Comment by kilo_bravo_3 | Hacker News Reader

Comment by kilo_bravo_3 | Hacker News Reader

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Off the top of my head this would be great for massive enterprise VDI installations and game streaming services (which is just VDI by another name), ML, AI applications, and NVMe storage.

Personally, this will be good for me because everything I do is bandwidth-starved.

I'm not a radar scientist but I am a systems engineer supporting radar scientists working on air- and space-based Synthetic Aperture Radar (SAR) systems. We use GPUs, FPGAs, and other accelerators to generate images from SAR data.

Here's an "old and busted" image made from SAR data: https://hackadaycom.files.wordpress.com/2014/02/image-from-s...

In 2002, it took more than 24 hours to generate a single low-resolution picture from low-bandwidth SAR data on a $1.5 million Sunfire 15K cluster with 70-ish SPARC CPUs. Today, on a single 3U server with two Xeons and four Tesla V100s it takes about 15 seconds-- and that's an extremely high resolution image from very high data rate SAR data.

But our goal is real-time VIDEO from SAR data, so everything needs to be faster. Network speeds need to be faster, CPUs need to be faster, GPUs need to be faster and we need more of them, storage needs to be faster, everything needs to be faster.

I could see a 3/4U box with 16+ 16x PCIe slots each stuffed with a 1-slot GPU with an NVMe (4x PCIe lanes each!) storage array and a couple of 100GBe dual-port NICs blasting through SAR data like a hungry hungry hippo.

As far as PCIe lanes go, if I have a 24-drive NVMe array that's 96 PCIe lanes all by itself.

That makes sense. Thanks to the reactions here (from you and others) getting an idea of the bandwidth starved computational tasks in real life.

I've never heard of "SAR", that's very interesting... But I am curious, if the data truly comes from only radar, why are shadows apparent in many of the created images? Or does the same surface reflect radio waves differently based on whether it is in the sun or not?

Radar sends pulse. Radar moves. Radar looks at reflections from previous pulse. Because radar moved before waves returned and is now looking at the area from a different angle making the image appear illuminated from elsewhere. Its not the suns shadow but a radar shadow. Like if you took a picture with a flash and managed to reposition your camera to a different angle before the light from your flash reached the target.

A bit off topic, but where can I find details of the math behind SAR? In my last job I worked on radar systems and I was always curious about SAR. However all the information I found was high level descriptions. There was even some MIT course available on it but they too skipped/avoided the math involved

(Im curious to see if I can apply similar techniques to audio)

How does one contact you outside of HN?

Hmmm, how many radar pulses need to hit a target to generate video? Sounds potentially irradating... ;)

eg: WARNING Don't attempt to image living creatures WARNING

RADAR typically uses microwaves, non-ionizing. Over this area it's bound to be a terribly, terribly small amount of exposure.

Ahhh, no worries.

Just remembering a friend recently telling me about someone who was killed at a work place. Apparently that person walked in front of the main radar array (defense related I think) while it was in operation and just dropped dead instantly. :(

This happened to a former schoolmate of mine with a pacemaker when strong EM equipment was turned on near them.

The people on site had no idea he had one and attempted to administer CPR, but they wouldn't have been able to detect his pulse, regardless.

Imagine how it looked to the people who never found out and the version of the story they might still be telling others.

At the 1933 World’s Fair in Chicago, Westinghouse demonstrated a 10-kilowatt shortwave radio transmitter that cooked steaks and potatoes between two metal plates [1]. In 1946 a Raytheon engineer named Robert Spencer "...was visiting a lab where magnetrons, the power tubes of radar sets, were being tested. Suddenly, he felt a peanut bar start to cook in his pocket. Other scientists had noticed this phenomenon, but Spencer itched to know more about it. He sent a boy out for a package of popcorn. When he held it near a magnetron, popcorn exploded all over the lab. Next morning he brought in a kettle, cut a hole in the side and put an uncooked egg (in its shell) into the pot. Then he moved a magnetron against the hole and turned on the juice. A sceptical engineer peeked over the top of the pot just in time to catch a face-full of cooked egg. The reason? The yolk cooked faster than the outside, causing the egg to burst..." [2]. This discovery led to a patent application for "the use of microwaves to heat food", a concept which was eventually realised in the "Raytheon RadaRange" series of microwave ovens [3].

[1] https://en.wikipedia.org/wiki/Microwave_oven#/media/File:Coo...

[2] https://spectrum.ieee.org/tech-history/space-age/a-brief-his...

[3] https://en.wikipedia.org/wiki/Microwave_oven#/media/File:NS_...

Given the Inverse-square law, your phone and wifi network will probably give you more radiation..

I had some bones scans (plus a couple of CTs the same day, just a bit more ionising radiation) last year. They inject you with Technician 99m and YOU become the gamma/ x-ray source. It's a little concerning when you see the detail and spread of the radiation. If it wasn't a pure Gamma source (and 6hour half-life) it would be lethal!

I forget if it was 70,000 milli or microsieverts (think it was milli? 0.5% increased risk of cancer in my lifetime). Oh, and my bladder looked like a lightbulb.

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