A flash from the past and a view of the present:
The following is a vehicle that is designed for support, little if any (Photo 1). Unfortunately, it does not exist. This is an artists conception of Shuttle operations dating back to the early 70's. During the planning phases for Shuttle a 160 hour timeline for turnaround was used as a goal. Today, the RLV program is using a 96 hour timeline as a turnaround goal. Obviously, Shuttle never met it's goal. It is not likely Shuttle will ever come even close to a 160 hour turnaround time. Why did this vast difference between vision and reality occur? Why the dissonance between the goal and the result? Most importantly, how can we, NASA and industry, learn from this valuable experience?
This is the reality, below (Photo 2). Shown is an orbiter in the Orbiter Processing Facility (OPF). Yes, it's somewhere in there. What assumptions were being made in the vision conceived above? First off, the vehicle above is highly reusable. Access is not required above, hence the lack of platforms. The vehicle below, however, really has only partial reusability, hence the platforms from end to end in every nook and cranny, in order to get at things and change them out. The vehicle above apparently has robust, maintenance free thermal protection systems (TPS). Again, no access is required above, not even for an up close look. Below, the TPS is fragile, easily damaged and needs waterproofing. Hence the platforms - again. Of course, access for parts removal and replacement or fixing doesn't help the TPS situation below - just more opportunities to damage fragile tile.
The first photo says more. Notice the doors - open in 1 gravity all on there own. This is a robust vehicle where operations was the focus, not just the 8 minutes of flight or 7 days in orbit.
The first photo also would seem to be inexpensive as far as infrastructure. Witness the sparse facility and the lack of connections to the vehicle. The "reality" photo is quite the contrary.
How can RLV avoid having the goal and the result be so different?
Another flash from the past? No, Photo 3 is a current RLV artists conception, one of many possibilities. Time has transformed the tools of the artists - computers have replaced the paintbrush. Will anything else be different?
Deja vu all over again? Hopefully not.
There is one photo missing here. The actual next generation reusable launch vehicle.
Again, how can the future be different? The RLV program is a technology development and demonstration program. How are priorities determined? With a proper focus on operations and design for support, certain technologies merit pursuit. Others do not. Consider the following measurable criteria:
1) Minimize the number of separate vehicle systems, subsystems, GSE and facilities.
2) Minimize the number of potential leakage sources.
3) Minimize the number of hands-on activities required (to handle, assemble, verify functionally, checkout, service, launch, flight operate, land, secure, safe, etc...)
4) Minimize the number of different fluids used.
5) Minimize the number of active components required to test and function.
6) Maximize the use of components with demonstrated high reliability (0.99999...)
7) Minimize the number of active systems required to maintain a safe vehicle.
8) Minimize the number of systems requiring monitoring because of hazards.
9) Maximize automation, autonomy and BIT/BITE.
10) Minimize the number of interfaces requiring engineering control.
These criteria (part of a larger set) are prioritized by order of importance. Quality Function Deployment techniques have surfaced them (such as the pre-RLV Space Propulsion Synergy Group) and some RLV (Operations Synergy Team) strategic planning work has used them. By using these "forcing functions" tied intrinsically to higher level goals of affordability and availability the missing photo may end up more like the first above - or, hopefully, better.
These criteria are also a part of Document 1 - Operability Criteria, a sub-part of the OST Concept Vision and used in exercises such as Document 2 - Technology Priorities Identification.
This is not to say measurable criteria are an end all, be all. Knowing what to focus on technologically in developing a product is key however, and operator input can provide that insight. QFD approaches simply provide the much needed means of manifesting operator goals (aircraft-like operations, high reusability...) and higher level goals (routine, affordable access to space) in a design approach. Measuring up any launch system concept as it evolves against these criteria serves to indicate if the direction is toward Photo 1 or Photo 2.
Data is another key aspect of assuring a future vehicle design that is supportable - if it is the right data. Knowing the recurring cost of a system can give key insight into where improvement is most needed. For example, what is the recurring cost of the Shuttle Main Propulsion System? How much does it cost to turnaround the hydraulic system? This information is key to knowing the economic impact of decisions to improve, upgrade or apply new technology to a future system. If obtained and applied it can, again, significantly aid in realizing those high level goals.
Realizing the truly significant metrics, obtaining this information, and focusing on the drivers indicated by the data, a course can be set to acquire the delta factor of improvement that will realize our goals.
Through this, and more, we will truly assure one day that the missing photo, once it appears, is looked back upon by future generations as having been what opened the space frontier.
Edgar Zapata
Return to KSC Next Gen Site
Edgar Zapata, NASA Kennedy Space Center
Shuttle Process Engineering Directorate, Fluid Systems Division