Timothy Best

Autorotational Descent vehicle

The goal of this project is to create an autonomous descent vehicle that is capable of landing a small payload from an altitude of ~30,000 meters (100,000 ft.). To test that the vehicle can perform this task it will be attached to a weather balloon, released and it will return to the position of launch. The descent will be slowed and controlled with an aerodynamic phenomenon known as autorotation. Autorotation is a state of flight where the rotorcraft's main rotor is unpowered and the rotor gains rotational speed form wind. This rotational speed can be converted to lift by adjusting the angle of the craft relative to the wind. Allowing for softer landing than the conventional parachute.

A Presentation on the important of autorotation can be found here.

Ascent vehicle prototypes: One Two Three.

Descent vehicle prototypes: One Two Three.

Descent Vehicle

Estimated Costs can be found here.


Praachute Release:

Autorotation is a safe form of descent but as with any untested technology many things can go wrong. Including but not limited to:

To prevent damage to the payload or anything it may land on the vehicle will be equipped with a parachute. The parachute will be deployed by an electronic match if at any moment the vehicle is traveling to fast or does not have sufficient rotor speed to preform a safe landing.

Cutdown Device

Many hobby balloon projects add a release mechanism to their set up. These systems are an added insurance so that if the balloon reaches an equilibrium then the payload will be released before the balloon drifts to far away. If the payload is not cut down it will drift far away and most likely wont be able to be recovered.

Detachment form a balloon in equilibrium is still a issue for this project but the greater concern is if the collapsed balloon is still attached during the decent. In this scenario the balloon will act as an unpredictable drag force and will jeopardize the capabilities of a safe descent. Therefore the balloon must be detached. To ensure detachment I will be coming up with multiple devices and then using the best two devices.

Radar Reflector:

Radar Reflector

A radar reflector is required legally on weather balloons by the FAA or Federal Aviation Administration. It must echo radar operating in the 200 - 2700 MHz range. TO achieve this our radar reflector will comprise of 3 one foot diameter Styrofoam disks each covered in a space blanket (thin aluminum foil). The disks are oriented in such a way as to form 8 corners. Giving this device the ability to echo any radar that hits it directly back to its source. Allowing our vehicle to be seen. Therefore protecting the payload and any other air traffic.

Mathematical Model

The first mathematical model estimated the aeronautical properties based on a body that was already at maximum rotor speed. This decent vehicle starts with little to no rotational speed so the model must also simulate this portion of the decent. The second model achieves this but assumes all vector forces are purely vertical. This model is great for low altitude but will need to be updated once again to account for wind speeds.

The current form of input into the model is with: InitialConditions.txt this file is inputed into the model which out puts data in a .csv FirstModelOutput.csv.

The First Model: Estimations.java, Variables.java

The Second (Incomplete) Model: Variables.java


The decent vehicle will be using a modified version of ArduCopter-2.9 that will support an auto rotational decent from high altitude.

Action Plan:


To increase the probability of success testing will be broken into multiple sections including on ground and in air testing.

Special Thanks

The Project Webpage can be found here.