Michael Paluszek is President of Princeton Satellite Systems. He graduated from MIT with a degree in electrical engineering in 1976 and followed that with an Engineer's degree in Aeronautics and Astronautics from MIT in 1979. He worked at MIT for a year as a research engineer then worked at Draper Laboratory for 6 years on GN&C for human space missions. He worked at GE Astro Space from 1986 to 1992 on a variety of satellite projects including GPS IIR, Inmarsat 3 and Mars Observer. In 1992 he founded Princeton Satellite Systems.

# PRISMS Secondary School Student Builds a Sun Sensor

The Princeton International School of Mathematics and Science is a private secondary school in Princeton New Jersey.

http://www.prismsus.org

One of their students, Savva Morozov, undertook a project to build a miniature 2-axis sun sensor for a CubeSat. Here is his blog post!

My name is Savva, I’m a senior at Princeton Int’l School of Math & Science. This summer I designed, built and tested a 2-axis solar tracking sensor for Princeton Satellite Systems.

The sensor can determine the relative position of the sun using a set of photodiodes. Bearing in mind that the solar sensor would be used in vacuum environment, I decided to make the sensor out of printed circuit boards (PCBs) and solder them to each other. Originally, I wanted to 3D print the sensor, but shifted to the PCB solution to eliminate the risk of outgassing.

Picture 1: solar tracking sensor, 2nd prototype.

My solar sensor design resembles the shape of a square-based pyramid that is approximately the size of a quarter. It consists of 5 PCBs: 4 sides and a base to which the sides are attached. Each side contains a photodiode, and by measuring the voltage outputs from at least 2 of the diodes, the device can determine the sunlight’s direction.

One of the initial problems I encountered was the handling and attachment of the photocells to the side PCBs. Each cell came with an anode and cathode wires already soldered to its front and back. I desoldered the cathode wire from every cell and affixed them to the PCB using a space grade silver conductive epoxy. This way I attached the cell to the device and grounded its cathode at the same time. I thought I killed two birds with one stone, but instead I killed two photodiodes: they were damaged in the soldering process. I resolved the issue in the second prototype: I threaded the cathode wire into a hole in a side PCB and then glued the diode to that same board. This way I didn’t have to use soldering iron at all, preventing possible risks. I then connected the cathode of every photodiode to a common ground and outputted the voltage readings from each cell in a single data bus.

Picture 2: Solar sensor, 2nd prototype, quarter for scale.

The diode, being attached to the outer side of the satellite, might be exposed to light that is reflected off the Earth or satellite surfaces. To partially prevent this, I soldered a shield to the edge of the sensor. Each surface of the shield would be covered with non-reflective material to further decrease the amount of ambient light.

To protect the diodes from the impacts of micrometeoroids and other space debris, I plan to cover the diodes with a thin shield of hard glass crystalline window (tempered glass or sapphire).

Testing the first prototype indicated a number of drawbacks that were solved in the second. Such problems are attaching the shield and the cells to the device, decreasing sensor’s size while increasing its aperture, and making the assembly process simpler.

I also calibrated photocell’s voltage outputs and their exact positions to account for manufacturing imperfections and for those created during the manual assembly of the device. I wrote a program to calculate the vector of sunlight direction and using Processing IDE created a visual representation of my sensor as well as its output result:

Picture 3: Visual illustration of a working solar sensor.

In order for my sensor to survive the vacuum environment, I attempted to use only space qualified materials in the device’s assembly: PCBs, solder, epoxy, and sheets of copper. I have finished working on the development stage of designing the solar sensor. Testing procedures on my last prototype showed that such device would be ready for further usage and launch.

# A Great Quote!

For everyone doing cutting edge work, here is a great quote from a pioneer in rotary wing aircraft:

Every very radical research needs an eccentric person who, by a certain amount of freedom from convention is not too afraid to go far afield for solutions.

Gerard Herrick

Richard Whittle, “The Dream Machine: The Untold History of the Notorious V-22 Osprey,” Simon & Schuster Paperbacks, 2010, p. 20

# The 2017 Edition of Princeton Satellite Systems’ MATLAB Toolboxes is Now Available!

Version 2017.1 of Princeton Satellite Systems MATLAB toolbox suite is now available! Over 60 new functions were added and updates to dozens of existing functions were made to improve their performance and expand their applications.

In the Aircraft Control Toolbox we added an inlet loss function to compute losses due to shockwaves. Our Unscented Kalman Filter algorithm was updated.

We expanded our support for heliocentric missions. This includes functions to compute solar eclipses in heliocentric orbits, heliocentric sphere of influence, heliocentric trajectory plotting and thermal models for heliocentric spacecraft.

Several new component models were added for use with the CAD modeling functions. These included a liquid apogee Engine, curved tubes and triangular trusses.

We have added all new star identification functions. These are based on a pyramid star identification algorithm using four stars for a definitive match during lost-in-sky conditions. The algorithm provides reliable star identification with almost any star catalog and in any orientation. We have updated image processing algorithms for star centroid determination.

New attitude determination demos and algorithms were added for mixtures of different sensors, such as sun measurements, earth chords and magnetic field measurements. You can compare the performance of extended and Unscented Kalman Filters. A new second order guidance law was added for planetary and lunar landing that provides a simple and effective algorithm for landers.

# Asteroid Day

June 30 is Asteroid Day. Asteroid Day is a reminder that we need to protect the Earth from asteroids. We need both an early warning system and a means for deflecting asteroids. The B612 Foundation is working on an early warning system. Direct Fusion Drive, a nuclear fusion rocket engine technology under development jointly by Princeton Satellite Systems and the Princeton Plasma Physics Laboratory could provide the means to deflect asteroids that are on a course to collide with the earth. We published a paper in October 2013 on how this might be done

Direct Fusion Drive Rocket for Asteroid Deflection [PDF], J. Mueller, Y. Razin, S. Cohen, A. Glasser, et al, 33rd International Electric Propulsion Conference.

Samuel Cohen, inventor of the Princeton Field Reversed Configuration reactor that is the core of our engine, co-authored a paper on comet deflection.

We are currently supported by a DOE grant, two NASA STTRs and a NASA Phase II NIAC grant! For more information go to our nuclear fusion page.

# The New Space Age Conference

Charles Swanson of PPPL and Mike Paluszek of Princeton Satellite Systems attended the MIT New Space Age Conference at MIT on March 11. It was held on the 7th floor of building E52 at MIT.

Princeton Satellite Systems was a sponsor of the event. It was a great event! There were a number of interesting presentations including one on the history of the Iridium Program. Iridium was almost ready to deorbit the constellation when an investor cobbled together enough money to keep it flying and then found a new market in places without any cell phone service. They are now  launching Iridium-Next. After the disappearance of the Malaysian Flight 370, the airlines realized that they need to know the position of all planes in real-time. Iridium offered a hosted payload to do that and that payload is effectively funding the new satellites. The speaker showed us a image from their satellite showing the tracks of aircraft.

Professor Loeb gave an overview of the Starshot project to accelerate small sails to 20% of the speed of light. He discussed some of the challenges of the program. The speed was selected specifically so that the probes would reach Alpha-Centauri during the lifespan of the investigators.

Boeing gave a talk on composite structures. The speaker, Dr. Naveed Hussain, VP of Aeromechanics Technology, The Boeing Company, showed how established companies are innovating.

Spaceflight gave a talk on their launch services. We plan to work with them to launch our test satellites.

At lunch Charles and I sat with a group of students from Mechanical and Aerospace Engineering Department at Princeton University. We were joined by Mark Jernigan, Associate Director, NASA/JSC Human Health and Performance Directorate. We talked with him about the challenges of human spaceflight to Mars.

Charles and I were on the propulsion panel. Charles gave a spectacular overview of the plasma physics of our nuclear fusion engine. I filled in the DFD system details. We had a few questions from the audience.

Our 2017 extern, Eric Hinterman, gave a great talk on the oxygen from carbon dioxide project that will be tested on Mars. It would produce the oxidizer for return missions thus saving money. My wife, Marilyn, took pictures of the panel.

At the reception we were the only sponsor with a table display.

It was a great event! We look forward to attending next year!

# MIT Externs at Princeton Satellite Systems

Every year during MIT’s Independent Activities Period in January MIT students can apply for externships at alumni’s places of business. Externships last from one to four weeks. Over 300 undergraduate and graduate students participate each year. As part of the program, MIT also helps students find housing with alumni who live near the businesses sponsoring the externship. Externships are a great opportunity to learn about different types of career opportunities. Students apply in September and go through a competitive selection process run by the MIT Externship office.

This year Princeton Satellite Systems had two externs, Tingxao (Charlotte) Sun, a sophomore in Aeronautics and Astronautics and Eric Hinterman, a first year graduate student in Aeronautics and Astronautics. Eric started January 9th and Charlotte on the 16th after spending time on the west coast visiting aerospace companies as part of an MIT Aeronautics and Astronautics trip. Eric took a break during the externship to attend a meeting at JPL on an MIT project.

Both externs worked on our Direct Fusion Drive research program to develop a space nuclear fusion propulsion system. An artist’s conception is shown below.

This project is currently funded by NASA under a NIAC grant. Eric worked primarily on the Brayton cycle heat recovery system that turns waste energy from bremsstrahlung radiation, synchrotron radiation and heat from the plasma into power that drives the rotating magnetic field (RMF) heating system. He produced a complete design and sized the system. He also wrote several MATLAB functions to analyze the system. Charlotte worked on the design of the superconducting coil support structure making good use of her Unified Engineering course skills! Here is a picture of Charlotte and Eric in front of the Princeton Field Reversed Configuration Model 2 test machine (PFRC-2) at the Princeton Plasma Physics Laboratory. Dr. Samuel Cohen, inventor of PFRC, is showing them the machine.

Both Charlotte and Eric made important contributions to our project! We enjoyed having them at Princeton Satellite Systems and wish them the best of luck in their future endeavors!

# MATLAB Machine Learning Book is Now Available

Apress just published our new book, “MATLAB Machine Learning”

written by Michael Paluszek and Stephanie Thomas. The book covers a wide variety of topics related to machine learning including neural nets and decision trees. It also includes topics from automatic control including Kalman Filters and adaptive control. The book has many examples including autonomous driving, number identification and adaptive control of aircraft. Here is a view of a neural net tool included with the book.

Full source code is available. For more information go to MATLAB Machine Learning.

# Princeton Satellite Systems Awarded Nuclear Fusion Patent in Japan

Princeton Satellite Systems was awarded its first patent in Japan, “Method to produce high specific impulse and moderate thrust from a fusion-powered rocket engine”. This technology was licensed from Princeton University’s Princeton Plasma Physics Laboratory. It is for a compact, low-neutron, nuclear fusion reactor that can be used as a rocket engine or as a power generator. The reactor can be built in sizes from 1 to 10 MW. A typical robotic spacecraft would use two engines. A human mission to Mars or the outer planet might use six 5 MW engines.

Here is the Japanese patent certificate.

# US-Japan Compact Toroid Workshop 2016

Mike Paluszek of Princeton Systems, Sam Cohen of the Princeton Plasma Physics Laboratory and Charles Swanson also of PPPL attended the US – Japan Compact Toroid 2016 meeting in Irvine California this past August.

We presented papers related to Sam’s Princeton Field Reversed Configuration nuclear fusion reactor research program. Charles presented, “Extracting electron energy distributions from PFRC X-ray spectra,” Sam presented “Long pulse operation of the PFRC-2 device” and Mike presented, “Fusion-enabled Pluto orbiter and lander”.

Here are the workshop attendees.

It was fascinating to listen to all of the papers at the workshop! John Santarius, who has done cutting edge work on space propulsion and small fusion reactors presented his talk, “Aspects of Advanced Fuel FRC Fusion Reactors.” He gave a very informative overview of small fusion reactors and advanced fusion fuel technology. Thomas McGuire discussed the Lockheed Martin research on small reactors. There were several presentations by Tri-Alpha Energy scientists on their beam heated FRC.

We look forward to the next Compact Toroid Workshop!