Brandon Lindquist

System Overview

Ares is the liquid fueled rocket team of Rocket Project, and designs are generally iterated on every year instead of starting from scratch as is the case with the hybrid team, Prometheus. 

Project Goals for 2023-24

For the 2023-24 year the overall focus of the vehicle engineering side of the team was:

• Launch Viability

• Manufacturing Quality

• Comprehensive Analysis/Simulations

• Major mass reduction

For Recovery, the focus was manufacturing quality and mass reduction.

CAD of Recovery Bay and Components

Detailed Deployment Sequence

Ares currently uses a single stage separation event to deploy its parachutes. The drogue is deployed during the initial separation, and once the rocket descends to a much lower altitude a tender descender separates to pull out the main parachute.

Original Shock Cord Layout

Mass Reduction

Quicklink alternative: Kevlar Softslinks?

A significant amount of mass is found in the variety of steel quick links that are used throughout the shock cord. An alternative was found: kevlar “soft links”  These offer similar loading capabilities at a tiny fraction of the mass, reducing 1.318 lbs to 0.042 lbs a 97% mass savings!

Load Testing the Kevlar Softslinks

Using an Instron, we tested the failure modes of the kevlar soft links in multiple configurations. The results showed a consistent stitching failure on a single loop of the kevlar at approximately a 900 lbs static force. This was much less than expected, and verified that doubling the loop would be required for the flight system.

(Experiment 2 had an anomaly that was possibly caused by extensometer slippage, or partial stitching failure at 2 kN.

Bulkhead material change and design

The team had a system wide materials upgrade by switching from Aluminum 6061 to Aluminum 7075. 7075 offered significant strength improvements, allowing for bulkhead designs that require less material, and thereby less mass. Where the yield strength of Al 6061: ~276 MPa and Al 7075: ~503 MPa.

• Lower bulkhead was reduced from 0.8” to 0.5” thickness and additional cutouts resulting in a 30% mass reduction.

• Upper bulkhead was reduced from 0.7” to 0.4” thickness resulting in a 28% mass reduction

Shock cord layout simplification

Further mass savings was found by: 

• Reducing the shock cord size from the 4000 lb 1” cord to a 2100 lb ⅝” cord

• Eliminating the main shock cord and attaching it directly to the bulkhead

• The parachutes chosen for this year did not have integrated swivels

Final Flight Configuration

Overall mass saving of 2.56 lbs, a reduction of 29%!

Equipment and Technical Specs

Drogue chute:
Iris Ultra 36" HP Compact

Size - 36in diameter
Released at apogee (30,000 ft goal)
Coefficient of drag - 1.5 to 1.6
Slows descent to ~72 ft/s
Shape - Elliptical 

Main chute:
Iris Ultra 144" Compact

Size - 144in diameter
Released at ~1700 ft 
Coefficient of drag - 2.2
Slows descent to ~18 ft/s
Shape - Toroidal

Manufacturing Quality

For this year, we were able to work with a professional machinist who was able to provide us with beautiful parts with extremely low tolerances. 

Testing

Separation

For final separation testing, we fully integrated the recovery system with all the electronics and shock cord. The altimeter triggers the ejection charge at apogee by sensing a plateau in the change of atmospheric pressure. To trigger this event, we sealed up the body tube as air tight as we could and mounted a vacuum to a hole in the body tube. Once turned on, the vacuum would suck all the air out of the recovery electronics bay until the pressure stabilizes, simulating apogee and triggering a separation. A baby stroller was used to catch the nose cone.

Test Rockets

Test Rocket 1

Test Rocket 3

Integration

Launch

Launch was mostly nominal, there was a wobble coming off the launch rail and the throttling mechanism partially failed. Only throttling down a fraction of what was planned for. This resulted in a trajectory that was significantly faster on ascent than was the goal and aerodynamic forces(wave drag) kept the apogee much lower than was hoped. These factors combined with a tank design that was too short, left our appogee at 24,111 ft, significantly below our 30,000 ft target. 

Recovery was a complete success! The rocket landed safely under main 2.4 miles from the launch site with zero damage. Unfortunately we did not get the recovery sequence we had hoped for, with main deploying at/near apogee. The horizontal velocity was approximately 280 ft/s at separation, a speed that handedly tore open the main parachute from its taped enclosure.

Reflection

A single bay recovery system is proving difficult to achieve a reliable recovery sequence. A more robust approach may be to have two separation events, one for the drogue, and one for the main. This would greatly widen the realm at which a successful deployment sequence may be achieved. However, it would be a mass hit, as it would require 2 more bulkheads. Another alternative may be to use a line cutter on a cable that keeps the main tied shut after separation. This seems far too risky for me though, as separation and descent under the drogue is very chaotic. This environment could break the e-match on the cutter, which would then prevent the main from deploying entirely, and destroy the rocket on landing.