Astronomy and Space

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lpm
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Re: Astronomy and Space

Post by lpm » Sun Apr 30, 2023 10:50 pm

Surely copy and paste is the fastest method? If someone else uses a million gallons of water, just copy them. All it needs is a massive tank.

Though it would mean the turtles get broiled in a rolling wave of steam, rather than bombarded with concrete.
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Re: Astronomy and Space

Post by Pishwish » Sun Apr 30, 2023 11:43 pm

Water deluge systems are used for cooling and for sound suppression. I think there is a water system planned, but I read somewhere it is difficult to get permits to dump huge amounts of freshwater in a in a salt-marsh ecosystem. Hence the desire for a simpler approach.

From that transcript:
So we were going to be putting down a very strong steel sandwich that is basically a water jacketed sandwich.
It's two layers of very thick plate steel that are also perforated on the upper side so that you have what is basically a massive, super strong steel showerhead pointing up.
And then the water pressure coming out of there has to exceed the pressure that the engine's thrust is exerting on the steel plate beneath the launch stand.
... The important thing is that you have a regeneratively cooled...
Like, wherever the flame is hitting, that that is regeneratively and evaporatively cooled.
So what you'll see is quite a big steam cloud, but not a dust cloud.
...
The acoustic environment is worse [than a flame trench] with a flat plate, as you might imagine.
But the payload is... like 400 feet away from where the plume is impinging.
So it's so far away that the acoustics are not actually not that bad in the payload fairing....
Yeah, so it can be done either way, but this is one way.
And we're pretty confident this will work.
And we're going to extend the steel out beyond just underneath the rocket, because we want to make sure we don't sort of dig up concrete elsewhere.
And then we're going to connect the load of the massive steel sandwich underneath the launch pad into the launch mount legs.
So it can take that load in tension as well as compression.

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Re: Astronomy and Space

Post by Martin_B » Mon May 01, 2023 5:41 am

Pishwish wrote:
Sun Apr 30, 2023 11:43 pm
Water deluge systems are used for cooling and for sound suppression. I think there is a water system planned, but I read somewhere it is difficult to get permits to dump huge amounts of freshwater in a in a salt-marsh ecosystem. Hence the desire for a simpler approach.
If the problem was dumping fresh water into a salt-water eco-system, then there's an easy fix for that - add salt to the water deluge tank.
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Re: Astronomy and Space

Post by jimbob » Mon May 01, 2023 6:19 am

Pishwish wrote:
Sun Apr 30, 2023 11:43 pm
Water deluge systems are used for cooling and for sound suppression. I think there is a water system planned, but I read somewhere it is difficult to get permits to dump huge amounts of freshwater in a in a salt-marsh ecosystem. Hence the desire for a simpler approach.

From that transcript:
So we were going to be putting down a very strong steel sandwich that is basically a water jacketed sandwich.
It's two layers of very thick plate steel that are also perforated on the upper side so that you have what is basically a massive, super strong steel showerhead pointing up.
And then the water pressure coming out of there has to exceed the pressure that the engine's thrust is exerting on the steel plate beneath the launch stand.
... The important thing is that you have a regeneratively cooled...
Like, wherever the flame is hitting, that that is regeneratively and evaporatively cooled.
So what you'll see is quite a big steam cloud, but not a dust cloud.
...
The acoustic environment is worse [than a flame trench] with a flat plate, as you might imagine.
But the payload is... like 400 feet away from where the plume is impinging.
So it's so far away that the acoustics are not actually not that bad in the payload fairing....
Yeah, so it can be done either way, but this is one way.
And we're pretty confident this will work.
And we're going to extend the steel out beyond just underneath the rocket, because we want to make sure we don't sort of dig up concrete elsewhere.
And then we're going to connect the load of the massive steel sandwich underneath the launch pad into the launch mount legs.
So it can take that load in tension as well as compression.
Maybe that was the sort of thing that should have been considered when choosing the site.
Have you considered stupidity as an explanation

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Re: Astronomy and Space

Post by jimbob » Mon May 01, 2023 6:30 am

Pishwish wrote:
Sun Apr 30, 2023 10:42 pm
I wouldn't trust any video by "common sense skeptic," he makes videos with bad-faith arguments written to please an anti-elon audience. This video isn't as bad as his earlier ones on Starship, but why waste time on an unreliable source? (Same goes for any video by Thunderf00t on SpaceX).
Speaking of unreliable sources, Musk gave an interview that I haven't watched but has been summarized in a twitter thread, these are some excerpts:
"The vehicle's structural margins appear to be better than we expected, as we can tell from the vehicle actually doing somersaults towards the end and still staying intact." ..."The longest item on that is probably requalification of the flight termination system ... it took way too long to rupture the tanks."
Time for AFTS to kick in "was pretty long," about "40 seconds-ish."
..."There were 3 engines that we chose not to start," so that's why Super Heavy booster lifted off with 30 engines, "which is the minimum number of engines."
The 3 engines "didn't explode," but just were not "healthy enough to bring them to full thrust so they were shut down" ."Rocket kept going through T+62 seconds" with the engines continuing to run. Lost thrust vector control at T+85 seconds.
"It was actually good to get this vehicle off the ground because we've made so many improvements" in Super Heavy Booster 9 "and beyond."

"Really just needed to fly this vehicle and then move on to the much improved booster."
"Got pretty close to stage separation ... if we had maintained thrust vector control and throttled up, which we should have ... then we would have made it to staging."
"Definitely don't" expect lunar Starship (under the HLS project) to be the longest lead item for the Artemis III mission.

"We will be the first thing to really be" ready.
there is a transcript halfway down this forum page, the flight termination system problem is more evident:
The longest lead item on that is probably re-qualification of the flight termination system.
Because we did initiate the flight termination system, but it was not enough to...
it took way too long to rupture the tanks.
So we need a basically a much...
we need more detonation cord to lines up the tanks at altitude and ensure that basically the rocket explodes immediately if there's a flight termination is necessary.
So re-qualification of the...
I'm just guessing here that re-qualification of the much longer detonation cord to lines up the rocket in a bad situation is probably the long lead item.
What was the time lag? It was pretty long.
I think it was on the order of 40 seconds-ish.
So quite long.
The yeah, so now the rocket was in a relatively low air density situation.
So the aerodynamic forces that I was experiencing were would be less than if it was at a lower, you know, lower down in the atmosphere.
And so the aerodynamic forces would have, I think, at lower point in the atmosphere aided in the destruction of the vehicle.
And in fact that's kind of what happened when the vehicle got to a low enough altitude that the atmospheric density was enough to cause structural failure.
But I mean this is obviously something that we want to make super sure is solid before proceeding with the next flight.
He might be, but several of the observations in his video - like the FTS not working properly have now been confirmed by Musk, and that is certainly against the impression given by SpaceX initially. Also he did predict that the pad would blast itself to rubble.
Have you considered stupidity as an explanation

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Re: Astronomy and Space

Post by bjn » Mon May 01, 2023 7:35 am

It’s not as if building launch pads isn’t a solved problem, or am I missing something?

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Re: Astronomy and Space

Post by jimbob » Mon May 01, 2023 8:56 am

bjn wrote:
Mon May 01, 2023 7:35 am
It’s not as if building launch pads isn’t a solved problem, or am I missing something?
That's the thing, from my understanding.

It *would* be cheaper to avoid having to build the flame trench and/or water deluge system (especially if the water deluge system is going to have issues with the fact that Musk chose to site this near a protected wetland, and the environmental mitigations might take time.

But Musk himself said in 2020 that it might have been a mistake to plan on not using a flame diverter.

So it's aggressive engineering for its own sake as far as I can see.
Have you considered stupidity as an explanation

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Re: Astronomy and Space

Post by bjn » Mon May 01, 2023 9:03 am

I believe that they couldn’t build a flame trench etc… in the Boca Chica site because there is a nature reserve with endangered species literally right next to the launch pad. So the choice of the site in Texas basically made that impossible.

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Re: Astronomy and Space

Post by bjn » Mon May 01, 2023 9:09 am

As for near anything Musk says, I wouldn’t believe a word without corroborating evidence. Why were three engines not working well enough to throttle up? Possibly because they were whacked by huge chunks of concrete that are clearly flying about? And in the video there are clearly many more engines dying as the rocket ascended, indicate by various explosions or green flames shooting as they ate themselves.

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Re: Astronomy and Space

Post by jimbob » Mon May 01, 2023 9:19 am

bjn wrote:
Mon May 01, 2023 9:03 am
I believe that they couldn’t build a flame trench etc… in the Boca Chica site because there is a nature reserve with endangered species literally right next to the launch pad. So the choice of the site in Texas basically made that impossible.

Exactly. Although I think that was the water deluge system.

A bit like deciding to build a thermal power plant far from an adequate water supply.



jimbob wrote:
Mon May 01, 2023 6:19 am
Pishwish wrote:
Sun Apr 30, 2023 11:43 pm
Water deluge systems are used for cooling and for sound suppression. I think there is a water system planned, but I read somewhere it is difficult to get permits to dump huge amounts of freshwater in a in a salt-marsh ecosystem. Hence the desire for a simpler approach.

From that transcript:
So we were going to be putting down a very strong steel sandwich that is basically a water jacketed sandwich.
It's two layers of very thick plate steel that are also perforated on the upper side so that you have what is basically a massive, super strong steel showerhead pointing up.
And then the water pressure coming out of there has to exceed the pressure that the engine's thrust is exerting on the steel plate beneath the launch stand.
... The important thing is that you have a regeneratively cooled...
Like, wherever the flame is hitting, that that is regeneratively and evaporatively cooled.
So what you'll see is quite a big steam cloud, but not a dust cloud.
...
The acoustic environment is worse [than a flame trench] with a flat plate, as you might imagine.
But the payload is... like 400 feet away from where the plume is impinging.
So it's so far away that the acoustics are not actually not that bad in the payload fairing....
Yeah, so it can be done either way, but this is one way.
And we're pretty confident this will work.
And we're going to extend the steel out beyond just underneath the rocket, because we want to make sure we don't sort of dig up concrete elsewhere.
And then we're going to connect the load of the massive steel sandwich underneath the launch pad into the launch mount legs.
So it can take that load in tension as well as compression.
Maybe that was the sort of thing that should have been considered when choosing the site.
Have you considered stupidity as an explanation

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Re: Astronomy and Space

Post by Pishwish » Mon May 01, 2023 2:01 pm

You really don't have much choice when picking suitable launch sites. Since you pretty much can't fly over land, your ideal site would be a massive area of uninhabited Atlantic coast as far south as possible but not too far from infrastructure, workers, etc. Since people like to live near the coast, you are pretty much left with swampland, and you would not have the resources, lax regulation, and power that the military (and then NASA) had when acquiring land and building at Cape Canaveral (on land that would, and sort of still is, a nature reserve). Also, Boca Chica is a test site (it was originally planned to be a launch site for Falcon rockets, and I think they are limited to about a dozen launches a year), so why would you invest in a billion dollar pad for such a small number of launches? However, using the results of an underpowered static fire as the basis of an assumption that the pad would survive a single launch was foolish.

MartinB:
If the problem was dumping fresh water into a salt-water eco-system, then there's an easy fix for that - add salt to the water deluge tank.
I think you could add salt to the deluge tank, particularly if you do not expect to reuse the rocket or do many static fires, but spraying salt water on hot metal is probably not a good idea.

Jimbob:
He might be, but several of the observations in his video - like the FTS not working properly have now been confirmed by Musk, and that is certainly against the impression given by SpaceX initially. Also he did predict that the pad would blast itself to rubble.
Except CSS claimed that SpaceX and the FAA lied when they say the FTS was used (it does seem to have been used, it did not work as fast as it should have done. And even then, a layman's expectation of what an FTS is supposed to do may not be correct. It is supposed to "Disperse any liquid propellant, whether by rupturing the propellant tank or other equivalent method, and initiate burning of any toxic liquid propellant...A Flight termination system must not cause any solid or liquid propellant to detonate"*
Look you can watch this guy's videos if you want, they've got a bit better (he's learned more about spaceflight, so his misrepresentations are harder to rebut), but you're really watching the Fox News of spaceflight.

*fireball good, detonation bad.

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Re: Astronomy and Space

Post by dyqik » Mon May 01, 2023 2:09 pm

Pishwish wrote:
Mon May 01, 2023 2:01 pm
You really don't have much choice when picking suitable launch sites. Since you pretty much can't fly over land, your ideal site would be a massive area of uninhabited Atlantic coast as far south as possible but not too far from infrastructure, workers, etc. Since people like to live near the coast, you are pretty much left with swampland, and you would not have the resources, lax regulation, and power that the military (and then NASA) had when acquiring land and building at Cape Canaveral (on land that would, and sort of still is, a nature reserve). Also, Boca Chica is a test site (it was originally planned to be a launch site for Falcon rockets, and I think they are limited to about a dozen launches a year), so why would you invest in a billion dollar pad for such a small number of launches? However, using the results of an underpowered static fire as the basis of an assumption that the pad would survive a single launch was foolish.
I suspect that the reason Elmu was looking for a site in Texas was likely political, rather than technical. He's been cozying up to the Republicans in Texas for a while now, across all his businesses.

The reason you'd invest in a billion dollar pad is so that your expensive space vehicle design isn't grounded by the FAA when you redistribute the cheap launch pad over the surrounding publicly accessible areas.

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Re: Astronomy and Space

Post by Pishwish » Mon May 01, 2023 2:25 pm

Definitely political, and also the attraction of less regulation (at the time, SpaceX was facing restrictions on launching out of Florida that seem to have resolved themselves).

You'd spend a billion dollars on a test pad? That's absurd. And space vehicles get "grounded" by the FAA all the time. In the last couple of years, Astra, Firefly, Virgin Orbit, Blue Origin have all had this happen.

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Re: Astronomy and Space

Post by EACLucifer » Mon May 01, 2023 2:34 pm

Pishwish wrote:
Mon May 01, 2023 2:25 pm
Definitely political, and also the attraction of less regulation (at the time, SpaceX was facing restrictions on launching out of Florida that seem to have resolved themselves).

You'd spend a billion dollars on a test pad? That's absurd.
How much did they spend on a rocket that was destroyed by an inadequate pad? How much would it had cost them if it had done what some of the N-1 launches did, and lost control so badly it came down some distance away and exploded? When you cut corners, it can cost you much more than you saved by cutting the corner.

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Re: Astronomy and Space

Post by dyqik » Mon May 01, 2023 4:34 pm

Pishwish wrote:
Mon May 01, 2023 2:25 pm
You'd spend a billion dollars on a test launch pad? That's absurd. And space vehicles get "grounded" by the FAA all the time. In the last couple of years, Astra, Firefly, Virgin Orbit, Blue Origin have all had this happen.
Yes, when the thing you are launching off of it costs more than a billion dollars for one launch, and the billion dollar launch pad can launch many of them.

I'm currently working on a billion dollar NASA satellite proposal, which does not include the cost of the launch.

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Re: Astronomy and Space

Post by Pishwish » Mon May 01, 2023 9:01 pm

I don't know why you changed what I wrote. Boca Chica will launch test rockets for the forseeable future. It will not be launching rockets with billion dollar payloads anytime soon.

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Re: Astronomy and Space

Post by dyqik » Mon May 01, 2023 9:04 pm

Pishwish wrote:
Mon May 01, 2023 9:01 pm
I don't know why you changed what I wrote. Boca Chica will launch test rockets for the forseeable future. It will not be launching rockets with billion dollar payloads anytime soon.
I changed it for my context. Either way, Starship is a multi-billion dollar program, and the entire program was put at risk by trying shortcut the launch pad.

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Re: Astronomy and Space

Post by Martin_B » Tue May 02, 2023 12:24 am

Pishwish wrote:
Mon May 01, 2023 2:01 pm
MartinB:
If the problem was dumping fresh water into a salt-water eco-system, then there's an easy fix for that - add salt to the water deluge tank.
I think you could add salt to the deluge tank, particularly if you do not expect to reuse the rocket or do many static fires, but spraying salt water on hot metal is probably not a good idea.
On the contrary, it's used throughout my industry (offshore oil and gas) to protect infrastructure. It only gets used for a short period of time, so there aren't issues with long-term use (corrosion, salt deposition, etc), and is very effective at turning jet fires (which eat through steel and concrete at alarming rates) into a manageable situation. And the idea is that the water spray gets turned on first, so it's the rocket exhaust hitting wet metal, not water hitting hot metal.

You'd have to try and match the salt levels to the brackish levels in the swamp (ie, likely to be lower salt content than seawater, which my industry uses), and you'd still have to manage the influx of large quantities of this salty water into the swamp, but I'd argue that the environmental impact is better than large chunks of concrete and dust being blown into the area.
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Re: Astronomy and Space

Post by Grumble » Tue May 02, 2023 5:30 am

Martin_B wrote:
Tue May 02, 2023 12:24 am
Pishwish wrote:
Mon May 01, 2023 2:01 pm
MartinB:
If the problem was dumping fresh water into a salt-water eco-system, then there's an easy fix for that - add salt to the water deluge tank.
I think you could add salt to the deluge tank, particularly if you do not expect to reuse the rocket or do many static fires, but spraying salt water on hot metal is probably not a good idea.
On the contrary, it's used throughout my industry (offshore oil and gas) to protect infrastructure. It only gets used for a short period of time, so there aren't issues with long-term use (corrosion, salt deposition, etc), and is very effective at turning jet fires (which eat through steel and concrete at alarming rates) into a manageable situation. And the idea is that the water spray gets turned on first, so it's the rocket exhaust hitting wet metal, not water hitting hot metal.

You'd have to try and match the salt levels to the brackish levels in the swamp (ie, likely to be lower salt content than seawater, which my industry uses), and you'd still have to manage the influx of large quantities of this salty water into the swamp, but I'd argue that the environmental impact is better than large chunks of concrete and dust being blown into the area.
If steel is hot enough then throwing water on it results in a layer of magnetite rather than haematite. Magnetite is an adherent oxide, it makes a nice protective black layer and doesn’t flake off. This is routinely used to protect windscreen wipers, to name one place people will definitely have seen it. Not sure what happens if you add salt to it though!
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Re: Astronomy and Space

Post by Pishwish » Wed May 03, 2023 11:24 am

Interesting. As i recall, Spacex lost their very first rocket due to corrosion of an aluminium nut in the salty air of an island launch site, but that's possibly because they cheaped-out on the part. Rocketlab have stated that retrieving boosters from the sea (as opposed to catching them with a helicopter) is not as bad for the engines as they thought, though these would then be refurbished before reuse. IANARS.

Eta : salty environment

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Re: Astronomy and Space

Post by EACLucifer » Wed May 03, 2023 3:50 pm

Pishwish wrote:
Wed May 03, 2023 11:24 am
Interesting. As i recall, Spacex lost their very first rocket due to corrosion of an aluminium nut in the salty air of an island launch site, but that's possibly because they cheaped-out on the part. Rocketlab have stated that retrieving boosters from the sea (as opposed to catching them with a helicopter) is not as bad for the engines as they thought, though these would then be refurbished before reuse. IANARS.

Eta : salty environment
Aluminium alloys vary in their corrosion resistance. Some of the older high strength alloys like Duralumin (nowadays 2000 series) which used copper as their alloying element were very vulnerable to saltwater corrosion. Aside from that, they offer extremely good strength to weight. Likewise the very strong 7075 alloy doesn't have the greatest corrosion resistance either. This can be remedied by plating the part with a thin layer of pure aluminium.

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Re: Astronomy and Space

Post by jimbob » Thu May 04, 2023 5:53 pm

I don't know enough industrial chemistry, but with the concrete dust that was eroded from the launchpad, I guess it would have got hot enough for the calcium carbonate to turn back into quicklime, given that it was eroded by a rocket exhaust?

Any ideas about whether this is a realistic concern?
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Re: Astronomy and Space

Post by monkey » Fri May 12, 2023 2:29 pm

Splodey.

clicky

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Re: Astronomy and Space

Post by Gfamily » Fri May 12, 2023 3:19 pm

monkey wrote:
Fri May 12, 2023 2:29 pm
Splodey.

clicky
If it 'splodes for more than 3 years, is it really a 'splodey thing?
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Re: Astronomy and Space

Post by dyqik » Fri May 12, 2023 4:48 pm

"The size of the solar system" doesn't sound that big to me.

I mean, it's a bang, but it's hardly the big one.

There are stars almost as large a Jupiter's orbit, or about 1/8 of the size of the solar system (taken as Neptune's orbit).

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