Capsule & Recovery

About the team

The Capsule and Recovery team started out as a sub-team of the Stratos II project. In this project, the team was responsible for the structural integrity of all the components above the engine as well as the recovery system. The main components that were designed and produced were the glass fibre nosecone shell, the payload section and a dual-spring-deployed parachute system.

The whole capsule section was designed with numerous iterations and tests along the way. Eventually, the final design for Stratos II and Stratos II+ were developed. This was composed out of a double clamp band system held together by spring steel. At predetermined moments these steel band would release, deploying the drogue and the main parachute respectively. On top of this dual parachute system, came the payload section, with a U-shape rack housing the external scientific payloads. To finalise the capsule, the onboard electronics were housed in the top of the nosecone, combined with an antenna for data telemetry and video downlink.

Capsule-Stratos

Stratos II+ Capsule overview

Current project

The current project that the Capsule and Recovery team is working on, is Project Aether. This project is a collaboration between multiple DARE teams to produce and launch a rocket to test several experimental technologies.

Gas powered ejection and pyroboltsCapsule - Mortar

The team has developed a gas powered ejection system called ‘mortar system’, which will deploy the drogue chute at high-speed sideways through the rocket. This prevents the rocket from having to separate into multiple segments for the parachute to deploy. By using this system the ability to predict the stability of the rocket and the flight dynamics involved are greatly simplified. After the drogue has deployed it will be attached at the bottom of the rocket with an explosive bolt. This bolt is custom designed and uses a small amount of black powder to break a steel bolt in half. Once this mechanism is activated in flight, the drogue should be separated from the main rocket structure and only remain attached to the main parachute. The main parachute will then be pulled out by the force of the drogue and deploy, ensuring the rocket will have a low end-velocity on touchdown.

Parachutes

The hemisflo drogue chute

The hemisflo drogue chute

The designs for both parachutes are another innovation within DARE. The drogue parachute design is a complex hemisflo ribbon parachute consisting out of numerous pieces of fabric stitched together.  This intricate design should ensure the parachute can survive the high speeds in the initial phase of the descend while also maintaining its stability. The main parachute will be a standard cross-shaped parachute or a small variation thereof. The current design calls for a 15m2 parachute which will be the largest parachute ever developed by DARE.

Structure

The structure of the capsule will be similar to Stratos II+, meaning it will be a glass fibre shell. The nosecone will again house the flight electronics and antenna. All the different sections of the rocket will be connected using identical couplers. This was designed so that all sections can be prepared independently and that section could easily be added or removed if it would be necessary.

Testing

All new subsystems (the mortar, explosive bolt and parachute designs) have been tested already and were mostly successful. Static test campaigns were held at the end of the summer and in September to prove the concepts behind the mortar and explosive bolt. Ultimately, all systems were combined in a CanSat rocket and launched in September 2016. During this launch, all systems that we wanted to test worked. Unfortunately, the wires holding the parachutes broke off on deployment, which meant that the CanSat came down without a parachute

To further improve our knowledge and confidence in the parachute system, a series of wind tunnel experiments were performed in October 2016. During this test campaign, 4 different main parachutes were tested and 1 drogue parachute. These tests were used to expand the knowledge on stability, shock loads and other parameters of the parachutes. Results of these tests will be published later.