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After reading the answers to:

I'm wondering which direction the Neumann drive will point, and what the maximum thrust it could potentially apply to the ISS. I realize this is primarily for testing the engine, but it reminds me that at one point there was an interest in installing VASMR on the ISS to altitude recovery. In this case this is just a test, but test or not, it will produce thrust and torque on the ISS that will be detectible as changes in orbital parameters and attitude.

For more on VASMR and the ISS see:

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  • $\begingroup$ It will be interesting to see. Apparently the payload is only 30 kg. I'm guessing it will be solely experimental in nature. $\endgroup$ – Organic Marble May 11 '18 at 13:08
  • $\begingroup$ @OrganicMarble it can't avoid being propulsive in nature as well, and they'll have to run it for thousands of hours at some point... $\endgroup$ – uhoh May 11 '18 at 14:07
  • $\begingroup$ Of course it could. Look up non-propulsive vent. $\endgroup$ – Organic Marble May 11 '18 at 14:26
  • $\begingroup$ @OrganicMarble I've just asked What is a non-propulsive vent? $\endgroup$ – uhoh May 11 '18 at 15:02
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The second part of the question is easier to answer; Neumann's thesis is available to download from the Uni. of Sydney's library via https://ses.library.usyd.edu.au/handle/2123/13810 and chapter six gives impulse and thrust results for the 11 different fuels tested. The max thrust from any of the fuels is a bit over 6N, and the max impulse from any of the pulses is around 1.5mN.s, as per table 6.2. While this is a fair amount of thrust from an electric thruster, bear in mind that this is the average thrust during a pulse that is only a few hundred microseconds long. If you want more time-averaged thrust, you'd want more pulses per second, which will require more electrical power and thermal management.

As for what direction the thruster will point, I'm certain that hard information on that is subject to confidentiality agreements; this is how the world works, at least until something progresses far enough along for press releases. The Airbus Bartolomeo website, at http://www.airbus.com/space/human-spaceflight/bartolomeo.html , indicates that the payload modules will hang off the Colombo module in the ram direction, being the direction "forwards" along the orbital path. Beyond that, we can only speculate as to the actual exhaust vector.

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  • $\begingroup$ Thank you for this excellent and well-sourced answer! I took a quick look at the thesis and the highest repetition rate I found was 4 Hz, so at an impulse of 1.5 mN s per pulse I can imagine that the testing will not result in substantial overall thrust compared to the mass and moment of inertia of the ISS, therefore the other part of the question (direction) doesn't really matter, and this is really a complete answer to what I was trying to find out. $\endgroup$ – uhoh May 15 '18 at 5:49
  • $\begingroup$ I wonder if testing has begun yet? If so, there may be more information available now. $\endgroup$ – uhoh Feb 10 at 11:26
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The Neumann Space site doesn't contain that info at the moment. They've tested their thruster with various fuels for wildly varying Isp. The main constraint will be the power budget. A 100 kg payload for Bartolomeo gets 250W max - which isn't much for an ion thruster.

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    $\begingroup$ I wonder if testing has begun yet? If so, there may be more information available now. $\endgroup$ – uhoh Feb 10 at 11:27

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