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Space Transportation Systems "-ilities"

Affordability, Reliability, Safety, Maintainability, Operability, Complexity, Sustainability & Responsiveness


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Affordability, Competition, Business Models and Acquisition Approach

"Air Mail Act of 1934 - Aerospace history can provide us some inspiration on this subject. The air transportation world in the early 1930s ran into the ethical problems that can often occur in completely vertical business arrangements with a narrow set of players. The issue was finally resolved through anti-trust legislation in the Airmail Act of 1934."


Affordability, Operability, Design for Operations


It is envisioned that dramatically safer, lower cost, and higher flight rate access to space is possible by applying the wealth of experience gained from human space flight launch operations. Shuttle launch operations, particularly the world’s only reusable space plane elements, the orbiters, have accumulated a vast set of ideas, lessons learned, insight and “design for ops” experience.


"Designers of space launch systems should be cognizant of the impact of their design assumptions on operational characteristics. Operational metrics such as turnaround time, recurring cost, and headcount are critical factors for the future viability of such systems. The results presented here are from a study that seeks to determine in what manner design approaches can improve the operability of future space launch systems. This is accomplished by applying such operational approaches at the start of the concept design process."


Responsiveness, Direct Labor

"Prediction is very difficult, especially about the future." -Niels Bohr


While scheduling a series of launches results in a plan that is worked to, system reality involves uncertainty, variability, and randomness. The long-view question becomes not "when are we planning to launch", or "how many launches are we planning for any year". The long view asks "what are the chances we will launch by a given date" or "what are the chances we will achieve a given number of launches by a set time in the future".

The Process for Simulation Modeling and Analysis of Space Shuttle Manifest Options

Shuttle Launch Pad Operations Added Work Days Post the Delta Launch Site Flight Readiness Review



Reliability, Safety








  • DATA: A Review of Space Shuttle Repair Data, Shuttle Orbiter Line Replaceable Units (LRUs) Replaced per Flight During Orbiter Processing Facility (OPF) Turnaround Operations, through STS-97, 2000

NASA Cost Models, Operations


These documents are the result of surveys into government, industry and academia in search of data, tools, software or capabilities applicable to the field of space transportation operations cost/time analysis and assessment.


"System Reliability, Maintainability and Supportability are the critical elements in obtaining SLI goals - unless these are the primary considerations in design and development, these goals will remain beyond reach."

"There seems to be a lack of organized data about current processes. Discussions with tool developers revealed a shortage of organized historical data about the details of shuttle processing. This data must be gathered so that it may be used to validate models for future vehicles."

"Parametric modeling, on the other hand, takes a more thermodynamic‟ approach, and determines costing based on more general driving parameters such as size, complexity, and application specific drivers."

"The user must be cautioned that the toolbox is a decision aid, not a decision maker; meant to supply insight, not directives."


  • DATA: A Review of Space Shuttle Repair Data, Shuttle Orbiter Line Replaceable Units (LRUs) Replaced per Flight During Orbiter Processing Facility (OPF) Turnaround Operations, through STS-97, 2000




Affordability, Maintainability, Space Shuttle Thermal Protection Systems (TPS)


The following file on Shuttle Orbiter Thermal Protection Systems (TPS) maintenance contains data that is extremely valuable to operations analysis such as relates to maintainability for one of the many complex systems on a reusable space transportation systems element. It is one piece of a much larger set of issues, including safety and reliability, relating to TPS systems, current and future. The CAIB report, coupled with the data herein, demonstrates how systems such as RCC can appear robust, but still be both un-safe and difficult to maintain, having an ill understood set of failure modes that can contribute to a low overall reliability/safety/operability.

And from the CAIB report, page 83:

"The wing leading edge Reinforced Carbon-Carbon composite material and associated support hardware are remarkably tough and have impact capabilities that far exceed the minimal impact resistance specified in their original design requirements. Nevertheless, these tests demonstrate that this inherent toughness can be exceeded by impacts representative of those that occurred during Columbia's ascent."



Reliability, Operability, Space Shuttle Main Engine (SSME)



For future systems to improve on the Space Shuttle it is extremely valuable to analyze and understand the Shuttle operations experience qualitatively and quantitatively. One such report follows specific to the Space Shuttle Main Engines (SSMEs).

All the "-ilities".





Reliability, Maintainability, Ground Operations, Rocket Engines

  • NASA Marshall Space Flight Center & Rocketdyne, "Report on Rocket Engine Life Analysis," August 1996 (for the HRST Study)

    • The report describes methods to extend rocket engine life, while increasing safety in flight, reducing failures and reducing operational costs. Additionally, the report provides information on how future reusable engine designs would avoid having to remove engines from flight to flight, as done with the Space Shuttle Main Engines.



Maintainability, Space Shuttle Thermal Protection Systems (TPS)


For future systems to improve on the Space Shuttle it is extremely valuable to analyze and understand the Shuttle operations experience both qualitatively and quantitatively. The Shuttle Thermal Protection System (TPS) experience is one such example.

Reliability, Safety




This work by the Operations Synergy Team was in preparation for and predates the selection of Lockheed-Martin to build the X-33. The files are still very relevant to future technology pursuits and space transportation systems affordability.








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Website Contact: Edgar Zapata, NASA Kennedy Space Center