FleshJeb
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Posts posted by FleshJeb
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1 hour ago, seaces said:
Thank you for the links provided. When I was building my craft I was aware that my mission payload as well as dry weight of the stage that is supposed to get me to Gateway needs to be light I tried to cut down on dry weight as much as possible. I arrived at idea of multiple smaller tanks connected with fuel lines that I keep dropping in space as I go. Per you link provided I think I made something called "Breadcrumb" staging. Stage pushed by two Terrier engines and FLT-T400 tanks (I think) that I drop. Initial TWR is around 0.5 and it grows as I burn till 1.1.
Breadcrumb is a fantastic method. Be aware that all those decouplers and fuel lines (and struts) add dry mass, so it may make sense to use fewer, larger/longer tanks, especially as you get down to the smaller diameters. FLT-T400s are pretty small. Structural complexity/part count can be an issue too.
There's also a rule of thumb for mass-efficiency that says for engines with roughly the same efficiency, each stage should have the same amount of dV. This is somewhat broken by the non-serial staging methods, but it's a good guide. You may be best off having your probe stage sitting on top of:
- A long 1.25m stage with one Terrier (capture)
- A 2.5m stage with a Poodle, or a Wolfhound if you've got it. (capture)
- A 3.75m stage with a Rhino. (transfer)
- Surrounded by 3.75m stacks with Mammoths, Asparagus-ed into the Rhino core. The Rhino and Mammoths all start at launch. You'll probably have a couple of Mammoths +Rhino left in orbit to start the transfer.
- Add SRBs to fill launch TWR needs, if any.
This is the gravity brake that Jimmy mentioned. From the BH dV map, it looks like you want to use Kohm, as I'm guessing it's the biggest moon at Gateway:
https://wiki.kerbalspaceprogram.com/wiki/Tutorial:_Gravity_Assist#Gravity_brake
https://forum.kerbalspaceprogram.com/index.php?/topic/186643-how-to-plan-a-tylo-gravity-assist/
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Efficient staging and/or orbital refueling is your only good answer.
One of the most efficient staging methods is called Asparagus, and has the benefit of a reasonably consistent TWR. You can also have multiple stacks of asparagus-staging, arranged in series, to suit the TWR and dV needs of that phase of the mission.
https://wiki.kerbalspaceprogram.com/wiki/Asparagus_staging
https://forum.kerbalspaceprogram.com/index.php?/topic/68532-staging-methods-overview/
If you really want to get into the weeds, a guide on optimizing multiple stages is on this page:
http://www.projectrho.com/public_html/rocket/multistage.php
I've built "serially asparagus-staged" LFO rockets that have in excess of 20000 m/s dV, and an average TWR > 1.0. Because when you're trying to circumnavigate the planet at faster than orbital velocity, you have to thrust straight down for extended periods.
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I think it's important to note that: If one were to apply the same critiques to the science of economics that one applies to the science of climate change, economics would (IMO) come out looking a lot worse.
Points of interest:
- Ideological motivation of the practitioners.
- Quality of assumptions made.
- Quality of data and the size of the error bars on that data.
- Quality of the methodology, and whether it properly takes into account all external confounding factors.
Not attempting to get into politics or economics here, just drawing a parallel as food for thought.
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Desmond Tutu passed today. A very VERY good man:
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I didn't realize we'd detected ANY rogue planets, much less 70. What a wild time to be alive:
https://www.inverse.com/science/largest-group-of-rogue-planets
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2 hours ago, DDE said:
Can maritime diesels and gas turbines use bunker oil? I'm seeing mixed signals, especially when it comes to, sigh, the procurement politics behind late Soviet Navy steamships.
Take a look at the F-76 listing: https://www.globalsecurity.org/military/systems/ship/systems/fuel-oil.htm
EDIT: Looks like there are a few grades of bunker oil. I'm actually not sure now if F-76 qualifies.
EDIT 2: The answer is yes for gas turbines:
https://www.wartsila.com/energy/learn-more/technical-comparisons/combustion-engine-vs-gas-turbine-fuel-flexibility
"Only about 400 GE gas turbines globally operate on crude, naphtha or heavy fuel oils." -
Not apropos of this particular thread: Is it possible for us to be less reductive and hyperbolic when discussing serious scientific matters? Or is poop-flinging more entertaining than having serious, good-faith exchanges and learning things?
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44 minutes ago, Nothalogh said:
All other concerns must cede priority
No.
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On 12/22/2021 at 12:34 AM, Scotius said:
Hey, what about not giving offshoot race reasons to wipe us out? Y'know - treating them well, making friends, teaching them things like empathy and altruism?
In effect such race would be humanity's children - so raise them and teach like children.
Anyone who wants to look at this notion in detail should read The Uplift War by David Brin.
Fiben Bolger is an uplifted chimp. He knows Uplift is a screwed up situation, but he's aware that humans do it more ethically and empathetically than everyone else. His motivations are complex and conflicting, and I think he's one of the best characters in science fiction. I'd have a banana and a beer with that guy.
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2 hours ago, king of nowhere said:
perfectly retrograde
I don't think this makes much difference in your case, but for the sake of accurate documentation: The atmosphere calcs happen in the Surface reference frame, so the Navball/SAS should be switched to Surface mode if you want to be retrograde relative to the air.
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4 hours ago, TheSaint said:
Kramax puts it down flat every time
Nevermind then!
5 hours ago, TheSaint said:They put the go-go in the zoom-zoom!
Bah, I thought those were OPT engines. I think they're actually NFA Broadswords. I haven't used them, but I took a look at the thrust curves on github--All I can say is YES. Also:
"The Broadsword is large and terrifying. So terrifying, in fact, that our engineers have postulated that it works by so deeply frightening the ground that the entire planet tries to run away." -
I'm a big fan of sandbox and self-imposed restrictions.
I will lightly suggest that your landing gear is a bit tall and narrow and may cause you headaches.
Are those the schramjets? They're FUN.
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3 hours ago, SunlitZelkova said:
Yes the strike cadence is better, but it seems like very little for so much cost, especially in the face of modern anti-ship missiles and such
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Some experiments have been performed in which M109s on Army ships (which are a thing) fired their cannon at a point, and hit it. This would be a very cheap substitute for naval gun fire support if the need arises.
The question being, "Is the kill cadence better?" A precision airdropped munition is very likely (90%) to hit and kill on the first try.
A brief googling shows that the CEP for Iowa in the 1990s with consistent powder and radar-verified muzzle velocity was 150 yards at 19 miles range. ref: https://www.popsci.com/blog-network/shipshape/rise-and-fall-battleship-and-why-they-wont-be-coming-back/
You could fire that all day and not kill what you need to kill.
Whereas, you can put this through a window at 69 miles, and hit a moving target at 45 miles: https://en.wikipedia.org/wiki/GBU-53/B_StormBreaker
Comparable weapon that will also do hardened targets: https://en.wikipedia.org/wiki/AGM-154_Joint_Standoff_Weapon
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They also did guided rockets off a ship deck: https://www.thedrive.com/the-war-zone/15410/himars-goes-to-sea-us-marines-now-fire-guided-artillery-rockets-from-ships
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2 hours ago, Spacescifi said:
Which means that you need a middle man... coolant, to offset overheating your infinite battery while you discharge massive amounts of energy to fly. Which of course will mean the ship never leaves the ground unless you stage it like rocketry.
What would happen if you got that coolant so hot that it left your ship at a really high speed? Man, you could even put it through some kind of nozzle to direct the output!
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It's a bit cheaty and not quite what you want, but maybe you could use AirPark? Have the functionality pinned on the mothership, focus on, and release the payload, then punch the Park button?
Then you fly your payload mission, and come back to the mothership later. I'm not sure if you can just recover an airparked craft, but you could fly it home.
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I know they messed with some of the nodes on the heatshield, so it might have something to do with that, but I think it's probably the trajectory. The more recent re-entry looks a lot shallower. The trick with heatshields is a steep, deep re-entry (see the link below). I'm a spaceplane guy, so I almost never play with the rocket parts--I think that pod could almost do the more recent re-entry without the shield.
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What color is your game clock when this is happening? If it's yellow or red, that means KSP is struggling to do all the physics calculations in real-time.
The KSP engine always does 50 physics updates per game-world second, to ensure the accuracy of the simulation, but that will often take more than one real-world second.
See here:
You probably want to try sliding the Max Physics Delta-Time per Frame to 0.12. You'll have to get to the settings in the main menu. It's under General, System.
Side note: Until I read the above link, I always thought this affected the quality of the simulation. It does not.
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On 11/25/2021 at 4:14 PM, JoeSchmuckatelli said:
From the paper cited by the above article:
'a survey of the recent literature shows that our knowledge primarily hinges on subpolar Atlantic records, while, due to the paucity of Arctic records, polar dynamics still remain elusive'
'Controversy still remains on the relative impact of natural versus anthropogenic forcing on the North Atlantic system'
'Our results combined with existing reconstructions demonstrate a rapid and early Atlantification of the eastern Fram Strait at the onset of the 20th century' [FleshJeb's bolding]
'These findings highlight a potentially important model-data discrepancy that begs for improved historical and preindustrial simulations with better constraints on the freshwater budget of the Arctic and North Atlantic Oceans. Resolving these modeling issues will be crucial to improve the accuracy of projected Atlantification in response to future Arctic warming.'
https://www.science.org/doi/10.1126/sciadv.abj2946
I did at least THREE hours of research on this at the time, but I ran out of energy to actually respond. Apologies that this is all from memory.
Pertinent facts:
- The methods they used have funny names and they're hard to google. The broad category is called a https://en.wikipedia.org/wiki/Paleothermometer
- They took a grand total of ONE core sample of the sea bed.
- What they're looking at is the preserved concentrations of chemical/isotope compositions of various species of microbes, as well as the radiocarbon dates of the slices they take.
- The concentrations reflect how many of that microbe was alive at the time, and that number is reflective of the water temperature.
My issues with their methodologies:
- The error bars for one of the methods is +/- 4deg C, but this requires extensive cross-correlation with multiple cores from the same geographic region, because it's species/environment dependent. A similar experiment in the South China Sea did something like 300 cores, another one well over 100. They DID cross-correlate with other temperature data, and other people's cores, but not nearly to that magnitude.
- IMO, large error bars on the derived temperature are better suited to looking at long-term (1000s of years) climactic trends, but they're applying it to a very short timespan (120).
- In addition they used fairly thick core slices (IIRC representing 5-10 years of sedimentation). This affects the time-resolution of the data. So with both these dimensions they're looking at some pretty broad error ellipses.
- The microbe species concentrations are very sensitive to freshwater inputs from nearby land, and they took that core fairly close to the coast.
- I measure the things outdoors for a living. The data I collect is fairly simple, and there's still a quite a bit of nuance with when, how, and how much I take that data: I would have taken at least THREE cores, spaced out by a few kilometers, and checked those against each other. I don't care how good their collection, lab, and analysis procedures might be, nature can always throw you a serious anomaly on one sample.
Neutral note:
- The research institute that did this study is underwritten by a bank. I spent some time looking for obvious biases or conflicts of interest in the organizations, but I didn't find any.
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So, while it WAS extremely interesting to learn about, I didn't find that the broad conclusion bolded above was well-supported at all.
This is why your links royally liquid me off sometimes, Joe.
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On 12/13/2021 at 9:19 PM, tater said:
It's partially the fault of the person interviewed not realizing they need to say things in an accessible way,
This is the line of argument I'm going to use the next time some STEM-lord whines to me about having to take Humanities classes.
(My Calc 1A professor also had an art degree; the man was an absolute wizard on the chalk board.)
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[All bolding mine]
Ray's NBC source:
Global sea levels will rise two to six feet by 2100 on the current trajectory, driven mainly by melting in Greenland and Antarctica, according to NASA satellite data. However, scientists have warned that projections underestimate the impact of climate change on sea level rise.
From that link:
If the rate of ocean rise continues to change at this pace, sea level will rise 26 inches (65 centimeters) by 2100
"This is almost certainly a conservative estimate," Nerem said. "Our extrapolation assumes that sea level continues to change in the future as it has over the last 25 years. Given the large changes we are seeing in the ice sheets today, that's not likely."
Additionally:
https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-levelAlong almost all U.S. coasts outside Alaska, the 2017 projections indicate that sea level rise is likely to be higher than the global average for the three highest sea level rise pathways, thanks to local factors like land subsidence, changes in ocean currents, and regional ocean warming.
Regarding rates:
- The rate of sea level rise is accelerating: it has more than doubled from 0.06 inches (1.4 millimeters) per year throughout most of the twentieth century to 0.14 inches (3.6 millimeters) per year from 2006–2015.
From here:
https://earthobservatory.nasa.gov/images/148494/anticipating-future-sea-levels
That growing knowledge base is why scientific organizations like the Intergovernmental Panel on Climate Change (IPCC) are publishing sea level rise projections with increasing levels of confidence. In its 2019 report, the IPCC projected (chart above) 0.6 to 1.1 meters (1 to 3 feet) [(sic) 0.6m = 2ft] of global sea level rise by 2100 (or about 15 millimeters per year) if greenhouse gas emissions remain at high rates (RCP8.5).
I look at tidally-influenced hydrology and flood-resistant infrastructure fairly frequently. This is what the cross section looks like when you have to raise a 10-foot levee by 2 feet:
Anyway, I'm tired of dealing with https://en.wikipedia.org/wiki/Brandolini's_law for the night.
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21 hours ago, tater said:
We've been thinking about some cool land between here and Colorado maybe, I don't even consider lots less than 100 acres, and only that small if it has a hill so I can potentially point any house I put there away from seeing anyone.
I've been in rural land development for most of my adult life, but this is off-topic so I'll spoiler it:
SpoilerApologies if you already know these things:
First priority: Make sure the land has good potential for well and septic, and preserve those areas. Without them, the property is next to worthless. I've seen a multi-million dollar parcel devalued because the owner decided to hop on the tractor and grade out some building pads and a driveway without permits. They were right in the middle of the only suitable soil for a septic system on the entire parcel. The "muh property" attitude ruined 20 years of this guy's dreams. (This was before my firm was involved.)
Second: On hilly land, it can be darn near impossible to grade a driveway in that meets local jurisdictional slope requirements. I've seen a narrow, steep parcel that the owner wanted to put a house at the top of, that would have required driveway switchbacks over 1/4 of the area of the parcel. 15 years later, and there's still no house on the property.
Third: Property boundary / access rights. You may want to get a boundary retracement done as a condition of purchase, and split the cost with the owner. It may be that the current owner is used to accessing the parcel across a neighbor's land because it's convenient, but that doesn't necessarily confer an access easement. If there's any other place to get from a public road onto the parcel, even if it's much more difficult and expensive to construct, the neighbor can deny access via the convenient route.
Of course, all this is dependent on state and county codes, and individual geography, so hire professionals and listen to them. Don't hire the up-front cheapest firms, it will almost certainly cost you more money in the long run. Also, hire civil/survey people that work in that county a lot. Local expertise is invaluable.
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Here’s a work-in-progress Neutron for RSS/RO. He’s soliciting input on the specs.
What type of government is your invitable Empire in KSP 2 going to be?
in Prelaunch KSP2 Discussion
Posted
Orkish Kult of Speed.