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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS2014

Nuclear Thermal Propulsion (NTP): A Proven, Growth Technology for Fast Transit Human Missions to Mars

The "fast conjunction" long surface stay mission option was selected for NASA's recent Mars Design Reference Architecture (DRA) 5.0 study because it provided adequate time at Mars (approx. 540 days) for the crew to explore the planet's geological diversity while also reducing the "1-way" transit times to and from Mars to approx. 6 months. Short transit times are desirable in order to reduce the debilitating physiological effects on the human body that can result from prolonged exposure to the zero-gravity (0-gE) and radiation environments of space. Recent measurements from the RAD detector attached to the Curiosity rover indicate that astronauts would receive a radiation dose of approx. 0.66 Sv (approx. 66 rem)-the limiting value established by NASA-during their 1-year journey in deep space. Proven nuclear thermal rocket (NTR) technology, with its high thrust and high specific impulse (Isp approx. 900 s), can cut 1-way transit times by as much as 50 percent by increasing the propellant capacity of the Mars transfer vehicle (MTV). No large technology scale-ups in engine size are required for these short transit missions either since the smallest engine tested during the Rover program-the 25 klbf "Pewee" engine is sufficient when used in a clustered arrangement of three to four engines. The "Copernicus" crewed MTV developed for DRA 5.0 is a 0-gE design consisting of three basic components: (1) the NTP stage (NTPS); (2) the crewed payload element; and (3) an integrated "saddle truss" and LH2 propellant drop tank assembly that connects the two elements. With a propellant capacity of approx. 190 t, Copernicus can support 1-way transit times ranging from approx. 150 to 220 days over the 15-year synodic cycle. The paper examines the impact on vehicle design of decreasing transit times for the 2033 mission opportunity. With a fourth "upgraded" SLS/HLV launch, an "in-line" LH2 tank element can be added to Copernicus allowing 1-way transit times of 130 days. To achieve 100 to 120 day transit times, Copernicus' saddle truss/drop tank assembly is replaced by a "star truss" assembly with paired modular drop tanks to further increase the vehicle's propellant capacity. The HLV launch count increases (from approx. 5 to 7) and a fourth engine is needed to reduce total mission burn time and gravity losses. Using a "split mission" approach, the NTPS, in-line tank and the saddle truss/LH2 drop tank elements can be configured as a pre-deployed Earth Return Vehicle/propellant tanker supporting 90-day crewed mission transits. The split mission approach also eliminates the need for on-orbit assembly. Mission scenario descriptions, key features and operational characteristics for five different vehicle configurations are presented.

Borowski, Stanley K.↗
NASA NTRS2015

Subscale Validation of the Subsurface Active Filtration of Exhaust (SAFE) Approach to NTP Ground Testing

Brief History of NTP: Project Rover Began in 1950s by Los Alamos Scientific Labs (now Los Alamos National Labs) and ran until 1970s Tested a series of nuclear reactor engines of varying size at Nevada Test Site (now Nevada National Security Site) Ranged in scale from 111 kN (25 klbf) to 1.1 MN (250 klbf) Included Nuclear Furnace-1 tests Demonstrated the viability and capability of a nuclear rocket engine test program One of Kennedys 4 goals during famous moon speech to Congress Nuclear Engines for Rocket Vehicle Applications (NERVA) Atomic Energy Commission and NASA joint venture started in 1964 Parallel effort to Project Rover was focused on technology demonstration Tested XE engine, a 245-kN (55-klbf) engine to demonstrate startup shutdown sequencing. Hot-hydrogen stream is passed directly through fuel elements potential for radioactive material to be eroded into gaseous fuel flow as identified in previous programs NERVA and Project Rover (1950s-70s) were able to test in open atmosphere similar to conventional rocket engine test stands today Nuclear Furance-1 tests employed a full scrubber system Increased government and environmental regulations prohibit the modern testing in open atmosphere. Since the 1960s, there has been an increasing cessation on open air testing of nuclear material Political and national security concerns further compound the regulatory environment

Test Facilities↗
NASA NTRSDate not supplied

Additive Manufacture of Porous ZrC for NTP In-Core Insulators

Nuclear Thermal Propulsion (NTP) requires the use of in-core insulators to manage to thermal environment between high temperature fuel elements and lower temperature structural components. The unforgiving in-core operating conditions severely limit potential material candidates. Zirconium Carbide (ZrC) is a promising candidate due to a high melting temperature, high compressive strength, hardness, wear resistance, hydrogen compatibility, and low neutron absorption cross sections. However, fully dense ZrC is not an insulator but it has been found that the thermal conductivity of ZrC decreases by increasing porosity to approximately 60 % theoretical density (%TD). Previous methods for generating porous ZrC were difficult, expensive, and time consuming. Binder jet additive manufacture (AM) can print ceramic materials to near net shape. Binder jet AM is not utilized in many applications due to an inherently low post-sintering density on the order of 60 %TD. For this specific application the inherent lower density is leveraged as an advantage in production porous ZrC in order to control the thermal conductivity. A feasibility study was conducted to investigate binder jet AM parameter development for ZrC, heat treatment optimization (burn-out and sinter), microstructural characterization, mechanical testing, and thermal testing to generate near-net shape ZrC components with ~60 %TD with the desired thermal conductivity and mechanical strength.

Omar Mireles↗
NASA NTRSDate not supplied

Mini-Nozzles for Individual Fuel Elements for NTP Systems NETS

The Testing Reference Design (TRD) reactor and engine for Nuclear Thermal Propulsion (NTP) systems typically use a large single nozzle with regenerative cooling which contributes a significant portion of the engine mass. Furthermore, if a fuel element is damaged or the flow is otherwise compromised, stagnant or backflow is expected which would further damage the reactor and engine. Therefore, the current analysis attempts to solve this potential issue by considering individual, smaller nozzles allocated for each individual fuel element while also neglecting regenerative cooling flow due to lower hoop stresses from the chamber pressure. However, a material that can withstand the chamber temperatures should be considered such as molybdenum or tungsten or a mixture of the two.

Daria Nikitaeva↗
NASA NTRSDate not supplied

Capabilities of Single Launch NTP and Chemical Spacecrafts for Cis-Lunar Tug Missions

Renewed interest in the region between the Earth and the moon suggests that a tug operating between these two destinations will be most likely required in the near future. This report details a parametric spacecraft model which sizes a nuclear thermal propulsion or chemical propulsion spacecraft and compares their payload transport capabilities for missions to the moon. A spacecraft sized to fit in a single launch vehicle is assumed, and six launch vehicles are investigated. Maximum spacecraft payload mass and minimum mission transit time are compared between nuclear and chemical propulsion spacecrafts. For vehicles sized to the maximum capability of a launch vehicle, payloads of at least five metric tons are possible with either propulsion option; with nuclear thermal propulsion able to provide additional mass or reduced transit time when the spacecraft is sized to the maximum capability of the heaviest-lift launch vehicles. Transit times to the moon with a five-ton payload could be reduced by at least 0.2 days with a nuclear propulsion system.

Cis-lunar tug↗
NASA NTRSDate not supplied

Capabilities of Single Launch NTP and Chemical Spacecrafts for Cis-Lunar Tug Missions

Renewed interest in the region between the Earth and the moon suggests that a tug operating between these two destinations will be most likely required in the near future. This report details a parametric spacecraft model which sizes a nuclear thermal propulsion or chemical propulsion spacecraft and compares their payload transport capabilities for missions to the moon. A spacecraft sized to fit in a single launch vehicle is assumed, and six launch vehicles are investigated. Maximum spacecraft payload mass and minimum mission transit time are compared between nuclear and chemical propulsion spacecrafts. For vehicles sized to the maximum capability of a launch vehicle, payloads of at least five metric tons are possible with either propulsion option; with nuclear thermal propulsion able to provide additional mass or reduced transit time when the spacecraft is sized to the maximum capability of the heaviest-lift launch vehicles. Transit times to the moon with a five-ton payload could be reduced by at least 0.2 days with a nuclear propulsion system.

Cis-lunar tug↗
NASA NTRS2014

The Benefits of Nuclear Thermal Propulsion (NTP) in an Evolvable Mars Campaign

NTR: High thrust high specific impulse (2 x LOXLH2chemical) engine uses high power density fission reactor with enriched uranium fuel as thermal power source. Reactor heat is removed using H2propellant which is then exhausted to produce thrust. Conventional chemical engine LH2tanks, turbopumps, regenerative nozzles and radiation-cooled shirt extensions used --NTR is next evolutionary step in high performance liquid rocket engines During the Rover program, a common fuel element tie tube design was developed and used in the design of the 50 klbf Kiwi-B4E (1964), 75 klbf Phoebus-1B (1967), 250 klbf Phoebus-2A (June 1968), then back down to the 25 klbf Pewee engine (Nov-Dec 1968) NASA and DOE are using this same approach: design, build, ground then flight test a small engine using a common fuel element that is scalable to a larger 25 klbf thrust engine needed for human missions

Nuclear thermal rocket↗