SpaceX reusable launcher (Grasshopper) thread 2


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DocM

Correct. For now anyhow because the info is a tad foggy. If no legs they may try a legless sea landing on CRS-4.

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flyingskippy

Judging from the video, you can clearly see the rocket pitch over before the inflight restart. Which makes me think it is either an actuator with the engines or the fins that got stuck. I find it hard to believe that it was an actual engine problem with over 60 Merlin's launched so far.

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DocM

It wasn't a blowb engine. Can't be more specific. L2 knows, but it's embargoed.

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DocM

Basically a blocked sensor port, a harsh test regime to push the flight envelope, and a less constrained software (to allow such maneuvers) than production F9 launchers.

This sometimes happens at the bleeding edge of aerospace testing.

Garrett Reisman of SpaceX gave a presentation to the Future In-Space Operations (FISO) Working Group on August 27. Some interesting stuff....

Q: What can you tell us about the Texas incident?

A: The test was of our three engine variant of Grasshopper, what we call F-9R Dev. It looks like it was a single point failure that existed on that test article, but does not exist on the Falcon 9. We think it was a failure of a single sensor. Falcon 9 has multiple sensors that its algorithm uses, so the same failure on Falcon 9 would not effect the mission in any way. The fact that Falcon 9 had nine engines, even if it had eight engines it could overcome this issue.

We've been taking a lot of risks with Grasshopper. We're flying this in flight regimes and conops that it was not designed for in an effort to learn. One of those risks bit us. One of the single point failures failed which we knew was a possibility. The failure was such that the flight control could not maintain the lateral boundries of its safety zone and so the flight was terminated intentionally upon exceeding that lateral boundry. That's the most we considered definitively right now.

There was no explosive termination device. Instead, the flight termination sequence is thrust termination combined with some valves that are opened. That caused the destructive sequence you saw. There are populated areas not too far away. We also have our own property and infrastructure that we're trying to protect. We set a certain bound and if we exceed that bound either laterally or vertically then the flight computer initiates the sequence that occurred.

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PaulRocket

Will they try to land the first stage in January during the max drag abort?

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DocM

Someone at SpaceX said they may try. It depends on how the conversion of Vandenberg SLC-4W from Titan II launch pad to multiple landing pads goes, which has begun, and if the stage breaks up after Dragon V2 bugs out.

Speculation: They're keeping the details close, which makes me think they're working on making the first stage survivable from some launch aborts. That may be the envelope expansion Dev-1 was probing, but ran out of capabilities which the full F9 has.

We'll see.

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DocM

It's quite possible. NASA has urgent payloads on CRS-4, space suit batteries and other things. A delay could mess with ISS ops and ripple down the Visiting Vehicle schedule.

Because of this CRS-4 may use AsiaSat 6's F9, meaning no landing legs.

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DocM

Because of a core swap and the rapid turnarounds of the last few launches. This core doesn't have leg specific plumbing etc. for recovery.

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PaulRocket

I know, but it was still expected that they'd try.

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DocM

This flight has cargo ISS needs NOW - the 2 space suit batteries needed for a critical spacewalk. The last thing they need is distractions for tests that can better be done with a legged launcher.

They're also going to have F9R Dev-2 ready for initial tests at McGregor in a few weeks, then it goes to SPA for reuse tests..

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FloatingFatMan

Better in this instance to prove fast turnaround capability and get that gear to the ISS.

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bguy_1986
FloatingFatMan, on 15 Sept 2014 - 16:15, said:

Better in this instance to prove fast turnaround capability and get that gear to the ISS.

Can we call this a fast turn around?  They aren't reusing anything correct?  Fast turn around on the employees part I guess, not on the equipment.

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Beittil

Thats what they need to demonstrate to!

Thats what they need to demonstrate to!

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DocM

Can we call this a fast turn around? They aren't reusing anything correct? Fast turn around on the employees part I guess, not on the equipment.

Fast turnaround of the pad and crew for consecutive launches, one of the fastest in KSC history.

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  • 2 weeks later...
DocM

OK kiddies, now it can be reported that F9R Dev-2 is on the McGregor stage test stand being qualified for flights. Been there for several days.

No idea what the test schedule will be. She may do a few short test hops at McGregor then go to SpacePort America in New Mexico, or she may go straight there. Time will tell.

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PaulRocket

So the first hops should occur in max. 1 month? Maybe before? I think they will try to go up high in New Mexico before the barge/land landing, maybe even simulating a mission.

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DocM

It may only be a single hop to test its systems, then off to SPA.

Given this one came off the line and will use production engines, it should have the redundant systems that would have saved F9R Dev-1.

(F9R Dev-1 used a qualification tank and preproduction Merlin 1D's which lacked redundant sensors)

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DocM

The launch pad at SLC-4E needed a lot of fixing after the CASSIOPE launch. The structural engineers misunderestimated just how big a blast that big, white 224 foot blowtorch would cause. Wicked acoustics.

They lost a lot of plumbing, infrastructure and for certain many of the microphones anywhere near it. Lots of upgrades needed so it wouldn't happen again, especially with Falcon Heavy. Those changes had to be incorporated into the rest of their F9R & FH launch pad designs, and the new F9R / FH test stand at McGregor..

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