Terwin
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Posts posted by Terwin
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Sociopathy requires no malicious intent, just a disregard for the right and wrong, and ignoring the rights and feelings of others.
I have yet to meet a 1 week old with regard for anything beyond their own discomfort, and perhaps bright colors.
(It looks like they do not even start showing attachments to caretakers until 6 weeks)
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48 minutes ago, DDE said:
I doubt it. I do believe there is an initial bias towards empathy.
You can't rely on it to run a big society, though.
A quick search on 'child developmental psychology' mentions Piaget's 4 stages of cognitive development.
According to that, it is in the 3rd stage(7-11 years old) that "children also become less egocentric and begin to think about how other people might think and feel."
I fail to see how you can be empathetic if you never even consider how others might think or feel.
(I would suspect that many people never actually achieve that level of interpersonal awareness, but that is the theory at least)
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6 hours ago, SunlitZelkova said:
Humans are not automatons. We have the power to move beyond selfish impulses we are conditioned to have from birth- not naturally possess- and work together.
It always amuses me when people forget that all humans are born as self-centered sociopaths, and only through socializing do we learn to reciprocate, cooperate, and all of the other 'virtues' of humanity.
Learning to read does not help one come to the realization that all of those 'humanoid interaction devices' are actually just as self-aware as oneself, each with their own views and understanding of the world that suffers from ones own, and just as valid(I can think of many so called adults that do not get this, sadly. Many of them using such ivory tower thinking that humans start as an effective blank slate that can be shaped as they like)
And being raised by robots would not improve this situation.
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52 minutes ago, Meecrob said:
The example/trope you seem to be getting at is when someone adds in overhaul time and says "every hour of flight time requires 10 hours of maintenance" or something similar. A different way to manipulate the numbers would be to say that for a 4 hour cross-country flight in a Cessna, the only maintenance performed was a 15 minute pre-flight inspection by the pilot.
Both of those examples are technically true, but are meaningless for comparisons.
I did not cite any examples or tropes, what are you talking about?
52 minutes ago, Meecrob said:In your example you are saying that overall, the average per launch is 1 hour inspection time. Cool, lets use your round number. When designing the maintenance schedule, engineering would take note of all things that require inspection and schedule those inspections to coincide with each other. So lets say we have 10 items that require inspection to keep the round numbers going. If done individually, they would take 10 hours to inspect. However, since inspections require removal of fairlings/access panels, etc. if you already have them removed for one inspection out of 10, it means you can save 9 removal and re-installs of the fairings. So, if the fairings take 10 minutes each, we are now at 8 hours, 20 minutes of inspection. Now that number is for one person. If possible, maintenance will get multiple inspectors on the task. Lets assume they could only get two. That still cuts our 10 hours down to 4 hours 10 minutes.
So now we have 9 flights on schedule and one flight delayed 4:10. I don't have the numbers handy, but that's about how many flights get scrubbed due to weather, isn't it? 1 in 10-ish?
I was attempting to illustrate that rocket burn times per flight are so radically different from jet burn times per flight, that attempting to compare them is like comparing how you serve blueberries and watermelon.
Sure they are both firm berries that get soft when they go bad, but they are wholly different from each other in many practical ways. I cannot imagine someone being satisfied with a slice or two of blueberry, nor would I expect to meet someone who frequently eats dozens of watermelons at a sitting.
Much like I would not expect rocket engines to have maintenance times < burn times like jet engines can manage. Rocket burn times are just not on the same scale as turbofan engine run-times.
I also strongly suspect that chemical rocket engines tend to burn much hotter and higher pressure than turboprop engines, if only because ~80% of the turboprop working fluid is inert gasses.
Rocket engines clearly have a much higher fuel through-put than turboprop engines:
"A Boeing 747 or 777 typically consumes approximately 5,000 gallons of fuel per hour while in flight."
"Raptor consumes 140kg of methane per second"
Conversion:
Jet A1 Fuel Conversion ChartLbs Litres U.S. Gallons 1000 568 150 5000 gal -> 33,333 lbs -> 15,119 kg
15,119 kg/hr / 3600 s/hr = 4.2kg/s
So 4.2kg/s(all 4 jet engines on 747) vs 140kg/s (per engine).
This suggests each raptor burns ~ 133 times as much fuel per second as a 747 engine.
So yes, that seems very different, even if the outside environment does not change much.
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Wikipedia says the burn-time of f-9 first-stage using FT engines is 162 seconds. Even just a quick visual inspection of the engines of a Falcon 9 would mean maintenance time > run time.
So if each first stage took less than 1 hour of inspections/repairs per launch, it would still be getting maintenance > 2x the total burn time of the engines, something that would likely put most airlines out of business.
(9*162 / 60 = 24.3 minutes of total burn time per launch. May not include <1m for landing burn))
If SH takes 2 hours from landing to launch, it could still average > 10x maintenance time per flight-hour. (F9 takes just less than 10 minutes from launch to landing for RTLS)
I do not see much value in taking SH maintenance down to even a 1:1 ratio of flight time to maintenance time, as the falcon 9 needs >30 minutes to load fuel, and I would not expect SH to be faster than that.
(As refueling is often counted as maintenance, taking SH down below 10:1 maintenance time:flight time might well be impossible even if the only maintenance is refueling)
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Mechanical power from water is easy and is more than 5000 years old, so that will clearly be a thing very quickly. Mechanical wind power is almost 3000 years old, both less concentrated and less reliable, but still pretty useful and should be back fairly quickly.
Turning either of those into electric power mostly requires magnets and wire, so intermittent local power(like a flour-mill that doubles as a battery charger) should be reasonably common, but if it gets set up by someone with limited understanding of electric theory(such as myself) such a charger is likely to damage the batteries with every charge. Fortunately, batteries are more than 200 years old, so if you have copper and zinc, you can turn those into electrical power as well.
Unfortunately, oil is of limited use without refineries, and refineries would be a primary target(tanks run poorly without fuel after all), so only chemists would be able to run vehicles until new refineries were produces(I think fractional distillation can provide something functional, but I would expect it to be hard on any engine that uses it)
Straight crude could be burned as fuel, but would generally be inferior to coal, as liquids are harder to store and handle than solids. Wood would likely be superior to both where it is available, as it is much less likely to produce hazardous fumes when burned.
So long as fuel reserves held out, food production would be in good shape, but would go down dramatically once farmers run out of diesel. Food processing would likely have issue before that however. Fortunately, it looks like almost all of the population is is major cities(86% in cities of 50k+ in 2020 for the US), so a drop in food production is probably not as critical as it would otherwise be.
There would probably be at least a decade of 'everyone is a farmer' with the related loss of population to starvation before we stabilized and started growing again. Assuming no one was in a position where they could take advantage of our weakened state to invade.
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Mars can be as little as 34 million miles or as much as 250 million miles. When on the other side of the sun, mars is more than 7x the distance from Earth as when it is close, and when it is close, there is no need to detour around the sun, making it even further.
No matter what sort of transfer you make, multiplying the distance by more than 7 has a major impact on if the transfer is even possible, not to mention the time increase.(There are many parts of the orbit where waiting to launch will make you arrive earlier)
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If you can ignore gravity and have a vacuum -only drive, why not just throw on a propeller?
Either the prop is enough to accelerate you or you can use your vacuum drive. It can even be an electric prop so you only need fuel for the vacc drive.(You could throw it inside a shell for protection, but just making it retractable would likely be better)
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I was thinking that mars and the moon would primarily start as retirement communities, with support personnel, etc.
The lower gravity should reduce strain on the body and allow for more autonomy for people too weak to get out of bed on earth. Might even allow for better longevity as it would reduce the minimal functional strength of bones joints and muscles(including the heart).
Sure such individuals would need to be in a liquid bath for launch and possibly landing, but they would have the funds and low concern about long-term viability needed for such an endeavor.
The colony would be the laborers and heath workers supporting the retirees.
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1 hour ago, Exoscientist said:
The trouble is if you run the numbers for the specifications SpaceX has cited for the SuperHeavy and Starship, i.e., their dry and propellant masses, and Raptor thrust and Isp, SH/SS should well be able to make 100+ tons to orbit as a reusable. I think NASA engineers were able to take the SpaceX proposal as a viable solution for an Artemis lander because their numbers checked out. But now we find the reusable payload for the current version is only 1/3rd the originally predicted 150 tons to orbit. What explains the drastically reduced payload capacity? This is a major issue because the current version can not perform the refueling functions of the Artemis lander missions at that low payload value.
My opinion: I think NASA was blind-sided by that low announced payload value. SpaceX and NASA will have to be open about what that severe loss in payload, by 100 tons, stems from.
Bob Clark
Looks like the plan is for Starship V3 to have a capacity of 200t to orbit.
Why would NASA be worried about an early prototype not being as capable as the expected delivered rocket?
Especially when the delivery plan provides greater performance than was initially expected?
Did you also expect NASA to complain when grasshopper never made orbit?
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You need incredibly good precision to manage replaceable parts. One person would likely spend their entire life just working through the steps to get to a precision where things like interchangeable parts could actually work, and that assumes access to materials that the romans never made use of(and thus may not have had access to).
There are many things that took one or more life-times of refinement to get things to a point where other things could be done.
Measuring precision(length, weight and volume, each taking a great deal of effort), materials purity(each material needing lots of effort, and often other highly pure materials needed as reagents)
I would expect that an immortal with unlimited modern knowledge and authority that went to the 1st century Roman empire could manage to double or triple the rate of advancement, even cutting out a few hundred years of non-progress during the dark ages if they had unlimited food/no need to eat as well.
I'm not sure if preventing or encouraging wars would be more beneficial to that advancement, but the wrong choice would obviously cause set-backs.
Unlimited authority and immortality would both be needed or else someone would kill or imprison you in the first few months because you were trying to do something that would annoy someone ruthless/powerful.
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I believe you need to use an engineer to 'perform maintenance' to transfer fuel from a nuclear fuel container into a reactor and transfer depleted fuel from a reactor to a nuclear waste container.
Automatic maintenance can also perform this function(but I think the engineer is still needed)
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Considering the speed of bureaucracy, this might well be a prompt response to IFT-1
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Anywhere you transition from flesh to bone/chitin is a possible vector of infection. Much like our gums need regular maintenance to avoid infections that lead to tooth loss, even though they are in an environment that is hostile to most microbes.
Why make the hands out of chitin?
Also, a small tube on the back of the arm should be less prone to clogging/obstruction(sort of like a urethra and just as prone to infection if not kept clean). 70' seems unlikely, even 20' seemed pretty optimistic and you still need to hit the same spot with both squirts, so anything more than 5-10' is probably useless unless a majority of an individuals caloric intake is dedicated to producing the liquids along with a large internal reservoir to build up enough to have a decent chance to hit farther away.
(How far away can you spit and hit a quarter laying on the ground, consistently enough to be useful when you only get 1 try per day? Now try the same trick with your urethra, but you only get 0.5-1ml per day and you need to hit the same quarter-sized patch with both arms. A palm-vent would be even worse as even finger-placenent would affect the stream direction.)
Also, humans are expert throwers, so don't pretend your theoretical species is just really better at rage, as humans are already fairly optimized at that.
Tldr; a bi-reactant biological ranged weapon, even if feasible to make, would be terrible to use and probably not have a greater useful range than an extendable club/baton or a baseball bat.
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2 hours ago, darthgently said:
Would there be any advantage to the pusher plate being parabolic with the focal point being the reaction zone? I'd think the angle of incidence of the explosion on the plate would make a difference, but would it be significant?
If the compression wave hit the entire surface at the same time, that seems like it would make the impact have a shorter, sharper duration. Considering that you are already needing a shock-absorber, that does not seem like a good change.
If the explosion is off center, having curved surfaces could also introduce lateral jiggle, potentially causing severe wear or even destruction of the shock-absorbing mechanic.
A flat surface where all forces striking and rebounding from it should only push you froward seems like a safer bet.
On the other hand, if you are close enough that you could cover a larger proportion of the shock-wave with less material by curving it, then it may be worth the extra engineering.
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That is called burning and it turns the diamond into CO2. Once the diamond is lit, it can keep burning even at very low temps, even submerged in liquid O2.
Methane is great because it is
40%25% hydrogen by weight. (Water is only20%11% hydrogen by weight)(Forgot neutrons)Pure hydrogen is much better for the isp but ts very low density and hard to handle .
Adding anything to it just before burning can only hurt isp.
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The storage requirements for metallic hydrogen make it a non-starter for rockets. 90% of your launch mas would be fuel tank, limiting you to short, low-velocity hops.
There was a theory that metallic hydrogen had a metastable island that could make it almost shelf-storable and remove that constraint, but it did not work when tested.
Methane is used because it is a much more dense and easier to handle holder of hydrogen. It would be silly to turn hydrogen into methane for rocket fuel unless you planned to store it for a while.
Diamond melts around 4500c and hydrogen evaporates at -253c, so you are not combining those in any direct way.
Metallic hydrogen converting to hydrogen gas(H2) releases much more energy than burning it does, and leaves you with pure hydrogen reaction mass, giving a theoretical isp of 1700.
Adding anything to it will only reduce that number.
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Well, depending on you definition, might have been Ikaros in May of 2010(first solar sail)
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Unless you are shipping tons of rare resources off-world, you cannot 'run out of' resources, you can run out of conveniently available or cost-effective to harvest resources, but you cannot run out of the resources themselves.
(Volatiles like oil may need to be reconstituted, but that is still an option)
Worst case scenario is resources are more or less evenly distributed and we need to harvest them similar to how we harvest 'rate earth minerals' now(they are not rare, they just do not occur in usefully concentrated forms)
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11 hours ago, Spacescifi said:
I dare say immortality and capitalism don't get along, since overpopulation creates scarcity of resources and the number of jobs to fill in any society is limited.
In capitalism Entrepreneurs create jobs. More entrepreneurs = more jobs.
So long as there is enough capital made available to entrepreneurs, there is no limit to the number of potential jobs. Also, productive labor produces capital, allowing for the exponential growth of wealth we have seen in the last few hundred years.
From 1ad to 1000 ad, india' gdp per capita stayed arout $450(1990's dollars), while china grew from $450 to $466.
Roman Italy was ~$800 in 1ad
By 1500ad India grew to $550, and china to $600, with Italy still at the top with $1100(this was the Renaissance with Michelangelo and da Vinci)
In 1750, 1st world gnp per cap was $804(still 1990 $), but by 1990 that ballooned to 15,413. A 10x increase over ~250 years when the prior wealth levels had been stable for ~1700 years.
I attribute this growth to the growth of industry, ie capitol.
Population was also only growing very slowly.
190M in 200ad, 275M in 1000ad, 610M in 1700ad, 1B in 1804, 2B in 1927, 3B in 1960, etc
More people means more jobs and more wealth per person(on average) because people performing productive work creates wealth.
Not to mention that someone living in public housing today has luxuries that were simply unavailable, even to kings, a few hundred years ago.
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15 hours ago, StrandedonEarth said:
Yeah, I was thining it would make more sense as combined cycle, since spacecraft need power. But would it not be more efficient to just keep heating the plasma with microwaves, like VASIMR?
While it may make sense to supplement the heating with microwaves if your nozzle can handle higher temps than your reactor, converting from heat to electricity to microwaves to heat cannot be as efficient as just conducting the heat directly.
So heating up your reaction mass to the reactor temp while simultaneously using it to cool the reactor is much more efficient.
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It makes sense that being much closer to success would mean fewer things to address, and as there was no real additional hazard area for this flight, the faa is probably not terribly concerned about the mishap, so long as there is a plan to do better.
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Straight lines are used because they are easier to draw and visualize.
Actually the lense will bend all light that hits it. This is part of why you generally have camera lenses in an opaque black tube: to minimize extraneous light that could interfere or obscure part or all of the image .
Much like friction-less inclines, those lines are a simplification to provide a clearer explanation, not a fully accurate reflection of reality.
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1 hour ago, Minmus Taster said:
Oh boy here we go again..
I had hoped that following the flight path all the way to the end might not count as a mishap, but at least the additional hazard should be close to zero.
I expect that most of the mitigation is to improve control, which SpaceX wants to do anyway.
A City On Mars
in Science & Spaceflight
Posted
Not all companies do or are even allowed to make money.
SpaceX is a private company and could readily spend every dollar they earn on the owners pet projects if they so choose.
As far as I can tell, the entire purpose of SpaceX is to make a mars colony a reality, and if they go bankrupt the day after the colony reaches self-sufficiency, then that will be considered a win.
Funding that colony is the reason starlink exists, and if needed, other space-based companies may be founded to help.
They are even getting government funding for some of the development costs by bidding on side-projects that NASA wants done which are within the capabilities of the planned interplanetary craft.
I expect there to be major financial issues, but the richest man in the world seems intent on using both his fortune and his business accumen for this purpose and I am not going to complain about that.