[House Hearing, 115 Congress]
[From the U.S. Government Publishing Office]
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
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
Available via the World Wide Web: http://science.house.gov
______
U.S. GOVERNMENT PUBLISHING OFFICE
26-237PDF WASHINGTON : 2017
-----------------------------------------------------------------------
For sale by the Superintendent of Documents, U.S. Government Publishing
Office Internet: bookstore.gpo.gov Phone: toll free (866) 512-1800;
DC area (202) 512-1800 Fax: (202) 512-2104 Mail: Stop IDCC,
Washington, DC 20402-0001
COMMITTEE ON SCIENCE, SPACE, AND TECHNOLOGY
HON. LAMAR S. SMITH, Texas, Chair
FRANK D. LUCAS, Oklahoma EDDIE BERNICE JOHNSON, Texas
DANA ROHRABACHER, California ZOE LOFGREN, California
MO BROOKS, Alabama DANIEL LIPINSKI, Illinois
RANDY HULTGREN, Illinois SUZANNE BONAMICI, Oregon
BILL POSEY, Florida AMI BERA, California
THOMAS MASSIE, Kentucky ELIZABETH H. ESTY, Connecticut
JIM BRIDENSTINE, Oklahoma MARC A. VEASEY, Texas
RANDY K. WEBER, Texas DONALD S. BEYER, JR., Virginia
STEPHEN KNIGHT, California JACKY ROSEN, Nevada
BRIAN BABIN, Texas JERRY MCNERNEY, California
BARBARA COMSTOCK, Virginia ED PERLMUTTER, Colorado
BARRY LOUDERMILK, Georgia PAUL TONKO, New York
RALPH LEE ABRAHAM, Louisiana BILL FOSTER, Illinois
DRAIN LaHOOD, Illinois MARK TAKANO, California
DANIEL WEBSTER, Florida COLLEEN HANABUSA, Hawaii
JIM BANKS, Indiana CHARLIE CRIST, Florida
ANDY BIGGS, Arizona
ROGER W. MARSHALL, Kansas
NEAL P. DUNN, Florida
CLAY HIGGINS, Louisiana
RALPH NORMAN, South Carolina
------
Subcommittee on Space
HON. BRIAN BABIN, Texas, Chair
DANA ROHRABACHER, California AMI BERA, California, Ranking
FRANK D. LUCAS, Oklahoma Member
MO BROOKS, Alabama ZOE LOFGREN, California
BILL POSEY, Florida DONALD S. BEYER, JR., Virginia
JIM BRIDENSTINE, Oklahoma MARC A. VEASEY, Texas
STEPHEN KNIGHT, California DANIEL LIPINSKI, Illinois
BARBARA COMSTOCK, Virginia ED PERLMUTTER, Colorado
RALPH LEE ABRAHAM, Louisiana CHARLIE CRIST, Florida
DANIEL WEBSTER, Florida BILL FOSTER, Illinois
JIM BANKS, Indiana EDDIE BERNICE JOHNSON, Texas
ANDY BIGGS, Arizona
NEAL P. DUNN, Florida
CLAY HIGGINS, Louisiana
LAMAR S. SMITH, Texas
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
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
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.
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
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 explores 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 in-space propulsion can expand our reach. Advancements in
these technologies will literally open up a universe of
possibilities.
[The prepared statement of Chairman Babin follows:]
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
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, low-thrust 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.
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:]
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
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:]
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
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 cross-agency 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 Propulsion 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 high-efficiency 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. 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:]
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
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,
high-power 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 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.
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.
[The prepared statement of Dr. Walker follows:]
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
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 deep-space 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.
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:]
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
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 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:]
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
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.
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:]
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
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 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 space-faring 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 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 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 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 higher-power 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 resiliency 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 technologies 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.
Chang-Diaz'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.
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?
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 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.
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--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
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.
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, 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 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.]
Appendix I
----------
Answers to Post-Hearing Questions
[GRAPHIC(S) NOT AVAILABLE IN TIFF FORMAT]
< [all]