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Space Shuttle Operations Zero Base Cost Study (1991)

July 2, 1991


The Space Shuttle Program Zero Base Cost Study was a key Shuttle cost study of the early 1990’s. This study was at the front end of numerous studies to follow addressing what was to come after the Space Shuttle. These 2 charts below are some of the more significant pieces of information when trying to understand the evolution of human space flight technology, infrastructure and business processes.

Download the Summary Zero Base report (39 pages, .pdf) or the Full Zero Base report (7MB, 248 pages, .pdf).


For further information on these studies contact Edgar Zapata at






1: Do NOT confuse a “Zero Base” amount with “yearly costs”, “required budget” or “expense” amounts any given year for achieving a certain number of flights, as utilization in any given year may or may not alter actual costs, required budget amounts or total expenses. For example, if planning on 5 flights, but making only 4, the dollar difference is actually manifest not as a savings but as simple under-utilization due to unforeseen events. The difference would likely still exist as a cost, have to be budgeted for and “expensed” at the flight rate of 5. Hence, a Zero Base concept goes hand-in-hand closer to the notion of "steady states" over many years or capacities maintained or targeted on a steady basis.


2: Do NOT confuse a “Zero Base” concept with that of “fixed costs”. The Zero base assumes that the capability exists only for the indicated number of flights and workforce, facility, equipment, flight or ground, is not a cost if it is not required to achieve the indicated flight rate. For example, if at a flight rate of 3 only 2 Orbiter Processing Facilities (OPF) are required, rather than the 3 that exist, the values shown for a flight rate of 2 do not include any costs with the 3rd OPF. This was stated in the study as:

“At low flight rates, when facilities or vehicles are not needed to support the flight rate, they are not maintained”

“No cost included for retention of capability to increase flight rate capability at a later date”

“No OMDPs performed on orbiter vehicles not required to meet the steady state flight rate”

“For each flight rate case, that flight rate is the assumed steady state flight rate for all future years”

However, in general a lower number compared to 100 units in the column for a steady 6 flights per year would likely indicate a higher fixed cost if that value were to be studied separately. Example – a 119.3 in column 6 would indicate a stronger fixed cost behavior there than in a column 6 with a value of 135.2. This reflects on the issue of the NASA Space Shuttle, or such related architecture, workforce, business process, and business technology fixed costs.


3: How to read this table? Example 1 - there is no difference in cost that can be found at the Michoud Louisiana External Tank (ET) Manufacturing site between having a production capacity of 1, 2, 3 or 4 ET’s, but if the capacity for manufacturing 5 tanks in a year were targeted and maintained that cost would be 4.2% higher than the capacity cost compared from 1 to 4 tanks a year. Example 2 – If mission operations at the Johnson Space Center (JSC) cost “100” units to have a capability to launch the Shuttle once per year, then to launch twice per year on a steady state basis would be 4.1 % more.



Website Contact: Edgar Zapata, NASA Kennedy Space Center