41–50 of 130 posts
Fun fact: The SR-71 and U2 planes had automated celestial navigation systems b/c GPS wasn't around when they came out. There a story in the book about Lockheed Martin's Skunk Works where they mention turning on the system while one of the planes was in the hangar and it locked on to a hole in the roof (sun was shining through the hole and system thought it was a start).
I wonder if GPS and the like will be used more for their clock features than for position. The emissions celestial bodies are perfect fiducial markers [0,1], but connecting them to position still requires accurate timekeeping [2], as the paper notes: Provided the use of an accurate clock, the results presented in this paper will not degrade over time. 0. https://www.twz.com/17207/sr-71s-r2-d2-could-be-the-key-to-w...…
I guess timekeeping is relatively easy? These systems would only operate independently for a few hours tops. I would imagine even a standard quartz movement would be accurate enough.
Good Lord! How wrong can you get!
Very precise timing (often taken from GNSS for convenience) is needed for much of the modern word, from IP, cellular and DAB networks, to AC phase matching the electrical mains grid. Quartz clocks are nowhere near accurate enough for these purposes.
This government report makes very sobering reading: https://www.gov.uk/government/publications/satellite-derived...
TLDR: Our dependence on GNSS for timing almost dwarfs that for navigation. And we urgently need to consider using backups (be that local atomic clocks, or long wave time signals).
Earlier quoted context omitted.
You will likely raise a flag somewhere if you publicise what you are doing, but I highly doubt there would be any issues if you're working on this in private as a hobby. As for chemicals, I can personally vouch that it is a terrible idea to order reagents (or even chemistry equipment) as an individual. I tried to teach myself organic synthesis in the summer before starting my doctoral studies, and ended up with MIB s…
Please tell me there is a blog post or something documenting this experience. Sounds like a fun read.
Sadly I don't remember who it was, it was a fun story. I thought it was maybe Mark Rober or Joe Barnard but I really can't find it anymore.
Edit: found it! It was launched from a weather balloon, and it was both Mark and Joe. https://youtu.be/BYVZh5kqaFg
Earlier quoted context omitted.
I guess timekeeping is relatively easy? These systems would only operate independently for a few hours tops. I would imagine even a standard quartz movement would be accurate enough.
> I guess timekeeping is relatively easy...... would imagine even a standard quartz movement would be accurate enough. Good Lord! How wrong can you get! Very precise timing (often taken from GNSS for convenience) is needed for much of the modern word, from IP, cellular and DAB networks, to AC phase matching the electrical mains grid. Quartz clocks are nowhere near accurate enough for these purposes. This government r…
Earlier quoted context omitted.
The sensor was sensitive enough that it could detect stars during daylight: * https://theaviationgeekclub.com/the-sr-71-blackbird-astro-na... * https://www.twz.com/17207/sr-71s-r2-d2-could-be-the-key-to-w... * https://en.wikipedia.org/wiki/Missile_guidance#Astro-inertia...
That's insanely cool what kind of cameras / telescope are strong enough to do that? My guess is it was primarily hardware and not software bacuse of compute limits Did the planes have to fly above clouds?
Info here: https://www.sr-71.org/blackbird/manual/4/4-3.php
It wasn't exactly a simple instrument to use, and it relied on a ton of planned course information. You could also do a cold midair start after a power outage, but preflight would be much more preferable!
Some modern microwave telescopes like BICEP3 have an additional optical telescope for star pointing that are daylight-usable, but in summer you need to use a big baffle tube. The images are taken with a high sensitivity CCD camera and you can pick out brighter target stars surprisingly well in the images.
Earlier quoted context omitted.
The sensor was sensitive enough that it could detect stars during daylight: * https://theaviationgeekclub.com/the-sr-71-blackbird-astro-na... * https://www.twz.com/17207/sr-71s-r2-d2-could-be-the-key-to-w... * https://en.wikipedia.org/wiki/Missile_guidance#Astro-inertia...
That's insanely cool what kind of cameras / telescope are strong enough to do that? My guess is it was primarily hardware and not software bacuse of compute limits Did the planes have to fly above clouds?
Perhaps I am too paranoid, but I've been told to avoid doing any DIY in this field of study. Apparently, or so I'm told, out of the many, many ways to end up on a list — building a working celestial navigation system can lead to some very inconvenient outcomes. Second, only to ordering large quantities of certain chemicals online. Is this true? ——— EDIT - from the paper, this is incorrect, > The introduction of GPS c…
I've also been told learning too much about linux or the nuclear reactions in power plants or bombs puts you on a list. I just assume I'm on several.
Perhaps I am too paranoid, but I've been told to avoid doing any DIY in this field of study. Apparently, or so I'm told, out of the many, many ways to end up on a list — building a working celestial navigation system can lead to some very inconvenient outcomes. Second, only to ordering large quantities of certain chemicals online. Is this true? ——— EDIT - from the paper, this is incorrect, > The introduction of GPS c…
I've also been told learning too much about linux or the nuclear reactions in power plants or bombs puts you on a list. I just assume I'm on several.
I don't believe they have the people to monitor those that know 'how to use grep' and put them on a list. It stands to no reason, government civil servants are rarely from the top drawer.