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Comment by thefurdrake | Hacker News Reader

JPL and whoever's behind engineering for the ESA have decades of experience on the Indian space program.

I believe the approach is to shut down all nonessentials and run a heater to keep the battery above failure level during the night. This sounds simple but I'm pretty sure it's an absolute nightmare to design autonomous systems for, especially when you've only encountered those situations theoretically or in a controlled lab environment.

Space is hard. It hates us. It hates life. It hates any form of order and will actively attempt to destroy it. Trying to make things that survive in space is Difficult. It would have been easy to go "Lol india amirite", but the fact is, this is one of the hardest things humanity can do.

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> This sounds simple

Especially for someone who never experienced anything lower than -5°C. Most cars wouldn't even start at -20°C if not equipped with a more powerful generator and battery from the factory. This is measly 20° difference.

It got below 0F a couple years ago and my garage door wouldn't open.

-200C in a vacuum is an entirely-different engineering paradigm as I understand it. Materials just don't behave the way we expect at regular temp/pressure.

There was a whole writeup (on here, IIRC) about the engineering behind the only (or one of less than a handful) types of planes that can transit Antarctica during the cold, dark months.

The fuel freezes, the oil freezes, the rubber in the tires and gaskets becomes brittle, and basically nothing normal works. I recall it being similar-but-different to the SR71 modifications, where the parts are loose and continuously leaks fluids because the materials all change shapes so much in the environment they're designed for. And of course it all has to return to the initial state for (a safe) landing.

The Concorde would get something like a foot longer at speed due to the expansion of the fuselage.

Stupid question, and maybe I should have web searched for it, but why did the fuselage expend? Something to do with the heat generated by the high speed and hence by the high friction?

https://www.flickr.com/photos/anachrocomputer/1829622910/

https://duckduckgo.com/?q=site%253Areddit.com+concorde+pilot...

I made the mistake of going splitboarding in the backcountry a few years back in -20°C with -40°C windchill.

Going up the mountain was surprisingly fine. I even had taken off both my jackets and was just wearing thermals as the heat I was generating working to go uphill was enough to keep me comfortable.

Unfortunately when we reached the top, we also ended up directly in the wind with no available cover. Within the ten minutes it took to put my jackets back on and transition to go downhill, I was nearly hypothermic. I couldn’t even operate my fingers enough to bring the idiot-proof magnetic clasp on my helmet together. The whole group was on the verge of panic to get off the top of that ridge. If we’d stayed there five more minutes, I’m not confident we would have made it back home that day.

I can’t fully express how obscenely, unconscionably, and incomparably cold that was. I have never felt anything like it and I hope never to again.

I once encountered -30°F one winter in Fairbanks. I visited a hot spring where, for some cruel and unusual reason, the facility was designed so you needed to walk about 10 meters out of the (well heated) building to get to the water. And of course, you would do this walk in nothing but just your bathing suit. That was the longest 10m walk of my life.

The cherry on the cake of the experience was that you get into water that is 70+°F but every part of your body above the water line is exposed to -30°F winds. Fun!

Where I grew up, each winter there were a few days that started at -30-40°C. Walking is not too bad (in the squeaky snow) because usually there's NO wind. Cars usually had (plug-in engine-coolant) 'tank heaters' and battery trickle-chargers to keep engines startable.

But there were plenty of snowmobile riders in the area. Some of them who bundled up and attempted to ride at these temperatures learned that their lungs did not work well after a short time.

Living in Ulaanbaatar Mongolia for some time I experienced temperatures of -20 -30 -40 Celsius. Every ten degrees lower I thought it was going to be the same, but was I wrong.

My most notable discovery was when I wanted to jump start my car, because the battery died due to the cold. I was about to bring out my jumper cables when my local friend told me to bring the cables inside first.

I didn't understand why and naively ignored what he said only for the rubber jumper cables to literally crumble in my hand, breaking as I tried to straighten them.

Mongolians are so resilient and have so much knowledge on how to survive in extreme weathers with a simple yurt and a livestock of 100 sheep goats and horses.

Most modern cars will happily start at -20°C and many will start at -30°C without any special additions (don't ask me how I know, you just need to know what you are doing). Of course it's not -200°C, but one thing to remember is that there is no temperature in the vacuum. The temperature of the Lunar surface is not it. An object without heating can easily reach lower temperatures there, yet it may not be that hard to keep that object warm as e.g. somewhere in the Arctic as there is no conductivity, only the radiation heat transfer.

> Most modern cars will happily start at -20°C and many will start at -30°C without any special additions

A couple years ago temps here went below -25° and there were a lot of cars which didn't go nowhere. Sure, some of them just had a battery too low from the usual urban minimal distance travel, but I heard enough rants from and about people who was forced to abandon their car and use the public transport or taxi. Diesels without an engine heater were among them.

> don't ask me how I know, you just need to know what you are doing

Ye, have an 'offline' (lol) charger for your car battery or have a 'kick-starter' kit. The thing is what the cars sold here are prepared for the winter conditions, yet many of them failed at a slightly lower temps - which again shows how a mere 5° difference can be way too much even for things what work otherwise just fine.

People just don't care about their vehicles, that's why. There are multiple examples of even diesels starting at -25°C without heating. All my cars have been gas and while starting them at -30°C required some magical actions (like turning on headlights briefly to warm the battery up or depressing the clutch if you have a manual transmission) they all started most of the time. No extra tools or devices were necessary.

> or depressing the clutch if you have a manual transmission

What exactly does depressing the clutch do as compared to not doing it and starting the vehicle in neutral? Is it to reduce the engine load further? Or something else?

Standard gear box oil is 80W90, which at -30C (even at -20C) turns into a thick jelly. Even in neutral starter has to move gears in that jelly. So normally you don't want to release the clutch until engine is warm enough and stable, and even when you do release it (in neutral) you do it slowly, sometimes in multiple attempts to avoid engine stalling, like starting on a steep hill. I haven't tried automatic at those temperatures, but ATF is much less viscous, so it should be much easier on the starter at low RPM.

> It hates any form of order and will actively attempt to destroy it.

If you are talking about ever increasing entropy, it applies to any environment. But keep in mind that the Moon itself is a manifestation of order. If it hadn't been the case we would have been observing a cloud of dust and gas where our Solar system is.

Oil and water separating into layers when mixed also looks orderly, but is in fact the higher entropy state https://physics.stackexchange.com/questions/111955/homemade-...

Yes, entropy increases in the salad dressing, but only when it's insulated (in reality we can't consider salad dressing outside of the Earth gravitational field, but let's say the Earth is insulated too). Now imagine that the extra energy (i.e. generated heat) has dissipated (either out of a window or, if we consider the Earth too, into the space). Is it still an increase of entropy? Our Solar system is not a closed system, the extra heat that was generated by creation of planets has dissipated (and is continuing to do so). So in the end the entropy of the Solar system is lower, i.e. we have more order, at least in our vicinity. Possibly in the whole universe since it's (presumably) expanding. Anyway, I wouldn't apply 2nd law of thermodynamics to the whole universe, we have no idea what happens at that scale.

Cosmic radiation hates electronics. Vacuum is inexorable.

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