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News SpaceX heavy-lift vehicles: Launch Thread

Marc said:
it's possible they went through more relight cycles than expected or it took a bit more work to get the rockets lit.
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The live video stream seemed to show them unsuccessfully attempting to light the other two engines on the core stage at about the time that the two boosters landed.
 
Marc said:
it's possible they went through more relight cycles than expected or it took a bit more work to get the rockets lit.
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While I was being facetious, for someone unfamiliar with building rockets like me, it sounds like a strange failure mode, somewhat like the landing that failed due to insufficient hydraulic fluid. I expected the rocket to blow up mid-launch because of unexpected stress due to the interactions of 27 engines in the real world that were hard to model precisely. Not that they would miscalculate the amount of fluid the rocket would use. How did they get that model so wrong that the actual needed TEA-TEB exceeded even the tolerance they put in extra, yet they got the insanely difficult 27 engine stress thing right? Accumulated errors in stress modelling should add up to a boom, accumulated errors in fluid use estimates – to a zero. :ouch: And I'm certain they did not overlook this part... or anything for that matter, otherwise they wouldn't have gotten such picture perfect launch and two landings.

I suspect the Heavy may use a lot more ignition fluid than the Falcon 9. They were throttling the engines up and down the whole time (John Insprucker reported so on webcast, I didn't watch the plumes), which I presume is because the rocket has a lot harder time to handle those engines at the same time at full thrust, while simultaneously having to minimise fuel economy before/after booster separation while maximising delta-V gained by the extra boosters. It's how Heavy makes everything more complicated. But I also assume throttling up and down does not use ignition fluid in itself (or does it?), but perhaps they also turned some engines off on the centre core along with it?

If they weren't turning engines on and off, though, the amount used should be close to what was used by a Falcon 9 launch, so no much more ignition fluid. And even though they were testing new landing mode with three engines, they did get data (and success) with that one right before that:

YellowSubmarine said:
In preparation for Falcon Heavy launch on 6th, Elon Musk presents a new epic failure:

Falcon 9 rocket fails to break apart, explode and disintegrate as planned, making an unintended successful soft landing :rommie:
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Where did that ignition fluid go, and how did they not know it would go there?
 
The outer two engines on the core did ignite but they then appeared to flame out for some unknown reason - perhaps turbulent air flow from the reentry. There probably just wasn't enought ignition fuel for yet another restart. They do throttle the engines at various stages such as around max Q. All the engines are out at time of reentry. They just need to fire up three again (centre and two outer) on the core to slow down from terminal velocity.
 
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Asbo Zaprudder said:
The outer two engines on the core did ignite but they then appeared to flame out for some unknown reason - perhaps turbulent air flow from the reentry. There probably just wasn't enought ignition fuel for yet another restart. They do throttle the engines at various stages such as around max Q. All the engines are out at time of reentry. They just need to fire up three again (centre and two outer) on the core to slow down from terminal velocity.
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Does the fluid actually cause ignition when combined with the rocket fuel or is it used a fuel source for a small flame in the way you have a pilot light on your gas heater or hot water system?
 
Marc said:
Does the fluid actually cause ignition when combined with the rocket fuel or is it used a fuel source for a small flame in the way you have a pilot light on your gas heater or hot water system?
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For the Merlin engines used on the heavy, the TEA-TEB is used to ignite the RP1/LOX mixture directly. (The turbopumps are driven by burning a small amount of RP1/LOX and the cooler exhaust gases used to protect the engine bell somewhat from the main combustion.) However, if the timing is incorrect, my understanding is that the ignition is either too early and fails to be sustainable or too late and causes a violent explosion that could damage the bell.

https://space.stackexchange.com/questions/13953/how-do-the-falcon-9-engines-re-ignite
 
Marc said:
it's always the little things.

SpaceX have determined the cause of the landing failure for the Falcon X core last week.

It had run out of ingition fluid and as unable to re-ignite the engines.

http://www.latimes.com/business/la-fi-spacex-falcon-heavy-core-20180212-story.html

And all that work for the simultaneous landing of the other two boosters and they won't be used again.
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The side cores were already reused, once, and they aren't the latest iteration of the F9 1st stage, so they were never going to be used again. The grid fins are titanium. they'll get reused or recycled. The center core was not going to be reused either but it was pretty clear they wanted the grid fins off it too.
 
XCV330 said:
The side cores were already reused, once, and they aren't the latest iteration of the F9 1st stage, so they were never going to be used again. The grid fins are titanium. they'll get reused or recycled. The center core was not going to be reused either but it was pretty clear they wanted the grid fins off it too.
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I thought I read that the core stage didn't have any expensive titanium grid fins which is perhaps why it would need three engines to land - the terminal velocity with fins should have been about the same as the boosters otherwise. I might be wrong though.
 
Asbo Zaprudder said:
I thought I read that the core stage didn't have any expensive titanium grid fins which is perhaps why it would need three engines to land - the terminal velocity with fins should have been about the same as the boosters otherwise. I might be wrong though.
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Not sure. It should have the grid fins, though.
 
Asbo Zaprudder said:
I thought I read that the core stage didn't have any expensive titanium grid fins which is perhaps why it would need three engines to land - the terminal velocity with fins should have been about the same as the boosters otherwise.
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I thought the same when I listened to Elon's press conference, but then I seemed to notice grid fins on the centre core when I rewatched the webcast. Not sure what were of their price or what they were made of, obviously. :p The earlier 3-engine landing test made me think the 3-engine landing is done for some other reason.
 
Yeah, Elon said there were no (expensive, machined titanium) grid fins on the core stage worth recovering. Perhaps they were experimenting with a three engine restart to reduce the expense of the fins.
 
http://www.whereisroadster.com/

If you want to keep track of Starman and the car..
At this very moment the stats are:
The current location is 2,102,739 miles (3,384,032 km, 0.023 AU) from Earth, moving away from Earth at a speed of 6,753 miles/hour (10,868 km/hour, 3.02 km/s).

The car is 138,301,171 miles (222,574,229 km, 1.488 AU) from Mars, moving toward the planet at a speed of 43,134 miles/hour (69,417 km/hour, 19.28 km/s).

The car exceeded its 36,000 mile warranty 580.7 times while driving around the Sun, (20,905,990 miles, 33,644,941 km, 0.22 AU) moving at a speed of 73,789 miles/hour (118,752 km/hour, 32.99 km/s). It has achieved a fuel economy of 165.9 miles per gallon (70.5 km/liter), assuming 126,000 gallons of fuel.
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Scott Manley explains suicide burns and why using three engines to slow down is more efficient:
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YellowSubmarine said:
How can you not get the ignition fluid right? Launch and landing 101 is not rocket science.
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I really didn't think they'd get the core back--but this looks an easy fix....

Ziggy approves

DVZkPj-WkAAwwPN.jpg
 
 
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Not a Falcon-Heavy launch, but if schedule holds, a Falcon 9 is about to make it's 3rd flight (first time they've the first stage more than once), flying from the California launch pad. Should be launching in about 40 minutes or so
 
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