mitchell Walker. He is Chairman 

of the Electric Propulsion Technology Committee of the American 

Institute of Aeronautics and Astronautics. Dr. Walker is also a Professor of Aerospace Engineering at the Georgia Institute of Technology, where he directs the High Power Electric Propulsion Laboratory. From 2011 to 2012, Dr. Walker served on the National Research Council Aeronautics and Space Engineering Board for the 

Air Force reusable booster system study. His research interests include both experimental and theoretical studies of advanced plasma propulsion concepts for spacecraft and fundamental plasma 

physics. He also conducts research on Hall-effect thrusters, gridded 

ion engines, diagnostics for plasma interrogation and thruster characterization, and several other aspects of electric propulsion. He received his Ph.D. in aerospace engineering from the University of 

Michigan, where he specialized in experimental plasma physics and 

advanced space propulsion. We welcome you, Dr. Walker. 

Fourthly is Dr. Franklin Chang-Diaz, Founder and CEO of Ad 

Astra Rocket Company. Dr. Chang-Diaz has flown a record seven 

space missions, logging over 1,600 hours in space including 19 

hours on three separate spacewalks. In 1994, he founded and directed the Advanced Space Propulsion Laboratory at the Johnson 

Space Center where he continued developing propulsion technology. 

Prior to founding Ad Astra, Dr. Chang-Diaz joined the technical 

staff of the Charles Stark Draper Laboratory in Cambridge, Massachusetts, where he conducted research in fusion. He earned a bachelor of science in mechanical engineering from the University of 

Connecticut and his Ph.D. from MIT. We welcome you, Dr. Franklin Chang-Diaz. 

Fifth is Mr. Joe Cassady, Executive Director for Space of Washington Operations for Aerojet Rocketdyne. Mr. Cassady has 33 

years of experience in propulsion as well as mission and systems 

analysis. This includes flight projects for both the Air Force and 

NASA. He is also the Vice President of the Electric Rocket Propul-
15 

sion Society. Mr. Cassady earned a bachelor’s of science and a master’s of science in aeronautics and astronautics from Purdue University. He also received a graduate certificate of systems engineering from George Washington University. We welcome you. 

Our sixth witness today is Dr. Anthony Pancotti, Director of Propulsion Research at MSNW. Dr. Pancotti previously worked at the 

Air Force Research Laboratory at Edwards Air Force Base where 

he reviewed and investigated a range of advanced propulsion concepts. In 2011, he joined MSNW to work on a variety of fusion and 

propulsion and plasma concepts and is now the Principal Investigator for their Next Step Propulsion program. He earned his Ph.D. 

in aerospace engineering from the University of Southern California, where he designed, built and tested an experimental highefficiency electrothermal ablative pulsed plasma thruster—that’s a 

mouthful—called a capillary discharge. 

I now recognize Mr. Gerstenmaier for five minutes to present his 

testimony. 

TESTIMONY OF MR. WILLIAM GERSTENMAIER, 

ASSOCIATE ADMINISTRATOR, 

HUMAN EXPLORATION AND OPERATIONS DIRECTORATE, 

NASA 

Mr. GERSTENMAIER. Thank you very much, Members of the Committee for the opportunity to be here to discuss in-space propulsion. 

Propulsion is a critical element of any human exploration plan 

or architecture. We need to further develop the ability to move humans and cargo in space to expand human presence into the solar 

system. Electric propulsion can be a key enabler to successful missions and activities beyond the Earth-Moon system. It offers significant advantages over other forms of propulsion, most notably, efficiency. Electric propulsion can offer the ability to move large 

masses through space with minimum fuel usage. The other advantages are, the fuel is storable, does not boil off, and can be easily 

resupplied. However, the thrust level of current electric propulsion 

systems is typically low and it requires a significant amount of 

time to move the spacecraft in space. Even for habitats in the vicinity of the Moon, we are planning to use 12–1/2-kilowatt electric 

thrusters, which is about 5 kilowatts, or 40 percent, higher thrust 

than typical thrusters used today. 

This disadvantage of long times is substantial when you’re considering transporting crew. We prefer to transport crew as fast as 

possible to avoid prolonged exposure to microgravity and high radiation conditions. We anticipate the early systems for sending crew 

beyond the Earth-Moon system will use a combination of chemical 

and much higher thrust level electric propulsion systems, possibly 

50 to 100 kilowatts or greater. 

The future systems we are investigating would increase thrust 

level and shorten transit time while still maintaining the high efficiency. We are looking at increasing thrust levels by factors of 10. 

These systems are at lower technology readiness levels but offer 

the promise for new technologies in the future. We have partnered 

with American industry through our next step broad agency announcement including some of the panelists here today to investigate and advance the capabilities of these emerging systems. 
16 

Looking at a variety of systems in the early stage of development 

is important. Maturing technologies and demonstrating system performance through ground testing prior to committing to utilizing 

them and operational systems and beginning a major systems development activity helps constrain program costs and schedule risk. 

NASA and other R&D organizations have learned that starting systems development activities prematurely can lead to significant 

technical challenges and unacceptable cost and schedule growth. 

The broad agency analysis process allows us to investigate the specifics of systems design before committing to technologies into an 

actual spacecraft or system. 

As we prepare for missions in the vicinity of the Moon and ultimately Mars, electric propulsion will be a key enabling technology. 

We will build off of the work done in support of the Asteroid Redirect Mission. Our ARM concept worked the tremendous benefits of 

electric propulsion for moving large masses in space, which transformed our approach for human exploration in deep space. The Asteroid Redirect Mission also helped us to understand the advantages of departing the Earth-Moon system for Mars from the vicinity of the Moon rather than from Earth orbit, and we believe using 

electric propulsion to preposition key large elements will be necessary for human Mars-class missions. 

Electric propulsion will play a key role in emerging concepts such 

as crew-tended habitation modules in the vicinity of the Moon. 

With advanced electric propulsion, we will have the ability to move 

habitat systems to various orbits around the Moon. We can support 

crewed science operations from the module and various lunar orbits—equatorial, halo orbits, or even an orbit around Lagrangian 

point two on the far side of the Moon. This far-side lunar orbit location would allow telerobotic operations from crews onboard the 

habitat module on the far side of the Moon, something we—a region of the Moon we have never explored. The module is not stuck 

in one place around the Moon. It can be moved to various locations, 

thanks to electric propulsion. 

As we look to electric propulsion for crew-tended habitation systems around the Moon, we will look for synergies with the commercial communications satellite industry and take advantage of electric spacecraft development in that market. Combining these capabilities with higher-power electric propulsion systems being developed by NASA’s Space Technology Mission Directorate will enable 

both the advance of U.S. industrial capabilities and the creation of 

the in-space infrastructure we need in the lunar vicinity to further 

Nation’s space exploration goals. 

Electric propulsion and advanced propulsion systems will be a 

key enabler for human exploration systems of the future. 

Thank you for the opportunity to discuss this topic with the Committee, and I look forward to your questions. 

[The prepared statement of Mr. Gerstenmaier follows:] 
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Chairman BABIN. Thank you, Mr. Gerstenmaier. 

Now I recognize Mr. Jurczyk for five minutes to present his testimony. 

TESTIMONY OF MR. STEPHEN JURCZYK, 

ASSOCIATE ADMINISTRATOR, 

SPACE TECHNOLOGY MISSION DIRECTORATE,NASA 

Mr. JURCZYK. Chairman Babin, Ranking Member Bera, and 

Members of the Subcommittee, thank you for the opportunity to appear today to discuss NASA’s in-space propulsion research and development activities with a focus on the agency’s efforts in space 

technology. 

NASA’s Space Technology Mission Directorate—STMD—programs are aimed at key research and technology challenges that 

will enable more ambitious missions in the future and create a new 

space economy. STMD is developing new capabilities for in-space 

propulsion including higher-performing chemical propulsion, highpower electrical propulsion, and nuclear thermal propulsion. The 

goal is to demonstrate these new capabilities in the near term to 

transition them into robotic and human missions in the next decade. 

Solar electric propulsion technology has long been a priority technology investment by STMD and such capabilities have been of 

great interest to NASA, other government organizations, and industry for many years. The focus of the current STMD technology 

project has been on increasing the solar power generation capability of spacecraft and development of advanced thrusters that are 

about two and a half times the power level of existing thrusters 

with significant increases in operational lifetime. Recently, NASA 

has demonstrated full performance of a high-power electric propulsion thruster system with more than 2,500 total hours of testing 

with no degradation in system performance. The agency subsequently awarded a contrast to Aerojet Rocketdyne for development 

and delivery of engineering units of a 12–1/2-kilowatt thruster system by the end of 2018. 

The activities to advance solar power generation capability culminated in the successful development of advanced solar arrays by 

our industry partners, Deployable Space Systems and Orbital ATK, 

that are two times lighter and use four times less stowed volume 

for the same amount of electricity produced as compared to today’s 

commercially available solar arrays. 

NASA recently completed an Air Force Research Lab-sponsored 

test of the Deployable Space Systems Solar Array Technology on 

the ISS. The current STP system being developed for demonstration-class mission will provide between 300 and 500 kilowatts of 

power. The initial deep-space transport capability for crewed missions beyond the Earth-Moon system requires an approximately 

300-kilowatt system. STMD intends to continue advancing thruster 

technology, increasing the power level up to 10 times current 

thruster systems to enable this capability. 

The Solar Electric Propulsion Project illustrates the strength of 

a multi-application approach to technology development. Other government agencies and the commercial space sector have shown interest in utilizing the component technologies, especially the 
26 

deployable solar arrays at 5 kilowatts to 30-kilowatt power levels. 

Commercial satellite firms will soon use these arrays with their 

lower weight and improved packaging efficiency to lower the cost 

of future communications satellites. 

STMD is also currently in the second year of a three-year effort 

to develop a safe and affordable nuclear thermal propulsion system. 

This effort is focused on addressing the most significant challenges 

in developing an NTP system including reducing the risk and cost 

of the reactor system, enabling long-term storage of liquid hydrogen, the working fluid for NTP, and developing approach for safe 

ground testing of the system. The agency will use the results of 

these activities to determine the feasibility and cost of advancing 

NTP by development and testing of a ground demonstration system. Although NASA does not expect to require advanced propulsion technologies such as NTP in the initial crewed missions to the 

Mars system, NTP can reduce trip times to Mars significantly. 

Finally, STMD will continue to advance power systems technologies to enable high-performing electric propulsion systems including both solar- and nuclear-based power generation. 

Mr. Chairman, thank you for your support and that of this Committee. I would be pleased to respond to any of the questions that 

you or the other Members have. 

Chairman BABIN. Thank you, Mr. Jurczyk. 

I’d now like to recognize Dr. Walker for five minutes. Thank you. 

TESTIMONY OF DR. MITCHELL WALKER, CHAIR, 

ELECTRIC PROPULSION TECHNICAL COMMITTEE, AIAA 

Dr. WALKER. Mr. Chairman, Ranking Member Bera, and Members of the Subcommittee, thank you for the invitation to share my 

views on strategic investments in America’s in-space propulsion 

technology program. I’ve been fortunate to serve on the faculty of 

the Daniel Guggenheim School of Aerospace Engineering at the 

Georgia Institute of Technology since 2005. It gives me great pride 

to work closely with undergraduate and graduate students as they 

develop into the space propulsion engineers and scientists of our 

Nation’s future. 

I presently service as the Vice Chair of the American Institute 

of Aeronautics and Astronautics Technology Committee, an Associate Editor of the journal Spacecraft and Rockets, and the General 

Chair of the 2017 International Electric Propulsion Conference. I’m 

here today as an individual, and the views I express are mine 

alone. 

Electric propulsion is the acceleration of propellant with electric 

energy to generate thrust for spacecraft. Hall-effect thrusters and 

gridded ion engines are successful examples of electric propulsion 

used in commercial, defense, and civil applications. Electric propulsion offers a significant advantage over chemical propulsion because the exhaust velocity is not limited by the amount of energy 

released from the chemical bonds of the propellant. Compared to 

chemical propulsion, the electrical approach enhances the efficiency 

of the propulsion system by more than an order of magnitude and 

leads to significant reductions in propellant mass. Typically, electric propulsion devices do not have large thrust because of the limited spacecraft power available. 
27 

NASA has been a leader in the development and flight of electric 

propulsion technology. NASA flew its first electric propulsion device in 1964. In 1998, the NSTAR ion propulsion system on NASA’s 

Deep Space 1 spacecraft flew. The NSTAR ion engine enabled a 

trip that included fly-bys of an asteroid and a comet. In 2007, 

NASA launched the Dawn spacecraft that also uses NSTAR ion engine as primary propulsion. To date, Dawn has orbited both Ceres 

and Vesta. Scientists will continue to embrace the unique capabilities of electric propulsion to explore our solar system. 

Our world has gradually shifted to a space-based infrastructure. 

That includes GPS, satellite radio, satellite TV, DOD communications, weather monitoring systems, and we stand in the midst of 

a paradigm shift in the requirements for these spacecraft from traditional chemical propulsion to electric propulsion. This shift is a 

result of a dramatic increase in available satellite electrical power. 

During the last 20 years, investments in solar array technology 

have increased geosynchronous satellite power from 1 kilowatt to 

over 25 kilowatts. In 2015, this trend culminated in the launch of 

Boeing’s first all-electric spacecraft. All-electric satellites use electric propulsion as a primary propulsion and to provide 15 years of 

station keeping on orbit. The enormous propulsion mass savings 

achieved with electric propulsion allows two electric-satellites to 

launch on one smaller, less expensive launch vehicle. Current projections show that 50 to 75 percent of all future geostationary 

spacecraft will use electric propulsion. 

All-electric spacecraft coupled with low-cost launch vehicles enabled our Nation to recapture the global launch vehicle market for 

commercial satellites. To remain economically competitive with this 

success, all launch vehicle providers are forced to upgrade their 

systems. In addition, Europe and Russia continue significant investments in electric propulsion. India and China each launched 

their first electrically propelled geostationary satellite this year. 

Japan is scheduled to launch its first all-electric commercial satellite in 2021. Electric propulsion is recognized as a competitive 

factor in the technology portfolios of these countries. 

There are three activities that I strongly believe will bolster our 

Nation’s leading position in electric propulsion technology. First, investments are required in electric propulsion technology across a 

spectrum of expected time to return on investment. Second, the Nation must invest in ground-based test facilities to develop and then 

fly the next generation of electric propulsion devices. Third, NASA 

must maintain a steady steering of investment in university research programs to ensure that the unique intellectual talent required to fly these systems is available when we are ready to execute on these ambitious missions. 

The role of electric propulsion in the exploration of our solar system, economy and security will increase in the coming decades. 

Thus, investment in NASA’s electric propulsion program helps 

maintain our leading position in space technology, aids economic 

competitiveness of our Nation, enhances our understanding of the 

physical world, and inspires current and future generations to pursue STEM careers. 

Thank you for the opportunity to be here today. I look forward 

to your questions. 
28 

[The prepared statement of Dr. Walker follows:] 
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Chairman BABIN. Thank you, Dr. Walker. 

I’d now like to recognize Dr. Chang-Diaz for five minutes. 

TESTIMONY OF DR. FRANKLIN CHANG–DIAZ, 

FOUNDER AND CEO, 

AD ASTRA ROCKET COMPANY 

Dr. CHANG-DIAZ. Thank you, Mr. Chairman and distinguished 

Members of the Subcommittee. I am honored to be called to testify 

before you on this important topic for our Nation and for our civilization. 

In securing our ability to travel in deep space safely and 

sustainably, we are also ensuring, or helping to ensure the survival 

of our species. I believe that space travel actually beckons humanity a lot more today than it did 50 years ago. But we need to secure 

a safe and robust and fast means of transportation. Going to the 

Moon is one thing; going to Mars is a completely different thing. 

So on the screen I wanted to put up that graphic representation 

of the in-space propulsion challenge before us. Despite decades of 

progress in many areas of space technology, the challenges of deepspace transportation remain as clear and present as they were in 

the 1960s. Our transportation workhorse, the chemical rocket, has 

reached an exquisite level of refinement but it has also reached its 

performance limit. That technology will not provide us with a sustainable path to deep space. It does not mean that we need to discard it. On the contrary, chemical rockets will continue to provide 

foundational launch and landing capabilities for the foreseeable future and reducing their cost is a worthy goal. 

But once you’re in space, the path to sustainable transportation 

lies in high-power electric propulsion, and by high power, I mean 

power levels of 100 kilowatts and up. A hundred kilowatts is 

roughly the power of a small car. Three hundred kilowatts is the 

power of an SUV, just to give you a sense for what these things 

means. 

Each one of us in the NextSTEP Program is due to demonstrate 

the efficient operation of our respective technologies at a power 

level of no less than 100 kilowatts for 100 continuous hours. These 

rockets will first be solar electric and later, as we move outwards 

from the sun, they must transition to nuclear electric power. 

Ad Astra Rocket Company is an American corporation, developing a uniquely American technology. We are based in Texas. Our 

flagship project is the VASIMR engine. It is an electric rocket that 

fits squarely within the high-power niche as previously defined and 

can scale naturally to multi megawatts. The VASIMR originated at 

MIT in the 1980s. The technology was transferred to NASA in the 

1990s and privatized in 2005 by Ad Astra Rocket Company in 

2005. The most advanced VASIMR engine is the VX–200, which is 

a 200-kilowatt engine which has executed more than 10,000 reliable and efficient firings at power levels of 200 kilowatts and higher. Its performance data has been well vetted by the science community and published in the top peer-reviewed journals of our industry. The technology readiness level of the VASIMR is now between four and five. The lion’s share of this development has been 

achieved at Ad Astra Rocket Company with more than $30M of private investment from U.S. and international investors. 
37 

In 2015, NASA became a partner and awarded us a three-year, $3-million-per-year NextSTEP contract to help bring the technology 

to TRL–5. We are halfway through this program and moving 

smartly to its successful completion in mid-2018. 

Mr. Chairman and Members of the Subcommittee, our Nation as 

we move to explore deep space with humans, we must be able to 

travel fast to reduce the debilitating effects of space on the human 

body, to reduce the burden of consumables, life support, to be less 

constrained by planetary alignments and tight launch windows and 

to expand our capability to recover from unforeseen contingencies 

en route. In short, this is the problem punch list we still need to 

solve to give our astronauts a fighting chance in deep space. The 

development of high-power electric propulsion is critical to checking 

these boxes and to meeting our Nation’s goals in space, and I look 

forward to your questions. Thank you very much. 

[The prepared statement of Dr. Chang-Diaz follows:] 
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Chairman BABIN. Thank you, Dr. Chang-Diaz. 

I now recognize Mr. Cassaday for five minutes for your testimony. 

TESTIMONY OF MR. JOE CASSADY, 

EXECUTIVE DIRECTOR FOR SPACE, 

WASHINGTON OPERATIONS, 

AEROJET ROCKETDYNE 

Mr. CASSADY. Good morning. Chairman Babin, Ranking Member 

Bera, Members of the Committee and your staff, I appreciate the 

opportunity to be here this morning to discuss how in-space propulsion will enable and enhance the Nation’s space exploration efforts 

together with the Space Launch System and the Orion. 

I’m going to summarize my remarks here but I’d like to request 

that the written testimony be included in its entirety in the record. 

Thank you, sir. 

On behalf of all Aerojet Rocketdyne employees across the country, I’d like to thank you and your Committee here for the relentless work the Members and staff have put forth to ensure that the 

Nation’s space program is a success. Your commitment to exploration and discovery should be lauded. 

This is a time of excitement and inspiration within the space 

community and, for that matter, across the country and around the 

world. We are building today the systems necessary to get humankind back to deep space and onto Mars starting in the early 2020s 

with the Deep Space Gateway in lunar orbit. 

Just for a moment I’d like to tell you a little bit about who we 

are. Aerojet Rocketdyne is a world leader in power and propulsion. 

We’ve supported the Nation’s defense, civil and commercial space 

efforts for over 70 years. Among the accomplishments we take 

pride in are having launched every astronaut from U.S. soil, landing seven spacecraft successfully on the surface of Mars, and sending spacecraft to visit every planet in the solar system, and I include Pluto in that because it was a planet at the time we launched 

that mission. 

Of particular relevance to this hearing, we’ve been pioneers in 

the application of electric propulsion since the 1980s. In fact, right 

now there are some 160 spacecraft orbiting the Earth flying our 

electric propulsion products of one type or another. 

As NASA looks to expand human presence in the solar system, 

development of efficient in-space transportation systems is critical. 

Solar electric propulsion, or SEP, is key to the sustainable architecture shown in the projected graphic by enabling efficient transfer 

of cargo, habitats and payloads to deep-space destinations in advance of astronaut arrival. Here’s why that’s important. Today we 

can land one metric ton on the surface of Mars. In order to do these 

human missions, we need to land 80 metric tons of supply and 

equipment. Mars missions will also send humans much farther 

than ever before. This combination of heavier payloads and the 

need to travel over greater distances drives us to seek a solution 

that takes advantage of strategic logistics planning. 

An analogy to explain this approach is the way that military deployments are conducted today. First, the heavy equipment, supplies and other logistical items are pre-deployed by large cargo 
45 

ships and planes to the region. Then once the equipment is in 

place, the troops follow by fast air transport. SEP systems are the 

equivalent to the cargo ship for deep-space missions. These systems 

are now under development by NASA and Aerojet Rocketdyne to 

reduce the amount of propellant needed for these space missions by 

a factor of 10. This is important because it costs just as much to 

launch propellant as it does to launch scientific instruments or 

other mission-critical equipment. With SEP, we can reduce the 

number of launches needed and thereby taxpayers cost to achieve 

the mission. We’re well on our way to having efficient in-space 

transportation with SEP. We must continue to adequately fund 

these development and demonstration efforts. 

The primary challenge facing high-power SEP development is the 

risk of losing focus as we go through the critical transition period 

from development to flight demonstration and subsequently operational use. This requires a stable budget and a constancy of purpose. Everything we do should be with the goal of landing human 

on Mars in the 2030s. 

Currently, we’re on a development path that will result in an 

SEP system capability in the 100-kilowatt to 200-kilowatt total 

power range. This is more than adequate for early outpost missions 

to Mars. 

As SEP is scaled up to several hundred kilowatts, another challenge we face is managing the power transfer from the solar arrays 

to the thrusters. To reduce transit times, it’s important that power 

is transferred as efficiently as possible. Since commercial spacecraft 

power systems are designed to power payloads and those are sized 

at 10 to 20 kilowatts, a power system from a traditional spacecraft 

cannot be adapted for a high-power SEP cargo vehicle. We’re currently working on three separate SEP system developments with 

NASA, and details are provided in my written testimony. 

So finally, let me just thank you, and I look forward to answering 

your questions about our in-space propulsion activities. 

[The prepared statement of Mr. Cassady follows:] 
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Chairman BABIN. Thank you, Mr. Cassady. 

I’d like to recognize Dr. Pancotti for five minutes. 

TESTIMONY OF DR. ANTHONY PANCOTTI, 

DIRECTOR OF PROPULSION RESEARCH, MSNW 

Dr. PANCOTTI. Chairman Babin, Ranking Member Bera, and 

Members of the Subcommittee, thank you for the opportunity to 

testify on in-space propulsion in the United States. I thank the 

Committee for its longstanding support of space exploration and 

plasma physics research in this country. I am pleased that the 

Committee is considering such important topics. 

I would also like to thank the Air Force Research Laboratory including the Office of Scientific Research as well as the SBIR program, which initiated and developed FRC propulsion over the past 

decade. 

High-power electric propulsion is a key technology for humanity’s 

sustained presence in deep space. In order to build a permanent existence beyond the bounds of Earth, advanced in-space transport 

will need to break today’s impulse and coast approach and advance 

to continuous direct burns to destinations in our solar system. For 

this approach to be effective, high specific impulse devices are 

needed. This metric ensures that a large fraction of the expensive 

masses we launch into orbit are payload and not just more propellant to get the job done. 

Considering that even the most conservative manned missions to 

Mars are predicted to require almost 100 metric tons to reach the 

planet’s surface, the cost of this endeavor becomes unsustainable. 

The above argument for high specific impulse provides good testimony for all electric propulsion systems. While low-power systems 

could effectively transport spacecraft almost anywhere in our solar 

system, it would take years or even decades. A trip from Earth to 

Mars with today’s electric propulsion and the world’s largest solar 

array on board the International Space Station would take over ten 

years. These time scales do not lend themselves to a sustainable 

deep-space astronauts. To be truly a sustainable endeavor, high 

power is needed to deliver any significant amount of mass in a reasonable period of time. 

While all the technologies being presented here today address 

this fundamental issue of high specific impulse and to a varying degree high power, MSNW’s 100-kilowatt FRC thruster supported by 

the NASA program has some key advantages. In addition to the 

aforementioned, FRC propulsion is very light weight, and as we all 

know, lighter is faster, and for spacecraft, allow more payload on 

board. If humanity’s intent is to explore, build and ultimately inhabit far-reaching destinations, it will require propulsion systems 

that are very light weigh. 

Variable power is another area where FRC propulsion has strong 

advantages. Interplanetary missions that use solar energy have a 

large decrease in power as you travel further away from the sun. 

Because FRC thrusters are pulsed fixed energy devices, not fixed 

power devices, they can accommodate a large range of power inputs 

in a single design. This means that FRC thrusters can be validated 

in cislunar space and the exact same hardware can be applied to 

a Mars transfer mission. 
56 

Another important benefit with regards to power is FRC’s ability 

to scale up. The physics of this technology were born out of the fusion community that currently operate FRC devices at energy levels that would correspond to a 70-megawatt thruster. Considering 

these origins, FRCs would be able to service the propulsion demands for several generations and expand deep space astronauts 

to Mars and the ocean worlds beyond. 

The most unique characteristic of FRC propulsion is their ability 

to operate in a wide variety of propellants including oxygen, which 

typically degrades vital components in other propellant systems. 

FRC thrusters have been demonstrated on pure oxygen as well as 

carbon dioxide, a major component in Martian atmosphere. FRCs 

have also been formed on vaporized water, which is easily stored 

and available—maybe available throughout our solar system. As 

part of MSNW’s NextSTEP program, the FRC thruster will be operated on Martian atmosphere and methane. 

While this fact may have some benefit to traveling to Mars and 

beyond, the real advantages are when we return home, whether 

that trip is to bring back explorers or sample materials, the ability 

to refuel at almost any planetary body within the solar system has 

huge advantages. The cost savings of this approach are significant, 

and NASA is already focused on this topic called institute resource 

utilization. 

We cannot have the future we want tomorrow without investing 

in its technology today. This is no easy task when there are many 

expensive and pressing matters that require our attention at home. 

While many of those matters cannot be ignored, we must keep our 

eyes lifted to the horizons and invest in our future. While this task 

may be daunting and overwhelming, it happens one step at a time. 

By making strategic choices, the next step we take will put us 

on a path to the future that we all want. I applaud NASA and the 

U.S. government for their commitment to space technology and exploration, and with your continued support, my colleagues and I 

can make the right next step for a better future for all of humanity. 

Thank you. 

[The prepared statement of Dr. Pancotti follows:] 
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Chairman BABIN. Thank you, Dr. Pancotti. Fascinating testimony. I notice we had even some more young folks come into the 

room. It’s great to see so many people here this morning to hear 

this testimony. 

I’d also like to introduce two interns I’ve got that are sitting over 

there, both of them real small fellows. You all stand for us, Bo 

Swanson and Jonathan Ladd. We need a bigger office, I can tell 

you that. 

Anyway, we appreciate all of you being here this morning, and 

thank you for this testimony. 

I want to thank the witnesses for your testimony, and I’d like to 

recognize myself for five minutes of questions. 

I’d like to direct this to Dr. Chang-Diaz and Mr. Cassady and Dr. 

Pancotti because I’d like for you to kind of delve into it a little bit 

more for the benefit of all of us here. What capabilities—and let me 

just say this—I’ve had the privilege of touring and visiting two of 

you guys’ facilities, very, very interesting. What capabilities does 

your specific technology have that makes it unique? We’ll start 

with you, Dr. Chang-Diaz. 

Dr. CHANG-DIAZ. For the VASIMR, there are certain features 

that are unique. One is that it can vary the thrust and the specific 

impulse of the rocket, keeping the power the same. It’s essentially 

the same thing that you do when you shift gears in the car, and 

if you drive a car like a racecar driver you step on the gas and you 

never let go and all you do is shift gears, and so when you’re climbing a steep hill, you would want more torque in your wheels so you 

shift to higher thrust, and when you are speeding in flat terrain 

such as interplanetary space, you would want to upshift to fifth 

and sixth gear, and then you will have a higher specific impulse, 

still the same power, maximum, because you paid dearly for the 

power. And so it’s important to have that feature. That’s one. 

The other one of course is that when you’re dealing with plasma, 

you’re talking about very hot substances, and you want to keep 

them off of the surrounding rocket casing, so you want to have 

magnetic nozzles, magnetic pipes that guide the plasma. The way 

you heat the plasma also is unique. We use electromagnetic waves, 

pretty much the same way you heat your coffee in a microwave 

oven: you don’t touch it. You just launch these waves and these 

waves wiggle the plasma and get it really hot, and we’re talking 

about temperatures of the order of two to three million degrees. So 

these are some of the features, and that gives you a great deal of 

capability to open up in the technology, so that’s a summary. 

Chairman BABIN. Mr. Cassady? 

Mr. CASSADY. I think the unique feature of our approach on the 

NextSTEP program is that we’re building upon what we’ve already 

flown. Our device that runs at 100 kilowatts is what we call a 

nested Hall thruster, and there’s some description of it in the written testimony, but just for the group here today, we fly a 5-kilowatt 

Hall thruster on the advanced DHF spacecraft now as was mentioned earlier. It has a single annular region where the plasma is 

generated. The nested Hall thruster takes that, adds a second ring 

outside and then even a third ring, and each of those rings you’re 

running essentially the Hall discharge. So we’re able to take what 

we’ve known today that we fly today and scale it up simply without 
65 

making it that much physically larger, we can scale it up to the 

much higher power. 

The other part of it is, I’d really like to delve into the system aspects. Because we’re doing that approach, we’re able to also deal 

with the power processing issues that we’ve learned a lot of lessons 

on in our flight experience—I’m not sure what’s going on there. 

Chairman BABIN. Ignore that. 

Mr. CASSADY. Ignore it? Okay. Thank you. 

So the other half of the system—the thrusters are obviously very 

important part and they’re the visible part that we all see but the 

other half of the system is the power, and Franklin referred to 

that. We have to shepherd that power through very carefully because wasted power is time to us. We need all the power we can 

get to keep that time down. So we’re building blocks that we’ve 

learned from our flight experience into modular designs that we 

can scale up incrementally to these higher powers, and as Steve 

Jurczyk mentioned earlier that we are also working now on the 12– 

1/2-kilowatt Hall thruster. It’s another incremental step. So 

incrementalism is my, I guess, word that I would use. 

Chairman BABIN. Thank you very much. 

Dr. Pancotti? 

Dr. PANCOTTI. Thank you, Mr. Chairman. I think in my testimony I highlighted quite a bit about what we call ISRU, in-stage 

research utilization, and for me, when we’re looking long term towards sustainable infrastructures in space, to become a spacefaring race or a multi-world species, advanced capabilities that will 

allow us to use the resources of our solar system will become vital. 

Just like today, if you wanted to drive across our country, you 

wouldn’t fill up an 18-wheeler worth of gasoline to make it. You 

would stop along the way and refuel, and I feel this is a very important aspect of building a sustainable infrastructure to be able 

to go to Mars, scoop up atmosphere, and use that to propel your 

spacecraft to the next destination or to return home. ISRU has a 

large payoff for return missions and also return missions from icy 

moons. So if we did want to go to far-off destinations, asteroids or 

icy moon planets, we could take water, use that as propellant and 

return very large samples to Earth. 

The other aspect I think that is fairly unique about FRC propulsion is the power. Not only is it scalable for a very, very large 

range of powers, like I indicated for many generations of propulsion 

systems to come, we can use the same technology but also the ability to vary that power over a mission. Because it’s fixed energy, we 

can optimize an impulse for an exact energy condition, and then by 

changing how often we fire it, we optimize it or we can use it over 

a very, very large of power within a single design. 

Chairman BABIN. Thank you very, very much. 

Now I’d like to recognize the Ranking Member of our Subcommittee, Mr. Bera. 

Mr. BERA. Thank you, Chairman Babin. 

I’m a simple person. I’m a doctor, not a rocket scientist, but if 

I’m thinking about this correctly, let’s think about it in the context 

of travel to Mars just for sake of being concrete. We know the distance that we have to travel. We know the safe amount of cosmic 

radiation that a human being can get exposed to in terms of the 
66 

time potentially. I think just listening to the testimony, we can 

think about this in two different ways. If we’re sending supplies 

that are nonorganic, non-human beings, you know, you can send 

that at one speed, perhaps using one type of propulsion system, but 

then if we are sending human beings, we’ve got to send them at 

a different speed, perhaps faster, but at less weight. Am I thinking 

about this correctly? You know, just as a doctor, you could also 

then think about as we’re thinking about how to send them faster, 

you know, what kind of additional shielding potentially we could do 

to prolong the time that they could be exposed to cosmic radiation. 

That’s correct as well? 

So it’s not an either/or, it’s, you know, perhaps all of these propulsion technologies that we ought to be thinking about here as 

well as, you know, working with our scientists and the folks that 

are looking at that. 

Dr. Pancotti, you also talked about taking water, if we find planets with ice and, you know, there’s some thought that, you know, 

part of our travel back to the Moon is potentially looking for ice in 

some of these deep craters that could—that we could then turn into 

fuel and use the Moon as a launch site. Is that correct or—— 

Dr. PANCOTTI. Yeah, that’s correct. Earth has a very deep gravity 

well, which means it’s very expensive. That’s why it costs so much 

to launch mass out of our gravity well. If we can find resources outside our gravity well or in smaller gravity wells that we can use, 

it will ultimately save us money. 

Mr. BERA. Okay. So for us as we’re thinking about it and explaining to our constituents and the public, when they say well, 

we’ve already been to the Moon, why would we want to go back to 

the Moon. One reason we would want to go back to the Moon is 

that that is a potential secondary launch site. Is that—or not? 

Dr. PANCOTTI. Yes. 

Mr. GERSTENMAIER. Yes. 

Mr. BERA. Well, again, I’m using your expertise to make sure I’m 

educated so that when I’m out talking to constituents and they ask 

these questions or talking to the broader public, it’s like well, 

here’s why this matters, or if they say well, why are you looking 

at solar propulsion or different technologies, well, here’s why this 

matters. 

So, you know, kind of looking at the human element, maybe, you 

know, Mr. Gerstenmaier, what is that—you know, just to kind of 

put it in context, what is that safe time for a human to be exposed, 

you know, using current technology, again thinking about travel to 

Mars? 

Mr. GERSTENMAIER. When we look at Mars today, basically with 

chemical propulsion, the transit time to Mars is roughly about a 

year or so and a year return. That’s right at the limit of the radiation levels that a human can tolerate. So we might have to take 

a small waiver to some of our radiation constraints but we can basically make it with chemical propulsion. The big advantage here 

with the higher-power electric propulsion is you can cut that time 

down and get more margin and so the radiation exposure for our 

crews is dramatically less. So I think that’s interesting about this 

technology is, it really opens up our way to do mission design, the 

way you described. We’ve talked about the gravity well being tough 
67 

to leave the Earth. it’s much nicer from the vicinity of the Moon 

or a high elliptical orbit around the Moon. Now we can station keep 

there with electric propulsion, then use these high-energy power 

systems to transit the Earth-Moon system to these distant locations with much higher speed with a higher thrust level. So this 

technology really opens up the ability—we can do mission design 

to essentially optimize the overall systems design since we’ve minimized the exposure of the human to radiation in a microgravity environment. 

Mr. BERA. So we really should be thinking about multiple modes 

of propulsion. 

You know, one theory that someone was also suggesting were 

these Lagrangian points where, you know, things can sit stationary 

potentially for lack of a better way of describing it, having a gas 

station up there where, you know, having propellant up there, you 

break through the gravity well, you’re able to able to go up there, 

refuel, and then go on. Is that just theoretical or is that something 

that folks think about? 

Mr. CASSADY. I think as Bill was just saying, some of the groups 

getting together now to study how we go, what this architecture 

ought to look like, and you saw a little bit of that in the graphic 

I put up, one of the thoughts is, you could aggregate things out 

there in the lunar vicinity and then depart from there, and part of 

that aggregation—when I say aggregate, I mean bring different 

pieces of the eventual Mars spaceship to that point and that could 

include fuel. So—and then as Anthony alluded to in his testimony, 

you know, as we get better at making fuel on other places where 

we’re going, we don’t have to, you know, use the gas station or 

bring everything from Earth. We’d like to use the things that we 

find when we get out there into the solar system and perhaps we 

have a couple more nodes in the overall subway system, if you 

want to consider it like that, going between Earth and Mars where 

we can refuel the systems. 

Mr. BERA. Great. Thank you. I’ll yield back. 

Chairman BABIN. Yes, sir. Thank you. 

I’d like to recognize the gentleman from Oklahoma, Mr. Lucas. 

Mr. LUCAS. Thank you, Mr. Chairman. 

Mr. Gerstenmaier, what we seem to be talking about here, I 

think can best be described as the concept of extensibility, that 

technologies developed in the near future will be useful for future 

exploration as well, and extensibility prevents the development of 

incapacities. Discuss with us for a moment how NASA ensures that 

its investments in in-space propulsion technologies have that ability. 

Mr. GERSTENMAIER. Again, I think as you’ve kind of heard from 

this discussion, we’re kind of investing in a variety of technologies 

so we don’t pick one technology to focus on solely. We do the broad 

agency announcements to go look at a variety of technologies. We 

test those on the ground. We make sure they show promise. We 

have this requirement for this 100-kilowatt system to run for 100 

hours. That’s a good proof of concept that can be done on the 

ground. Then when that’s kind of behind us, we know the system 

is mature enough, then it can start being fielded into an operational system, and for example, the concept of the habitat around 
68 

the Moon that uses a 12–1/2-kilowatt system that Steve and the 

Space Technology Mission Directorates have been investing in, 

that’s a step up from where we are with electric propulsion today 

and Hall thruster regime but that’s an incremental step moving 

forward. So I think by taking these steps but also investing in 

these far-reaching technologies that are not yet—we’re not sure 

what promise they have, that’s also advantageous too so we need 

to have that mixed investment philosophy of where we’re looking 

at each one of these but then we also look at the application moving forward. 

So we know today commercial communication satellites have 

electric propulsion on them. If we go to this 12–1/2-kilowatt size, 

that can remove the liquid apogee motors that are used from some 

launch vehicles that even helps the commercial satellite industry 

more. So these things have application not only for NASA use but 

also for use of the next generation of satellite technology. So I 

think we invest in a variety of activities not knowing exactly where 

the outcome is and we do it in a measured way that we can then 

get the best technology for future applications. 

Mr. LUCAS. Along that very point, Dr. Chang-Diaz, Mr. Cassady, 

Dr. Pancotti, would you expand for a moment? Besides the government interest, and we just talked about this to a degree, how would 

you quantify commercial interest in high-powered in-space propulsion systems, gentlemen? 

Dr. CHANG-DIAZ. For our company, we started out actually as a 

purely private venture, and it was all funded by private investors, 

and our interest was not really to go to Mars because going to Mars 

is really not a good business right now. So—but it is important to 

build the scaffolding that eventually will make it into a good business, and right now the business of space is closer to Earth, and 

so our vision is more of the vision of the trucking business of space, 

you know, building essentially a logistics capability, an electric 

high-power electric truck, and we think of ourselves as sort of the 

diesel engine of space that enables all these trucks to be traveling 

back and forth between the vicinity of the Earth and the Moon to 

make some revenue for the company and then as needs expand 

why we go further, so that’s the vision. 

Mr. LUCAS. Mr. Cassady? 

Mr. CASSADY. I would just say very similarly, we’ve been in the 

commercial side. We’re supplying hardware now to most of the 

commercial satellite providers who fly electric propulsion. What we 

do see, as Bill said, as we’re working with NASA on these higherpower devices, there are other functions on those spacecraft that 

can be accomplished like taking them from the drop-off orbit where 

the launcher leaves them to their final destination. Then there’s a 

whole world of expanding possibilities that we’re seeing open up. 

People are talking about these large 6,000 satellite low-Earth orbit 

constellations. Those satellites have to go to individual points 

around the globe and be positioned. You can do that very effectively with a space tug, and I like Franklin’s term, the space truck. 

We think of it very similarly. It’s pretty, you know, multipurpose. 

It really serves a lot of different functions. We see interest in the 

DOD world because they’re looking at reducing the cost to get their 

assets where they need to be, and as well as improving the resil-
69 

iency of the assets, and that all involves more maneuverability in 

space, which is, again, something that solar electric can provide to 

them. 

And then finally, I would say, you know, there’s going to be probably an expanding sphere of influence of the economy as we move 

out and do these exploration missions around the Moon. We’re 

going to start supporting people who want to go mine the Moon 

and do things like that. They’re going to need transportation systems as well, and so as we’re moving out to Mars, they’re going to 

be coming along behind us and doing things that are economically 

viable and they’ll need these transportation systems to support 

that. 

Mr. LUCAS. Thank you. 

Mr. Chairman, I see my time’s expired. 

Chairman BABIN. Yes, sir. 

Now the gentleman from Virginia, Mr. Beyer. 

Mr. BEYER. Thank you, Mr. Chairman, very much, and thank 

you for holding this hearing. It was just fascinating. 

Dr. Chang-Diaz, you’ve been in space, and I was impressed with 

your opening paragraph where you said ‘‘In securing our ability to 

travel in deep space safely and sustainably, we’re also ensuring the 

survival of our species.’’ Can you expand on that? Are you worried 

about the survival of our species, and how will going into deep 

space help that? 

Dr. CHANG-DIAZ. Well, this has been voiced by many of my colleague astronauts, and we all believe that, you know, we are all astronauts in this one planet that we have, and it’s the only one we 

have, and we have no redundancy, and astronauts like redundancy. 

You know that. You know that. And so if you look at the way humanity is all housed in this, you know, this one ball, it is our life 

support that matters right now. We have no way to survive if 

something were to happen to us, something that could be brought 

by some external beyond our control event, we would be history 

that no one could tell, and it doesn’t matter that much to the universe whether we are here or not but it does matter to us. And so 

I think the important thing here is for us to enable ourselves to 

be beyond and to work beyond and live beyond our Earth is fundamental to our survival. 

Mr. BEYER. Thank you very much. 

Dr. Pancotti, much of this testimony in this hearing is with the 

understanding that the Asteroid Redirect Mission was canceled and 

that all the work that was done basically—I mean, some of it 

moves forward. I want to ask this of our NASA gentlemen but was 

it a mistake to cancel it and to defund it? 

Dr. PANCOTTI. From my personal view, I don’t think it is. I like 

to use the term, keep our eye on the prize, and that prize is Mars. 

I think the next step forward for humanity I think is a huge calling 

like Dr. Chang-Diaz mentioned, to get to Mars and put people on 

another planet, and in doing so, I think the most direct approach 

to that is the best path forward. 

As far as technology goes, propulsion devices, all three of us that 

are here talking today, those propulsion devices were initiated 

under the ARM mission and they are one of the most direct tech-
70 

nologies that is going to move forward. No matter what we do in 

deep space, we are going to need advanced propulsion. 

Mr. BEYER. Great. Thank you very much. 

Dr. Walker, in your both written and oral testimony, you wrote— 

you said ‘‘Investments are required in electric propulsion technology across the spectrum of expected time to return on investment.’’ Is that just a really polite way of saying that they show no 

return on investment? 

Dr. WALKER. No, it’s not. 

Mr. BEYER. Or not in our lifetimes. And is it reasonable to expect 

a reasonable return on investment when we’re talking about the 

exploration of deep space? 

Dr. WALKER. Sure. Let me explain. I think the spectrum is very 

important. There are commercial things right now that impact our 

economy from how we deliver commercial satellites. That’s a significant business. That business is up for grabs now as electric propulsion has become more mainstream, and the country or group 

that creates the next best electric propulsion device will own that 

business. So we need to make some very short-term investments so 

that we can make sure we have that. In the long term as the power 

available on orbit continues to rise, then we can begin to feed in 

these higher-power devices. So yes, it’s a spectrum, some things 

that will be very impactful in the next five years and other things 

won’t see for 15 to 20 years. Does that answer your question? 

Mr. BEYER. Yes, it does. Thank you very much. 

Mr. Cassady, you talked about how you’re on the development 

path that results in SEP system capability in the 100-kilowatt to 

200-kilowatt power range, and yet we heard I guess Dr. ChangDiaz’s company, they’re already doing a consistent 200 kilowatt. 

Are you lagging behind or is it just because there’s different technologies with different uses, or—you know, you seem uncompetitive 

relatively. 

Mr. CASSADY. So I guess what I was trying to focus on there was 

the total system power that we need to get to Mars in the 2030s, 

and my point was, we don’t need to go to a megawatt to be ready 

to go to Mars; we can do it with 100 to 200 kilowatts. We’ve done 

a lot of internal studies on the architecture as was shown in the 

diagram that I presented there, and I know our colleagues at 

NASA are doing the same thing. What we’re trying to do, and I 

used the word ‘‘incrementalism’’ earlier—we’re trying to come up 

with a ‘‘walk before you run approach,’’ approach, I guess. We know 

the budgets are tight. We know that we’re going to have to work 

under a constrained budget environment for the foreseeable future, 

and within that environment, we’re trying to be responsible and 

say what’s the minimum amount that we need to have to ensure 

we can do this mission and make the mission close, and for the 

cargo part of that mission, we can live with about 200 kilowatts, 

something in that range. 

Mr. BEYER. Great. 

Mr. CASSADY. That’s for the total system, and then the idea is 

that we plug in these 12–1/2-kilowatt thrusters that we’re developing right now for STMD onto that vehicle and that would be the 

cargo vehicle. That’s why most of that payload that we talked 

about to Mars before the astronauts get there and pre-deploy it. 
71 

Mr. BEYER. Great. Thank you. 

Mr. Chair, I yield back. 

Chairman BABIN. Yes, sir. Thank you. 

Now the gentleman from California, Mr. Rohrabacher. 

Mr. ROHRABACHER. Thank you very much, Mr. Chairman, and 

thank you, Mr. Chairman, for having this hearing today and organized as it is so that we can have a better understanding of the 

goals and the technology needed to achieve those goals, and I appreciate the witnesses and I appreciate your leadership on this. 

We had a hearing on materials and the development of new materials and how that relates to human progress yesterday or the 

day before, and when we are talking about the electric propulsion 

systems now which is being presented to us as some new type of 

options that we have, how much of this is dependent, was dependent on new materials? Is this something that’s part of this formula? 

Whoever wants to, go right ahead. 

Dr. CHANG-DIAZ. It was quite dependent on materials, advanced 

materials, particularly when you deal with very hot plasmas, and 

you have to encase these plasmas in materials that will not erode 

away or melt away, so there are some special ceramics that have 

been developed that enable us to shine these electromagnetic waves 

and make the plasma hot yet they go right through the walls of 

the rocket. So the material development has been critical. 

For us, some of the means of delivering this energy to the plasma 

requires materials and special antennas and special coatings that 

we use, very new materials, of course, that are proprietary right 

now but definitely materials is very important. 

Mr. ROHRABACHER. Do any of these materials—I have not been 

a friend of necessarily spending more money on fusion energy. I felt 

that was something that doesn’t seem like we’ve made much 

progress. However, I’ve been told that fusion energy, or actual or 

attempt to develop it has helped produce new materials. Is this 

part of that? 

Dr. CHANG-DIAZ. In our case, it is, and I think in the case of Anthony’s as well. I think we both have the same pedigree from the 

fusion energy program way back in the—well, he’s a lot younger 

but I go back to the 1970s when we were trying to develop fusion 

and they told us it was 20 years away. 

Mr. ROHRABACHER. In light of that expression where the young 

kid says ‘‘I don’t know where I’m going but I’m on my way,’’ and 

I think with fusion energy, as I say, I’ve been skeptical. I’m working to the point where we can use it for the production of electricity 

here but we can see that there’s benefits that we don’t know were 

going to happen, and so I’m very pleased to hear that all that 

money that we spent on fusion energy didn’t go to waste. So thank 

you very much. 

I’d like to ask Mr. Jurczyk about the choices here that we do 

have, and maybe it’s like a choice between fission and fusion. I 

don’t know. But the idea of having a refueling station, cryogenic 

propellant storage station there, is that with this type of new technology that we’re taking about developing and putting into place, 

is it still important for us to do cryogenic storage facilities and refueling, basically refueling stations if we have this capability? 
72 

Mr. JURCZYK. As Mr. Gerstenmaier mentioned, one of the real 

advantages of electric propulsion is the storability of the propellant. 

So for the 12–1/2-kilowatt thruster system, xenon is the propellant 

and xenon is storable, and so we don’t have to come up with credibility to either passively or actively cool the system to keep that 

propellant available to the thruster system. However, if we look at 

more advanced chemical propulsion systems like locks hydrogen 

propulsion systems for space, and that would require advances in 

technology for both long-term storage of locks and particular hydrogen, long-term storage of hydrogen is very challenging and you’ll 

need active cooling to be able to do that in transfer technologies. 

So that would be more geared towards if we went to higher-performing in-space chemical propulsion stages. The real advantage of 

electric propulsion is the storability of the propellant and not needing to go to cryogenic propellants. 

Mr. ROHRABACHER. I’m not sure if that was a yes or no, but— 

do we see that if we’re going to be having a successful—there’s talk 

that maybe—you know, keep your eyes on the prize, like you say. 

I’m not necessarily involved with trying to eliminate all these other 

options we need to do in space in order to just get to Mars, but in 

order to do some of our Moon—if we readjust so it’s Moon first, 

then Mars, will we need a cryogenic storage facility as compared 

to a deep space propellant like was being described today? 

Mr. JURCZYK. Yeah. If we continue to go down the route of chemical propulsion, we talk about—we talked about being able to 

produce a fuel with water resources on the Moon and then being 

able to handle that propellant, store it and transfer it would be a 

capability we’d want to need if we wanted to use that ISRU capability on the Moon as was mentioned previously, yes. 

Mr. ROHRABACHER. Well, thank you, gentlemen, very much. It’s 

been a very educational experience. God bless. 

Chairman BABIN. Thank you. 

Now I’d like to recognize the gentleman from Florida, Mr. Posey. 

Mr. POSEY. Thank you very much, Mr. Chairman, and I thank 

all of you on the panel for this very informative session, all of you. 

Dr. Chang-Diaz, I was particularly pleased that you mentioned 

survival of our species as an important aspect of our space missions. I don’t think that’s emphasized enough. For a number of 

years, I know anytime any of us mentioned it, critics said you’re 

trying to scare people into supporting space, and a lot of those critics dropped off a year or so ago when that relatively small, 

undetectable asteroid detonated over an uninhabited area of Russia 

a thousand miles from the closest living person and still injured 

over a thousand people, and made them reflect a little bit more 

about the cause of the last Ice Age, the cataclysmic asteroid that 

hit the Yucatan peninsula. 

But anyway, thank you for mentioning that. I wish we would all 

be more informed about it and mention it more often. I think the 

public would have an interest in that. Since there’s no more shuttles for Bruce Willis to change the course of these things on, we’d 

be in a bit of a bind. The longest silence I ever heard in this place 

was when I asked three of our top-ranking space officials what 

would happen if we found a relatively small one, the size of the one 

that exploded over Russia, headed for the Big Apple and we had 
73 

three days, and we never would have three days to do something 

about it. It’s the longest silence I’ve ever heard in this Committee. 

But anyway, having always been informed that there’s no such 

thing as perpetual motion or a perpetual energy machine, I wonder 

if any of you would care to comment on the closest thing to it that 

you have ever seen. 

Dr. CHANG-DIAZ. I mean, in our case, we deal with it every day, 

it’s superconductivity. The magnet that produces the strong magnetic field that houses the plasma in the rocket is a superconducting magnet, and this magnet runs electricity through its 

windings with almost zero, absolute zero resistance. So in a sense 

it’s like this current can keep going forever. It’s almost like a perpetual motion machine. It is not. There is a tiny little bit of resistance that you have to deal with, and that comes out in the electric 

bill that you do have to pay to keep the magnet running. It’s just 

about 100 watts but you do have to pay for that. And this is technology that’s already in the field and we see it in hospitals. MRI 

machines are basically superconductors, and we want to improve 

that technology to the high-temperature superconductors, which 

are much cheaper, much more capable so that we can have MRI 

machines in ambulances and perhaps in field hospitals or clinics 

and something that really can be done that way. So this is the way 

space feeds back to our society. 

Mr. POSEY. There’s been some theories that some other folks may 

have harnessed isolated and focused magnetism in a way that 

would propel without sparks. What do you think about that? 

Dr. CHANG-DIAZ. Well, I’ve seen a lot of fringe projects that 

promise to deliver tremendous results, but we’re all scientists and 

we all believe in the scientific process that’s in place where scientists vet these things and you have to do an experiment and 

measure and be able to prove to your peers that you are measuring 

the right thing, and after you’ve done that, then people believe you. 

But until you do that, it’s all just smoke and mirrors. 

Mr. POSEY. Do any of you foresee any advances or breakthroughs 

in battery storage capacity in the relatively near future? 

Mr. CASSADY. Yeah, I think that’s something we’re working pretty actively right now. We just replaced the batteries on the Space 

Station with lithium ion, an upgrade from the nickel hydrogen batteries that were the primary technology available at the time we 

started putting the Space Station together, and so we have a group 

in our company that’s always looking at the next battery wave 

that’s coming ahead of where we are now. A lot of that’s being driven by what you see across multiple industries including the automotive industry, laptop computers and things like that, but we’re 

looking always for what’s the next energy-efficient without the 

problems of some of the reactivity that you have in something like 

a lithium ion battery, and there’s a lot of applications for that that 

are driving that including long-term undersea as well as space, so 

yes, sir. 

Mr. POSEY. I was going to ask you about a form of hydrogen but 

I’m about out of time and—— 

Chairman BABIN. No, sir. I’m going to take the liberty of the 

Chair and say we’re going to ask some more questions. Go ahead. 

Finish. 
74 

Mr. POSEY. You know, when we talk about hydrogen that there’s 

all kinds of hydrogen. During World War II we were having some 

disasters with some of our Navy frogmen, I understand. They’d be 

down there welding up a hole in a ship and their mask would explode, and it’s my understanding that it was finally determined 

that the bubbles from the welding that they’re doing contained a 

hydrogen and very explosive, and that was causing the problems 

with their masks. I don’t know if that’s a fact. I’ve been informed 

that from several sources. 

So I saw a person one time have a fish tank filled with water, 

a stream of carbon at the bottom of the tank, put a welding rod 

in there, ignited the carbon, and it continued to burn by itself, and 

it made bubbles, and he had like a bell jar on top, and the bubbles 

burst and he captured the hydrogen in the bell jar, and pumped 

it into a compressor. He just used like a diver’s air tank, sealed it 

up, hooked it up to a little engine, started the engine. The engine 

ran off it for about ten minutes that I witnessed, could put my 

hand on the engine, could put my face on the exhaust pipe. It ran 

that cool, and I’d just like your thoughts on that. I mean, I perceived all kinds of things just from looking at that and all kinds 

of uses for it, and I’m just—— 

Dr. CHANG-DIAZ. Yeah, your—I think your description, it seems 

to me that it was electrolysis—— 

Mr. POSEY. Yes, yes. 

Dr. CHANG-DIAZ. —was what was happening here, and it was 

producing just—it happens that the electricity and that spark that 

you were seeing was breaking the water molecules into oxygen and 

hydrogen, and so there must have been two streams of gas, one 

that he captured in the bell jar, which was hydrogen, but there was 

also oxygen coming out, and yes, in fact, in our company, we’re 

very deep in the hydrogen economy. In my home country of Costa 

Rica, we’re trying to deliver and produce hydrogen from water and 

solar and wind energy electrically to power transportation, to 

power cars and mostly urban buses and trains and so on. So it is 

very much here and now. 

Mr. POSEY. The typical hydrogen that you might put in a balloon 

and the balloon would be flat the next day. So we put some of this 

in a balloon and it was still just about fully blown up for over a 

month, and I just thought maybe the bucky balls were different in 

there, they were thicker, bigger, and that would not have let them 

escape, but I imagine by now—and this was 20 years ago—I 

thought now we’d be seeing something like this in progress and 

making energy for it and running people’s homes and over-the-road 

trucks, and I’m just surprised. 

Anyway, I know my time’s up now, Mr. Chairman. Thank you so 

much, Mr. Chairman. 

Chairman BABIN. No, sir, I think he’s into racing cars and I 

think he’s trying to figure out some way to get an edge with hydrogen. 

Mr. POSEY. You know, I did spend a day with Smokay Yunick before he passed away, the greatest automotive mind I think in 

American history, and Smokay’s the one that said—I mean, we 

talked about it a long time. He scratched his head and he said— 
75 

I mean, it’s just hydrogen but it’s different than any other hydrogen I’ve ever dealt with here. 

Thank you, Mr. Chairman. 

Chairman BABIN. Yes, sir. Thank you, Mr. Posey. 

There was just a couple more questions that I wanted to ask as 

well of a couple of you, and Dr. Walker, what are the largest technological challenges associated with the development of advanced 

in-space propulsion generally? What are we dealing with her? What 

are we having to overcome? 

Dr. WALKER. So the largest technological challenge is time. So 

whatever everyone alluded to here is I need a lot of electricity so 

I can get my trip time down. What they’re not saying is that that 

means those engines that we use have to last thousands of hours, 

so the engine has to be able to run for years, and so if there is 

some small, little process that’s slowly eating away at that engine, 

I have to have a great experiment to catch that process so I don’t 

build it into my final product. So for us, we have to have really 

great facilities so we can catch the little, slow, progressing physics 

that will eventually kill the engine. 

Chairman BABIN. And you’re still talking about electric propulsion and solar electric propulsion, right? 

Dr. WALKER. That’s correct. 

Chairman BABIN. The slightest little flaw over a period of years 

and you have a destroyed engine and you’re dead. You’re dead in 

the water. 

Dr. WALKER. Correct. 

Chairman BABIN. Yeah. Okay. And then I wanted to also ask Mr. 

Gerstenmaier, extensibility is the concept that technologies developed in the near term be useful for future exploration as well. Extensibility prevents the development of dead-end capabilities. How 

is NASA ensuring that its investments in in-space propulsion technologies are extensible? 

Mr. GERSTENMAIER. Again, kind of what we’re doing is, we look 

at systems that we put together, so when we talked about the 

cislunar habitat or the Deep Space Gateway, that uses 12–1/2-kilowatt thruster technology. We think a lot of the things we saw for 

that 12–1/2-kilowatt thruster level can be then advanced and 

moved forward through things similar to the nested technology 

that Joe talked about a little bit and then you can advance that 

to the higher-level thrust, maybe 50-kilowatt thrusters, for the 

deep-space transport. So that technology we do around the Moon 

to allow us to maneuver the habitat to various locations, that same 

technology then can be advanced and pieces of it moved forward. 

We’re also not only doing that but then we’re also investing in 

this brand-new technology, the things that two of the panel members here are looking at that’s a different technology but it has tremendous potential for us, so we want to invest in those on the 

ground to look at things like running them for 100 hours, and that 

was part of our test plan, and that was to look at this life issue 

that was described by the panel. So we think we can do that, then 

if that comes online, then we can interject that technology into that 

next generation of spacecraft. So the idea is to look at what we’re 

doing with each piece, look at the individual technology underneath 

it, the power systems that have to convert from solar arrays and 
76 

bring that power level to the thrusters. That same power conversion technology is common no matter what the thruster itself does. 

So that technology is common. So we look for those areas, those 

common threads across multiple technologies that can be expanded 

or extended into other areas, and we don’t end up with a technology that only supports one type of spacecraft and has no applicability to other spacecraft. 

Chairman BABIN. I appreciate that. We’re talking about faster 

velocities. How much faster? I mean, if we’re talking about this 

type of propulsion, and put it in terms of those of us who are 

laypersons can understand. How much faster are we talking about 

here? Any of you if you’d like to chime in. 

Mr. CASSADY. So I mentioned the architecture studies that we’re 

looking at. We typically want to try to work on about a two-year 

cycle for Mars missions as you know. About every other year 

there’s a favorable opportunity to leave. So what we do—when I 

mentioned that 100- to 200-kilowatt system power level, we are 

trying to time the launches of the cargo vehicles so that they will 

be there, have enough time to have that equipment in position before we launch the crew on the next opportunity so there’s sort of 

a natural cycle there of about two years. If we don’t have enough 

power, and for whatever reason the thruster technology isn’t adequate or the power system technology doesn’t give us the efficiency 

of the power transfer from the arrays to the thrusters, then we’d 

end up probably extending that by six months or a year. So then 

we’re out of sync and we’re not able to support the mission. So 

that’s really the trade the way we look at it. It’s fitting the longer 

transit time that the solar electric’s going to take to the other mission constraints like when we’re going to want to launch the crew 

and get them there so that everything lines up. 

Chairman BABIN. Okay. Thank you. 

And then one last question, Mr. Jurczyk. Future in-space propulsion may require enormous amounts of power beyond what solar 

power can feasibly provide. What kinds of other power technologies 

is NASA pursuing to meet increasing power demands in coming 

decades? 

Mr. JURCZYK. Yeah, so right now we’re focused on compact nuclear fission-based reactors targeted for surface power currently but 

we can evolve it to spacecraft power systems. So early next year 

in collaboration with DOE we’re going to demonstrate a 1-kilowatt 

fission-based reactor at the Nevada Test Site that scales to 10 kilowatts. And then the other key technology that’s part of that is the 

conversion technology. So that’s going to use sterling cycle engine 

technology to convert the heat from the reactor to electrical power. 

There are other cycles that we need to look at too but that’s going 

to be key to get the efficiency up to convert the heat from the reactor to electrical power and continue to advance that conversion 

technology. So we are working—your current efforts are focused on 

surface power but we’re looking at how those technologies and systems are extensible for nuclear power for spacecraft. 

Chairman BABIN. All right. 

Mr. Bera? 

Mr. BERA. I’ll take advantage. I feel like a student in office hours 

with the professors here. 
77 

So thinking about this with regards to solar electric propulsion, 

Mr. Cassady, the further you get away from the sun, does the 

amount you can generate diminish? 

Mr. CASSADY. Yes. 

Mr. BERA. Okay. 

Mr. CASSADY. Yes, and Anthony referred to that in his remarks. 

So we’re falling off, it’s roughly a factor of two out at Mars. If you 

look at the history of deeper space exploration with the exception 

recently of Juno, everything we’ve sent out further in the solar system has used some sort of either radioisotope or other type of nuclear power, and solar arrays are only going to be good probably 

for going between here and Mars. At that point, some point in the 

future as we start to go further out, especially with human-scale 

missions, we’re going to need to have nuclear power developed. 

Mr. BERA. And again, it’s appropriate. You know, part of the reason why we can use nuclear when we’re going further out is, we 

don’t have human beings and obviously the exposure factor is different. 

It’s also accurate to think then, you know, so for us in the public, 

we see big launches and you see the big thrusts and so forth. That 

really is to break the gravity well. Once you’re beyond the gravity 

well of Earth and you’re in the vacuum of space—and I don’t know, 

you know—I think of space as a vacuum but I don’t know if it’s 

a true vacuum. As you’re accelerating, though, you’re going to continue to accelerate. Is that not—are we thinking about that correctly? 

Dr. PANCOTTI. Yes, that’s correct. So part of what I was talking 

about, we’re dominated by orbital mechanics, right? So if the chemical system is what I call in my initial argument was kind of the 

impulse and coast, and that’s what we do with chemical systems. 

We apply a force and then we coast for a very long time so all of 

the orbits line up and we can get to our destination as efficiently 

as possible because with chemicals systems with low ISP, they’re 

not efficient and we have to do that in order to rendezvous and 

make that approach. 

When I was talking about going to very high power and very 

high ISPs, we can talk about doing direct burns where we turn the 

thruster on and we leave it on and we just pick our target, we aim 

directly towards it, and we go straight for it. In order to do that 

in a short time, you need a large power, megawatts’ worth of 

power, a nuclear reactor-type power. 

Mr. BERA. So you can—if you’re continuously thrusting and burning, you can cut the time down? 

Dr. PANCOTTI. Yeah. In fact, sometimes you can even eliminate 

the need to do a fly-by, which is sort of another lap around the sun, 

and for some missions, there’s a lot of missions right now in the 

new frontiers proposals that are out there that are looking at solar 

electric for that reason just because the science return, the time 

frame that they can get it back is reduced dramatically for these 

principal investigators. 

Dawn is another good example that was brought up earlier. The 

ability to directly fly orbit one body in the asteroid body and then 

depart and go to another body, that’s unprecedented. We’ve never 

been able to do that. And Dawn actually, I believe I read this right, 
78 

my friend John Brophy at JPL was telling me the total amount of 

impulse that Dawn provided to the spacecraft, the ion engines provided to the spacecraft, was greater than the Delta-2 rocket that 

launched it out of the gravity well, so that’s just to give you some 

idea, and it was done with just a couple hundred kilograms of 

xenon that was onboard the spacecraft. 

Mr. BERA. So we spent a lot of time talking about acceleration 

and so forth but we also then have to think about deceleration, 

right? Do you have to use propellant to decelerate or do you 

through science use the natural gravity and atmosphere? 

Mr. JURCZYK. Missions now use propellant to decelerate to say, 

achieve Martian orbit. There are other approaches that we’ve studied like aerocapture so you can dip down into the Martian atmosphere and use atmospheric drag to decelerate and then come back 

out and achieve Martian orbit. So there are other approaches that 

do not need propellant. But we haven’t tried any of those yet, and 

I’d be really looking forward to a mission that would be willing to 

sign up for aerocapture. We do aerobraking right now where we go 

into Mars orbit in a high elliptical orbit and then dip down in the 

atmosphere to slow down and circularize the orbit but we haven’t 

done aerocapture yet. 

Mr. BERA. And then I guess my last question, one that I hadn’t 

necessarily thought about, we’ve talked about what powers the engine, the propellant, the gasoline in that engine, and just again listening to the conversation, different propellants require different 

size gas tanks in essence, and right now are we also doing research 

on smaller propellants as well? 

Mr. CASSADY. So there’s a number of sort of lower technology 

readiness level things out there that people are looking at, especially now. I mentioned the constellations of satellites earlier. A lot 

of those constellations want to fly electric propulsion onboard a 

very small spacecraft, you know, maybe something that would sit 

on this table in front of me here, and for them, xenon, while it’s 

good, it has some of the problems that you brought up—it needs 

a big tank of some sort—and they’re looking at things that might 

be able to fly with a solid propellant, for instance, something like 

iodine and then let that propellant just sublime off into a gas and 

be run through the engine. So there are some programs like that 

I know that are out there and people are looking at. 

Mr. JURCZYK. Just to add, we have several public-private partnerships within STMD, not only with our programs but also SBIR 

to advance these very highly efficient, very compact electric propulsion systems for cube sats and small spacecraft, and that’s come 

along pretty well. Iodine—solid iodine is definitely one of the propellants that you can get the energy you need in a very small package. 

Mr. BERA. Great. Thank you. 

Chairman BABIN. Thank you, Mr. Bera. 

And Mr. Posey has some additional questions. 

Mr. POSEY. Just since we have the extra time, Mr. Chairman, if 

nobody minds. 

As you know, we’re still waiting on a map to Mars, a roadmap 

to kind of put everything in perspective, and so there’s questions. 

We had the pleasure of asking today and learning the answers to 
79 

today that maybe are a little bit ahead of the edge but we talk 

about the craft and the engines to take us to Mars, and we talk 

about the durability of them that’s required, which is a serious 

issue, and I assume that we would use the craft and the engines 

continuously as much as possible. Once we would get them in orbit, 

we’d just have cyclers. We’d eventually have a supply train up 

there. Maybe we’d go back and forth to the Moon. I think Buzz 

Aldrin talked about it in his cyclers. You know, we ought to be able 

to get fuel on the Moon to go back and forth and refuel the cyclers 

and have stuff going all the time where if you were on Mars, you 

wouldn’t have to wait two years to come home again, we’d have 

something going through there all the time. Thoughts about that? 

Dr. PANCOTTI. Yeah, I can comment. I think what you’re talking 

about is a truly sustained architecture. Those are the words we use 

a lot, a sustainable deep-space architecture. What we’re talking 

about today is building the foundations to make that possible. With 

advanced power, in particular high ISP, which electric propulsion 

devices can do, you can start talking about building those infrastructures in space where you do have a continuous supply of materials. 

Mr. POSEY. I think the NASA guys thank you for answering that. 

Thank you, Mr. Chairman. 

Chairman BABIN. Is that it? Okay. 

This has been a very fascinating hearing, one of the best ones 

that I believe I’ve had since I’ve been in Congress, so I’d like to 

thank the witnesses for being here and answering these questions, 

and I really, really appreciate your expertise in your fields, and 

without any further ado—let’s see. Well, anyway we’re going to 

have this thing opened up for a while to take any further questions 

or if any of the other Members who were not able to be here, if 

they want to ask further questions, they certainly can. It will remain open for two weeks for additional comments from our Members. 

So without any further ado, I adjourn this hearing. Thank you. 

[Whereupon, at 11:46 a.m., the Subcommittee was adjourned.] 

(81) 

Appendix I 

ANSWERS TO POST-HEARING QUESTIONS
82 

ANSWERS TO POST-HEARING QUESTIONS

Responses by Mr. William Gerstenmaier 
83 
84 
85 
86 
87 

Responses by Mr. Stephen Jurczyk 
88 
89 
90 
91 
92 
93 
94 

Responses by Dr. Mitchell Walker 
95 
96 
97 
98 
99 

Responses by Dr. Franklin Chang-Diaz 
100 
101 
102 
103 
104 

Responses by Mr. Joe Cassady 
105 
106 
107 

Responses by Dr. Anthony Pancotti 
108 
109 

Æ