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SpaceX will launch it's first geo satellite Tue 3rd Dec

Albert VDS

By Albert VDS
in Science & Spaceflight

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Kryten

Kryten

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Now my dad thinks SpaceX is inexperinced and bad because the didn't get it after they fixed a problem on the first try- no point in arguing, he just says it's excuses.

To be fair, only checking the rocket after it's had it's launch aborted for the fourth time doesn't exactly seem like a sensible way to operate.

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Albert VDS

Albert VDS

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To be fair, only checking the rocket after it's had it's launch aborted for the fourth time doesn't exactly seem like a sensible way to operate.

It's not like they restarted without doing anything.

They did various tweaks on every try to get it to launch within the safe limits.

They also checked the rocket before this launch windows.

It seems to me you would have a lot of confidence in your rocket to have so many retries.

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Jarnis

Jarnis

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To be fair, only checking the rocket after it's had it's launch aborted for the fourth time doesn't exactly seem like a sensible way to operate.

Nope. They already checked it after first days of aborts. Here is the whole timeline so far;

- First try, extra hold time at t-13min because first stage liquid oxygen vent/pressure relief valve failed to close properly. They held for a bit, cycled back the clock and decided to try again.

- Second try, this bit worked fine but second time around inside 13min final count a ground power supply had out-of-spec voltage and that tripped a hold. They looked at it, decided it was just too conservative limit and recycled to t-13min

- Third try they got fairly far into the count (t-4min) but this time the liquid oxygen valve again suspect as there were off-nominal pressure readings from 1st stage tank.

Additionally there were two glitches with the strongback. When it retracted for the last attempt (only one which got that far) the air conditioning ducts attached to the fairing (to keep satellite cooled) detached earlier than normal due to a tangled line. Not a showstopper. When the third abort was called, the strongback returned to upright position very slowly (some glitch with that).

Between Tuesday and Thursday they took the rocket horizontal, inspected the LOX valve that had caused grief (and I assume, fixed whatever was wrong with the strongback) and were ready to try again.

On Thursday the first attempt took them all the way to ignition of all 9 engines but the computer shut them down immediately as two of them were showing slower-than-expected thrust build-up. Falcon 9 is designed for this; Engines start, computer checks all values are fine and THEN releases the rocket from the pad. Computer said no. Blame the SpaceX MechJeb.

They recycled for a second attempt while engine guys (probably back at the factory) went over all the data from the first attempt. They knew they would not launch if the engine guys were not happy with the data they had. Nothing prevents SpaceX from recycling without inspecting the engines outright - they are designed for re-starts - but it does require that the guys responsible for those engines fully understand what caused the first cutoff. They set the new time at the end of the launch window and everything went fine until ~T-48 secs (just after the point where internal computer takes over the control of the vehicle) but at that point the guys responsible for the engines basically said "nope, we are not comfortable enough with the data we have / the time we had to analyze it. Let's abort and take a close look at the engines to ensure there is nothing wrong".

I don't blame them for electing to be conservative. Would YOU want to go over complex engine telemetry data while a countdown clock is ticking and a satellite insured for $200M is sitting on top of it. Your call may decide if that satellite is toast or not...

The valve that caused them grief on Tuesday *was* inspected and cleared prior to Thursday attempt. There was no reason to inspect the engines prior to the Thursday 1st attempt - they had passed testing at McGregor and had already started up once during hotfire test at the pad. They were considered good. Didn't quite work up to specs set for the flight computer this time around and SpaceX wanted to be sure there is nothing off so we wait for another day...

Edited by Jarnis
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Meithan

Meithan

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Thanks for the rundown, Jarnis.

I feel bad for SpaceX, but to be honest they're doing things the right way. Definitely better be safe than sorry, and you can simply retry in a few days after all has been double- and triple-checked.

What's a bit odd is that they've had 6 successful launch sequences with no issues so far (right? I didn't watch them all), and then suddenly two scrubbed ones. Well, it's true that out of those 6, five were Falcon 9 v1, not v1.1. Could it be something with v1.1?

Also, didn't they do a static fire at least once before Monday's launch? That indicates that the engines were firing normally.

Just bummer, I guess. But good call on aborting. And third's the charm ;).

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Jarnis

Jarnis

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Thanks for the rundown, Jarnis.

I feel bad for SpaceX, but to be honest they're doing things the right way. Definitely better be safe than sorry, and you can simply retry in a few days after all has been double- and triple-checked.

What's a bit odd is that they've had 6 successful launch sequences with no issues so far (right? I didn't watch them all), and then suddenly two scrubbed ones. Well, it's true that out of those 6, five were Falcon 9 v1, not v1.1. Could it be something with v1.1?

You are misremembering.

- Falcon 9 Flight 1 - First try was aborted seconds prior to liftoff (out of range engine parameter, turned out to be sensor failure). Second try worked out.

- Falcon 9 Flight 2 (COTS Demo 1) - Abort with 2:48 on the clock (false telemetry data). Second attempt worked out.

- Falcon 9 Flight 2 (COTS Demo 2) - Abort after engine start (higher than acceptable pressure in engine 5, faulty check valve). Valve replaced, success 3 days later

- Falcon 9 Flight 3 (CRS1) - First try worked. Partial success (loss of one first stage engine 1min 19s into launch) Primary payload OK, secondary (Orbcomm test sat) not deployed to right orbit due to performance lost with the engine loss. Mostly because the initial orbit was so close to ISS orbit and upper stage didn't have quite enough fuel left for NASA-approved safe restart for Orbcomm delivery (NASA didn't want to take any chances)

- Falcon 9 Flight 4 (CRS2) - Couldn't find exact details but I recall this one went up also on the first try, had issues with thrusters (pressurization problem, cycled/"hammered" some valves to clear it)

- Falcon 9 Flight 5 (F9 v1.1, CASSIOPE) - had to repeat their hot fire test once to get everything sorted, actual launch was on the first try - much to the surprise of pretty much everyone. Usually the first launch of a new rocket never goes up on the first try.

So... you most likely are just remembering the last ones (CRS1 and 2, CASSIOPE) which did launch on first try. Not true for every single one :)

This one has been the most temperamental one, I grant you that. New pad structure and still-fairly-new rocket.

Also, didn't they do a static fire at least once before Monday's launch? That indicates that the engines were firing normally.

Just bummer, I guess. But good call on aborting. And third's the charm ;).

Yep. Which is also probably one of the reasons they want to take a look - they worked fine in Hot Fire and now the signature (thrust build-up) was off. "Why?"

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Meithan

Meithan

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You are misremembering.[...]So... you most likely are just remembering the last ones (CRS1 and 2, CASSIOPE) which did launch on first try. Not true for every single one :)

I stand corrected. I think I only watched the v1.1 launch and one of the CRS launches (I might have watched only the second attempt).

So it has been a bumpy road it seems. But I think that, all things considered, they've been very successful so far, and these difficulties are normal for a rocket company that's just starting out (with most hardware designed from the ground up, one must add).

Where are you getting all this info, by the way? Just thorough Google search?

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TwoHedWlf

TwoHedWlf

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I have to agree with everyone that says they're doing it the right way. Being overcautious can be annoying, but a handful of aborts followed by successful launches is embarrassing and a bit expensive. A handful of quick successful launches followed by an explosion would be disastrous.

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Albert VDS

Albert VDS

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Hmm, this is what Elon Musk tweeted 4 hours ago:

All known rocket anomalies resolved. Will spend another day rechecking to be sure. Launch attempt tmrw eve w Wed as backup.

So I guess it's not going to launch today(Dec 2nd) but tomorrow (Tue 3rd).

From Spaceflightnow.com

After cleaning and replacing engine components, SpaceX is gearing up for another try to launch a Falcon 9 rocket Tuesday on a crucial mission to deliver the SES 8 commercial television broadcasting satellite to orbit. Liftoff from Cape Canaveral's Complex 40 launch pad is set for 5:41 p.m. EST (2241 GMT), the opening of an 86-minute launch window.
Edited by Albert VDS
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