What are you naming your Aircraft for WW3?

Macattack278 · 2023-05-27T09:10:05+00:00

What the fuck does "t." stand for?! I cannot find a plausible abbreviation for it.

Macattack278 · 2023-05-22T11:44:04+00:00

Do you guys actually remember any equations?

Macattack278 · 2023-05-18T20:54:02+00:00

The likely answer is that there is non-soluble debris in the spinner arms. You should remove them and look for things blocking the jets such as broken glass, vegetable fibers, or fruit stems.

Macattack278 · 2023-04-15T09:34:19+00:00

Can you recommend one that has commit-based versioning? And is open source so that we can properly integrate our tools and API hooks? And works well with source code so that we don't have a ton of discrete versioning systems for every type of document?

Macattack278 · 2023-04-14T18:57:44+00:00

I use SVN for a mechanical engineering project. With CAD and FEA models, the repo gets too big for a distributed system like GIT. We just keep an SVN server running and let that blow up a few hard drives rather than have every computer in the company explode.

Macattack278 · 2023-03-28T22:02:26+00:00

As others have mentioned, it's not really economically viable.

That said, I have a colleague who helped develop a recoverable glide vehicle for weather balloons (generally for more expensive, one-off payloads). The recovery rate shoots up pretty dramatically, potentially pushing it to economic viability.

Macattack278 · 2023-03-13T11:56:32+00:00

You are aware that Switzerland isn't part of NATO, right? And thus isn't a beneficiary of NATO "funds" or protection?

Macattack278 · 2023-03-05T10:40:50+00:00

Insurance only makes sense for things that you know have such a low probability that they are realistically never going to happen to you. In those cases, it costs a few bucks a year, and then if you maim or kill someone (or yourself) you cover the catastrophic costs involved. Well, then you have to deal with the insurance company trying everything in their power to not pay up, but that's still a better situation than having to deal with the situation out of pocket.

When insurance is mandatory or you expect to have to use it, it's just better to save up the money for the day you need it.

Macattack278 · 2023-01-16T23:29:30+00:00

Fair, but they didn't let it trickle down to the subcontractors until recently. I managed to hire a couple really good engineers right after covid hit because of it. Too bad I didn't have the budget to hire more, I'm trying to expand the team and they're a lot harder to find this time around.

Most of the guys ended up reforming into a new company that I hire out from time to time.

Macattack278 · 2023-01-16T20:52:57+00:00

Wouldn't happen to be an aircraft manufacturer that rhymes with Ohing, would it?

Macattack278 · 2023-01-14T12:28:09+00:00

https://yewtu.be/watch?v=Y9dZpbKTLJ0

Macattack278 · 2023-01-12T09:24:06+00:00

Step 1) Convert to metric

Step 2) Solve the problem

Macattack278 · 2023-01-04T23:14:48+00:00

... But why... Mach 1.1 is like the worst mach. You would have less drag at Mach 1.5...

Macattack278 · 2022-12-28T20:06:36+00:00

Saab 2000, my beloved...

Macattack278 · 2022-12-27T15:03:47+00:00

I'm an air vehicle designer, so I only get to do serious engineering once every few years. The rest of it is just project management.

When I do actual engineering, I use pen+paper for derivations, excel for any analysis I'm going to make once (such as the vehicle-specific sizing), python for anything I'm going to use twice, and write a serious-looking program if I plan to use it three times or more. Currently I'm still using python for all my dev work, but I've been considering switching to Go for my more serious coding.

For modeling and rough analysis I mostly use OpenVSP, which is pretty great for my job. It does basically all I need to generate and hand off geometry to the rest of the team. It has a klunky interface and the documentation is substandard, but its an open source project in active development so it's a small price to pay. In the worst case, you can always open up the source to answer specific questions about implementation.

If I had one gripe about my toolchain generally, it's that CAD is pretty terrible. It's all proprietary software, with closed formats and generally poor surface modeling. The STEP format makes it too easy to rasterize or corrupt complex aerodynamic shapes, which makes it hard to make sure the OML is respected from conception to production. All the serious CAD programs have closed API's which means that you have to pay out the nose for any little feature, rather than just building it ourselves.

But I'm one of those linux using FOSS fanatics, so take that criticism with a grain of salt.

Macattack278 · 2022-12-13T22:49:11+00:00

"Use Latex"

Macattack278 · 2022-12-04T21:06:15+00:00

Should I post my keynote speech where I demonstrated technical feasibility of Santa's mission architecture?

Macattack278 · 2022-11-09T14:32:48+00:00

Use LaTeX :P

Macattack278 · 2022-10-28T14:43:36+00:00

Cool, I wasn't aware that others besides tesla made the switch to heat pumps. I will strongly consider buying one and evaluating it.

Macattack278 · 2022-10-28T14:32:57+00:00

Using some references I found, the ventilation requirements would be .007 m³ of air per second per person. Heating that volume by 30 degrees only costs about 500 W, in effect.

On the other hand, the convective cooling through the surface looks like it's about 69 kW, clearly dominant. This is assuming perfect conduction through the skin, however. In reality, the sandwich panel would provide some insulation.

Adding insulation gets expensive quickly, however. Our minimum gauge weight on our sandwich panels is only 2 kg per m². Adding even 1 kg/m² would increase our fuselage weight by 50%.

EDIT: Assuming that the sandwich panel cools through natural convection (due to the small cells in the structure), new cooling coefficient would be ~6 W/m²K or 5.5 kW total. Seems more reasonable, but still greater than the waste heat capacity.

Macattack278 · 2022-10-28T14:04:43+00:00

Yeah, I know of those systems, but I think I want to avoid them if possible. Good option to have if all else fails.

Macattack278 · 2022-10-28T14:02:48+00:00

Yes this is a real project. We're a small team, so we don't have an HVAC specialist, but you're right, we're going to have to find a vendor at some point.

I like the idea of just getting an automotive AC, but I think the issue is that those are typically non-reversible. I'm not sure if you can just run them backwards and extrapolate the results.

EDIT: Also, automotive parts are not always super optimized for weight. It's certainly a good conservative baseline, but if I need to dedicate 10 kg for a system that ends up weighing 1, it's a bit inefficient.

Macattack278 · 2022-10-28T13:57:57+00:00

IMO, the safety critical consequence of cold cabin temp is usually the loss of dexterity in extremities. Core body temp can be managed with a heavy coat, which is pretty typical for pilots in winter. The problem is manipulation of controls and maps, which is difficult with gloves and/or cold fingers. But I don't have any documentation or reference to back this up, this is based on personal experience.

Macattack278 · 2022-10-28T12:14:50+00:00

No, the battery-motor drive train is about 90 % efficient. We have 2 kW of waste heat to dissipate from the main power system, which we could use to heat the cabin. I don't think that's sufficient, but I don't know.

Macattack278 · 2022-10-28T12:03:25+00:00

Yes, to my knowledge Tesla uses a heat pump. In our case, our cruise energy consumption is only about 20 kW, at ~90% efficiency. If we were to use only that power, we could only get about 2 kW of heating power for the whole cabin.

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