Are the countdown steps of Delta-IV (or any other rocket) public? (at least for last 10-20 minutes)
Quote from: Antares on 12/04/2014 01:02 pmQuote from: MATTBLAK on 12/04/2014 12:54 pmQuote from: Steven Pietrobon on 12/04/2014 12:48 pmProblems with port and core valve cycling. LOX valves are OK. The problems are with the LH2 valves.'Sticky' valves from a long pre-launch cold soak?Concur.So is the valve not working to spec? Or the spec does not require the valve to work after a long hold? Either one seems odd to me - long holds are hardly an unusual occurance, so it should be covered by the spec. And on the valve side, surely some acceptance test requires it to work after a long cold soak.
Quote from: MATTBLAK on 12/04/2014 12:54 pmQuote from: Steven Pietrobon on 12/04/2014 12:48 pmProblems with port and core valve cycling. LOX valves are OK. The problems are with the LH2 valves.'Sticky' valves from a long pre-launch cold soak?Concur.
Quote from: Steven Pietrobon on 12/04/2014 12:48 pmProblems with port and core valve cycling. LOX valves are OK. The problems are with the LH2 valves.'Sticky' valves from a long pre-launch cold soak?
Problems with port and core valve cycling. LOX valves are OK. The problems are with the LH2 valves.
When is next launch window?
Stupid Question: what are the causes of the limited launch window?
I hate a very noobish question from earlier today.Why isn't there strict security for boaters?
Will this valve problem cause trouble during detanking?
So is the valve not working to spec? Or the spec does not require the valve to work after a long hold? Either one seems odd to me - long holds are hardly an unusual occurance, so it should be covered by the spec. And on the valve side, surely some acceptance test requires it to work after a long cold soak.
Thinking about this some more. Surely the valve is designed to work even after a cold soak - it's a known operating condition. And so surely they took at least one valve, soaked it in liquid hydrogen for 6 hours (or whatever the longest cold soak might be) then verified it still worked.But I guess they don't do this for each valve off the production line, since such a test is cumbersome and expensive.
A second article from Businessweek with an interesting claim:Businessweek - Why NASA's Orion Spacecraft Looks So Familiar"Orion is roughly three times larger than the Apollo crew module, built to carry four astronauts as far as Mars, a 70-million mile round-trip journey that could take as much as 23 months."It's amazing the pervasiveness of this meme.