BlackHorse HAB

Context

In 2015 a local energy drink brand wanted to send the Bangladeshi flag higher than anyone in the country had sent anything before. Their agency, Dogs Day, brought me in through a Kolpokoushol connection. I was in charge of the onboard electronics and the payload fabrication. Everything else — buying the helium, getting the permits, recovering the box from a rice field — we figured out as we went.

Problem

A weather balloon payload is mostly a question of constraints. It has to weigh under 500 grams. It has to survive temperatures from +40 °C on the ground to roughly −55 °C in the stratosphere. The batteries have to keep working at those temperatures. The radio has to reach back down through 30+ km of atmosphere on a low-power 433 MHz link. And the whole thing has to be cheap enough that losing it is acceptable.

What I did

I built the onboard stack around a Raspberry Pi 2 with a Radiometrix NTX-2b as the primary downlink. Primary GPS was a Ublox Neo 6M; we ran a SPOT Tracker as a backup so we’d at least know where the box landed if the main radio failed. A DS18B20 (waterproof variant) sat outside the enclosure for external temperature; a BMP180 handled internal temp and pressure. Camera was a hacked GoPro Hero Session — the unmodified firmware kept shutting down at altitude, so we patched it.

On the ground side I built a Yagi antenna out of copper rod and PVC sheet because there was nothing locally available we could buy. The receiving station was a laptop running fldigi for the RTTY decode.

The enclosure was a block of styrofoam carved by hand, coated with mylar to hold heat in. Energizer Ultimate Lithium AAs ran the whole stack — they’re the only batteries we found that didn’t fall over in the cold.

It took three launches. The first two failed because the batteries underperformed worse than expected at altitude. The third one worked.

Outcome

• Highest altitude reached: 32,450.1 metres (≈106,000 ft)
• Total flight time: 3 h 26 min 41 s
• Ascent: 2 h 07 min 12 s · Descent: 1 h 19 min 29 s
• Lateral displacement: 68.8 km
• Lowest recorded external temperature: −25.31 °C
• Payload mass: 500 g · Helium supplier: Linde

We recovered the box, the GoPro, and a complete sensor log. The footage became the centrepiece of the campaign. The data plots — altitude, temp, internal vs external — are in the repo.

Fun fact: pure helium is genuinely scarce in Bangladesh. Most of the project budget went to gas.