News Changes to the SpaceX BFR rocket.
- Thread starter RGClark
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Linguofreak
Well-known member
As I said, masscons might tweak an object's orbit. That's in fact the only way that you'll ever get a full orbit in the first place.
Some details coming in:
Still need to listen for full context, but TL;DR:
Pad damage not severe, relatively short repair time [they've oficially told NASA as much].
No evidence yet of concrete causing damage to engines or heat shields, but not ruling it out. First 3 engines were turned off on ignition, 30 is minimum for lift-off.
Lost comms at +27s [E: with engine 19 only] due to "energy event", booster kept going, lost TVC at +85s, ship wasn't at a safe point for separation [my interpretation is stage separation was not attempted then, and the cartwheeling was just the TVC loss].
FTS triggered 40 seconds before explosion, took too long to rupture tanks, needs requalification, expects that to be one of the big items for the next launch.
Next flight to repeat the profile, now with the water cooled steel plate [two layers] underneath and faster ignition [Edit: they want 2.5s] to not blast the pad as long. Not decided yet which ship/booster pair fly.
Edit to add not in the Twitter thread:
Pitch over on lift-off not planned and was due to the loss of the engines.
Leading theory in SpaceX is that upon full thrust, sand beneath the concrete was compressed leading to a collapse and subsequent concrete failure.
Don't think acoustics with the plate will be an issue due to how far up the ship and payload are [here's hoping it's not another "we thought the concrete would be enough"].
Vertical tank farm to be replaced with vacuum sealed tanks [presumably not made in-house and matching the current CH4 tanks].
Still need to listen for full context, but TL;DR:
Pad damage not severe, relatively short repair time [they've oficially told NASA as much].
No evidence yet of concrete causing damage to engines or heat shields, but not ruling it out. First 3 engines were turned off on ignition, 30 is minimum for lift-off.
Lost comms at +27s [E: with engine 19 only] due to "energy event", booster kept going, lost TVC at +85s, ship wasn't at a safe point for separation [my interpretation is stage separation was not attempted then, and the cartwheeling was just the TVC loss].
FTS triggered 40 seconds before explosion, took too long to rupture tanks, needs requalification, expects that to be one of the big items for the next launch.
Next flight to repeat the profile, now with the water cooled steel plate [two layers] underneath and faster ignition [Edit: they want 2.5s] to not blast the pad as long. Not decided yet which ship/booster pair fly.
Edit to add not in the Twitter thread:
Pitch over on lift-off not planned and was due to the loss of the engines.
Leading theory in SpaceX is that upon full thrust, sand beneath the concrete was compressed leading to a collapse and subsequent concrete failure.
Don't think acoustics with the plate will be an issue due to how far up the ship and payload are [here's hoping it's not another "we thought the concrete would be enough"].
Vertical tank farm to be replaced with vacuum sealed tanks [presumably not made in-house and matching the current CH4 tanks].
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GLS
Well-known member
All that for 27s of data....
So the engines went kaput on their own (9% failure rate just at ignition), which were uncontained failures as seen by the fire and also the adjacent engines eventually going kaput as well. The fire might also explain the "energy event", which I guess is PR for "massive short-circuit"... all very similar to the N1. I guess the thread title should be changed to "SpaceX N2 rocket".
Thunder Chicken
Fine Threads since 2008
What in the world would they consider "severe"?
Two of the engine bells appear to have been missing. They had better be hoping it was concrete impact damage, otherwise something shook apart that shouldn't have.
Again, if they lost their TVC hydraulics from anything other than concrete impact damage, the rocket, as designed, is tearing itself apart. They really need to verify what is going on. There are several videos showing damage to fairings that are outside of the skirt - if that isn't impact damage than something really weird is going on.
No kidding. I think the only reason the vehicle broke apart was aerodynamic loads when it fell back into denser air. Whoever was charged with pressing the FTS button must have been mashing it repeatedly for all they were worth.
I wonder why they have the farm located where it is relative to the pad and tower. It would seem that putting the tank farm on the opposite side of the tower from the pad would protect it pretty well. Even on a nominal launch those tanks are getting a lot of sound and vibration.
GLS
Well-known member
I think it triggered when needed, but it just was ineffective at ripping the tanks open, and instead just opened a (small) hole. They probably need linear changes along the tanks to really slice them open.
Correction: T+27s loss of comms was only with one of the engines.
Unless he elaborated further in the source, who knows (note: actual phrasing might have been "quite small"). But considering the context, I'd guess whatever involves having to replace the ring or redo foundations/structure. From all that's been said, and all the work going on seemingly comfortably on and around the mount, it looks like they dodged a massive bullet and there's no structural damage. I still think his/their timelines of two months can probably be safely ignored though, the whole new tank farm thing feels like it's being underestimated, on top of the rest.
This was actually the last booster with hydraulic TVC (moving to electric), but that doesn't help much in the context of this launch if hydraulics didn't fail on their own (treating a symptom and not a cause). Agreed that all the falling apart is odd if there were no external forces, though it only takes one engine dying to potentially ruin several other things. He says engine isolation is one of the improvements in the new ones, as B7's protection was simply retrofitted and it's now built-in. Based on how they have operated in the past as far as vehicle assignment, had they chosen to go ahead with finishing the steel plate for another few months I think it's likely they would have just scrapped the current ship and booster pair and worked in parallel to get the next pair done.
I think with the tank farm it might be to do with the actual area they're allowed to build on being relatively tiny, maybe easier access to resupply by being next to the road too. But it wouldn't surprise me if there was a lot of underestimating involved. Even before the flight it seemed like they already regretted the choice of building those tanks, especially after screwing up and wasting time and money with the CH4 ones on account of not complying with storage regulations.
steph
Well-known member
So, no flame trench, but the 'steel plate' thing goes ahead. If the damage to the engines was also caused by sound/shockwaves, it could still mean trouble, if it ends up reflecting them. Would surely be awkward to have Elon admit the need for a flame trench after yet another failure.
Damage not that bad as in 'didn't obliterate the launch tower and pad' , I guess, but I'm amazed that they didn't actually test the FTS before flight, at least on an empty structure. Seems like it was designed in full KSP mode.
Oh well, Falcon Heavy has like 27 engines on the first stage, so it's probably not a question of failure rate/reliability. I wonder how feasible it would be to launch the Starship on an expendable version of the first stage for the Heavy? Perhaps add another booster in a delta config? Of course, they probably wouldn't be launching from there, but at least it's a relatively tried and tested system
Damage not that bad as in 'didn't obliterate the launch tower and pad' , I guess, but I'm amazed that they didn't actually test the FTS before flight, at least on an empty structure. Seems like it was designed in full KSP mode.
Oh well, Falcon Heavy has like 27 engines on the first stage, so it's probably not a question of failure rate/reliability. I wonder how feasible it would be to launch the Starship on an expendable version of the first stage for the Heavy? Perhaps add another booster in a delta config? Of course, they probably wouldn't be launching from there, but at least it's a relatively tried and tested system
GLS
Well-known member
If shockwaves are a problem, then the solution is water.
steph
Well-known member
statisticsnerd
Active member
Have any other rockets had water-cooled steel plates underneath them rather than a flame trench or water deluge system, or is this another case of Elon half assing it and hoping it works?
He describes it as a reverse showerhead, so maybe both. Something like this.Yeah, I guess it remains to be seen whether water-cooled means 'with a water suppression system' or actively cooled like from inside. I wouldn't put it beyond Elon
GLS
Well-known member
Oh, so when they say "plate" they mean just a flat plate on the ground??
I though it would be a tilted plate, like this:
or better for the pad design, this (but with 6 sides):
Thunder Chicken
Fine Threads since 2008
Yeah, just a plate. The problem with the rocket exhaust on the bare concrete is that the heat will cause spalling, and the stagnation pressure of the exhaust is really high. If a crack forms anywhere, the gas pressure can push through it, lift the slab, and you get what happened last week. A plate, cooled sufficiently so it won't actually melt, will prevent the high pressure gas at the stagnation point of the exhaust from exploiting cracks in the concrete. It's still a big plate, and probably needs to be water cooled so it doesn't melt, but it doesn't need to be any more exotic than that. Once the gas is moving parallel to the surface in the radial direction, it will quickly slow and cool sufficiently that the shear and thermal loads on the bare concrete should be tolerable.
Why they couldn't have waited to install such a thing in the first place is baffling. They knew it to be a problem or they wouldn't have been working on it. They needlessly trashed their pad and launch mount and tank farm, and probably compromised their first orbital test. This is worse than bad engineering, it's a 5-year-old screaming "I want to launch my shiny rocket NOW!!!" sort of impatience.
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GLS
Well-known member
Thunder Chicken
Fine Threads since 2008
Here come the lawyers.
/cloudfront-us-east-2.images.arcpublishing.com/reuters/G4W7QL73IBIHTAXGZY64TQPJQQ.jpg)
www.reuters.com
Environmental groups sue US over SpaceX launch license for Texas
Conservation groups sued the Federal Aviation Administration on Monday, challenging its approval of expanded rocket launch operations by Elon Musk's SpaceX next to a national wildlife refuge in South Texas without requiring greater environmental study.
www.reuters.com
Plate corners have started being put together:
In the past few days they've also been putting in new pilings under and around the mount, this time with a full rebar cage (old ones had a single rebar down the middle).
Also Ship 25 is expected to move to the launch site tonight for testing after a few rounds of cryo elsewhere, which might be a hint they've chosen the next sacrificial goat.
While I'm at it, there's been an FTS test of some kind, unclear whether it's a modification or an attempt at reproducing the flight's issue:
In the past few days they've also been putting in new pilings under and around the mount, this time with a full rebar cage (old ones had a single rebar down the middle).
Also Ship 25 is expected to move to the launch site tonight for testing after a few rounds of cryo elsewhere, which might be a hint they've chosen the next sacrificial goat.
While I'm at it, there's been an FTS test of some kind, unclear whether it's a modification or an attempt at reproducing the flight's issue:
Thunder Chicken
Fine Threads since 2008
I'm trying to sort out what this system will look like. There are some renderings of general arrangement here based on parts that have been seen on the site:
There are certainly some parts missing, but I'm wondering about the headers and the ultimate path for the water flow. I'm not convinced that the locations of those headers are correct. The headers seem to be separate tanks capped on both ends, each located on a side of the hexagon. But so far only one has been seen with a inlet pipe, and it's not apparent how the separate headers interconnect, if they do. I hope they have a plan for that big hexagonal hole because if that isn't covered that whole plate assembly is not going to last long.
I am vaguely wondering if they are planning to use pairs of headers something like the water and steam drums in a natural circulation boiler as they look somewhat like them:
en.wikipedia.org
Rocket exhaust turns water to steam under the plate, steam rises into the upper header, and water circulates downwards through downcomers to replace the steam. It would vent a LOT of steam all at once, but if they can keep the plate filled with boiling water then that would effectively control the temperatures. It also might allow them to conserve some water vs dumping a lot of water in an uncontrolled manner in a deluge. Per the environmental mitigation plan if they use water deluge they have to truck municipal water into the site, which is a major consumable which would hinder resetting the pad between launches or scrubs. If they basically make this a low pressure boiler system that is open to atmosphere, they boil away just enough water to keep the pad cool and no more. It might be possible to charge the system with enough water that it can work for several launches between refills. The only problem I see with this arrangement is the water under the plate - if it boils to steam, the steam will be on the side of the hot plate and can potentially superheat and allow that plate to lose strength. The only way to beat that is to somehow push a lot of water through the plate, but it's not clear where the water enters and where it exits. It may be that the water needs to come up the center and push out radially, so maybe they are happy that the OFT excavated the hole for them.
Interesting.
There are certainly some parts missing, but I'm wondering about the headers and the ultimate path for the water flow. I'm not convinced that the locations of those headers are correct. The headers seem to be separate tanks capped on both ends, each located on a side of the hexagon. But so far only one has been seen with a inlet pipe, and it's not apparent how the separate headers interconnect, if they do. I hope they have a plan for that big hexagonal hole because if that isn't covered that whole plate assembly is not going to last long.
I am vaguely wondering if they are planning to use pairs of headers something like the water and steam drums in a natural circulation boiler as they look somewhat like them:
Steam drum - Wikipedia
Rocket exhaust turns water to steam under the plate, steam rises into the upper header, and water circulates downwards through downcomers to replace the steam. It would vent a LOT of steam all at once, but if they can keep the plate filled with boiling water then that would effectively control the temperatures. It also might allow them to conserve some water vs dumping a lot of water in an uncontrolled manner in a deluge. Per the environmental mitigation plan if they use water deluge they have to truck municipal water into the site, which is a major consumable which would hinder resetting the pad between launches or scrubs. If they basically make this a low pressure boiler system that is open to atmosphere, they boil away just enough water to keep the pad cool and no more. It might be possible to charge the system with enough water that it can work for several launches between refills. The only problem I see with this arrangement is the water under the plate - if it boils to steam, the steam will be on the side of the hot plate and can potentially superheat and allow that plate to lose strength. The only way to beat that is to somehow push a lot of water through the plate, but it's not clear where the water enters and where it exits. It may be that the water needs to come up the center and push out radially, so maybe they are happy that the OFT excavated the hole for them.
Interesting.
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