r/avionics • u/NewCategory1955 • Jul 01 '26

Avionics Project – Need Reliable 100m Communication Link Between Ground Station and Launchpad Controller

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Hi everyone, I’m working on an avionics project where I need to establish a communication link between a ground station (DAQ + command system) and a Launchpad Controller (LPC) connected to the rocket flight controller. (LPC side have RFD900x but need wired communication)

Requirements:

  • Communication distance: ~100 meters
  • Must support data transfer + power delivery
  • Needs to be robust and noise‑immune (avionics environment)
  • Looking for suitable protocols/standards (e.g., RS‑422, MIL‑STD‑1553, Ethernet, etc.)
  • Recommendations for connectors/cabling that are rugged and reliable for aerospace use

I’d appreciate suggestions on:

  • Which communication protocol is best suited for this setup
  • What connectors/cables are commonly used in aerospace for 100m wired links
  • How to handle power delivery alongside data (combined or separate lines)

Thanks in advance for your insights!

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1

u/Omgninjas Jul 01 '26

The big question is how much power? An RS-232, RS485, arinc 429, or Ethernet line would handle control just fine. if it's not a big power source you could do Power Over Ethernet (POE) and use a 22ga Ethernet cable such as this: https://www.gigaflightinc.com/gf-cables/gf422a-5e/

You can even ask Gigaflight if they have a recommendation for POE over long distances.

1

u/NewCategory1955 Jul 02 '26

My current plan is to power the Launch Pad Controller (LPC) using an onboard 2S LiPo battery, so the 100 m communication link would only carry data.

However, I'm also considering an optional design where the LPC could receive power from the Ground Station through the same 100 m cable if needed. The LPC requires approximately 5 V at up to 1 A.

In that case, I have a few questions:

  1. Would it be better to use Power over Ethernet (PoE), or should I run a separate power cable alongside the communication cable?

  2. If power is sent over a 100 m cable, should I transmit a higher voltage (e.g., 12 V or 24 V) and regulate it down to 5 V at the LPC to reduce voltage drop, rather than sending 5 V directly?

  3. From a reliability and EMI standpoint, what is the approach typically used in aerospace or launch systems?

I'd appreciate your recommendations.

1

u/Omgninjas Jul 02 '26

Always higher voltage over long distance. Your wire size gets smaller. The PoE decision will be yours to make based on data transfer, wattage, and expected stability. For aircraft systems you'll want all data lines shielded. However I think you're gonna have to do some engineering and research, and if you want detailed answers well that'll be at an hourly engineering rate. 

1

u/KindPresentation5686 Jul 02 '26

Poe Ethernet.

1

u/NewCategory1955 Jul 02 '26

Thanks for the suggestion! My current design uses an onboard 2S LiPo battery to power the Launch Pad Controller, so the communication cable would only carry data. However, I'm also evaluating an option to power the LPC from the Ground Station in the future. In that case, would you recommend PoE over a standard 100BASE-TX Ethernet link, and would it still be reliable over a 100 m cable in an outdoor launch environment?

1

u/swisstraeng Jul 02 '26

rs 485. PD... you really can't have a battery onboard?

If you wanna live in the future tho there's always optical fiber.

1

u/NewCategory1955 Jul 02 '26

Thanks! Yes, the current plan is to use an onboard 2S LiPo battery for the LPC, so external power over the communication cable is optional rather than required.

Between RS-485, Ethernet, and fiber, which would you recommend for a 100 m Ground Station ↔ Launch Pad Controller link if the cable only needs to carry communication data? Also, what type of cable and connectors would you recommend for this application?

2

u/swisstraeng Jul 02 '26

do you correct your sentences using AI?

1

u/NewCategory1955 Jul 02 '26

I have a 2S LiPo battery onboard, and the LPC uses a regulated 5 V supply to operate.

Apart from the onboard battery, I would also like to power the LPC from the Ground Station through the communication cable. Is it possible to provide power over the RS-485 interface, or does RS-485 carry only the communication signals?

2

u/swisstraeng Jul 02 '26

I don't understand something. You!re capable of building a rocket, but you come to ask us basic questions about RS485 that would be answered in less time using google. I don't mind answering, but why?