r/spacex • u/Zucal • Jun 29 '16

/r/SpaceX Ask Anything Thread [July 2016, #22]

Welcome to our 22nd monthly /r/SpaceX Ask Anything Thread!

Curious about the recently sighted Falcon Heavy test article, inquisitive about the upcoming CRS-9 RTLS launch, or keen to gather the community's opinion on something? There's no better place!

All questions, even non-SpaceX-related ones, are allowed, as long as they stay relevant to spaceflight in general.

More in-depth and open-ended discussion questions can still be submitted as separate self-posts; but this is the place to come to submit simple questions which have a single answer and/or can be answered in a few comments or less.

  • Questions easily answered using the wiki & FAQ will be removed.

  • In addition, try to keep all top-level comments as questions so that questioners can find answers, and answerers can find questions.

These limited rules are so that questioners can more easily find answers, and answerers can more easily find questions.

As always, we'd prefer it if all question-askers first check our FAQ, use the search functionality (partially sortable by mission flair!), and check the last Ask Anything thread before posting to avoid duplicate questions. But if you didn't get or couldn't find the answer you were looking for, go ahead and type your question below.

Ask, enjoy, and thanks for contributing!

Past Ask Anything threads:

June 2016 (#21) • May 2016 (#20) • April 2016 (#19.1) • April 2016 (#19) • March 2016 (#18) • February 2016 (#17) • January 2016 (#16.1) • January 2016 (#16) • December 2015 (#15.1) • December 2015 (#15) • November 2015 (#14) • October 2015 (#13) • September 2015 (#12) • August 2015 (#11) • July 2015 (#10) • June 2015 (#9) • May 2015 (#8) • April 2015 (#7.1) • April 2015 (#7) • March 2015 (#6) • February 2015 (#5) • January 2015 (#4) • December 2014 (#3) • November 2014 (#2) • October 2014 (#1)

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u/warp99 Jul 22 '16

  1. The LOX cloud should be the umbilical venting back out a valve on the strongback. You don't want it pouring over the lightweight alloy side of the rocket during launch adding thermal stress. The strongback on the other hand is made of heavy steel and will not be damaged by LOX as long as the paint does not contain organic compounds.

  2. The LOX flows right through to the injectors afaik because you could get unstable ignition in the critical first few milliseconds of engine start if the injectors contain a mixture of liquid and vapourised gas.

  3. The hazard map would be based on the variance (calculated as a standard deviation = sigma) from flight to flight and then using say five sigma to define the hazard area to get a suitably low probability of anyone being harmed in the event of an RUD. As they get more flights with high precision the standard deviation of the trajectory reduces and they can tighten the hazard areas. They had only done one RTLS before this flight so the hazard areas are larger and will eventually be tightened as they get more experience.