Overview
This year I led the development of two, 3U CubeSats which are deployed from the rocket "Pitchfork". The rocket is 10.5' long with a 6" diameter, weighing in at nearly 80 lbs. The payload is deployed at apogee (10,000 ft) as a 6U unit and separates into two, 3U CubeSats with independent recovery systems.
The top CubeSat, Helios, is equipped with a variable reefing parachute system to control descent rate, solar panels and landing legs deployed mid-flight, and the top of the "Lumberjack" system which is used to split the payload into two parts.
The bottom CubeSat, Hermes, has its own passively deployed parachute upon separation, grid fins for roll stabilization, and live video feed transmitted to the ground.
During the 2024 Spaceport America Cup, the team was awarded the Jim Furfaro award for technical excellence, scored 1st for design and build, and scored 4th for technical documentation.
Deployer
The deployer was redesigned this year to rely on fewer sensor triggered events in order to deploy the payload at the correct time.
The previously custom machined rails were simplified and sourced from a commercial vendor. They were later finished and polished by hand.
Deployment is triggered by the rocket's drogue separation. When the separation devices fire, a force is created in opposing directions between the two halves of the rocket. This load is transferred into shock cords that run down throughout the nosecone and wrap around the CubeSats. The resultant tension slides the CubeSats along the deployer rails and out of the upper airframe.
1 | Modular
Standard CubeSat frame design with options to change form factor during flight
2 | Interesting
Showcasing Grid Fins, Solar Panels, Landing Legs, Live Video, Variable Reefing Parachute
3 | Redundant
Critical operations rely on Avionics triggered events and have backup systems in place
Grid Fins
Two Carbon Fiber-Nylon 3D printed control surfaces actively stabilize roll during flight.
Custom aluminum linkage provides independent control
CFD was used to tune PID parameters.
Variable Reefing
A thin line runs around the Helios canopy and feeds to a winch that controls chute aperture.
The variable reefing system (VRS) can adjust descent rate from 10 - 25 ft/sec in order to match the descent rate of Hermes.
The system is folded with the chute lines to ensure untangled deployment
Parachute Ejection
A dually redunadant servo system ensures primary parachute ejection after deployment.
A friction fit cap keeps the parachute contained inside of the deployer.
Solar Panels
Two different chemestries of panels (ETFE and Polysilicon) are used to compare efficiency and power collection throughout flight.
Landing Legs
Facilitating solar panel alignment with the sun after landing, the spring loaded landing legs deployed alongside the solar panels and locked in place mechanically.
Testing
Regular testing was performed throughout the semester on all of the subsystems under development.
Milestones were set for all critical systems with an emphasis on early parachute system testing and working flight computer designs.
Payload was also involved in rocket separation testing to evaluate CubeSat ejection from the deployer.
Launch
An oversight on the main rocket apogee detection system caused the flight vehicle to experience premature separation triggering during flight. This resulted in the full separation of the rocket causing the forward airframe to cant and do two full loops in the air before the shockcord between the two sections was severed, and the booster continued on an upward flight.
Since the rocket separated, the deployer system was able to eject the CubeSats immediately where they deployed parachutes and traveled safely to the ground. While this failure of the flight vehicle was unfortunate, the CubeSat system proved its redundant systems and safe operation under unexpected conditions.
