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Top-Down Manpower Estimating Based on Historical Program Experience
Alan W. Wilhite*
Georgia Institute of Technology, 270 Ferst Drive, Atlanta, GA 30332-0150
and
David Pine† Consultant, 101 Tries Tr., Yorktown, VA 23693
and
Vince J. Bilardo, Jr.‡ NASA Langley Research Center, MS 353X, Hampton, VA 23681-2199
Historical data of the National Aeronautics and Space Administration (NASA) programs and projects were retrieved from the NASA Marshall Redstar database, the program review files from the Independent Program Assessment Office at NASA Langley, and from program performance database at NASA Headquarters Comptroller Office. The data collected were organized by program/project dates from inception to completion and yearly funding and NASA workforce (manpower) usage. The programs and projects were categorized by manned versus unmanned, and in-house (most work completed by NASA) versus out of house. The data for program duration ranged from 2.5 to 12 years with a mean of 5.3 and 9.1 years for manned and unmanned programs respectively. Program costs ranged from $48M to $87B using inflation to scale to 2004 dollars, and NASA civil servant manpower average per year over the program/project ranged from 6 to 3,132 man-years. Statistical analyses were conducted to correlate workforce, cost, and duration.
Nomenclature a = regression constant (the intercept on the log-log-scale) ATP = Authority to Proceed b = the regression coefficient (the slope on the log-log scale) CDR = Critical Design Review CSM = Command and Service Module FF = First Flight FTE = Full Time Equivalent, total hours worked/work-hours per year per person JPL = Jet Propulsion Lab LM = Lunar Module NASA = National Aeronautics and Space Administration PDR = Preliminary Design Review UPN = Unique Project Number X = the cost parameter Y = workforce level
* Langley Distinguished Professor, School of Aerospace Engineering, Associate Fellow AIAA † Consultant, Member AIAA. ‡ Project Manager, Exploration Systems and Space Operations Technology, Senior Member AIAA.
1st Space Exploration Conference: Continuing the Voyage of Discovery30 January - 1 February 2005, Orlando, Florida
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I. Introduction
ITH the National Aeronautics and Space Administration’s (NASA) recent introduction of “Full-Cost Accounting” practices into its project formulation and implementation processes, reliable estimates of the
scope and cost of the Civil Service component for each mission is now essential. This knowledge is needed for three reasons; 1) project workforce requirements must be laid against all Center requirements to determine availability of personnel, and 2) the full cost of these personnel are now included as a project cost, and thus must be known in advance for budget planning, and 3) project schedules need to be assessed to assure “reasonableness” when compared against NASA history. Of course, skill mix analysis is also needed to assure that the proper skills are available. This model addresses personnel quantity and their cost, but not skills availability. Prior to the introduction of full-cost accounting, the cost of civil servants were not included in project budgets. This “free” labor distorted the cost histories of many projects, especially projects with significant spacecraft or instrument in-house civil servant builds. Now these costs are to be included as part of a project’s budget. Workforce allocations and their cost are analyzed to generate traceable estimates for predicting civil service requirements and their cost to the project needed to successfully achieve project objectives. The model is intended to be an aid to project managers in ascertaining valid projections of required workforce, by mission phase, and by the total cost of the project. The database includes both in-house data where the project workforce is dominated by NASA civil servants for design/build/integration, and out-of-house data where most of the design/build/integration is conducted by contract through private industry. An excellent precursor to this study was conducted by NASA Marshall Space Flight Center – Civil Service Manpower Model.1
Another valuable element of this model is to provide a historical reference of the schedule time needed to accomplish various project development phases as a function of the type of project. Too often NASA projects are initiated with schedules that have little likelihood of satisfactory accomplishment. This causes continual time-consuming and costly rebaselinings. Unattainable initial schedules are a major cause of budget overruns and schedule slippage. Prior studies by NASA indicate that on average a project takes 42% longer than was originally planned at the start of the project.2
II. Manpower and Schedule Data The model’s missions are stratified into three categories; manned mission (always out of house), unmanned out-of-house missions, and unmanned in-house missions. Generally, data was only available at high levels. While this exercise endeavored to capture development costs and associated workforce, often it was impossible to cull out Phase A/B activities and operations aspects of workforce and budget. The schedule used was through the end of the development phase, however activities performed in Phase B that should be considered development or operations activities occurring within the development phase could not be identified. Also somewhat inconsistent was the relationship between Phase B activities and the actual date of Authority To Proceed (ATP). Budgets did not allocate pre and post-ATP funding within the start year and thus costs were interpolated by months. This model examines workforce headcount and budget levels as a function of schedule intervals -- Authority To Proceed to Preliminary Design Review (PDR), PDR to Critical Design Review (CDR), and CDR to first flight -- provides a time-phased estimate of project requirements. It includes only direct civil service labor, or in the case of Jet Propulsion Laboratory (JPL) in-house missions, the JPL labor. Since a listing of the time span for each of the intervals is collected, the model also produced probability plots of accomplishing an interval’s work within the allotted time. The projects selected as data points in developing this model, stratified by group, are presented in Table I below.
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Table I. Database Missions.
III. Guidelines, Groundrules, and Assumptions Because of the number of different NASA program and project data documents researched in this study and no one consistent format for financial and workforce accounting, the following is a list of guidelines, groundrules, and assumptions used for database development and organization:
A. Cost
• Project cost was taken from the top-level NASA Program Financial Plan as well as other project documentation. Cost were accumulated in real-year dollars and then normalized to FY2004 dollars for each mission.
• In general costs were captured by fiscal year and then interpolated based on the number of month for the event in that time period to get the cost for a partial year’s activity.
• Cost covered the period from ATP through flight of the first article if there was a series of satellites. Whether Phase A or Phase B activities were included depended upon the relation of the ATP to those activities.
• Where operations costs could be determined and separated from development costs, those costs were excluded.
• Annual real-year cost data were inflated to constant year FY 2004 using NASA’s inflation index. Escalation is based on NASA’s Office of the Chief Financial Officer’s New Start Inflation Index dated February 8, 2004.
B. Civil Service Workforce
• Workforce is expressed as Full Time Equivalent (FTE) in work-years of Civil Service and/or JPL
effort.
MANNED MISSIONS UNMANNED OUT-OF-HOUSE UNMANNED IN-HOUSESaturn V NIMBUS-7 Atmospheric Explorer 1/3/5Saturn 1 Advance X-ray Astrophysics Facility Cosmic Background Explorer (CoBE)Apollo CSM/LM Adv. Composition Explorer (ACE) International Sun-Earth Explorer 1/3 (ISEE)Saturn 1B Active Magnetic Particle Tracer Exp. (AMPTE) International Ultraviolet Explorer (IUE)Gemini Landsat-3 Mars Exploration RoversShuttle Orbiter Landsat-4 Mars PathfinderSolid Rocket Boosters Landsat-7 VikingSpace Shuttle Main Engine Earth Radiation Budget Experiment (ERBE) Tropical Rainfall Measure Mission (TRMM)External Tank Solar-Terrestrial Relations (STEREO) Magnetic Field Satellite Observatory (MAGSAT)Total STS Program Hubble Space Telescope (HST)
SOLAR-BGamma-Ray Observatory (GRO)Space IR Telescope Facility (SIRTF)Upper Atmosphere Research Sat. (UARS)Swift Gamma-Ray BurstThermosphere, Ionosphere, Mesosphere
Energetics and Dynamics (TIMED)Tracking and Data Relay Satellites H/I/J High Energy Astronomy Observatory (HEAO)
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• The workforce figures specifically exclude overhead workforce associated with the Multi-Program Support (MPS)/Institutional Management Support (IMS) budget or other center overhead charges as well as any indirect workforce numbers.
• The workforce numbers are carried through first flight. Workforce numbers are interpolated to split annual numbers between partial year events.
• Post-launch, operations, workforce was excluded. Workforce dedicated to operations, incurred during development could not be separately identified.
• Where identifiable, Phase A and Phase B workforce and cost data is excluded. • Apollo Command Service Module and Lunar Module data are combined, as separated data could not
be obtained. • Out-of-house civil service head counts include both project oversight personnel and technical staff
performing contractor-like work.
C. Schedule
• Data was accumulated by fiscal year. The data were then subtotaled for the periods: ATP to PDR, PDR to CDR, and CDR to first flight.
• Because of numerous rebaselinings, it was occasionally difficult to correlate schedule dates against the version of the project under construction. The International Space Station, which was excluded as a data point, is the prime example of evolving project configurations.
• The relationship between the ATP date and the beginning of development activities was frequently dubious. Often there was a lot of development activity occurring during Phase B. For example, the UARS budget doubled during the latter parts of an extended Phase B, as the true cost and time to develop the instrument suite became known. This Phase B work is not captured.
•
IV. Program/Project Database Description
The 37 missions that comprise this database consist of projects from the 1960’s through the 2000’s. The database is stratified by three development methodology categories. There are 18 out-of-house unmanned missions, 10 out-of-house manned missions and 9 in-house NASA/JPL missions. The number of potential data points were limited by the ability to get a complete set of data, schedule, budget and workforce head count for a project. Fifteen other projects were researched but a full data set could not be found. The project considered were:
Skylab Solid Rocket Motor Heat Capacity Mapping Mission Solar Maximum Mission Dynamics Explorer Voyager Adv. Communications Tech. Sat Applications Tech. Satellite-6 Orbiting Solar Observatory-8 Mars Observer Ocean Topographic Explorer Galileo Orbiter Stratospheric Aerosol Gas Experiment Magellan Geostationary Ops. Environmental Satellite
As with the development of any model, the more data points used, the better the predictive results. The manned data, by nature of what occurred when, is quite old. Apollo is a project of the 1960’s and the Shuttle the 1970’s. The International Space Station project had such a high level of rebaselining that it was impossible to get an accurate, consistent track of schedule and workforce. The model, as it applies to manned missions, assumes that the culture and loading of the 1960’s through the early 1980’s is still appropriate for manned missions being considered at this time. The unmanned project list provides a wide cross-section of missions, from very small explorers to major projects such as the Hubble Space Telescope and Viking. The civil service workforce loading is the direct labor charging against that project’s Unique Project Number (UPN), the primary accounting method for tracking budget and workforce. In most out-of-house projects, this is the civil service staff responsible for the oversight of the development effort. However, some projects had instruments or other mission elements provided by the
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Government, and in those cases the oversight and other technical support staff are not separated. All staffing is considered the same, as is any operation system development staff included in the head count numbers. In developing the model one assumes that every project follows a normal development process and that the schedule dates reflect that process. In reality, many projects have protracted Phase A/Phase B activities, which tend to significantly shorten the time from ATP to PDR. Without researching the details surrounding the development of each project, a difficult if not impossible task at this point in time, the story for each can not be used to adjust data, if such a subjective adjustment is warranted and should be done. Thus it is assumed, that every project has similar development difficulty issues which is included into the statistical analyses by using the non-adjusted data. The upper section of Exhibit 2 shows the format for a typical data point, Saturn V, in this case. Head count and budget data were collected by fiscal year. Then in the next column the budget data were inflated to FY 2004. The key schedule milestone points are then determined and the number of months between each key milestone calculated. Of more importance is when in a fiscal year a key milestone occurs. The ratio of months, before and after a key milestone, is used to interpolate cost and head count data for proper allocation among data points. The lower section of Exhibit 2 summarizes and breaks out the head count and cost data by key milestone periods; ATP to PDR, PDR to CDR, and CDR to First Flight. In addition, within the lower section the following data are calculated for plotting and regression analyses.
• Total duration in months • Average workforce for the three periods • Maximum workforce in any single fiscal year • Total development budget in FY 2004 dollars • Maximum budget in any single fiscal year • Average annual budget in each of the three periods of interest
o ATP to PDR o PDR to CDR o CDR to first flight
• Stratification Group o 1a = Out-of-house unmanned o 1b = Out-of-house manned o 2 = In-house
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These data are analyzed and the regression curves result in the Manpower Estimating Relationships (MER) that are tools to be utilized by NASA planning personnel in establishing budgets and ensuring personnel availability. Curves are developed for the full data set as well as each of the three stratified groups.
V. Data Analysis The methodology used to created the model was to start with the three stratified group of data and then the three time periods, ATP to PDR, PDR to CDR, and CDR to First Flight, for each of the group. Then for each of the groups and each of the time periods a least-squares regression analysis of budget vs. head count was performed and a simple power series regression equation in the form of:
Y=aXb where Y represents the workforce level a represents a regression constant (the intercept on the log-log-scale) X represents the cost parameter b represents the regression coefficient (the slope on the log-log scale) This equation has the property of presenting the regression curve as a straight line when plotted on a logarithmic ordinate or log-log scale. Each of the MER equations has an associated R2 value, which is a measure of dispersion of data along the regression line. The higher the magnitude of the correlation, the better the fit, or less scattered the data along the regression line. A correlation value of 1.0 indicates a perfect fit, 0.6 is considered very good, and 0.3 are considered acceptable in the social sciences.3
VI. Program/Project Cost and Schedule This modeling activity investigated schedule spans to see if inroads could be made into reducing the historically high level of optimism in initial master schedules produced when the project is in its mode of selling itself as a new start. Using the collected data, it was possible to develop probability distributions surrounding each of the stratified groups for each of the development phases. This provides NASA management with a tool to compare the master schedule of a proposed new start against the distribution of times required for a similar suite of work, and quantify the probability of accomplishing that part of development within their proposed time. NASA, historically, has resisted employing other than optimistic schedules at the start of a project for two reasons: • There is a widely held belief in “self fulfilling prophecies,” meaning that a project will use all of the time
allocated and then some. Therefore the prevailing lore is that a tighter schedule will result in an earlier delivery.
• All things being equal, the faster a project can be completed, the lower the final cost of that project. With a lower cost come the resources to accomplish more projects.
Unfortunately overly optimistic schedules result in two serious problems that work to negate the above potential savings in time and money. a. The first is that the likelihood and frequency of time-consuming rebaselining exercises is increased greatly.
During a rebaselining much work is put on hold and efficient progress comes to a stop. These rebaselinings result in a project’s taking more time to complete than had a realistic schedule been in place at the start.
b. Because the time is increased, the budget that is directly related to time expended is also increased. Not only is
the rebaselined project affected, but also as NASA management searches for the resources to support the new schedule, they often shave resources from other projects, which put stress on other well run projects. In the end, everything increases in cost, as an examination of NASA’s cost and schedule performance substantiates.
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Figure 1 shows the overall breath of NASA’s program and projects that range from 2.5 to 12 years in duration and $47M to $87B (combining both Saturn V and Apollo) in $2004.
Figure 1. NASA Program and Project Durations and Costs
Figure 2. NASA Unmanned projects.
Figure 2 is a replot of Figure 1 showing only unmanned programs. The lowest cost ($48M) and quickest from ATP to first flight (31 months) project in this database is the Magnetic Field Satellite (Magsat) project which was built in-house at NASA Goddard. The Viking project launched in 1975 for Mars exploration is the most expensive
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unmanned system with a total cost of $3,115M with a duration of 67 months. Twenty eight years later, the second generation Mars Exploration Rover was launched in 2003 after the first generation Pathfinder rover in 1997. Because of the experienced NASA/contractor team and technology demonstration 5 years earlier, it was one of the quickest projects in the database at 38 months with a cost of $511M, being 84 percent cheaper and 43 percent quicker than Viking. The Hubble Space Telescope project is saddled with being the longest unmanned project, 165 months, because of a 4 year delay after the original scheduled launch on the Space Shuttle Challenger and had the second highest cost of $2,992M. Manned spaceflight, as shown in Figure 3, is very costly. The total Apollo program approaches $100,000M with the Apollo Command and Service Module and the Lunar Module costing $40,677M and the Saturn V costing $36,126M. President Kennedy constrained the program schedule by announcing that the Nation would put a man on the moon by the end of the decade (8 years). The Gemini project appears to be a very cost effective and short project; however, the preliminary design and the associated costs were a part of the Mercury project.
Figure 3. Manned NASA Programs and Projects Duration and Costs The funding profiles for the present NASA program and project database are show in Figure 4. Most of the data show the “classic” profile with a buildup through ATP to PDR and CDR. Eighty percent of the peak between PDR and CDR. Many of the profiles have waves mostly due to NASA overall budget constraints. The funding profiles for selected manned and Mars programs is shown in Figure 5. Each of these programs/projects exhibit the classic profile; however, the Hubble profile is much stretched because of the sever funding constraints for the project and also the four year delay to launch because of the Space Shuttle Orbiter Challenger accident.
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Figure 4. NASA Program and Budget Funding Profiles for the Present Database.
Figure 5. Selected Funding Profiles of NASA Programs/Projects.
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As shown in Table III, the average NASA program/project takes 74 months to complete from ATP to first flight. As expected, the human space flights have a longer duration, 92 months, because of the complexity and interfacing of all architecture elements; the unmanned programs/projects have an average duration of 62 months. As shown in Figure 6, the data varies considerably for all the programs/projects shown for each of the phases. The duration of the Apollo program shows that duration can be constrained. The impact on total cost is unknown; however, the cost of parallel activities to complete the program must be traded with the opportunity to add addition risk mitigation work if the program had no schedule constraint.
Table III. Mean Schedule Durations for NASA Programs/Projects (months)
Figure 6. Program/Project Schedule Durations for Major Milestones
VII. MANPOWER ESTIMATING RELATIONSHIPS (MERs)
The programs and projects were analyzed to determine the NASA civil servant workforce utilized. As stated above, there were no consistent definition civil servants and no standard process for reporting.
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As shown in Figure 7a, an MER was developed for the complete project based on the maximum manpower (FTEs) used per year and the total cost of the project. Based on this data, the MER had an R2 of 0.69 which is very good considering the data sample and the differences between all the programs. There is a large uncertainty in the data because each program and project determines the work distribution between NASA personnel and contractor workforce. Many of the NASA centers have strategic policies to distribute NASA workforce on programs and projects for engineering and hardware development to maintain these core competencies. The MER developed for the manned program is quite good with an R2 of 0.91 (Fig. 7b); however, the relationship for the unmanned programs/projects is poor with an R2 of 0.44 (Fig. 7c). Additional data collection and analyses have to be performed to improve the understanding of the relationship. An attempt was made to segregate the data for what was considered an “in-house” project. The relationship for these projects was very good with an R2 of 0.75 as shown in Figure 7d.
Figure 7a. Workforce Relationship with Total Cost (all programs)
Figure 7b. Workforce Relationship with Total Cost (manned programs)
HC = 1.6253(Total Funding)0.6884
R2 = 0.6664
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Figure 7c. Workforce Relationship with Total Cost (unmanned programs)
Figure 7d. Workforce Relationship with Total Cost (unmanned, inhouse programs)
Finally, an analysis was conducted to determine the effect of the work required between the major program milestones (ATP-PDR, PDR-CDR, and CDR-first flight) on the MERs. In Figure 8a, it appears that civil service workforce doesn’t change significantly as a function of the development cycle. Workforce as a function of budget is virtually identical for the first two development phases whereas post-CDR workforce increases with smaller projects and has lesser workforce requirements for larger projects. This perhaps indicates that on larger projects the workforce transitions from design and building to integration and test (I&T) activities where the large design and build staff tails off. For smaller projects, a significant cadre is still needed to perform the I&T functions, but these
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personnel are less than the design/build staff fall-off. In fact for projects with annual funding of approximately $100M, the workforce remains constant regardless of the development phase. Both Figures 8a and 8b show little impact on workforce over the development phases on the average.
Figure 8a – Impact of Development Phase on NASA Manpower (unmanned programs)
Figure 8b – Impact of Development Phase on NASA Manpower (manned programs)
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Conclusion A database of NASA program and project cost, schedule, and workforce was developed. The data show that the
manned projects on the average take 30 additional months to complete and cost 40 to 80 times more than unmanned programs. Good correlation was determined between program and project costs and the number of supporting NASA civil servants. There was not a significant variation of the supporting NASA workforce as the programs and projects progressed through the development phases.
References 1Whitt, Freeman; Mikitish, John P., “Civil Service Manpower Model,” Planning Research Corporation, PRC D-2334-H,
under contract to NASA MSFC NAS8-36931, May 1990.
2Li, Allen, “NASA – Lack of Disciplined Cost-Estimating Process Hinders Effective Program Management,” General Accounting Office (GAO) Report to the Committee on Science, House of Representatives, GAO-04-642, May 2004.
3Evans, James R.; Olson, David L., Statistics, Data Analysis, and Decision Modeling, Prentice Hall, 2003, pg. 185.
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