SPEAR II
SPEAR
The Supersized Parachute Experiment Aboard REXUS (SPEAR II) aims to introduce the concept of reusability for high-altitude sounding rockets within DARE, through the design, testing, and validation of a parachute recovery system, capable of safely landing a 100 kg rocket. The experiment is designed to fly in the nosecone of the REXUS sounding rocket in the 14th REXUS/BEXUS cycle.
System-wide Design Parameters
Length
590 mm
Diameter
220 mm
Dry Mass
8.7 kg
Packed explosive
1.25 g
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The Origin of SPEAR II
Every year, DARE continues to expand as a society, and its projects grow in both number and ambition. The increasing scale of projects such as Stratos IV, EuRoC 21 / 22, and Bloom inherently makes financial sustenance more challenging. The SPEAR projects (SPEAR and SPEAR II) were started to provide DARE with a cheaper long-term solution for frequent, large-scale rocket launches.
While the objective of the Supersonic Parachute Experiment Aboard REXUS (SPEAR) mission is to test the Stratos III and Stratos IV drogue Hemisflo drogue parachute at supersonic conditions, SPEAR II will validate a novel, 8 m2, disk-gap-band (DGB) main parachute in subsonic conditions, at high dynamic pressures.
Project Research Value
Parachute behavior can be difficult to model mathematically, particularly during deployment and due to the high degree of uncertainty involved. The existing literature contains very limited inflation models, only for specific parachutes, due to the lack of deployment flight empirical data. Therefore, the current solution for reliably determining inflation loads in subsonic parachutes is through computationally-expensive fluid-structure interaction, compressible flow transient simulations with commercial software. SPEAR II aims to change that for Disk-Gap-Band parachutes, by improving current analytical inflation load models with its collected sensor data.
Mission Overiew
The SPEAR II mission aims to:
Primary Objectives:
- Deploy an 8 m2 main parachute, at a dynamic pressure of at least 4.5 kPa
- Fly and actuate an active reefing mechanism on the main parachute
Secondary Objectives:
- Determine the drag coefficient of the parachute throughout the flight, and visually observe the parachute from deployment to fully disreefed
- Validate an in-house 3D, 6 DoF trajectory simulation tool ;
- Validate an in-house parachute inflation model
Tertiary Objectives:
- Provide an educational experience for the team.
Trajectory Analysis
The trajectory of the SPEAR II vehicle has been simulated using a Monte Carlo analysis with the team’s in-house simulator: ProSIM. ProSIM is a 6 DoF (degree of freedom) 3D trajectory simulation tool that can model the flight paths of free-falling units (FFU’s) through subsonic, transonic, and supersonic conditions. It uses the Nrlmsise00 atmospheric model, together with an in-house inflation model for Earth-bounded reentry mission simulations. ProSIM has already been validated with the flight data from the SuperMAX and ASPIRE S02 missions, predicting the trajectories of these missions with an error below 2%. An overview of several environmental parameter variations during SPEAR II’s descent is given below:
The Parachute
SPEAR II will test an 8 m^2 Disk-Gap-Band parachute with an active reefing system, which is the largest and most complex parachute ever designed by DARE. This parachute will be able to withstand deployment in dynamic pressures up to 4.5 kPa, and Mach numbers up to 0.85.
The Testbed
The testbed of SPEAR II is a 220 mm diameter by 590 mm length capsule housing all the subsystems of the experiment. It is meant to withstand shock loads up to 36 kN and vibrational loads of up to 20 g. Its glass-fiber shell is meant to operate in temperatures between -50 deg C and 150 deg C.
The structural components are listed on the right.
- The Shell
- The Top Bulkhead
- The Trusses
- The Load Cells
- The Rear Bulkhead
- The Stabilizing Counterweight
- The Deployment Device
- The Connector Ring
The Electronics Design
The SPEAR II electronic system will, much like its predecessor, break new grounds in DARE in terms of complexity. While the avionics and power management subsystems follow the footsteps of SPEAR, the data acquisitions subsystem of SPEAR II is the most advanced of its kind. It contains the following sensors:
- two 50 kN load cells
- four temperature sensors for different temperature ranges
- one IMU (Inertial Measurement Unit)
- one static pressure sensor
- one 120 fps 4k rear camera
In this combination, these sensors will be able to determine the drag coefficient of the parachute after deployment inflight, as well as the experiment position, velocity, and acceleration, and transmit these to the ground station
