NEXT Ion Propulsion System Configurations and Performance for Saturn System Exploration

Abstract

The successes of the Cassini/Huygens mission have heightened interest to return to the Saturn system with focused robotic missions. The desire for a sustained presence at Titan, through a dedicated orbiter and in-situ vehicle, either a lander or aerobot, has resulted in definition of a Titan Explorer flagship mission as a high priority in the Solar System Exploration Roadmap. The discovery of active water vapor plumes erupting from the "tiger stripes" on the moon Enceladus has drawn the attention of the space science community. The NASA's Evolutionary Xenon Thruster (NEXT) ion propulsion system is well suited to future missions to the Saturn system. NEXT is used within the inner solar system, in combination with a Venus or Earth gravity assist, to establish a fast transfer to the Saturn system. The NEXT system elements are accommodated in a separable Solar Electric Propulsion (SEP) module, or are integrated into the main spacecraft bus, depending on the mission architecture and performance requirements. This paper defines a range of NEXT system configurations, from two to four thrusters, and the Saturn system performance capability provided. Delivered mass is assessed parametrically over total trip time to Saturn. Launch vehicle options, gravity assist options, and input power level are addressed to determine performance sensitivities. A simple twothruster NEXT system, launched on an Atlas 551, can deliver a spacecraft mass of over 2400 kg on a transfer to Saturn. Similarly, a four-thruster system, launched on a Delta 4050 Heavy, delivers more than 4000 kg spacecraft mass. A SEP module conceptual design, for a two thruster string, 17 kW solar array, configuration is characterized. Nomenclature

Reduction of Saturn Orbit Insertion Impulse Using Deep-Space Low Thrust

“…The difference is so large that the same result holds for different launchers. Even for an Atlas V 551, which has a sensitivity 50% smaller ( [36]), the lowest C 3 remains the obvious choice. This is a natural consequence The Jupiter GA is modeled with the patched conics method.…”

“…Such a large initial energy requires a powerful launcher and severely limits the mass injected. For example, a Delta IV Heavy (4050H) is only capable of accelerating a 1500 kg payload at this C 3 level [36]. † Obviously, this is just a partial analogy because the excess speed is a scalar value.…”

An Overview of Recent Developments in Electric Propulsion for NASA Science Missions

“…As shown in Figure 1, the NEXT system consists of a highperformance, 7-kW ion thruster; a high-efficiency, 7-kW power processor unit (PPU); a highly flexible xenon propellant management system (PMS); a lightweight engine gimbal; and key elements of a digital control interface unit (DCIU) including software algorithms [5][6][7][8][9]. The NEXT team consists of NASA GRC as technology project lead, JPL as system integration lead, Aerojet as Prototype (PM) thruster, PMS, and DCIU simulator developer, and L3…”

Recent electric propulsion development activities for NASA science missions

“…As shown in Figure 1, the NEXT system consists of a highperformance, 7-kW ion thruster; a high-efficiency, 7-kW power processor unit (PPU); a highly flexible xenon propellant management system (PMS); a lightweight engine gimbal; and key elements of a digital control interface unit (DCIU) including software algorithms. [5][6][7][8] The NEXT team consists of NASA GRC as technology project lead, JPL as system integration lead, Aerojet as Prototype Model (PM) thruster, PMS, and DCIU simulator developer, and L3 Communications ETI as PPU developer. This design approach was selected to provide future NASA science missions with the greatest value in mission performance benefit at a low total development cost.…”