JoeSchmuckatelli Posted February 11 Share Posted February 11 On 2/11/2025 at 2:24 PM, farmerben said: Diesel fuel has 44 times more energy/kg compared to lithium ion batteries. That is 4400% better. *correction its not that much better because the conversion of thermal power to shaft power is around 40%, whereas electric battery combos are closer to 90% Expand Oh yeah - trust me I was also thinking about ways to capture the heat and convert to electricity... But it's the same problem = adding weight + inefficiency. Quote Link to comment Share on other sites More sharing options...
magnemoe Posted February 11 Share Posted February 11 On 2/11/2025 at 12:10 PM, farmerben said: Taking the motion of a shaft into electricity and then back into a shaft involves losses. What percentage is lost I'm not sure but 10% is quite significant. It makes the most sense if you stagger the inputs and outputs in time. A hybrid that stops and starts frequently and has good batteries is ideal. If you need to motor continuously for many hours than basic diesel powered shaft is going to be more efficient than hybrid. Expand Now diesel electric locomotives have no batteries but guess the zero rpm torque and many driving wheels makes this preferable. Else hybrids are nice you getting the best of both worlds. Fun fact the US made steam turbine electrical battleships, the problem was that they had issues with geared turbines so using generators and motors worked. It had the benefit of not needing an long drive shaft and that you could route power easy. Say you lost the left propeller and the right engine, just have the left engine drive the right propeller. Downside was losses and the fun of high power electricity and sea water if you took damage. Quote Link to comment Share on other sites More sharing options...
magnemoe Posted February 11 Share Posted February 11 On 2/11/2025 at 5:48 AM, razark said: https://en.wikipedia.org/wiki/List_of_oldest_extant_buildings Expand Looking at some very sad looking pyramids Stuff who get buried survive much better unless its massive and / or build of huge stones. One thing who would survive for up to billions of years would be mines, yes they will be filled with mud who become stone but that its an old mine would be pretty obvious. More fun thick steel structures like the stuff holding up the roof and railroad track would fossilize easy compared to bones as it take much longer to break down. And it should be iron here, instead we find this weird stuff. Also stuff like ceramics don't break down more than stone if buried. Silurian hypnosis debunked. Yes they could be stone age, people find stone tools all the time, mostly arrowheads as they was semi disposable. Quote Link to comment Share on other sites More sharing options...
farmerben Posted February 11 Share Posted February 11 Edenborough, Scotland is built mostly of granite blocks over a foot thick. I'll bet on it as the city that changes the least in the next 1000 years. Quote Link to comment Share on other sites More sharing options...
darthgently Posted February 18 Share Posted February 18 On 2/11/2025 at 2:56 PM, JoeSchmuckatelli said: Oh yeah - trust me I was also thinking about ways to capture the heat and convert to electricity... But it's the same problem = adding weight + inefficiency. Expand We already do make use of the excess heat in smallish ways. Cabin heating and defrost in an ICE vehicle is taken for granted. I would not own a Tesla, for example, in a blizzard prone area in winter without a small diesel cabin heater and a few gallons of diesel for battery emergencies. Here is a cheap Asian knockoff of what I’m thinking of but the $elect $pecial brand name$ are: Webasco and Eberspracher https://www.amazon.com/ChuBu-12V-24V-Upraded-Consumption-Heating/dp/B0C696B6V2/ref=mp_s_a_1_5?sr=8-5 Quote Link to comment Share on other sites More sharing options...
magnemoe Posted February 18 Share Posted February 18 On 2/11/2025 at 2:56 PM, JoeSchmuckatelli said: Oh yeah - trust me I was also thinking about ways to capture the heat and convert to electricity... But it's the same problem = adding weight + inefficiency. Expand We have two ways of doing this first is a steam turbine, second is thermocouples, later is less effective than steam engines but has no moving parts. Make an thermocouple with an efficiency as an steam engine. Quote Link to comment Share on other sites More sharing options...
farmerben Posted February 19 Share Posted February 19 (edited) What is your favorite type of nuclear reactor. I think the US should be building breeder reactors like EBR II and LFTR. For export purposes to perhaps unstable parts of the world I recommend CANDU because there is no fuel enrichment or reprocessing. There has been sensational news that CANDUs leak tritium into the atmosphere. But that is so miniscule I don't care. Currently the AP1000 Westinghouse reactor might be the most economical. It is a pressurized light water reactor. Edited February 19 by farmerben Quote Link to comment Share on other sites More sharing options...
DDE Posted February 19 Share Posted February 19 On 2/19/2025 at 1:23 PM, farmerben said: What is your favorite type of nuclear reactor Expand BREST-OD-300 (fast neutron, lead-cooled)of Project Breakthrough for the sheer madness of coming bundled with its own on-site fuel fabrication facility. Yep, it's a breeder. Late-model VVERs have sold like ice cream in July, comparatively speaking. On 2/19/2025 at 1:23 PM, farmerben said: For export purposes to perhaps unstable parts of the world I recommend CANDU because there is no fuel enrichment or reprocessing. Expand Truly unstable parts of the world tend to be too unstable for a large, long-term project in the first place. That's why the various mobile options might be a simpler way, and putting them on a barge expedites a lot of politics. Yeah, I'm talking about Akademik Lomonosov. Quote Link to comment Share on other sites More sharing options...
DDE Posted February 20 Share Posted February 20 Russian Academy of Sciences petitions for a new HAARP-style system to replace Sura https://iz.ru/1841985/2025-02-20/v-rossii-postroat-superantennu-dla-izucenia-kosmiceskoi-pogody 60 antennae in 700 m x 700 m grid, 2,5-6 MHz, effective power 900 MWt How does it compare to HAARP - because I'm seeing givawatt claims for an array that is a fourth of the size - and how excited should the tin foil salesmen be? Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted March 13 Share Posted March 13 Is the shadow of the moon on earth during an eclipse smaller in diameter than the moon itself? I'm thinking it would have to be, given that the sun isn't a point light source. Quote Link to comment Share on other sites More sharing options...
Terwin Posted March 13 Share Posted March 13 Depends on if you count the 'partial eclipse's shadow(larger than moon) or just the full eclipse part of the shadow(smaller than moon) Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted March 13 Share Posted March 13 On 3/13/2025 at 7:04 PM, Terwin said: Depends on if you count the 'partial eclipse's shadow(larger than moon) or just the full eclipse part of the shadow(smaller than moon) Expand I think that would be true for a point light source. However, given that the sun is much larger (and despite the distance) we almost have to assume that the penumbra might actually lightly shade inside the actual diameter Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted March 13 Share Posted March 13 Ofc - I could be glaringly wrong abt this! Quote Link to comment Share on other sites More sharing options...
monophonic Posted March 14 Share Posted March 14 Here's what @Terwin wrote in picture form. (Except this one shows the Earth, but the shadow regions are the same.) (Qarnos, Public domain, via Wikimedia Commons) As you can see, penumbra (partial shadow) is larger than the Moon, but the umbra (full shadow) is smaller. And sometimes the Moon is far enough from the Earth that it does not completely cover the Sun. Then we get an annular eclipse, without any full shadow at all. Quote Link to comment Share on other sites More sharing options...
AckSed Posted Wednesday at 01:26 AM Share Posted Wednesday at 01:26 AM So I have been watching Mobile Suit Gundam from the start - slowly, one episode a week - and the whole thing started as essentially an attempt at semi-hard SF. Zero-gravity manoeuvering, no artificial gravity, spacesuits with jetpacks, special recoil-reducing rifles, everything drunk through a straw or pouch and of course the O' Neill Cylinders at the "Sides" i.e. Lagrange Points (Pay no attention to the psionics, everyone was doing it in the 70s; they really thought it was a thing for a while. Childhood's End, anyone? Gundams? Look, I am allowed one treat.) Point is, I'm into Zeta (sequel to original season) and, in ep. 7 for the first time we actually see a diagram with Earth-Moon Lagrange points, the O' Neill Cylinders situated at EML2, L1, L4 and L5 and the parabolic paths one side is expecting the other side to follow. (Eee!) According to this, EML2 is stable. But how much delta-V would be needed for station-keeping at EML4 and EML5? Quote Link to comment Share on other sites More sharing options...
darthgently Posted Wednesday at 04:44 AM Share Posted Wednesday at 04:44 AM On 3/19/2025 at 1:26 AM, AckSed said: So I have been watching Mobile Suit Gundam from the start - slowly, one episode a week - and the whole thing started as essentially an attempt at semi-hard SF. Zero-gravity manoeuvering, no artificial gravity, spacesuits with jetpacks, special recoil-reducing rifles, everything drunk through a straw or pouch and of course the O' Neill Cylinders at the "Sides" i.e. Lagrange Points (Pay no attention to the psionics, everyone was doing it in the 70s; they really thought it was a thing for a while. Childhood's End, anyone? Gundams? Look, I am allowed one treat.) Point is, I'm into Zeta (sequel to original season) and, in ep. 7 for the first time we actually see a diagram with Earth-Moon Lagrange points, the O' Neill Cylinders situated at EML2, L1, L4 and L5 and the parabolic paths one side is expecting the other side to follow. (Eee!) According to this, EML2 is stable. But how much delta-V would be needed for station-keeping at EML4 and EML5? Expand I thought L1, 2, &3 were unstable saddles and L4,5 were stable Quote Link to comment Share on other sites More sharing options...
magnemoe Posted Wednesday at 08:06 AM Share Posted Wednesday at 08:06 AM On 3/19/2025 at 4:44 AM, darthgently said: I thought L1, 2, &3 were unstable saddles and L4,5 were stable Expand Yes L4 and 5 is stable, L1,2 and 3 is not but it don't require much to stay in them or even orbit around them like web does. But it require some as web life is determined by its fuel. And its was extended by the very precise injection burn. Quote Link to comment Share on other sites More sharing options...
darthgently Posted Wednesday at 11:44 AM Share Posted Wednesday at 11:44 AM On 3/19/2025 at 1:26 AM, AckSed said: But how much delta-V would be needed for station-keeping at EML4 and EML5? Expand None for L4 and L5 if done correctly Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.