News SpaceX heavy-lift vehicles: Launch Thread

Discussion in 'Science and Technology' started by XCV330, Jan 24, 2018.

  1. StarCruiser

    StarCruiser Fleet Captain Fleet Captain

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    Houston, we have a problem...
    Around that time, I had to learn x86 machine code...

    Push
    Pull
    Pop
    Stacks
    Registers....

    Gott im himmel!
     
  2. XCV330

    XCV330 A Being of Pure Caffeine Premium Member

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    TOS-BSG is a holographic universe written in..
    [​IMG]
     
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  3. StarCruiser

    StarCruiser Fleet Captain Fleet Captain

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    And you haven't burned it yet!?! Are you MAD?
     
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  4. Santaman

    Santaman Vice Admiral Admiral

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    Atari Basic.. yeah.. in the old days I tried to create some stuff in that...
     
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  5. Asbo Zaprudder

    Asbo Zaprudder Vice Admiral Admiral

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    I've used Basic (several varieties, some actually not bad), Fortran (several varieties), Algol, Algol 68, Pascal, x86 assembler, 68000 assembler, C, C++, Java, sh, csh, ksh, bash, Matlab, PowerShell, Python, Ruby, Miranda, Lisp, JavaScript, SQL, perl and many others I either can't recall or don't wish to. I don't claim to be anything near expert in any of them. Cobol I never touched. Ada likewise. I'm so old that I was using paper tape and punched cards at one point. I've even used computer consoles with vector rather than raster graphics displays. I used light pens years before I used a mouse.
     
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  6. Cyanide Muffin

    Cyanide Muffin All hail Doctor 13 Premium Member

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    I love UK based micros, we had a Jupiter Ace. Which was a real oddball.
     
  7. Santaman

    Santaman Vice Admiral Admiral

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    I'm not sure what spacecraft are using nowadays, in the past it was purpose built, IBM based hardware running single task software to keep things as robust as possible.
     
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  8. StarCruiser

    StarCruiser Fleet Captain Fleet Captain

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    And that's the way anything critical should be... Dedicated to a single task - as bullet proof as you can make it (with an option to reboot when Murphy kicks in)!
     
  9. Cyanide Muffin

    Cyanide Muffin All hail Doctor 13 Premium Member

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    Are modern spacecraft designed to play nice after a full reboot?
     
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  10. Santaman

    Santaman Vice Admiral Admiral

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    I have no idea if they still keep it as simple as in the past, if it were my call systems for a spacecraft would have everything in ROM, some RAM and a CPU good enough to run its tasks and thats it, a reboot would just mean that it would reload the needed stuff back to RAM and you can continue to use the machine as if nothing happened.

    I assume that they still would build systems like that, a reboot would purge RAM and the system would reload everything the way it was when it was switched on the first time, kinda like the old home computers.
     
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  11. Cyanide Muffin

    Cyanide Muffin All hail Doctor 13 Premium Member

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    I remember watching a movie and can't recall the name but they asked that very question and no one had ever done that on one of their craft due to the expensive nature of them. I just laughed. I mean no one ever thought to test what a reboot would do.
     
  12. Asbo Zaprudder

    Asbo Zaprudder Vice Admiral Admiral

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    It's kind of useful to be able to change the software in flight though - as on the Voyager spacecraft, where the communications algorithms were updated to handle the increasingly vast distances from Earth and consequent reduced bandwidth and degraded signal-to-noise ratio.
     
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  13. Santaman

    Santaman Vice Admiral Admiral

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    That is true as well. :)
     
  14. publiusr

    publiusr Vice Admiral Admiral

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    I wish that had continued. I'm convinced that--somewhere on this planet--is a savant who can think in binary and write a code so tight no one could hack it.

    It'd drive him insane and take 20 years to code, but....
     
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  15. Cyanide Muffin

    Cyanide Muffin All hail Doctor 13 Premium Member

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    Anything's possible.
     
  16. Asbo Zaprudder

    Asbo Zaprudder Vice Admiral Admiral

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    It's impossible to decrypt ciphertext that is encoded using a one-time pad, provided the pad is not reused and is not available to an adversary. Modern asymmetric key encryption is based on "trap-door" algorithms that are easy to compute in one direction and very difficult to compute in the other direction - an example being the factorisation (very hard) of the product of two primes (very easy).

    I'd be interested to know if there is a publicly available encryption technique that can mix two messages with two keys so that each key decrypts only one of the messages. The message would look to all intents and purpose like ciphertext encrypted using a single key, so if the authorities demanded a key, one could hand over the key to a decoy message in the pair. However, perhaps statistical analysis would reveal that the ciphertext contained much more entropy than expected and that another message was probably present.

    The most similar method that I can think of was "chaffing and winnowing," which was mooted about 30 years ago by Ron Rivest, but that technique is really neither cryptographic nor steganographic in nature.

    ETA: Two messages within a single ciphertext should be possible using two different one-time pads. The authorities would have a hard time proving that the one-time pad that they made you hand over was the wrong one. The number of possible pads is vast and each pad can reproduce a message of equivalent length - although most messages will be garbage, all possible messages of the same length are equally valid.
     
    Last edited: Sep 7, 2019
  17. YellowSubmarine

    YellowSubmarine Rear Admiral Rear Admiral

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    One-time pads would be a little bit of a cheat here, so I'm not sure the authorities would buy it. You can claim anything encodes with a one-time pad to anything. For example, you'd get funny (and obviously fake) results if you tried to decode the quoted part of your message with the following one-time pad:
    Code:
    CxUSewAkFgZETTcGABIOBB0AFgoABxsdABVPUxoaBgsAABcBFUgoHRsLWBhBHQwGGwtETwxFbREd
    BxoIDEwWTxwfSQ8JRFQcBkwIDAJGBB4JTk0AGwYADQMAGQtFAxIBAA==
    
    Here it goes:
    Code:
    >>> import binascii
    >>> ciphertext = 'ETA: Two messages within a single ciphertext should be possible using two different one-time pads'
    >>> onetime_pad = '''
    ... CxUSewAkFgZETTcGABIOBB0AFgoABxsdABVPUxoaBgsAABcBFUgoHRsLWBhBHQwGGwtETwxFbREd
    ... BxoIDEwWTxwfSQ8JRFQcBkwIDAJGBB4JTk0AGwYADQMAGQtFAxIBAA==
    ... '''
    >>> key = binascii.a2b_base64(onetime_pad)
    >>> cleartext = bytes(map(operator.xor, ciphertext.encode('utf8'), key)).decode('utf8')
    >>> print (cleartext)
    NASA paid Russian actors to stage the Moon landing on Martian soil and killed all 9 the witnesses
    
    
     
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  18. Asbo Zaprudder

    Asbo Zaprudder Vice Admiral Admiral

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    Already been done - it's called quantum key distribution. It can be used to set up one-time pads at the two ends of a channel for completely secure communication, which cannot be eavesdropped or spoofed. Companies exist that sell such solutions.
     
    Last edited: Sep 12, 2019
  19. publiusr

    publiusr Vice Admiral Admiral

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