Recent submissions

Comment · 3 months ago
Again,

Smaller radiator = bigger heat pump + more batteries and solar panels

Satellites have a mass and power budgets. Your scheme only looks at temperature. If you want to build infinitely large AI Data satellites, go ahead.

Comment · 3 months ago
See:

SNAP-10A

BES-5 (oops, sorry 'bout that Canada!)

TOPAZ-I

Kiwi, Phoebus, and NRX (Mars here we come!)

RD-0410 (Dossvidanya Solar System!)

SP-100

TOPAZ-II

Kilopower

Comment · 3 months ago
The Caltech Concept is just that — a concept. No prototype, no tests, no manufacturing, no results. When they achieve this order of magnitude improvement on a prototype scale, that's when we should take them seriously.
Comment · 3 months ago
It just goes to show magical thinking isn't just an American thing.
Comment · 3 months ago
Ah yes. The heat pump.

My response:

Carnot's theorem and refridgeration cycles rear their head. Your heat pump still needs power to pump heat uphill., negating any savings from a smaller radiator. And what happens when you shrink a radiator? It becomes a high temperature radiator, meaning the GPU must operate outside its operational tmperature of about 70 degrees C. So small radiator = big pump + extra solar panels and batteries + dead GPU

Also, how do you deal with the added cost and complexity for the solar tracking mechanisms for the "edge-on-to-the-Sun" radiator?

Comment · 3 months ago
> Ok, there are at least two bad assumptions there.

> First, it assumes the radiator is at the same temperature as the GPU. But radiators become dramatically more effective as temperature increases, with radiated power increasing as the fourth power of absolute temperature. So a heat pump that drives the radiator at higher temperature could make the radiator far smaller.

Carnot's theorem and refridgeration cycles rear their head. Your heat pump still needs power to pump heat uphill., negating any savings from a smaller radiator. And what happens when you shrink a radiator? It becomes a high temperature radiator, meaning the GPU must operate outside its operational tmperature of about 70 degrees C. So small radiator = big pump + extra solar panels and batteries + dead GPU

Also, how do you deal with the added cost and complexity for the solar tracking mechanisms for the "edge-on-to-the-Sun" radiator?

Comment · 3 months ago
This reminds me of the railgun. Basic math and physics tells us that not only would the (very expensive) barrels wear out very quickly, but that it would have had to be fitted on on a nuclear-powered pocket battlecruiser.

Worse, the technology for firing any meaningful payloads from an electric gun (8" Small Diameter Bomb equivalents, guided, airburst, incendiary) simply does not exist.

Same as with Musk's California Vacuum Tunnel (which diverted attention from passenger rail). And his Neuralink. In the 1980s, it was nuclear pumped space-based lasers and Soviet particle beam weapons.

All of the above can be debunked with 2 years undergrad physics and a Casio calculator. Yet they were still taken seriously by high-level politicians and business, some of whom were deeply connected with the military-industrial complex.

People have shrugging of questions like 1 and 2, only for 3 to hit them very hard. But we will see if they can launch 600 of these satellites as they claim.

Comment · 3 months ago
If the "physics" tells you that your satellite cannot radiate heat away from your nVidia GPU cluster because each H100 needs 1.1 meter square of radiator, then opinions do not matter. The same applies to power supply and bandwidth.
Comment · 3 months ago
Comment · 3 months ago
Yes indeed, you are correct. My mistake.
Comment · 3 months ago
The ball is not microscopic, but the tolerances required to make the ball spherical and fit into the socket are.
Comment · 3 months ago
They do. The micro-precision subculture required to (in order):

1. Powder prep your tungsten carbide

2. Form said powder

3. Thermally prepare the resulting slurry using a vacuum forming furnace

4. Finish it with diamond lap grinders, lapping machines and polishing machines

5. Clean it ultrasonically, with solvent, rinse, then dry them.

6. Have the metrology required to test thousands of micron-scale balls a day (a world-beating skill in itself)

7. Build a QA lab that can assure the quality of said balls statistically (you can test them all).

8. And then integrate them via socket assembly

are not just hereditary, but proprietary. And assuming a competitor does manage to achieve the basic ISO 3290 and ASTM F2094 standards, you still need tacit knowledge. Stuff like sintering temperature curves, proper powder grain distribution, polishing chemistry, proper statistical rejection thresholds and a whole lot more.

And that is just the ball. Not the socket, or the ink channels. Making a perfectly spherical 0.5 mm ± 0.0001 mm tungsten carbide ball requires the same techniques used in building micromotors, medical devices, and semiconductor subcomponent manufacturing. Techniques such as high-volume sorting, advanced powder metallurgy, controlled sintering, and precision machines that operate 24-hour shifts without drifting. All operated by modern process engineers who are the spiritual (or actual?) descendants of Swiss watchmakers or the glassmakers of Murano.

Comment · 4 months ago

Live from the official Hacker News API

A modern reader for Hacker News · SvelteKit + Skeleton