The HAPP project embraces a strict ethic of do-it-yourself tinkering. This is aerospace engineering for hackers.
The goal of the High Altitude Photography Platform is simple: Capture pristine 360-degree, high-definition video from extreme altitudes around 30 km (100,000 ft). Others have tried it, but none have done it with an actively stabilized platform, and their cameras typically bounce around below large balloons.
The one inviolable rule for the project is that we remain true to a do-it-yourself ethos. Don't outsource the engineering. All parts and manufacturing processes must be readily available to any hobbyist; no cheating by purchasing real aerospace hardware from the pros. We're hackers at heart, and this project is for fun, not for profit.
That being said, the laws of physics are pretty hard to change, and the physics dictated our final engineering decisions. Occasionally those decisions required some fancy things like a lightweight, carbon-fiber structure and aeroshell. It's easy enough to contract out that kind of manufacturing if you have deep pockets, but how can you build it in a garage? By spending months developing a production cell using parts from the local hardware store. Over 80% of the 22 months for development were dedicated to creating tools and methods rather than actually producing flight hardware.
The HAPP ascends using a weather balloon. At apogee, pyrotechnic devices sever the link with the balloon and the HAPP plummets back to earth, nearly breaking the sound barrier during descent down to thicker air. The platform resembles a scaled-down Apollo Command Module and is essentially a lightweight flying wing, so it falls slowly in dense air at low altitudes. But to ensure a safe landing, and because it looks freakin' awesome, three parachutes are deployed prior to landing using pyrotechnic mortars.
During flight, the HAPP utilizes a cold-gas reaction control system (RCS) and an autopilot function to stabilize the platform. Small jets fire as needed to control spin. This is critical for obtaining smooth video footage. The HAPP is subject to disturbances from the atmosphere, from the natural motion of the balloon during ascent, and from motion induced by balloon rupture or cutdown at apogee.
Why not simply tie a drone to a balloon and be done with it? It won't work because there's almost no atmosphere up at 30 kilometers for propellers to grab onto and generate thrust.
The HAPP can easily drift 100 kilometers or more during a mission. To ensure the ground crew can recover the craft, we developed a satellite-based communication system. One of the onboard computers continuously sends down GPS coordinates and other status information. This data is funneled to a mobile app which maps the current position so the ground crew knows where to go.
A typical mission requires almost two hours to reach maximum altitude and only 15 minutes to descend and land.
What We've developed
- Control software for stabilization implemented on an Arduino
- Cold gas reaction control system (RCS) with 3D-printed jet nozzles
- Bonded carbon fiber structure with CNC-machined components
- Vacuum-molded carbon fiber / Kevlar aeroshell
- Pyrotechnic guillotines for balloon separation
- Earth Landing System (ELS) with parachutes in pyrotechnic mortars
- Redundant power busses and onboard computers
- Optimized packaging for minimal weight, stable flight, and clear field of view for the cameras
- Cryogenic vacuum chamber for testing
- High fidelity CAD model and simulations
- Duplex satellite communications
- Real-time tracking on a mobile app
- An empty bank account and frazzled spouses