Recently in CONTINUITY

Friday, September 17, 2021

KIC 8462852 (Boyajian's Star) Continues to Mystify

I'm not saying it's aliens…but what the heck is going on? The continued and possibly periodic dimming episodes and secular decline in brightness of of KIC 8462852, an otherwise unremarkable F-type main-sequence star located around 1470 light years from the Sun in the constellation of Cygnus, continues to bat away every proposed natural theory of origin. Might we be watching stellar lifting in progress?

Posted at 11:08 Permalink

Wednesday, September 15, 2021

The UAC TurboTrain—America's Failed Attempt at High-Speed Rail

I do not use “America” as a sloppy synonym for the United States: the trains were manufactured and used both in Canada and the U.S. Here is more on the UAC TurboTrain.

Posted at 11:36 Permalink

Tuesday, September 14, 2021

Nike-Hercules—When U.S. Cities were Ringed with Nuclear-Tipped Missiles

When I was a kid, my parents took me on a week-end tour of a local Nike-Ajax site, probably in 1958 or 1959. They showed you everything, except inside the circular berm where they did hazardous propellant maintenance operations. (Nike-Ajax used toxic hypergolic liquid propellants in its second stage.) Afterward, the site was converted to the nuclear-tipped Nike-Hercules, and no tours were offered.

At the peak, there were 265 Nike-Ajax sites in the U.S. The longer range Nike-Hercules covered a larger area, and was deployed in only 130 locations, with the excess Nike-Ajax sites decommissioned.

Posted at 12:49 Permalink

Vacuum Tube Computer Part 17: Arithmetic/Logic Unit

Finally, all of the previously design, built, and tested pieces of the computer begin to come together at its heart: the unit which performs the arithmetic or logic operation designated by an instruction. This is simpler than you might imagine, as it consists mostly of selecting a result among multiple logic inputs that compute the results of the various functions, all of which have been previously constructed.

Posted at 11:32 Permalink

On the Road with Tesla “Full Self Driving” Beta 10

Here is another report, driving in San Francisco and deliberately putting the car into difficult situations.

Two things amaze me about this deployment of “full self driving” on the litigious streets of Safetyland. First, that paying customers are so forgiving of a product which, after ten releases, still does not remotely do what it is claimed to—drive autonomously without a vigilant human driver ready to take over an in instant when it “disengages” or is about to turn into oncoming traffic. Second, that Tesla, a public company with PricewaterhouseCoopers as its auditors, is not required to qualify its financial statements with risk factors due to liability from mass deployment of a flawed product with such potential risk to life, limb, and third-party property damage, and that its directors seem fine with the situation. (Here are the declared risk factors from Tesla's most recent Form 10-K filing with the U.S. Securities and Exchange Commission.)

Posted at 11:00 Permalink

Monday, September 13, 2021

“SX-70” by Charles and Ray Eames

In 1972, instant photography reached an apogee with the Polaroid SX-70, a camera which was simultaneously foldable, single-lens reflex, automatic exposure, and instant, with the pictures developing outside the camera in broad daylight and requiring no messy coating or throw-away parts. Film was sold in cartridges of ten pictures, each of which included a disposable battery that powered the electronics and motorised machinery of the camera. Focus was manual on the original model; later models added ultrasonic sonar automatic focusing.

This film was produced for Polaroid by the Eames Office and shown at the shareholders' meeting when the camera was introduced and later used by the sales organisation.

Posted at 11:53 Permalink

Sunday, September 12, 2021

Jet-Powered Parasitic Fighter: McDonnell XF-85 Goblin

Here is more about the XF-85 Goblin. The task of re-attaching to a trapeze lowered by a bomber in the turbulent environment of its slipstream proved too demanding for even the very best test pilots. By the time the difficulty became apparent, progress in in-flight refuelling had rendered the concept of parasitic aircraft carried by larger planes obsolete.

Posted at 12:41 Permalink

Saturday, September 11, 2021

Railroad Car Ferry

Posted at 13:39 Permalink

Friday, September 10, 2021

Selenium Rectifiers—When They Blow Up, It’s Like a Rectal Fire

You'll find these in all kinds of electrical and electronic gear dating from the 1930s through the 1960s. They were the first (kind of) practical solid state rectifier, but had limited reverse voltage capability and required a stack of individual junctions for mains and higher voltage applications. They had a forward voltage drop of around one volt, which would increase as the unit aged. In high voltage and current applications, this could eventually lead to thermal runaway as heat dissipation and resistance increased, ending with a bang and release of hideously malodorous and toxic smoke. At least, when this happened, there was no question about what was wrong.

Posted at 14:11 Permalink

Interstellar Visitors in the Oort Cloud

Objects in the Oort cloud orbit the Sun very slowly: some less than 150 metres per second. This means it takes very little delta-v to cancel enough velocity to cause them to plunge into the inner solar system, where we observe them as comets. Interstellar comets, however, pass through the Oort cloud with velocities typical among nearby stars of tens of kilometres per second and continue unperturbed along their paths. This may have the consequence that in the outer Oort cloud interstellar comets outnumber those gravitationally bound to the Sun by a substantial margin.

Posted at 13:28 Permalink

Thursday, September 9, 2021

Hewlett-Packard 150A Oscilloscope Restoration: Part 3

With basic functionality restored, the focus turns to the inoperable second channel, a mystery thermistor, dodgy tubes, leaky capacitors, calibration, and the eternal confusion of RMS and peak-to-peak AC voltages. The behaviour of vacuum tube direct coupled and balanced amplifiers can be subtle, and even the slightest change can be puzzling.

Posted at 11:14 Permalink

Wednesday, September 8, 2021

Gun Launch to Earth Orbit

The 1991 paper, “A revolution in access to space through spinoffs of SDI technology” is, thirty years later, behind an IEEE paywall because, of course, it's only fair that the taxpayers who paid for this research should have to fork over US$33 to a private organisation in order to read it. Fortunately, Sci-Hub rides to the rescue with the full text.

Posted at 11:10 Permalink

Tuesday, September 7, 2021

The Curious Behaviour of Bullets in First-Person Shooter Games

One of the reasons many games use the “hitscan” model, where bullet flight is instantaneous, is that it is very easy to implement and fast to evaluate using “ray casting” from the player's viewpoint in the direction of look (and aim, which is the same). You just project a vector along that direction and look for the first intersection with an object in the scene, and there's your point of impact. Then you just render the shot along that vector with suitable sound and light effects. Modelling the flight of a projectile with physics is a lot more difficult, and requires taking into account motion of objects in the scene while the projectile is in flight.

If you think this is weird, there's been a flaw in Second Life since early 2020 where, in some regions of the grid, when you shoot a projectile, it may just hang in the air in front of the launcher for two long seconds, then take off in the direction of the target. I wasted a huge amount of time in development of my Anvil Tosser trying to work around this and finally concluded it can only be remedied by fixing the fundamental problem in the simulator. Here is some of my research into this problem, and some more.

Posted at 11:56 Permalink

Monday, September 6, 2021

The Relaxed Wife—“Who Needs Tranquillity? I'm Hopped Up on Goofballs!”

From 1957, Pfizer promotes “ataraxic medicine”.

It makes those who fear they're about to quit feel like they're ready to begin, bidding their darkened spirits goodbye, for the calming peace of a cloudless sky. [8:20]

What could possibly go wrong?

Posted at 13:05 Permalink

A History of Bitcoin Transaction Dust and Spam Storms

Posted at 12:45 Permalink

Sunday, September 5, 2021

Colour-Motion Optical Illusion

Posted at 12:21 Permalink

Saturday, September 4, 2021

Tour of the International Space Station's New Nauka Module

The tour is guided by European Space Agency astronaut Thomas Pesquet. The audio is in French, with English subtitles. The module, called Наука (Nauka), which means “Science” in Russian, is also known as the Multipurpose Laboratory Module (MLM) and is docked to the nadir (Earth-facing) port of the Russian segment of the space station.

Posted at 11:53 Permalink

Friday, September 3, 2021

“The Big Switch”—IBM Computer Message Switching in 1963

Posted at 12:54 Permalink

Thursday, September 2, 2021

Apollo Command Module: Excellent Spacecraft—Terrible Boat

Posted at 12:11 Permalink

Wednesday, September 1, 2021

HP 9825 Repair Part 11—Debugging the Keyboard, Display, and Printer Board

The repairs of earlier episodes got the Hewlett-Packard 9825 laboratory computer working, but only with a keyboard, display, and printer module borrowed from a working 9825. Now the focus moves on to repairing the module from the unit fried when its power supply blew up. This is a worrisome task, since this module's circuit board includes a custom Hewlett-Packard application-specific integrated circuit (ASIC) which, all these years later, might as well be made of gold-pressed unobtainium.

Posted at 15:15 Permalink