About Michael Paluszek

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.

Animation of a Nanosat Near the ISS

A popular way of launching a small satellite is to bring it up on an International Space Station resupply mission. The Spacecraft Control Toolbox has functions to help you animate the orbit of your spacecraft near the ISS. A function, ISSOrbit, generates the orbital elements for the ISS. ISSOrbit generates Keplerian Elements from the latest 2-line elements. We use the function CoplanarOrbit to create an orbit 50 m below the ISS. There are no disturbances and the gravity model is for a point mass Earth.

DrawSpacecraft.m is a function that will draw any number of spacecraft in the viewer. This is the ISS and our, very small, NanoSatellite. The MATLAB camera controls allow you to zoom in or rotate the view. The view is with respect to the first satellite entered in the argument list, which in this case is the nano satellite.

DrawSpacecraft also does animation and will create an avi file. You can see the animation on our YouTube Channel or by clicking the video below. We converted the avi file to an mp4 file using a movie converter.

The script is an m-file that you can download, just to view, here.

You won’t be able to run the script without the rest of the toolbox. It shows how you can easily create animations.

Going to Mars with Direct Fusion Drive

We developed a round trip mission to Mars using Direct Fusion Drive. Key parameters are:

  • Specific power of 1.2 kW/kg
  • Exhaust velocity of 110 km/s
  • 40 MW engine
  • Payload of 55 MT out, 40 MT return
  • Outward leg 128 days
  • Inward leg 110 days
  • Stay on Mars 650 days

The following plot shows the trajectory. Some additional time would be needed to enter and exit the Mars and Earth’s orbit. That could be shortened by using a nuclear thermal engine tug.

The payload is based on the NASA Deep Space Habitat. It could be replaced by a less massive habitat and a lander. Two spacecraft, one including a lander, is another possibility. A dual spacecraft mission would enhance safety.

This mission plan has the DFD decelerating the spacecraft and going into Mars orbit. Some time could be saved using aerodynamic braking. The mass of the aeroshell would need to be included as part of the “engine” mass.

This analysis was done using the Spacecraft Control Toolbox http://www.psatellite.com/products/sct/

Covid-19

Many of you are working at home now due to social distancing rules.  We are ready to support you!  

  • Site licenses for all PSS toolboxes, including Academic and Cubesat, apply to people working at home. You can have your own copy on your computer.
  • We provide email and phone support to all customers. Call or email us anytime. We are generally available from 9 am to 11pm U.S. Eastern Time.
  • We can help you use the functions and scripts in the toolboxes and even help you customize the toolboxes for your current projects.
  • We can set up a Google Meet or Skype session if you want more interactive support
  • If you would like to get the latest versions of the toolbox, 2019.1 please email kcenci@psatellite.com.
  • We have many new functions and demos, including slosh models and reliability tools in 2020.1. If you intend to renew, and need some of these now, we can supply them in advance.

Please let us know if there are any other ways we can help keep your projects moving.  

Damping Nutation

It may from time to time necessary to damp nutation with thrusters on a momentum bias spacecraft. For example, nutation can happen when you transition from stationkeeping mode, which uses thrusters, to normal mode, in which you use low control authority actuators, such as magnetic torquers, for control.

We’ve written a script that simulation a momentum bias spacecraft. Let’s show the results.

The spacecraft body rate is 0.01 rad/s. This is much greater than you will ever see on your own spacecraft. The peak roll angle is about 18 degrees! The last plot shows the thruster control. In this simulation we don’t apply any control so the line is flat.

All you need is one thruster pulse, properly timed, to drive the x angular rate to zero. You must time it properly so as not to not leave a roll error. What we do is measure the peak angular rate, compute the pulsewidth needed to drive the rate to zero, and turn on the thruster when the roll angle is zero and the nutation rate is at its peak with the appropriate sign. The following plot shows the results.

The results aren’t perfect, as they would not be operationally. We did both simulations with the same Spacecraft Control Toolbox http://www.psatellite.com/products/sct/ script. This is a link to the m-file, saved as a zip file.

You won’t be able to run this without our toolboxes but you can see how we implemented “manual” nutation control. This script, and the new function RHSGyrostat.m will be available in SCT 2020.1 coming soon!

Toolboxes 2019.1 Now Available

Over 100 new functions were added or had major updates in Version 2019.1. Improvements were made to dozens of existing functions to improve their performance and expand their applications. Built-in demos were added to many functions to make them easier to use in your applications

In the Aircraft Control Toolbox, we added new tools for aircraft simulation. This includes a model builder allowing you to create mass and aerodynamic models from a CAD model that you load from in a Wavefront OBJ format. The model builder GUI is shown below. This  tool is matched with a new 6 degree of freedom aircraft simulation with an easier-to-use model viewer, shown under the GUI. The simulation lets you plug in your own aerodynamics and engine models, use the built-in defaults or other models from the toolbox.

The Spacecraft Control Toolbox has many new features. For example, you can now create cross-scale constellations and control them, or any other constellation, using control laws recently developed at PSS and presented at IWSCFF in 2019. A cross-scale constellation is shown below under active control.

We added the Fusion Toolbox for the development of nuclear fusion reactors. This function includes physics models, reactor models, thermal models and many other tools.  Both core reactor and balance of plant functions are included. 

The below shows a plot from one of the nuclear fusion tools which finds the fusion reaction rate for the aneutronic Deuterium-Helium3 fuel cycle as a function of ion temperature.

Artemis: From Gateway to Low Lunar Orbit

One concept Gateway may be in a polar orbit with an apolune of 70,000 km and perilune of 3,000 km. One concept is for the lander and Orion to meet at Gateway. Our alternative is for Artemis to stay in a low lunar orbit and be met there by Orion, the cargo transfer vehicle and the tanker. There are many orbit maneuver sequences that will get us from Gateway to our 15 km altitude orbit. A simple one is shown below. We first lower apogee to 3,000 km we then do a Hohmann transfer from the 3,000 km orbit to the 1753 km orbit (that is 15 km altitude). The maneuver to lower apogee is shown below.

The delta-v for the first maneuver is 0.49 km/s and for the Hohmann transfer is 0.39 km/s.

While in low lunar orbit in between landings the lunar lander will do high resolution photo surveys of the surface. These will be used to train the neural network for landing navigation.

Artemis: NASA RFP for Lunar Landers

NASA recently released a request for proposal for a lunar lander with a due date of November 1.

https://www.nasa.gov/feature/fast-track-to-the-moon-nasa-opens-call-for-artemis-lunar-landers

NASA would like a crew to land on the moon by 2024.

We didn’t have time to write a proposal, but here is our design. We propose a single stage vehicle, that can land from and return to a 15 km circular orbit. It uses 2 Blue Origins BE-3U engines that use cryogenic hydrogen and oxygen. An Orion capsule houses the astronauts. The Orion would take astronauts to and from Gateway and to and from the Earth. Lockheed Martin is building the Orion spacecraft. The European Space Agency is building the service module. A separate transport would bring fuel and payload to the lander. In the future, the lander could be refueled from lunar water.

The dimensions are in meters. The Orion is shown below. We purchased the model from https://hum3d.com.

The landing gear were scaled from the Apollo Lunar module.

It is interesting to compare its size with the Apollo Lunar Module. The Artemis is designed to fit into the 10 m SLS fairing. This a fully reusable lunar vehicle that can be refueled. It is designed for a long-term, sustainable, lunar base.

We use two toroidal hydrogen tanks and two spherical oxygen tanks. The cylinder on the outside is the solar array producing 34 kW of power. Of course, numerous details are omitted. We developed this model using our Spacecraft Control Toolbox. The design script will be available in the Spacecraft Control Toolbox Version 2019.1 due in mid-November.

Other elements of the lander were designed for different purposes. The GN&C system is based on our Army Precision Attitude Control System.

Our control system is based on a robotic lander we designed some time ago. We have full C++ code for the control and guidance system.

The architecture for Earth/Moon transportation system is shown below. Eventually, a Direct Fusion Drive freighter would be the main way of moving cargo between Earth orbit, lunar orbit and Gateway. The lander would remain in lunar orbit. Humans would go to the moon using fast orbital transfer, much like during Apollo.

Our next blog post will show how we get from Gateway to and from our 15 km starting orbit. A subsequent post will demonstrate our lunar landing guidance that uses a neural network for navigation based on images of the surface. Using it for landing would require higher resolution images than we have today, but short of building a lunar GPS system, it might be more cost-effective to have a satellite assembling images from low lunar orbit.

We will also update this blog post from time to time. Stay tuned!

IWSCFF 2019

I attended the 2019 International Workshop on Satellite Constellations and Formation Flying at the University of Strathclyde in Glasgow, Scotland. https://www.strath.ac.uk/engineering/iwscff/ It was a very interesting and enjoyable conference. The papers included a mix of papers from faculty, students and engineers in industry. Authors were from around in the world including Bangladesh, Brazil, Japan, China, Europe, Canada and the United States. Topics included control, orbit determination, constellation design and even the legal aspects of space operations.

Keynote speakers included Professor Simone d’Amico who talked about the work done in Stanford’s laboratories, Prof. Moriba Jah, who discussed large constellations and Dr. Timothy Maclay of OneWeb who discussed large commercial constellations such as the soon to fly OneWeb constellation.

Three students were awarded cash prizes for their papers. All of the student papers were good so it must have been a difficult decision for the judges.

My paper on cluster control was the first paper of the meeting. Other control papers focused on orbit estimation, use of environmental forces for control and even using electrostatic actuators.

The workshop reception was at the Glasgow City Chambers that has the largest marble staircase in Western Europe.

The conference dinner was the Glasgow Science Centre. Dinner was preceded by a planetarium show. After dinner, the attendees could wander around the museum that included many fun interactive exhibits.

Glasgow is a great city!

The Kelvingrove Art Gallery and Museum https://www.glasgowlife.org.uk/museums/venues/kelvingrove-art-gallery-and-museum is a fabulous museum. All the museums in Glasgow are free. Shown below is an exhibit at Kelvingrove related to the meeting.

The weather was nice with just a bit of rain. We went to many good restaurants including “The Buttery”, the Chippery for fish and chips and Chakoo for Indian food.

We plan to attend IWSCFF in the future and hope to return to Scotland for another visit!

Mr. Fusion (8 Wheeler)

A famous scene in “Back to the Future” is when Doc returns from the future and refuels his “Mr. Fusion” generator mounted on his DeLorean:

https://www.youtube.com/watch?v=ptlhgFaB89Y

PFRC is a little too big for a DeLorean but not for a U.S. Army Heavy Expanded Mobility Tactical Truck (HEMTT).

There is a version of the HEMTT that uses Oskhosh’s ProPulse diesel-electric hybrid system with ultra capacitors for energy storage. Electric motors drive the wheels.

https://oshkoshdefense.com/engineering-solutions/propulse/

A PFRC mounted on an HEMTT would provide electric power directly to the ProPulse system. The diesel might only by used to start up the fusion reactor. In effect we would have a 8 wheeler Mr. Fusion!