Critical Information for Decision Making

In determining what information and data is most crucial to the decisions involved in defining, and designing, and providing a market driven HRST system for the future we need to first identify that market, the customers, and clearly understand what they want in, and demand of, a space transportation system. However, in addition to the "customers" who will eventually pay for the services of a space transportation system, there are several other organizations / individuals who will be major players or "stakeholders" who must be fully considered and satisfied if a proposed space transportation system enterprise is to be successfully marketed and profitably operated. Including the paying customers, the stakeholders are:

1. The financial investor who will provide the capital for the development, acquisition and initial operation of the transportation system. He will demand a reasonable return on investment. It is possible that the investment may be divided into these two parts:

• Capital for the design, development, and marketing of the transportation vehicles to be utilized in the operation of a space transportation system, for example a "United Spacelines".
• Capital for the operator to acquire vehicles, facilities, and support infrastructure to start operations of a "United Spacelines."

2. The User or Payload Customer who will pay the operator for the transportation services of cargo and personnel in space.
3. The Developer and Producer of the space transportation vehicle which will be procured and utilized in the operation of a space transportation system. This includes the critical selection of the vehicle concepts which best satisfies all of the transportation system desired attributes and the design, development, certification, and production of the vehicle.
4. The Transportation System Operator of a "United Spacelines" who will acquire, establish and operate the transportation system as a profitable, business enterprise., for example a "United Spacelines". This transportation system operator is a customer of the vehicle developer and producer.
5. The federal, state and local governments representing the general public, each who play several important roles which must be addressed by both the system developer and operator., such as assuring public safety or addressing overflight issues.

• The role to be played by the federal government is still evolving; but it is expected to be patterned after the role the federal government has developed with the airline transportation industry. The major elements are:

• National policies to foster affordable, safe, reliable space transportation.
• Provide development and demonstration of advanced technologies.
• Assure public safety which is manifested in "spaceport" certification, launch permits, reentry control, and eventually space vehicle certification.
• Negotiate, ratify, and enforce international agreements and treaties of space transportation operations.
• Environmental control - ground, air and space.

• The state governments are interested in the potential economic benefits, development of new jobs, and the safety and environmental consequences of spaceport operations in their or neighboring states. They may be financial and political supporters or adversaries, and may be involved in support infrastructure, financing and development as needed.
• The role of local governments, again using the model of airline transportation systems is expected to have the following elements:

• Investment and operations for fees of a spaceport similar to the relationship of a municipal airport and airlines.
• Tax structure and incentives.
• Support infrastructure financing and development of roadways, power supply, communications, etc.
• Motivated by economic growth.
• Constrained by environmental and safety concerns. The general public, taxpayers, will be concerned with many of the issues and decisions involved in establishing and operating a spaceport and need to be brought into the decision process as early as possible.

The purpose of outlining the major organizations and the role they will play in establishing and operating an HRST system of the future is to help the reader understand how and why this design guide was developed and how it may be helpful to designers and decision makers.

In developing this "Guide for the Design of HRST Systems" the "paying customer" and each of the other four stakeholders needs and demands were considered as requirements to be satisfied in the best manner possible. Particularly, the Commercial Space Transportation Study⁸ has recently examined potential markets and associated needs to spur these markets. In the process used to accomplish this, the SPST divided the overall requirements into three The first step in this process was the identification of the customers requirements and priority needs. These were divided into three categories:

• Functional performance of the transportation system such as capability in terms of payload or destination.
• Desired attributes of the transportation system (essentially demands of the customers) such as safety, affordability, dependability, or flexibility.
• Programmatic constraints of the transportation system such as cost, schedule, or risks associated with the design, development and implementation of the system including infrastructure.

The following chart focused on affordability shows the relationship of these categories and places them in two groups. The one group (desired attributes & functional performance) is described here as recurring cost or operational effectiveness and the other group (programmatic constraints) is described as non-recurring cost or programmatics. This group is further broken down into program acquisition (commitment) and technology R&D (long lead investment). The technology cycle is required when the technology readiness and risk from performance and operability goals compliance are not satisfied. Therefore, the key to achieving the objective of space transportation systems affordability is brought about when and only when the program acquisition criteria are properly met (technology margins, options, readiness, and full compliance of performance and operability goals can be achieved).

[Figure not included here]

FUNCTIONAL PERFORMANCE

The functional performance requirements used in the QFD process were basically those defined in the HRST project guidelines. The performance requirement was to deliver 30,000 lbs +/- 10,000 lbs to a 100 nm, 28.5 degree inclination orbit. A candidate transportation system (HRST) must provide credible evidence, system design and performance data to prove that it can satisfy the functional requirements.

In order to make a reasonable assessment of the potential of a candidate transportation system meeting the functional performance requirements there is a critical level of conceptual design data and performance flyout trajectory data that must be available. Since the concepts currently being considered for HRST include several variations and combinations of air breathing and rocket propulsion systems the design and performance analysis data must include critical parameters appropriate to these concepts. This data should include key aerodynamic characteristics of the vehicle such as the lift and drag coefficients as a function of altitude and Mach number, engine maps giving thrust and propellant flow rate as a function of altitude, Mach number and equivalence ratio, detailed breakout of component weights and a description of the force accounting system. The underlying data base for the engine maps should also be included in the data. This would include inlet compression efficiency, inlet air capture ratio, mixing combustion and exhaust nozzle efficiencies where applicable.

The section in this guide "Verifying Functional Requirements - Performance" further expands on information relevant to the performance aspects of an HRST, such as an air breather. For purposes of this guide and the initial work of the SPST, it should be noted, however, that the focus has been principally on the desired attributes and programmatic constraints of future concepts.

DESIRED ATTRIBUTES

In addition to meeting functional or performance requirements a candidate space transportation system must be evaluated in accordance with the degree to which it provides the attributes or features most desired by customers. These were identified by the QFD process as follows:

These transportation system attributes were prioritized according to a combination of the importance to the customer, where we are today in space transportation, and how much we need to improve. Note that the lower level does not mean less important. Rather, it indicates that in view of current transportation system characteristics the need for improvement there is not as great.

Figure A. Attributes of a Reusable Space Transportation System

However, it is very difficult for a transportation system decision maker or designer to respond to desired attributes, such as highly reliable, flexible or maintainable. Therefore, the next step in the process used to develop this guide was to identify measurable criteria that correlate with, such as have a positive impact on, the desired system attributes. There were many measurable criteria (64) identified. To aid the system definition and design decision process they have been prioritized in accordance with the degree of impact they have on the desired attributes. These are shown in Figures 1, 2 and 3. Each of these measurable criteria is addressed individually in this guide. Each of the highest criteria is a design feature that significantly impacts many of the desired attributes, particularly affordability, safety, dependability and operability.

In other words, the incorporation of design features, particularly those in the top 20 will have a positive impact on many of the attributes that the customer desires in a space transportation system. This relation of the design criteria and the desired system attributes and sub-attributes is shown on the following page.

[Figure not included here]

Each of the systems major attributes and sub-attributes on the left have been connected to a box or boxes containing those design features which if incorporated in the system design would have a positive, beneficial impact on the desired attributes.

It may be noted here that the design criteria are divided into two groups. In the first group the desired direction is to minimize (minimum number). For example a minimum "number of potential leakage / connection sources" will have a significant positive impact on several of the desired system attributes. In the second group the direction is to maximize (maximum number). For example a maximum "number of components with demonstrated high reliability" in an HRST system will have a major impact on affordability (operations and support) and dependability (intact vehicle recovery, mission success and launch on time).

The highest priority (top 20) criteria, if manifest in a design with the desirable directions of improvement, will obviously have the greatest positive influence on the desired attributes. Therefore, information and data on these top 20 criteria are most critical in any decision making process that will define the most marketable transportation systems and choose among alternative design concepts.

Unfortunately, in the initial phases of the decision making process regarding future, next generation transportation systems, only top level information or data is traditionally available. In exercising the QFD process using the measurable criteria (Figures 1, 2 and 3) it was found that information on many of the top 20 criteria was not available even from transportation system studies that had been completed. In other words a different type of system information was required by a large number of measurable criteria. Referring to the description of levels shown below many of the criteria required data at Level 2 and some at Level 3.

Level 1 - Transportation System Concept Definition. This includes a sketch of the system and a functional description, performance analysis, preliminary mission trajectory and weight estimates.

Level 2 - Transportation System and Subsystem Description. This includes sub-systems configuration and functional descriptions including weight estimates. This includes propulsion, avionics, thermal protection and power generation definition.

Level 3 - System Preliminary Design Review. Information and data normally included in a PDR.

To correct this situation some level 2 subsystem description and data must be developed in the initial phases of advanced system studies. This is necessary in order to provide the critical information required by the top 20 criteria. This requirement needs to be communicated to the technical community involved in advanced transportation system studies and analysis.

Again, to assess future operational scenarios it is necessary to answer questions for which information is not often traditionally available before decision making processes such as funding distribution. "How often will it fly and for how much and why?" is a question the answer to which begins by addressing the criteria in this guide. This is not entirely a novel conclusion:

Only the direct hardware driven costs, about 32 percent of the Space Shuttle Program Budget, were addressed by the study. Current operations cost accounting methods were found to be inadequate for accurately determining the savings from subsystem improvements. The NASCOM was not designed for estimating modifications to existing systems and there are only limited tools available for estimating space flight operations costs.

From the NASA Access to Space Study, Summary Report¹⁴

OSSD, NASA HQ, January 1994

PROGRAMMATIC CONSTRAINTS

The identification of the transportation system design features that will benefit (have a positive impact on) the desired system attributes was addressed in the previous section. The other dimension that must be addressed in any decision making process involved in the definition and design of an advanced space transportation system is the programmatic constraints. These are factors such as schedule, cost, risks and investor incentive in a given market environment. Again, in the QFD process that has supported this guide, measurable criteria were developed and prioritized. These are shown in Figure 4. Adequate information on these program criteria is as critical to strategy as the design features based on desired system attributes.

Our ability to acquire the critical information and data on schedule, costs, technical risks and so forth met with many of the same problems as were addressed in the previous section on desired system attributes. The necessary data is not readily available in the initial phases of transportation system studies and conceptual designs. It will be necessary to proceed to Level 2 in some cases to obtain it. For example, the number of technology breakthroughs required for successful development of a particular concept may require definition of major sub-systems.

It should be noted that in contrast to the stability of the desired attributes and the related design features in this guide that the program constraints may be expected to vary far more over shorter periods of time for several reasons. Global or national economic change, international competition and political scenarios may all significantly impact program considerations. This further emphasizes the need and value in defining the desired attributes and related measurable criteria or design features since they are the foundation of a technical strategy that can be expected to focus improvement efforts for the long term.

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Edgar Zapata, NASA Kennedy Space Center

Shuttle Process Engineering Directorate, Fluid Systems Division