No abstract

No abstract

A system trade study was conducted to determine the feasibility of a 2007 Mars sample return (MSR) mission utilizing the Martian atmosphere for in-situ propellant production (ISPP). A hybrid zirconia and SabatierElectrolysis (S E) process ISPP system was assumed that produced liquid oxygen and liquid methane. The emphasis of the study was threefold. First, to determine what impact the choice in mixture ratio of the oxygedmethane propellant combination used for Mars ascent has on the overall injected mass from Earth of the MSR mission elements. Second, to ascertain if the 2003/2005 "workhorse" lander being designed for MSR missions can be modified to accommodate a 2007 ISPP MSR mission. Third, to identify what parameters and technologies have a significant impact on the overall injected mass of the MSR mission elements. This paper also summarizes the current status of ISPP work funded by the NASA through the Jet Propulsion Laboratory (JPL). It was determined that the choice in mixture ratio has a moderate impact on the overall injected mass from Earth of the MSR mission elements. Although it satisfies the injected mass constraint of an affordable medium"? launch vehicle, a 2007 ISPP MSR mission cannot be accomplished using a modified 2003/2005 "workhorse" lander due to configuration and packaging issues. Configuration, propulsion, power, and thermal control appear to be the four areas with the highest impact on the overall feasibility and injected mass for an ISPP MSR mission. Technology investment in these areas is required to make a 2007 ISPP MSR feasible.

A method for determining margins in conceptual-level design via probabilistic methods is described. The goal of this research is to develop a rigorous foundation for determining design margins in complex multidisciplinary systems. As an example application, the investigated method is applied to conceptual-level design of the Mars Exploration Rover (MER) cruise stage thermal control system. The method begins with identifying a set of tradable system-level parameters.Models that determine each of these tradable parameters are then created. The variables of the design are classified and assigned appropriate probability density functions. To characterize the resulting system, a Monte Carlo simulation is used. Probabilistic methods can then be used to represent uncertainties in the relevant models. Lastly, results of this simulation are combined with the risk tolerance of thermal engineers to guide in the determination of margin levels. The method is repeated until the thermal engineers are satisfied with the balance of system-level parameter values. For the thermal control example presented, margins for maximum component temperatures, dry mass, power required, schedule, and cost form the set of tradable system-level parameters. Use of this approach for the example presented yielded significant differences between the calculated design margins and the values assumed in the conceptual design of the MER cruise stage thermal control system.

The creative process of team design can he rapid and powerful when focused, yet complex designs, such as spacecrafi. can slow and quench the essential elements of this process. Concurrent Engineering techniques partially address this problem, but a fuller realization of their benefits require an approach centering on the human aspects of teamwork. ICEMakerTM is a Microsofi Excel@ based software tool that facilitates closer-to-ideal collaboration within teams employing the new Integrated Concurrent Engineering (ICE) methodology. ICE is a generic approach that emphasizes focused collaborative design in a singleroom context. and is now employed at several aerospace organizations to increase the productivity of design teams defining complex early development-phase products. By way of introduction, this paper describes the basic elements of ICE needed to understand ICEMaker and its application. We present the design approach, philosophy, and clientserver architecture of the ICEMaker system, as well as a simplified user scenario.NASA's Jet Propulsion Laboratory (JPL) has recently adopted ICEMaker for its primary early-phase space mission and system advanced project design team, Team-X. We describe Team-X's experience with ICEMaker and report on the lessons learned, and qualitative product improvements, resulting fiom JPL's implementation of ICEMaker.