Bitter Lessons from the ISSpresso

sam1r•about 2 hours ago

The flow diagram provided for fracture control is incredible. Quite a work of art. [1]

[1] https://substackcdn.com/image/fetch/$s_!AOMG!,f_auto,q_auto:...

Update: After staring at this flow diagram for quite some time, I realize it's actually the most robust, "complete-seeming" finite state machine I have seen used in the real world.

xoxxala•about 2 hours ago

That was an excellent read for explaining why space isn’t just hard, but expensive.

jacknews•about 1 hour ago

Good read.

"Since that time, I’ve learned that small heaters (like coffee makers or kettles) can be kryptonite to an inverter, and that this is common folk knowledge among solar installers."

Is there any more on this? It can understand inductive loads maybe challenging inverters but resistive loads should be easy? Is it an issue of cheap inverter design, or something more fundamental?

aidenn0•5 minutes ago

Assuming the heating element has a positive temperature coefficient (which seems likely), there will be inrush current greater than the operating current.

As an extreme example, a tungsten filament in a lightbulb would rise to 1500C (2700F) which with even a small temperature coefficient can mean inrush current 10x higher than the operating current.

Fr0styMatt88•about 1 hour ago

From a quick Google that kinda makes sense, it’s just the strong, _sustained_ power draw that gives them issues. So I’d say fundamental AND inverter design — imagine pushing 2kW continuously through an inverter.

It’s funny, power use can be really unintuitive. Try convincing someone that using the big air conditioner for heating is more efficient than using that little plug-in bar heater. Or yeah, a power board with 8 tiny wattage wall-warts isn’t using a lot of power.

I could probably run my big fridge overnight off my portable battery generator, but it wouldn’t run my small electric kettle without putting it into a special mode and for nowhere near as long.

margalabargala•40 minutes ago

That doesn't make sense to me. On a cheap RV inverter maybe, but on solar for a house? The inverters should be rated to continuously output whatever the panel is generating. It shouldn't care whether the 2kW is going back on the grid or into your water kettle, it should be doing that all day every day.

zhivota•27 minutes ago

Typical hybrid inverters have an output rating around half the theoretical max input of the panels. This is due to theoretical max of panel input being very rare or even impossible in normal earth conditions, the presence of an attached battery to soak up part of the input, and the general cost benefit trade off of solar equipment (more throughput means more heat, means bigger heatsinks, means heavier and more expensive).

You can definitely get equipment that can do symmetrical input/output, but if you actually model out the supply and demand curves on the system it's not usually going to be worth the extra up front expense since peak input is a small portion of the day and that extra hardware will mostly sit idle.

For that matter people often design systems where peak input can't even be accepted by the inverter and the extra power is just wasted, because it's more valuable to have a steady input over a long period than to maximize the daily peak.

pavel_lishin•2 days ago

The Pressurized Payloads Interface Requirements doc is kind of interesting. Lots of diagrams & such that would be great for art projects.

Bitter Lessons from the ISSpresso

⚡ Community Insights

Discussion (11 Comments)Read Original on HackerNews