R. Joseph Cassady

• MS Aeronautics and Astronautics
• Managing Director at Aerojet Rocketdyne

NASA and its international partners have identified an exciting plan for opening up cislunar space and making the first steps toward human exploration of Mars in the 2020s. 1 Aerojet Rocketdyne is working with NASA to develop higher power Electric Propulsion (EP) in support of this vision. The Advanced Electric Propulsion System (AEPS) is being dev...

A status update on the advanced electric propulsion system work being performed in support of NASA's exploration program.

NASA is moving forward with plans to send humans beyond low Earth orbit to explore the Moon and Mars. To prepare for this ambitious activity, technology development of a 13 kW class electric thruster has been underway for several years to improve the ability to support human exploration with an advanced power and propulsion capability. The technolo...

Future human exploration missions to Mars are being studied by NASA, industry and academia. Many approaches to the Mars mission are being examined that use various types of propulsion for the different phases of the mission. The choice and implementation of propulsion system options can be optimally determined based on specific mission criteria suc...

NASA is currently underway developing the Space Launch System (SLS) to carry crew and cargo beyond low Earth orbit (LEO). The heavy lift capabilities of the SLS will enable spacecraft and mission architecture flexibility not achievable with current or proposed alternative, medium and heavy lift launch vehicles. The SLS is being designed in an evolu...

This study examines the impact of the launch capabilities provided by the planned Space Launch System (SLS) Block 2 vehicle on the solar electric propulsion (SEP) power levels required for large cargo prepositioning missions to Mars orbit. Our analysis shows that the additional launch capability planned for the SLS vehicle enables a dramatic reduct...

There is growing consensus within the international space community that the surface of Mars is the ultimate destination for human exploration efforts over the next two decades. As this consensus solidifies, the focus will turn to the necessary steps and associated capabilities that will be required to execute such a challenging mission. It is desi...

Nuclear and radioisotope powered electric thrusters are being developed as primary in space propulsion systems for potential future robotic and piloted space missions. Possible applications for high-power nuclear electric propulsion include orbit raising and maneuvering of large space platforms, lunar and Mars cargo transport, asteroid rendezvous a...

A trade study is carried out for the design of electric propulsion based lunar robotic precursor missions. The focus is to understand the relationships between payload mass delivered, electric propulsion power, and trip time. The results are compared against a baseline system using chemical propulsion with LOX/H2. The major differences between the...

The increased interest in NASA exploration missions to the outer planets has spurred a revival in interest in applications of radioisotope power to propulsion for the spacecraft. This concept requires a closely coupled systems analysis of the power conv ersion, power management and distribution (PMAD) and the electric propulsion subsystems because...

The sta:us of development of a Direct Drive Ha!! Thruster System is presented. 13 the first part. a s:udy of the impacts to spacecraft systems and mass benefits of a direct-drive architecture is reviewed. The study initially examines four cases of SPT-100 and BPT-4000 Hall thrusters used for north-south station keeping on an EXPRESS-like geosynchro...

Electric propulsion has emerged as a cost-effective solution to a wide range of satellite applications. Robust development of the near-Earth infrastructure that will enable Mars exploration can also rely upon solar-electric powered vehicles. Some of these options will be discussed as well. The POWOW concept is a solar-electric propelled spacecraft...

The Electric Propulsion Space Experiment (ESEX) flew in 1999 on the Air Force Space Test Program Advanced Research and Global Observation Satellite. ESEX was initiated to address potential in-space operational issues associated with the use of high-power electric propulsion. Potential issues included plume deposition, electromagnetic interference,...

The design and testing of a micro-Pulsed Plasma Thruster (PPT) is presented. Developed for the University of Washington's Dawgstar nanosatellite, the micro-PPT will provide formation keeping, orbit maintenance and attitude control functions to enable the smallest known spacecraft with an active propulsion system. Dawgstar, funded by Defense Advance...

A survey of potential applications for pulsed plasma thrusters is given. The range of potential functions proposed for a PPT is defined, organized and critically evaluated. Spacecraft missions are defined and organized according to recognized mission categories. The full range of opportunities for PPT application are listed and discussed. A signifi...

The AFOSR/DARPA University Nanosat program aims to produce a small fleet of nanosatellites. Among the most ambitious is the “Dawgstar” from the University of Washington. It proposes to use micro-PPTs to formation fly with two other student-built satellites in a constellation known as ION-F. Dawgstar, planned for launch in 2001, provides a useful te...

A new attitude control strategy is described using pulsed plasma thrusters (PPTs) as actuators. PPTs offer several advantages over conventional actuators such as reaction wheels, cold gas thrusters, or small chemical thrusters. These advantages derive from its simple, robust design and high performance capability. A PPT system is composed of electr...

Guidelines for improvements in arcjet performance based on a simplified analysis of advanced mission requirements are presented, The results of this analysis clearly show that to remain competitive with next-generation electric propulsion devices, significant increases in the specific impulse of present arcjet technology must be achieved, Of the va...

Pulsed plasma thrusters (PPT's) offer the combined benefits of extremely low average electric power requirements (1 to 150 W), high specific impulse (approximately 1000 s), and system simplicity derived from the use of an inert solid propellant. Potential applications range from orbit insertion and maintenance of small satellites to attitude contro...

A limited end-to-end chamber verification of a 26 kW arcjet propulsion system to be flown on the Air Force P91-1 spacecraft in 1995 is addressed. The arcjet Advanced Technology Transition Demonstration program encompasses a series of integrated tests with various combinations of system elements culminating with an integrated test of all the major f...

This study examined the utility of electric propulsion for orbit maintenance and maneuvering for a wide range of satellite masses. Candidate thrusters included the Russian Hall current devices (SPTs) recently introduce to the West. Updated performance data was used for arcjet, SPT, and ion thrusters. Using a first order systems-level analysis, vehi...

Design and testing of a 26 kW ammonia arcjet system for the Air Force Laboratory's Electric (Propulsion) Space EXperiment (ESEX) demonstration mission are described in this paper. The design philosophy of the arcjet thruster and the ammonia propellant feed subsystem is presented. A third system element, the Power Conditioning Unit (PCU), is also di...

Pulsed Plasma Thrusters (PPTs) are finding renewed user appeal due to the growth in small satellite applications. PPTs are especially well suited to small satellite applications because they are simple, low-mass, and high Isp propulsion systems. The solid Teflon fuel allows for a self-contained, inert and stable propellant system. With a power draw...