Hack Chat Transcript, Part 1

A event log for Open-Source Satellite Propulsion Hack Chat

Michael Bretti

lutetiumLutetium 12/11/2019 at 21:180 Comments

Hi everyone, welcome to the Hack Chat. Today we're excited to welcome Michael Bretti of Applied Ion Systems to the Hack Chat. He's literally building the future - open-source thrusters for DIY satellites that you'll be able to buy off-the-shelf someday!

Welcome Michael - can you tell us a little about how you got to this point?

Applied Ion Systems12:03 PM
Thanks Dan! Like Dan mentioned, I am currently leading development of open source propulsion for small satellites. As far as I am aware, this is really the first and only fully open source propulsion program out there. I have a small, modular high vacuum system for testing these systems. Details are archived on my website here:

Applied Ion Systems12:03 PM
Other media and references can be seen on twitter and Instagram as well:

Applied Ion Systems12:03 PM


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Applied Ion Systems12:04 PM
Currently, I have 2 thrusters slated for space this upcoming year with AMSAT-Spain's GENESIS PocketQubes

Applied Ion Systems12:04 PM
Lot's of new and exciting collaborations to come with others in the community though!

I was just going to ask when you expect to fly hardware. That's really exciting!

Applied Ion Systems12:05 PM
I have primarily been focusing on pulsed plasma thrusters, but have recently switched gears for more advanced systems such as ionic liquid ion source (ILIS) thrusters

Applied Ion Systems12:05 PM
Yeah, it should be sometime early 2020, assuming they pass integration and environmental testing

RichardCollins12:06 PM
What is the primary power source?

Applied Ion Systems12:07 PM
For the PPT that is being launched, the AIS-gPPT3-1C, it is designed to run from 3.3V to 4V power from the PQ battery bus

Nicolas Tremblay joined  the room.12:07 PM

Applied Ion Systems12:07 PM
the circuit boosts this to about 1kV for the primary bank, and a pulse transformer provides a 10kv trigger pulse for ignition

Applied Ion Systems12:07 PM
Ill post the circuit here

RichardCollins12:07 PM
Solar panels feeding the batteries?

Applied Ion Systems12:08 PM

Applied Ion Systems12:08 PM

Nardax joined  the room.12:08 PM

RichardCollins12:08 PM
Can private groups use radio-isotopes yet?

Jake Moomaw joined  the room.12:09 PM

Applied Ion Systems12:09 PM
I highly doubt it, dealing with any radioactive sources would be a nightmare to deal with

Applied Ion Systems12:10 PM
No need though, the groups out there are using quite high efficiency cells, and lots of exciting development for deployable arrays to really boost power capabiities

Jake Moomaw12:10 PM
What type of fuel are you looking to use with the ILIS engine?

Plus I think the government has a pretty tight lid on plutonium-238 supply. They've got pretty much the world supply sitting in the RTGs that will go to Mars with the Mars Rover mission.

Applied Ion Systems12:11 PM
I will be using standard EMI-BF4, a popular room temperature ionic molten salt. Very well studied and understood, and highly stable

RichardCollins12:12 PM
Pardon me for interrupting. What kinds of packages are people talking about sending?

yashelite12:12 PM
Weren't plasma thrusters first used in 1964? What kind of innovation or improvement has this now?

Applied Ion Systems12:13 PM
Electric propulsion (EP) in general dates back to the 60s. The thrusters built back then were monstrous though, huge beasts 10s to 100s of kW of power. The key difficulty in EP has been scaling down.

Applied Ion Systems12:13 PM
Curently, there is no EP solution on the market for PQs

Applied Ion Systems12:14 PM
there is a lot of competition at the cubesat level, but it is still very costly

Applied Ion Systems12:15 PM
My goal is to radically bring down price, and scale to a level that is very accessible to low funded groups, as well as provide resources on these thrusters showing how I go through designing and building them, from concept to deployable solution

yashelite12:15 PM

Applied Ion Systems12:15 PM
EP right now is highly protected, open source EP is unheard of in industry

Applied Ion Systems12:15 PM
lots of details in academia, but published data or experiments is not quite the same as open source

Have you gotten any pushback from the industry for disrupting things?

Applied Ion Systems12:16 PM
and most of it is just experimental benchtop systems

Jake Moomaw12:16 PM
How far along are you with the ILIS thruster?

Applied Ion Systems12:16 PM
No not yet! But I am sure once i get the ILIS thruster running, I may make some enemies

Applied Ion Systems12:17 PM
I have the design just about ready to go for first prototypes, just waiting on machining quote for the porous glass emitter

Applied Ion Systems12:17 PM
hopefully I'll have that quote today or tomorrow, which is the key driving cost for this thruster at this point

yashelite12:17 PM
Be sure to patent your work.

Applied Ion Systems12:18 PM
since it relies on standard CNC vs traditional micromachining, it allows ILIS thrusters to actually be accessible at this level

Applied Ion Systems12:18 PM
I've heard everyone saying to patent stuff

Applied Ion Systems12:18 PM
cant afford patents lol

You seem to have devoted a lot of resources to the solid-fuel thrusters. Why the switch to liquid fuel?

Morning.Star12:18 PM
It will cost you dude.

Applied Ion Systems12:18 PM
my budget is practiclly non-existant

Patents are just permission slips to be sued.

yashelite12:19 PM
That's a nice way of putting it.

yashelite12:20 PM
You can always start a Gofundme campaign or use crowdfunding.

Applied Ion Systems12:20 PM
While solid PPT thrusters are great leaning tools, the physics just don't allow it to scale for the thrust needed at the power restrictions of a PQ. Hpwever, ILIS has extraordinary potential, in that it can provide very high thrust to power ratios at very high efficiency and ISP. This type of thruster also eliminates the need for any pressurized feed, valves, active flow control, heaters, or electron emitting neutralizer

Morning.Star12:20 PM
Yeah, but its the only protection you have. Licensing, especially public licensing isnt worth a damn. Just sayin lol.

toani12:20 PM
Hi! Excuse me. I am new in the topic. How many key pieces is a thruster comprised of?

Patents: If it is published anywhere, then it is not patentable anymore. Otherwise, you can afford $120 for the provisional that is good for a year, enough time to get some funding for the whole thing including patents. But then it is not open source anymore ^^

Now THAT'S a Kickstarter I could back!

toani12:20 PM

rizoid joined  the room.12:21 PM

Applied Ion Systems12:21 PM
@toani it depends on the thruster and the scale, it's hard to say unless we are talking about a specific system

rizoid12:21 PM

Applied Ion Systems12:21 PM
from what I have seen full tech patents in the US can average around $20k

toani12:22 PM
I see thanks

Patent == patent attornies == billable hours

Applied Ion Systems12:23 PM
As an individual doing this out of pocket in my free time, patents are out of the question

Morning.Star12:23 PM
Business is business.

Anyway, rocket science ;-)

yashelite12:23 PM
Can the ILIS thrusters be used in heavy spaceships? Like say Falcon 9 which uses liquid oxygen as its primary fuel?

Applied Ion Systems12:24 PM
but I will say that doing this type of work at a highly restricted budget has pushed me to think way outside the box and really simplify these systems

Applied Ion Systems12:24 PM
@yashelite how do you define heavy?

Nicolas Tremblay12:24 PM
I would continue with the open source and publish it at a few places to make sure your rights are recognized

Applied Ion Systems12:24 PM
like very large satellites?

Ethan Waldo12:25 PM
Have you done any RF and optical evaluation yet? These types of electric propulsion systems are effectively spark gap transmitters that emit damped radio waves (bad) as well as ultra-violet emissions which can interfere with ground-based astronomical observations. To my knowledge these have only flown with experimental designation where these concerns could be coordinated accordingly.

Applied Ion Systems12:25 PM
@Nicolas Tremblay yeah, at this point I publish details and updates regularly on Twitter, and archive stuff on the website

yashelite12:26 PM
By heavy I mean spaceships which can carry a substantial amount of payload.

Applied Ion Systems12:27 PM
@Ethan Waldo for ILIS no need - as a DC thruster it outputs no RF interference, and optically the emission is very light to negligeable. The PPTs can generate a bunch of noise due to the pulse, but they are the oldest and some of the most commonly flown and tested EP

Applied Ion Systems12:27 PM
PPTs especially due to their extreme simplicity, low cost, and ruggedness

Ethan Waldo12:28 PM
Not the PPT, but the actual sparks between anode and cathode is what generates bad emissions

Applied Ion Systems12:28 PM
@yashelite technically it could scale, but I think at a certain point the big ion or plasma engines would take over - efficiency and performance goes up with these at higher power levels, and ILIS is not at the point yet for massive array scaling

Ethan Waldo12:29 PM
Just like a spark plug

Applied Ion Systems12:29 PM
@Ethan Waldo the PPT produces a spark - one for ignition, and the main plasma pulse. If the ILIS thruster sparks, then it can damage the thruster lol.

So, orbital dynamics newbie here, maybe a dumb question. How do you get the thrust from one of these pointed in the right direction? IOW, how are PocketQubes able to control their attitude relative to the direction of orbit?

Applied Ion Systems12:30 PM
The main discharge for a PPT can range from several hundreds to thousands of amps in a few uS

Applied Ion Systems12:31 PM
@Dan Maloney great question! That's another task that needs to be addressed at the PQ level - attitude control. It's either you have none and tumble freely, have passive means like magnetorquers, or active control like reaction wheels

Ethan Waldo12:31 PM
yes, I would highly recommend an evaluation and publish results

Applied Ion Systems12:31 PM
Most PQs have some form of passive control

Applied Ion Systems12:31 PM
active control is a challenge due to power and size constraints, but there are a few out there actively working on this

I think I saw something about PQs having permanent magnets on board to keep them aligned to the earth's magnetic field. Is that magnetotorque?

Jonny Wester12:33 PM
Hi, Jonny from Sweden in China.

How do you switch a couple of thousands of Amps?

Applied Ion Systems12:33 PM
So for the GENESIS satellite, the plan will be firing when it is passively aligned in the correct direction. So a period of about 15 minutes every 90 minute orbit

Applied Ion Systems12:33 PM
@Dan Maloney yes that's correct

Applied Ion Systems12:35 PM
@Jonny Wester no need to switch that current. The trigger pulse is a low current, high voltage pulse that ablates an initial amount of fuel between the cathode and igniter. This inital ionized fuel then allows for a conducting path to be formed between the anode and cathode, which a larger cap bank is charged and connected to. This energy gets directly dumped in, ablating more fuel, ionizing, and accelerating it as the plasma you see out the end.

Applied Ion Systems12:36 PM
So it acts essentially as a triggered spark gap switch

Applied Ion Systems12:36 PM
albeit a bit different

Applied Ion Systems12:36 PM
(since triggered gaps don't rely on ablated ionized fuel for firing)

Ethan Waldo12:37 PM
and the plasma only works in a high enough vacuum :)

Applied Ion Systems12:37 PM
here is a video of the thruster firing:

Applied Ion Systems12:37 PM


Applied Ion Systems12:38 PM
yeah, these thrusters require vacuum to operate correctly

Jonny Wester12:38 PM
Capacitor banks, I have had dreams about this!!! Now they are real. So, creating plasma as a thruster.

Applied Ion Systems12:38 PM
differnet types of thrusters have different types of vacuum testeing requirements

RichardCollins12:38 PM
You might have to find several projects in development phase, then offer to design their propulsion subsytem. Ask for attitude data and methods for controlling orientation. If you can have multiple small units of yours - for each axis or primary direction, then you can write the control algorithms and model them.

The earliest plasma experiments were modified spark gaps where the ionization was provided by external sources - beta or alpha emitters, uv sources, electron beams, smaller ion and electron sources.

Applied Ion Systems12:39 PM
Yeah, one of my main specialties, pulsed power, deals a lot with this in history. Dumping huge banks of energy into plasma or pulsed particle beam systems

Applied Ion Systems12:39 PM
Dates very early on back to the 50s

Jonny Wester12:40 PM
Yes, massive pulsed capacitor banks, and "spark plugs", genious!

yashelite12:40 PM
That was the golden age of space exploration and propulsion systems.

Bob joined  the room.12:41 PM

Applied Ion Systems12:41 PM
@RichardCollins yeah, I'm actively collaborating with several groups

Jonny Wester12:41 PM
Now there are supercapacitors.

Applied Ion Systems12:41 PM
Actually, spark gap switches are still to king of switching. Some of the state of the art stuff is really wild

Applied Ion Systems12:41 PM
at least in pulsed power they are a very dominant form of switching

Bob12:42 PM
What kind of facilities/equipment did it take to get to this stage? Have you done it all in your own shop / rented time / outsourced?

Jonny Wester12:43 PM
It would interfere seriously with the electronics in the close vincinity controlling it. How to protect the control circuitry from thus massive EMC?

Applied Ion Systems12:46 PM
@Bob the biggest requirement is high vacuum. This was all designed and optimied from scratch with available surplus. In the US at least, it is very easy to get vacuum equipemnt on ebay, however there is a whole group of vacuum enthusiasts around the world. if you are interested, I would check out the Vacuum Hackers discord chat. Fantastic place with tons of awesome high vacuum projects around the world. A lot of the design resources were free that I used - fusion 360 for CAD and thermal (CAD is a must for planning!), and a free vacuum simulation software from CERN called MOLFLOW+ (but this is highly overkill for most amaetur vacuum work). Really, it comes down to a lot of prep. I spent a year prior collecting resources, data, and getting preppped before designing my system so it would just work when switched on.

Ziya Yıldız joined  the room.12:46 PM

Applied Ion Systems12:47 PM
For vacuum, I can reach in the 10^-6 torr range. I optimized my system for high pumping speed based off of 6" conflat hardware, which is pretty available, and not too bad in cost used, and is a good balance between size and cost for what I need

Bob12:47 PM
That is really impressive! Helpful information, too. Thank you. I just spotted this project when it was featured on HaD but I'm pretty much glued to it now.