FERMIAC: The Computer that Advanced Beyond the Manhattan Project

One of the keys to nuclear fission is sustaining a chain reaction. A slow chain reaction can provide clean power for a city, and a fast one can be used to create a weapon that will obliterate a city. These days, kids can learn about Uranium and Plutonium in high school. But just a few generations ago, the idea of splitting the atom was just a lofty goal for the brightest physicists and mathematicians who gathered at Los Alamos National Laboratory under the Manhattan Project.

Decoding the mysteries of nuclear fission required a great deal of experimentation and calculations. One bright physicist in particular made great strides on both fronts. That man was [Enrico Fermi], one of the fathers of the atomic bomb. Perhaps his greatest contribution to moving the research beyond the Manhattan Project was creating a handheld analog computer to do the math for him. This computational marvel is known as the FERMIAC.

What is Fission?

Nuclear fission occurs when a nucleus is split into fragments, a process that unleashes a great deal of energy.  As a handful of neutrons travel through a reactor pile or other fissionable material, a couple of outcomes are possible. Any one neutron collision might result in fission. This means there will be some number of new neutrons whose paths must be tracked. If fission does not occur, the neutrons may simply scatter about upon collision, which changes their speed and trajectory. Some of the neutrons might be absorbed by the material, and others will simply escape it. All of these possibilities depend on the makeup of the material being bombarded and the speed of the neutron.

Fission Diagram by Michalsmid

Every event that happens to a neutron comprises its genealogical history. If this history is recorded and analyzed, a statistical picture starts to emerge that provides an accurate depiction of the fissility of a given material. [Fermi]’s computer facilitated the creation of such a picture by performing mathematical grunt work of testing different materials. It identified which materials were most likely to sustain a reaction.

Before he left Italy and the looming threat of fascism, [Fermi] led a group of young scientists in Rome called the Via Panisperna boys. This group, which included future Los Alamos physicist [Emilio Segrè], ran many experiments in neutron transport. Their research proved that slow neutrons are much better candidates for fission than fast neutrons.

During these experiments, [Fermi] ran through the periodic table, determined to artificially irradiate every element until he got lucky. He never published anything regarding his methods for calculating the outcomes of neutron collisions. But when he got to Los Alamos, [Fermi] found that [Stanislaw Ulam] had also concluded that the same type of repeated random sampling was the key to building an atomic weapon.

The Monte Carlo Method: Shall We Play a Game?

Monte Carlo method applied to approximating the value of π. by CaitlinJo

[Ulam], a Polish-born mathematician who came to the US in 1935, developed his opinion about random sampling due to an illness. While recuperating from encephalitis he played game after game of solitaire. One day, he wondered at the probability of winning any one hand as laid out and how best to calculate this probability. He believed that if he ran through enough games and kept track of the wins, the data would form a suitable and representative sample for modeling his chances of winning. Almost immediately, [Ulam] began to mentally apply this method to problems in physics, and proposed his ideas (PDF) to physicist and fellow mathematician [John von Neumann].

This top-secret method needed a code name. Another Los Alamos player, [Nick Metropolis] suggested ‘Monte Carlo’ in a nod to games of chance. He knew that [Ulam] had an uncle with a propensity for gambling who would often borrow money from relatives, saying that he just had to go to Monte Carlo. The game was on.

The Tricky Math of Fission

Determination of the elements most suitable for fission required a lot of calculations. Fission itself had already been achieved before the start of the Manhattan Project. But the goal at Los Alamos was a controlled, high-energy type of fission suitable for weaponization. The math of fission is complicated largely because of the sheer number of neutrons that must be tracked in order to determine the likelihood and speed of a chain reaction. There are so many variables involved that the task is monumental for a human mathematician.

Stanislaw-Ulam-FERMIAC
[Stanislaw Ulam] and FERMIAC.

After [Ulam] and [von Neumann] had verified the legitimacy of the Monte Carlo method with regard to the creation of nuclear weaponry, they decided that these types of calculations would be a great job for ENIAC — a very early general purpose computer. This was a more intensive task than the one it was made to do: compute artillery firing tables all day and night. One problem was that the huge, lumbering machine was scheduled to be moved from Philadelphia to the Ballistics Research Lab in Maryland, which meant a long period of downtime.

While the boys at Los Alamos waited for ENIAC to be operational again, [Enrico Fermi] developed the idea forego ENIAC and create a small device that could run Monte Carlo simulations instead. He enlisted his colleague [Percy King] to build the machine. Their creation was built from joint Army-Navy cast off components, and in a nod to that great computer he dubbed it FERMIAC.

FERMIAC: Hacking Probabilities

FERMIAC was created to alleviate the necessity of tedious calculations required by the study of neutron transport. This is something of an end-run around brute force. It’s made mostly of brass and resembles a trolley car. In order to use it, several adjustable drums are set using pseudorandom numbers. One of these numbers represents the material being traversed. A random choice is made between fast and slow neutrons. A second digit is chosen to represent the direction of neutron travel, and a third number indicates the distance traveled to the next collision.

FERMIAC in use
FERMIAC in action.

Once these settings are dialed in, the device is physically driven across a 2-D scale drawing of the nuclear reactor or materials being tested. As it goes along, it plots the paths of neutrons through various materials by marking a line on the drawing. Whenever a material boundary is crossed, the appropriate drum is adjusted to represent a new pseudorandom digit.

FERMIAC was only used for about two years before it was completely supplanted by ENIAC. But it was an excellent stopgap that allowed the Manhattan Project to not only continue unabated, but with rapid progress. FERMIAC is currently on display at the Bradbury Science Museum in Los Alamos, New Mexico alongside replicas of Fat Man and Little Boy, the weapons it helped bring to fruition. [Fermi]’s legacy is cemented as one of the fathers of the atomic bomb. But creating FERMIAC cements his legacy as a hacker, too.

After Los Alamos, [Stanislaw Ulam] would continue to make history in the field of nuclear physics. [Enrico Fermi] was opposed to participating in the creation of the exponentially more powerful hydrogen bomb, but [Ulam] accepted the challenge. He proved that Manhattan Project leader [Edward Teller]’s original design was unfeasible. The two men worked together and by 1951 had designed the Teller-Ulam method. This design became the basis for modern thermonuclear weaponry.

Today, the Monte Carlo method is used across many fields to describe systems through randomness and statistics. Many applications for this type of statistical modeling present themselves in fields where probabilities are concerned, like finance, risk assessment, and modeling the universe. Wherever the calculation of all possibilities isn’t feasible, the Monte Carlo method can usually be found.

[Main Image Source: FERMIAC machine by Mark Pellegrini]

UPDATE: Commentor [lwatchdr] pointed out that the use of the FERMIAC began after the Manhattan Project had officially ended in 1946. Although many of the same people were involved, this analog computer wasn’t put into use until about a year later.

CubeSat Challenge Winners Show Interesting Design Approaches

The winners are in for the GrabCad CubeSat Challenge, which asked designers to rethink the way that CubeSats are built. These tiny 10 cm square satellites are the hot thing in orbit, and the competition was looking for new ways to build and pack more into this tiny space. The winners offered some fascinating new approaches to building CubeSats, and some excellent design lessons that anyone can use.

The winner was FoldSat, by [Paolo Minetola]. His excellent design is a 3D printed folding case for a satellite that is built from just two 3D printed parts. The case can be snapped together and offers multiple ways to mount electronic components and sensors inside. [Paolo] estimates that it could save 40% time and 30% materials from existing CubeSat casings, which means more space inside and more time to build. It is an excellent example of how 3D printing can make things cheaper, easier and better, all at the same time.

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Arduino Powered Rubber Band Sentry Turret Is Not a Lie

You know that guy in the next cube is sneaking in when you are away and swiping packs of astronaut ice cream out of your desk. Thanks to [Kevin Thomas], if you have an Arduino and a 3D printer, you can build a rubber band sentry gun to protect your geeky comestibles. You’ll also need some metric hardware, an Arduino Uno, and a handful of servo motors.

The video shows [Kevin] manually aiming the gun, but the software can operate the gun autonomously, if you add some sensors to the hardware.  The build details are a bit sparse, but there is a bill of material and that, combined with the 3D printing files and the videos, should allow you to figure it out.

We couldn’t help but wish for a first person view (FPV) camera and control via a cell phone, so you could snipe at those ice cream thieves while hiding in the broom closet. On the other hand, if you got the gun working, adding the remote wouldn’t be hard at all. You probably have a WiFi FPV camera on your quadcopter that finally came out of that tree and there’s lots of ways to do the controls via Bluetooth or WiFi.

Not that you don’t have options. But here at Hackaday HQ, we have lots of rubber bands and not so many green pigs. If you’d rather shoot paintballs, be careful you don’t accidentally repaint the insides of your cube.

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Custom Machined Triple Threat Slingshot

Time was when a lad in need of a ranged weapon would hack a slingshot together out of a forked tree branch and a strip of inner tube. Slingshot design has progressed considerably since [Dennis the Menace]’s day, but few commercially available slingshots can match up to the beauty and functionality of this magnificently machined multipurpose handheld weapon system.

Making it clear in his very detailed build log that this is but a prototype for a design he’s working on, [Gord] has spared little effort to come up with a unique form factor that’s not only functional as a slingshot, but also provides a few surprises: a magazine that holds nine rounds of ammo with magnets; knuckle protection on the hand grip that would deal a devastating left hook; and an interchangeable base that provides a hang loop or allows mounting a viciously sharp broadhead hunting arrow tip for somewhat mysterious purposes. There’s plenty to admire in the build process as well – lots and lots of 6061 billet aluminum chips from milling machine and lathe alike. All told, a nice piece of craftsmanship.

For a more traditional slingshot design with a twist, check out this USB-equipped slingshot that talks to Angry Birds. And when your taste in slingshots run more toward the ridiculously lethal, [Jörg Sprave]’s machete launcher never disappoints.

[Thanks Leslie!]

Engineers Create Super-Hard Whack-a-Mole

Is your latest project driving you mad? Are you subject to occasional fits of rage? This project might help: for a class called elecanisms at Olin College, [Forrest] and a team of three other students made a whack-a-mole arcade game that lets you vent your rage on a helpless furry animal by whacking it with a large hammer. He built most of it from scratch, creating his own solenoid driver and LED sensor board. However, there is a twist in here that gives the moles a fighting chance: there is an accelerometer built into the hammer that lets them know that your heavy hammer of doom is approaching.

Will they escape before your righteous wrath descends upon them? That depends on how you decide to set it up, and how merciful you want to be. The build even includes a coin-operated pay-to-play slot. They kept the cost low at a penny, but this is just begging to be installed at the local pub to rake in those quarters.

This course has been the source of a few projects that we have featured before on Hackaday, including the Confectionary Canon, which tracks your face and fires marshmallows right into your gaping maw.

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Artificial Killing Machine

L.A. artist [Jonathan Fletcher Moore] sent us this fantastic tech-art piece on dehumanization and drone warfare. Talking too much about art is best left to the artists, so we’ll shut up and let you watch the video below the break.

artificial_killing_machine_0011_800The piece is essentially a bunch of old cap guns with servos that pull their triggers. A Raspberry Pi with an Internet connection fetches data on US drone strikes from www.dronestre.am and fires off a cap every time someone is killed. At the same time, the story version of the data is printed out in thermal paper that cascades onto the floor.

Viewers are encouraged to sit underneath all the cap guns and wait. Talk about creepy and suspenseful. And a tiny reflection of the everyday fears that people who live under drone-filled skies.

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Billy Club Texts Your Mother if you Hit Someone

Mama, just killed hit a man, Put a gun against his head, Pulled my trigger, now he’s dead.
Mama, life had just begun, But now I’ve gone and thrown it all away…

This latest piece of half-art / half-prototype from one of our favorite hacker-artists [vtol] is a billy club equipped with a GSM-module. It automatically sends an SMS to your mother with the text: “Mom, I hit a man.” He calls it the Antenna:

The idea of the project is to create a device which strictly controls the cruelty of police. As all the standard methods of control are ineffective, this project suggests the maternity as the last stronghold of human kindness and responsibility.

An Arduino is equipped with a piezo sensor to detect impact, and a GSM shield takes care of the texting. It’s an interesting concept, similar to requiring police officers to wear body cameras. You can debate the practicality, but we’re always interested in hearing about weapons monitoring tech concepts. One of our favorites has always been the DNA gun from (Judge) Dredd. Did you know there was an Internet Movie Firearms Database? But we digress, check out [vtol’s] demo video:

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