Shpaget

Hmm, not for some time. Anyway on topic, today I realized I got lucky that a piece of electronics I built a few years ago didn't blow up and potentially cause an expensive repair on a device it was mounted in. A real-time clock module I got from ebay that came with a coin cell battery (and is a part of my device) malfunctioned a few weeks ago, so I finally got around to fixing it. It turned out that the battery died, which was surprising since it was a rechargeable li-ion thingy and the module was supposed to have a charging circuit. I expected the battery to live for ten or so years. It died in about three, so after reading about other peoples problems with it and inspecting the thing myself it turned out that, due to poor design, the 3,6V battery was being charged to almost 5V (which is not a good thing). For some reason the battery didn't explode but lived for a few years. Anyway, I replaced the battery with a non rechargeable one, disabled the charging circuit, reprogrammed the RTC and reinstalled the device. Seems to work just fine now, hope it lasts. Can't trust cheap ebay electronics. There is a reason the RTC clock with battery included and shipping across the world is only half the price I paid for just the battery in a local shop.

That MECO and staging looked weird.

Judging by the live feed, they seem to have removed the wrapping from the fairing. And we have a Liftoff!

That fairing looks like something from a Mad Max mod for KSP (is there a Mad Max mod?), or stock, but from Jeb's Junkyard. Seriously, what is that thing?

I remember hearing about this lunacy in school; unfortunately it was so long ago I don't remember the context and whether my teacher presented it as an actual lightning repellent or as a superstitious folly.

While I certainly wouldn't say that nothing should be done about rocket stages splashing down into oceans to sink and be forgotten, there are more pressing environmental issues that are both much more serious in terms of damage done and are easier to deal with. After all, perspective is very important. When it comes to ocean pollution, rockets are not really significant factor when compared to literal mountains of trash that are dumped without control every day. Just take a look at this image and keep in mind that this is just physical debris that floats. There is much more of it that sinks, and still more chemicals in liquid form dumped from various manufacturing and processing plants. Our environmental efforts should be prioritizing this sort of thing, and once we bring this source of trash under control, rocket stages can be our next goal.

In addition to the previous replies, sounding rockets achieve, from the start of the flight, significantly higher accelerations meaning that they pick up a lot of speed early on in the thick parts of the atmosphere. Drag is a function of square of speed, so higher speeds bring a lot higher drag forces. In contrast, Saturn V started off at around 1,2 G and never exceeded 4.28 (Apollo 7) and no more than 3,97 for the rest of the Apollo missions.

I don't know why, but sample return missions have a special place in my hearth. For some reason I really like them. Not that you guys need a reminder, but while we are waiting for the Phobos samples, there is still Hayabusa 2 mission going on. The probe should arrive at 162173 Ryugu in less than a year (July 2018) and come back with some space rocks. Hopefully the changes JAXA has made to Hayabusa 2 will improve on its predecesor's problems in sampling and this time we get some substantial amount of material. In any case, Phobos mission is not going to launch before we get some more info on how H 2 performed, so even more data points for Phobos. Good luck JAXA!

That's great! From what I've heard it starts with earthquakes, birds, snakes, aeroplanes and stuff... Hope it won't be a letdowner (is that a word?) like the last one.

Brain fart, I guess. Diesel electric locos routinely exceed 2 MW... Still, it's not a trivial task to handle those powers.

I'm trying to imagine the cable required for a 1 MW load at relatively low DC voltage (a few hundred V, I guess). Anyway, we're talking industrial sized power outlets and then you'd need to convert it to DC. Uh, I've spent a good 15 minutes trying to find an industrial scale electrical device that could gobble up 1 MW, no luck.

If somebody is permanently disqualified for medical reasons, then it is because medical practice has determined that the particular condition in question is a lifelong issue. Unfortunately some conditions can not be cured, only kept under control. Yes, some aspects of jobs are computerized, but humans are there for the aspects that are not computerized. No company or country would want a liability of knowingly giving a job to someone who has a medical history that could potentially lead to loss of life. Yes, Yuri Gagarin (just like quite a few other early astronauts) was driven on autopilot because the government, scientists and the doctors were not willing to take a risk of mission failure in case he gets ill during the flight. They wanted to make sure the mission was completed, and Yuri was a guinea pig placed in a life threatening experiment. If he was operating the spacecraft and went ill, died, or just made a mistake that meant he would potentially not be able to return to Earth, the mission would be a total failure. By giving the controls to the computer they made sure (or more likely) that he would return. They wanted him back on Earth in one piece (dead or alive) so they can study him afterwards. @Green Baron You keep on ninja'ing me.

It seems to me that you are mistaken regarding what it is that doctors do when it comes to medical reports concerning aviation and similar professions that require medical exams. Doctors do not give you a permission or disqualification to do the job. All they do is provide the assessment of your health and it is the employer (or more often the law) that is the one that grants permission or disqualifies an individual for a certain job. Have you ever seen a blood work report? It usually looks something like this (I'm making these numbers up): Test Result Unit Ref. Interval Flag Iron 273 ug/dl 250 - 450 Cholesterol 301 ug/dl 100 - 200 HIGH Platelets 175 x10E3/ul 140 - 415 Calcium 9,5 mg/dl 8,7 - 10,2 You see, there is a test and the result for a particular individual, there is also the interval of values that a healthy person should have. If the result doesn't fall into its respective intervals, it is an indication that something may be wrong, like the cholesterol level in this example. Depending on what specific test we are talking about and how significantly the result is outside the normal interval and how that condition may affect an individual in the specific job, the doctor may give his opinion on the person's fitness for the job, but strictly based on the laws and regulations. There is very little room for manipulation. It is the law that says that if you have this condition or that that you are not fit for a certain job. Of course, when it comes to psychological conditions, it is somewhat harder (or impossible) to put a number on a test and see if it fits in the accepted interval, but that is why psychologists and psychiatrists train for years to detect certain conditions. Yes, some individuals bypass this check one way or another and there are certainly cases where somebody is withheld a license when he shouldn't have been, but those are individual cases that are always going to be present in whatever system you put in place; and I must say that there has to be a system in place to protect the safety of general society. There is no way around that, you just can't allow anybody to fly a plane with 400 people on board without some safety checks.

I'm not trying to say EEG is a lie detector. I'm just giving it as an example of a test on which you can not lie. Here where I live, it is mandatory if you want to be a pilot or an ATC. Keep in mind that most civil aviation jobs do not require perfect health. Most people have some mild deficiency or another. There are provision and tolerances for various conditions. I didn't get the impression this was about OP trying to get into aviation, but more of a general question.

For example, one of the tests is EEG (electroencephalography). Basically they hook your head to a computer and monitor your brain activity while they flash lights at your eyes and ask you questions. The doctors will look at brain activity and irregularities. There is not much you can do to manipulate that because the answers are not relevant, the brain waves registered on the computer are what is important. If another test is for cardiovascular system and they hook you up to EKG, you can not consciously alter your heart rate and rhythm to modify the result. If the test is for peripheral vision, you place your head into a device and are instructed to stare at one spot while there are tiny lights that flash all around you. You are required to push a button each time you see it flash and are not allowed to move your eyes. If you do not see all the lights you need to, you are disqualified. The doctor can see your eyes moving so can he disqualify you if you do. The tests are designed to be objective and hard to manipulate.

Those medical exams are not questionnaires where you tick the "I'm healthy" box and you're done. The exam I went through for air traffic control lasted two days and just about every imaginable doctor pokes and prods you until they are convinced that they can form an opinion on your health.

That's the assumption I embraced with the model above. After all, during the one and a half hour that it took the shadow to cross the States, the Earth moved only 360/365/24*1,5 = 0,06 degrees. Compared to 15° of planetary rotation, it's negligible.

So, I came across a flat Earther video in which a guy comments on the fact that the shadow of the Moon being cast on the surface of the Earth during eclipse travels from west to east. His main argument is that this is the proof of some conspiratorial trickery since Earth rotates once per day and it takes Moon to orbit the Earth roughly 28 days, hence the shadow can not possibly travel from west to east since Moon moves a lot slower that the Earth rotates. He then proceeds to demonstrate this by moving a golf ball in front of a rotating globe. In his experiment, the shadow really does move from east to west. Of course, he neglects to take into account vast distances involved when dealing with anything space related, even our closest neighbor, the Moon. Since I am somewhat fascinated by those distances, I fired up Solidworks and drew our little Earth - Moon system to scale, and indicated the movement of Earth and moon one hour after noon. The view is from above the plane of ecliptic, looking down on North Pole. Earth and Moon rotate counter clockwise in this depiction. The small circle on the right is our little planet Earth, the big dash - dotted circle that doesn't fit the image is the orbit of Moon (which is aproximated to be circular 380 000 km radius from the center of Earth), and the two tiny circles on the left are Moon, one representing its position at noon and the other one hour after noon. The Sun, of course, is waaay to the left off screen (more than 100 meters at this scale) and assumed to cast perfectly horizontal rays. Here we see the left detail with the angular displacement that occurs after one hour (fun but unrelated fact, it's just over one Moon diameter): , And here we see the resulting motion of the shadow in relation to the Earth's one hour worth of rotation (15° mark): The center of the shadow at noon is the topmost gray line, while the bottom blue line is the path of the shadow one hour later. It's clear that the Earth's rotation can't keep up with the shadow. I know you guys don't need convincing, but I find these sort of images very simple yet powerful and fairly accurate tools to represent just what happens in the skies above.

What does that mean? Double pressure of vacuum? Double of diddly squat is still not much more than diddly squat. Or is that double vacuum, as in doubly more vacuumy than vacuum itself? It does look cool, though.

Well, as soon as somebody notices that the Pe is raising, the game is up.

I love those! Wouldn't call them Sci-Fi, though. Anyway, I fondly remember Interstellar Patrol by Christopher Anvil. The ship is definitely my favorite Sci-Fi spaceship. I think I'll read that again!

For those that don't have RPi, a cool Arduino based solution is PLX-DAC. Basically you feed the data into a Microsoft Excel spreadsheet and from there you do whatever you want with it. https://medium.com/@islamnegm/quick-start-to-simple-daq-system-using-plx-daq-excel-arduino-d2457773384b

Thank you for your effort to write this post. I haven't checked the math, but it's a nice read anyway. However, your proposal is not applicable in OPs scenario where he wants to inject a single individual (or a small group) undetected onto another planet. The ship with your design would weigh thousands of tons and would be quite a disaster if it struck an Earth like planet.

The problem is that a shattered inner core is likely a solid lump of steel. How do you mine it?

Hi and welcome to the forums! There have been quite a few discussion here about warfare in space all of which eventually come up with the idea of stealth in space. Perhaps you should read those topics for additional info, but the consensus is that there is no stealth in space. Even with our current technology, if we spot a spaceship we could easily differentiate it from a space rock by it thermal signature. Basically anything artificial will be warmer than asteroids and stand out in infra red. There is a possibility of active cooling and directional thermal radiation, but that would highly depend on your story setting and the capabilities and resources of the spied-upon side. Another issue is that couple of hundred thousand km is very close and anything lighting their engines that close would register on sensors, especially if you have two warring sides that are concerned with each other and monitoring their neighborhood. If your spy containing ship is detected (but not recognized as a spy ship) and tracked, any change in velocity not consistent with ordinary orbital movement would, without doubt, be instantly suspicious. Before the Chelyabinsk meteor hit Earth in 2013, it was undetected, mostly because it came from an unusual direction (roughly from the direction of the Sun). Perhaps you could use that in your story. After atmospheric entry, anything dropping from the sky will experience significant forces and heating. While that may be survivable, it can not go unnoticed. What happens then? Your spied upon nation will go out to try to find the meteor. Once they do find it they will realize it's a spaceship. Trajectory calculation can easily be done and you could perform your trajectory correction maneuvers behind a nearby moon to hide the exhaust, but it will still change the trajectory and if tracked it will be obvious that something is going on. From the storytelling you might want to have a system breakdown period that offers a window of opportunity for spy insertion, or have the spy ship approach from a non monitored direction (not in plane of ecliptic). That makes the maneuver a lot more complicated and expensive, but more realistic for stealth.