Douglas O. Stanley

Design options for advanced manned launch systems

Various concepts for advanced manned launch systems (AMLS) are examined for delivery missions to Space Station and polar orbit. Included are single- and two-stage winged systems with rocket and/or airbreathing propulsion systems. For near-term technologies, two-stage, reusable rocket systems are favored over single-stage rocket or two-stage airbreathing/rocket systems. Advanced technologies enable viable single-stage-to-orbit (SSTO) concepts. Although two-stage rocket systems continue to be lighter in dry weight than SSTOs, advantages in simpler operations may make SSTOs more cost effective over the life cycle. Generally, rocket systems maintain a dry weight advantage over airbreathing systems at the advanced technology levels, but to a lesser degree than when near-term technologies are used. More detailed understanding of vehicle systems and associated ground and flight operations requirements and procedures is essential in determining quantitative discrimination between these latter concepts.

Dual-Fuel Propulsion in Single-Stage Advanced Manned Launch System Vehicle

As part of the United States Advanced Manned Launch System study to determine a follow-on, or complement, to the Space Shuttle, a reusable single-stage-to-orbit concept utilizing dual-fuel rocket propulsion has been examined. Several dual-fuel propulsion concepts were investigated. These include: a separate-engine concept combining Russian RD-170 kerosene-fueled engines with space shuttle main engine-derivative engines: the kerosene- and hydrogen-fueled Russian RD-701 engine; and a dual-fuel, dual-expander engine. Analysis to determine vehicle weight and size characteristics was performed using conceptual-level design techniques. A response-surface methodology for multidisciplinary design was utilized to optimize the dual-fuel vehicles with respect to several important propulsion-system and vehicle design parameters, in order to achieve minimum empty weight. The tools and methods employed in the analysis process are also summarized. In comparison with a reference hydrogen- fueled single-stage vehicle, results showed that the dual-fuel vehicles were from 10 to 30% lower in empty weight for the same payload capability, with the dual-expander engine types showing the greatest potential.

Propulsion system design optimization using the Taguchi method

The authors discuss the Taguchi method as an approach to design optimization for quality. The method is briefly explained, and its application is illustrated for a propulsion system design optimization study for an advanced space transportation vehicle. The results suggest that the Taguchi method is a systematic and efficient approach that can aid in designing for performance, quality, and cost. Principal benefits include significant time and resource savings and the determination of parametric sensitivities and interactions. >

Utilizing air-turborocket and rocket propulsion for a single-stage-to-orbit vehicle

With appropriate technology advances, a horizontal-takeoff single-stage-to-orbit (SSTO) launch vehicle could be designed which utilizes a combination of air-turborocket (ATR) and rocket propulsion systems. Such a vehicle is currently under study at Langley, and this paper presents the results of that study. Estimated vehicle weight characteristics, engine characteristics, geometry, aerodynamics, performance, structures, and subsystems are summarized. Trade studies performed on the reference vehicle to optimize the initial thrust-to-weight ratio (T/W) and the T/W after transition to the rocket phase with respect to vehicle weights are also presented. Throughout the vehicle presentation, special attention is given to the design issues, sensitivities, and performance parameters involved.

Conceptual design of a fully reusable manned launch system

The conceptual design of a rocket-powered, two-stage fully reusable launch vehicle has been performed as a part of the advanced manned launch system (AMLS) study by NASA. The main goals of the AMLS study are to provide routine, low-cost manned access to space. Technologies and system approaches have been studied that would contribute to significant reductions in operating time and manpower relative to current systems. System and operational characteristics of the two-stage fully reusable vehicle are presented, and the various tools and methods used in the design process are summarized. The results of a series of trade studies performed to examine the effect of varying major vehicle parameters on the reference two-stage fully reusable vehicle are also summarized.

Application of Taguchi methods to dual mixture ratio propulsion system optimization for SSTO vehicles

The application of advanced technologies to future launch vehicle designs would allow the introduction of a rocket-powered, single-stage-to-orbit (SSTO) launch system early in the next century. For a selected SSTO concept, a dual mixture ratio, staged combustion cycle engine that employs a number of innovative technologies was selected as the baseline propulsion system. A series of parametric trade studies are presented to optimize both a dual mixture ratio engine and a single mixture ratio engine of similar design and technology level. The effect of varying lift-off thrust-to-weight ratio, engine mode transition Mach number, mixture ratios, area ratios, and chamber pressure values on overall vehicle weight is examined. The sensitivity of the advanced SSTO vehicle to variations in each of these parameters is presented, taking into account the interaction of each of the parameters with each other. This parametric optimization and sensitivity study employs a Taguchi design method. The Taguchi method is an efficient approach for determining near-optimum design parameters using orthogonal matrices from design of experiments (DOE) theory. Using orthogonal matrices significantly reduces the number of experimental configurations to be studied. The effectiveness and limitations of the Taguchi method for propulsion/vehicle optimization studies as compared to traditional single-variable parametric trade studies is also discussed.

Application of Taguchi methods to propulsion system optimization for SSTO vehicles

The application of advanced technologies to future launch vehicle designs would allow the introduction of a rocket-powered, single-stage-to-orbit (SSTO) launch system early in the next century* For a selected SSTO concept, a dual mixture ratio, staged combustion cycle engine was selected as the baseline propulsion system. A series of parametric trade studies are presented to optimize both a dual mixture ratio engine and a single mixture ratio engine of similar design and technology level. The effect of varying lift-off thrust-to-weight ratio, engine mode transition Mach number, mixture ratios, area ratios, and chamber pressure values on overall vehicle weight is examined. The sensitivity of the advanced SSTO vehicle to variations in each of these parameters is presented, taking into account the interaction of each of the parameters with each other. This parametric optimization and sensitivity study employs a Taguchi design method. The Taguchi method is an efficient approach for determining near optimum design parameters using orthogonal matrices from design of experiments (DOE) theory. Using orthogonal matrices significantly reduces the number of experimental configurations to be studied. The effectiveness and limitations of the Taguchi method are also discussed.

Single-stage-to-orbit — A step closer

Abstract Over the past several years there has been a significant effort within the United States to assess options to replace the Space Shuttle some time after the turn of the century. In order to provide a range of technology options, a wide variety of vehicle types and propulsion systems have been examined. These vehicle concepts which are representative of the classes of concepts mat could be proposed for any future vehicle development is being used in the initial phase of the access to space activity to identify requirements for the technology maturation effort and to assess approaches to achieve the required low operations cost. This paper provides the results of recent systems analyses and describes the ongoing technology maturation and demonstration program supporting the Reusable Launch Vehicle Program.

Design for Quality Using Response Surface Methods: An Alternative to Taguchi's Parameter Design Approach

ABSTRACTThis article presents the response surface methodology as an alternative approach to Taguchis parameter design methods for optimizing designs for quality. The method is briefly explained, and its application is illustrated by an example of a preliminary design study of an advanced space transportation vehicle. The results indicate that the response surface methodology is a systematic and efficient approach that can help engineering managers design for quality, performance, and cost.

Propulsion requirements for reusable single-stage-to-orbit rocket vehicles

The conceptual design of a single-stage-to-orbit (SSTO) vehicle using a wide variety of evolutionary technologies has recently been completed as a part of NASAs Advanced Manned Launch System (AMLS) study. The employment of new propulsion system technologies is critical to the design of a reasonably sized, operationally efficient SSTO vehicle. This paper presents the propulsion system requirements identified for this near-term AMLS SSTO vehicle. Sensitivities of the vehicle to changes in specific impulse and sea-level thrust-to-weight ratio are examined. The results of a variety of vehicle/propulsion system trades performed on the near-term AMLS SSTO vehicle are also presented.