Over the past two decades, risk management and risk analysis have emerged throughout the business community in the United States (US) as prominent planning and development strategies used to mitigate risk of failure and ensure a high return on investment (ROI) for business endeavors (financial and otherwise). They are generic tools that can be applied to any business regardless of the sector (i.e., government, university, private) and have been used by the Federal government in the form of institutional practices aimed at maximizing the probability of success in business activities. One US Federal agency that incorporates risk management and analysis techniques into business and/or engineering activities is the National Aeronautics and Space Administration (NASA). The present work is a discussion on mission, spacecraft and instrument design (as well as technology development) and the role of risk management, analysis and mitigation as a fundamental tool in the design process

Dash, Paul H.

Silk, Eric A.

NASA Technical Reports Server

Silk and Dash, August 27,2007 
RISK MANAGEMENT: A PRACTICAL DESIGN TOOL FOR SPACE 
SYSTEMS AND TECHNOLOGY DEVELOPMENT 
ERIC A. SILK+ 
Thermal Engineering Technology Development Group, NASA Goddard Space Flight Center, 
Greenbelt, MD 2077 1 
PAUL H. DASH$ 
Economic & Business Analysis Group, Booz Allen Hamilton, 
5220 Pacific Concourse Drive, Los Angeles, CA 90045 
1 ABSTRACT 
Over the past two decades, risk management and risk analysis have emerged throughout the business 
community in the United States (US) as prominent planning and development strategies used to mitigate 
risk of failure and ensure a h ~ g h  return on investment (ROI) for business endeavors (financial and 
otherwise). They are generic tools that can be applied to any business regardless of the sector (i.e., 
government, university, private) and have been used by the Federal government in the form of institutional 
practices aimed at maximizing the probability of success in business activities. One US Federal agency that 
incorporates risk management and analysis techniques into business andlor engineering activities is the 
National Aeronautics and Space Administration (NASA). The present work is a discussion on mission, 
spacecraft and instrument design (as well as technology development) and the role of risk management, 
analysis and mitigation as a fundamental tool in the design process. 
2 INTRODUCTION AND BACKGROUND 
The primary objective of every spacecraft program at NASA is mission success. Mission success is 
measured relative to the mission's technical goals as dictated by the principal investigator. Techniques to 
ensure mission success (i.e., mission assurance) are used in spacecraft development at each assembly level 
(i.e., spacecraft, instrument, subsystem, and component). Engineering design on each of these levels is 
subject to four criteria: technical performance, size, cost and risk of failure [I]. Each of these criteria are 
applied to spacecraft design from concept to flight and are often used to tailor engineering decision making 
that eventually leads to a flight ready product. While these criteria are presented as individual design 
Submitted to AIAA Journal of Spacecraft and Rockets Submitted for review on September ?, 2007 
t Corresponding Author 
5 Senior Business Consultant 
Email address: Eric.A.Silk@nasa.gov 
https://ntrs.nasa.gov/search.jsp?R=20080045468 2019-08-30T20:47:50+00:00Z
parameters, close examination of the design process shows that they are not mutually exclusive, but 
intricately coupled. 
Techca l  performance may be assessed in terms that are easily quantifiable, however, the criteria of 
size and cost are slightly more pervasive. In spacecraft design, volume and mass are used to quantify the 
metric of size. Spacecraft andlor instruments that have a large volume require a larger payload and launch 
vehicle. A larger launch vehicle also requires more fuel in order to ensure transit to deployment altitude 
outside the earth's atmosphere. In addition, more mass also implies an increase in fuel is needed at launch 
to provide thrust levels commensurate with the launch vehicle's total mass. An increase in the projected 
fuel consumption for the launch vehicle implies an increase in comprehensive program costs. Thus, from a 
program perspective, cost corresponds directly with size. Since cost projections for proposed missions are a 
continually increasing concern in the context of the US national budget, mission success may be considered 
a function of two criteria: technical achievement of mission goals and cost effectiveness associated with the 
attainment of these goals. Cost effective designs for spacecraft systems must aim to meet technical 
performance requirements while designing size and mass efficient spacecraft that meet the mission mass 
budget and launch vehicle size constraints. Risk management and analysis have become usehl tools in 
meeting this challenge. 
3 RISK MANAGEMENT AND SPACECRAFT DESIGN 
The topic of risk analysis often takes the form of reliability analysis in engineering applications. 
However, for the present discussion, the general term of risk analysis shall be used henceforth. Risk may be 
considered the possibility of exposure to an adverse consequence given certain actions. In regards to space 
flight applications this could be a safety accident, a budget overrun, a slip in schedule, or failure to acheve 
mission success due to selection of a particular design for use [2,3]. Risk analysis pertains to the 
quantification of uncertainty associated with certain adverse events (i.e., the chances of an undesirable 
event occurring) [2]. Risk management deals with decision making under conditions of uncertainty while 
using quantified measures of uncertainty in the decision making process [2,3]. Inherent to risk management 
theory is the definition of utility. Under conditions of uncertainty, the utility of a particular decision may be 
defined as the consequence of each possible outcome associated with the decision. The goal of risk 
management is to investigate the trades between different conveniences and consequences (i.e., utilities) for 
each possible outcome given a situation involving uncertainty [2]. 
Risk management, as applied to spacecraft design, investigates the utilities associated with specific 
mission and system designs on all levels. This includes identification, analysis, planning, tracking, 
controlling and documenting (as well as communicating) risks and the corrective measures developed to 
address them 131. The three primary tools used in the implementation of risk management are Failure 
Modes Effects Analysis (FMEA), Fault Tree Analysis (FTA), and risk mitigation. FMEA is used to identify 
mission failure modes and associated utilities for each system design element. FMEA is also used to 
categorize failure modes according to severity. FTA is instituted to specify credible ways that an undesired 
event can occur [3]. Upon determination of mission endangering utilities pertaining to desired design 
options, risk mitigation techniques are applied to the design to increase the probability of mission success 
(i.e., decrease the risk associated with the design selection process andlor the design leading to the actual 
mission). Application of methodologies that mitigate risk of failure have a direct effect upon mission costs. 
Mitigation techniques are often incorporated into spacecraft design and assembly through the use of 
spaceflight hardware and procedures from legacy space flight programs, redundancy of mission critical 
components as well as technology and manufacturing validation of system components. Successful flight 
legacy programs with an established performance record serve as a basis for expected performance on 
future missions that use similar flight system components. Integration and test procedures borrowed from 
such programs aid in the reduction of human error (and associated impacts) during integration at each of 
the assembly levels. T h s  further reduces the probability of increasing program costs through new and 
extensive engineering efforts to ensure in-flight performance of components. System and component level 
redundancy also is a technique that has been used to mitigate mission risk. Redundancy of critical system 
components (e.g., lasers, sensors, detectors, thermal control hardware, etc.) increases the probability of 
mission success if failure of a primary component were to occur. However, system redundancy often leads 
to hgher program costs. As such, many modem spacecraft programs either opt for selective redundancy 
(i.e., redundancy applied to a few critical items) or a single string approach (i.e., no system redundancy 
designed into system critical space flight components). A primary factor in the determination of risk of 
failure associated with a spacecraft assembly is the risk of failed performance associated with the individual 
components comprised in the assembly. Full technology validation of component level items is critical to 
mission success and aids in the mitigation of risk at each of the spacecraft and instrument assembly levels. 
Furthermore, it decreases the need for additional validation efforts during assembly phases that may also 
require additional funding. Nonetheless, component level validation is best addressed in the technology 
development stage of the space flight hardware in question. 
4 TECHNOLOGY DEVELOPMENT 
As one of the vanguards of human science and technology, NASA is always eager to promote new 
concepts and ideas that have the potential to grow and aid in future flight programs through mission 
enabling technologies. The approach used by NASA to establish new technologies while also mitigating in- 
flight risk of failure is to subject the component in question to a regiment of tests designed to validate 
successful in-flight performance and decrease the probability of failure. This goal is acheved through a 
technology development and maturation plan designed around the technology rating level (TRL) system 
and lifetime testing. The TRL system (shown in Table 1) has rankings from one to nine and is aimed at 
developing technologies from the breadboard phase up through flight readiness. Upon achieving TRL 8, 
technologies are acknowledged as being viable for use on actual performance based missions. TRL 9 is 
validation of successful flight performance on an actual mission. The TRL system is applied to all 
technologies actively developed through NASA's technology development programs: Small Business 
Innovative Research (SBIR), Small Business Technology Transfer (STTR), Internal Research and 
Development (IRAD), and New Millennium programs. 
Each of the development levels in the TRL system is assigned a relevant environment for testing. 
These environments are based on ground (TRLs 1-6), micro-gravity (TRLs 7-9), and space (TRLs 7-9) 
platforms. Ground based testing may consist of testing in a thermal vacuum chamber to simulate pressure 
and temperature conditions in space. Such facilities are easily accessible in the government and private 
sector. However, from both a technical and logistics standpoint, the more challenging of these 
environments to simulate and test in is micro-gravity. Test apparatus that simulate the effects of micro- 
gravity are not limited to space based platforms. NASA's drop towers (located at NASA Glenn Research 
Center) and reduced gravity aircraft have been used in technology development efforts to characterize 
component performance in micro-gravity. The NASA Glenn drop towers can provide a maximum of 3.3 
seconds of micro-gravity whereas the parabolic flight profiles associated with reduced gravity aircraft 
testing provide approximately 22 seconds of micro-gravity during a single flight parabola. Under these 
approaches, the time constant associated with micro-gravity conditions is significantly shorter than the 
amount of time required to reach system equilibrium for many experiments. Thus, other methodologies are 
required for sustained micro-gravity testing. In previous years, the Space Shuttles' payload bays have been 
used to provide a sustained micro-gravity test platform for emerging space technologies (i.e., the Hitchhiker 
and Get Away Special (GAS) programs which are currently non-active). However, the emergence of the 
International Space Station (ISS) and delivery of components to it via the Space Shuttles significantly 
reduced the availability of Shuttle payload bay space for technology development efforts, hence reducing 
the number of technologies satisfying mid-level TRL requirements. In addition, the Space Shuttle 
Columbia disaster further limited payload bay access for technology development programs. Today, 
microgravity requirements are satisfied for growing technologies through space flight on missions 
specifically designed and created for technology validation such as the New Millennium program and the 
Department of Defense's Tactical Microsatellite Experiment (TacSat) missions. Nonetheless, such missions 
have limited availability of space and relatively high mission costs, thereby limiting the number of 
technologies validated through these missions. 
An additional technique used to mitigate risk that may be considered complementary to the TRL 
system is lifetime testing. Lifetime testing is not explicitly addressed in the TRL system, however, it is 
highly pertinent to space flight programs seeking to mitigate risk (especially those that are not particularly 
sensitive to gravitational effects). The primary objective of the TRL system is to validate new technologies 
as flight proven in a relevant mission environment. The primary objective of lifetime testing is to 
demonstrate component andlor system performance as well as the determination of possible performance 
degradation to components that are subjected to extensive use. Thls applies to subsystems (i.e., electrical, 
mechanical and thermal) on all assembly levels. The afore-mentioned technical goals used to gauge mission 
success are based on temporal specifications. The temporal metric for mission success is the expected 
mission lifetime. Longer missions (2 5 years) entail more durable components which increases costs 
through material selection and engineering design time. Thus, mission lifetime is a driver for system design 
as well as the selection of components and machinery for use on space flight missions. The amount of risk 
associated with the use of a component often incorporates continuous lifetime performance (either through 
ground based lifetime testing or legacy flight systems) relative to the desired mission life. Furthermore, 
achievement of TRL 9 does not negate or diminish the importance of lifetime testing and performance. The 
larger the amount of time a component or system has operated within desired performance specifications on 
orbit, the more reliable it is considered. 
6 CONCLUSIONS 
For several years, NASA has been instrumental in the creation and validation of new technologies that 
later matriculated to the civilian sector and revolutionized the American way of life. The basis for the 
successful development of these technologies are risk management (based on quantified measures of 
uncertainty), risk analysis and mitigation techniques that are rooted in the institutional practices of NASA. 
The risk mitigation practices and procedures detailed in this work are examples of common risk prevention 
techniques borrowed from the private sector, as well as institutional practices created and refined in-house 
through years of successful engineering efforts. Today these practices are part of NASA culture. As 
technical complexity for mission programs and Federal budget constraints increase, risk management, 
analysis, and mitigation techniques that complement the engineering process are expected to become more 
important and refined in aiding the success of NASA's future flight missions. 
DISCLAIMER 
The ideas and opinions expressed in this document are solely those of the authors' and do not represent 
official NASA policy. 
ACKNOWLEDGEMENTS 
Eric Silk was supported by the Thermal Engineering Branch and the Technology Transfer office at the 
NASA Goddard Space Flight Center. Paul Dash was supported by the Economic & Business Analysis 
group of Booz Allen Hamilton in Los Angeles, CA. Special thanks also to Dan Butler of NASA Goddard 
Space Flight Center's Thermal Engineering Branch for his insights. 
REFERENCES 
[I] Silk, E.A., and Creel, R., 2007, "Technology Development for Lunar Thermal Applications and the 
Next Generation of Space Exploration," Journal ofAerospace Engineering, Vol. 221, No. 2, pp. 305-309 
[2] Singpurwalla, N.D., 2006, "Reliability and Risk: A Bayesian Perspective," John Wiley & Sons, Ltd., 
Washington, D.C. 
[3] NASA Goddard Space Flight Center Office of Mission Success/Code 170, 2005, "Goddard Procedural 
Requirements: Directive No. GPR7 120.4A," Goddard Space Flight Center, Greenbelt, MD 
List of Tables 
Table 1. 
Level p Definition Validation Environment Basic principles observed and reported. I Ground based laboratory 1 
function andor characteristic proof-of 
conceDt. 
Technology concept andor application 
formulated. 
Analytical and experimental critical 
Ground based laboratory 
Ground based laboratory 
System prototype demonstration in an 
operational environment. 
Actual system completed and "flight 
qualified" through test and 
Component andlor breadboard 
validation in laboratory environment. 
Component and/or breadboard 
validation in a relevant environment. 
Systemisubsystem model or prototype 
demonstration in a relevant environment 
(ground or space). 
demonstration (ground or space). 
Actual system "flight proven" through 
Ground based laboratory 
i) Microgravity platform (airborne or 
ground). 
ii) Vacuum environment ( ~1 oW6 Torr) 
i) Microgravity platform (airborne or 
ground). 
ii) Vacuum environment ( Tom) 
successful mission o~erations. 
1 i) Microgravity platform (space) I 
i) Microgravity platform (airborne or 
i) Microgravity platform (space) 
I 
Table 1. Technology Readiness Level Definitions 


Risk Management: A Practical Design Tool For Space Systems and Technology Development

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server