MainPowerDistributionSystem

Virginia Tech RockSat-X 2026 Project.

[!IMPORTANT] Quick link to:

• Wallops Testing Procedure.
• Remove-Before-Flight Procedure.

Also check out the RSXVT2026 Wiki!

 

Mission Overview.

Our experiment aims to evaluate the use of optical navigation with Commercial-off-the-Shelf (COTS) products for use in spaceflight applications. To conduct the experiment, an autonomous attitude determination and control system (ADCS) employing an optical navigation system (ONS) will be designed to control a 1U CubeSat, codenamed Commercial Optical Navigation Satellite (CONSat).

The 2024 NASA Civil Space Shortfall Ranking lists 9 out of the top 30 shortfalls as limitations with autonomous deep space navigation. With recent advancements in computing and ML capabilities, optical navigation could revolutionize deep space navigation. Our team aims to address some of the challenges facing the space industry by designing a cost-effective ADCS that would rely primarily on conditions only available in deep space.

The CONSat vehicle's Optical Navigation System (ONS) has:

• OpenMV H7+.
• VN-100 IMU / AHRS.

The operating principle of the CONSat will be to:

1. Capture image and isolate target.
2. Perform LoS measurements to estimate attitude.
3. Blend LoS solution with IMU / AHRS solution.
4. Reorient spacecraft to align to target.

The target will be the Earth's horizon as seen at ~190 km apogee.

 

High-Level System Overview.

Deck-plate integrated experiment.

 

Top-down view of the deck-plate integrated experiment.

 

Weight of the deck-plate integrated experiment (13.935 pounds / 6.321 kilograms).

 

Center of gravity of the deck-plate integrated experiment.

 

The inside of the main electronics box enclosure.

 

CONSat vehicle.

 

The inside of the CONSat vehicle.

 

Labeled CAD model of the experiment.

 

Functional block diagram of the CONSat experiment.

 

Main Camera System.

The experiment has two Main Camera Systems: one placed before the ejection mechnism and one next to a Solarboard by the burn-wire mechanism.

Main Camera System demonstration.

 

The Main Camera System board has a single RGB LED.

 

The Main Camera System creates a binary blob file for each recording. Use cli.py parseVideo to convert the binary blob file into an MP4 video.

 

Debug Board.

The Debug Board has a display to indicate the status of subsystems from the perspective of the Main Flight Computer. When the experiment is powered on via GSE-1, the Debug Board will initialize and play the Nokia buzzer tune. The display will also periodically invert color; this is just to indicate that the Debug Board MCU is still running.

Debug board demonstration.

 

The Debug Board displays the following information.

If the Debug Board has not received the first debug packet from the Main Flight Computer yet, then the field values will either be ??? or nan to indicate this.

[!IMPORTANT] A known issue with the Debug Board's display is that it is not resettable. That is, if the Debug Board MCU has a communication issue with the display driver, there's a small possibility that the display ends up in a corrupted state. This may appear as the screen being darker, the resolution looking off, or is completely blank. The MCU has no way to fix this, but power-cycling will resolve this rare issue if it ever happens.

 

The debug board has four RGB LEDs.

[!IMPORTANT] If the Debug Board encounters an irrecoverable error, it'll panic and indicate this by flashing all LEDs red. The Debug Board should eventually reset itself and continue on as normal.

 

The debug board plays the following buzzer tunes.

To mute the buzzer, leave the header above the buzzer open. To enable the buzzer, have a jumper shorting two adjacent pins; which pins are shorted determines the volume of the buzzer.

 

The uSD card is optional to the operation of the Debug Board. The Debug Board uses LED D to indicate that it's successfully saving log data.

To load a uSD card, lift the connector lid up,
place the uSD card, and slide the lid down to secure it.

 

The Debug Board creates an ASCII text file with
the same information displayed on its screen.

 

Vehicle Flight Computer.

The following table details the corresponding buzzer tune and RGB LED behavior for when a Vehicle Flight Computer diagnostic is reported.

The three pin header on the Vehicle Flight Computer can be left open to mute the buzzer, otherwise short a pair of adjacent pins to determine the volume of the buzzer.

 

The Vehicle Flight Computer board also has an optional uSD card slot for log data.

The Vehicle Flight Computer creates an ASCII text file with information
like VN-100 IMU data, CVT results, current motor velocities, and so on.

 

 

OpenMV H7+.

The OpenMV H7+ has a single RGB LED.

Each toggle of the RGB LED represents an entire image being captured, processed, and transmitted to the Vehicle Flight Computer. Because JPEG image compression is used, if the OpenMV H7+'s camera lens is covered (e.g. by a finger), the blinking of the RGB LED will be much faster.

If the OpenMV H7+'s RGB LED is not blinking, then it's very likely the program is not running, but the Vehicle Flight Computer should reset the OpenMV H7+ eventually after a time-out period.

No other colors or behavior should be expected from the RGB LED or the OpenMV H7+ module as a whole.

 

Vehicle Power Distribution System.

The Vehicle Power Distribution System has LED indicators to be aware of.

The Vehicle Power Distribution System has three jumpers to be aware of.

First jumper on the left denoted with "M" as in "Motor Inhibit".
Second jumper in the middle denoted with "B" as in "Battery Inhibit".
Third jumper on the right denoted with "P" as in "Power".
Note that the third "Power" jumper should only have its
first left pin and the second right pin is broken off.

 

[!TIP] A quick way to turn off the vehicle is by using an Allen key to short the middle "B" jumper.

 

RF Verification.

During sequence testing and particularly GPS Roll-Out, it's critical to verify that RF systems are working as intended and to communicate this to NASA.

The easiest way to do this is to use the Debug Board. The screen will indicate if the Main Flight Computer is receiving RF data from the ESP32 and/or LoRa. If the Debug Board is loaded with a uSD card, the RF status will also be logged over time.

A more robust way to verify RF is to use the TinySA Spectrum Analyzer. There are two particular frequency bands of interest.

Configure the spectrum analyzer to observe these frequencies.

Spectrum analyzer demonstration.

 

You should see a reading similar the following figures:

Spectrum analyzer measurement for the ESP32 link.

Spectrum analyzer measurement for the LoRa link.

 

[!IMPORTANT] The measurements shown in the figures were taken with an RBW value of 200 Hz; this makes the measurement more accurate but at the cost of being extremely slow. It's probably more productive to use an auto RBW value so measurements can be done quickly. Just as long there is an expected peak within frequency bands, all is good.

The RF verification process and expectations should be roughly as follows:

1. Before the experiment is powered on via GSE-1, no RF transmission is detected within the frequency bands.

2. Shortly after the experiment is powered on via GSE-1, ESP32 and LoRa transmission can be seen within the frequency bands.

3. RF transmission is sustained for at least the duration of a full mission; if applicable, the RF transmission should still be sustained even if the vehicle has ejected or becomes undocked.

4. RF transmission is sustained even when main has powered off (i.e. GSE-1 deactived) as the vehicle will continue transmitting via battery power.

5. RF transmission is no longer detected once the vehicle has powered off (either by using the vehicle battery inhibit or through a docked reset).

 

Wallops Testing Procedure.

The following table summarizes the primary configurations needed to be set for tests done at Wallops.

To allow ejection ( :white_check_mark: ), ensure the mechanical inhibit in front of the ejection mechanism is removed.

To prevent ejection ( :x: ), ensure the mechanical inhibit is secured in front of the ejection mechanism.

To have TE-1, Main GSE-1, or Vehicle GSE-1 be enabled ( :white_check_mark: ), insert a screw into the corresponding electrical screw switch on the side of the ejection mechanism. Verify short-circuit with a multimeter.

To have TE-1, Main GSE-1, or Vehicle GSE-1 be disabled ( :x: ), ensure a screw is not inserted into the corresponding electrical screw switch. Verify open-circuit with a multimeter.

[!IMPORTANT] The experiment must be put into flight-ready configuration during vibration testing. This means all electrical screw switches should be enabled and no mechanical inhibit present. Any loose components such as external uSD cards and jumpers should be removed (see RBF procedures). Screws should be applied with blue Loctite.

It should also be noted that Wallops will only provide GSE-1 and there will be no TE-1 power during this vibration test (this also applies to GPS Roll-Out).

[!IMPORTANT] The purpose of the electrical screw switches for Main GSE-1 and Vehicle GSE-1 is for flexibility. In the event that we need to ensure that the main avionics and/or vehicle does not power on, we have these as a way to do so.

 

Remove-Before-Flight Procedure.

The following steps are to be carried out in order with minimal deviations after all final sequence tests are done.

[!IMPORTANT] Pre-RBF procedure checklist:

• Multimeter.
• Three fully charged EEMB LP653042 3.7V 820mAh batteries.
• Allen key kit.
• Red Loctite.
• Tweezers.
• Needle-nose pliers.
• Phillips screwdriver.

 

1. Take out vehicle.

Remove the ejection inhibit if still in place. The ejection inhibit will not be used again, so store it away in a secure location.

Take out the burn-wire mechanism in order to release the vehicle from the ejection mechanism. Place the burn-wire mechanism in a secure location.

Carefully undock vehicle and place it down on a table to be worked on.

 

2. Replace vehicle batteries.

Go to the side of the vehicle where the batteries are stored.

Side of the vehicle where the batteries are stored.

 

Take off the panel. Place the panel and screws in a secure location.

Panel that secured the vehicle's batteries removed.

 

Take out the old vehicle batteries. It is okay to tug on the cable to do so if excessive force is not used. Make sure to place the old vehicle batteries somewhere secure so it will not be confused with the new batteries.

Vehicle batteries removed.

 

Verify that the new batteries (EEMB LP653042 3.7V 820mAh) are fully charged.

A fully charged vehicle battery should have at least 4V.

 

Verify that the new batteries have a JST-XH plug of the correct polarity.

Note the plug polarity.

 

Put in the new vehicle batteries. The order in which the vehicle batteries are connected does not matter. Ensure the cables are well tucked to prevent them being crushed by the panel.

Vehicle batteries replaced.

 

Place and align the vehicle panel with the pillar's screw holes and verify that the battery cables will not be crushed.

Vehicle panel aligned on top but not yet screwed.

Battery cables tucked securely and not between the panel and pillar.

 

Apply red Loctite to the threads and reinsert screws to secure the panel.

Side of the vehicle where the batteries are stored.

 

3. Remove vehicle jumper inhibits.

Ensure the vehicle's jumpers for disabling motors, disabling batteries, and forcing vehicle power-on are all open-circuit as depicted below.

Vehicle jumpers in flight configuration.

 

4. Redock vehicle.

Reinsert vehicle into the ejection mechanism. Make certain that the vehicle is in the correct orientation. Verify that the vehicle interface connectors are aligned.

Put the previously removed burn-wire mechanism back onto the deck-plate to secure the vehicle in the ejection mechanism. Apply red Loctite to screws during this process.

Visually verify and test that the vehicle is well secured by the ejection mechanism and burn-wire rope.

 

5. Remove external uSD connector lids and jumpers.

To prevent vibration risks, the Vehicle Flight Computer and Debug Board should have the lid of their uSD connectors be taken off. The pin header for the buzzer should also be left as an open circuit.

Debug Board without uSD card connector lid and buzzer jumper.

 

Vehicle Flight Computer without uSD card connector lid.

 

Vehicle Flight Computer without buzzer jumper.
Tweezers might be needed.

 

6. Enable electrical screw switches.

Insert screws with red Loctite into the three electrical screw switches on the side of the ejection mechanism.

Verify connectivity of each electrical screw switch by testing continuity of the two pads.

 

7. Final checks.

[!IMPORTANT] Verify that the following has been done:

• New vehicle batteries has been put in.
• Red Loctite has been applied to the vehicle's panel on the battery side.
• Red Loctite has been applied to the burn-wire mechanism.
• Red Loctite has been applied to the electrical screw switches.
• Vehicle is well secured by the burn-wire rope and ejection mechanism as a whole.
• No loose components like uSD card connector lids or jumpers are in place.
• Electrical screw switches have the expected connectivity.

 

Burn-Wire Line Assembly.

These instructions describe how to fabricate the burnwire restraint lines using 1 mm braided line and two overhand loop knots.

The finished burnwire line should have:

• Two looped ends.
• Approximately 12.75 in finished length.
• ±0.5 inch allowable tolerance.

Required materials:

• Tape measure.
• Dorisea Extreme Braid, 300 lb, 1 mm.
• Good scissors or sharp knife.

Use an Overhand Loop Knot for both ends (video tutorial).

Overhand loop knot reference diagram.

 

1. Tie first loop.

Tie an overhand loop knot at the end of the line. Target loop length of approximately 1 inch. Leave a short tail after tightening the knot.

1 inch loop.

 

2. Measure length.

Using the tape measure, measure 13.5 inches from the tip of the loop. Mark this location with a marker.

[!IMPORTANT] Do NOT cut the line yet.

13.5 inch mark.

 

3. Fold the line.

Fold the line in half at the 13.5 inch mark. Ensure the marked location becomes the tip of the second loop.

Folded at mark.

 

4. Tie second loop.

Tie another overhand loop knot. Loop length should again be approximately 1 inch. Ensure the black mark is positioned at the tip of the loop before tightening.

End loop first step.

 

Completed end loop.

 

5. Cut from roll.

Cut the line free from the spool. Leave approximately 0.25 inch tail on the final knot.

Trimmed end loop.

 

6. Final inspection.

Verify the completed burnwire line length. Finished length of 12.75 ± 0.5 inches. Measure from loop tip to loop tip.

Completed burn-wire line.

 

12.75in length confirmation.

 

A completed burnwire line is acceptable if:

• Both loops are securely tied using overhand loop knots.
• Both loops are approximately 1 inch long.
• Knot tails are trimmed to approximately 0.25 inch.
• Final overall length is 12.75 ± 0.5 in.
• Knots are fully tightened and seated cleanly.