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The future of human exploration missions to Mars is dependent on solutions to the technology challenges being worked on by the National Aeronautics and Space Administration (NASA) and industry. One of the key architecture technologies involves propulsion that can transport the human crew from Earth orbit to other planets and back to Earth with the...
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... stage element was still able to stay within the 45-mT NASA SLS throw capability defined in previous architecture trades. Figure 5 shows the updated NTP Mars crew vehicle configuration with a three-NTP-engine system core and hydrogen tank, three in-line hydrogen tank stage elements, and the crew habitat sized for 1000+ day missions. ...
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... to 29% with no modification to the PoD. When adding features such as higher Isp, H2 OMS, and staging an in-line tank stage, the LEU NTP is 26% to 46% faster in transit time. The same LEU NTP architectures outperform a "hybrid" propulsion approach by 33% to 57% in reduced transit times. Architectures that use the LEU NTP PoD configuration shown in Fig. 5 or the LEU NTP PoD with enhancements will keep astronauts at a lower risk in regard to GCR exposure on all Mars mission opportunities with reduced transit ...
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Nuclear thermal propulsion (NTP) systems have been studied in both the USA and the former Soviet Union since the 1950s for use in space science and exploration missions. NTP uses nuclear fission to heat hydrogen to very high temperatures in a short amount of time so that the hydrogen can provide thrust as it accelerates through an engine nozzle. Be...
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... Studies have also looked at using 15 k-lbf (66.7 kN) and 16.5 k-lbf (73.4 kN) engine classes for a host of missions to the outer planets using both thrust-only and bimodal concepts [14,15]. Finally, there has also been a study on the use of a 25 k-lbf (111.2 kN) engine for missions to Jupiter and Uranus [16]. ...
Nuclear thermal propulsion (NTP) has emerged as a promising technology for enhancing the capabilities of robotic missions in space exploration. This paper investigates and analyzes the tradeoffs and sensitivity associated with utilizing NTP systems for robotic missions to the outer planets. The engine trade results for Jupiter and Neptune rendezvous missions using expendable configuration have demonstrated that the thrust range of 12.5–15 k-lbf (55.6–66.7 kN) can enable new frontiers and flagship-class missions with minimum initial mass in low Earth orbit. The specific impulse sensitivity analysis has shown that using a 13 k-lbf (57.8 kN) engine with an [Formula: see text] as low as 850 s can enable flagship-class missions to the gas giants in a direct transfer trajectory.
... The goal was to determine the NTP performance towards delivering 1500 kg payload to Neptune orbit. The mission to Uranus was studied using LEU NTP engine system design and utilizing SLS Block 2 launch vehicle to deliver the spacecraft in LEO parking orbit [24]. Due to the enhanced performance of the launch vehicle and high thrust NTP system, a payload of about 3000 kg can be inserted into Uranus orbit. ...
The exploration of outer planets and icy moons demands advanced propulsion and power solutions to overcome the limitations of chemical and solar-electric systems. This paper highlights the transformative potential of Nuclear Thermal Propulsion (NTP) and nuclear power systems for deep-space missions. NTP systems, with their high thrust and specific impulse, enable reduced trip times and increased payload capacity, facilitating flagship-class missions to distant worlds. Nuclear power systems provide sustained energy for high-power instruments, such as ice-penetrating radars, LIDARs, and mass spectrometers, critical for investigating subsurface oceans and detecting organic compounds. Additionally, they enable high-rate data transmission over vast distances, ensuring maximum scientific return from robotic missions to the outer solar system.
... The goal was to determine the NTP performance towards delivering 1500 kg payload to Neptune orbit. The mission to Uranus was studied using LEU NTP engine system design and utilizing SLS Block 2 launch vehicle to deliver the spacecraft in LEO parking orbit [45]. Due to the enhanced performance of the launch vehicle and high thrust NTP system, a payload of about 3000 kg can be inserted into Uranus orbit. ...
... However, to be effective in these applications, NTP spacecraft require other developments, such as cryocoolers, in order to enable the necessary long-term hydrogen propellant storage [3]. NTP engines may be more useful in the near term in single-burn applications such as an Earth departure booster spacecraft for sending robotic science missions to the outer planets where long-term propellant storage is not necessary [4]. In addition to considering more near-term applications of NTP spacecraft, we can also consider how to design the NTP engines to be a more near-term technology, and one method of achieving this is to consider propellant feed systems that minimize coupling with the reactor. ...
... The following calculations are based on methods for chemical and NTP rocket engines described in Space Propulsion Analysis and Design [5]. The propellant mass flow rate is estimated Article in Advance / AUERON AND DALE THOMAS for these thrust levels with an I sp of 900 s using the relation of rocket engine thrust to I sp , simplified to assume an infinite nozzle in space, in Eq. (4). ...
This paper describes an analysis of the viability of electric-pump-fed nuclear thermal propulsion (EPFS NTP) for space missions. EPFS is an alternative to the turbopumps typically employed by high-impulse rocket engines, but it is not yet clear if they are suitable for this application. The method employed by this analysis utilizes the rocket equation to determine whether EPFS NTP spacecraft are capable of delivering payloads to Jupiter and Saturn, subject to the mass and geometry constraints imposed by near-term launch vehicles. The analysis found that 7.5 klbf EPFS NTP can deliver up to 3000 kg to Jupiter and 2000 kg to Saturn, and that spacecraft with higher thrust EPFS NTP engines deliver smaller payloads. This analysis provides confidence that EPFS NTP can enable a space mission of interest, and therefore EPFS can be considered as an alternative to turbomachinery for near-term NTP engine development.
... These promising results from NTP Project team members reinforced the academic research results, and refinements of HALEU engine designs continued in subsequent years [ 30 , 31 ]. Additionally, mission analyses were performed using HALEU fueled NTP engines, with results comparable to mission designs using HEU fuels [30] . ...
This paper describes the current research and development effort s currently underway within the United States on Nuclear Thermal Propulsion (NTP), with a particular focus on the Demonstration Rocket for Agile Cislunar Operations (DRACO) project, a joint effort of the United States Defense Advanced Projects Agency and the National Aeronautics and Space Administration. However, to put the DRACO project into context, the prior United States’ prior effort s on NTR are described and the foundation those efforts pro- vided to enable DRACO. The impact of NTP propulsion on both human and scientific exploration of the Solar System will also be discussed. And finally, the topic of advanced NTP propulsion will be addressed, including liquid fuel NTP engines.
... Studies have also looked at using 15 klbf and 16.5 klbf engine class for host of missions to the outer planets using both thrust only and bi-modal concepts [15,16]. Finally, there has also been a study on the use of 25 klbf engine for missions to Jupiter and Uranus [17] This paper presents the trade space exploration of the NTP engine parameters for the selected Design Reference Missions (DRM) in order to determine the enabling engine thrust of NTP system for missions to the outer solar system exploration. Section III discusses the NTP mission model developed using MBSE along with the selected design reference missions for trade space exploration. ...
Nuclear Thermal Propulsion (NTP) has emerged as a promising technology for enhancing the capabilities of robotic missions in space exploration. This paper aims to investigate and analyze the trade-offs and sensitivity associated with utilizing NTP systems for robotic missions to the outer planets. The engine trade results for Jupiter and Neptune rendezvous mission using expendable configuration has demonstrated that the thrust range of 12.5 klbf to 15 klbf can enable flagship class missions with minimum IMLEO. The specific impulse sensitivity analysis has shown that using a 13 klbf engine with as low was 850 s can enable flagship class missions to the Gas giants in a direct transfer trajectory.
... Current Mars transfer vehicle (MTV) mission architectures consider vehicle aggregation in either low Earth orbit (LEO) or lunar distant retrograde orbit (LDRO). These architectures consider maximizing both the volume and mass capabilities of the Space Launch System (SLS) [13,14]. Therefore, for aggregating these vehicles using only what can be brought from Earth, a higher vehicle engine I sp is key to decreasing the number of launches by reducing the propellant mass, and thus the cost of a vehicle because launch costs can be incredibly high, especially when the SLS [15] is considered. ...
... The purpose of this study is to evaluate the vehicle trades when using different propellants and propulsion systems. These include propellant grade water and ammonia for A-NTP engines [29], electrolyzed water for the reference RL10 engine [4], methane and oxygen for Relativity Space's Aeon-1 engine [30], pure hydrogen for H-NTP engines [14], and electrolyzed water for the liquid-oxygen (LOX) augmented nuclear thermal rocket engine [31]. These same propulsion systems were analyzed for Mars missions in previous works [23,24]. ...
... Future work will consider multistage LADVs. The vehicle analysis code was validated by comparison [49] against the reference mission architecture [14,26] and was described in previous work [23]. ...
Recently, NASA has pushed for returning humans to the moon sustainably with in situ resource utilization as the central focus. The moon has an abundance of water that is proposed to be electrolyzed into hydrogen and oxygen to be used as propellant. Other volatiles such as ammonia, carbon dioxide, and methane are also present. A mission architecture for a lunar ascent/descent vehicle (LADV) from the Polytechnic University of Turin and nuclear thermal propulsion (NTP) engine models from the University of Alabama in Huntsville were used to compare in-situ-derived propellants for a LADV. This study considered a LADV originating from the lunar surface, delivering a payload in the lunar distant retrograde orbit, and returning to the lunar surface for retanking. This research analyzed the impacts on this mission of using hydrogen NTP, water/ammonia NTP, liquid-oxygen augmented nuclear thermal rocket, and Aeon 1 methane–oxygen engines using the selected architecture and tools. The results were compared to the reference hydrogen–oxygen RL10 engine. The propulsion system comparison analysis showed that combustion engines will offer better overall performance than NTP-based engines due to a 50% decrease in propellant volume, a 20% decrease in dry mass, and a lower propellant mass than the water and ammonia NTP systems. Both the hydrogen–oxygen and methane–oxygen propulsion systems will have similar propellant masses when compared to other systems. This is due to the order of magnitude higher mass of the NTP engines, with the highest mass contribution coming from the reactor. However, both water and ammonia alternative propellant NTP engines can still be viable candidates for the usage of these minimally processed propellants to satisfy this mission.
... Therefore, when these vehicles return from the first mission, they will be parked in LDRO to be retanked at a propellant depot and prepared for their next mission. However, to simplify the analysis and determine the effects of alternative propellant NTP (A-NTP) on just the vehicle architecture, the propellant required is assumed to be available in LDRO according to the Commercial Lunar Propellant Architecture study [17][18][19]. ...
... Furthermore, if aggregation of a vehicle in a baseline architecture does not occur in LDRO, the aggregation will need to be moved to LDRO as retanking the vehicle with a propellant denser than hydrogen will only be effective in the lunar vicinity due to the lower I sp of a non-pure-hydrogen propellant. Therefore, vehicles based on a non-pure-hydrogen propellant will require higher propellant mass, thereby causing the Earth launch vehicles to be mass limited rather than volume limited as in the case of vehicle requiring only pure hydrogen as the propellant [18][19][20][21]. ...
... As the vehicle performs the burns, the drop tanks are discarded. Given that reusability is considered, the vehicle would be cycling between Mars orbit and LDHEO with retanking taking place in LDRO (140 m∕s difference between LDHEO [18]). Figure 5 shows the vehicle architecture of the Mars opposition vehicle that would be aggregated in LDRO. ...
Recently, NASA has pushed for returning humans to the moon, with in-situ resource utilization being the key capability to provide sustainability. One of the potential future developments could be a propellant depot in lunar distant retrograde orbit. Using Aerojet Rocketdyne Mars mission architectures and University of Alabama in Huntsville Nuclear Thermal Propulsion (NTP) engine models, this research analyzed the impacts of using chemical [Formula: see text] and [Formula: see text] engines as well as the liquid-oxygen (LOX) Augmented Nuclear Thermal Rocket (LANTR) engines for these missions and compared their performances to the reference hydrogen-based NTP (H-NTP) engines all the while assuming a propellant depot at lunar distant retrograde orbit. For a human mission to Mars originating in the lunar distant retrograde parking orbit, the LANTR engines will offer better overall performance than H-NTP engines with a predicted 55.6% decrease in propellant volume, 39% decrease in vehicle dry mass, and 50% decrease in the number of aggregation launches. This is due to LANTR’s 22% higher specific impulse than conventional [Formula: see text] chemical propulsion systems, three times higher density than pure hydrogen, and 440% higher thrust than the baseline H-NTP engines. However, these benefits come at the cost of the propellant mass, which is 32.4% higher for the conjunction class mission and 106.7% higher for the opposition class mission than the baseline H-NTP system.
... Numerous studies have been conducted toward demonstrating the feasibility of NTP-powered robotic missions for deep space exploration. [16][17][18][19][20][21][22] Among many development challenges such as very high cost and long schedule of completing development, qualification, and production of these engines, NTP systems for science missions have also not been aggressively considered in the past due to their large mass and the inability to launch them on a single ...
This paper discusses the current challenges of exploration of outer planets and proposes a nuclear thermal propulsion (NTP) system for future deep space exploration missions. The mission design problem with respect to the NTP system is presented where it is proposed that NTP-powered missions need to integrate the requirements and constraints of mission objective, spacecraft design, NTP system design, and launch vehicle limits into a self-consistent model. The paper presents a conceptual NTP-powered rendezvous mission to Neptune that uses a single high-performance–class commercial launch vehicle to deliver over 2 mT of useful payload in a direct transfer trajectory with total trip time being under 16 years.
... Due to modern regulatory concerns, the uranium enrichment is limited to the use of High-Assay Low Enriched Uranium (HALEU) with a cap of 19.75%. Recent studies focus on qualifying such LEU systems for nearterm crewed missions to Mars (Joyner et al., 2020a(Joyner et al., , 2020b. Moreover, these efforts are driven and assisted by tailored computational models (DeHart, 2021;Gustafson, 2021). ...
Nuclear thermal propulsion offers high thrust and specific impulse engine capabilities for future manned missions to Mars and beyond. Legacy nuclear engine designs developed and experimented with highly enriched uranium engine systems. Currently, extensive research is performed to analyze the behavior of low enriched uranium reactors to meet the current regulation limits. Most of these analyses are focused on complicated multiphysics steady-state calculations to determine key engine performance parameters. Often time these computational frameworks decouple various engine components in the calculation phase, resulting in uncertainties of the engine's performance. The challenges and limiting factors associated with transient operations in low enriched uranium reactors, such as engine startups and shutdowns, must be well understood. The objective of this paper is to present a reduced-order computational transient framework that examines a system-wide low enriched uranium nuclear thermal engine. The framework includes a steady-state solver used to converge on pumping requirements and conserve enthalpy prior to the start of a transient. The novel approach here relies on the steady-state component within the framework to generate operational maps. The latter indicate the feasibility of control based on nozzle chamber conditions for a given engine design in lieu of publicly unavailable pump curves. The framework is applied to investigate uprate in power maneuvers in conjunction with sensitivity studies to show the feasibility of an engine startup.
