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December 10, 2020 Archives
Thursday, December 10, 2020
CONTINUITY: 1950s Teleregister Numerical Displays
In the 1950s big city stockbrokers' offices had large boards that showed near-real-time quotes of the most traded stocks. These boards had hundreds of these Teleregister electromechanical displays, which could be set by simple pulses of DC current and required no power unless they were changing. By 1964, these quote boards were installed in around 650 brokerage offices in the U.S. A few years later, they had all been replaced by quote machines.
Posted at
19:36
THE HAPPENING WORLD: Delta IV Heavy / NROL-44: Will the Hangar Queen Finally Fly?
United Launch Alliance is set to try again to launch a Delta 4-Heavy rocket and a classified US government spy satellite from Florida Thursday after delays of more than three months due to persistent issues with the mission’s launch pad.
— Spaceflight Now (@SpaceflightNow) December 10, 2020
📷: @ulalaunchhttps://t.co/Yl3GrXUYYs pic.twitter.com/vkWRhZJIv1
ULA have been trying to launch this rocket since August 26th. Today's attempt will be its sixth announced launch date, with two prior countdowns halting shortly before liftoff. The scheduled launch time is 23:15 UTC on 2020-12-10, with weather predicted as 90% favourable for the attempt.
Posted at
12:54
TRACKING WITH CLOSEUPS: SpaceX’s Biggest Starship Flight Is a Spectacular Success Even after Crash Landing
Here is Scott Manley's analysis of the SpaceX Starship SN8 flight test. Scott believes that the two Raptor engine shutdowns during ascent were intended, as part of a thrust reducing programme to slow and halt the ascent near the intended altitude and hover during the horizontal translation toward the landing site. Based on the most recent information I can find, the Raptor cannot be throttled below 40% of full thrust, so shutting down engines as the vehicle loses mass due to propellant consumption may be necessary. Further, maintaining engine power is the only way for the vehicle to remain stable during the ascent phase.
This analysis is reinforced by the observation that the two engines which that restarted to perform the flip maneuver and landing (which failed due to fuel starvation) were the ones shut down during ascent. If they had been shut down due to a detected failure, it's unlikely they would have restarted.
Posted at
12:27