Gani B. Ganapathi

The Ion Propulsion System For Dawn

Summary The Dawn mission will be the first use of ion propulsion on a full up science mission for NASA. The ion propulsion system for Dawn is based on that demonstrated on Deep Space 1 with modifications necessary to accommodate multiple thrusters, to make the system single fault tolerant, to reduce the mass of the mechanical gimbals, and to accommodate a much larger propellant load. To rendezvous with the two heaviest main-belt asteroids, Vesta and Ceres, Dawn will carry 450 kg of xenon, whereas DS 1 carried only 8 1.5 kg of xenon. Acknowledgements The work described in this paper was conducted, in part, by the Jet Propulsion Laboratory, California Institute of Technology, under contract to the National Aeronautics and Space Administration. References 1. 2. 3. 4. 5. 6. M. D. Rayman, P. Varghese, D. H. Lehman, and L. L. Livesay, “Results From The Deep Space 1 Technology Validation Mission,’D IAA-99- IAA. 1 1.2.01, Presented at the 50th International Astronautical Congress, Amster#am, The Netherlands, 4-8 October, 1999, Acta Astronautica 47, p. 475 (2000). M. D. Rayman and P. Varghese, “The Deep Space 1 Extended Mission,” Acta Astronautica Brophy, J. R., et al., “Ion Propulsion System (NSTAR) DS 1 Technology Validation Report,” JPL Publication 00-1 0, October 2000. J. E. Polk, et al., “Validation of the NSTAR Ion Propulsion System on the Deep Space One Mission: Overview and Initial Results,” AIAA 99-2274, presented at the 35th Joint Propulsion Conference and Exhibit, 20-24 June 1999, Los Angeles, California. J. E. Polk, et al., “Demonstration of the NSTAR Ion Propulsion System on the Deep Space One Mission, IEPC-01-075, Presented @t the 27th International Electric Propulsion iconference, Pasadena, CA, 15- 19 October, 2001. Brophy,

The Hardware Challenges for the Mars Exploration Rover Heat Rejection System

The primary objective of the Mars Exploration Rover (MER) 2003 Project focused on the search for evidence of water on Mars. The launch of two identical flight systems occurred in June and July of 2003. The roving science vehicles are expected to land on the Martian surface in early and late January of 2004, respectively. The flight system design inherited many successfully features and approaches from the Mars Pathfinder Mission. This included the use of a mechanically‐pumped fluid loop, known as the Heat Rejection System (HRS), to transport heat from the Rover to radiators on the Cruise Stage during the quiescent trek to Mars. While the heritage of the HRS was evident, application of this system for MER presented unique and difficult challenges with respect to hardware implementation. We will discuss these hardware challenges in each HRS hardware element: the integrated pump assembly, cruise stage HRS, lander HRS, and Rover HRS. These challenges span the entire development cycle including fabrication, as...

High Density Thermal Energy Storage With Supercritical Fluids

A novel approach to storing thermal energy with supercritical fluids is being investigated, which if successful, promises to transform the way thermal energy is captured and utilized. The use of supercritical fluids allows cost-affordable high-density storage with a combination of latent heat and sensible heat in the two-phase as well as the supercritical state. This technology will enhance penetration of several thermal power generation applications and high temperature water for commercial use if the overall cost of the technology can be demonstrated to be lower than the current state-of-the-art molten salt using sodium nitrate and potassium nitrate eutectic mixtures. An additional attraction is that the volumetric storage density of a supercritical fluid can be higher than a two-tank molten salt system due to the high compressibilities in the supercritical state.This paper looks at different elements for determining the feasibility of this storage concept — thermodynamics of supercritical state with a specific example, naphthalene, fluid and system cost and a representative storage design. A modular storage vessel design based on a shell and heat exchanger concept allows the cost to be minimized as there is no need for a separate pump for transferring fluid from one tank to another as in the molten salt system. Since the heat exchangers are internal to the tank, other advantages such as lower parasitic heat loss, easy fabrication can be achieved.Results from the study indicate that the fluid cost can be reduced by a factor of ten or even twenty depending on the fluid and thermodynamic optimization of loading factor. Results for naphthalene operating between 290 °C and 475 °C, indicate that the fluid cost is approximately

Effect of Laminar and Turbulent Buoyancy-Driven Flows on Thermal Energy Storage using Supercritical Fluids

3/kWh compared with

Design and Testing of an Active Heat Rejection Radiator with Digital Turn-Down Capability

25-

Fluid Line Evacuation and Freezing Experiments for Digital Radiator Concept

50/kWh for molten salt. When the storage container costs are factored in, the overall system cost is still very attractive. Studies for a 12-hr storage indicate that for operating at temperatures between 290–450 °C, the cost for a molten salt system can vary between

Mars Exploration Rover Heat Rejection System Performance – Comparison of Ground and Flight Data

66/kWh to

Thermal Testing of Organic Fluids for Supercritical Thermal Energy Storage Systems

184/kWh depending on molten salt cost of

A 5 kWht Lab-Scale Demonstration of a Novel Thermal Energy Storage Concept With Supercritical Fluids

2/kg or a more recent quote of

Design and Modeling of a Radiator with Digital Turn-Down Capability under Variable Heat Rejection Requirements

8/kg. In contrast, the cost for a 12-hr supercritical storage system can be as low as