Slam_Jones Posted February 16, 2018 Share Posted February 16, 2018 Just now, Steel said: I have a feeling that whoever did those calcs has a very poor grasp on physics. Anyway, they've missed the fact that the equation they've used gives then velocity squared, the the actual velocity is root(6159) which is about 78 m/s Yeah I figured it would be something like that. Thanks for the response! Quote Link to comment Share on other sites More sharing options...
raxo2222 Posted February 17, 2018 Share Posted February 17, 2018 What if asteroid made of pure ice was orbiting Earth in circular orbit of 90 km? Lets say asteroid is almost spherical and has radius somewhere from 100 meters to 10 kilometers. How long it would orbit until it crashes on Earth? How much mass would be ablated? Quote Link to comment Share on other sites More sharing options...
YNM Posted February 23, 2018 Share Posted February 23, 2018 I just noticed that the railway lines of Pacific Surfliner and Coast Starlight passes "through" Vandenberg SLC (well, at least 500 m from SLC 8 !). Is it possible, then, to watch a rocket launch from a train there ? XD Quote Link to comment Share on other sites More sharing options...
magnemoe Posted February 25, 2018 Share Posted February 25, 2018 On 23.2.2018 at 4:08 AM, YNM said: I just noticed that the railway lines of Pacific Surfliner and Coast Starlight passes "through" Vandenberg SLC (well, at least 500 m from SLC 8 !). Is it possible, then, to watch a rocket launch from a train there ? XD 500 meter is a bit short pretty sure they shut it down during launch so you might end up with the train in an stupid place like an tunnel or behind an warehouse during launch. Quote Link to comment Share on other sites More sharing options...
YNM Posted February 25, 2018 Share Posted February 25, 2018 (edited) 17 minutes ago, magnemoe said: 500 meter is a bit short pretty sure they shut it down during launch so you might end up with the train in an stupid place like an tunnel or behind an warehouse during launch. There are only a few trains passing through during the course of a day. Apparently none passes during the usual launch times for SSO missions (early morning and late dusk). The track is "owned" (?) by UP, so while the passenger timetable doesn't show anything I'm not sure for freight movements, though apparently freight rarely uses them either (alternative lines with better alignment (?) available further inland). It's just weird seeing a public railway soo close to a military installation. Not even KSC or CCAFS have them... It passes 500 m from SLC-8 (Minotaur etc.) and ~1 km from SLC-4 and 6 (Falcon and Delta). Edited February 25, 2018 by YNM Quote Link to comment Share on other sites More sharing options...
KG3 Posted February 25, 2018 Share Posted February 25, 2018 Question about things landing on Mars. This article from August 2009 has been in the back of my mind for almost 10 years. A meteorite the size of a large watermelon was found on the surface of Mars. https://www.nasa.gov/home/hqnews/2009/aug/HQ_09_186_Mars_meteorite.html The microscopic imager on the arm revealed a distinctive triangular pattern in Block Island's surface texture, matching a pattern common in iron-nickel meteorites found on Earth. "Normally this pattern is exposed when the meteorite is cut, polished and etched with acid," said Tim McCoy, a rover team member from the Smithsonian Institution in Washington. "Sometimes it shows up on the surface of meteorites that have been eroded by windblown sand in deserts, and that appears to be what we see with Block Island." "At about a half ton or more, Block Island is roughly 10 times as massive as Heat Shield Rock and several times too big to have landed intact without more braking than today's Martian atmosphere could provide. "Consideration of existing model results indicates a meteorite this size requires a thicker atmosphere," said rover team member Matt Golombek of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Either Mars has hidden reserves of carbon-dioxide ice that can supply large amounts of carbon-dioxide gas into the atmosphere during warm periods of more recent climate cycles, or Block Island fell billions of years ago." Please bear with me here. In this video from Demolition Ranch (a guy who really likes to shoot things with various guns to see what happens) he shoots at dry co2 ice with his .50 cal. BMG (he's particularly found of this gun) at about 3 min 30 seconds in (you can FF past his "bullet proof T-shirt" plug if you like). The dry ice explodes into a cloud of vapor like he had hoped for but https://www.youtube.com/watch?v=Cnvw_5JlIcs&t=34s instead of the bullet passing through the blocks of dry ice, the water melon and off into the woods (like the bullets that went through the safe in the background) it stopped at the dry ice. The bullet wasn't deformed at all but it did have the copper jacket scoured off! Is there something about dry ice that makes it particularly good at stopping and polishing projectiles? Could the Block Island meteorite have landed on dry ice which sublimated away leaving it sitting on the surface rather than travelling through a thicker atmosphere? I'm sure the meteorite was traveling much faster than the bullet. Quote Link to comment Share on other sites More sharing options...
Green Baron Posted February 25, 2018 Share Posted February 25, 2018 (edited) 1 hour ago, KG3 said: Could the Block Island meteorite have landed on dry ice which sublimated away leaving it sitting on the surface rather than travelling through a thicker atmosphere? I'm sure the meteorite was traveling much faster than the bullet. It would have impacted and left a crater in the ice, but i see no reason to totally exclude that the block might have landed on ice. If it impacted billions of years ago an eventual crater might have been blown by wind. The surface seems to confirm that it is laying there a loooong time. Exposure to particles in suspension by wind cause a typical "shine" on surfaces exposed to them for a long time. They can even form facets through constant abrasion by prevailing wind directions, fooling 1st semester archaeologists into interpreting artificial things into them :-) This may be the case here. Or not. :-) Edited February 25, 2018 by Green Baron Quote Link to comment Share on other sites More sharing options...
linuxgurugamer Posted February 25, 2018 Share Posted February 25, 2018 Probably the heat of the friction caused the ice to vaporize, and that additional pressure stopped the bullet Quote Link to comment Share on other sites More sharing options...
Guest Posted February 26, 2018 Share Posted February 26, 2018 (edited) Hey uh, Shouldn't this violate newton's third law or something? I mean, the vehicle is pulling itself into translational motion, is this even possible Edited February 26, 2018 by Guest Quote Link to comment Share on other sites More sharing options...
DerekL1963 Posted February 26, 2018 Share Posted February 26, 2018 2 hours ago, Aperture Science said: Shouldn't this violate newton's third law or something? I mean, the vehicle is pulling itself into translational motion, is this even possible It's not "pulling itself" into anything... It's using the wheel and pipes as gears, and a driven gear (the pipes) will always spin the reverse direction from the driving gear (the wheel). Quote Link to comment Share on other sites More sharing options...
magnemoe Posted February 28, 2018 Share Posted February 28, 2018 On 26.2.2018 at 8:34 AM, DerekL1963 said: It's not "pulling itself" into anything... It's using the wheel and pipes as gears, and a driven gear (the pipes) will always spin the reverse direction from the driving gear (the wheel). Yes, the wheel rotates the pipes. like gears they rotate in the opposite direction. so car moves backward. Quote Link to comment Share on other sites More sharing options...
Green Baron Posted March 2, 2018 Share Posted March 2, 2018 I'd rather repair the gear. Question: isn't there a periodic check for cars in (i assume) the US ? Quote Link to comment Share on other sites More sharing options...
KG3 Posted March 2, 2018 Share Posted March 2, 2018 1 hour ago, Green Baron said: I'd rather repair the gear. Question: isn't there a periodic check for cars in (i assume) the US ? The laws are different from state to state. In Massachusetts (where I live) it's every year and the quality of the inspection can vary from service station to service station. I once failed for bad windshield wipers. I think they just wanted to sell me a pair of their $60 windshield wipers. Everyone seems to know of a garage that will pass their car without looking too closely at it, although the state seems to be cracking down on this. They should at the very least check the ball joints and tie end rods! They are supposed to check emissions, lights, tires, breaks, parking break, horn, wipers and check for rust. I'm not sure but I think other states have different laws as to how often or how closely they look at the cars. Commercial vehicles like trucks, tractor trailers, and busses are subject to national Department of Transportation (DOT) safety regulations and are inspected differently. One of the big complaints by truck drivers about the North America Free Trade Agreement (NAFTA) was that trucks driving over the boarder from Mexico were held to lower standards of safety therefore cheaper to operate and more dangerous on the roads. Quote Link to comment Share on other sites More sharing options...
Green Baron Posted March 2, 2018 Share Posted March 2, 2018 Sounds very similar as in e.g. Germany and Spain, except that the check is done by a dedicated technical services company (not the garage) and the times between checks may vary. A missing reverse might remain undetected. Thanks. Quote Link to comment Share on other sites More sharing options...
KG3 Posted March 2, 2018 Share Posted March 2, 2018 Yes, it's a very clever solution to his transmission problem and it works great on flat smooth ground. I would like to see what happens it he backs it up over bumps, pot holes, debris or even a patch of sand or snow! Quote Link to comment Share on other sites More sharing options...
magnemoe Posted March 3, 2018 Share Posted March 3, 2018 11 hours ago, Green Baron said: Sounds very similar as in e.g. Germany and Spain, except that the check is done by a dedicated technical services company (not the garage) and the times between checks may vary. A missing reverse might remain undetected. Thanks. In Norway you can do it either with service company or garage, benefit of service company is that they earn nothing ordering you to repair stuff. Has been plenty of cases garages require replacements who are not strictly required. Quote Link to comment Share on other sites More sharing options...
DerekL1963 Posted March 3, 2018 Share Posted March 3, 2018 4 hours ago, KG3 said: Yes, it's a very clever solution to his transmission problem and it works great on flat smooth ground. I would like to see what happens it he backs it up over bumps, pot holes, debris or even a patch of sand or snow! I was more thinking I'd like to see him try it on hard surface... ground is easy because it gives a little and spreads the weight out. Quote Link to comment Share on other sites More sharing options...
YNM Posted March 3, 2018 Share Posted March 3, 2018 (edited) On 26/02/2018 at 12:13 PM, Aperture Science said: Shouldn't this violate newton's third law or something? I mean, the vehicle is pulling itself into translational motion, is this even possible It's not too weird. The answer lies in gearing. Edited March 3, 2018 by YNM Quote Link to comment Share on other sites More sharing options...
Guest Posted March 3, 2018 Share Posted March 3, 2018 7 hours ago, YNM said: It's not too weird. The answer lies in gearing. Yeah mate I didn't realize they were actually rolling, I just thought they were fixed pieces Quote Link to comment Share on other sites More sharing options...
YNM Posted March 3, 2018 Share Posted March 3, 2018 10 hours ago, KG3 said: Yes, it's a very clever solution to his transmission problem and it works great on flat smooth ground. I would like to see what happens it he backs it up over bumps, pot holes, debris or even a patch of sand or snow! My bigger question is how to control the amount of reverse you get. I hope that's fixed - carrying a log isn't the smartest of ideas sometimes. Quote Link to comment Share on other sites More sharing options...
KG3 Posted March 3, 2018 Share Posted March 3, 2018 4 hours ago, YNM said: My bigger question is how to control the amount of reverse you get. I hope that's fixed - carrying a log isn't the smartest of ideas sometimes. They don't have chock blocks in Africa? Quote Link to comment Share on other sites More sharing options...
YNM Posted March 3, 2018 Share Posted March 3, 2018 (edited) 50 minutes ago, KG3 said: They don't have chock blocks in Africa? It's Jezza, after all. Rudimentary rock blocking works too as long as said rocks are available. Edited March 3, 2018 by YNM Quote Link to comment Share on other sites More sharing options...
Slam_Jones Posted March 3, 2018 Share Posted March 3, 2018 (edited) And I thought Clarkson was actually clever for once with that invention... until it backfired spectacularly, of course Edited March 3, 2018 by Slam_Jones Quote Link to comment Share on other sites More sharing options...
wumpus Posted March 9, 2018 Share Posted March 9, 2018 Any idea why Radon isn't used for ion engines? While I suspect that Radon might be excessively rare in the atmosphere (Xenon certainly is), there is an unbelievable amount of data in the US on areas where Xenon leaks out of the Earth in much higher quantities than normal (in much of the US basements are a popular form of foundation, and when Ra leaks into them, it stays put and poisons/irradiates the residents). My best guess is that it comes down to two issues: the high percentage of Ra is a slow thing, and once the air is liquified once it the Ra level drops to basically zero for the next month or so, and that the rock formations in question (granite, from memory) doesn't form the type of cave systems needed to really supply enough "new radon" for such a collection scheme. But I still have to wonder if there is anywhere to scoop up some Radon. Note that I'm not certain that doubling the efficiency of ion engines is worth it (Isp is "good enough", power efficiency could use some help), but it might help ion drives scale better than limiting them to the Xe supply (there is more Argon in the atmosphere than CO2, but I you might need to make up the Isp losses if you use Ar). Quote Link to comment Share on other sites More sharing options...
p1t1o Posted March 9, 2018 Share Posted March 9, 2018 57 minutes ago, wumpus said: Any idea why Radon isn't used for ion engines? While I suspect that Radon might be excessively rare in the atmosphere (Xenon certainly is), there is an unbelievable amount of data in the US on areas where Xenon leaks out of the Earth in much higher quantities than normal (in much of the US basements are a popular form of foundation, and when Ra leaks into them, it stays put and poisons/irradiates the residents). My best guess is that it comes down to two issues: the high percentage of Ra is a slow thing, and once the air is liquified once it the Ra level drops to basically zero for the next month or so, and that the rock formations in question (granite, from memory) doesn't form the type of cave systems needed to really supply enough "new radon" for such a collection scheme. But I still have to wonder if there is anywhere to scoop up some Radon. Note that I'm not certain that doubling the efficiency of ion engines is worth it (Isp is "good enough", power efficiency could use some help), but it might help ion drives scale better than limiting them to the Xe supply (there is more Argon in the atmosphere than CO2, but I you might need to make up the Isp losses if you use Ar). Isn't it radioactive? Could be a factor? Ionisation energy is also a thing, perhaps it's less favorable. I'm out at the mo, can't do my usual research Quote Link to comment Share on other sites More sharing options...
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