Software powering Falcon 9 & Dragon - Simply Explained

hi there my name is xfj and as you might know i am a developer but I'm also a huge SpaceX fan and that got me thinking what software and hardware powers the Falcon 9 Falcon Heavy and Dragon let's first take a look at what challenges the hardware and software of a spacecraft faces when it is being launched into space first of all it's very hard to get your craft into orbit around the Earth a launch on top of a rocket causes a lot of vibrations and that means that the craft itself and the electronics have to be able to withstand that and once you get into orbit you're welcomed by even more challenges dragon for instance has to be able to cope with intense heat when it's facing the Sun but also intense cold when sunlight is being blocked by the earth these temperatures range from minus 150 all the way up to 120 degrees Celsius but the biggest problem for the electronics is radiation this radiation comes from high-energy particles that are ejected by our Sun particles trapped in Earth's magnetic field and even cosmic rays or particles from outside our solar system these particles can have a pretty severe effect on the systems inside a spacecraft one of the biggest problems is what's called a bit flip this occurs when a high-energy particle hits the memory or the processor of the spacecraft if it hits the memory it can cause a zero to become a one essentially corrupting a part of the memory luckily though the hardware on board SpaceX vehicles can attack these bit flips and fix the corrupted memory by using parody bits no big deal however when the processor is hit with radiation it can cause the result of a calculation to be completely incorrect to demonstrate this let's ask a processor to calculate 10 plus 10 in binary that would look like this and the result is obviously 20 no surprises there but let's now take a look at what happens when a bit flip occurs while performing this calculation we still ask the processor to calculate 10 Plus 10 but because of the bit flip the processor is actually calculating something completely different right now it will say that ten plus ten equals twenty four because one of the bits flipped while running the calculation wrong calculations can have pretty severe effects on spacecrafts this was demonstrated by the maiden flight of the Ariane 5 rocket in 1996 it didn't suffer from a bit flip but 40 seconds into the flight the rocket software tried to put a 64-bit number into a 16-bit address causing the number to be truncated and be completely different the Rockets avionics then continued to perform their calculations with this wrong number and performed an abrupt course correction because it thought it was going the wrong way the vehicle eventually broke up because the aerodynamic stress was simply too high now back to SpaceX how did they handle the problem of radiation well they assume that you can't protect electronics completely from radiation and they design their systems with this in mind instead of using expensive radiation hardened parts SpaceX uses off-the-shelf components let's look at dragon first according to John Moore Ettore previous director of SpaceX vehicle certification each dragon is equipped with three flight computers each of these flight computers is powered by a dual-core x86 processor the computers however don't use this multi-core capability instead they execute each calculation on the two cores individually and then compare the results so three flight computers with each a dual-core processor can be seen as six independent computers that are constantly checking each other's calculations if one of the flight computers is hit with radiation and produces a wrong calculation the others will spot it and when that happens the malfunctioning computer will be rebooted automatically to prevent further errors after rebooting the computer has to perform what's called a resync it has to get up to speed with what the vehicle is doing so it copies the memory of the other two computers and runs the same programs a bit like rebooting your computer with the option to restore all your windows when you log back in dragon can even handle a situation where all three of its flight computers are by radiation at the same time although that is very unlikely to happen besides three flight computers dragon has 18 other systems on board that also use triple redundancy computers and that brings a total amount of processors up to 54 and that is just for a single Dragon capsule but dragon isn't alone also the Falcon 9 has redundant systems it has three computers for each engine and triple redundancy flight computers which means that it carries 30 processors at least that was the situation in 2012 right now it's possible that the Falcon 9 has even more processors to handle the landing now at this point you might be thinking hang on does NASA really allow SpaceX to use regular hardware components the ones you and I can buy on Amazon while actually yes NASA doesn't require the use of radiation hardened components instead they require SpaceX to do extensive research into what effects the radiation can have on their spacecrafts if they know how they'll be affected they can compensate for it in fact this is called a radiation tolerant design and it is different from a radiation hardened design nasa itself doesn't use radiation hard part's everywhere the International Space Station for instance uses a mix of radiation hardened parts but they also use regular laptops for some controls even some parts on the Space Shuttle were radiation tolerant instead of radiation hardened but back to SpaceX how do they select their parts while they have two conditions first of all the parts have to be capable enough to handle their tasks pretty obvious and secondly they take into account what tooling is available for that particular part tooling determines what kind of people SpaceX can hire off-the-shelf hardware is pretty generic and uses software and tooling that a lot of developers already know and that means that SpaceX has less trouble finding great engineers radiation hardened parts however only work with special programming languages that few people know thus limiting the ability to hire new people off-the-shelf hardware is also cheaper and that allows SpaceX to extensively test these systems John moratoria said that at one point over 40 flight computers were sitting on people's desks for testing and development you simply cannot do that with expensive and hard to come by hardware but enough about all this hardware what about the software that controls everything while the operating system of choice at SpaceX is Linux it runs on the desktops of the engineers and it powers its vehicles using Linux everywhere allows them to streamline the development process and use the robust tools that come with it the programming language of choice is C++ and they use it for two main reasons first it allows SpaceX to hire a lot of brilliant people because the language is still relatively popular and secondly they benefit from the large C++ ecosystem no need to create custom software when you can just use the tools that developers already know like GCC and gdb for instance but Linux isn't the only platform that is being used they also use LabVIEW a graphical programming tool that runs on Windows it is used to visualize the lemma tree that they get from the Falcon 9 or a dragon during flight and ground teams use it to keep an eye on important metrics another interesting fact is that SpaceX tries to share as much code as possible between its vehicles the biggest advantage of this is that bug fixes for one vehicle are automatically pushed to the other vehicles as well oh and another interesting fact is that game developers are usually a good fit for SpaceX because they are used to writing code that runs in environments where memory and processing power are constrained the last thing we'll take a look at is how SpaceX monitors their software and vehicles engineers are encouraged to add metrics to everything they can think about and when a vehicle is being used all these logs are collected and analyzed by programs who raise an alarm if something is not within the safety margins all these metrics are then stored together with the source code that was running at the time if something goes wrong with the vehicle SpaceX can recreate the exact environment to reproduce a problem and fix it and finally they're using continuous integration to automatically test all the code that is being written by engineers they even have test sense with all the components of a falcon 9 bolted on so they can simulate a complete flight to discover potential problems now more details about the used hardware and software aren't really available and that's because the United States government considers it classified a rocket like the Falcon 9 is basically a missile that goes to space so in the wrong hands the technology could be misused and cause harm but even with limited information we got a pretty good view and what software and hardware is being used at SpaceX and what challenges the teams face so that was it for this video if you liked it hit the thumbs up button and consider subscribing also follow me on Twitter for more updates and as always thank you very much for watching you

Channel: Simply Explained

Views: 891,555

Rating: 4.9139471 out of 5

Keywords: lesson, course, training, basics, basic tutorial, beginner, best practices, dummies, fundamentals, free, getting started, introduction, howto, tutorial, learn, space, nasa, spacex, iss, shuttle, space shuttle, space station, falcon, falcon 9, falcon heavy, dragon, spacecraft, c++, linux, vehicle, electronics, bitflip, bit flip, radiation, earth, orbit, memory, processor, x86, binary, ariane, ariane 5, accident, labview

Id: N5faA2MZ6jY

Length: 9min 52sec (592 seconds)

Published: Tue Feb 27 2018

Reddit Comments

[u/Ckandes1]

I liked this, learned a lot. Subscribed, his explanations are great

[u/ergzay]

This video has several inaccuracies.

1. Radiation hardened hardware doesn't require special programming languages.
2. Everyone uses gnu compiler suite nowadays, no matter your platform.
3. Real time linux is quite common everywhere. VxWorks (the previous common OS for NASA spacecraft) is dying pretty rapidly.
4. Launch vehicles don't care about radiation hardening. Most launch vehicles don't use radiation hardened parts.

[u/scr00chy]

Related article about radiation tolerant design at SpaceX

[u/Faaak]

I would love to have a more in-depth video. Like how their CI-environment work, pictures of their test boards, how their simulator works, etc.

There's another video of the same type by a guy that explain how they do CI, but it's still superficial.

[u/TheCoolBrit]

Great vid, originally posted some time ago in SpaceX Lounge to see comments.

[u/NelsonBridwell]

Another advantage of C++ is that it is possible to create very efficient, highly optimized native machine language code that will run as fast as possible on the onboard processors. It doesn't have the overhead of other languages like C# (garbage collection) or python/Java interpreters.

[u/driedapricots]

If you work in the industry, and actually know what's going on, this video is quite inaccurate and hard to watch.

[u/keezah]

Great video, big thumbs up