Stephanie and I attended the YWC conducted by PPPL at Princeton University on March 16, 2023. This conference introduces middle-school and high-school-aged girls (in 7th to 10th grades) to women scientists and engineers and the wide breadth of careers available to them in these fields. Prominent women scientists and engineers from around the region spend the day with the girls engaging them in different variety of formats that include small-group presentations, hands-on activities, a keynote address, and a chemistry demo. This event is a great motivation for the girls to choose STEAM as their career.
We had 3D printed models of the Princeton Field reversed Configuration (PFRC), a Poster of Direct fusion drive, Spectroscopy diagnostic poster that demonstrated the visible and X-ray diagnostics that are performed to predict the electron temperature, impurities, and how these vary with other experimental parameters such as pressure, magnetic field and RMF-heated power in PFRC.
I demonstrated how visible light can be split into different wavelengths using a hand-held spectroscope. Visible light waves are electromagnetic waves. We see these waves as the colors of the rainbow. Each color has a different wavelength. Red has the longest wavelength, and violet has the shortest wavelength. These different colors of waves together make white light. The girls enjoyed observing different wavelength colors using the handheld spectroscope It was fascinating to see around 800 students after the Pandemic for this conference.
Lastly, we enjoyed the keynote talk by Dr. Liz Hernandez-Matias. Sr. Educational Specialist, CienciaPR.
I attended Submarine Supplier Days 2023 in Washington, D.C. March 7 and 8. It is an opportunity for companies contributing to building the latest attack and ballistic missile submarines to get together. The two big programs are for the Columbia Class fleet ballistic missile submarine and the Virginia Class attack submarines. Australia will be buying four of th e latter. I attended the meeting to introduce people to the potential of PFRC as a power plant for future submarines. The first day was a series of presentations on the latest submarines.
On the next day we visited the offices of our N.J. U.S. Representatives and Senators to gain their support for the submarine programs. Here is the inside of the Senate office building with its Calder sculpture.
It was fun to meet people building the submarines. One company in New Jersey has a sole source contract to weld components of the submarines. Each weld is signed by a welder so it can be traced back should a problem arise.
I learned that there are major problems with materials supply and with finding workers to build the submarines. Lead times on some materials can be 80 months. The issues of on-again/off-again production were also discussed. We all agreed, as did the Congressional and Senate staffers, that continuing resolutions were bad.
One of the biggest concerns people have with electric vehicles is charging. We’ve taken our Mach-E on two trips with different approaches to charging. Our experience is with a rear-wheel drive Mach-E with the extended range battery. Its EPA range is 303 miles.
The first was from Princeton to the Berkshires, then to Boston and then back to Princeton. The trips were made without any charging on the way. We used Level 2 chargers at our destinations. The Williams Inn, in Williamstown, had ChargePoint chargers, as did the Cambridge Marriott in Kendall Square in Cambridge, MA. At the Cambridge Marriott, there are ChargePoint chargers in the garage used by the valets. The valets are willing to plug your car in as long as you have a ChargePoint card.
The picture blow shows our current mileage.
The most recent trip was from Princeton to Pittsburgh. The one-way distance of 330 miles necessitated charging on the road. We used the Ford app, which showed two stops. We didn’t follow its plan. Instead, we broke the trip into two segments each way with one charging stop. Prior to the trip we tested the high power charging at a local EVGo station.
In both directions we stopped at the Electrify America charging station at 1098 Harrisburg Pike in Carlisle. It was only 2 miles from the highway at a location with the Sheetz convenience store. There were two 350 kW chargers and two 150 kW chargers. Here is the station on the way to Pittsburgh.
It took about 20 minutes to charge from 30% to 80%. We charged until Apple Maps said we had 20% battery margin at our destination. In both directions we ended up with about 15% margin. In Pittsburgh we did destination charging at the Forbes Tower garage. The garage was $22 for 24 hours and charging was free. It was a short walk from the Residence Inn.
On the way to Pittsburgh we were joined at the charging station by two Ford F-150 Lightning trucks. On the way back, we were joined by another Mach-E.
The Electrify America stations were seamless. We have 250 kWh of free charging from Ford. The station knew all about the free charging and we didn’t have to pay or do anything else to be reimbursed. It was simply plug and charge.
PlugShare was the most reliable way to find charging stations.
We drove a Tesla Model 3 as a Hertz rental In Chicago. We charged once at a SuperCharger. It worked very well! I’d say the Electrify America experience was its equal.
I worked on two projects during my winter internship at Princeton Satellite Systems: a two-stage-to-orbit (TSTO) launch vehicle design proposal related to the NASA Space Launch System (SLS) and a satellite conjunction maneuver demo. These both used the Spacecraft Control Toolbox for MATLAB.
One of the main ideas behind the TSTO launch vehicle project is to propose an all-liquid variant of the SLS. Currently, the SLS first stage is mostly powered by two solid rocket boosters (SRB) upgraded from the Space Shuttle SRBs. However, our proposal is to replace the two SRBs with five liquid boosters (LB), each mated with an RS-25 engine. The second stage would remain the same. Using MATLAB, I analyzed the launch and trajectory performance of both variants and found similar performance. Additionally, the total mass of the all-liquid SLS variant would be approximately two-thirds the mass of the SRB-powered spacecraft. An approximate CAD model of the all-liquid SLS version is shown below.
In addition, the LBs can be used independently to power smaller high-performance TSTO launch vehicles that carry around 8,000 kg of payload to low earth orbit. Trajectory plots and a preliminary CAD model are shown below.
My other project this internship was to help out with a satellite conjunction avoidance demo with Ms. Stephanie Thomas. The goal was to create a solution in MATLAB to identify potential satellite-debris conjunctions and develop a method/algorithm to avoid the conjunctions. I mainly worked on testing the code and relevant functions and providing feedback about the solution’s comprehensiveness.
Overall, I greatly enjoyed this internship and the opportunity to work at PSS. I saw firsthand how even a small company can make significant contributions to aerospace and engineering through diverse interests yet specific, impressive skill sets.
A new paper, “Analysis and Mitigation of Pulse-Pile-Up Artifacts in Plasma Pulse-Height X-ray Spectra” by Taosif Ahsan and our team has been published open-access in MDPI Plasma. It describes the implementation of an algorithm, the two-photon trapezoidal uncorrelated-pulse model, to improve analysis of x-ray spectra emitted from PFRC-2 plasma. This model was developed to reduce artifacts in x-ray spectra caused by pulse pile-up, PPU (the phenomenon where x-ray photons are recorded nearly simultaneously so that only one x-ray photon is recorded with a combined energy), and diagnose the tail region to see if it is a pulse-pile-up artifact or if it has physical origins.
Experiments on the Princeton Field-Reversed-Configuration (PFRC-2) device explore nearly pure, ca. 99%, partially ionized, warm hydrogen plasmas. For these, great interest lies in the tails of the X-ray spectrum. The tail region is important as an electron temperature in the PFRC can be estimated by fitting a Maxwellian distribution. Small tails of high-energy electrons in the energy distribution (EED), even comprising less than 1% of the plasma density, can have large effects on the resistivity, stability, and reaction rates of the plasma.
This paper is a step toward understanding how PPU affects the tail region of spectra for detector-formed trapezoidal pulses. Here we focus on relatively low count rate (≤0.1/deadtime) spectra where primarily only two-photon pile-up needs to be considered. Extension of this work to multi-photon pile-up will be necessary to develop an analytical tool to diagnose and mitigate pile-up effects in the tail regions of higher count-rate spectra.
At MIT, we are given the month of January off from classes to pursue our own interests, whether they be career-oriented or hobby-based. During these five weeks, I have worked at PSS as a power electronics intern. My time at PSS has given me the opportunity to explore so many of the industry based applications of electronics and electrical engineering amongst some of the most innovative minds in the aerospace and energy industries.
Within the GAMOW (Galvanizing Advances in Market-Aligned Fusion for an Overabundance of Watts) project, my work centered around helping redesign, assemble, and test a power load switch, the resulting prototype of which is shown above. Within this project, I received a wide array of experience ranging from 3D-modeling PCB boards with Eagle software, to physical board assembly, to designing testing procedures for the completed board. Initially, I worked on redesigning the load switch PCB to reduce loop currents and noise. My next steps were to source and order all needed components for in-house assembly. During the assembly process, I worked with both a soldering iron and hot air rework station to assemble surface mounted devices (SMDs) and through-hole components.
I also dipped into some software based components of the project, programming in C and Python to create hardware based signals to our desired testing specifications. Specifically, I was aiming to make Pulse Width Modulation (PWM) signals of a specific duration for the Raspberry Pi to output. This led to various tests on the outputs of the code, through the use of an oscilloscope (two PWM pulses on the oscilloscope are shown below). Ultimately, I had the chance to start testing the board in connection with a power supply and the Raspberry Pi’s program.
Moreover, I had the opportunity to dip into so many different branches of electrical engineering and project design. In attending meetings about all of the individual components of the massive GAMOW project, I saw how the team plans and executes each individual collaborative part of the project. This experience in the project process and cutting edge electrical project design as a whole have given me many insights into the professional world of electrical engineering.
During my time at Princeton Satellite Systems, I worked on a momentum unloading project for NASA’s Gateway, a component of the Artemis program. I designed a deployable parasol that is controlled by Canadarm using Solidworks.
Solidworks is a platform I am familiar with, but I was still able to learn new functions. My favorite part of working with Solidworks is the puzzle-like nature of assemblies. When trying to make dynamic parts you have to think about how to best add relations without over-constricting or under-constricting the part. Once I finalized my initial design I was able to attend a Zoom meeting and present it to another company.
When not working on my Gateway project, I fiddled with the 3D printer to print models of the PFRC fusion reactor.
Although I have used 3D printers several times before, this time was more of a learning process. I was an acting 3D printer technician and wrote a guide with troubleshooting tips for future employees. Due to problematic unspooling and tangled filament the printer became jammed a few times, and I was unable to do the typical loading/unloading to set the filament free. This gave me the opportunity to take apart the 3D printer and see the internal mechanisms, which in turn allowed me to unjam the printer and solve the problem. I was thrilled to see inside the 3D printer and how the parts blend together!
Through my internship I learned about the complexity of the design process and how many things you need to consider when creating a product. Conceptualizing is one step, but bringing that concept into the real world requires much more research and planning. Overall, this internship was a great opportunity that allowed me to learn how to solve several engineering problems.
Our paper gives an overview of the Princeton Field-Reversed Configuration (PFRC) fusion reactor concept and includes the status of development, the proposed path toward a reactor, and the commercialization potential of a PFRC reactor.
The Journal of Fusion Energy features papers examining the development of thermonuclear fusion as a useful power source. It serves as a journal of record for publication of research results in the field. This journal provides a forum for discussion of broader policy and planning issues that play a crucial role in energy fusion programs.
Our latest paper on DFD applications, “A Fusion-Propelled Transportation System to Produce Terrestrial Power Using Helium-3 From Uranus”, is now available from AIAA. This paper was part of the Future Flight Propulsion track and AIAA SciTech 2023. For those with AIAA membership, there is a video recording of the presentation as well! Download the paper here.
Our goal with this paper is to create a framework within which we can study the potential cost of electricity produced on Earth using helium-3 mined from Uranus. The scarcity of terrestrial helium-3, along with the radioactivity of methods to breed it, lead to extraterrestrial sources being considered as a means to enable clean helium-3 fusion for grid-scale electricity on Earth.
This paper builds on the work of Bryan Palaszewski who has published numerous papers on mining the atmospheres of the outer planets. Palaszewski’s work assumed fission-based power and propulsion systems, with a much lower (worse) specific power than we anticipate from a PFRC-based Direct Fusion Drive. We consider both transport and mining vehicles that are instead fusion-powered, including a fusion ramjet. This ramjet may be able to be both the mining vehicle and the orbital transfer vehicle to bring the refined helium-3 to the interplanetary transport,
The results allow us to estimate levelized cost of electricity, LCOE, for the electricity produced on Earth as a function of assumed cost of the fusion transports and mining system, cost of the PFRC reactors, amount of helium-3 stored on each transport and numbers of trips per year, etc. You can learn more about LCOE from the NREL website. Uranus is likely the most economical outer planet for mining due to its lower gravity and radiation environment and high concentration of helium in its atmosphere, about 15%. We find that with our set of assumptions, the resulting cost of electricity could potentially be competitive with wind and solar.
Future work will include analysis of the fusion ramjet trajectories between mining and transfer altitudes, and research into sizing a mining payload using membranes and adsorption to separate the helium-3 from the helium, rather than depend on heavy cryogenic techniques.
The frequency we describe is that of the rotating magnetic field (RMF) which is generated by four radio-frequency antenna loops surrounding the machine. The RMF is responsible for creating a higher density field-reversed configuration plasma out of an initial lower density seed plasma and for heating the ions and electrons in the plasma.
The video below shows bright plasma pulses of increased density driven by RMF, now in various gases (argon, helium, and hydrogen):
Achieving bright plasma pulses is an important first step in operating at the new RMF frequency. This frequency will be within the range at which we expect ion heating to occur once we finish installation of the belt coils to increase magnetic field. We first observed bright plasma pulses at the new frequency of 1.8 MHz in argon gas due to its lower ionization potential in comparison to that of molecular hydrogen. In the experiment runs following the run with argon, we tuned parameters such as magnetic field, pressure, and seed plasma power until we began to see bright flashes in helium and hydrogen (where there is still a small percentage of argon). We are continuing work on optimizing the bright flashes for these gases.
In other good news, our two INFUSE awards with PPPL, which were announced this summer, have finally received all necessary approvals from DOE and are kicking off. Sangeeta and I (Chris) are at the lab helping to run the PFRC-2 experiment every week and will soon be running software simulations for the INFUSE projects. We will be studying plasma stabilization techniques and new antenna configurations, all to maximize plasma heating efficiency!
Stay tuned as we continue to update on our progress with the PFRC-2!