Accelerating Deep Space Travel with Space Nuclear Propulsion

Summary

This congressional hearing examines the opportunities, technical hurdles, policy frameworks, and interagency/commercial collaborations involved in developing space nuclear propulsion systems. Expert witnesses discuss the merits and readiness of Nuclear Thermal Propulsion (NTP) and Nuclear Electric Propulsion (NEP) systems, addressing mission architectures, fuel requirements (HEU vs. HALEU), testing infrastructure, and timelines needed for human missions to Mars.

Title Page

ACCELERATING DEEP SPACE TRAVEL WITH SPACE NUCLEAR PROPULSION

HEARING BEFORE THE SUBCOMMITTEE ON SPACE AND AERONAUTICS OF THE COMMITTEE ON SCIENCE, SPACE, AND TECHNOLOGY OF THE HOUSE OF REPRESENTATIVES ONE HUNDRED SEVENTEENTH CONGRESS FIRST SESSION OCTOBER 20, 2021 Serial No. 117–35 Printed for the use of the Committee on Science, Space, and Technology Available via the World Wide Web: http://science.house.gov U.S. GOVERNMENT PUBLISHING OFFICE WASHINGTON : 2022

Committee and Subcommittee Roster

COMMITTEE ON SCIENCE, SPACE, AND TECHNOLOGY HON. EDDIE BERNICE JOHNSON, Texas, Chairwoman ZOE LOFGREN, California SUZANNE BONAMICI, Oregon AMI BERA, California HALEY STEVENS, Michigan, Vice Chair MIKIE SHERRILL, New Jersey JAMAAL BOWMAN, New York MELANIE A. STANSBURY, New Mexico BRAD SHERMAN, California ED PERLMUTTER, Colorado JERRY MCNERNEY, California PAUL TONKO, New York BILL FOSTER, Illinois DONALD NORCROSS, New Jersey DON BEYER, Virginia CHARLIE CRIST, Florida SEAN CASTEN, Illinois CONOR LAMB, Pennsylvania DEBORAH ROSS, North Carolina GWEN MOORE, Wisconsin DAN KILDEE, Michigan SUSAN WILD, Pennsylvania LIZZIE FLETCHER, Texas FRANK LUCAS, Oklahoma, Ranking Member MO BROOKS, Alabama BILL POSEY, Florida RANDY WEBER, Texas BRIAN BABIN, Texas ANTHONY GONZALEZ, Ohio MICHAEL WALTZ, Florida JAMES R. BAIRD, Indiana DANIEL WEBSTER, Florida MIKE GARCIA, California STEPHANIE I. BICE, Oklahoma YOUNG KIM, California RANDY FEENSTRA, Iowa JAKE LATURNER, Kansas CARLOS A. GIMENEZ, Florida JAY OBERNOLTE, California PETER MEIJER, Michigan JAKE ELLZEY, TEXAS VACANCY

SUBCOMMITTEE ON SPACE AND AERONAUTICS HON. DON BEYER, Virginia, Chairman ZOE LOFGREN, California AMI BERA, California BRAD SHERMAN, California ED PERLMUTTER, Colorado CHARLIE CRIST, Florida DONALD NORCROSS, New Jersey BRIAN BABIN, Texas, Ranking Member MO BROOKS, Alabama BILL POSEY, Florida DANIEL WEBSTER, Florida YOUNG KIM, California

C O N T E N T S October 20, 2021 Hearing Charter … Page 2

Opening Statements: Statement by Representative Don Beyer, Chairman, Subcommittee on Space and Aeronautics … Page 9; Written Statement … Page 10 Statement by Representative Brian Babin, Ranking Member, Subcommittee on Space and Aeronautics … Page 11; Written Statement … Page 13 Statement by Representative Eddie Bernice Johnson, Chairwoman, Committee on Science, Space, and Technology … Page 33; Written Statement … Page 33

Witnesses: Dr. Roger M. Myers, Co-Chair, Committee on Space Nuclear Propulsion Technologies, National Academies of Sciences, Engineering, and Medicine Oral Statement … Page 15; Written Statement … Page 17 Dr. Bhavya Lal, Senior Advisor for Budget and Finance, National Aeronautics and Space Administration Oral Statement … Page 34; Written Statement … Page 36 Mr. Greg Meholic, Senior Project Leader, The Aerospace Corporation Oral Statement … Page 41; Written Statement … Page 43 Mr. Michael French, Vice President, Space Systems, Aerospace Industries Association Oral Statement … Page 50; Written Statement … Page 52 Dr. Franklin Chang-Diaz, Founder and CEO, Ad Astra Rocket Company Oral Statement … Page 59; Written Statement … Page 61 Discussion … Page 65

Appendix: Answers to Post-Hearing Questions Dr. Roger M. Myers … Page 88 Dr. Bhavya Lal … Page 102 Mr. Greg Meholic … Page 121 Mr. Michael French … Page 132 Dr. Franklin Chang-Diaz … Page 141

Hearing Charter

SUBCOMMITTEE ON SPACE AND AERONAUTICS COMMITTEE ON SCIENCE, SPACE, AND TECHNOLOGY U.S. HOUSE OF REPRESENTATIVES

HEARING CHARTER Accelerating Deep Space Travel with Space Nuclear Propulsion October 20, 2021 10:00 a.m. EDT Online Via Zoom

PURPOSE The purpose of the hearing is to understand the opportunities and challenges of space nuclear propulsion for enabling deep space exploration, examine the status of NASA’s R&D activities and plans for space nuclear propulsion, and to consider government and industry contributions to and collaboration on advancing space nuclear propulsion, among other issues.

WITNESSES

Dr. Roger M. Myers, Co-Chair, Committee on Space Nuclear Propulsion Technologies, National Academies of Sciences, Engineering, and Medicine
Dr. Bhavya Lal, Senior Advisor for Budget and Finance, NASA
Mr. Greg Meholic, Senior Project Leader, The Aerospace Corporation
Mr. Michael French, Vice President, Space Systems, Aerospace Industries Association
Dr. Franklin Chang Diaz, Founder and CEO, Ad Astra Rocket Company

OVERARCHING QUESTIONS

What are the opportunities for space nuclear propulsion to enable deep space exploration, especially human missions to Mars?
What are the major challenges, including technical hurdles, for developing, testing, demonstrating, and using space nuclear propulsion systems, and what needs to be done to overcome them?
What are the respective capabilities and expertise within the federal government and commercial sectors that could contribute to maturing space nuclear propulsion technologies, and are there any gaps?
How are industry and government collaborating on advancing space nuclear propulsion?

BACKGROUND NASA has sent many orbiting spacecraft and robotic landers and rovers to Mars since the 1960s, but a crewed mission to the red planet would be significantly more challenging, requiring far more mass, power, and capabilities than even the most complex robotic missions to date. Numerous NASA studies and external reports identify advanced in-space propulsion as one of the most critical enabling capabilities. With chemical propulsion, transit times are six to nine months, with round-trip durations around three years due to orbital mechanics alignment constraints (occurring roughly every 26 months).

Space nuclear propulsion systems (NTP and NEP) can significantly reduce transit times and mission risk. In 2020, NASA STMD requested NASEM convene an ad hoc committee to assess technical and programmatic challenges, merits, and risks for baseline missions targeting 2039 launch dates.

Oral Proceedings: Opening Statements

Chairman BEYER. The hearing will come to order. Welcome to today’s hearing on ‘Accelerating Deep Space Travel with Space Nuclear Propulsion.’ If we are serious about deep space exploration to Mars with humans, we need to take bold steps. Space nuclear propulsion can produce thrust far more efficiently than conventional chemical systems, allowing for shorter trip times to Mars, reducing astronaut radiation exposure and expanding launch flexibility. Developing space-qualified fission reactors, cryogenic fluid management, and testing infrastructure present significant challenges. A recent National Academies study indicated readiness by 2039 (or cargo in 2033) requires aggressive action now.

Ranking Member BABIN. Space nuclear power and propulsion holds great promise for faster transit, reduced radiation, and increased operational payload. Historical projects like Rover, NERVA, and SNAP demonstrate the legacy of these concepts. Sustained strategy, objective comparisons between NEP and NTP, assessment of HEU versus HALEU fuel architectures, and close coordination across NASA, DARPA (DRACO), and the private sector are essential.

Chairwoman JOHNSON. For decades nuclear propulsion has been identified as an enabling technology for human Mars exploration. We must move from studies and talk to meaningful progress in R&D investment, safety standards, and workforce development.

Witness Oral Testimonies

Dr. ROGER M. MYERS. The NASEM consensus study assessed NTP (900s Isp) and megawatt-class NEP systems for a 2039 baseline Mars mission. Key findings: For NTP, no currently available fuels meet required operating temperatures (2700 K hydrogen exit) or lifetime; liquid hydrogen in-space long-term storage is unproven; full-scale ground testing combined with advanced modeling is required. For NEP, scaling subsystems by orders of magnitude is needed, though modular subsystem ground testing may suffice. Both systems offer substantial benefits but carry significant technical risks requiring immediate, balanced investment.

Dr. BHAVYA LAL. Nuclear fission systems are transformative for deep space. NASA STMD has prioritized surface power (which offers extensibility to NEP) and NTP development in response to congressional direction. NASA is collaborating with DOE, DOD (DARPA DRACO program), and commercial industry on reactor designs, LEU fuels, and cryogenic fluid management.

Mr. GREG MEHOLIC. SNPP offers twice the cycle efficiency of high-thrust chemical engines for NTP, and continuous megawatt power for NEP. Fission systems are launched in an ‘off’ (non-critical) state, making them fundamentally safer prior to deployment than RTGs. Tailored regulatory and testing frameworks are vital to accelerate development.

Mr. MICHAEL FRENCH. AIA emphasizes moving from study to action through three pillars: modernizing launch approval frameworks (NSPM-20, SPD-6), securing stable multi-year funding, and establishing clear congressional direction for in-space flight demonstrations.

Dr. FRANKLIN CHANG-DIAZ. High exhaust velocity is key to rocket efficiency. While NTP achieves ~9,000 m/s, nuclear electric plasma rockets (like VASIMR) achieve 30,000–50,000 m/s using electromagnetic fields to contain million-degree plasma, enabling Mars transit times under three months with scalable megawatt-class systems. An 88-hour high-power endurance test at 80 kW was recently completed.

Summary of Q&A and Discussions

Key topics covered in Member questions:

VASIMR Operation & Transit Profiles: Continuous low thrust creates continuous acceleration, cutting transit times dramatically compared to ballistic trajectories.
NASA Budget & Priorities: Discussion on FY2022 requests, prioritization of Lunar Fission Surface Power (10-40 kWe), and cross-cutting cryogenic fluid management.
Safety & Launch Approval: Under NSPM-20, tiered risk categories allow NASA administrator approval for non-HEU/fission launches.
Mission Timelines & Milestones: Exploration of realistic target dates (2033 vs 2039) given challenges in orbital assembly, Mars entry/descent/landing, and life support systems.
Fuel Architecture: Consensus that commercial adoption favors High-Assay Low-Enriched Uranium (HALEU) over Highly Enriched Uranium (HEU) due to nonproliferation and regulatory constraints, with only modest mass penalties at scale.
Terrestrial Synergies: Parallels between terrestrial microreactors (Project Pele, commercial SMRs) and space power/propulsion systems.

Appendix: Answers to Post-Hearing Questions

Detailed written responses from Dr. Roger Myers, Dr. Bhavya Lal, Mr. Greg Meholic, Mr. Michael French, and Dr. Franklin Chang-Diaz covering:

Requirements for cryogenic fluid management (liquid hydrogen storage at 20 K with boil-off reduction).
Technical trade studies between NTP and NEP architectures.
Feasibility and facility requirements for ground testing vs. in-space flight demonstrations.
Uranium fuel form maturation (TRISO, BISO, cermet, cercer) and domestic HALEU supply chains.
International competitive landscape (Russia and China programs in space fission power and megawatt NEP).
Detailed engineering schematics and performance metrics for the VASIMR magnetoplasma engine.