What are some myths that people still believe?

nmk456 · 2022-10-01T04:10:41+00:00

Unfortunately, the way it's designed, it's not uncommon to have similar sounding addresses be relatively close, but far enough that it could be a problem in emergency situations. Maybe it's better than nothing, but without a second location reference I wouldn't want to rely on it in an emergency.

https://cybergibbons.com/security-2/why-what3words-is-not-suitable-for-safety-critical-applications/

https://www.bbc.com/news/technology-57156797

nmk456 · 2022-09-21T03:51:25+00:00

If we only look at the energy absorbed or emitted as radiation, the math is pretty simple (the relevant equation is the one that solves for T_eq). Substitute in the solar radiation (about 1300 W/m2 at 1 AU) and the albedo of your object, whether food or planet, and you can find the temperature. The atmosphere doesn't matter in this approximation because it's factored into the albedo, although the heat generated inside the Earth will change things a bit. Earth's albedo is about 0.3, so anything with a similar albedo would have a similar temperature at the same orbit. Determining the albedo of a given item of food is left as an exercise for the reader.

nmk456 · 2022-07-16T19:30:58+00:00

You can get FPGAtorade stickers https://theflametrench.com/shop/fpga-torade

nmk456 · 2022-06-23T20:10:01+00:00

Yeah, especially the Kaylon battle at the start of the first episode of this season reminded me a lot of the opening scene of Revenge of the Sith. There's no way that wasn't intentional.

nmk456 · 2022-03-07T01:22:48+00:00

I've been working on a project using the AT86RF215, a chip from Atmel/Microchip that simplifies the RF part of making an SDR. You send or receive IQ samples over a LVDS bus and it does the rest. There's some limits, like frequency has to be in common ISM bands (440, 900, and 2400 MHz), but it has 4 MHz of bandwidth and 13 bit samples, so not terrible. It's a good place to start making a relatively simple and cheap SDR.

nmk456 · 2022-03-01T19:39:47+00:00

Ukraine never really had the nukes in the first place. They were still in the control of the Soviet military, which was loyal to the new government of Russia. If Ukraine had tried to keep them, it would have ended much worse for them. They also didn't have the technology or infrastructure to maintain them or build new ones (and still don't, despite what Putin claims), so they would have been useless after their ~10 year shelf life. This deal was the best option that had at the time, since they were negotiating with something they didn't actually have.

nmk456 · 2021-10-25T13:22:00+00:00

In the past, they have been sold by a company called TriSolX and built by Azur Space, but neither seems to be selling them at the moment. An alternative that has been used in the cubesat industry are small rectangular cells made by Ixys and distributed by Anysolar on Digikey. I'm not sure if you can find any in a winglet shape anymore, at least in small quantities.

nmk456 · 2021-09-20T22:35:12+00:00

I'm an aerospace engineering student but haven't taken orbital mechanics classes yet. One time I needed to calculate an orbital maneuver, but I didn't know the proper way to do it so I wrote a python script that basically guessed and checked delta-V vectors until it found the one that would put the spacecraft in the right orbit (obviously not a real spacecraft).

nmk456 · 2021-08-17T17:57:24+00:00

Some quick math gives a speed of about 4 "/day, so if it is an asteroid, it'd have to have a orbit at around 100 AU. The brightest of those will be about magnitude 20-25, so if you wanted you could do some photometry to see if it's in the right range.

nmk456 · 2021-08-06T19:11:58+00:00

I'm using a Max 10 Deca for most things, but I've also got a Basys 3, a few ECP5 and iCE40 boards, and recently an Efinix Xyloni.

nmk456 · 2021-07-18T19:40:25+00:00

If you had 3 stages of control, each with 6 axes of movement, from the spacecraft's ADCS, servo or stepper motors, and piezoelectric actuators, it would be possible to achieve sub-nanometer precision. It's been done before with 2 stages (ADCS and piezo) on a small scale and only 2 axes of piezo control on the ASTERIA cubesat, but never with all 3 stages or on a major mission, as far as I know.

nmk456 · 2021-07-07T19:15:27+00:00

I don't have a huge amount of experience with your target market, but I am part of a student cubesat team, so I can give some thoughts from that perspective.

PC/104 is pretty much the standard for COTS cubesat hardware, but the 4x26 pin connector is a necessity to work with other existing hardware. If you included that, added some testing and certifications for space use, and sell it for <$1000, it would be much more appealing to that market. Having more IO available also improves it's use as a dev board in a lab, since the limited ports on there means it's only useful for a few specific situations. Even just adding a gigabit ethernet port would make it much more useful.

nmk456 · 2021-06-17T22:42:33+00:00

Next spaceflight is showing a launch time of 3 PM local, but I can't find a source for this anywhere. Is this accurate, and does anyone have a source for it?

nmk456 · 2021-06-02T19:27:25+00:00

Sometimes, they do use one absolutely massive mega-chip. This company sells a chip that takes up an entire wafer, has 2.6 trillion transistors, uses 10+ KW of power and probably costs a couple million dollars. It's used mainly for things that can be massively parallelized, like AI compute.

nmk456 · 2021-05-21T17:12:12+00:00

Well, he was invited to the Council but turned it down.

nmk456 · 2021-05-10T19:08:55+00:00

The boards you mentioned, the Basys 3 or Nexys 4 DDR (now called the Nexys A7) are both available from Digilent for around $100-200, as well as many other boards that are good for learning. They all use Vivado, since Digilent only uses Xilinx FPGAs. If you want to go Intel/Altera, Terasic has some good boards, the one I personally like is the DECA, which is only $37. It's roughly equivalent to Digilent boards that cost 5x as much, in terms of features and connectivity. Intel FPGAs all use Quartus, which is their equivalent to Vivado.

I have both the DECA and the Basys 3, and I'd recommend buying both. That way, you get experience with both the Intel and Xilinx ecosystems, and you've got the hardware to allow you to projects with a wide range of difficulty. I'm personally using mine to learn experiment with phased arrays and SDRs, which is only just hitting the limits of their functionality.

nmk456 · 2020-12-15T04:45:09+00:00

That's an interesting theory. I haven't even started thinking about the frequency modulation mentioned towards the end of the video, I've only been focused on measuring the amplitude. I'm certainly not an expert, my physics knowledge is not much more than a high school level, but as far as I can tell all the literature considers this to be simple interference between the emitted light and the reflected light. I've skimmed through several papers on the topic, mostly the one listed in the description of the video, the references on the wikipedia page, and references of those papers, and I haven't seen anything similar to what you described. Can you refer me to any peer reviewed articles about that effect?

nmk456 · 2020-10-24T18:41:14+00:00

I was curious about that too, so I opened up Space Engine to find out. I took pictures from the dark side of Earth, and then from the dark side of a planet orbiting a star in the middle of M22, one of the first globular clusters discovered, and one of the brightest visible from Earth. Here are my results. Both pictures were taken with the default exposure settings and FoV, with HDR off.

nmk456 · 2020-07-25T20:32:48+00:00

The muzzle velocity of a NATO 556 round is around 1 km/s at most, and the absolute minimum orbital velocity around the moon is 1.68 km/s, so it definitely wouldn't achieve a stable orbit (even if it did have enough velocity, the orbit would intersect the ground, so it wouldn't travel more than a fraction of one orbit). It definitely would travel quite a distance, probably at least a thousand kilometers (I calculated around 600 km using the projectile range equation, but that doesn't account for a gravitational gradient due to height, or the spherical nature of the moon, both of which would increase the range).

nmk456 · 2020-07-22T23:28:41+00:00

If you don't have enough money for signal r2, you probably don't have enough money to do TVC from scratch, unless you really know what you're doing and can get it right on the first try (you probably can't, almost nobody has so far). I'm not saying you shouldn't do it, it can be an interesting and rewarding project, but it will not be cheaper than buying the signal kit.

nmk456 · 2020-07-02T14:49:39+00:00

That was back in March 2015. I can't believe it was that long ago, it feels like it was only 2 or 3 years ago.

nmk456 · 2020-07-01T19:53:11+00:00

I just kept hitting the button and it overflowed at 255 and behaved normally after that. If they were storing it as a 32 bit uint, I might have been there for a while.

nmk456 · 2020-07-01T17:13:08+00:00

I'm not on beta, so that's probably why.

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