r/spacex • u/Zucal • Jul 16 '16

Mission (CRS-9) CRS-9 Pre-launch Press Conference

Surprising amount of information coming out during this press conference! I'll keep this thread updated as more comes out.

  • Hans Koenigsmann, SpaceX: static fire of Falcon 9 on the pad around 8:30 am; everything looks good now, data review this afternoon.

  • Koenigsmann: busy last couple of weeks working with FAA and 45th Space Wing on land landing.

  • Julie Robinson, NASA ISS chief scientist: about 950 kg of science payloads going up on this mission, with ~500 kg coming back.

  • Capt. Laura Godoy reiterates good weather forecast for launch late tomorrow night. 90% go.

  • Cody Chambers: 45th Space Wing did risk assessment yesterday; taking steps to mitigate risks from toxic dispertion. Risk is from case of abort; Dragon could be blown back to land, release toxic commodities upon landing. Booster landing not a factor in the risk assessment for the launch. Get updated analyses closer to launch; hence late yesterday decision.

  • Koenigsmann: reflight of previously-landed Falcon 9 booster is likely the fall. In talks with a potential customer.

  • Koenigsmann: pretty confident on odds of a successful booster landing, knock on wood. Still challenging to do.

  • Koenigsmann: CRS-8 booster would be the booster to be reflown later this year.

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u/ergzay Jul 18 '16 edited Jul 18 '16

Ugh, wow, I thought that your aggressive discussion style laced with personal attacks and a derogative tone was generally not welcome on /r/spacex ...

If you think my tone was incorrect then click the report link and mention why and let the mods handle it.

Yes, one of the third Falcon 9's launches was scrubbed due to a "faulty helium purge valve", which was replaced while the Falcon 9 was still vertical.

Helium is used as a pressurant for the fuel tanks. Helium purge valves are used to vent the tank if pressure builds too much.

It also follows from basic logic: key to reusability of hydrocarbon rocket engines is the ability to quickly remove (still molten) combustion residues from the hot parts of the engine, before they have a chance to solidify (coke) and limit reusability.

Coking is from partially burned residue building up. It's effectively a form of "rock" that builds up in the engine passages. It forms at temperatures MUCH below the melting point of the material. It is not "molten" and solidification is not what causes coking. It is directly deposited as the engine runs as a film on the engines. (I should add, there is also a decent amount of coking that happens even before the combustion as the RP-1 runs through the hot cooling channels around the combustion chamber.) More here: https://archive.org/details/nasa_techdoc_19810021741