danielravennest


























  1. Those sparks are not responsible for lighting the rocket's engines. They are responsible for burning the hydrogen that escapes from the nozzles during startup procedure so it doesn't accumulate and explode.

  2. For the SRB, it is more complicated than that. There are three pyrotechnic charges at the top (for redundancy). The flame from those lights a 6 inch solid motor with a "fast burn" fuel mix. The flame from the 6 inch solid lights a 48 inch solid motor which also has a fast burn mix. The 170 foot flame from that motor is what lights the main solid fuel grain.

  3. Not "there will be" -- "there could have been" is what the water means, but we already knew there was water. and no it's not habitable, not on its own.

  4. 86% of the Earth isn't habitable for humans without technology. That's the oceans, deserts, and ice caps. Mars just takes more technology, and less than space stations and submarines which we already have.

  5. Mars takes way, way, way more technology to sustain humans than submarines. Space stations too. Unless your idea of habitable is dying of radiation poisoning after getting there.

  6. I helped design and build the ISS when I worked for Boeing, and the Martian surface is easier conditions than vacuum.

  7. Why weren't we doing this all along?

  8. Wind became competitive with coal in the US around 2011, and solar in 2013. So we just didn't build much of them before that. Since 2012 their combined output has grown by four times, but that still is only 15% of total US electric supply.

  9. Maybe in the future we can use that instead of taking water from Earth for space exploration supplies.

  10. There's plenty of water already in space. Some nearby asteroid types contain up to 20% water and carbon compounds. The carbon compounds typically have hydrogen, and that can be combined with mineral oxides (most rocks) to make more water.

  11. The exhaust from a rocket is basically unusable as a source of water for astronauts. Every drop of water you take from the exhaust, too, would be reducing the rocket's efficiency. In order for that rocket to work, you need all those combustion products to fly out the back of the nozzle at high speed. Anything you put in the exhaust stream that is attached to the ship is going to reduce the effective thrust of the rocket (assuming it doesn't just melt first). You'd be better off just already having a water storage tank on the spacecraft, but then we get back to the original problem.

  12. I was responding to the "taking water from Earth" part of the previous comment. The exhaust from a rocket launch to orbit stays in the atmosphere.

  13. On the down side they have to drink massive amounts of coffee when they wake up, and keep asking "what year is it?"

  14. But, but, muh clean coal!! /s

  15. I used to do blacksmithing as a hobby, with coal. Clean coal is a lie. It's dirty nasty stuff. I used it because I got two tons of coal free.

  16. Also the "learning curve". If you do the same thing 750 million times a year (about the world's production of solar panels in 2022), you get pretty good at it. You figure out ways to do it more efficiently and cheaper.

  17. Lol, still enough for a trip to heaven. I guess when oil becomes rarer and people start randomly digging in their fields, we might someday see an interesting video on liveleak.

  18. Ships and tanks will still run fuel. No way those are becoming battery based.

  19. For my education is there a city of over a million people that’s 100% powered by wind and solar? And if not why is that? Hydro and geothermal only work in specific places

  20. [EDIT: this is incorrect]The Netherlands was powered 92% by wind and 8% by solar in 2016 (16 million people).

  21. Could you elaborate on what you mean, and point to the data you base your statement on? Because according to the

  22. I made a mistake and read the wrong data off a table. Thanks for catching it. Based on

  23. Would it be tho? What do you do with all the solar panels and other equipment components when they hit their EOL? No one is addressing this massive future problem. Just like EV batteries. What’s the plan when they die? It’ll be ,”Oh look! Another self inflicted crisis! Yay!”

  24. I see. So how much energy does it require to separate and then recycle those components on such a large scale? And where does that technology exist currently to deal with that?

  25. Solar panel recycling hasn't really started yet. Current panels come with a 30 year warranty to produce at least 80% of rated power, and have a loss rate of 0.5% per year. The oldest panels being field tested by the Department of Energy from the mid-1970's (50 years old) are still running, but at lower output.

  26. Ok, so the x-axis on this chart is earth's age (in Ma or Mega-annum i.e. Million year increments) and the y-axis is the rotational speed measured in hours to complete one full rotation. The "tao nought" in the legend refers to distance to the Moon and the various plotted black points (some with the confidence intervals) appear to show observed data.

  27. Temperature drops are "snowball earth" events, where the oceans froze. There are no tides, and therefore reduced tidal forces slowing rotation. Squiggly line from 800 to 2600 Mya was a tidal resonance. The tidal period happened to match the rotation period, so the Moon stopped moving away and the Earth stopped slowing down for a while.

  28. Fascinating. So I'm guessing super tides occur when the moon and sun line up? I had no idea the Sun's pull on the oceans was so strong but makes sense given its gravitational pull on earth.

  29. Usually, through fudging renovations you paid for with cash, but there is a multitude of different ways of doing it. You cant, generally, buy real estate with cash outside of private mortgages, but you can do hefty upgrades and renovations with cash. Contractors will often even ask for cash, as on their side of things they also claim less for tax reasons

  30. I don't think the commentor above you was trying to act superior or anything. A lot of people thought Elon was the "savior" billionaire that would help pioneer new industries and move society forward. There's no shame in being wrong, especially if you are willing to change your views when presented with new information.

  31. His L.A. rocket factory was also the location for "Hammer Technology" where Ivan Vanko was making "drone better".

  32. All the offices can become apartments.

  33. It would require significant renovation. Office buildings don't generally have private bathrooms and kitchens, and large ones don't have many windows per person.

  34. I haven't run the numbers on basic water, sewer, and electricity needs for residential vs office per square foot, but I would not be surprised if they were different.

  35. Again, the juice is simply not worth the squeeze. You're adding nuclear complexity to every launch (nobody wants a dirty bomb going off in the sky) and you're just not getting significant benefits. You're still going to run out of propellant after an X minute burn. And now you're stuck with a super complex, hazardous, expensive boat anchor on your space craft that's VERY hard to cool because you only have radiation as conduction and convection don't exist in space.

  36. Right, and I'm a SUPER spaceman Thunderbirds engineer.

  37. Cleveland cliffs have electric arc furnaces that are significantly better than the old style. I'm not sure if it is the same tech or better

  38. Electric arc furnaces are for remelting scrap iron to make new steel. About half of US steel production is remelted scrap. The other half has to come from a "reduction" furnace that removes oxygen from iron ore. Historically this was a blast furnace, but Boston Metal has a different process.

  39. If the question was "how can I get really expensive electricity in 14 years", then yes nuclear is the answer. 14 years is the Vogtle 3 & 4 reactors in Georgia, approved in 2009, supposed to be operational this year.

  40. I don't have enough expertise to judge why the USA has such a high murder rate, i assume it's a bunch of factors. I'm sure environment plays a role, and ease of acquiring weapons that make killing relatively easy is also likely a part of it.

  41. Wow, learning something new every day. Odd rule though, surely there must be a good reason

  42. There are other subreddits for astrophotography, so this one limits photos to 1 day a week to allow more room for general space news.

  43. & yet none of them know. Coz it’s a mild cold or flu at best. It’s time to get on with our lives. Stop paying attention to fear porn.

  44. Thank you for sharing your experience! Beat Saber, I’m going to Google that. I quit smoking cigarettes 4 years ago, but I replaced it with Thrive chewing gum (the kind you use to quit smoking) and whiskey. I quit drinking in November, replaced pop with water the week before last and am on day nine of no gum. It’s been a tough road but it isn’t done yet. Haven’t ran for over a month now and I can’t seem to get the motivation to. Always hated every second of it though. Time to find something I can enjoy and stick to!

  45. how does he control it though? are there some ... sensors or actuators?

  46. He has fingers, just not fully formed and normal length. I think the prosthetic just extends the fingers and moves them when he moves his "stubs".

  47. "Stubs" lol. I believe you'll find the medical term for that is "nubs".

  48. Matter can absolutely be destroyed, E=mc² tells us that.

  49. The amount of solar energy that reaches the top of the Earth's atmosphere is 10,000 times as much as our civilization uses. With a small fraction of that we absolutely could recover all the "waste products" and return them to usable form. In the US, 80-90% of scrap steel gets recycled. We just don't do as well with other materials.

  50. Im curious to see a source on that.

  51. Radius of the Earth is 6378 km. Add 12 km to give the effective height of the atmosphere, so r = 6390 km. Cross-sectional area of a circle with that radius is 128,278,000 km2.

  52. "There are actually things worse than CO2 for the environment and RE and other mineral mining is one of them. "

  53. Sorry, my is a slight misrepresentation. The typical design that people site for Thorium is a molten salt reactor. The Lithium salt used by said reactors highly corrosive thus requiring frequent replacement of the reaction vessel.

  54. I think I have 3 FCs within a 15 mile radius and the amount of stuff I get same day/overnight is crazy. Sucks to hear it’s getting worse for others.

  55. I didn't know it ahead of time when I bought this house, but my town has an "intermodal center" (where they move stuff from rail to truck and the other way), and therefore a ton of warehouses. We have like 5 Amazon warehouses in the area. So my stuff is regularly a day early. I feel for people in the opposite situation.

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