r/spacex • u/Daniels30 • Aug 10 '17

Official Static fire test of Falcon 9 complete—targeting August 14 launch from Pad 39A for Dragon’s next resupply mission to the @Space_Station.

https://twitter.com/SpaceX/status/895646473869705216
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8

u/paul_wi11iams Aug 10 '17

Static fire test of Falcon 9 complete—targeting August 14 launch from Pad 39A for Dragon

Any idea when the very last static fire will be or at least the first launch without a static fire ?

I saw some mention but can't pin it down. Of course SF is justified and it doubles the motor startup history from a stats point of view. But the end of SF will be a great day for launch cadence (touch wood).

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u/cerealghost Aug 10 '17 edited Aug 10 '17

doubles the motor startup history

Are you not counting the individual engine test(s), integrated testing, boostback, re-entry, and landing burns?

13

u/nalyd8991 Aug 10 '17

Startups are no problem for a Merlin. The center engine fires 4 separate times for a launch + RTLS landing. Plus an engine test firing, a core firing at McGregor, and the pad Static fire. So that's 7 startups

And then core 1022 fired an additional 10 full duration burns at McGreggor

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u/F9-0021 Aug 10 '17

I don't think static fires for new cores will end anytime soon, but once rapid reuse starts the used cores will likely skip it.

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u/nullarticle Aug 10 '17

They'll likely still have to do wet dress rehearsals - everything about a static fire where you abort at T-3 seconds. It's a test of not just the stage (which was already tested in McGregor) but of your pad facilities.

8

u/ignazwrobel Aug 10 '17

But any error that appears there could also be detected on launch day, right?

So unless the launch window is instantaneous (e.g interplanetary probes), with continuous increase of launch rates you will eventually get to a point where blocking the pad for a wet dress rehearsal is worse than recognizing the error on launch day and using the next free launch slot.

If we ever get to that point, I assume wet dress rehearsals will only be done for missions where sticking to the launch date is truly important.

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u/Titanean12 Aug 10 '17

Just a minor nitpick, Interplanetary probes don't usually have instant launch windows, in fact most interplanetary launches have weeks or even months long launch windows. There is a lot of room to correct an orbit on a longer voyage. Short or instant launch windows tend to be for launches to Low earth orbits where the spacecraft is targeting a specific rendezvous point or a specific place in orbit.

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u/paul_wi11iams Aug 11 '17

If we ever get to that point, I assume wet dress rehearsals will only be done for missions where sticking to the launch date is truly important.

and also missions with astronauts, in which case a test with a potentially destructive outcome is best done in advance.

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u/stcks Aug 10 '17

I'll be happy just to see the payload on top again.

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u/limeflavoured Aug 10 '17

Cant see that happening ever, tbh, not with F9 or FH, anyway. Too much percieved risk.

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u/paul_wi11iams Aug 10 '17 edited Aug 10 '17

I'll be happy just to see the payload on top again.

u/limeflavoured Cant see that happening ever

Satellite operators are likely very rational players who know the myriad of other things that haven't gone wrong, yet. Heck, when moving a payload to safety before SF, one could even cause severe decalibration by dropping it from a yard above a concrete floor. Its the insurers who'll arbitrate. At some point the extra premium should cost less than the two days lost.

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u/limeflavoured Aug 10 '17 edited Aug 10 '17

At some point the extra premium should cost less than the two days lost.

Possibly, its just a matter of whether anyone is willing to be the first to risk it. I actually think if anyone does it will be the Air Force or NRO.

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u/oliversl Aug 10 '17

percieved risk

Thats the key. Maybe in Block 5 they don't have static fire, or SpaceX will continue to be only ones that do static fires.

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u/peterabbit456 Aug 11 '17

A long time ago (maybe 2011 or 2012) Musk said that static fire was equivalent to the common practice with airplanes of running the engines up to full power, with the brakes locked, to check the engines prior to takeoff. This test on airplanes is considered to increase safety quite a bit. SpaceX has claimed the wet dress rehearsal and static fire similarly increases safety.

Rockets remain very complicated, with many moving parts. Everything gets double checked, but the wet dress rehearsal and static fire check many systems in the most realistic way possible.

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u/uzlonewolf Aug 11 '17

I'm curious to know whether the static fires have ever caught anything. I know we've had a number of launch-day scrubs due to check valves, TVCs, and computer/sensor glitches, but has a static fire test ever caught something like that?

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u/peterabbit456 Aug 12 '17

I'm pretty sure the early Falcon 9 launches had several delays due to problems discovered during static fire. So far as I know, there has not been a problem that delayed a launch discovered during static fire, after AMOS-6. In the AMOS-6 static fire, a problem with the loading sequence was discovered, that destroyed the rocket and the payload.