KG3

It seems to me that in all the of the animations of nuclear reentry vehicles that I've seen the warhead had been shaped like a cone and traveled into the atmosphere point first. How does a sphere-cone-flare work and look like? Does KSP have anything like this to play around with? I just loved Fractured Fairy Tails as a kid although those Bullwinkle cartoons were actually made more for an adult audience.

Never heard of the yo-yo de-spin. Looks like a very elegant solution though. The paper talks about a stretch yo-yo system that compensates "to a reasonable degree" for variations spin rates. The faster the vehicle spins the more centripetal force there is on the yo-yo, the longer the chords stretch and more inertia is removed from the vehicle. Clever and simple! I can't quite picture how the yo-weight works on the spent solid rocket boosters. It somehow makes the spent booster tumble and not crash into the upper stage from residual thrust.

Hello, I have a question about this video. It's about getting the exploration rovers to mars from way back in 2006. About a minute and 15 seconds in it shows the vehicle separating from the upper stage of the rocket. Then it fires more rockets to make the vehicle spin presumably to stabilize it for the last engine to fire and send it on it's way to Mars. Then it looks like two weights on the ends of strings spool out from the sides to slow down the vehicles spin. Does anyone know why they used weights on strings for this? I saw a video recently where they were testing a new parachute in the Earths upper atmosphere in which they used rocket motors to spin the vehicle then just used another set of rocket motors pointing the opposite direction to stop the spin after the main engine shut off.

I think DDE is asking about the electrically conductive channels of ionized gas that occur during lightning. https://en.wikipedia.org/wiki/Lightning#Lightning_leaders In a process not well understood, a bidirectional channel of ionized air, called a "leader", is initiated between oppositely-charged regions in a thundercloud. I think the zap won't work if your target is in a car, wearing tinfoil or using some other kind of Faraday cage type thing. I think you also need a high electrical potential between your weapon and target.

That's quite a piece of glass! I tried grinding a 6" mirror years ago. It got stuck to the pitch lap, I panicked and tried to pry the mirror off. It popped off, went flying across the room and smashed on the floor and that was that. So how do you choose eyepieces? I seem to recall different eye pieces work better with different focal lengths but I can't recall how or why. Nice work though!

So what's the biggest problem, getting rid of waste heat?

Just a question about the concept of putting a turbine into space. What would having such a large rotating mass do for the stability of the spacecraft? Wouldn't you need two counter rotating turbines? Or maybe this system in intended to by landed and secured to a much larger body like a moon or asteroid?

I never thought of that. Pit Vipers can see IR. They can't see IR with their eyes, they use a completely different organ. https://en.wikipedia.org/wiki/Loreal_pit The loreal pit is the deep depression, or fossa, in the loreal area on either side of the head in crotaline snakes (pitvipers). It is located behind the nostril and in front of the eye, but below the line that runs between the centers of each. It is the external opening to an extremely sensitive infrared detecting organ. The loreal pit is bordered by lacunal scales.The loreal pit is thermal regulating system. Pitvipers maintain their temperature of body through loreal pit. Good thing they are cold blooded. They need to be colder than their prey or they would blind themselves.

This is true, the aluminum that I've had the misfortune to over heat kind of just turned into a mealy mush and lost it's structural integrity when cooled. I believe all of the aluminum horseshoes I've come across are cast not forged. It seems like all the different manufacturers have their own secret recipe as far as the alloy goes. We tend to work these shoes cold because heating them seems to ruin whatever tempering they do at the factory and because it's not too hard to just smack them into shape cold with a hammer.

I think you would need to get more specific about what you were mining for. Are you trying to get water, iron and nickel, gold, iridium, carbon, Sulphur? Some asteroids are somewhat solid and some are just piles of rubble that you could probably take apart with a spoon. And then there is size, some asteroids are just meters across some are kilometers. This looks interesting from Wikipedia: https://en.wikipedia.org/wiki/Asteroid_mining Extraction using the Mond process The nickel and iron of an iron rich asteroid could be extracted by the Mond process. This involves passing carbon monoxide over the asteroid at a temperature between 50 and 60 °C, then nickel and iron can be removed from the gas again at higher temperatures, perhaps in an attached printer, and platinum, gold etc. left as a residue. You might find that you will need to mine carbon monoxide from a comet to process material from an iron asteroid!

I've tried making horseshoes out of aluminum bar stock. Tricky stuff. A propane gas forge runs about 1800 F. You put the bar stock in and count to about 15 then pull it out and check to see if you can work it. It's so easy to over heat the stuff. It goes from workable to a puddle in seconds. I've never seen any color (or glow) on it. Maybe in a very dark room?

I am a blacksmith. Rule of thumb around a forge is hot steel looks allot like cold steel. A horseshoe at a gray heat is still hot enough to take the skin off of you fingers. Also, I can't read small print easily at any temperature.

I didn't know this but it makes sense. A photon leaving the area near a black hole loses energy or is red shifted as it makes it's way out of the gravity well (general relativity). But a magnetic field line that originates near a black hole doesn't lose strength do to general relativity? My next question would have been something like can a black hole be so massive that even gravity can't escape but I think you answered that too! That one is a little like when George Carlin would ask the nuns at school "if god can do anything can he make a rock so big that he couldn't lift it." I can see why they want to get a good look at this object.

The first paper mentioned in a couple of places that magnetic field lines are anchored in the black hole. ".Within this scenario, the initial acceleration of the jet plasma to relativistic speeds is related to violent reconnection episodes between the magnetic field lines of the inner disk region and those that are anchored in the black hole." Doesn't the magnetic field disappear into the black hole along with the matter that produced it?

You are right but it does sound like a daunting task. It sounds like a very chaotic environment around a super massive black hole though. This part interests me: "....magnetorotational-instability-driven turbulence and magnetic reconnection in the accretion flow" What happens to magnetic fields when part of it falls beyond the event horizon? Is that why there is so much magnetic reconnection?

Well this part of the abstract doesn't sound good. " General relativistic magnetohydrodynamic (GRMHD) simulations show that radio emission from Sgr A* exhibits variability on timescales of minutes, much shorter than the duration of a typical VLBI imaging experiment, which usually takes several hours. A changing source structure during the observations, however, violates one of the basic assumptions needed for aperture synthesis in radio interferometry imaging to work." This is from the introduction. "...the emission region surrounding the black hole depends on the details of the underlying accretion process and is intrinsically time variable primarily due to the stochastic nature of magnetorotational-instability-driven turbulence and magnetic reconnection in the accretion flow" It sounds a little like they are trying to get a picture of a boxing match with a pin hole aperture camera.

I've been wondering if you could run a jet engine in an atmosphere that had fuel in it with a vehicle had the oxidizer stored in tanks. Maybe if you were on Saturn's moon Titan and flying through a cloud of Methane or something.

Nuclear weaponry might be a filter, however if civilization and to other solar systems we'd need a very good grasp of nuclear power and be able to deal with radiation too. Another possible filter is genetic engineering. Could make for some awful weapons but maybe needed for living in space if you are going to be making food and oxygen and other stuff. Migrations tend to follow resources. If everything available in the Oort cloud gets used up civilization might just follow space crumbs to another solar system. It might take tens of thousands of years or longer.

Are there any gasses that are denser than liquids so that if up together in a container the gas would bubble to the bottom? I'm not too concerned if the two can't actually exist in the same place at the same time because of temperature differences or because they wouldn't play nice together chemically. Like maybe Uranium hexafluoride put in liquid Hydrogen or Tungsten vapor mixed in liquid Helium or some such thing. It's just that there are so many solids that float on liquids why not a liquid that floats on a gas? I've been wondering about this for a while now.

Ok, so where are the ions coming from? Does the spacecraft need to bring a supply of xenon like a ion thruster? Could some kind of permanent magnet be uses to keep this ion cloud in place?

I had thought that the Apollo landing sites were protected somehow as historic landmarks and that tampering with them might be considered some sort of a crime but it looks like that is not the case. https://en.wikipedia.org/wiki/Tranquility_Base#Status "The U.S. National Park Service has declined to grant it National Historic Landmark status to avoid violating the Outer Space Treaty's prohibition on any nation claiming sovereignty over any extraterrestrial body. It has not been proposed as a World Heritage Site since the United Nations Educational, Scientific and Cultural Organization (UNESCO), which oversees that program, limits nations to submitting sites within their own borders." But I would like to see some of those lava tubes explored! https://en.wikipedia.org/wiki/Lunar_lava_tube#Observational_evidence "Gravitometric observations by the GRAIL spacecraft suggest the presence of lunar lava tubes with widths of over one kilometer. Assuming a width-to-height ratio of 3:1, such a structure can remain stable with a ceiling that is 2 meters thick. Lava tubes at least 500 m underground can theoretically remain stable with widths of up to 5 km."

I do think it's a good idea to at least look for life. It won't look good if it's out there in an obvious place where we could find it but we didn't bother to look. Just remember that it wasn't very long ago we were asking "are there planets around other stars?". It was assumed that there were but as far as we knew for sure there was just one star in the universe with planets. I'm just amazed at how scientists create ways to find things out. In the late 19th century astronomers claimed with great certainty that "we will never know what powers the sun"! Some clever person or persons will figure out how to tease out the signals of life elsewhere in the universe. I can't wait to see how they do it! This is why I love science.

I thought that maybe the author from Businessinsider.com who wrote the article about the mars 2020 rover might have gotten it confused with the Japanese Aerospace Exploration Agency's MMX (Marian Moon Exploration) sample and return mission of Phobos. https://en.wikipedia.org/wiki/Martian_Moons_Exploration But you are right, that was a stretch on my part. They do clearly say that a return mission is for some point in the future and is not part of the mars 2020 mission itself. They do seem to be a bit confused about how many rovers are on mars.

Maybe the author of the article was getting confused by this sample return mission. It seems like they don't know what they are talking about anyway and are getting more than one mission conflated somehow. Is there another sample retune mission planned for the surface of Mars? NASA has selected a science instrument for an upcoming Japan-led sample return mission to the moons of Mars planned for launch in 2024. The instrument, a sophisticated neutron and gamma-ray spectrograph, will help scientists resolve one of the most enduring mysteries of the Red Planet—when and how the small moons formed. The Mars Moons eXploration (MMX) mission is in development by the Japan Aerospace Exploration Agency (JAXA). MMX will visit the two Martian moons, Phobos and Deimos, land on the surface of Phobos, and collect a surface sample. Plans are for the sample to be returned to Earth in 2029. NASA is supporting the development of one of the spacecraft's suite of seven science instruments.

Something you seem to hear during interviews of people who witnessed above ground nuclear tests is something like "It was so bright I could see the bones of my hands". Does anybody know if this is actually a thing? I'm assuming that these are people who had covered their faces with their hands during the first seconds after detonation. Could the light have been that bright without their flesh bursting into flames? Maybe they were seeing an optical illusion of some kind? Could there have been enough x-rays emitted that they could be seen by the human retina? Maybe something caused the calcium in their bones to momentarily fluoresce. Or maybe one person just said it as an exaggeration and others repeated it just because it sounded cool.