Rakaydos
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Posts posted by Rakaydos
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15 hours ago, sevenperforce said:
Raptor already has such a deep throttle range, so the turbopumps must have a pretty large allowable speed range as well. And they run independently. So I don't see why you couldn't vary the mixture ratio already, like the F-1.
First things first- if you perfectly mix the fuel and oxidiser, combustion will be too complete and you'll melt any material in existance. They have to be off-balance to have enough unburnt cool propellant to keep the temperature to reasonable levels, for rocket science levels of reasonable.
Second- metals that dont combust in hot oxygen rich enviroments are difficult. So it's normally easier to run the exhausts fuel rich, and also offers better ISP with most fuels that are lighter than their oxidiser.
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13 hours ago, sevenperforce said:
They have a very good oxygen-rich preburner so they should have no trouble scaling it up to make it an ORSC engine, and ORSC gives you a slightly denser fuel mix to boot. Perhaps using only a single preburner and turbopump would make the engine lighter.
But then you lose three main advantages of FFSC: lack of ox/fuel hot seals, variable mixtures and efficiently-sized preburners, and gas-gas combustion efficiency.
Not ORSC.
FFSC, but on the oxygen rich side of schtochimetric.
Higher thrust, lower ISP, cheaper and denser propellant mix.
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The majority view on NSF is that The Engine to Surpass Raptor is probably a second-generation FFSC methalox engine, using all the lessons and materials developed for Raptor 2 but unrestricted by Raptor's form factor, which was locked in years ago. Particularly optimizing "thrust per dollar" with the goal to make it so the cost to travel to mars is within the reach of at least a million people who want to go.
Also some speculation of Oxygen-rich methalox mixtures.
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8 minutes ago, AtomicTech said:
The discussion's been rather long and I didn't notice the tweet.
Thanks for pointing it out!
So, what names do you think would fit the former Raptor 2?
"Raptor 2 has siginificant improvements in every way, but a complete design overhaul is necessary for the engile that ACTUALLY makes "life multiplanetary""
Raptor 2 still exists, it just wont be eneough to make life multiplanetary. We already knew "raptor wont be really ready until, like Raptor v5", so it looks like "Raptor v5" is going to be this new engine.
https://twitter.com/elonmusk/status/1413909599711907845?s=20
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6 minutes ago, AtomicTech said:
It's not Raptor anymore?
Raptor 3 wont be Raptor anymore, but Raptor 2 will still exist.
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They've already hit on the "part reduction" of making the Upper Stage, Mars transit craft, and earth return vehical the same structure. Any optimization of the engine is going to have to work for all three regimes.
Put me down for "One of our interns came up with a cool idea that'll probably be cheaper, but means throwing out everything we've been doing with Raptor." They'll indulge sunk costs for Raptor 2, get the production line running for Raptor 2, and then the engine team will dive into this other idea.
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4 hours ago, kerbiloid said:
What if stick the smoke pipes underwater?
Ocean acidification
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The problem with the "kilometer of ice" arguments isnt the freezing temperature, but the evaporation temperature. Steam is ALSO a greenhouse gas, and the higher the global temperature average, the number of places with water that get significant evaporation also rises. (this is not, strictly speaking, "boiling the seas," but the closer the water gets to boiling temperature, the more likely any given atom might recieve an anomalous spike of energy that leads to that atom turning to steam- which is the process of evaporation)
This means that as global temperatures rise, it will take less to KEEP them rising... While simultaneously leading to bigger storms and stronger pressure gradiants, as well as more flooding as rivers and coast experience more water than mere "sea level rise" would account for.
Melting glaciers and sea level rise are the wrong side to be looking at. Evaporation rates is.
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2 minutes ago, JoeSchmuckatelli said:
Where do they put the engines?
Other end. The straight fins are the equivilant of SpaceX's grid fins, the flare at the far end is the engine bay cowling.
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9 minutes ago, JoeSchmuckatelli said:
You mean "A two week celebration of business as usual and blah blah blah"*?
*G. Thunberg
I take it that's a no.
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So has anyone in this thread been following the climate summit?
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3 minutes ago, SunlitZelkova said:
I was not talking about SpaceX's design process. They are very advanced in relation to their goal in that regard and I don't think there have been any internal issues at all. I was more thinking about public relations and "non-engineering" (dealing with regulations, getting land, permits, etc.) stuff.
He may not have that in a "black-and-white" manner ("textbook my way or the highway mentality") but that vibe is sort of there.
So, less "my way or the highway", and more "If you arnt part of the solution, stop being part of the problem."
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3 minutes ago, StrandedonEarth said:
Someone finally drank a glass of class (or Tory Bruno was ghost writing for him). Now if only Musk would do the same…
I'm not sure what you mean?
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13 hours ago, Codraroll said:
Rendezvous with Rama featured this as a minor plot point, if I recall correctly. Having a defined up and down makes it easier to orient yourself, and set a mental system of reference to prevent vertigo in zero G. Imagine floating at one end of a corridor, maybe doing some work along the short wall, grabbing a handhold, and looking over your shoulder. The comfortable perspective is that you're standing at the end of a horizontal corridor, like on Earth. Slightly more unsettling is imagining that you lie at the bottom of a deep, narrow well. But if your brain somehow tricks you into believing you've grabbed a hold to the ceiling of a tall and narrow tower shaft, you'd have to take several deep breaths to let go of that handhold, and it would be hard to focus on the work you're doing. Having some surroundings telling you what is up would be a real comfort in that situation.
"The enemy gate is down."
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Ironically, China is actually doing more about their CO2 footprint than America is.
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5 minutes ago, JoeSchmuckatelli said:
That's the point of the question I posed above. How fast did DDT affect life, vs how fast do you really expect anthropogenic climate change to adversely affect us on a species wide scale?
Chemicals are decades... climate is not.
This is where the ~20 year lag time is lethal- we have to act 5 presidential administrations before a crisis to have any hope of heading it off.
And it's looking like the world is having a hard time meeting that kind of challange.
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12 minutes ago, kerbiloid said:
The post-Ice Age ice melting was definitely a series of temperature changes, too.
So, why expect what didn't happen at much greater climatic catastrophes?
Why expect that their strengthening/weakening isn't cyclic?
The models describe their correlation based on a 100 year long history.
The climate changes were taking from centuries to millenia.Life adapts when change happens over thousands of years. Not so much, when it happens over mere decades.
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You still havnt addressed the existing strengthened storms. A model is considered useful when it reflects what is actually happening.
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2 minutes ago, kerbiloid said:
y=y(x)
... ?
We can see that the ocean raised by 120 m, and this didn't cause any unusual hurricanes.
Welcome to chaotic systems. If it were easy to model, the weather man would never be wrong. But the changes in hurricane strength is well documented at this point.
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44 minutes ago, kerbiloid said:
What's the formula of
deltaHeightOfStormWave, m (deltaOceanLevel, mm)
dependence?
Is it exponential ?
Or, say, some historical chart.
On the other hand.
If the ocean level gets lower by a meter, the storm waves would disappear at all?How about the 12kya ocean level raise, by 120 m?
Were there no storm waves before, or should we suffer from Gargantuan tsunami now?Independant factors. Hurricane strength is rising dramatically just off existing climate change.
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5 minutes ago, JoeSchmuckatelli said:
At what pace do you reasonably expect sea level rise?
Average sea level, in this case, matter less than storm surge and hurricane count and strength. The global average sea level might only be rising a few MM per decade off ice melt, but a hurricane can locally raise the sea level meters at a time, with waves on top of that.
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1 hour ago, JoeSchmuckatelli said:
(Slow climate change is something we can adapt to quite readily, but stupidly poisoning ourselves because its convenient and cost effective is... stupid).
Slow is relative. A major city like, say, miami has about half a million people. Just building half a million new apartments, somewhere out of the flood zone, is going to be tens or hundreds of billions of dollars- and that doesnt even count infrastructure, like sewer mains, power lines and internet connections, or services, like schools, commercial districts, and office space, if you build it a place not already choked with existing construction. That's not the sort of thing that can appear overnight. Having to abandon all the existing infrastructiure we built in what is now the "wrong" places is what makes things difficult.
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7 minutes ago, GuessingEveryDay said:
Tsar Bomba was only 2 meters wide, and 8 meters long. This includes the fins, so we can definitely get rid of that, but you would probably have at least enough room for 7 Tsar Bombas. The payload would be called Nuclear Pluto.
That's a MERV. (multiple independant reentry vehicals), which the person disallowed.
How much did the Tsar bomba mass? that might be more of a restriction, though the weight might be difficult to find when explosions are measured in the equivilant weight of TNT.
Edit: 27 tons, so an expendable could carry 9 50-megaton bombs. I probably slipped a digit in my previous post.
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32 minutes ago, 55delta said:
I was going to bring this thread back to point out how difficult to hide and ineffective an orbital laser weapon would be. But I thought of something better.
Imagine that someone was crazy enough to make Starship into a nuclear bomb (instead of using a better, purpose-built ICBM.) That is, a Starship loaded with a single nuclear device (as opposed to a MIRV) somehow fitting into its cargo bay and used as a ICBM. If the whole cargo section could be used, and that such a nuclear device could be built and installed, how power could a Starship nuclear weapon be?
For this thread, we dont care about practical reality, so lets pull out the big numbers.
"Even more efficient than fission, nuclear fusion would liberate 6.46 × 1014 Joules of energy per kilogram of hydrogen fuel, meaning it would take a mere 867 tonnes of hydrogen to power the world"
"TNT has an energy density of 4.6 million J/kg. This means that setting off one kilo of TNT releases 4.6 million Joules of energy,"
...running some numbers...
"Sir, we estimate that starship could carry a 140 megaton Fusion Bomb, almost 6 times more powerful than the largest nuclear bomb ever deployed."
wait, that's the reusable numbers. 250 tons expendable... call it 225 megaton thermonuclear weapon. 9 times larger... so round up an call it an "Order of magnitude improvement."
SpaceX Discussion Thread
in Science & Spaceflight
Posted
Given that the intermediate zone is RUD territory, and that rocket engines are incredibly optimized, I doubt an off the shelf engine could cover both regimes. Certainty not without including the same exotic materials from the OR turbopump in the main combustion chamber and nozzle!