Hacker News: gjrq

New comment by gjrq in "Blue Origin's New Glenn blows up during static fire test"

gjrq — Fri, 29 May 2026 03:32:30 +0000

The estimate is roughly E = rho*R^5/t^2 with rho the density of air: https://en.wikipedia.org/wiki/Taylor%E2%80%93von_Neumann%E2%...

New comment by gjrq in "Blue Origin's New Glenn blows up during static fire test"

gjrq — Fri, 29 May 2026 03:11:20 +0000

Counting frames on YouTube, I get about 0.3s for the blast front to reach the top of the 600ft towers. That gives an estimate of around 600 tons TNT so definitely nowhere near all the fuel exploding.

New comment by gjrq in "A supersonic engine core makes the perfect power turbine"

gjrq — Wed, 10 Dec 2025 02:36:15 +0000

I also don't think it's necessarily true? A jet engine (which many many power turbines can run off of) can obviously run without cooling water on a hot day just fine.

New comment by gjrq in "A supersonic engine core makes the perfect power turbine"

gjrq — Wed, 10 Dec 2025 01:54:53 +0000

Oh come on, what is this crap? Absolutely no thermal efficiency numbers or anything else you could use to validate any claims. Especially if you are claiming that an aero-derived turbine is somehow going to be better than a purpose-built unit.

The "supersonic engines are better because they are designed to operate at hotter temperatures" argument is particularly insane: turbine efficiency is driven by turbine inlet temperature (already 3000ish C), not ambient temperature.

I suppose it's only right that VCs are going to get scammed by LLM slop.

New comment by gjrq in "Why haven't quantum computers factored 21 yet?"

gjrq — Sun, 31 Aug 2025 18:27:21 +0000

Latest numbers are about 1e6 qubits with 1e-4 error rate: https://arxiv.org/abs/2505.15917. Gates (in the sense the OP means) is harder to quantify in the error corrected context once you compile to the operations that are native to your code. Total compute time of about a week assuming a 1MHz "clock" (code cycle time, for the experts). In some ways this is the harder metric to meet than the qubit numbers.

Note that the magic of quantum error correction (exponential improvement in the error rate goes both ways): if you could get another 9 in qubit fidelity, you get a much larger improvement in qubit numbers. On the other hand, if you need to split your computation over several systems, things get much worse.

New comment by gjrq in "Numerical Electromagnics Code (NEM)"

gjrq — Sat, 05 Jul 2025 18:22:17 +0000

Best one I know of as a direct replacement is AWS PALACE: https://awslabs.github.io/palace/stable/

Of course, you have to interact with the solver through JSON files and provide your own initial mesh. They recently added adaptive refinement but I don't know how well it works. Given what Ansys charges for an HFSS seat though can't complain!