Question: Dynamic Voltage in NOS3/42, but Fixed Telemetry & No Component Power Draw

[roypyp]

Hello,

I am running the NOS3 simulation framework connected to the '42' dynamics simulator on a Raspberry Pi 5. I have a few questions to understand the behavior I'm seeing and would appreciate any guidance.

1. Investigating Subsystem Interaction:
   My simulation shows a dynamic battery voltage, which seems to confirm the connection to the '42' simulator is working. However, when I command a power-consuming component to activate (using a reaction wheel as an example), I see no corresponding change in the battery voltage.
   To make this work, is the general approach to define the power consumption model for each individual component directly within the '42' input files?

2. Understanding Fixed Telemetry:
   Even though the main battery voltage is dynamic, many other values in the EPS telemetry packet (like BATT_TEMPERATURE, SA_VOLTAGE, and all the switch currents) appear to be fixed. If the dynamic voltage proves the link to '42' is live, why would these other values be static? Does this also point to an incomplete thermal or solar model in our '42' configuration?

3. Raspberry Pi Specifics:
   Finally, are there any known issues or special configuration changes required when running the full NOS3 stack and the '42' simulator on a Raspberry Pi 5?

Thank you for your help and clarification.

[zlynch2]

Hi @roypyp, Ill answer you questions detailed by number below.

1. If you want to enable a powerdraw in NOS3 with the EPS, I would refer to the low power scenario defined here: https://nos3.readthedocs.io/en/latest/Scenario_Low_Power.html

There is a switch that you may need to toggle which could help with power consumption/usage with the nos3 eps. It is a good example of how to put the spacecraft into a high power consumption mode, and watch the telemetry values graph over time.

2. The telemetry values are simply pulled in from 42. ultimately, the eps sim is responsible for writing/reading values for NOS3 to 42. So I would start by looking at the sim for the EPS component. If your question is more how 42 can simulate I would encourage you to reach out to eric stoneking, who is the 42 creator. feel free to create an issue here https://github.com/ericstoneking/42.

3. Unfortunately, the NOS3 team doesnt have a lot of experience with running nos3 on a rPI, but we do have an arm64 container which is pulled in during the make prep stage. So I would be curious in your efforts to see how that goes, I would also check out the ci_launch make target in NOS3 as I think this launches everything in headless mode. which may be a path forward for running on the rPI. (just thinking off the top of my head).

I am curious if you are using the EPS sim out of the box from NOS3 or if you are running a modified version. Either way I think your goal is to simulate battery draw and you would like to see the values change accordingly.

let me know, and I hope this gives you some direction. Thanks!

[roypyp]

Hi, thanks for the reply @zlynch2
I am using the generic EPS out of the box.
One question:

In the simulator, does activating subsystems (reaction wheel, radio TX, heaters, etc.) actually change the simulated EPS power readings (voltage/current)?

I’m trying to understand whether the simulation models each subsystem's power draw, or if the EPS values remain constant regardless of subsystem activity.

I will try to do what you said with the rPI. I ran NOS3 on it, but the CPU is at 100% utilization, so it's slow.
Thanks!

[zlynch2]

The values should change, again I would refer to the low power scenario. here you will see how you can put the spacecraft in a power draw state/low power. It does take sometime depending on how the spacecraft is configured and if its sun pointing or not