Page 4 of 24
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 7:38 am
by TimW
Apparently the destroyed ship was called SN8. How is that irreverent? I don't get it.
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 9:09 am
by Grumble
TimW wrote: ↑Thu Dec 10, 2020 7:38 am
Apparently the destroyed ship was called SN8. How is that irreverent? I don't get it.
Has someone said it is? The next one is SN9, which seems fairly straightforward and not like a jokey naming scheme which SpaceX sometimes do. I thought last night’s test flight was awesome, that “bellyflop” manoeuvre was actually quite graceful to the point I could imagine people being inside one, once they sort out the landing.
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 11:00 am
by Lew Dolby
But SSN8 would be a killer name
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 2:02 pm
by Gfamily
View of the landing - from the landing site.
https://video.twimg.com/ext_tw_video/13 ... mp4?tag=10
You can see the burn weaken at the end
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 3:06 pm
by Grumble
What makes the flame go green?
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 3:09 pm
by Matatouille
The chatter speculation has settled upon copper as the motor eats itself. As the propellent & oxidiser pressures dropped, the engines started combusting bits of itself.
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 3:24 pm
by Grumble
Matatouille wrote: ↑Thu Dec 10, 2020 3:09 pm
The chatter speculation has settled upon copper as the motor eats itself. As the propellent & oxidiser pressures dropped, the engines started combusting bits of itself.
Copper seems an unlikely metal to use in a rocket motor
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 3:48 pm
by insignificant
Grumble wrote: ↑Thu Dec 10, 2020 3:24 pm
Matatouille wrote: ↑Thu Dec 10, 2020 3:09 pm
The chatter speculation has settled upon copper as the motor eats itself. As the propellent & oxidiser pressures dropped, the engines started combusting bits of itself.
Copper seems an unlikely metal to use in a rocket motor
It's used in combustion chamber liners
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 3:55 pm
by Martin Y
At 25 seconds both engines are still running but by 26 seconds the engine on the left has cut out.
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 3:57 pm
by Grumble
insignificant wrote: ↑Thu Dec 10, 2020 3:48 pm
Grumble wrote: ↑Thu Dec 10, 2020 3:24 pm
Matatouille wrote: ↑Thu Dec 10, 2020 3:09 pm
The chatter speculation has settled upon copper as the motor eats itself. As the propellent & oxidiser pressures dropped, the engines started combusting bits of itself.
Copper seems an unlikely metal to use in a rocket motor
It's used in combustion chamber liners
Huh, I’d have thought a refractory metal would be more obvious. Is it used for cooling reasons?
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 4:16 pm
by dyqik
Grumble wrote: ↑Thu Dec 10, 2020 3:57 pm
insignificant wrote: ↑Thu Dec 10, 2020 3:48 pm
Grumble wrote: ↑Thu Dec 10, 2020 3:24 pm
Copper seems an unlikely metal to use in a rocket motor
It's used in combustion chamber liners
Huh, I’d have thought a refractory metal would be more obvious. Is it used for cooling reasons?
The fuel and oxidiser are commonly circulated in pipes around the combustion chamber to cool it before they are fed into the chamber, so yeah, it could be for heat transfer reasons.
And the low fuel/oxidiser pressure would reduce the amount of cooling, and thus lead to overheating. The fuel/oxidiser ratio changing with reduced pressure could also make the combustion run hotter (running a car engine lean can lead to overheating, as another example. There the incoming fuel charge is part of the cooling of the piston and valves - running lean tends to burn valves first).
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 4:30 pm
by Grumble
dyqik wrote: ↑Thu Dec 10, 2020 4:16 pm
Grumble wrote: ↑Thu Dec 10, 2020 3:57 pm
insignificant wrote: ↑Thu Dec 10, 2020 3:48 pm
It's used in combustion chamber liners
Huh, I’d have thought a refractory metal would be more obvious. Is it used for cooling reasons?
The fuel and oxidiser are commonly circulated in pipes around the combustion chamber to cool it before they are fed into the chamber, so yeah, it could be for heat transfer reasons.
And the low fuel/oxidiser pressure would reduce the amount of cooling, and thus lead to overheating. The fuel/oxidiser ratio changing with reduced pressure could also make the combustion run hotter (running a car engine lean can lead to overheating, as another example. There the incoming fuel charge is part of the cooling of the piston and valves - running lean tends to burn valves first).
Ok, cooling the nozzle and preheating the fuel makes sense. Judging by the size of the bang there was plenty of fuel, and probably oxidiser, left so I wonder why pressure dropped.
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 4:34 pm
by Gfamily
Grumble wrote: ↑Thu Dec 10, 2020 4:30 pm
dyqik wrote: ↑Thu Dec 10, 2020 4:16 pm
Grumble wrote: ↑Thu Dec 10, 2020 3:57 pm
Huh, I’d have thought a refractory metal would be more obvious. Is it used for cooling reasons?
The fuel and oxidiser are commonly circulated in pipes around the combustion chamber to cool it before they are fed into the chamber, so yeah, it could be for heat transfer reasons.
And the low fuel/oxidiser pressure would reduce the amount of cooling, and thus lead to overheating. The fuel/oxidiser ratio changing with reduced pressure could also make the combustion run hotter (running a car engine lean can lead to overheating, as another example. There the incoming fuel charge is part of the cooling of the piston and valves - running lean tends to burn valves first).
Ok, cooling the nozzle and preheating the fuel makes sense. Judging by the size of the bang there was plenty of fuel, and probably oxidiser, left so I wonder why pressure dropped.
SN8 has a separate smaller fuel tank for re-entry because the large tank fuel would slosh around.
Also the re-entry fuel has to be kept colder for longer. It may have only been 6 minutes in this case, but normally it would be a lot longer between launch and landing.
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 9:00 pm
by bjn
From my understanding the engine started to run oxidiser rich, as there was a problem with the methane tank being tested. Hot oxygen with nothing to burn decided to the eat the engine instead, including copper alloys. Green flames, not enough thrust to stop it + hard pad = RUD.
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 9:07 pm
by Grumble
bjn wrote: ↑Thu Dec 10, 2020 9:00 pm
From my understanding the engine started to run oxidiser rich, as there was a problem with the methane tank being tested. Hot oxygen with nothing to burn decided to the eat the engine instead, including copper alloys. Green flames, not enough thrust to stop it + hard pad = RUD.
RUD? Even urban dictionary isn’t giving me anything. Thanks for the extra detail though.
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 9:09 pm
by bjn
Rapid unscheduled disassembly. Originally a joke, Space X actually use the term in their communications.
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 9:11 pm
by lpm
A RUD is like air traffic control's MAPE.
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 9:35 pm
by bjn
lpm wrote: ↑Thu Dec 10, 2020 9:11 pm
A RUD is like air traffic control's MAPE.
I’m failing on that one.
Re: Astronomy and Space
Posted: Thu Dec 10, 2020 10:44 pm
by lpm
Mid Air Passenger Exchange. To be avoided.
Re: Astronomy and Space
Posted: Fri Dec 11, 2020 7:25 am
by TimW
Grumble wrote: ↑Thu Dec 10, 2020 9:09 am
TimW wrote: ↑Thu Dec 10, 2020 7:38 am
Apparently the destroyed ship was called SN8. How is that irreverent? I don't get it.
Has someone said it is? The next one is SN9, which seems fairly straightforward and not like a jokey naming scheme which SpaceX sometimes do.
...
Nah, it just seems to be a Musk thing.
The Boring Company, Tesla models, Falcon Heavy, I assume there are more.
Re: Astronomy and Space
Posted: Sun Dec 13, 2020 8:43 am
by plodder
I'd assumed it was a nod to the culture novels?
Re: Astronomy and Space
Posted: Sun Dec 13, 2020 5:42 pm
by dyqik
TimW wrote: ↑Fri Dec 11, 2020 7:25 am
Grumble wrote: ↑Thu Dec 10, 2020 9:09 am
TimW wrote: ↑Thu Dec 10, 2020 7:38 am
Apparently the destroyed ship was called SN8. How is that irreverent? I don't get it.
Has someone said it is? The next one is SN9, which seems fairly straightforward and not like a jokey naming scheme which SpaceX sometimes do.
...
Nah, it just seems to be a Musk thing.
The Boring Company, Tesla models, Falcon Heavy, I assume there are more.
I'd guess that working directly with NASA for crewed vehicles means that they are being more staid about the naming.
Re: Astronomy and Space
Posted: Sun Dec 13, 2020 9:51 pm
by bolo
Or that they are launching satellites for DOD, which is not known for its sense of humor.
Re: Astronomy and Space
Posted: Mon Dec 14, 2020 2:37 am
by dyqik
bolo wrote: ↑Sun Dec 13, 2020 9:51 pm
Or that they are launching satellites for DOD, which is not known for its sense of humor.
It does have some weird named stuff though.
Imagine naming your military bases after traitors who attacked your army...
Re: Astronomy and Space
Posted: Mon Dec 14, 2020 9:30 am
by JQH
dyqik wrote: ↑Mon Dec 14, 2020 2:37 am
bolo wrote: ↑Sun Dec 13, 2020 9:51 pm
Or that they are launching satellites for DOD, which is not known for its sense of humor.
It does have some weird named stuff though.
Imagine naming your military bases after traitors who attacked your army...
To be fair, Bragg did more to ensure the defeat of the Confederacy than most Union generals.