Posts by mtp 198 publicly visible posts • joined 27 Sep 2009
"Despite the two successful suborbital lobs of a Starship prototype, SpaceX has yet to reach orbit, let alone transfer fuel."
This is being too harsh. They were not trying to reach orbit but they were so close to orbital velocity that they could certainly have done it if they wanted. They are testing lanch and landing so there is no point wasting time going around the Earth a few times before doing the landing.
I was there although not at Rothera (where Sara Wheeler went) and we did indeed play darts over HF radio. The loosing base sent the winners some beer or equivalent by the next available 'post'. Once we were refueling a plane from Neumayer and they dropped off a crate of beer but nobody at Halley (my base) remembered when the game was played, it was probably a previous generation of winters who had all been replaced by this point. We even had a wooden signpost to Neumayer in the bar (https://www.zfids.org.uk/1998/z98asm.jpg) as they were our nearest neighbour despite being 500 miles away.
As far as I remember we where honest and when my darts missed the entire board we reported it correctlybut the main problem was that HF radio is very unreliablie so most games ended in stalemate when it became impossible to hear what the other base was saying.
At university the physics building had a long corridoor running down the middle of it and we found that the best way to move accumulated dust and fluff from our side of it to the department at the other end was a few litres of liquid nitrogen vigorously thrown along the floor. It rushed along the corridor in a cloud of white vapour picking up all the dust until it went under the door at the far end of the corridor depositing everything that it had picked up on the way. A minute later it was all gone and there was no evidence left indicating how this dirt had appeared all over their floor.
I used to work with a electron microscope with lots of illumunated buttons but some designer in his infinite crazyness decided that the ilumination shows which buttons could be pressed at the moment not the status of what that button controlled.
So the button for operating mode X came on when it was not in mode X ETC.
That is still evolving. Evolution does not care about teeth, eyesight or anything apart from how many grown up children your children will produce. If eating burgers every day then dropping dead at 40 produces more children on average then writing learned textbooks and running marathons then the McBurger genes win and evolution proceeds.
This reminds me of the Microsoft DR-DOS issue. If Windows (at this time it was a program not a operating system) found itself running on a PC running DR-DOS instead of Microsofts MS-DOS it generated a cryptic error just to scare the user.
https://en.wikipedia.org/wiki/AARD_code
A few years ago I was staying in a remote cabin with my ex girlfriend and she wanted to use her laptop but there was no wifi. The phone signal was poor but even so I set it up as a wifi hotspot so she could get some minimal network access.
Naturally as all the data had to go down a almost noexistent 3G connection the speed was terrible but with the phone next to the laptop the wifi signal was strong. I spent about 5 minutes trying to explain why despite a full strength wifi signal the network speed is low but eventually gave up. She just could not grasp the weakest link principle between the laptop and the wider internet.
I used to believe that until I came across this EEVBlog article where he tested fuses. Summary - they are the safety feature of last resort to blow first if there is a short circuit but don't rely on them for much else.
https://www.eevblog.com/forum/blog/eevblog-1377-the-amazing-unpredictability-of-fuses/
"I bought a very second-hand BBC Micro (a partially upgraded Model A, with at least one dodgy RAM chip!) in 1989"
I wonder if it was mine. I had one of the earliest BBC model As (I think the SN was 230 ish), I upgraded the RAM and I think the printer driver (because some things needed it despite having no printer). It also had the excellent EXMON2 ROM chip in it which I used to single step through the entire OS. Those were happy days when it was possible to know everything about how it worked.
I sold it to a school in London sometime around 1984 and replaced it with a Atari ST 1024STFM (later replaced with a Mega 4).
Collisions have happened a few times. From Wikipedia:
The 1991 collision between Kosmos 1934 and Mission-related debris (1977-062C, 13475).[1]
The 1996 collision between the French Cerise military reconnaissance satellite and debris from an Ariane rocket.
The 2009 collision between the Iridium 33 communications satellite and the derelict Russian Kosmos 2251 spacecraft, which resulted in the destruction of both satellites.
The 22 January 2013 collision between debris from Fengyun FY-1C satellite and the Russian BLITS nano-satellite.
The 22 May 2013 collision between two CubeSats, Ecuador's NEE-01 Pegaso and Argentina's CubeBug-1, and the particles of a debris cloud around a Tsyklon-3 upper stage (SCN 15890)[2] left over from the launch of Kosmos 1666.
The 18 March 2021 collision between Yunhai-1 02 and debris from the Zenit-2 rocket body that launched the Kosmos 2333 satellite (a Tselina-2 satellite) in 1996.[3]
https://en.wikipedia.org/wiki/Tartrazine
Don't know how trustworthy this is but the wikipedia article says that tartrazine causes allergic symptoms in about 1:10000 people but the other 'well known' issues are all just urban legends. It might be a case of scared because they 'read it on the internet' so it becomes true by repetition.
Icon - well he might be drinking soda.
Gemini 8 had a uncontrolled thruster burn that spun the capsule upto almost 1 rotation per second - just imagine being in this and how hard it would be to function. Neil Armstrong (pre moon) was in command and somehow managed to get thing back under control without blacking out or otherwise being disabled by the spin.
Truely the Right Stuff.
I had a set of units that came back from customers as faulty but it was very hard to reproduce. I eventually discovered that it was due to a micro crack caused by a common event on these boards that only showed up when the device was in a certain orientation. When on my desk this was not the natural orientation and it worked fine but in the machine it was at 90 degrees and the weight of the sensor opened the crack.
Caused much head scratching until I found the pattern.
I had a battery powered scope which was ideal for such things - a lovely little bit of kit. More recently I was using a big old CRT scope and got zapped from it because the earth was disconnected, I know why because when it was connected it caused other problems.
Battery power is much better than no earth.
There are going to be some interesting decisions to be made on orbits of any LPS (I vote for LPS) system as there are no radiation belts or atmosphere which gives more choices but the moon has a messy mass distribution which means that more stationkeeping tweaks are going to be required as the orbit gets lower and magnetorquers wont work so there will be a increased fuel burn to maintain orientation. I suspect the answer would be proportionally higher orbits where each one can be seen from more of the moons surface. This is good for reducing the number of satellites and improving orbital stability plus do you really need a 20 satellite fix on the moon? Being between skyscrapers is wont be a issue for a while.
Lets add some maths
Radius of Earth 6380 km
Altitude of satellite 1000 km (random guess)
Diameter of satellite 10cm=0.0001 km (thickness of shell)
Area = 4*pi*(6300+1000)^2= 7e8 km^2
Volume = 7e8 * 0.0001 = 68000 km^3
At a density of 1000 kg/m^3 = 1e12 kg/km^3 (water) this has a mass of
Mass = 68000 * 1e12 = 7e16 kg
A falcon heavy can launch about 10000 kg so to make a 10cm thick shell around Earth at a height of 1000 km would take about 7e12 launches. I think we are safe for now.
(Please check my maths)
Maybe flotsam vs jetsam is relevant here. As it was deliberatly 'thrown overboard' it would be jetsam in which case NASA no longer owns it.
https://oceanservice.noaa.gov/facts/flotsam-jetsam.html
"Under maritime law the distinction is important. Flotsam may be claimed by the original owner, whereas jetsam may be claimed as property of whoever discovers it. If the jetsam is valuable, the discoverer may collect proceeds received though the sale of the salvaged objects."
The problem is more that people believe stuff they read on the internet from sources as unreliable as social media.
Schools should have compulsory courses on critical thinking and general how to identify poor information and this should be done early, no later than 10 years old.
Won't fix it but at least it is a start
Many years ago I was on a Twin Otter fully loaded with fuel drums. We headed off on the great white expanse but we were too heavy to get off the ground. After 10 mins or so of very fast bouncing and probably skipping over many crevasses we finally limped into the air. It was the EPICA project at 2892m altitude which can't have helped. Apparently there is now a station there (Kohnen) but it my time it was in the middle of nowhere with a high snow accumulation rate.
I once built a pendulum clock from PC components. The pendulum was hanging from the head arm of a HDD and used the coils to nudge it when it slowed down. The swing was monitored by a mechanical mouse sensor that incremented the clock on every swing and measured the swing speed by looking at the time taken to traverse the mouse sensor.
All done in discrete 74xx and 4000 series logic - lots of it.
Usenet was good in the 1990s, comp. and sci. groups were my lunchtime viewing and I even used Emacs as a reader. Took a break from Usenet in the late 90s and when I looked again the signal/noise which had been deteriorating for years had dropped to the point were it was not worth the effort.
I hate to think what it is like now.
Sad that it is gone but it had no defence against spam so once the threat of your university / company taking action against you if you made a bad post was gone it was doomed.
But is it wrong? Given publically available data to it the answer to 'an average woman of Afghanistan' is basically what it produced. It is going to be a merging of the images out there and 90% of them are going to be the iconic image so it is no surprise that the result is very similar to the original image but impressively facing towards the 'camera' which puts this in a different league to a simple copy. What about the other lesser influences to this image? Where do they stand? When it comes to copyright this is a minefield.
"500v supply by putting two adjacent 240v sockets in series." - Ouch, I see exactly how the thought process of your colleague went on this because if you think about it from a certain point of view it makes sense.
Sadly from another point of view connecting the live of one socket to the neutral of another would not have the desired effect!
I have also got to wonder why anyone was trying to get 500V from the mains. Wanting double heat from a portable heater maybe?
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