Falcon 9 Re-Supplies the ISS on CRS-14

Launch of CRS-14
Threatnigh thunderstorms, an image taken by a sound triggered camera at Space Launch Complex 40. Image from @marcuscotephoto on twitter.

On April 2nd, 2018 at 20:30 UTC a Falcon 9 took off from Launch complex 40 at Cape Canaveral AFB. Aboard was a refurbished Dragon capsule with CRS-14, a resupply for the ISS. This was the 14th of up to 20 CRS missions contracted with NASA, with new Crew Dragon variants soon to be used. The capsule safely reached the ISS and was docked 20 minutes earlier than planned. The cost of the mission was reported to be around $2 billion, and comes under a contract between NASA and SpaceX.

Reused Dragon Capsule on CRS-14
The CRS-14 just before launch, carrying a reused Dragon Capsule for CRS-14. Image from @marcuscotephoto on Twitter.

The Dragon capsule carried 2,630kg  of cargo to the International Space Station, including supplies and research equipment. it has 1070 kg of science equipment, 344 kg of supplies for the crew, 148 kg of vehicle hardware, 49 kg of advanced computer equipment and 99 kg of spacewalking gear. Aboard there are a number of experiments, such as a new satellite designed to test methods of removing space debris. There are also frozen sperm cell samples, a selection of polymers and other materials, all experiments to test what happens to different items when exposed to space and microgravity.

CRS-14 launch
Launch of F9-53 on April 2nd 2018, carrying CRS-14 using a reused rocket and capsule. Image from SpaceX Flickr.

Designated F9-53, the Falcon 9 used booster B1039.2, which previously boosted the CRS-12 mission in August 2017, where it returned to landing zone 1. As is customary, the first stage was left “sooty” from it’s first flight. It powered for 2 minutes and 41 seconds before falling back to earth. For the sixth time in the last 7 Falcon 9 launches, the first stage was purposefully expended, even though it carried landing legs and steering grid fins. As with other expenatures, the rocket went through the re-entry landing sequence, but just didn’t have anything to land on and ended up in the sea. It was the 11th flight of a previously flown Falcon 9 first stage, five of which have been purposefully expended during the second flight, only 3 first stages remain that can be reflown.

A Sooty Falcon 9
The Falcon 9 was left sooty after its first flight which has now become the norm. Image from @marcuscotephoto on twitter.

The second stage completed its burn at 9 minutes and 11 seconds after takeoff, to insert Dragon into a Low Earth Orbit inclined 51.6 degrees to the equator. The Dragon 10.2 is a refurbished spacecraft capsule that first flew during the CRS-8 mission in April 2016. CRS-14 was the third launch of a previously flown Dragon capsule. This was also the first time that both the Dragon capsule and the Falcon 9 were refurbished versions on the same rocket. The docking process was carried out for around 20 minutes, and at 10:40 UTC Kanai detached the lab’s robotic arm to hook the free-flying Dragon capsule. At around 12:00 UTC Houston and Canada took control of the robotic arm and maneuvered it to the Harmony capsule of the ISS. It will be unpacked in a very slow process over a number of months.

Falcon 9 CRS-14
A falcon 9 lifting off from Cape Canaveral AFB Launch Complex 40. Image from SpaceX Flickr.
CRS-14 vapour streams
You can see the vapour streams coming off the falcon 9 as it sends its cargo towards the ISS. Image from SpaceX Flickr.

To find similar photos, and to buy reasonably priced prints of some of the above visit www.marcuscotephotography.com

SpaceX Launches NEXT 10 Iridium Satellites For a Fifth Time

Iridium-5 Launch 4
The Falcon 9 F9-52 launching with the Iridium NEXT-5 satellites aboard. Image from SpaceX Flickr.

At 14:13 UTC on March 30th 2018, SpaceX launched a Falcon 9 from foggy Vandenberg Air Force Base. Although designated F9-52 this was the 51st Falcon 9 launch. Using a v1.2 variant booster, the rocket delivered 10 Iridium NEXT satellites into orbit. This was the fifth of eight planned Iridium NEXT missions.

Iridium-5 Launch 2
The Falcon 9 lifting off from Vandenberg AFB california. After the fog had lifted. Image from SpaceX Flickr.

 

From Vandenberg AFB Space Launch Complex 4 East, the first stage of the rocket lasted 2 minutes 34 seconds, separating a few seconds after. The second engine fired for 6 minutes 23 seconds. This part of the webcast was purposefully cut short due to a NOAA remote sensing licensing requirements. This is an issue with SpaceX not having the right licence to broadcast images from certain parts of space. This burn placed the rocket in a roughly 180 x 625 km parking orbit. The Thales Alenia Space satellite then deployed an hour after launch, after a second brief 11 second burn. This put the satellites into a 625km x 86.6 deg orbit.

Iridium-5 Long Exposure
A 53 second long exposure of Falcon 9 F9-52 launching from Vandenberg AFB. Image from SpaceX Flickr.

The rocket used another “Fairing 2.0”, which is slightly larger than usual, but equipped with recovery systems. These systems include thrusters, a guidance system, and a parafoil. The ship, named Mr Steven has a large net to capture the halves of the fairing. Again, the ship failed to catch one of the fairings, due to a parachute system issue. In a tweet by Elon Musk, it was reported that the GPS guided parafoil twisted so the fairing impacted the water at high speed. He also said that SpaceX are doing helicopter drop tests to fix the issue.

Iridium-5 launch 3
The Falcon 9 launching, with a view of the surrounding buildings and fuel tanks. Image from SpaceX Flickr.

Five of the six previously used Falcon 9 vehicles have been fully expended, this was the tenth flight of a previously-flown Falcon 9 first stage. Four of these ten have been purposely expended during their second flight. The first stage (B1041.2) was previously flown during the Iridium NEXT 3 launch on October 9th, 2017. It performed the 2 minute 34 second boost, and performed what SpaceX call a “simulated landing” into the ocean. SpaceX appear to be only launching a reused stages for one reflight, with the soon to launch “block 5” likely to be reused multiple times. Currently the company only have 4 first stages that might be flown, with one allocated for the upcoming CRS-14 dragon resupply mission.

Iridium-5 mission 1
The Falcon 9 F9-52 launching with the Iridium NEXT-5 satellites aboard. Image from SpaceX Flickr.

Explorer 1 and the Van Allen Story

On February 1st, 1958 at 03:48 UTC (January 31st at 22:48 EST), the first Juno booster launched Explorer 1 into Low Earth Orbit. It was the first satellite to be successfully launched by the United States, and the third ever, after Sputnik 1 and 2 in 1957. Launched from the Army Ballistic Missile Agency’s (ABMA) Cape Canaveral Missile Annex in Florida, now known as Launch Complex 26. The launch played a pivotal part in the discovery of the Van Allen Belt, Explorer 1 was the start of the Explorer series, a set of over 80 scientific satellites. Although sometimes looked over in the history of space, it guided the US space program to what it eventually became.

William Hayward Pickering, James Van Allen, and Wernher von Braun display a full-scale model of Explorer 1 at a crowded news conference in Washington, DC after confirmation the satellite was in orbit.

In 1954 The US Navy and US Army had a joint project known as Project Orbiter, aiming to get a satellite into orbit during 1957. It was going to be launched on a Redstone missile, but the Eisenhower administration rejected the idea in 1955 in favour of the Navy’s project Vanguard. Vanguard was an attempt to use a more civilian styled booster, rather than repurposed missiles. It failed fairly spectacularly in 1957 when the Vanguard TV3 exploded on the launchpad on live TV, less than a month after the launch of Sputnik 2. This deepened American public dismay at the space race. This lead to the army getting a shot at being the first american object in space.

The launch
Launch of Jupiter-C/Explorer 1 at Cape Canaveral, Florida on January 31, 1958.

In somewhat of a mad dash to get Explorer 1 ready, the Army Ballistic Missile Agency had been creating reentry vehicles for ballistic missiles, but kept up hope of getting something into orbit. At the same time Physicist James Van Allen of Iowa State University, was making the primary scientific instrument payload for the mission. As well this, JPL director William H. Pickering was providing the satellite itself. Along with Wernher Von Braun, who had the skills to create the launch system. After the Vanguard failure, the JPL-ABMA group was given permission to use a Jupiter-C reentry test vehicle (renamed Juno) and adapt it to launch the satellite. The Jupiter IRBM reentry nose cone had already been flight tested, speeding up the process. It took the team a total of 84 days to modify the rocket and build Explorer 1.

Preparing the explorer 1
Explorer 1 is mated to its booster at LC-26

The satellite itself, designed and built by graduate students at California Institute of Technology’s JPL under the direction of William H. Pickering was the second satellite to carry a mission payload (Sputnik 2 being the first). Shaped much like a rocket itself, it only weighed 13.37kg (30.8lb) of which 8.3kg (18.3lb) was the instrumentation. The instrumentation sat at the front of the satellite, with the rear being a small rocket motor acting as the fourth stage, this section didn’t detach. The data was transmitted to the ground by two antennas of differing types. A 60 milliwatt transmitter fed dipole antenna with two fiberglass slot antennas in the body of the satellite, operating at 108.3MHz, and four flexible whips acting as a turnstile antenna, fed by a 10 milliwatt transmitter operating at 108.00MHz.

Explorer 1 parts
A diagram showing some of the main parts of the Explorer 1 satellite

As there was a limited timeframe, with limited space available, and a requirement for low weight, the instrumentation was designed to be simple, and highly reliable. An Iowa Cosmic Ray instrument was used. It used germanium and silicon transistors in the electronics. 29 transistors were used in the Explorer 1 payload instrumentation, with others being used in the Army’s micrometeorite amplifier.  The power was provided by mercury chemical batteries, what weighed roughly 40% of the total payload weight. The outside of the instrumentation section was sandblasted stainless steel  with white and black stripes. There were many potential colour schemes, which is why there are articles models and photographs showing different configurations. The final scheme was decided by studies of shadow-sunlight intervals based on firing time, trajectory, orbit and inclination. The stripes are often also seen on many of the early Wernher Von Braun Rockets.

NASM flight spare
The flight ready spare of the Explorer 1, now shown at the National Air and Space Museum.

The instrument was meant to have a tape recorder on board, but was not modeled in time to be put onto the spacecraft. This meant that all the data received was real-time and from the on board antennas. Plus as there were no downrange tracking stations, they could only pick up signals while the satellite was over them. This meant that they could not get a recording from the entire earth. It also meant that when the rocket went up, and dipped over the horizon, they had no idea whether it got into orbit. Half an hour after the launch Albert Hibbs, Explorers System designer from JPL, who was responsible for orbit calculations walked into the room and declared there was a 95% chance the satellite was in orbit. In response, the Major snapped: “Don’t give me any of this probability crap, Hibbs. Is the thing up there or not?”.

Explorer 1 Mission Badge
The official JPL mission pac=tch for the Explorer 1 mission.

The instrument was the baby of one of Van Allens graduate students, George Ludwig. When he heard the payload was going into the Explorer 1 (and not the Vanguard) he packed up his family and set off for JPL to work with the engineers there. He has a good oral history section on this link, talking about designing some of the first electronics in space. He was there watching the rocket launch and waiting for results. From the Navy’s Vanguard Microlock receiving station they watched the telemetry that reported the health of the cosmic-ray package. The first 300 seconds were very hopeful, with a quick rise in counting rates followed by a drop to a constant 10-20  counts per second, as expected. The calculations told them when they should hear from the satellite again, but 12 minutes after the expected time, nothing showed up but eventually, after pure silence, Explorer 1 finally reported home.

The Van Allen Belt
This diagram showcases the Van Allen belts, which were first detected by instruments aboard Explorer 1 and Explorer 3. The Van Allen belts were the first major scientific discovery of the space age.

Once in orbit, Explorer 1 transmitted data for 105 days. The satellite was reported to be successful in its first month of operation. From the scientist point of view, the lack of data meant the results were difficult to conclude. The data was also different to the expectations, it was recording less meteoric dust than expected and varying amounts of cosmic radiation, and sometimes silent above 600 miles. This was figured out on Explorer 3 when they realised the counters were being saturated by too much radiation. Leading to the discovery of the Van Allen Radiation Belt. Although they described the belt as “death lurking 70 miles up” it actually deflects high energy particles away from earth, meaning life can be sustained on earth. The satellite batteries powered the high-powered transmitter for 31 days, and after 105 days it sent it’s last transmission on May 23rd 1958. It still remained in orbit for 12 years, reentering the atmosphere over the pacific ocean on March 31st after 58,000 orbits.

Semi Autonomous Robotic Platform

As part of my degree I had to complete a project as part of the third year in the field of robotics and electronics. I chose to make a robotic platform, a simple idea that could be completed to a high quality with the right amount of effort. What is a robotic platform I hear you ask? well it essentially is a small buggy/rover that that moves around an assigned area completing simple jobs such as transporting goods, picking up parcels or any job that needs a moving vehicle. Usually autonomous, and very expensive, the majority of systems are very application specific. Some simple systems without any sort of control system can cost tens of thousands of pounds, and are not easy for the average employee to operate. Tackling the problem of expensive, application specific robotic platforms was the basis of my project.

4WD robotic platform
The Nexus 4 wheeled drive mecanum robot has an arduino based control system, and mecanum wheels, but will set you back $1500

Named the Semi Autonomous Robotic Platform, the idea was very simple, make a modular system, with building blocks that could be easily interchanged, and didn’t cost the world. These modules were things like motor controllers, sensors and power systems. If a user had a working platform built from this system, it would take minimal effort to swap out any of these modules to bigger motors or better sensors. This means a user can make a robot and only buy the bits they need, and even make their own modules, as long as they fit to the standard written as part of the project.

system block diagram
The initial block diagram of the system, showing how the modules can be controlled in hierarchy structure.

In most robotic systems, mainly to keep costs cheap, there is one controller that controls everything. This idea makes sense for small integrated systems that don’t need to change, but doesn’t really work when systems need to be dynamic. For instance, say you decide that your DC motors driving your robot aren’t giving you the control you want. You source some stepper motors, but this means completely changing the motor controller and therefore the software that controls it. Because one controller is in charge of everything, the software for the whole system needs to be re-written, and re-tested. That small change could have affected any of the other systems that that controller is in charge of. Make a change that breaks something important, you could set back a project weeks. This shows how painful a setup like this can be, especially when it starts to become a complex robot. Add on top of that the potential for computer intensive algorithms being used on the robot, like route planning or SLAM, and that controller suddenly has a lot to do. My system design separates these jobs out to a selection of individual controllers, such as a system specifically for motor control, or power systems. These controllers can deal with the nitty gritty hardware, and leave the master controller to orchestrate a higher level version of control.

Final Year Project
My design, near the end of the project, with the mecanum wheels, ultrasonic sensors and multiple controllers.

The added benefit of separating out all these jobs means that multiple engineers can work on the same robot, at the same time on different areas and not be worried about breaking the other person’s design. The system specification defines how the modules interact in terms of communication speeds/type, the way to alert other modules and how those communications are scheduled. The master controller (shown in the system block diagram in green) schedules all these communications and decides which modules need specific information. Warnings, control signals and user inputs are all calculated and scheduled, then communicated to and from the required modules. A power system doesn’t care that a user has pressed a button to scroll through an LCD screen, and the master controller means it doesn’t see it.

The above video shows how the robot moves with its mecanum wheels, and how it can easy move around environments. I will explain the more technical parts of the project in a later post, but this simple idea became a very heavy hardware based project, rather than the software project it started as. I learnt about mechanical design, PCB design and good techniques associated with electronic design. For these reasons, the robot won the “Best Project” award for 2017. Thank you to: Cubik Innovation for help with electronic design, and providing PCBs, VEX Robotics for donating the wheels, and Altium Designer for providing their electronic design software. I would not have been able to produce the robot I did without them.

Arianespace Launches a Successful Soyuz

VS18 liftoff
VS18 taking off from the Soyuz Launch Complex (ELS) near Sinnamary.

At 17:10 UTC on the 9th of March 2018, Arianespace launched its second rocket of the year from Guiana Space Center at Kourou. Designated VS18, the Soyuz rocket launched four O3b Satellites into orbit more than 3 years after the last O3b launch. Controlled by a Russian ground crew from the Soyuz Launch Complex (ELS) near Sinnamary, there was a 33 minute delay to the start because of bad weather. The Soyuz used was a Soyuz 2-1b/Fregat placing the satellite in Medium Earth Orbit (MEO).

The VS18 launch from Instagram
The VS18 launch from the Instagram of Arianespace.

A somewhat complex launch, the first ascent lasted 9 minutes and 23 seconds placing the launcher in a sub orbital trajectory. After separation the Fregat performed a 4 minute burn to reach 160 x 205 km x 5.16 deg parking orbit. Coasting for 8 minutes, the Fregat performed its second burn for 8 minutes and 36 seconds to enter  a 190 x 7,869 km x 3.88 deg transfer orbit. Then after a coast of 1 hour and 21 minutes to the apogee, the Fregat fired for its third and final time for 5 minutes and 6 seconds, to enter its 7,830 km x 0.04 deg insertion orbit.

Poster of VS18 launch
Poster advertising the VS18 launch from the Arianespace website.

After the third burn, the satellites were release two at a time, with opposite satellites released at the same time. The first were released 2 hours into launch, and the second set 22 minutes later after a short firing of the Altitude Control System. The rocket then performed 2 more burns to lower its orbit to 200 km below the O3b release point. This was a disposable orbit, intended so that it will not interfere with working satellites.

The four 700kg satellites
The four 700kg satellites being lowered being loaded into the fairing, before the launch. Image from Arianespace website.
The O3b Satellites being prepared to be transported
One of the O3b Satellites being prepared to be transported to the launch site.

The Ka band satellites are the fourth set of O3b to be sent up, making the total constellation 16. Arianespace intend to launch the next set of four in 2019. “The new Ka-band satellites will join the existing O3b constellation to deliver high-speed connectivity to people and businesses in the growing mobility, fixed data and government markets,” Arianespace officials said in a statement. It was reported that the launch was a success, and the Luxembourg based satellite operator SES Networks now have control of the O3b’s.

The fairing of VS18 ready to launch
The fairing of VS18, ready to be attached to the Soyuz rocket, picture from Arianespace website.

The second launch of the year, Arianespace delayed the launch from the original March 6th launch date. This was postponed to conduct extra checks, likely inspired by the partial failure of the Ariane V earlier this year. On January 25th the company lost contact with the upper stage of the rocket. The 3 satellites on board did reach orbit despite the anomaly, but Arianespace have been quiet on the condition of them.

Launch of VS18 with four Ob3
Launch of VS18 with four Ob3 satellites on board. Image from Arianespace website.

How Going To The Moon Kick-started the Silicon Age

In the late 1950’s, there were three people who were at the epicenter of a huge breakthrough in the world of electronics, the invention of the Integrated Circuit (IC). Jack Kilby of Texas Instruments, Kurt Lehovec of Sprague Electric Company, and Robert Noyce of Fairchild Semiconductor. In August 1959, Fairchild Semiconductor Director of R&D, Robert Noyce asked Jay Last to begin development on the first Integrated Circuit. They developed a flip-flop with four transistors and five resistors using a modified Direct Coupled Transistor Logic. Named the type “F” Flip-Flop, the die was etched to fit into a round TO-18 packaged, previously used for transistors. Under the name Micrologic, the “F” type was announced to the public in March 1961 via a press conference in New York and a photograph in LIFE magazine. Then in October, 5 new circuits were released, the type “G” gate function, a half adder, and a half shift register.

The Type F flip flop
Junction-isolated version of the type “F” flip-flop. The die were etched to fit into a round TO-18 transistor package
Type F life image
Physically-isolated Micrologic flip-flop compared to a dime from LIFE magazine March 10, 1961

These first few integrated circuits were relatively slow, and only replaced a handful of components, while being sold for many times the price of a discrete transistor. The only applications that could afford the high prices were Aerospace and Military systems. The low power consumption and small size outweighed the price drawbacks, and allowed for new and more complex designs. In 1961, Jack Kilby’s colleague Harvey Craygon built a “molecular electronic computer” as a demonstration for the US Air Force to show that 587 Texas Instruments IC’s could replace 8,500 discrete components (like transistors and resistors) that performed the same function. In 1961, the most significant use of Fairchild Micrologic devices were in the Apollo Guidance Computer (AGC). It was designed by MIT and used 4,000 type “G” three input NOR gates. Over the Apollo project, over 200,000 units were purchased by NASA. The very early versions were $1000 each ($8000 today) but over the years prices fell to $20-$30 each. The AGC was the largest single user of IC’s through 1965.

apollo guidance computer logic module
Apollo logic module assembled by Raytheon to be used in the AGC
Type G micrologic
Philco Ford also produced the Fairchild Type ‘G’ Micrologic gate for the Apollo Guidance Computer – this is the flat pack verison

Note that although Fairchild designed and owned the type “G” device, they were mostly made by Raytheon and Philco Ford under licence from Fairchild. Over this time many semiconductor manufacturers such as Texas Instruments, Raytheon and Philco Ford were also making large scale silicon production for other military equipment. These included the LGM-30 Minuteman ballistic missiles, and a series of chips for space satellites. This major investment from the government and the military kick started the development of the increasingly complex semiconductor, and eventually forced the prices low enough for non military applications. The processes improved and by the end of the Apollo program, hundreds of transistors could be fitted into an IC, and more complex circuits were being made. Eventually the costs of adding more transistors to a circuit got extremely low, with the difficulty being the quality of manufacturing. It could be argued that NASA and the Pentagon paved the way for silicon device production as we know it today.

Four Bit Carry Adder/Subtractor Circuit

After creating my 1 bit full adder design found in a previous post, I decided to go for something a little more complicated. I wanted to prove to myself that the ripple carry system worked, so the obvious choice is to make a multi bit device. 4 bits seemed like a good amount, it’s a value used in some early ALU’s so it can be used in a future project. To make it more interesting I added in the ability to make the device a Subtractor at the same time. When you look at the schematic, it only requires one more device per adder, so it’s not even an expensive thing to implement, but adds lots of functionality. As with the 1 bit adder, I have attempted to build this adder using only single logic chips.

4 bit adder-subtractor circuit

The first stage is to know the logic circuit, its widely known and can be found pretty easily all over the web. I’m not going to explain how it’s created (I can always make a separate post on that) but I can describe how to use it. The aim is for the device to take two 4 bit inputs (0 – 15), along with a carry from another adder. So the adder needs to be able to output a value between 0 and 31. In binary this can be shown as 5 bits, so we have 2 outputs. This the S output is a 4 bit bus, and the Co output bumps this up to the 5 bits we need to make 31. A truth table can be made for this but it would be 32 lines long, so too much for this post. You could regard it as a personal challenge if you want to attempt it on your own.

So I got onto Altium and made a schematic of this circuit using some of the low voltage 7400 LVC series individual logic gates that I used on the previous adder I made. They come in SOT23-5 packages which are leaded a nice size to solder. Plus they are a size where it’s possible to probe the pins fairly easily. Luckily Altium shows the components as their logic symbols. Below I have shown the first two adders, the third and fourth are basically the same as the second one, which is the idea of the ripple carry adder.

The first two adders of the four found on the board

I also added a few LEDs to show what parts are on and off. This means the user can see the inputs and outputs. These LEDs run off the 5V input voltage, and have 220Ω current limiting resistors in series with them. Also, I have put in some 0.1 inch header pins so it can be attached into a breadboard and maybe even a micro.

The LEDs for the carry bits and outputs
The LEDs for the input bits

As a base of my circuit, I have decided on a double sided 100mm x 100mm board. This is quite big as you can see for the circuit I have made, but gives plenty of space for a soldering iron to get access. As well as this, it gives a nice amount of space for multimeter probes. I also tried to keep the individual logic chips in a similar arrangement as the schematic. This is meant to be used as a learning device, so it’s useful for the chips to line up with the diagram. The header pins for the inputs and outputs are placed on opposite sides of the board to make it more obvious for the user to see it. And the pins have designators written on the board so the user can see what each pin does. The input and output busses are placed in fairly logical places, and grouped together. There is no point having all the A inputs intertwined with the B inputs. The pins for the power and ground are on opposite sides with their own headers, only one needs to be connected for it to work. The LEDs that are directly attached to the pins are placed closer to the logic circuitry, but labeled clearly on the silkscreen. Most of the routing to the LEDs is on the underside of the board, else the top could get confusing. All the designators for components have been made half the normal size due to the small amount of parts used in the project. The below images show the PCB layout I created with the top copper being red, bottom copper being blue, and the silkscreen shown in yellow.

Top Copper

As you might be able to see, I have tried to keep all the power on the bottom side of the board. This leaves lots of space for the logic signals on the top, where the user is more likely to see. As you can see, most of the inputs and outputs of the circuit are also on the bottom side. This is because the way the busses work and input into the adder needs lots of crossing over and would add confusion into the design. This is why labels were used instead.

Bottom Copper

To make it easier to see, I made a larger image of the first and last adder in the series. As you can see, the only real difference in them is that the first has the add/subtract input shown by an LED, whereas the last shows the carry from the previous adder (C0). This is because the A/D bit is attached to all the adders, but the first bit doesn’t have a carry bit input. The carry on that adder is the input for the A/S. It serves the function of inverting the first bit, so that it works like 2’s complement when in subtract mode.

The layout of the first adder in the series
The layout of the last adder in the series

As noted above I used 7400 LVC series logic gates. The SOT23-5 package chips have the suffix of “BVD”. See the datasheets for each of the devices for more information. I have written a simple bill of materials below:

12x SN74LVC1G86DBVT – XOR gate
8x SN74LVC1G08DBVT – AND gate
4x SN74LVC1G32DBVT – OR gate
17x DO-214 LED’s
17x 0805 220Ω resistors
6x 5-pin 0.1″ header pins

The main downside to this type of adder is that is is very slow. Especially when you get to high bit amounts that you are trying to add. This adder will take at least 4 times as long as a single adder to add the two numbers together because the signal has to propage through 4 full adders. This problem is known as propagation delay, each logic chip will take a very short time to compute the output. Although this time is not perceivable by the human eye, if there are 100’s of logic gates in a row, then the delays start to add up and be a problem. If this circuit is to be used in a computer, it could need to make calculations thousands, or maybe millions of times a second, and a carry bit adder is not generally good at that. There are other, faster adders that I will show in a future post.

Why James Webb Was so Important

NASA Administrator James E. Webb
NASA Administrator James E. Webb. This was his official NASA photograph

There are not many people who know off the top of their head who James Webb is, even many lovers of space may not know who he was. Yet they are about to launch the James Webb Space Telescope into space to replace Hubble. James Webb wasn’t an engineer, or a physicist, or even really an academic; he was a lawyer and politician. He turned a small government research department into an organisation that had links to almost every state, and had control of 5% of the US federal budget. Webb’s NASA controlled the jobs of half a million workers across America, and he introduced new working practices and management techniques that are still used today.

If you were to go out and read the biographies of the astronauts, or histories of spaceflight, Webb doesn’t really come up. He was portrayed as just a bureaucrat in Washington, funnelling orders down the chain, living the politician life. In this new age of spaceflight, we see the Apollo years as some sort of poetic story, with NASA being the figurehead of the battle to win space against the evil russians. In 1961 though, America did not follow this narrative, nobody in America cared about space, least of all the brand new president, John F Kennedy. When he set up his first reshuffle of the cabinet they simply could not get anyone to run NASA, they asked 18 high level politicians, and everybody said no, space was a dead end job, and NASA was just a collection of squabbling mission centres. Eventually, JFK’s vice president, Lyndon B. Johnson suggested Jim Webb, a guy who had worked under the Roosevelt administration and had some experience with private businesses. When asked, by JFK personally, Webb agreed to run NASA, as long it was the way he wanted it. JFK, desperate for an administrator gladly agreed.

shaking hands with JFK
President Kennedy shakes hands with NASA Administrator James Webb

There had been heavy opposition to the idea of manned spaceflight. Up to this point, the head of the President’s Science Advisory Committee, Jerome Wiesner, had issued a critical report on project mercury. Kennedy, as a senator he had openly opposed the space program and wanted to terminate it. Kennedy put his vice president LBJ as the head of the National Aeronautics and Space Council because he had helped create NASA, but it was mainly to get him out of the way. Although Kennedy did try and reach out for international cooperation in space in his state of the union address in January 1961, he got nothing from Khrushchev. Kennedy was poised to dismantle the effort for space, purely because of the massive expense.

The space Council
Vice President Lyndon B. Johnson (seated, center) presides over a meeting of the National Aeronautics and Space Council.

He began his NASA administration on February 14th 1961. A month later on April 12th, Yuri Gagarin became the first man to orbit the earth. Reinforcing some fears that America was being left behind in a technological competition with the Soviet Union, America suddenly cared about space. Kennedy made a U-turn and space sped to the top of the list.  This lead to Kennedy making his famous speech on May 21st where he spoke those famous words “we will put a man on the moon before the decade is out”. Kennedy wanted to take lead in the space race. Suddenly, putting a man on the moon was the number one priority.

Kennedy Talking to Congress
MAy 1961, Kennedy proposes landing a man on the moon to congress. LBJ and Sam Rayburn sit behind him.

This meant that James Webb just got handed the opportunity to run the biggest single project the country had ever seen. Webb was told to go back to his engineers and figure out how much it will cost to get to the moon. His engineers came up with the number of $10 billion (a scary big number in the 1960’s), and sheepishly told Webb, expecting to be told to make cuts and slashes to the plan. Instead he told them to go higher, because he knew problems would come their way, and extra money will need to be spent, so they come back with the figure of $13 billion. Webb accepts the number, and goes to congress and tells them he needs $20 billion over the next 7 years. Jaws hit the floor, but he used this political knowledge to get a huge amount of leverage.

The key leverage he had was jobs, and he knew it. At its height, NASA employed half a million people in some form, that’s roughly the number of people living in Wyoming. The two biggest investments were in Cape Canaveral, FL and Houston, TX. The most controversial was the Manned Spaceflight Centre in Houston, donated by Rice University. Originally based in Langley Virginia, and named the Space Task Group, the senator didn’t care much for space. The entire operation was moved to Houston, LBJ’s home state. It was central, and had good universities surrounding it. There were many Texas based representatives in the space political landscapes at that time, such as Sam Rayburn, the speaker of the House of Representatives.

Johnson Space Centre
Manned Spaceflight Centre, Texas, one of the biggest employers in Texas for a long time. with over 3000 federal workers, and 100 buildings

One thing that Webb understood was what NASA needed to run. He implemented a very flat organisational structure, with very few middle managers. Webb was the very top, controlling Washington. He also had the head of NACA (precursor to NASA) Hugh L. Dryden as an associate director. He had overseen the development of the x-15, and understood the technical needs of Apollo. Also Robert Seamans, also an associate director, acted as the general manager of NASA, and oversaw the everyday running of the program. Using a team of people, each with their own particular strengths helped NASA, especially in the early growth years, much more so than any one of them could achieve on their own.

Webb in a Gemini Trainer
Webb in a Gemini Trainer

Part of what James Webb did, to the dislike of congress, was to invest in academia, specifically universities. $30 million dollars a year was put into the Universities Development Fund. A fund designed to help students get into engineering, and to develop talent, skills, and academics that could not only work for NASA, but help the science behind it. As it was taken from a fund that congress had no control over, the money continued to help 7000-8000 students a year get through university at a time where NASA needed engineers. Webb believed that NASA was more than just the one shot to the moon, and frequently fought with the presidents on that fact. He wanted NASA, and space exploration to benefit science, engineering and even society. He believed that this project could fix other problems not even related to space, such as poverty and disease. The management style of NASA, and the way these big projects were handled showed the impossible could be achieved. He frequently lectured on this subject, and universities became an important part of NASA.

Launch_Complex_34_Tour
Webb, Vice President Lyndon Johnson, Kurt Debus, and President John F. Kennedy receive a briefing on Saturn I launch operations

There was huge pressure from washington to spend all of NASA’s budget purely on the Apollo moonshot. Webb was instrumental in making sure that NASA and spaceflight was more than that. be made sure other projects like the Mariner and Pioneer space programs happened, and that JPL still functioned even with a terrible track record at the time. At the time, the academic community worked with NASA, in large part because of the importance Webb put on furthering science. Webb would frequently lecture at universities, and teach about the management styles that made NASA was. Unfortunately, some in Washington didn’t care for the extra spending, especially the states that did not have a mission centre or any of the major manufacturing plants located there. So when the Apollo 1 fire happened, there were a small group that were willing to use it as a way to make changes.

Closeup of James E. Webb, National Aeronautics and space administration

The Apollo 1 fire was a very unfortunate accident, and a national tragedy. For some, it highlighted some major problems with the Apollo program and how it had been run by the major contractor North American Aviation. Committees were set up, and Webb suddenly went from running NASA to trying to defend it. During the inquests, NASA still ran, it continued to fix problems and aim for the moon. This was because James Webb was there defending it. Left to just take the heat, some believe (me included) NASA’s funding would have been significantly cut, and we may have never got to the moon. Webb stood up in Washington and fought hard for the continuation of the project, defending the decisions that his team had made. At the end of it, he had used up most of his political sway, and called in so many favours that NASA was safe for the time being, and that Apollo was possible.

Webb presents NASA’s Group Achievement Award to Kennedy Space Center Director Kurt H. Debus, while Wernher von Braun (center) looks on

At this point, Johnson had decided not to run for re-election, Webb felt that he should step down to allow Nixon to choose his own administrator. On October 7, 1968 he stepped down from office. To put that into perspective, Apollo 11 landed on the moon July 20th, 1969, barely a year later. Webb went on to be a part of many advisory boards and served as regent for the Smithsonian institute. He died in 1992, and was buried in Arlington National cemetery.

This post was inspired by reading the book: The Man Who Ran The Moon by Piers Bizony. For anyone interested in the subject of how Webb actually made his dealings, and a much more detailed account of how NASA became what it is, I recommend this book. He also did a Lecture on Webb that I found on YouTube where he tells the story really well.

 

One Bit Adder Project

One thing that has always been interesting to me is using logic circuitry in electronics. It’s easy to implement something on a microcontroller in just a few lines of code, but the real challenge comes from making a boolean project using real logic gates. It’s something we all learn about if you have taken a basic computer science class, or even digital electronics. One of the first circuits you ever learn about is the adder. It’s pretty simple, teaches you how to cancel down boolean equations, and only has a few inputs and outputs. I have decided to try and make the circuit using real components, and see if I can get it to work.

full adder layout

The first stage is to know the logic circuit, its widely known and can be found pretty easily all over the web. I’m not going to explain how it’s created (I can always make a separate post on that) but I can describe how to use it. The aim is for the device to take two 1 bit inputs, along with a carry from another adder. So the adder needs to be able to output a value between 0 and 3. In binary this can be shown as 2 bits, so we have 2 outputs. The S output represents bit 1, and the Co output represents bit 2. Below is the truth table I used, if you want a little challenge, try and get the above circuit using boolean algebra.

A B Ci Co S
0 0 0 0 0
0 0 1 0 1
0 1 0 0 1
0 1 1 1 0
1 0 0 0 1
1 0 1 1 0
1 1 0 1 0
1 1 1 1 1

So I got onto Altium and made a schematic of this circuit using some of the low voltage 7400 LVC series individual logic gates. They come in SOT23-5 packages which are leaded and a nice size to solder. Plus they are a size where it’s possible to probe the pins fairly easily. Luckily Altium shows the components as their logic symbols.

1 bit adder 1 schematic

I also added a few LEDs to show what parts are on and off. This means the user can see the inputs and outputs. These LEDs run off the 5V input voltage, and have 220Ω current limiting resistors in series with them. Also, I have put in some 0.1 inch header pins so it can be attached into a breadboard and maybe even a micro.

1 bit adder 1 schematic

As a base of my circuit, I have decided on a double sided 50mm x 50mm board. This is quite big as you can see for the circuit I have made, but gives plenty of space for a soldering iron to get access. As well as this, it gives a nice amount of space for multimeter probes. I also tried to keep the individual logic chips in the same arrangement as the schematic. This is meant to be used as a learning device, so it’s useful for the chips to line up with the diagram. The header pins for the inputs and outputs are placed on opposite sides of the board to make it more obvious for the user to see it. The pins for the power and ground are on the same side on both headers. The LEDs that are directly attached to the pins are kept close to them, and the track is fairly obvious to show where the signal is from. The silkscreen labels which LED designates which input/output. All the designators have been made half the normal size due to the small amount of parts used in the project. The below images show the PCB layout I created with the top copper being red, bottom copper being blue, and the silkscreen shown in yellow.

1 bit adder 1 PCB top

As you might be able to see, I have tried to keep all the power on the bottom side of the board. This leaves lots of space for the logic signals on the top, where the user is more likely to see. As you can see, not all signals are on the top side due to circuit constraints, but signals that do swap over are generally short jump, and straight lines, This makes it more obvious where the tracks go without having to flip the board.

1 bit adder 1 PCB bottom

As noted above I used 7400 LVC series logic gates. The SOT23-5 package chips have the suffix of “BVD”. See the datasheets for each of the devices for more information. I have written a simple bill of materials below:

2x SN74LVC1G86DBVT – XOR gate
2x SN74LVC1G08DBVT – AND gate
1x SN74LVC1G32DBVT – OR gate
5x DO-214 LED’s
5x 0805 220Ω resistors
2x 5-pin 0.1″ header pins

The Foundry: Drilling an Air Hole

At this point we had a cast foundry base, made out of sand and plaster of paris. To see how that was made, see the tutorial here.  Before we first test it though, we had to make one modification, and that was to drill a 30mm diameter hole in the side of it.

The hole from the outside
The hole from the outside

The idea of the hole is to allow air to come in and fuel the fire. The theory goes that the air comes in the side, and the resultant fumes (like smoke) leave via the opening at the top. It makes sense because heat rises, and takes all those hot resultant gasses up with it. Note that we don’t really care about the fumes coming off the fire at this point, we just want as much oxygen as possible to get to the coals. If hot exhaust fumes are leaving via the same hole as the oxygen, but going the opposite direction, they will interact with each other, slow each other down, and make the furnace much more inefficient.

Also notice the hole is angled down into the base of the furnace. This isn’t by accident, we want that hole to do two things, pump air into the base of the fire, and not let anything go back up the hole. This hole in the future may contain a fan, to pump more air in. We don’t want the embers flying back up the pipe and breaking the fan during use.

To drill the hole we used a hammer drill bought from Aldi, and a 30mm masonry drill bit, these parts can be pretty cheap if you search around, and the hole doesn’t have to be this exact size. Use what you can find, and make sure you get help when doing the drilling. As always, safety is important, and safety glasses and gloves would be a good idea. if one person steadies the foundry, while the other drills, it is much easier. Go slow, so that the plaster on the inside doesn’t break too much. It is easy to be too eager and create large cracks and chips, which could mean an entire restart.

The hole from the inside
The hole from the inside, notice the dust, and broken parts around the hole.

Although this was a shorter post, the next one will be about the first tests! As always, thanks for reading, and I hope to be along with another update soon. If you guys have any tips, questions, or want to show your foundry, please post in the comments below.