Comments by "SeanBZA" (@SeanBZA) on "Scott Manley"
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The thing about the photography side was that the ultra fast gas switches were not used to fire the Xenon flash, which, for the technology of the time, was easy to do, using a simple high voltage pulse that ionised the gas in the Xenon flash tube at the cathode end. The big thing was they had to actually only fire the tube for a very brief period, so as to only have this very short burst of very bright light, so that the motion of the aircraft would not blur the image. Thus the need to develop a device that would be able to turn on very fast, and also handle a massive current pulse, so as to dump all the charge in the capacitor bank used to provide energy to light the flash tube, so as to drop the voltage across the flash tube (at this time it would be dropping from the 400V or so initial voltage, to the cut off point of around 60V, where the tube itself would start to slowly cut off due to the arc voltage being below the voltage needed to keep it on, slowly being in the order of tens of microseconds) to close to zero, and thus ensure it has a sharp cut off. Most devices at the time would either not last more than a single use, or would not have the fast response needed.
This device was the original gas thyratron, and the need for fast ones meant they made them with a hydrogen gas fill, with early ones filled with neon being both slow, and too low an operate voltage. Hydrogen gave the needed high voltage stand off needed, and because it is light, it also ionised very fast, giving the very rapid current path build up, in the order of nanoseconds from fully off to fully on. This has led to them being now an export controlled device, and to this day an item that is still made, on the original tube lines, by some specialist companies in the USA, as the US military needs them for operational parts, and, because of the hydrogen gas fill being able to penetrate almost all seals with ease, a part that has a very limited shelf life of around 2 years, before you need to either replace or rebuild it. Neither are cheap either.
You can test it at lower current, and do all your qualification at this level, as full power operation you only have around 5 uses, before it degrades to the point it is no longer usable. Selling them is ITAR restricted, as heavily as any part can be, because of the one use case, so there have been a few attempts to steal the technology. These days you still find it hard to get the same power delivery with small volume, it really is a part that is perfect in it's application. But you can do it, with modern high power semiconductors from specialist companies, with corresponding exotic semiconductor compounds, and prices that make the gold used to plate them the cheapest cost in production.
Incidentally the bridge wires also underwent massive changes, from simple thin wires, to the modern ones, mass produced using semiconductor wafer processes, to make thin film metal alloy strips that are precisely controlled in shape, composition and dimension, so that all of them are as close to atomically identical as possible. The difference in timing between them is in the order of picoseconds, they are that identical.
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Funny enough, I did once jump start a helicopter, which had a battery that had run down due to the DC bus being turned on overnight so the security guards could use the aircraft radio to listen to broadcast FM. Helped that I did my apprenticeship on that model, and knew the entire electrical system, and also the pitfalls that could occur with them running the battery down, and what to look for. Ground power unit and the ground power connection, start the ground power unit and power up the DC bus, and they press start.
Low current, the ground support unit is designed to supply 8kA at 28VDC, and this little turbo barely made it to 400A during start, so after a half minute of idle, pulled the cable ( only way, there is no disconnect other than a sense contact on the plug), waited another 5 minutes at idle to see if the battery was not going to go into thermal runaway, it was still cold so gave them a clearance to take off back.
As well used another ground support unit to jump an ambulance that had waited 6 hours for the casevac to get there, with lights on, and there had to grab jumper leads to make the link between the connector and the battery. those lights went very bright on 28V instead of 24, and that ammeter needle did not even budge off the zero during the very very vigorous starting.
As to the LRV batteries being used to fire the ascent stage probably no issue, the batteries certainly were the same chemistry, they used a similar enough voltage. The major issue was the disconnection, as the LRV batteries would stay behind, and the ascent stage needed power to keep the valving operational, so they designed the systems to get you power from an alternate set of ascent batteries if the main ones failed, but use batteries on the ascent stage.
You could not have kept the mass centre stable if you used the LRV battery pack and carried it with, no real space to place it (otherwise they would have had equipment or battery pack there already) and also it would move the mass centre from the engine bell outside the ability of the RCS system to compensate for the eccentricity.
Silver Zinc batteries are heavy, and are only used in space applications because they are so reliable and tolerant to abusive temperatures and charge and discharge use, unlike the modern lithium chemistries. Thus you can have a smaller battery pack for the same high current draw, and not have to worry too much about it cycling from -100C to +200C every orbit.
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You can see a skirt on the base, so likely it was lowered onto the stand and sat on the skirt. Then they likely used multiple clamps to hold the skirt to the stand. Most likely is that one or more of the clamps either were not tight, or the bolts had been machined undersize, leaving not enough thread engagement, or only a part of the thread was engaged. Then the thrust snapped those, and the others that held tore the skirt loose, which accounts for the damage, as that skirt likely also damaged the engine bells as they rose up past the stand centre, and either bent them or fractured them.
Bent ones got hot spots that later on failed, and the cracked ones were losing lots of cooling fuel till the uncooled areas melted away, and caused that engine to shut down because controller saw dropping thrust. Then the remaining engines were slammed to 110% to compensate, and this extra stress meant that one of the dented ones split open, and the parts blown off into the plenum damaged piping and such on others, and also likely destroyed the guidance controls, as it did not recover. Thus the big black cloud of burning fuel and hydraulic fluid, and bits of engine rich exhaust.
Controller saw thrust was dropping on those engines, or pressures were dropping and flow rates were running wild, and shut off them, trying to correct attitude with the others by throttling them back and trying to correct with steering the remaining engines, and then it went horizontal. It probably detected a launch abort, and attempted to blow the destruct charges. Of course, seeing as this is a test firing, those likely were not fitted, just had the test bypass units in place, to pass the regular self test cycle.
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A lot of very bespoke computer designs were around before the microprocessor came along and guided them into a few very rigid areas. Especially those that were made from discrete logic, and where the designers went and made it with instructions they needed, and little more, and where your software and hardware were very tightly bound. Designed for the purpose, and then made to be as compact as possible, with, in that era, as few transistors as possible, because they were both very expensive, and also not as reliable as diodes. So you had a lot of diode logic, with transistors scattered around where absolutely needed, to act as inverters and regenerate the logic levels.
Many of those designs were translated into early IC based systems, and they often used EPROM to do complex functions, like a lot of glue logic, and also to store tables used in math, so as to simplify multiplication, giving you the ability to have 2 5 bit numbers be multiplied together, to give an 8 bit output, in a single clock cycle. Used a 2708 1k EPROM, holding the decimal number table, and allowing you to do multiplication in a few cycles through the table per digit.
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Also your mobile phone absolutely depends on GPS, just to provide an accurate clock that allows for the time slots per device to be as tight as possible, allowing for maximum data throughput, but also to provide an accurate clock that allows the base stations to be able to use QAM256 to get as much data through per signal transition, using the GPS clocks to generate a very precise, as in down to single parts per billion accurate, clocks for the base stations, to do this. No GPS, no clocks, and very much degraded phone service, as the towers need to fall back to a very coarse clock provided by a heated crystal, good enough for one part per million, but now resulting in a much reduced data rate per device.
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Probably will need around 5 times the delta V to deorbit, though of course that is also something you can do with just using a large ion engine, and a lot of fuel for it, with power being provided by the on board satellite arrays, as you would need minimal power to charge batteries as they only will have to provide orientation and 45 minutes of low draw during the night passes, and will not really need to power much in the environmental system with no people on board, do you can simply shut down and drain a lot of the systems to safe them, then keep the bare minimum like attitude control, computer systems and circulation to even out temperature.
You can close all the airlocks as well, and that will reduce the need further for power. Just your booster bus will need some redundancy power wise and control wise, probably like the shuttle, 5 general purpose computers to run it, and likely some solar panels to augment power, and also a lot of RCS fuel for attitude control. Easy to do if you have 2 of them one each end, and thus taking turns in providing thrust in orbit to raise it, and slowly over say a year getting up to a relatively open orbit. To get past LEO will take about as much ion engine fuel though as what you can fit into a Falcon 9 heavy payload fairing, as a single large cryogenic tank, so you probably will want to make the tank emulate the fairing and take it to orbit, it will save weight using the fairings as structural and insulation instead of discarding them. Would say 4 F9 heavy launches will get the lot up there, with 2 separate orbit lifter units and tanks, and then probably a final set of spacewalks to provide connection to them so they can share fuel and power
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@NicholasRehm Not likely, just that the computer systems are probably only going to be Intel 386 based at best for the core of the ISS, as those are currently the only, aside from some Motorola and MIPS parts, of around equal speed and complexity, parts with space grade reliability available, Laptops and other stuff they handle by having multiple devices, so a radiation induced failure is not terminal, and they do repair a lot of them by swapping parts around common devices.
Remember most of the control software is either running on redundant hardware with error correction, and no method to update it, or is running older versions of operating systems that are different enough that your common malware will not run on them. However nothing stopping somebody from doing a Stuxnet style attack, though that requires intimate knowledge of the systems and how they are connected.
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Not really, the field would very likely also affect operation of the craft itself, so much simpler is simply to have light mass shielding, or something that you need to take with do it as well. Most likely thing is that there will be a water tank that is also a shelter, with the water acting as shield, and also the required food rations can do the shielding as well.
Probably there will be a thermal shield used on the spacecraft that does triple duty, acting as sun shield, and also as a micrometeorite shield by having multiple thin metallised mylar layers, and acting as a radiation shield by allowing the high energy particles to impact it, and the inner layers handling secondary emission, then the spacecraft hull itself acting as a barrier, with the rations packed so as to absorb it's secondary emissions. The dried waste would also be packed back into the same spot, so the shield gradually changes from food to poo as they travel along.
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Well, it would devolve to VFR from 1924, when pretty much the instrumentation was the pilot and his eyes. Would suggest a good upgrade would be to add in a standby compass, standby altimeter and a standby airspeed indicator, as a minimum flight instrument list, that will help in case the ancient Garmin decides to brain fart, as they are well known to do with some combinations of a complex map and some locations. All 3 can be bought used, and simply sent in for a certification, and then the standby compass will just need to be swung with the aircraft in flight ready configuration, to adjust the 8 cardinal point compensation screws.
Memories of 3 hours in the swamp, in the compass bay, acting as the intercom link between my instructor melting in the rear, and the 2 pilots and flight engineer melting in the cockpit. After the 10 full circles to get the newly repaired fluxgate sensor aligned perfectly, the others decided to drive back on the tow tractor, while I elected to stay on board, and fly back with the 3 in front. They still had 3 hours of fuel left, but only needed an extra hour to complete flight hours for the month, so they did a little trip out to sea, and there I got to see them doing an aerobatics show with the 16 ton helicopter, doing all the daring moves, that are limited to 0G to +3G, that are permitted with a helicopter when you want to avoid chopping your own tail off, or having the main rotors separate. Sitting in the door, hand through the strap, and looking up at the ocean above me, and the sky past my feet, as they did a few barrel rolls around 1km offshore, with the closest place to swim to being the offshore oil platform. 2 very happy and now cool pilots.
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No need to actually look for a new processor, simply use one of the more modern Space rated products that are still available in large volumes. Intel still does supply the 386SX and DX in space rated packages, using a SOS technology, which is a more modern and faster part. Yes likely just a few thousand fully tested dies in CA storage, ready to be packed and tested to order, but still a part likely to be around for the next 50 years.
Buying an original Mostek or Rockwell part is still there, not robbing old equipment, you just pay Rochester Electronics to take a wafer and pack it, then test the result and get the qualification, they specialise in old silicon, buying up old wafer stock and storing them essentially forever. You need it you pay the price they ask, and smile. With gritted teeth, they price just below replacing the whole lot entirely, but still cheaper.
However the 6502 is, thanks to it being out of copyright, one of the more prolific processors around, available as an IP core for pretty much all FPGA and ASIC families, as it is simple, very small and very functional. You have one in every hard drive, used to load the firmware into the ASIC and FPGA units that do the actual work, and it also then is a slow processor, but tiny one, that does housekeeping and monitoring of the hard drive, so that the drive can retract heads and shut down gracefully when power is removed. With only 64k of memory you can make half the fixed ROM, for bootloading the rest, and the rest RAM to handle memory, with a little bit of IO somewhere to feed data out to the rest of the array. Simple to implement in silicon, free assemblers and compilers, and no money to pay for a per unit license, it is very common to have it embedded all over in equipment as a processor doing something.
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Plus the material used for the walls got thinner and thinner, till they had to stop, because the craft was almost at the point it could not support itself under earth gravity. So thin that the crews who were building it had to take care not to step on, or touch the hull, as they could destroy it merely by putting a foot on the surface, and tear the skin. This would mean scrapping the entire craft, and building another, as the skin was too thin, and the joins so small, that they could not remove a panel and rivet in another, as the material would likely tear. The end material was barely thicker than the aluminium used to make cans, and just as easy to dent when not pressurised.
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My father crashed 2 aircraft. One a Gypsey Moth during training, and the other was a Lancaster, that sort of fell apart around him over the Bodensee. All he remembered, before the 6 weeks of black, was the plane, and his parachute, being on fire, and him telling his crew to bail out. Austrian nurses told him they picked up his body in a snow bank under a pine tree, and thought he was dead till the coroner found a heartbeat. Then patched him up, removed most of the broken pine tree, broken glass and shrapnel from him, and did a massive skin graft to fix the burn that covered his entire back. Basically broke almost every bone in his body, but the Austrian doctors and nurses put him back together.
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The modern way to get accurate time is a set of GPS locked hydrogen maser clocks at each location, so that the GPS signal, knowing your accurate location, and a long enough time, allows both atomic clocks to keep near perfect time with each other, and then you record the data with a time stamp and use a compute cluster to correlate the data to match each waveform to the corresponding one from the other. From that determine the delay due to distance, and solve the trigonometry. You have to sample at the carrier itself, which generates truly huge data sets, but you can use local computation to reduce the data volume, without sacrificing the time information, and once you have the data you can also average over a few minutes, to both get a motion vector compensation for the earth rotating, and also then the vector for the spacecraft moving.
Before you would record both outputs using magnetic tape with an accurate clock, a Cesium atomic clock that was in a suitcase, that got flown there powered up, keeping the time from the master clock, and used to time stamp the data on the magnetic tapes. Then the tapes were flown back, and a room full of mathematicians solved the problem. Current methods rely on a high bandwidth link via the public Internet to do the backhaul in near real time, and NASA has the computer clusters to do the data handling as well in near real time as well, thanks to improving technology.
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Well simply because they are rare, and there are not exactly a million cameras on Mars capturing video 24/7/365, only the odd camera on a spacecraft that orbits, taking a complete pass every few days for the low resolution, and every few weeks to months for the higher resolution imagers, simply because they are scanning with such a small aperture camera to get that increased resolution. 99.999% of the meteorites that hit earth smaller than 20kg are not recorded either, simply because they burn up out of view, or nobody looks at the footage, and only the bigger pieces actually make it down and leave any mark, so likely 99.99% also are never going to be found either. Big planet, small rock, and nobody knows when or where one will hit.
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@DrDeuteron True, but the decay products are not quite as benign after a while, as you get into the longer lived decay products, that are going to emit gamma radiation at some level. But the RTG would only have the core loaded just before final mating to the lift vehicle, so it is inert, aside from some testing during construction, then the fuel pellets are removed and placed in a cooling unit. But even then you can stand next to it for a few hours, as the shielding is very effective, and it also has to survive reentry at maximum velocity in case of a failure of the launch vehicle, and also explosion on the pad. That is why those RTG units are normally deployed on an arm, both for radiating heat away, and to keep the low levels they emit from interfering with other instruments, so have it far away, and calibrate it out.
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Well yes, the currents involved are minuscule, and the price really puts them in the "we got a budget that is not a worry, and we do not want a battery that will leak ever" camp, and the main use is as memory back up, as it really can only supply 100nA of current, so most uses are as standby power source for memory back up, where you need to first make sure your memory uses less power. Consider these batteries in the forms normally seen, DIP24 ceramic package, can be shorted out merely by a fingerprint on the board allowing enough current to flow, and you typically also use ultra low leakage capacitors (PTFE dielectric, none of that rubbish ceramic, electrolytic or tantalum capacitor will do) to store charge to allow them to deliver a current pulse for other applications.
Yes you can make a clock that will run forever off them, though you will find it hard to find a foundry to make the large dimension IC to get low leakage, and a display will similarly have to be specially made, probably both will be a SOS (silicon on sapphire) structure, with the LCD laser sealed after filling with the fluid, to keep it from degrading. Might be done for a $500k watch, because for sure the mech will cost more than making the case out of platinum iridium alloy.
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@solandri69 Most likely poor maintenance, they painted over the cables time and again, and you will probably find they trapped water in the cable, which led to corrosion cells and failure. The cables likely were made from hot dipped galvanised strands, which eventually had the zinc erode off, exposing enough steel to make galvanic cells inside the cable.
I would say the design flaw was not in having enough cables there, so that you could safely remove half of them every 5 years per tower to replace with a spare set, and those removed went off to be unwound, serviced and inspected, and then greased, reassembled and recoated for the next tower rope cycle. 10 years would be plenty of time to find weak strands and remove them. Yes you would probably be splicing in repair sections every time, making the cable thicker in parts, but they would still be more than capable with that. That the initial cable failed at the poured zinc plug indicates it was very likely badly corroded inside from neglect, as that section is the one most protected cathodically, but had plenty of water ingress to corrode the inner. Likely all the lanolin applied during manufacture was long gone, and had never been replaced.
Not that those were highly stressed cables, only a static load, no real dynamic force and no real bending. There are mine lift cables that are kilometers long, used dozens of times daily, that are probably older than those, but they also undergo regular inspection and lubrication cycles to keep them in operation. There are plenty that the cable weighs more than the entire telescope aerial steel structure, just in the cable alone.
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That aluminised fabric is also used to make bags, which hold stuff sensitive to thermal damage, and they work well to keep the contents at a reasonably stable temperature. I use the old bags, which are very big, as camping blankets, as they are easily big enough to cover you, and after 5 minutes you are very warm inside from the reflected body heat. Normally a ground sheet, one on top of that, a blanket or thin foam mattress, then you, a blanket, and another on top is a perfect way to stay warm even on the coldest night. They take up little space when folded up as well.
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I would guess the major reason for lack of proper guidance is because the computers and controls are in the second stage, and the first stage is mostly just sensors and actuators, to save mass in not having 2 guidance blocks.
Simplest solution would be to put only a small low mass battery and controller there, to just turn the booster around and fire the main motors till empty, or at least be able to receive a deorbit burn instruction the next pass, and then scrub enough energy to land in the Pacific in 2 orbits. Would need to have the extra fuel and oxygen, plus also the ability to relight the core engine at least twice, first time to drop down a lot, and the second to finish, after drag has been calculated from the timed burn, then probably 2 orbits later get an updated firing time and duration on the remaining fuel.
But this needs extra fuel to be carried, and the motors might not be able to restart. Otherwise just a big drag parachute to make it come down very fast and calculate the drag to make probability such that it will land in the ocean. They are just hoping that 70% water is good enough, and the 1% that it lands in China itself is fine for them, as the chance of hitting the launch area is very small.
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@lawrencedoliveiro9104 To run a run of them, using existing masks, the quote came to $10 per transistor, with a lead time of 18 months, and a minimum order quantity of 100k units. I needed 2, so went through the pain of putting in the paperwork, to have a common part substituted for this obsolete superceded transistor.
The 100k 18 month lead time though is pretty much industry standard, unless it is for something like a sea of gates ASIC, where you only pay for the final metal mask, and run off a existing batch of nearly fully made wafers, where you will get 10k units, 100 wafers, one carrier full, run with your mask, processed and packaged for you. Make sure you got it right, because they only will do a basic wafer test to see if it responds to signals, and is not shorted too badly. Then it can be as low as 6 weeks, though you will pay.
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Making an engine that uses elemental fluorine is going to be hard, seeing as you will have to make a pump that can handle the volume, and last long enough, as you will be having a race between running out of fuel, versus running out of engine. These will be rockets with engine rich exhaust even running perfectly, let alone when they get upset. Plus remember bulk fluorine liquid will burn things you think are non flammable, sand, asbestos, water, steel, aluminium, unfortunate people downwind......
now think of the thermal shock in the first combustion chamber, and that whatever you use for injection of the lithium will be dissolving in the hot liquid, and whatever you are using to bring in the fluorine will be doing the same. You probably will also not want to use pure lithium, rather a lithium sodium alloy, as those do have a lower melting point at least, and with Gallium you can get it low enough to use ordinary steel alloys as the tank.
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Guess version 2 should include into the mass calculations the addition of a small set of doppler radar sensors, and use them during the landing, probably doing a disable of the data from them below 50m, because of dust. The 3 radars will be giving a X drift, a Y drift and an altitude above terrain, along with closing rate. That will allow them to remove residual error from the IMU units, which likely led to the rolling over, as the tiny errors accumulated during the journey, and rounding errors led to the ground drift likely being excessive, and thus it landed with a significant drift, which caused it to tumble.
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Helicopters tend to avoid negative G for noise abatement purposes. Heck of a noise as the rotors hit the tail if you pull negative G past a point. Some helicopter designs include in the tail a heavy steel cutter bar, designed so that you get a very audible warning, as it chews the tips off the main rotor blades, that what you are doing is not a good idea. Yes you will need all new rotor blades, very expensive, and a good pit of panel work to fix the hole cut in the tail rotor, but still cheaper than losing the airframe.
Do remember having a flight with some really stressed out pilots, who had spent 3 hours turning in circles to calibrate the magnetic compasses after a replacement, and I took the flight back instead of driving on the tractor. Sitting in the cabin, door open, legs out and holding to the strap, with the sky below my feet, and the ocean visible through the rotor blades, as they were doing barrel rolls in this 16 ton helicopter. Yes it could lift cargo, 16 tons max at sea level, and if you could fit it inside, it would carry it.
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Probably supplied by the same company, just had a little more care taken in processing to keep thickness variation, always there with thin foils, to a minimum, and to have a single pass pressing, so both sides are shiny, unlike the regular foil in which 2 foils are done at a time, with a thin oil coat between to prevent sticking, so as to cut time and cost. the foil from the roller is rolled onto a wide long roll, then goes to a slitter, where it gets cut to a width, then the length of foil required per pack is rolled onto the disposable mandrel in the box.
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Outer layer would be destroyed by the sun, but the aluminium under will be mostly fine, except where the plastic of the threads has been destroyed, so the blankets will have sagged and deformed, with likely some of the structure visible now. Paint exposed will be basically only the oxide pigments, and the mineral powders and fillers, nothing organic left, except where sheltered. Glass exposed could likely be a lovely blue from photon and electron bombardment, though most of it would be brown for the same reason. Thin film of dust on everything, as it rains down from the sky, as a result of micrometeorite bombardment nearby causing dust to fly up, and also from static charge causing particles to levitate in the vacuum from charge generation due to impact from solar wind protons and electrons.
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@-danR High pressure gas comes into the check valve, then there is a orifice plate to provide some flow restraint, and then the burst disk. In the space between the 2 units you can add a simple leak detector. For the oxidiser just use a high pressure electric feed through and a plain low carbon steel thin wire that will be corroded open if there is any leakage, and similar for the fuel, as it is also corrosive. Cheap, and can be integrated into the flange and orifice plate as well with ease, along with a pressure test port. You could also add in pressure transducers and a low pressure fill with gas, but pressure sensors that will survive that fuel and oxidiser are not cheap, nor are they low mass, as you need a diaphragm and transfer fluid to keep from melting the silicon strain gauges, which are ironically the cheapest part of the sensor.
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@paulhaynes8045 The phone has GPS yes, but also the towers, because they have a fixed nearby location, also will send the ephemeris data for all the locally visible satellites to the phone on request, so the phone GPS can lock really fast, and it also uses the time difference between local towers to gat a very fast and somewhat accurate location if indoors, so that it can at least give a position to within 30m almost immediately, even if there is no sight of the sky for GPS signals. The GPS signal is used outside in your car, to track better, but rough location is done using the signal strength and timing of local towers.
Did once turn on a phone GPS with no coverage from the network, and it took around 20 minutes to finally position me, within a 100m sphere, while another phone, with service and data, took under a minute to position, using data and the 2 visible towers to get a rough area to gain coarse position fast. GPS in your phone needs data, stand alone GPS can do without it, though your accuracy improves with time on, as it refines errors out long term, though you also get the map used providing some sort of sanity check, as there is an assumption if you are moving you are on a road, allowing it to remove parallel paths easily.
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Not necessarily that the parachute will fail to operate, it could, because of the Russian space program wanting simplicity and robustness, have a very simple pressure capsule that was only armed by a pin being pulled during separation, that now is waiting for the pressure to approach a part atmosphere, which would be the opening pressure in the upper Venusian atmosphere, and thus acting as a backup for the electronic trigger, or it also acts to power up the lander, as it would assume it was doing reentry, and thus connect the internal batteries to the electronics. 50 years and the batteries might have still some residual charge, enough to have it give a final few seconds of swansong, as the radio transmitter operates for a few moments before they deplete completely.
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Remember every survivor of an ejection does get a tie pin from Martin Baker, as testament to surviving the event. Fun thing is the speed at which it does eject you does compress your spine, so you will only ever eject once, as the second time might kill you. Your legs get pulled in with straps, but your hands are not pulled in, instead you have both hands on either the top ejection pull ring, or the one between your legs. You do though want to pull your legs in before, as there is a rather good chance if you do forget that those straps that pull your legs in to the seat are there, and that they pull your feet in by being attached to the airframe, and pull in while the seat is busy making you 10cm shorter. You have a greater than 50% chance that unprepared your ankles and shins will be broken.
Yes have chatted to pilots that survived landing separate to the plane, and met the one who landed missing large parts of the airframe behind his seat, but still had a working engine (sans afterburner, seeing as the missile hit that), and no parachute or brakes. Him ejecting would have been fatal, he is a little past the design envelope for that particular seat design, and ejecting would mean his head was the canopy breaker. Fighter pilots are in general short and stocky, because the cockpits are designed for short and stocky people. Very uncomfortable for bigger or taller people like me to fit in there.
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As more satellites were added in different orbits, accuracy improved. With low numbers of satellites, and also with long paths through the air to provide diffraction of the signal, you got poor accuracy. More orbits meant more visible at any time, and thus a more precise position. You need, IIRC, at least 4 to get a coarse position in 3 axes, and with every added satellite visible at the same time your error reduces. At 6 you get 100m, and with more the error reduces further, with most receivers able to handle up to 12 simultaneous decodes at a time, and with more sophisticated receivers using ADC units that can sample at the actual chirp bit rate, timing each individual bit as it comes in, and thus being able to correct for smaller drift with each cycle.
Some of the software defined units have no real limit on the number of satellites they can view simultaneously, just depends on the amount of memory and processor speed, as you can always add more of both, and make the rake receiver scale with visible satellite numbers. Some of those have impressive cold start capability, being able to start from cold within a few minutes, and with warm start capability of seconds, provided the data they have is not too stale.
Big issue is with noise, you find that often GPS signals in urban areas are poor, lots of RF noise desensitising the receiver, and also urban canyons making for lots of multipath distortion, and limiting visible sky to use. Sometimes I need to restart the old Garmin I have a few times, as it is unable to start, but often during RF quiet times it will be up and running in 2 minutes, from a warm start.
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@ericlotze7724 Not much about VFD's other than they all die eventually. The SOS construction because you have to grow a film on an insulator for electrodes, and sapphire in pure form is transparent, and making the whole clock in the display area is possible, as the electronics can all be coated with silicon nitride to provide isolation afterwards, except for some bumps at the edge of the device that are built up with aluminium to make the top layer connections. You probably will want to use an electrochromic display instead of LCD though, as that saves a lot of power, though you will still need to have a capacitor to store the energy needed to refresh the display, which likely will only update once a minute. But same construction physically as LCD, just needs a very low current high voltage (around12V) power source to do the update.
Going to be fun to do the crystal drive though, with nanowatts of power available, and typical watch crystals being in the microwatt range for drive. Battery array likely to be a lot bigger and thicker than the display. your wristwatch is going to be Rolex Oyster size, and only rated to 10m depth.
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@michaireneuszjakubowski5289 Thing is that as a single aircraft it had a very limited lifetime, your airframe needs periodic inspection, and this is actually more expensive than building the aircraft new again. Hopefully they will build at least 2 new ones, as the cargo capability will be used for sure, and having two or more makes the cost so much lower to maintain, as your costs to manufacture is not linear with number, and building 2 or more, with the knowledge from the years of running the first one, will not be as expensive, as the new ones will have all the fixes that went into the first one, and thus will be much improved.
Yes it needs to be rebuilt, another casualty of this senseless posturing.
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