-
Posts
8,984 -
Joined
-
Last visited
Everything posted by sevenperforce
-
Or you can go the opposite route and offer tax credits direct to suppliers in proportion to the percentage of their energy that comes from renewable resources. One problem comes from failure to distinguish between the "worst-case scenario" in terms of total warming impact and the "worst-case scenario" in terms of how rapidly that total warming impact point is reached. For the former, we are already in the worst-case scenario, and that will not change unless we take drastic action. On our current path, we are going to melt all the land ice. Melting all the land ice is the worst case scenario. We need major change in order to avoid this worst-case scenario. How quickly will we reach that worst-case scenario? We don't know. Hopefully there will not be a sudden and drastic runaway feedback collapse a la Venus. Hopefully the worst-case scenario is at least 80 years away. It doesn't look good, though. In terms of the timing itself, the worst-case scenario is of course a Venusian feedback loop. That particular scenario seems unlikely at this point. I think that climate change skeptics/deniers (along with much of the general public) hear scientists say "we are already in the worst-case scenario" and assume the scientists are talking about the timing of it rather than the overall endpoint. Thus it suggests a higher level of alarmism on the part of the scientists than is actually there, which leads to people ignoring the realities of it all.
-
totm nov 2023 SpaceX Discussion Thread
sevenperforce replied to Skylon's topic in Science & Spaceflight
Cool image, but fuzzy. I think I can make out the skirt mating points where the rim becomes thicker. Are there three mounting points in the center for pusher separation rods to the Raptors? -
Mission To Mars Scifi Challenge
sevenperforce replied to Spacescifi's topic in Science & Spaceflight
There is no limit to waste heat ejection capacity in a thermal rocket. You just design an engine that is large enough to provide the desired flow path and rate for the heat capacity of the propellant you are using. That being said, @Shpaget is absolutely correct; 500 terawatts is nearly thirty times the continuous human and industrial power consumption across our entire planet, from all energy sources. Suggesting the use of a continuous 500-terawatt laser (which would NOT be the NIF laser, because the NIF laser cannot do that) is kind of like suggesting the use of Saturn's moon Rhea as a bowling ball. It's just not a scale that makes any sense. For reference, the F-1 engine had a peak power output of 23 gigawatts. A thermal rocket engine large enough to provide a propellant flow path and flow rate necessary to handle 500 terawatts could be theoretically built, but it would weigh around 183,000 tonnes, 75% heavier than the world's largest aircraft carrier, and it would have a nozzle approximately 21% larger than the entire Pentagon complex. NOTE: this does NOT mean that we would want to build one of these....because, again, we don't have that kind of power source. If the rings each have a mass of two tonnes and you want to use them as the powerplant for a thermal rocket engine, then the associated mass of the heating chamber and nozzle would be in the range of the F-1 engine. So you would need a power source producing around 23 gigawatts to match the power output of the F-1. That's just a little bit higher than the power output of the largest hydroelectric dam in the world, the Three Gorges. You would then need a way to convert all the power output of that dam into light and somehow focus that light into a 5-meter-wide circle, and boom, there you go. -
My only mention of you in my last post was to say that you seem like a nice fellow and I would happily buy you a beverage of your choosing.
-
We know precious little and it is intensely annoying. Tory Bruno told me a few weeks ago that reuse is all still in dev and totally planned but we don't have any idea when it will be implemented, if ever.
-
Wellllll looks like I'm going to be liquidating those assets.
-
Mission To Mars Scifi Challenge
sevenperforce replied to Spacescifi's topic in Science & Spaceflight
To be clear, it is MORE than good enough. You can colonize Mars and the Moon using current tech easily enough, if you can get Congress to fund it. You don't need a nuclear saltwater rocket. That being said, Zubrin's 13 meganewton design would boast about 0.8 terawatts of power at full thrust. So yeah, if you could make the NIF laser fire continuously through the portal, then you could produce a power output 625 greater than Zubrin's design. But of course you can't make the NIF laser fire continously, so......????? -
Blue Origin could set itself up as the more conservative alternative to the Starship launch system, by sacrificing the fairing. Starship is designed to be fully reusable in every extent, but that results in some issues related to payload integration, because it is simply too big. Blue Origin could redesign its BE-3U upper stage to be partially reusable. It would blow the expendable fairing, complete orbital insertion, release the payload, perform the deorbit burn, drop the PAF, and re-enter like the X-37B. Glide back down to any runway. An open expander cycle should give at least 435s of Isp, which is a huge flex.
-
I will say again what I said before: I appreciate your reasoned approach to these questions. It is helpful. As @SunlitZelkova pointed out, this politicization was not unexpected. [Snip] As a person who has been on both sides of the science denial world and has spend the better part of his entire life dealing with science denial, I don't give much credence to "respectful" skepticism that lacks facts, evidence, or maths. Again, that's not a personal criticism in any way. I am sure @GoSlash27 is a lovely person and I would readily buy him any adult beverage of his choosing, given the opportunity. But I know what science denial looks like, and this is it. I can honestly say I have never seen any degreed climate change "activist" argue that climate change processes are more rapid than the decade-to-centuries timescale. It's about perspective. It's about probabilities. This is the more common perspective I have seen: There is a 10% chance of a rapid, runaway, cataclysmic climate shift due to accumulating factors which will cause global catastrophe and millions of deaths within a single decade. There is a 75% chance of a long-term cataclysm to our planet that will cause millions of deaths over the next half-century. There is a 15% chance that factors we don't yet fully understand will delay the cataclysm by a century or so. There is a 0% chance that inaction will avert ultimate cataclysm. That is the approach most people in this world take. It is a fairly honest and straightforward approach. It is serious. This is a very big deal. I will very gently posit that this is a strawman. I have never seen anyone with a graduate degree advocate subsistence farming for all humans. Not even once. I honestly don't think I have ever suggested that "sudden, cataclysmic collapse" is some inevitable immediate reality. If I ever have, I emphatically and wholeheartedly retract. There is a small (but nonzero) probability of a sudden and cataclysmic collapse. My understanding of the science is that this probability is very low. I am not worried about a sudden collapse. I am worried about what happens if we continue to do nothing for the next half-century. One of our major concerns is that while the rank and file humans are concerned about cutting their own personal emissions, the rich and powerful who control governments continue to avoid accountability for the industrial systems that dominate carbon emissions. Good question! Our obsession with oil transcends oceanic boundaries, so we're almost certainly going to keep tapping the oceans for oil and tapping the land for gas regardless of where the boundaries are. We need to get a better power grid focused on nuclear energy with wind and solar supplements so that it becomes economical to crack water into hydrolox (or to crack CO2 and water into methane via the Sabatier process). I appreciate this. And agree.
-
Can you repost the above in the dedicated thread?
-
Oh, it is just a term I coined myself a while back. A variant of the Gish Gallup as well as the burden-shifting fallacy. But I encourage you to use it!
-
Mission To Mars Scifi Challenge
sevenperforce replied to Spacescifi's topic in Science & Spaceflight
Yeah, now that I check the math, it seems you would need something with more umph to compete with a nuclear thermal rocket. The NERVA XE Prime had a total dry mass of 18 tonnes and it produced over 1000 MW. It’s physics-breaking so it is better than a nuclear saltwater rocket in that sense, but as described it would be nigh-impossible to get the kind of thrust or specific impulse out of it that Zubrin’s dragon breath rocket can boast. -
Mission To Mars Scifi Challenge
sevenperforce replied to Spacescifi's topic in Science & Spaceflight
No need; just let the propellant be your coolant. It heats up before entering the chamber, then heats up more in the chamber before being expelled. No radiator fins required. If the portals have the same melting point as tungsten then they can readily survive being in orbit around the sun with the same perihelion as the Parker Solar Probe, or evening closer. At that distance, solar insolation is 625 times higher than it is on the hottest summer day on Earth. That’s a terrific energy source. We would basically be building a Dyson swarm and we would rapidly solve all energy problems on Earth. I am in no mood to do the math now, but I strongly suspect a five-meter-diameter three-tonne photon portal would allow you to build a LOX-afterburning methane thermal rocket with extremely high specific impulse and absolutely acceptable TWR. -
Mission To Mars Scifi Challenge
sevenperforce replied to Spacescifi's topic in Science & Spaceflight
If you don't wish to play along fine. Just invented the scenario to see if we could cheat an NSWR using a contineous terawatt laser on propellant rocketry or not. Oh, I absolutely would love to play along. I was being snarky. I just need to know whether these are portals with an area of five square meters or a diameter of five meters. It makes a big difference. Also, how much does each portal weigh? Also very important. Are the portals indestructible? Because if they are, I propose yeeting them into a low solar orbit. Put the pair portal underwater in the ocean and run a steam turbine. Absolutely massive power production capability. Unlimited free energy everywhere within 100 miles of any major body of water. Of course we will probably be contributing to anthropogenic climate change at that point, but we can stop using fossil fuels, so that should help. You don't need a laser at all because the light doesn't need to be coherent. You mount one portal inside some super hot industrial furnace. You mount the other portal inside your combustion chamber and pipe liquid hydrogen directly into the chamber. Not a torchship, but close enough to one that we can easily colonize half a dozen worlds within fifty years. I will say for the record that if you allow for lightspeed delay and a few other things, I **think** that you could create pair portals like this without violating any of the laws of physics. Obviously we don't know of any way to create one, but a black-box pair portal that allows radiation transmission as described wouldn't necessarily violate any laws. It would make for a cool science fiction story if some social media mogul tried to create "instant communication" portals using entangled particles so that you could have a "window" into another part of the world, and then someone clever thought about using them for energy transfer. -
It won't. The 'wobble' is measured in decades. It's part of a cycle that we've been aware of for a looong time. Most people don't think in terms of decades. For the last decade (approximately) the rise in sea levels caused by anthropogenic climate change has been "hidden" by a cycle of decreasing lunar tides. If the average sea level is rising, but the average high tide is dropping, then it looks like the total sea level isn't getting much higher at all. But for the next decade (approximately) the cycle of lunar tides will be increasing. And so not only will the last decade's worth of sea level rise show up, but we're also going to be seeing the next decade's worth of sea level rise, AND we're going to get higher average high tides.
-
GOOD QUESTION! So, originally a Mars-sized protoplanet called Theia slammed into proto-Earth KABOOM Chunks of rock went flying off of the crust as the cores of Theia and proto-Earth merged LOADS AND LOADS OF FIRE AND LAVA The chunks of rock that were flung off the crust formed rings which were basically aligned around Earth's equator. Those rocks all eventually collided and coalesced into our moon. Our moon was massively larger than any other moon in the solar system (relative to its primary). Its massive tidal interactions with Earth (and Earth's tidal interactions with it) caused it to recede and become tidally locked. BILLIONS OF YEARS PASS Over time, our moon moved farther and farther away and became more and more affected by the gravity of the sun. Fairly early in the process, our moon became far enough away that it no longer "circled" the Earth at all; it was more affected by the gravity of the sun than the gravity of the Earth. The impact of the sun's gravity tugged the moon away from its original orbit around Earth's equator into an orbit that was closer to a flat orbit around the sun. But it's not quite there yet, so for the time being, there is an 18.6-year "wobble" in the lunar cycle from where it aligns with the Earth's equator to where it doesn't. Due to the inclination of the moon's orbit, there are only certain times of the month when you can do a minimal-energy Trans-Lunar Injection burn. You can do it at other times of the month but it costs more propellant.
-
Mission To Mars Scifi Challenge
sevenperforce replied to Spacescifi's topic in Science & Spaceflight
If the aliens are giving us photon portals with an area in units of distance1, we already have a big problem because apparently these are two-dimensional aliens who use volume to denote area and area to denote distance. -
No, bias correction is a term used in statistical analysis in reference to model adjustment. Bias correction is not applied to historical data. The fact that you use the term "bias correction" in reference to supposed "adjustments" to historical data shows that you do not know what bias correction is. Historical data are not subject to bias correction. Historical data can be subject to renormalization. For example, let us suppose that I am counting up the number of traffic fatalities in my city over the past few years. The set of fatal car accidents from 2015 to 2019 in my city looks like this: 2015: 19 2016: 17 2017: 22 2018: 20 2019: 23 The average across these five years is 20.2 traffic fatalities per year. Thus, the normalized difference from the average is as follows: 2015: -5.9% 2016: -15.8% 2017: +8.91% 2018: -1.0% 2019: +13.9% A year passes, and I find out that in 2020, there were 14 traffic fatalities. This means that the average is now 19.3 traffic fatalities per year, and so the renormalized difference from the average becomes: 2015: -1.6% 2016: -11.9% 2017: +14.0% 2018: +3.6% 2019: +19.2% 2020: -27.5% OMG THE NUMBERS CHANGED WHAT HAPPENED!!!!111!!!1!!11!!! It's just math, y'all.
-
These are very definite and specific claims relating to your concrete knowledge which would be very easy to demonstrate with minimal effort on your part. Please provide some evidence for your claims. Thanks, but no thanks. I have told you I don't know how many times and different ways now that I'm not trying to convince you of anything. If you want to go digging down that particular rabbit hole, then you will. This is the drive-by fallacy, a subset of argumentum ad ignorantium. Drive by, firing bold claims haphazardly out the window at pedestrians, then speed off before anyone thinks to ask you to provide any evidence. Perhaps, the driver thinks, some of the shots will find fertile ground in the torsos of innocent onlookers. It is a fallacy because it appeals to the common human intuition that claims are not made unless there is evidence for them, and thus the claim seems to have grounding specifically because it was made without citing evidence. Of course, claims are often made without any evidence at all, but humans forget about that. And we know this is not a good-faith argument, because if you weren't trying to convince anyone of anything, you wouldn't be speeding by with a spray of rapid-fire claims. I don't agree with you on everything but I always appreciate your inquisitiveness and desire to find the truth. Unfortunately, @GoSlash27 doesn't have any data or source material; he's repeating an argument he found convincing even though he hasn't seen any evidence for it. I don't say that as a personal attack; it's just a fact. I grew up creationist and I am very, very familiar with science denial. I am, in fact, a recognized and published expert in the area of science denial. And this is just a repetition of science denial. Do you know what Temperature Anomaly is? Simple answer. Yes or no. Because those graphs show the exact same data. Correct. If you change the size of the Y-axis in a graph, you end up with vertical distortion. It's the exact same graph, though. The difference in the scale of the Y-axis is partly due to the size of the graph and partly due to the fact that the graph is measuring Temperature Anomaly, not temperature alone. It looks like that, but it's not -- the left red circle is in the exact same location relative to the mean temperature anomaly, but the averaging line in the 2001 version is truncated at around t=1885 while the averaging line in the 2015 version goes all the way back to 1880. Also, the averaging line is a moving average, which is going to be in part an artifact of the size of the graph. As @mikegarrison explained upthread, "When you get more data it changes the running average at the end of the previous line, because that's what a running average does." I will note that I have yet to see any evidence whatsoever of this. Fifty years ago, not forty. And even then, no. There was one Science article in 1971 suggesting global cooling as a result of aerosols which was corrected by its own author in 1975. Some media outlets in the early 1970s chattered about it, leading to a handful of headlines. But the science on anthropogenic, warming-dominated climate change was already well-established. Well, nuclear winter was definitely a possible issue. It is still a possible issue. But it has nothing to do with the current trend of anthropogenic climate change. And that is why I asked @GoSlash27 to show me his data. I always, always ask for the data.
-
These are very definite and specific claims relating to your concrete knowledge which would be very easy to demonstrate with minimal effort on your part. Please provide some evidence for your claims.
-
And to preclude any confusion over the variations between 1750 and 1850: (a) The data back then was much less precise so the error bars are larger (b) Look what happens when you line up observed solar activity across the same period:
-
This claim is plainly and demonstrably incorrect. And that's not a graphic I found somewhere online. I went to the actual source data from Berkeley Earth, downloaded the .txt datasets, converted them into CSV, and loaded them into Excel myself. These data are not "corrected" or "altered" or "normalized" or "adjusted" in any way. They are the raw, unedited data. Here's the ten-year average if you want to see that: The Earth is warming. It is obviously and incontrovertibly warming. Insisting otherwise isn't skepticism; it's sticking your head in the sand.
-
totm nov 2023 SpaceX Discussion Thread
sevenperforce replied to Skylon's topic in Science & Spaceflight
Another possibility is that those are smaller to avoid accidentally placing regular tiles on those points, although I would think going upside down would fix that anyway. -
totm nov 2023 SpaceX Discussion Thread
sevenperforce replied to Skylon's topic in Science & Spaceflight
Some excellent person on NSF did a visual representation of the above: It looks from this like the inverted (green) stud triangles are smaller than the rest, but it is hard to tell for sure.