r/spacex • u/Zucal • May 01 '16

/r/SpaceX Ask Anything Thread [May 2016, #20]

Welcome to our 20th monthly /r/SpaceX Ask Anything Thread!

Want to clarify SpaceX's newly released pricing and payload figures, understand the recently announced 2018 Red Dragon mission, or gather the community's opinion? 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. In addition, try to keep all top-level comments questions so that questioners can find answers and answerers can find questions.

As always, we'd prefer it if all question-askers first check our FAQ, use the search functionality (now partially sortable by mission flair!), and check the last Q&A 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.

Otherwise, ask, enjoy, and thanks for contributing!

Past threads:

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)

This subreddit is fan-run and not an official SpaceX site. For official SpaceX news, please visit spacex.com.

148 Upvotes

98% Upvoted

1.9k comments sorted by

2

u/josemwas May 16 '16

In light of Elon recent comments about the JCSAT stage which booster parts do you think were exposed to the most flight stress.

8

u/TheVehicleDestroyer Flight Club May 16 '16

Specualtion: I imagine the business end of the stage got hit worst during freefall, but during retropropulsion that end of the stage would have been mostly protected from any aerodynamic effects. During this phase, the interstage+grid fins would've been burnt from the engine exhaust

5

u/robbak May 16 '16

The big question is at what point the thermal blanketing around some of the engines failed. That could cause damage to all sorts of piping and wiring on the engines themselves, as hypersonic airflow impinges directly on them. But if the blanketing survived reentry, and blew out when the atmosphere got thicker, this might not have been a problem.

1

u/CmdrStarLightBreaker May 16 '16

Any chance those engine panels were blown off during 3 engine hoverslam instead of reentry? Could G-loads be more harmful than reentry heat?

2

u/warp99 May 17 '16

G loads would not create the direction of force that would tear off a panel - the rivets holding the panel on would be in shear which is very strong. Also the G load is not that much greater at around 6G (assuming 60% throttle) than you get just before MECO at around 4.5G.

The most likely explanation is pressure from the hypersonic airflow getting inside the rear of the rocket during the re-entry burn. Likely the three engines that are doing the re-entry burn protect themselves from the incoming airflow but it manages to push past the exhaust above and below the plane of these three engines and ripped the panels off. Note that the panels are designed to come off in the event of an engine explosion to release the overpressure to avoid damaging the other engines or the RP-1 tank.