The Hidden Cost of Reusability

All space flight providers want to control costs. From the traditional government and commercial enterprises to the new entrants, all want to keep costs as low as reasonably possible. Gone a long time ago—and forever—are the days of unlimited resources to get the job done. Bottom lines matter, and matter a lot.

It has long been argued that one way to keep costs reasonable is to reuse launch hardware. Even when adding the required refurbishment/reflight checks, repairs, component replacements, etc., to the equation it can be shown on paper to save money in the long run. The Shuttle was sold to Congress in part on this philosophy. And being the first reusable spacecraft they could know no different.

Nor could NASA fully know the long-term implications of reusability.

An additional fact is this: Adding astronauts to the equation requires changing ‘reasonably’ to safely. No argument there, right? But what are the implications of this change? Simply put, based on Shuttle experience, it requires lots more of the checks, repairs, component replacements, etc., in an attempt to make the re-flight as technically close to the first as possible. The newer the hardware, the less risk of failure. No argument there either.

These costs are easy to understand and accept. What about the posting’s title? Hidden? I have alluded to it in earlier postings and it’s not just a financial issue. It can cost a lot more than money.

Here it is:

With the desire to refly hardware that has (theoretically) performed well before, a tendency to rely on past performance when approving current flight rationale is given more weight than it should.

That tendency can either be seen overtly, or it can be latent. If obvious, it can be dealt with through open discussion and full debate of the issue at hand. If hidden, it can fester, grow, become a ‘new normal’—or worse, lead to disaster.

Examples in the Shuttle program are numerous. From those we recognized and dealt with—wire chafing, flow liner cracks, hydrogen leaks—to those that dealt us the most severe of consequences—foam shedding, O-ring scorching—we were challenged by the need to re-fly hardware, all with the overarching tenet of doing so safely.

Tragically, we didn’t always balance that correctly.

I sincerely hope today’s and tomorrow’s astronaut launch providers succeed 100% of the time. Recognizing when a ‘new normal’ is kicking in is part of the success criteria.

spacex-falcon-9-crs-9-landing
SpaceX Falcon 9 first stage returns to Earth after the CRS-9 launch. (Photo courtesy SpaceX)

Author: Mike Leinbach

Mike was the final Space Shuttle Launch Director at NASA's John F. Kennedy Space Center. He led the launch team for all Shuttle missions from August 2000 to the end of the program in 2011, giving the final "go" for every launch.

3 thoughts on “The Hidden Cost of Reusability”

  1. You realize that neither failure of the shuttle had anything to do with reusing the hardware. O-ring blow by in freezing weather and foam strikes on the wing. Those failures were due to NASA management “normalizing” these risks.

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    1. Both the Challenger and Columbia investigations noted that hardware degradation had occurred because of reuse and possibly contributed to the accidents.

      In Challenger, the board noted that the “diameters of the two solid rocket motor segments had grown as a result of prior use,” to the extent that the tang-to-clevis gap was twice that which normally assured that the O-ring was compressed against all of the walls in the joint. The segments were also out-of-round, also as a result of multiple reuse. While neither of these were the direct cause of the accident, they were both noted as possible contributing factors.

      With Columbia, NASA and the CAIB noted prior to the cannon tests at the Southwest Research Institute that the RCC in the wing leading edge panels became thinner and more brittle with multiple uses. That’s why NASA pulled flown RCC panels from Atlantis and Discovery for the impact tests, because those two vehicles had similar wear and tear on the RCC as did Columbia. Would the ET foam have broken a brand-new RCC panel? Unknown.

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  2. The point i was trying to make is that with reusability comes an unwanted tendency to accept prior flight minor hardware issues as part of the rationale to fly the next mission even if those issues have not been fully resolved. Think of my point more in terms of flying the same type of system multiple times rather than actually re-using specific hardware — which has its own issues as Jonathan points out. It’s more of a management challenge to ignore prior flight performance when dispositioning problems of a repetitive nature than a physical degradation of hardware. The Shuttle’s thermal protection system spec assumed no impacts. The O-rings were not designed for scorching on any level. The hidden cost is when these minor issues suddenly become major cost or schedule issues, or worse, though they could have been fixed by getting ‘back to spec’. Normalization of deviance is real and needs to be recognized. Once realized it can be dealt with. I hope this helps you understand my original posting. Mike.

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