Project Horus Member Payload Launch Program

Program Aim

Encourage experimentation and technical development amongst club members in the area of high-altitude balloon payload development.


Various small payloads, about to be launched into the stratosphere!


Do you have a payload idea you would like launched under a high-altitude balloon? Now’s your chance! This program gives you the opportunity to build and launch your payload idea, with support from the Project Horus sub-committee.

Your payload will be launched along with the standard Horus tracking and cutdown payloads up to an altitude between 20 and 30 km. As it rises through the atmosphere, it will experience temperatures as low as -80 degrees C, and near-vacuum pressures. After the balloon bursts, your payload will descend back down to the ground, to (hopefully) be recovered by yourself and the experienced Project Horus chase teams.

How does it work?

  1. Build your payload idea!
  2. Bring it along to a club meeting, or e-mail the AREG mailing list – explain what your payload does and what it will achieve. A demo of it operating would be ideal!
  3. If your payload meets the rules below, it will be placed in a queue for launch along with other payloads. Your payload must be at least at the prototype / concept-demonstrator stage before it will be placed in the launch queueFirst come, first served!
  4. When enough payloads are available, a launch will be scheduled. There will be about one month ‘early warning’ of the launch, and then two weeks notice of the planned launch date – Your payload must be 100% ready to launch and tested a week prior to the launch.
  5. Final confirmation of the launch will be given 3 days prior to the scheduled date.
  6. Launch! (and hopefully recovery…)

Any queries should be directed to either the AREG mailing list (preferred, as other club members can see what’s happening), or to Mark VK5QI (vk5qi (at)

Program Rules & Guidelines

Club Membership

This program is open to current (financial) AREG members only.


Your payload should be in the spirit of the amateur radio hobby. That is, experimentation and self-learning in the field of communications (radio and otherwise). We’ve done enough soft-toy launches 🙂

Payload Weight

Payloads must fall into one of three weight categories:

  1. ‘Light’: 1 to 250 grams
  2. ‘Medium’: 250 to 500 grams
  3. ‘Heavy’: 500 to 1000 grams.

Please keep your payload as light as possible!

The lighter your payload, the more experiments we can fit on a single launch, and the higher the altitude the launch can achieve! Payloads in the ‘Heavy’ category will require their own launch, and will only be considered for launch in special circumstances.

Example weights of current Horus payloads, for reference:

  • RS41 RTTY Payload: ~60g
  • Horus primary RTTY Payload: 90g
  • Horus cutdown payload: 150g
  • Horus Wenet imaging payload: 150g
  • Horus Cross-band Repeater Payload: 330g
  • Typical GoPro payload, with 6x AA Lithium batteries: ~350g

Radio Communications / Telemetry

Encouraged! (This is an amateur radio activity after all!)

Transmit / Receive frequencies will need to be coordinated to avoid conflict with the main telemetry downlink and cutdown payload frequencies.

The following frequencies should be avoided:

  • 434.650 MHz (Primary Telemetry Downlink)
  • 431.650 MHz (Cutdown Payload Uplink)

If you are intending to transmit your own telemetry, carefully consider how this will be received on the ground, and by who. Consider using bands we don’t use often (6m? 2m? 23cm?), and try and avoid long trailing wires.


Your payload must not:

  • Have any sharp edges, or very hard external surfaces.
  • Catch fire spontaneously, or on impact with the ground.

Your payload will be hitting the ground at around 5-7m/s. This is equivalent to the payload being dropped from a height of ~1.5m to the ground. If you’re not willing to drop your payload from this height, don’t launch it!

Payload Construction

Foam boxes make for good payload containers!

Styrofoam is your friend! All of the Horus payload have been built from styrofoam sheeting (available at Clark Rubber, amongst other places), and is a lightweight way of building a payload container that also provides shock absorption and thermal insulation.

Power Supplies

We recommend the use of Energizer Lithium AA / AAA / 9V batteries, using a Lithium/Iron-Disulphide chemistry. These have been proven to perform in the freezing temperatures encountered on high-altitude balloon flights. You may use other battery chemistries, though this is entirely at your own risk!


We’ve been doing high-altitude balloon launches for about 8 years now, have an excellent recovery track record, and will do whatever we can (including delaying a launch) to make the flight a successful one. However, there is always a chance of something going wrong, and your payload ending up in the drink, in an inaccessible location, or interstate.

We take no responsibility if your payload is lost!