The readiness of commercial Hall thruster technology is evaluated for near-term use on competitively-award, cost-capped science missions like the NASA Discovery program. Scientists on these programs continue to place higher demands on mission performance that must trade against the cost and performance of propulsion system options. Solar electric propulsion (SEP) systems can provide enabling or enhancing capabilities to several missions, but the widespread and routine use of SEP will only be realized through aggressive cost and schedule risk reduction efforts. Significant cost and schedule risk reductions can potentially be realized with systems based on commercial Hall thruster technology. The abundance of commercial suppliers in the United States and abroad provides a sustainable base from which Hall thruster systems can be cost-effectively obtained through procurements from existing product lines. A Hall thruster propulsion system standard architecture for NASA science missions is proposed. The BPT-4000 from Aerojet is identified as a candidate for near-term use. Differences in qualification requirements between commercial and science missions are identified and a plan is presented for a low-cost, low-risk delta qualification effort. Mission analysis for Discovery-class reference missions are discussed comparing the relative cost and performance benefits of a BPT-4000 based system to an NSTAR ion thruster based system. The BPT-4000 system seems best suited to destinations located relatively close to the sun, inside approximately 2 AU. On a reference near Earth asteroid sample return mission, the BPT-4000 offers mass performance competitive with or superior to NSTAR at much lower cost. Additionally, it is found that a low-cost, mid-power commercial Hall thruster system may be a viable alternative to aerobraking for some missions. Suggestions for the near- and far-term implementation of commercial Hall thrusters on NASA science missions are discussed.

/pdf/evaluation-of-a-4-5-kw-commercial-hall-thruster-system-for-3o1b3u0poe.pdf

Evaluation of a 4.5 kW Commercial Hall Thruster System for NASA Science Missions

Liquid Acquisition Devices for Advanced In-Space Cryogenic Propulsion Systems

One way to reduce the carbon dioxide emissions of heavy vehicles is to install regenerative braking systems. These capture the kinetic energy of the vehicle during braking and store it, in order to feed it back into the drivetrain during acceleration. It is not clear, however, which of the many available technologies should be used to implement this regenerative braking.This report explores the different possible energy capture and storage technologies for regenerative braking, including electrical, kinetic, hydraulic and compressed air. The basic systems are plotted on a selection chart, and an optimal selection methodology is used to aid in the selection of the lightest and smallest system for regenerative braking.The results of this comparison and selection show that hydraulic energy storage is likely to be 33% smaller and 20% lighter than the closest electrical counterparts and is therefore a logical selection for regenerative braking on the trailers of heavy goods vehicles.

http://journals.sagepub.com/doi/pdf/10.1177/0954407011433395

Comparison of regenerative braking technologies for heavy goods vehicles in urban environments

A titanium-lined, composite overwrapped pressure vessel (COPV) for helium pressurant storage was designed for a commercial spacecraft. This tank has a nominal propellant volume of 81.4 liters (4,967 cubic inches) and a nominal weight of 11.7 kg (25.8 pounds). The maximum expected operating pressure is 331 bar (4,800 psi). Proof pressure requirement is 414 bar (6,000 psi), and the minimum burst pressure is 497 bar (7,200 psi). The pressurant tank design is based on a flightqualified pressurant tank to take advantage of its design and flight heritage. To minimize risk, the pressurant tank is designed to use only existing manufacturing technology, processes, and procedures. Manufacturing cost is minimized by using existing tooling to the fullest extent.

Design and manufacture of a composite overwrapped pressurant tank assembly

Within the last ten years, the commercial communications satellite industry has seen increasing demand for satellites with larger capacity and longer on-orbit life. Both requirements lead to the development of propellant tanks with increasing volumetric capacity. However, due to the size limitation of launch vehicles, satellites and, therefore, satellite propellant tanks, can only grow in length rather than girth. As the traditional monolithic titanium tanks grew longer, they became less mass efficient, and technical, economical, and compliance issues demanded a new approach to the design and fabrication of satellite propellant tanks.

Hybrid propellant tanks for spacecraft and launch vehicles

A unique titanium-lined, carbon fiber overwrapped Xenon storage pressure vessel was designed for an aerospace application. This tank has a nominal propellant volume of 1980 cubic inches and a nominal weight of 13.5 pounds. The operating pressure is 2500 psi, and the minimum burst pressure is 3750 psi. Due to limited space aboard the spacecraft, the tank was designed to fit within a conical envelope. This conical shape presented several major challenges for analysis, design and manufacture. Nonlinear material and geometric modeling techniques were used to analyze this tank. Stress analysis shows positive margins of safety for pressure cycle fatigue, vibration fatigue and minimum burst pressure over the design requirements. The liner was constructed from commercially pure (CP) titanium. CP titanium was chosen due to its relative high strength, excellent corrosion and oxidation resistance characteristics, superb weldability, good low and high cycle fatigue characteristics, and competitive manufacturing cost. The overwrap consists of high strength Torayca T1000GB carbon fiber and Shell Epon 826 cured resin system. Four composite layers were applied, two helical and two hoop wraps. A complete qualification program was conducted to verify the tank design, including two destructive burst pressure tests. A leak-beforeburst demonstration was also performed. The tank qualification program was successfully completed on 28 March 1996.

Design and manufacture of a composite overwrapped xenon conical pressure vessel

Design, development, qualification, and manufacture of the HS 601 propellant tank

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Design and manufacture of a composite overwrapped xenon conical pressure vessel

Design, development, qualification, and manufacture of the HS 601 propellant tank