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Old 9th December 2020, 03:48 PM   #41
crescent
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Originally Posted by 3point14 View Post
Wow.


It blew up - but not until it was done. And it did the thing with the engines, and going sideways, and belly flopping, then back up right again.

That was crazy.
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Old 9th December 2020, 03:52 PM   #42
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And it 'landed' where they wanted it to.

I suspect that's as much success as they could hope for.

SN9 is just over there, they have a metric ****ton of data to apply to the next go.
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Old 9th December 2020, 04:05 PM   #43
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Fare the well, SN8. You gave us good data, burning fairings, beautiful gimbaling recovering raptors, perfect belly flop, an incredible relight manouevre (2 out of 3 ain't bad) then an epic explosion. Mission absolutely accomplished.
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Old 9th December 2020, 04:15 PM   #44
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Rocket go BOOM!
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Old 9th December 2020, 04:18 PM   #45
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Amazing flight and Elon Musk has tweeted that the problem was low pressure in the LOX header tank that lead to reduced thrust in the final stages, so I imagine a few tweaks will be made, the pad will be cleaned up and SN09 will move out, and any more extensive mods will go into SN10 and 11, got to love rapid prototyping.
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Old 9th December 2020, 06:59 PM   #46
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Is he launching from The Interplanetary House Of Pancakes?
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Old 9th December 2020, 07:34 PM   #47
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Originally Posted by cow_cat View Post
Fare the well, SN8. You gave us good data, burning fairings, beautiful gimbaling recovering raptors, perfect belly flop, an incredible relight manouevre (2 out of 3 ain't bad) then an epic explosion. Mission absolutely accomplished.
Epic explosion FTW.
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Old 9th December 2020, 07:42 PM   #48
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Tweet from Elon Musk

"Successful ascent, switchover to header tanks & precise flap control to landing point!"


"Fuel header tank pressure was low during landing burn, causing touchdown velocity to be high & RUD, but we got all the data we needed! Congrats SpaceX team hell yeah!!"


I will be watching for Scott Manley's take on today's events
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Old 9th December 2020, 08:12 PM   #49
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Chuck Yaeger would not have approved of the landing, but probably not too bad beyond that.

Could someone tell me what was going on with the engine that appeared loose? Was that by design or is that essentially the cause of the problem?

https://youtu.be/ap-BkkrRg-o?t=6601
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Old 9th December 2020, 08:25 PM   #50
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They are on gimbals.
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Old 9th December 2020, 08:28 PM   #51
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Originally Posted by a_unique_person View Post
They are on gimbals.
Thanks!
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Old 9th December 2020, 09:54 PM   #52
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My take on this. Everything worked perfectly up to the last minute, which created a spectacular fireball. Accident? I don't think so.
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Old 9th December 2020, 11:38 PM   #53
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Originally Posted by angrysoba View Post
Chuck Yaeger would not have approved of the landing, but probably not too bad beyond that.

Could someone tell me what was going on with the engine that appeared loose? Was that by design or is that essentially the cause of the problem?

https://youtu.be/ap-BkkrRg-o?t=6601
Here is the reason, as I understand it.

At this stage of development, the methalox powered Raptor engines can only be throttled down to 40% of maximum thrust, but the test was designed to take the rocket to a specific height, pitch it over and let it fall back to earth. Rather than throttle back the engines, they decided to shut down first one, then two then three engines to slow down and eventually stop the ascent

If you watch closely, at about T+1:40, the whole three engines gimbal to the bottom right of the picture just before the first engine (top left) gimbals outwards as it shuts down. This is done in order to reduce the sideways thrust as the two remaining running engines gimbal sharply to the centre to maintain the correct attitude. Same thing happens again at T+3:12 when the second engine shuts down. You can see that both the shut down engine nozzles are gimballed well away from centre to give the running engine a full range of movement.

You can see that all three nozzles have gimballed back to centre by the time the landing burn happened at T+6:30 with all three engines lighting
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Old 10th December 2020, 01:25 AM   #54
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And FYI, here is Scott Manley on today's test, which includes an awesome view from the landing pad camera looking straight up at the rocket bellyflopping and flipping just before it crashes.

https://www.youtube.com/watch?v=egHxiX40eJY
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Old 10th December 2020, 01:42 AM   #55
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So they try, first time, get this to land on the landing pad, right in the middle of the Boca Chita site.
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Old 10th December 2020, 01:53 AM   #56
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Originally Posted by a_unique_person View Post
So they try, first time, get this to land on the landing pad, right in the middle of the Boca Chita site.
Err, no! The launch pad is about two miles ENE of the main site where the control rooms and rocket build centre is

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Last edited by smartcooky; 10th December 2020 at 02:02 AM.
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Old 10th December 2020, 04:14 AM   #57
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Originally Posted by smartcooky View Post
Here is the reason, as I understand it.

At this stage of development, the methalox powered Raptor engines can only be throttled down to 40% of maximum thrust, but the test was designed to take the rocket to a specific height, pitch it over and let it fall back to earth. Rather than throttle back the engines, they decided to shut down first one, then two then three engines to slow down and eventually stop the ascent

If you watch closely, at about T+1:40, the whole three engines gimbal to the bottom right of the picture just before the first engine (top left) gimbals outwards as it shuts down. This is done in order to reduce the sideways thrust as the two remaining running engines gimbal sharply to the centre to maintain the correct attitude. Same thing happens again at T+3:12 when the second engine shuts down. You can see that both the shut down engine nozzles are gimballed well away from centre to give the running engine a full range of movement.

You can see that all three nozzles have gimballed back to centre by the time the landing burn happened at T+6:30 with all three engines lighting
Thanks for that!
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Old 10th December 2020, 05:36 AM   #58
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Originally Posted by Garrison View Post
Amazing flight and Elon Musk has tweeted that the problem was low pressure in the LOX header tank that lead to reduced thrust in the final stages, so I imagine a few tweaks will be made, the pad will be cleaned up and SN09 will move out, and any more extensive mods will go into SN10 and 11, got to love rapid prototyping.
Fuel header, not the LOX header.
The fuel also being the coolant for the engines and the thing that keeps the oxygen from eating them, which is why that last engine was so unhappy.
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Old 10th December 2020, 08:19 AM   #59
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I thought the "bellyflop" thing was just so "meh!" - I mean they were just totally ripping off the "Adama maneuver from Battlestar Galactica:

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(skip to 1:43 for the relevant part)
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Old 10th December 2020, 10:42 AM   #60
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Originally Posted by cjameshuff View Post
Fuel header, not the LOX header.
The fuel also being the coolant for the engines and the thing that keeps the oxygen from eating them, which is why that last engine was so unhappy.
My bad. Important thing is they were able to pin down the problem right away.
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Old 10th December 2020, 10:58 AM   #61
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Originally Posted by Garrison View Post
My bad. Important thing is they were able to pin down the problem right away.
Wouldn't surprise me if they had someone watching a line on a plot dip and going "uh-oh" as it happened.
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Old 10th December 2020, 04:38 PM   #62
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Originally Posted by crescent View Post


It blew up - but not until it was done. And it did the thing with the engines, and going sideways, and belly flopping, then back up right again.

That was crazy.
My reaction was that 7 out of 8 criteria for success were met.
  1. Launch successfully - tick
  2. Climb to target altitude - tick
  3. Transition to bellyflop position - tick
  4. Controlled descent - tick
  5. Transition to upright position - tick
  6. Relight engines - tick
  7. On target to landing site - tick
  8. Land without exploding -
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Old 10th December 2020, 06:43 PM   #63
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What's it like for the people in the Starship when it does the aerobatics?
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Old 10th December 2020, 06:46 PM   #64
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Originally Posted by a_unique_person View Post
What's it like for the people in the Starship when it does the aerobatics?
It's not especially aerobatic. Particularly when you consider that on a genuine mission, the craft would approach the atmosphere pretty much already in the bellyflop position, and the only manoeuvring required is the transition to upright just before landing. It'll be rough, but not too bad.
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Old 10th December 2020, 06:54 PM   #65
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Originally Posted by arthwollipot View Post
My reaction was that 7 out of 8 criteria for success were met.
  1. Launch successfully - tick
  2. Climb to target altitude - tick
  3. Transition to bellyflop position - tick
  4. Controlled descent - tick
  5. Transition to upright position - tick
  6. Relight engines - tick
  7. On target to landing site - tick
  8. Land without exploding -
A couple of other things it did that were important...

1A. Synchronized engine shutdowns and gimbaling to maintain the vehicle attitude during ascent.
1B. Translation while maintaining attitude to prepare for the pitch-over maneuver at target altitude (the vehicle needed to get "downrange" in order to pitch over and glide/skydive back to the landing pad)
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Old 10th December 2020, 06:55 PM   #66
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Originally Posted by smartcooky View Post
A couple of other things it did that were important...

1A. Synchronized engine shutdowns and gimbaling to maintain the vehicle attitude during ascent.
1B. Translation while maintaining attitude to prepare for the pitch-over maneuver at target altitude (the vehicle needed to get "downrange" in order to pitch over and glide/skydive back to the landing pad)
Indeed. So let's say 9/10 criteria for success.
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Old 11th December 2020, 10:51 AM   #67
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SN9 has tipped over in the high bay and is leaning against one corner. Happened about 9:02am Friday morning.

https://twitter.com/BocaChicaGal/sta...24248260993024

Looks like a stand might have buckled.
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Old 11th December 2020, 12:06 PM   #68
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Originally Posted by arthwollipot View Post
My reaction was that 7 out of 8 criteria for success were met.
  1. Launch successfully - tick
  2. Climb to target altitude - tick
  3. Transition to bellyflop position - tick
  4. Controlled descent - tick
  5. Transition to upright position - tick
  6. Relight engines - tick
  7. On target to landing site - tick
  8. Land without exploding -
Not sure I'd give the tick on "relight engines". Yes they relit, but then began consuming themselves.
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Old 11th December 2020, 12:13 PM   #69
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Originally Posted by a_unique_person View Post
What's it like for the people in the Starship when it does the aerobatics?
Probably not nearly as rough as on them as it is when it blows up.
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Old 11th December 2020, 12:35 PM   #70
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Originally Posted by Trebuchet View Post
Not sure I'd give the tick on "relight engines". Yes they relit, but then began consuming themselves.
They got the vehicle oriented and a good way to the pad before they started having issues. The low fuel header pressure issues only had a visible effect a good bit after ignition, and if they were present at ignition the Raptors only deserve extra credit for successfully igniting under suboptimal conditions.
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Old 11th December 2020, 12:46 PM   #71
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Can anyone link to a video where there is NOT an edit in the split second before the explosion?

Ward
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Old 11th December 2020, 01:00 PM   #72
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Originally Posted by Trebuchet View Post
Not sure I'd give the tick on "relight engines". Yes they relit, but then began consuming themselves.
They re-lit. They just had burned a bit engine rich.
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Old 11th December 2020, 01:27 PM   #73
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Originally Posted by smartcooky View Post
SN9 has tipped over in the high bay and is leaning against one corner. Happened about 9:02am Friday morning.

https://twitter.com/BocaChicaGal/sta...24248260993024

Looks like a stand might have buckled.
Well damn, but its stainless steel so replacing parts should be straightforward, unlike the Orion capsule where a PDU failure could take months to repair:

https://www.theverge.com/2020/11/30/...lure-artemis-i
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Old 11th December 2020, 04:34 PM   #74
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Bad news is the tilt damaged a fin, good news a replacement fin arrived within a few hours.
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Old 11th December 2020, 05:11 PM   #75
smartcooky
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Originally Posted by Trebuchet View Post
Not sure I'd give the tick on "relight engines". Yes they relit, but then began consuming themselves.
That was because of fuel starvation due to low pressure in the header tank, not a problem with the engine.

Lack of fuel causes the engines to run "Oxidizer Rich". AIUI (no doubt Jay will correct me if I'm wrong) when that happens, the oxygen will be chemically reacting with the best available candidate. Since the Raptor combustion chamber and nozzle contains copper, it will combine with that. This will cause the chamber temperature to spike, and since pure oxygen is very corrosive at high temperatures, the copper gets rapidly oxidized away, causing the bright green flame we saw.

The resulting sudden drop in thrust meant that the rocket fell too quickly to get fully upright and land safely.
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Old 11th December 2020, 05:21 PM   #76
cjameshuff
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Originally Posted by smartcooky View Post
That was because of fuel starvation due to low pressure in the header tank, not a problem with the engine.

Lack of fuel causes the engines to run "Oxidizer Rich". AIUI (no doubt Jay will correct me if I'm wrong) when that happens, the oxygen will be chemically reacting with the best available candidate. Since the Raptor combustion chamber and nozzle contains copper, it will combine with that. This will cause the chamber temperature to spike, and since pure oxygen is very corrosive at high temperatures, the copper gets rapidly oxidized away, causing the bright green flame we saw.

The resulting sudden drop in thrust meant that the rocket fell too quickly to get fully upright and land safely.
The fuel's also the coolant that keeps them from melting under normal operating conditions.
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Old 11th December 2020, 06:46 PM   #77
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Originally Posted by cjameshuff View Post
The fuel's also the coolant that keeps them from melting under normal operating conditions.
Yes, I forgot that. The lack of liquid methane flow was probably the key factor in the engine temperature spiking.
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Old 26th December 2020, 07:42 AM   #78
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Short video covering the fates of SN01-SN08:

https://www.youtube.com/watch?v=G7Ik089A5nc

From cryo tank test to 12.5km flight test took 10 months.
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Old 26th December 2020, 11:04 AM   #79
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I note that S/N Nine, or Snine as I think of it, has had engines installed without first doing the pressure test with artificial thrust simulator. Definitely moving right along.
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Old 26th December 2020, 04:48 PM   #80
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Originally Posted by smartcooky View Post
SSTO might be possible, but I doubt such a vehicle would or could deliver a significant payload to orbit.
SSTO is already possible. It is just so uneconomical with current tech that no one bothers with it.
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