SCRUB: SpaceX Falcon 9 v1.1 - CRS-3 Dragon - ATTEMPT 1 UPDATES

[yg1968]

Here is a replay of the NASA TV coverage of the scrub:

[jacqmans]

Forecast 40 Percent 'Go' if SpaceX-3 Aims for Friday Launch

April 15, 2014 - 9:20 AM EDT

If NASA and SpaceX officials decide to attempt to launch SpaceX-3 to the International Space Station on Friday, April 18, there is a 40 percent chance of favorable weather. The U.S. Air Force 45th Weather Squadron issued its L-3 forecast, which predicts a chance of showers and thunderstorms that could result in violating the Thick Cloud, Lightning and Flight Through Precipitation rules.

Monday's launch attempt was scrubbed because of a helium leak in the first stage of the Falcon 9 rocket. The next possible launch opportunity would be April 18 at 3:25 p.m. EDT, pending resolution of the issue and a decision by NASA space station and SpaceX managers.

[beancounter]

they use helium for turbopump spin up, right?  Or was this for the helium tanks for the legs?

Fuel pressurization.  Secondary function is leg deployment.

And stage separation, which happens to be today's culprit, I'm hearing.

Do the pneumatic pushers utilise helium?

[beancounter]

No, F9 uses pneumatic pushers, not helium.

Huh?  The pneumatic pushers use helium

Yes sorry just realised my error and asked the question.

[Chris Bergin]

New article today to update where we are, and I'll use William's article for the Friday attempt.

....

SpaceX:

NASA and SpaceX have confirmed Friday, April 18 for the next launch attempt for the Falcon 9 rocket to send the Dragon spacecraft on the company's third commercial resupply mission and fourth visit to the space station. Launch is targeted for 3:25 p.m. ET. The launch will be webcast live at www.spacex.com/webcast beginning at 2:45 p.m. ET.

 

A launch on Friday results in a rendezvous with the space station on Sunday, April 20 and a grapple at 7:14 a.m ET.

 

During Monday’s launch attempt, preflight checks detected that a helium valve in the stage separation pneumatic system was not holding the right pressure. This meant that the stage separation pistons would be reliant on a backup check valve.

 

No issue was detected with the backup valve and a flight would likely have been successful, but SpaceX policy is not to launch with any known anomalies. We have brought the vehicle back to horizontal and are replacing the faulty valve, as well as inspecting the whole system for anything that may have contributed to the valve not working as designed.

[yg1968]

http://www.nasa.gov/mission_pages/station/structure/launch/index.html

SpaceX Launch Reset for Friday
April 16, 2014 - 8:28 AM EDT

The International Space Station Program and SpaceX have selected Friday, April 18 for the next launch attempt for the Falcon 9 rocket to send the Dragon cargo craft on the company's third commercial resupply mission to the space station. Launch is scheduled for 3:25 p.m. EDT. NASA TV coverage will begin at 2:15 p.m.

A launch on Friday results in a rendezvous with the space station on Sunday, April 20 and a grapple at 7:14 a.m. NASA TV coverage will begin at 5:45 a.m. with berthing coverage beginning at 9:30 a.m.

The U.S. Air Force 45th Weather Squadron forecast predicts a 40 percent chance of favorable weather, with a chance of showers and thunderstorms that could result in violating the Thick Cloud, Lightning and Flight Through Precipitation rules.

SpaceX has settled on a backup launch date of Saturday, April 19 for the best pair of launch dates for the science payloads being delivered to the station. If needed, a Saturday launch would occur at 3:02 p.m. NASA TV coverage would begin at 2 p.m. This would be a three-day transit to the station instead of two days with grapple on Tuesday, April 22.

If SpaceX launches Friday, a contingency spacewalk to replace a failed multiplexer-demultiplexer will be conducted on Wednesday, April 23. If SpaceX scrubs Friday and attempts to launch Saturday, the contingency spacewalk moves earlier to Sunday, April 20.

[yg1968]

If Friday doesn't work out, the backup date is Saturday according to the press release above.  Is the weather more favourable on Saturday?

[Lurker Steve]

No issue was detected with the backup valve and a flight would likely have been successful, but SpaceX policy is not to launch with any known anomalies. We have brought the vehicle back to horizontal and are replacing the faulty valve, as well as inspecting the whole system for anything that may have contributed to the valve not working as designed.

Sure, the backup value worked. But if there was a helium leak, would there be enough gas remaining in the system ? Is it just a backup value, or an entire duplicate set of helium lines that are able to maintain pressure when the primary lines have low pressure due to the leak ?

[Space Pete]

So, two scenarios then:

Scenario 1:
SpX-3 launch: Friday 18/04 @ 3:25 PM EDT / 7:25 PM GMT
SpX-3 capture: Sunday 20/04 @ 7:14 AM EDT / 11:14 AM GMT
MDM R&R EVA: Wednesday 23/04

Scenario 2:
SpX-3 launch: Saturday 19/04 @ 3:02 PM EDT / 7:02 PM GMT
SpX-3 capture: Tuesday 22/04
MDM R&R EVA: Sunday 20/04

[dsmillman]

So, two scenarios then:

Scenario 1:
SpX-3 launch: Friday 18/04 @ 3:25 PM EDT / 8:25 PM GMT
SpX-3 capture: Sunday 20/04 @ 7:14 AM EDT / 12:14 PM GMT
MDM R&R EVA: Wednesday 23/04

Scenario 2:
SpX-3 launch: Saturday 19/04 @ 3:02 PM EDT / 8:02 PM GMT
SpX-3 capture: Tuesday 22/04
MDM R&R EVA: Sunday 20/04

GMT is four hours later than EDT not five. Please adjust the times.

[Space Pete]

GMT is four hours later than EDT not five. Please adjust the times.

Oops, right you are! I accidentally adjusted them for British time, forgetting that the UK is now on BST, now GMT. Post adjusted.

[yg1968]

So, two scenarios then:

Scenario 1:
Scenario 2:

I thought that there was parts that needed to be delivered on the CRS-3 flight in order for the EVA to be done. But under scenario 2, the EVA is done prior to capture. So I imagine that they will do without these parts if the launch is on Saturday.

[Kabloona]

No issue was detected with the backup valve and a flight would likely have been successful, but SpaceX policy is not to launch with any known anomalies. We have brought the vehicle back to horizontal and are replacing the faulty valve, as well as inspecting the whole system for anything that may have contributed to the valve not working as designed.

Sure, the backup value worked. But if there was a helium leak, would there be enough gas remaining in the system ? Is it just a backup value, or an entire duplicate set of helium lines that are able to maintain pressure when the primary lines have low pressure due to the leak ?

It sounds like a leaking check valve that wasn't "checking" sufficiently to hold pressure...ie an internal leak, not an external leak. In which case it was not a question of losing helium to the atmosphere, and thus running out of helium, but of potentially not having adequate helium pressure in one branch of the pusher plumbing.

Check valves are often placed in series for redundancy in case of a leak like this. Don't know, but I'm guessing there are two check valves in series on one high pressure line supplying a pusher, and one of those two valves leaked internally. In that case, the backup valve would have maintained adequate pressure on that line.

[Chris Bergin]

Here's an article I've thrown together:

http://www.nasaspaceflight.com/2014/04/spacex-nasa-realign-launch-eva-scenarios/

[Prober]

? what's changed

Thought Dragon could only be launched every 4 days?

[psloss]

? what's changed

The phasing would be different for a Saturday launch attempt; three days instead of two for Friday.  (See the NASA update that yg1968 posted.)

[psloss]

If Friday doesn't work out, the backup date is Saturday according to the press release above.  Is the weather more favourable on Saturday?

The 45th Weather Squadron didn't post a specific forecast for Saturday in this morning's update; however, we may see that going forward given the decision to target Saturday for a backup launch opportunity.

(Which isn't to say that Friday might not work out.)

Edit, here's the synopsis from the 45th from this morning...I don't see much of a change from Monday evening:

Synoptic Discussion: The front that passed through Central Florida yesterday has stalled in Southern
Florida. The front will remain to the south today and Thursday bringing partly cloudy skies and a chance
of isolated rain showers. In addition, an upper-level feature move through Central Florida on Thursday
and will bring a slight chance of a thunderstorm in the afternoon. Winds will be strong and gusty from the
northeast both days. On Friday, the frontal boundary will move back to the north into Northern Florida as
a wave develops in the Gulf of Mexico. This wave will move through the Florida Peninsula and off to the
northeast by Saturday morning. Thick cloud cover, with periods of rain and isolated thunderstorms are
expected as this system transits through Florida on Friday.
Maximum upper level winds will be 70 knots from the west-northwest at 43,000 feet.

[Norm38]

The Weather Channel forecast for the Cape is thunderstorms on Friday, 80% chance of rain, and showers on Sat, 40% chance of rain.  That's all the resolution there is right now.

[yg1968]

If Friday doesn't work out, the backup date is Saturday according to the press release above.  Is the weather more favourable on Saturday?

It would be 70% go on Saturday (if Friday is scrubbed).

https://twitter.com/flatoday_jdean/status/456487028633260032

[GalacticIntruder]

But there was this tweet.

Jeff Foust ‏@jeff_foust  1h
Gerst: if Dragon doesn't launch on Friday, go with Cygnus launch on May 6.

https://twitter.com/jeff_foust

Ultimatum?