Comments by "SeanBZA" (@SeanBZA) on "Scott Manley"
channel.
-
4
-
4
-
4
-
4
-
4
-
4
-
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.
4
-
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.
4
-
3
-
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.
3
-
3
-
3
-
3
-
3
-
3
-
3
-
3
-
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.
3
-
3
-
@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.
3
-
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.
3
-
3
-
@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.
3
-
2
-
2
-
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.
2
-
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.
2
-
2
-
2
-
2
-
@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.
2
-
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.
2
-
2
-
2
-
2
-
2
-
2
-
2
-
2
-
2
-
2
-
2
-
2
-
2
-
2
-
2
-
2
-
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.
2
-
2
-
2