"On This Day" In Engineering History

Tune in to find out about significant engineering events that took place "on this day".

April 11, 1976 – The First Apple Computer is Released

Posted April 11, 2019 12:00 AM by RSBenner
Pathfinder Tags: Apple I computer jobs Wozniak

It is hard to imagine life without personal computers. I am old enough to remember when computers did not decorate the top of every office desk. Now they are everywhere – even in our pockets! But how did the computer business get to where it is now? Helping to ignite the industry were two members of a computer hobbyist group who came up with an idea, called the Apple Computer.

Steve Wozniak had a goal. He wanted to show the members of his group, the Homebrew Computer Club, that they could build their own, affordable computer. When his design was ready, he handed out schematics of his board to club members and taught them how to assemble their own units. Recognizing the substantial interest generated by this, fellow club member Steve Jobs convinced Wozniak that they should build and sell the computers, rather than giving the design away. This computer, the Apple I, was released for sale on April 11, 1976.

The Apple I was a single board computer with built-in circuitry for a video monitor and a keyboard. It featured an 8-bit MOS 6502, 1 MHz microprocessor and 40x24-pixel graphics. The 4KB standard memory could be expanded up to 8KB (or 48KB if expansion cards were added). Consumers had to add their own keyboard and monitor, although a regular television set could be used. Additional components such as power supply transformers, a power switch and a case would also need to be provided by the purchaser. Shortly after its initial release, an optional board was offered which provided a cassette interface for storage. The system could be used for programming, games or for running the BASIC operating system.

The Apple I was initially sold for $666.66, equivalent to a little over $3000 in today’s dollars. Over its lifetime, around 200 units were made and was discontinued in September of 1977. Sixty-six are still in existence today and if you have one, celebrate; in October of 2014, an Apple I was sold for $905,000.






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January 15, 1919 – The Day Boston Drowned in Molasses

Posted January 15, 2019 12:00 AM by RSBenner
Pathfinder Tags: Boston flood molasses

When I think of molasses, I think of the brown, thick, sticky, syrupy stuff my mother stored in her refrigerator. My father would wait, for what seemed like forever, for it to slowly pour out of the jar onto whatever it was he was eating. Who knew that, exactly 100 years ago, the same substance formed a 15-foot high wall and destroyed a neighborhood in the North End of Boston, Massachusetts?

In the early twentieth century, fermented molasses was commonly used to produce industrial alcohol for use in the manufacturing of munitions and other weaponry. In 1915, the Purity Distilling Company, trying to capitalize on the rising sale of industrial alcohol due to World War I, constructed a huge, 50-foot high, 90-foot diameter steel holding tank (capacity of 2.5 million gallons) in the North End of Boston. They planned to use the tank to store shipments of molasses received from the Caribbean before being processed. However, in their haste, the tank was constructed haphazardly.

January 15, 1919 was an unusually warm day in Boston, heating up to over 40 degrees F by mid-day – and it was then that the molasses tank exploded. The tank, recently filled, unleashed a 15-foot high wave of molasses that traveled through the neighborhood at 35 miles per hour. Buildings were destroyed or totally picked up and moved from their foundations. A support girder from an elevated train track was snapped in half. Twenty-one people, unable to flee from the oncoming rush, were drowned, or otherwise fatally hurt, because of the flood; 150 people were injured.

Rescue and cleanup operations after the flood were extremely difficult. First responders struggled through the viscous molasses to help the victims – and the situation worsened as the molasses hardened quickly in the winter air. After the victims were recovered, the cleanup of more than 2 million gallons of molasses was a daunting task. And this task was aggravated by the rescuers and clean-up crews who, after leaving the scene, tracked molasses onto train platforms and seats, payphone handsets and elsewhere around the city as they made their way home. All in all, an estimated 80,000 man hours were spent cleaning up the molasses. For several weeks after the clean-up was completed, the smell of molasses was still in the air. The waters of Boston Harbor were stained brown until summer.

Initially, the company blamed anarchists for blowing up the tank to prevent munition manufacture. Then it was suggested that the warmer than average ambient temperature caused fermentation of the molasses, thus producing carbon dioxide and increasing the internal pressure in the tank which led to the explosion. Although this latter explanation may have contributed to the failure of the tank, it was not the cause; the cause was determined to be the poor design and construction of the tank. Investigators determined that the company constructed the tank without proper design, inspections or safety tests, and that the man they hired to oversee the project was not an engineer nor could he even read a blueprint. They discovered that the tank leaked since its installation and that the company’s solution was to paint the tank brown so that the leaks would be less noticeable. Hence, the company was to blame.

This tragedy helped Massachusetts, and many other states, to develop and enact laws requiring the inspection and approval of plans prior to the beginning of major construction projects.

It is interesting to note a couple of recent studies about the Great Molasses Flood and their findings. In 2014, Ronald Mayville, a senior structural and metallurgical engineer with Simpson, Gumpertz & Heger in Waltham, MA, determined that the steel walls used to construct the tank were half the thickness they should have been in order to withstand the enormous stress applied by 2.5 million gallons of molasses. He also stated that, although manufactured to the standards of the time, the type of steel used did not contain enough manganese which made it brittle. In 2016, Harvard professor Shmuel Rubinstein and some of his Fluid Dynamics students determined that one of the reasons the spill was so deadly was because it occurred during the winter. They discovered that the molasses had just been delivered two days prior to the collapse and that, following what was common practice during that time, the cargo was heated a few degrees to make it less viscous and easier to unload. Therefore, the molasses in the tank was warmer than the surrounding air allowing for the size and quick movement of the wave when the tank initially burst. The cold winter air, however, cooled the molasses quickly, raising the viscosity, and turning it into a deadly weapon. If the tank had burst in the summer, the molasses would have traveled further but been thinner, due to the higher temperature and lower viscosity, and although it would still have created a mess, it probably would not have caused as much death or damage.



Harvard Study:


Structural study:


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December 28, 1973 - The Skylab 4 "Mutiny"

Posted December 28, 2018 12:49 PM by Hannes

Forty-five years ago on December 28, 1973, the three-man crew of the Skylab 4 space station made history by effectively taking an unscheduled day off. Gerald Carr, Edward Gibson and William Pogue switched off radio communications with NASA, refused communications from mission control and spent time relaxing and admiring Earth.

The Skylab controversy was triggered by a number of factors. Skylab 4’s 84-day mission was the longest yet undertaken by American astronauts, and the three crewmembers had never spent any time in space. Skylab 3’s crew had finished their assigned work on their 60-day spaceflight and asked NASA for more work, possibly leading the organization to have elevated expectations for the Skylab 4 crew. Skylab 4’s crew had gradually fallen behind on work for the first six weeks of the mission, and had become stressed trying to catch up.

Skylab 4 crew inside the space station. Source: NASA

Pogue’s New York Times obituary quoted him as writing: “We had been overscheduled. We were just hustling the whole day. The work could be tiresome and tedious, though the view was spectacular.”

Skylab 4’s mission continued without incident following the “strike,” and NASA worked carefully with the astronauts to reduce their workloads and control stress. Despite only lasting one day, the outage was an expensive one: estimates value a single day’s work on any Skylab mission at around $6 million per crewmember in 2017 dollars.

Skylab 4’s long duration and rookie crew were uncharted territory for NASA, and the organization learned important lessons about the psychological effects of long-term spaceflights. An astronaut lacks the freedom to act as he or she wants, and spur-of-the-moment thinking generally vanishes while in space. Astronauts often become frustrated by communication delays with mission control. Sunrises and sunsets every 45 minutes can interfere with sleep-wake cycles, quickly causing fatigue. Yet among astronaut testimonials, most relate that the biggest stressors are social and cultural deprivation as well as boredom during downtime.

Skylab’s teaching moments resonated throughout the subsequent history of American space programs. NASA implemented longer training protocols and more careful astronaut selection in subsequent space station programs. Psychological compatibility of crewmembers also became a greater concern.

Astronaut psychology is still a prime concern as NASA eyes spaceflights to Mars. For the past five years, the organization has studied crewmembers stress management, morale and problem-solving at Hawaii Space Exploration Analog and Simulation (HI-SEAS), an analog habitat meant to replicate the Martian surface. Most HI-SEAS missions last around 8 months, significantly shorter than a two- to three-year expeditionary mission to Mars, which could be possible as early as 2021.

The Skylab 4 “mutiny” and the subsequent Shuttle-Mir missions of the 1990s provoked necessary organizational changes at NASA, focused less on individual crewmembers and more on crew dynamics and their isolation from family and friends for long periods.

10 comments; last comment on 01/10/2019
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November 7, 1940 – The Collapse of “Galloping Gertie”

Posted November 05, 2018 12:00 AM by RSBenner

If you have ever taken a physics course, whether in high school or college, there is a very good chance that you heard about the collapse of the Tacoma Narrow Bridge. In fact, if you are an engineering student, you probably have learned more about this bridge than the average student. Why? Because not only did this bridge collapse due to flaws in the design and construction, it collapsed in an amazingly dramatic fashion and was captured on film. This film, commonly shown as part of many physics or engineering curricula, leaves a lasting impression in the student’s memory.

Construction of the Tacoma Narrows Bridge began in September of 1938. It was a suspension bridge built over Puget Sound between the city of Tacoma and the Kitsap Peninsula in Washington State. At the time of construction, it was the third-longest suspension bridge in the world, by main span length. However, as soon as the deck of the bridge was built, the workers realized that something was not right. The deck of the bridge would move vertically during windy conditions – so much so, it was given the nickname “Galloping Gertie.” Some of the workman were even forced to chew on lemons to lessen the feeling of seasickness they experienced while working on the bridge.

Although the state’s engineers assured the local papers that the ‘bounce’ was normal, they began taking steps to eliminate the movement. They contracted for a wind tunnel study of the bridge to be performed to find the cause and a permanent solution. In addition, four hydraulic jacks were installed at the towers to act as shock absorbers. Although this modification was not very effective, the bridge was opened to traffic on July 1, 1940.

In October of 1940, as a preliminary suggestion from the wind tunnel study, tie down cables (1-9/16” diameter anchored restraining wires) were installed along the bridge’s side and mid-spans. This seemed to reduce the ‘bounce’ of the side spans, but was not effective at reducing the movement of the center span. The increased winds of autumn were now taking their toll on Gertie.

During the morning of November 7, 1940, a strong, icy wind was lashing at the bridge, causing two- to five-foot-high movements of the mid-span. This was followed later by a “lateral twisting motion” which was tilting the roadside up 28 feet one side, then the other, at an angle of up to 45 degrees. Approximately one hour after this twisting motion began, the Tacoma Narrows Bridge failed, and the center span of Galloping Gertie fell into Puget Sound.

The Tacoma Narrow Bridge was a suspension bridge and, as such, was designed to move. But why did this bridge move so much and, therefore, ultimately fail? As described in many physics and engineering books, the cause of the collapse is attributed to forced resonance: aeroelastic flutter produced by the wind that matched the natural frequency of the bridge. Several factors contributed to this. The wind tunnel study, completed just days before the collapse, determined that the solid stiffening girders, used underneath the roadbed, were partly to blame. Typically, bridges employed an open lattice beam truss, allowing the wind to pass through. However, this solid girder design caused the wind to be diverted above and below the structure, therefore, attributing to the flutter. Other factors identified throughout the investigation were the narrow deck design (only two lanes) and the overall lightness of the bridge partly due to the cost saving measures of limiting the amount of steel used during construction.

Although a tragedy financially, there was no loss of life from the collapse (except for a cocker spaniel, Tubby). And, as a direct result, research into aerodynamics-aeroelastics expanded, which helped influence future bridge designs preventing this from occurring again.

However, Galloping Gertie still lives on in physics and engineering classrooms and students’ memories.




Video showing the collapse:


15 comments; last comment on 12/29/2018
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September 30, 1954 - Commissioning of the First Nuclear Submarine

Posted September 30, 2018 12:00 AM by RSBenner
Pathfinder Tags: Nautilus nuclear submarine

The birth of the United States Submarine Force is considered to be April 11, 1900, the day the US Navy purchased the Holland VI Submersible (renamed the USS Holland, SS-1) from John Philip Holland's Holland Torpedo Boat Company. Since then, submarines have been an important component of the US Naval force. In fact, during World War II, US submarines sank over 30 percent of Japanese naval ships, including eight aircraft carriers, despite being only 2 percent of the Navy. Although effective, there were drawbacks to their design. Submarines used during World War II were diesel-electric; powered by diesel engines while traveling on the surface of the water and by battery operated electric motors while submerged. As a result, these submarines traveled much slower while submerged compared to their surface speed. Additionally, the boats could only remain submerged up to 48 hours before surfacing and recharging their batteries via their air-breathing diesel engines. These facts hindered attempts to hide or escape from enemy ships. New designs had to be developed.

On December 31, 1947, the task to design a nuclear power plant for a submarine was given to Bettis Atomic Power Laboratory. This design would solve the issues that plagued the diesel-electric submarines since nuclear power produces zero emissions and consumes no air. Overseen in every detail by Admiral Hyman G. Rickover, “Father of the Nuclear Navy,” the result was a pressurized water reactor, the S2W, which would be the basis for future US nuclear-powered submarines. The keel of the ship to house this power plant was laid on June 14, 1952 at General Dynamic, Electric Boat Division. Designated the USS Nautilus (SSN-571) after Captain Nemo's submarine in Jules Verne's novel Twenty Thousand Leagues Under the Sea, she was christened and launched on January 21, 1954 by First Lady Mamie Eisenhower. The USS Nautilus (SSN-571) was commissioned as the first nuclear submarine on September 30, 1954.

It is interesting to note that today, after a newly built ship is christened and launched, the sea trial phase of the boat’s development begins. During sea trials, the ship’s systems are tested “at sea” and any problems resolved. Once completed, the ship is deemed ready for service and commissioned into the US Navy. However, in the case of the Nautilus, she remained docked after commissioning for more construction and testing. She was finally sent to sea on January 17, 1955 with the transmission of the historic message by the first Commanding Officer, Commander Eugene P. Wilkinson, “Underway on nuclear power.” Extensive system testing continued until May 11, 1956, almost two years after commissioning, when the USS Nautilus was accepted for unrestricted service by the US Navy.

The USS Nautilus was a great success and began setting new records almost immediately. During her first shakedown cruise from New London to San Juan, Puerto Rico, she traveled 1,381 miles in less than 90 hours. She set speed and distance records during this trip and also achieved a record for the longest period of complete submergence. The Nautilus broke her own record in May of 1957, by cruising completely submerged from the Panama Canal to San Diego, a distance of 3,049 miles. On August 3, 1958, she became the first ship to travel to the North Pole, sailing 96 hours and 1,830 miles under the ice from the Barrow Sea to the Greenland Sea. She again broke her own record on August 18, 1958 when she traveled from Portland, England to New York City, traveling over 3,100 miles submerged in six days, 11 hours and 55 minutes, at an average speed of more than 20 knots.

After a distinguished career spanning 25 years, the USS Nautilus was decommissioned on March 3, 1980. She was designated a National Historic Landmark in 1982 and, after extensive work, was returned to her birthplace, Groton CT, in 1985. On April 11, 1986, on the eighty-sixth birthday of the Submarine Force, the Historic Ship Nautilus opened to the public as part of the Submarine Force Museum. It is a wonderful museum and I highly recommend a visit. You can read about CR4’s visit to the museum here: https://cr4.globalspec.com/blogentry/10112/The-Submarine-Force-Museum-The-USS-Nautilus-Part-1

The USS Nautilus was an amazing piece of engineering. Being the first nuclear submarine, she was a critical test platform for the newly designed power plant and its systems, helping to shape future submarine design and technology. She ushered in a new era of submarines and the US Navy would never be the same.




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