Federal Aviation Administration Commercial Space Transportation Human Space Flight Occupant Safety Telecon Telecon 6 – Fault Tolerance, Margin and Reliability January 15th, 2013 Mike Machula Tom Martin

Office of Commercial Space Transportation Federal Aviation Administration 2 Agenda Introduction Rules of Engagement Next Steps Last Month’s Topic Today’s Topic Wrap-up Today’s facilitators are Mike Machula and Tom Martin

Office of Commercial Space Transportation Federal Aviation Administration 3 Introduction The FAA may not propose regulations covering occupant safety until October We now plan to turn our efforts to drafting guidance and best practices. We'd like input from technical folks from industry and government to help us. We are hosting a series of one-hour telecons, each with a narrow focus on a specific technical topic to be held about once a month. We are using our industry advisory committee, COMSTAC, to help us. We are not soliciting any proposals for agency support on this topic at this time. This is background research.

Office of Commercial Space Transportation Federal Aviation Administration 4 Rules of Engagement 1. When speaking, please identify yourself so we can follow up with you if we have more questions. 2. We are recording this teleconference. We will publish minutes that summarize the discussion. 3. Please limit your time to 5 minutes of time to allow for greater participation. You are welcome to follow up with a phone call or to Randy Repcheck at or Call-in information: Call-In Number: (605) Participant Access Code: # Help Line (For Problems with Connection):

Office of Commercial Space Transportation Federal Aviation Administration 5 Next Steps After today’s meeting, we will take some time to put together minutes and publish them on the AST website. The minutes will contain a list of attendees, the topic(s) discussed, and a summary of what was discussed. We look forward to you participating in the next conference call on March 12 th 2013 at 1 pm Eastern. No February telecon due to 16 th annual AST Commercial Space Transportation conference February 6 and 7.

Office of Commercial Space Transportation Federal Aviation Administration 6 Aborts and Abort Systems We worked to identify the applicability of abort systems as part of fault tolerance, the applicable flight phases and designs it should apply to (e.g. suborbital?), and the abort reliability and the level of care an occupant should expect during an abort. Last Month’s Topic (18 December 2012)

Office of Commercial Space Transportation Federal Aviation Administration 7 Today’s Meeting Objective To explore industry views on how to balance fault tolerance, design margin, and reliability to achieve reasonable occupant safety

Office of Commercial Space Transportation Federal Aviation Administration 8 Today’s Discussion Topic Fault Tolerance, Margin and Reliability. To allow for industry innovation, the commercial sector wishes to be free to the maximum extent possible to choose between fault tolerance, design margin, and reliability. Today’s discussion explores the best practices of applying fault tolerance, margin and reliability from a guidance perspective.

Office of Commercial Space Transportation Federal Aviation Administration 9 Questions for Today’s Discussion Topic We will discuss the following questions from a guidance perspective: a)What would be appropriate rationale at a functional level for a choice of fault tolerance, design margin, or high reliability to protect the safety of the occupants? b)What is the minimum recommended level of fault tolerance? Is it different for orbital vs. suborbital?

Office of Commercial Space Transportation Federal Aviation Administration 10 Today’s Discussion Topic Continued c)When is risk high enough to justify additional fault tolerance? d)What determines whether fault tolerance should be handled at the function level or system level?

Office of Commercial Space Transportation Federal Aviation Administration 11 Discussion a)What would be appropriate rationale at a functional level for a choice of fault tolerance, design margin, or high reliability to protect the safety of the occupants? When would redundancy be recommended? What differentiates redundancy from high reliability? How do you measure and demonstrate high reliability? When would it be appropriate to solely rely on design margin? What determines how much margin is recommended?

Office of Commercial Space Transportation Federal Aviation Administration 12 Discussion Continued b)What is the minimum level of recommended fault tolerance? Is it different for orbital vs. suborbital? AST thinks that a single fault tolerance for critical functions, with abort capability for orbital flights, is generally acceptable Should human errors “stack?” In other words, should it be recommended to protect for a single system failure combined with a single human error? What would be the rationale for having different recommended levels of fault tolerance between orbital and suborbital? Exposure time? Severity of the environment?

Office of Commercial Space Transportation Federal Aviation Administration 13 Discussion Continued c)When is risk high enough to justify additional fault tolerance? What critical functions/systems would be high risk and how is the risk determined? When would dissimilar redundancy be appropriate? When is risk low enough to negate the need of fault tolerance?

Office of Commercial Space Transportation Federal Aviation Administration 14 Discussion Continued d)What determines whether fault tolerance should be handled at the function level or system level? Does the criticality or complexity of the system determine it?

Office of Commercial Space Transportation Federal Aviation Administration 15 Wrap-up Thanks to everyone for participating! You can post comments, questions, etc. to Docket FAA If anyone has any new topics or suggestions on improving this discussion process, contact: We look forward to you participating in the next conference call on March 12th. The topic will be “ Medical Best Practices for Crew & Space Flight Participants ”.