Random links #19

Written on 12 February 2020, 04:22pm

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3 reasons to go vegetarian/vegan/flexitarian

Why do the helicopters crash more often?

  • they are used in risky situations: search and rescue operations, military, medical evacuation, etc
  • more vulnerable than planes to bad weather
  • they fly at lower altitudes, so higher risk to hit obstacles and less time to recover in case things go wrong
  • they take off and land more often than the planes (shorter routes)
  • more moving parts, so more possibilities to fail
  • can’t glide
  • a bit more difficult to control than planes


Why the commercial aircraft do not have a parachute?

Well, some of the small planes do. But the commercial aircraft don’t and are unlikely to have in the future because of how physics works:

  • if there would be a single parachute, the shock when it will be engaged will simply destroy the aircraft structure
  • multiple parachutes make things impractical: they would have to be deployed in the same time, would increase the total weight and significantly decrease the payload
  • a parachute system would require a very complex maintenance process (periodic tests, replacements, etc).
  • it would also require a complex safety system to prevent accidental deployment
  • a parachute system for a large airplane (like the Airbus A380 – 850 people or Boeing 747 – 500 people) will have to ditch everything except for the pressurized passenger cabin. Again, not practical, and how do you control where the rest of plane ends when the pilot engages this system?


OK, then why don’t the airlines give parachutes to the passengers?

Simply put, they are unlikely to save lives.

  • first problem: at which stage of the flight do you tell the passengers to use the parachutes? Life vests are simple, everybody knows when to use them. But parachutes?
  • the physics laws prevent the hatch to be opened at high altitudes. So an explosives system would be needed if you want to jump at 35000 feet (10700m)
  • if you still want to jump at that altitude, you would likely enter a thermal shock (negative 60 degrees Celsius) and lose conscience in a few seconds due to the lack of oxygen. Unlikely to land alive.
  • so you will have to blast the door and jump somewhere lower, maybe 15000 feet (4500m). Except – you’re not alone. A few hundreds passengers will try to do the same thing before the plane hits the ground.
  • assuming that the passengers can jump in an orderly manner, and allocating 10 seconds per jump, you would still need around 40 minutes for a 250 passenger plane to be evacuated in mid-air. Only 20 minutes if you open 2 doors.
  • if you manage to jump, you will hope to avoid being sucked into the engines (if you use the front doors) or sliced by the horizontal stabilizers (if you use the back doors). More importantly, you will pray to avoid fatal injuries when the parachute deploys: your plane will probably fly way past the safety jump speed limit
  • BTW, did you ever strap your parachute and actually jump from a plane? And did you ever land by yourself?
  • You see, the chances of coming down alive using a parachute are becoming increasingly small. Not to mention that you might land in the middle of a freezing ocean, with the parachute coming down on you.
  • Also, most of the aircraft accidents happen during takeoff and landing, when the parachutes simply won’t work



Random links #17

Written on 7 October 2019, 02:49pm

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Electric planes

Air travel is bad for the planet—and travelers may finally be getting the message.
The change in mindset is due to increasing awareness of the issue thanks to attention-grabbing protests, like when activist group Extinction Rebellion shut down Heathrow Airport and climate warrior Greta Thunberg sailed across the Atlantic in a zero-emissions yacht to speak at the UN’s climate summit.

Does flight shaming work?

Solution? Hybrid or full electric planes. Also tested by NASA.

Heavyside, from Kitty Hawk is really silent and has a range of about 100 miles

Radiation in space is a big deal

If we want to prepare astronauts to fly to Mars, then we have a lot of problems to solve when it comes to health and well being. There are both psychological (isolation, confinement, sleep disturbance, etc) but also physiological (micro-gravity long time effects, radiation) factors to overcome. One of the most important is the radiation.

Radiation on Earth is about 4.6 mSv/year. On the Moon – 300/400x. On Mars – 1000x.

How can we reduce the radiation impact? Medical selection of the most resistant individuals, shielding (the ISS has 3 highly shielded areas) and medication. Hibernation is also an option, not explored yet.

Radiation sensitivity decreases with age. A teenager is 2 times more sensitive than a 30-years old adult, which is in turn 2 times more sensitive than a 50-years old.

Space travel affects the astronauts’ immune system. Various factors play a part in this process, i.e. weightlessness, cosmic radiation, isolation and the inevitable stress. At the request of European, American and Russian space agencies, SCK•CEN tests the blood of astronauts when they return from a long space mission. We perform analyses using advanced biochemical and molecular techniques.
Long-term exposure cannot be avoided during long distance missions, e.g. to Mars – for which the return flight takes 18 months. Sensitivity to cosmic radiation varies considerably between people, and consequently also between astronauts. 

The Belgian Nuclear Research Centre

Time matters

The Tesla dashcam writes its rolling clips in the /recent folder. The manually saved clips are stored in the /saved folder. Recently Tesla introduced the Sentry mode, which automatically saves events when the car is parked (ex. a person or a car is passing by).

The Tesla engineers thought that it’s appropriate to save these clips not in a dedicated folder (like /sentry), but in the same /saved folder where the manual clips are saved.

The outcome? When I want to look for a video that I manually saved, I have no easy way to find it. Sentry mode produces a huge number of videos, sometimes 10 videos for a half an hour spent in a busy parking. Finding the right folder among literally hundreds of other folders is like finding a needle in a haystack.

Compare this to the following bit:

One day Jobs complained to Larry Kenyon (the engineer of the Macintosh OS) that it was taking too long to boot up. Kenyon explained why reducing the boot-up time wasn’t possible, but Jobs cut him off: “If it would save a person’s life, could you find a way to shave 10 seconds off the boot time?”. He then showed on a whiteboard that if the Mac had five million users and it took 10 seconds extra to turn it on every day, that added up to 300 million or so hours a year — the equivalent of at least 100 lifetimes a year. After a few weeks, Kenyon had the machine booting up 28 seconds faster.

Steve Jobs Insane Productivity Secrets

Random links #13

Written on 19 March 2019, 10:20am

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Biohack is just a fancy buzz-word for common-sense advice about improving your life. The most important ones are:

  • sleep well
  • eat well
  • move
  • spend time in nature
  • socialize


I am currently reading Solenoid, by Mircea Cartarescu, a surrealist novel that shows, among others, the challenges of growing up in Bucharest during the communist era.

In a nutshell, the novel is presented as a manuscript of a failed writer who teaches Romanian at an elementary school in Bucharest, hates his job and wishes to find an escape route from the confinement of his body and the three-dimensional world around it.



MCAS (Maneuvering Characteristics Augmentation System) seem to be the faulty mechanism behind the Boeing 737 Max recent failure.
If an outside sensor measuring the angle-of-attack reports that its nose is aimed too high, the MCAS is programmed to automatically lower it, allowing the plane to regain speed and lift. But if this sensor is broken (and it looks like there was no redundancy), then the MCAS will be incorrectly trigerred, causing the aircraft to dive.
A longer explanation here.


– If you could convince an organization to take only one action to be more secure what would it be?
Collect less data and get rid of it faster.


A good reason to use the dark theme whenever you can