John Walker

  • John Walker posted an update in the group Group logo of SCANALYZERSCANALYZER 4 hours, 38 minutes ago

    THE HAPPENING WORLD

    “Tesla Crash on Autopilot”

    Here is a full unroll of the thread.

  • John Walker posted an update in the group Group logo of SCANALYZERSCANALYZER 8 hours, 25 minutes ago

    TRACKING WITH CLOSEUPS

    “Photography of Nuclear Detonations”

    This is a collection of gorgeous films from the atmospheric testing era made by Edgerton, Germeshausen, and Grier, Inc. (EG&G), including many shot with the Rapatronic camera (shutter speed as short as 10 nanoseconds), and some showing the elusive “rope trick” and precursor wave from a low-altitude detonation.

    These are some of of the few movies of nuclear detonations which do not just go all white for a short time after the burst, but actually record the growth of the firebal…[Read more]

  • John Walker posted an update in the group Group logo of SCANALYZERSCANALYZER 9 hours, 30 minutes ago

    CONTINUITY

    “How a $2 Toothbrush Saved the ISS and Other Unbelievable Space Hacks”

  • John Walker posted an update in the group Group logo of SCANALYZERSCANALYZER 1 day, 3 hours ago

    THE HAPPENING WORLD

    “SpaceX Starship SN8 Nose Code Installed”

  • John Walker posted a new activity comment 1 day, 6 hours ago

    Mentioned in an official tweet from Second Life.

  • John Walker posted a new activity comment 1 day, 11 hours ago

    Scrubbed.

  • John Walker posted an update in the group Group logo of SCANALYZERSCANALYZER 1 day, 13 hours ago

    THE HAPPENING WORLD

    “SpaceX Starlink 15 Launch”

    Weather is still 50-50 for a launch today.

    • Scrubbed.

      3+
      avataravataravatar
  • John Walker posted an update in the group Group logo of SCANALYZERSCANALYZER 1 day, 15 hours ago

    TRACKING WITH CLOSEUPS

    “500V to 12V 3 Phase Power Supply”

    From China: an inexpensive and impressively reality-hardened™ power supply that takes 380 volt 3 phase input and regulates it to 12 volts DC. This supply has excellent isolation, common-mode suppression, spike filtering and overload fusing, thermal design, and conservative use of redundant components to run well below their ratings and provide fault tolerance. Amid a sea of Chinese junk, one finds an occasional gem.

    The reverse-engineering is a good short course on con…[Read more]

  • John Walker posted an update in the group Group logo of SCANALYZERSCANALYZER 1 day, 16 hours ago

    CONTEXT

    James Randi, 1928–2020, R.I.P”

  • John Walker posted an update in the group Group logo of SCANALYZERSCANALYZER 2 days, 5 hours ago

    TRACKING WITH CLOSEUPS

    “Collecting the Return Sample from Asteroid 101955 Bennu”

  • John Walker posted an update in the group Group logo of SCANALYZERSCANALYZER 2 days, 9 hours ago

    THE HAPPENING WORLD

    “Rocket Lab ‘In Focus’ Launch from New Zealand”

  • John Walker posted an update in the group Group logo of SCANALYZERSCANALYZER 2 days, 13 hours ago

    CONTEXT

    “Insane Engineering of the Saturn F-1 Engine”

    Before you call it a “big, dumb engine”, look at some of the engineering drawings of components here. I don’t recall hearing before about the injection of gaseous helium in the oxygen feed lines to damp pogo, pre-filling the thrust chamber with ethylene glycol, and burst capsules of hypergolics in the fuel feed lines to the injector plate. Clearly, if they’d had a cut-off after one or more engines had started, major servicing would have been required, possibly requiring a roll-ba…[Read more]

  • John Walker posted an update in the group Group logo of SCANALYZERSCANALYZER 2 days, 13 hours ago

    TRACKING WITH CLOSEUPS

    Here’s the “8”:

    u1 = 10^6400
    u2 = 10^6352
    t = u1 – u2 – 1
    9.9999999999999999999999999999999999999999999999__8__9999999999…999

    FactorInteger[t]
    {{9999999999999999999999999999999999999999999999989999999999999999999999999999999999999999999999999999999999999999999999999999999999999999…999, 1}}

    (Computations with Mathematica on my Raspberry Pi 3.)

  • John Walker posted a new activity comment 3 days, 4 hours ago

  • John Walker posted an update in the group Group logo of SCANALYZERSCANALYZER 3 days, 4 hours ago

    THE HAPPENING (TINY) WORLD

    “OSIRIS-REx Touches Down on Asteroid 101955 Bennu and Collects Sample”

  • John Walker posted a new activity comment 3 days, 11 hours ago

    Cloud Halo was featured in Inara Pey’s “Living in a Modem World” for 2020-10-20.

  • John Walker posted an update in the group Group logo of SCANALYZERSCANALYZER 3 days, 11 hours ago

    TRACKING WITH CLOSEUPS

    “Extremely High-Altitude Nuclear Detonation Effects – Systems Interference”

    I saw one of those barium release sounding rocket shots launched from Wallops Island in the 1960s. At the time, they said it was for “atmospheric research”—heh.

  • John Walker posted an update in the group Group logo of SCANALYZERSCANALYZER 3 days, 12 hours ago

    CONTEXT

    “Explosive Bat in Slow Motion”

    Finally! An exploding baseball bat.

  • John Walker posted an update in the group Group logo of SCANALYZERSCANALYZER 3 days, 15 hours ago

    THE HAPPENING WORLD

    “SpaceX SN8 Pre-Burn and Static Fire Test”

    Overnight, SpaceX conducted a pre-burner test followed later by a static firing of Starship prototype SN8, the first equipped with three Raptor engines and intended for the first high-altitude hop flight.

  • John Walker posted an update in the group Group logo of SCANALYZERSCANALYZER 5 days, 13 hours ago

    CONTINUITY

    “How Can Soyuz Reach the Space Station in Only 3 Hours?”

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