Evaluation of Recent Upgrades to the NESS (Nuclear Engine System Simulation) Code

Abstract

The Nuclear Thermal Rocket (NTR) concept is being evaluated as a potential propulsion technology for exploratory expeditions to the moon, Mars, and beyond. The need for exceptional propulsion system performance in these missions has been documented in numerous studies, and was the primary focus of a considerable effort undertaken during the Rover/NERVA program from 1955 to 1973. The NASA Glenn Research Center is leveraging this past NTR investment in their vehicle concepts and mission analysis studies with the aid of the Nuclear Engine System Simulation (NESS) code. This paper presents the additional capabilities and upgrades made to this code in order to perform higher fidelity NTR propulsion system analysis and design, and a comparison of its results to the Small Nuclear Rocket Engine (SNRE) design.

Small Reactor Designs Suitable for Direct Nuclear Thermal Propulsion: Interim Report

“…These papers have addressed neutronics modeling of the SNRE reactor core, 19 enrichment zoning options 20 for the SNRE, the SNRE reference stage, 21 integrated thermal-fluid-structural analysis of reactor core interior components, 22 and engine system level modeling and analyses. 23 A prior year effort included an extension of the SNRE design into the 111.2 kN (25,000 lb f ) thrust range. 24 Relevant extracts from the previously reported 111.2 kN evaluations results are summarized in Section 3.4.…”

“…23 The NESS code contains an option to calculate a suitable fuel element propellant orificing pattern to minimize fuel element temperature peaking, maintain the peak fuel temperature below a specified limit, and maximize the mixed mean propellant exit temperature. Performance characteristics are shown in Table 3 for the three lower thrust engine options evaluated.…”

Enrichment Zoning Options for the Small Nuclear Rocket Engine (SNRE)

“…Results from additional engine system performance evaluations such as reported in Ref. 8 are needed to incorporate inlet flow control and to assess the impact of using a minimum number of enrichment groups. …”

“…Initial efforts were focused on benchmarking methods and models against the Small Nuclear Rocket Engine (SNRE) and stage configuration documented in the Nuclear Engine Definition Study (NEDS) Preliminary reports 3,4 . Past papers have addressed neutronics modeling of the SNRE reactor core 5 , the SNRE reference stage 6 , integrated thermal-fluid-structural analysis of reactor core interior components 7 , engine system level modeling and analyses 8 , and an extension of the SNRE design into the 25,000 lbf thrust range 9 . Most nuclear thermal propulsion engine designs utilize uranium fuel enriched to 93 wt% 235 U.…”

The Nuclear Thermal Propulsion Stage (NTPS): A Key Space Asset for Human Exploration and Commercial Missions to the Moon

“…Engine Design, Analysis and Modeling is aimed at developing conceptual designs for small (~7.5 klb f ) demonstration engines and higher thrust-class (~25 klb f ) engines utilizing the candidate fuels discussed above. Stateof-the-art numerical models are being used to determine reactor core criticality, detailed energy deposition and control rod worth within the reactor subsystem [25,27,35], provide thermal, fluid and stress analysis of reactor fuel elements and core components [36,37], and predict engine operating characteristics and overall mass [38,39]; Task 4. Demonstration of Affordable Ground Testing is focused on maturing equipment requirements and cost estimates for a "proof-of-concept" validation test of the SAFE (Subsurface Active Filtration of Exhaust) [40,41] concept (also known as the "bore-hole" option) at the Nevada Test Site (NTS).…”