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We are the SpaceX software team, ask us anything
- deleted 6y ago[deleted]
- jonathanaird 6y agoWhat language/framework is the GUI for the controls written in?
- jve 6y agoRelated: Software Engineering Within SpaceX https://news.ycombinator.com/item?id=23403800 https://news.ycombinator.com/item?id=23403800
- nsajko 6y agoAlso "What computer and software is used by the Falcon 9? (2015) (stackexchange.com)" from 5 days ago - https://news.ycombinator.com/item?id=23368109 https://news.ycombinator.com/item?id=23368109
- jcun4128 6y agoDang the influx of questions wonder how they decide what to answer.
- adambyrtek 6y agoThis is Reddit so probably by upvotes?
- jcun4128 6y agoYeah but I also wonder how many people filter/read new and vote vs. just asking whatever... if they could average the questions that would be interesting/frequency of mentions... anyway be curious what questions are asked. ~600 comments under an hour? dang edit: oh comments are randomly ordered interesting
- cryptonector 6y agoMore-upvoted comments float up. That's how Reddit works.
- pjscott 6y agoTo expand on your edit: 1. This comment thread shows comments in random order, so you're not seeing the more upvoted questions bubble to the top the way they usually would, which prevents winner-takes-all feedback loops in the voting. 2. People browsing through the thread may upvote good questions, but currently the scores are hidden in order to avoid bias. 3. Once the thread has been up for a while, the people doing the AMA can just re-sort to show the highest-voted comments first, which will give a good starting point for which questions to answer.
- jcun4128 6y agoYeah I'm glad they did that. The score hidden thing is interesting, I see some people do that at will, I'm a person affected by down votes haha like "oh no someone disagreed with me" anyway... pretty cool.
- RedShift1 6y agoWhat kind of computing hardware is used inside the rockets? Off the shelf Intel or AMD cpu's setup in some kind of redundancy or custom hardware? How does the redundancy work, how many CPU's can fail before the rocket can't be controlled anymore? Are they all located in the same place in the rocket, why/why not?
- ponker 6y agoNo way. Anything that costs a lot of money runs industrial computing like the RAD750.
- mshook 6y agoThere are some answers here: https://space.stackexchange.com/questions/9243/what-computer-and-software-is-used-by-the-falcon-9 https://space.stackexchange.com/questions/9243/what-computer... IIRC it was the same thing they said during the launch of the Dragon capsule so yeah they don't use crazy RAD stuff: SpaceX uses an Actor-Judge system to provide triple redundancy to its rockets and spacecraft. The Falcon 9 has 3 dual core x86 processors running an instance of linux on each core. The flight software is written in C/C++ and runs in the x86 environment. For each calculation/decision, the "flight string" compares the results from both cores. If there is a inconsistency, the string is bad and doesn't send any commands. If both cores return the same response, the string sends the command to the various microcontrollers on the rocket that control things like the engines and grid fins. The microcontrollers, running on PowerPC processors, received three commands from the three flight strings. They act as a judge to choose the correct course of actions. If all three strings are in agreement the microcontroller executes the command, but if 1 of the 3 is bad, it will go with the strings that have previously been correct. The Falcon 9 can successfully complete its mission with a single flight string. The triple redundancy gives the system radiation tolerance without the need for expensive rad hardened components. SpaceX tests all flight software on what can be called a table rocket. They lay out all the computers and flight controllers on the Falcon 9 on a table and connect them like they would be on the actual rocket. They then run a complete simulated flight on the components, monitoring performance and potential failures. SpaceX engineers perform what they call "Cutting the strings" where they randomly shut off a flight computer mid simulation, to see how it responds. Dragon uses a similar triple redundant system for its flight computers.
- HALtheWise 6y agoTo unbury the lede, this is happening at tomorrow, Saturday June 6 at noon PST
- travisporter 6y agoOff topic, but is there a nitter/invidio.us equivalent to reddit? After HN, I find reddit and old.reddit to be so cluttered I can't stand it
- 4rollingstock 6y agoHave you tried i.reddit? Its their old-school mobile website, super simple interface. https://i.reddit.com/ https://i.reddit.com/
- deleted 6y ago[deleted]
- travisporter 6y agoLove it! Thanks!!
- dependenttypes 6y agothere is snew.notabug.io but I do not know if this is what you are looking for.
- thecleaner 6y agoReal jewel from the AMA - what "web technologies" did you use for the UI But one great question - What practices did you use to ensure there are no bugs ?
- nsajko 6y ago> Real jewel from the AMA They did use Chromium and Javascript for the UI at least a few years ago. See the stackexchange posts. EDIT: also see the old AMA: https://www.reddit.com/r/IAmA/comments/1853ap/we_are_spacex_software_engineers_we_launch/ https://www.reddit.com/r/IAmA/comments/1853ap/we_are_spacex_...
- macintux 6y agoI was fond of the "do you think AI will get us FTL travel" question.
- jonnypotty 6y agoDo you have any tools to attempt prove correctness of critical code beyond traditional testing?
- hartator 6y agoYou have to ask that on the Reddit.
- jonnypotty 6y agoOh. Oops.
- pinacarlos90 6y agoHow do you go about organizing/prioritizing work, and executing? 1) what workflow methodology you use (e.g. scrum/sprint, Kanban, etc) 2) where does requirements come from? 3) how granular is your code-review process?
- O_H_E 6y agoYou gotta ask on Reddit.
- dmead 6y agowhat happens if node has to garbage collect during launch?
- deleted 6y ago[deleted]
- unnouinceput 6y agoboy that thread at reddit took like 20 seconds to close my firefox tab that was in it. Never seen a tab to take that much to close.