BIG RED 2

Big Red 2 is a 4 inch diameter dual-stage rocket with a targeted apogee of 60,000ft. It is designed to test a few critical design elements for the upcoming Pioneer Program, namely fin design for Mach 2+ Flight, as well as recovery systems for flights over 50,000 ft.

Design

A large part of Big Red 2's design was based around being both a test bed rocket for future technologies to be used in the Pioneer program, as well as a successor to Big Red 1. One of the biggest improvements over Big Red 1 was motor selection. For the booster, an Aerotech M1939W was used, mainly for it's combination of high thrust and a flat thrust curve, and then the sustainer used an Aerotech M685W was chosen for it's long burn time, and regressive thrust curve.

Another improvement over Big Red 1 was that Big Red 1 was way longer than it needed to be. This was mostly due to Big Red 1's initial goal of participating in a competition that would have required a payload, and the space to accommodate it. As Big Red 2 didn't have this design constraint, the airframe could be made much shorter, and thus much lighter. This in combination with the optimized motor selection is why the apogee of Big Red 2 is double that of Big Red 1.

A big part of the design process for a dual stage rocket is the timing of when the two stages separate, and when the sustainer motor ignites. Ideally, the longer we wait to separate and ignite, the higher our overall apogee becomes, but we also need enough speed to keep the two stages stable upon separation and ignition. How we determine this value is we look to see when the rocket slows down to around 750 ft/s, and use that as the mark for sustainer ignition, and then set booster separation to be a second prior to ignition to give it time to get away from the exhaust from the sustainer motor.

Unfortunately, due to logistical issues, we were unable to procure a M685W in time for the launch, so it had to be substituted for an Aerotech M1780NT, which threw off the stability of the rocket, as by this time the airframe had already been built. But this was combated by adding additional mass to the nose cone. The combination of the motor swap and the additional mass did decrease the expected apogee to around 45,000 ft.

Recovery

As stated, one of the main design objectives for Big Red 2 was to test out ways of deploying parachutes at high altitudes. Traditionally, Pyrodex is used as the charge for the separation charges, but it tends to burn very poorly in low oxygen environments, such as up at high altitudes. One solution is to use a system that doesn't rely solely on the combustion of powder to create pressure. A CO2 ejection system was chosen for Big Red 2, as it works by puncturing small CO2 canisters rather than the combustion of powder, making it operable regardless of altitude.

However, this system came with some fairly significant design challenges to solve. Namely how to cram 2 redundant CO2 systems into a 4 inch diameter Avionics Bay. One problem was the very large holes that needed to be cut into the bulkheads. Typically, G10 Fiberglass is used to make our bulkheads, but this would have been very prone to cracking at the thinner sections, so the decision was made to machine a pair of custom bulkheads out of 6061-T6 Aluminum, as it's higher ductility would make it much more resistant to cracking under load.

The other major design challenge was space. A typical 4 inch Avionics bay would be around 10 inches long, and the tubes that house the CO2 canisters are 4.5 inches long. meaning a significant amount of internal space was used up, meaning that the flight electronics had to be crammed in on the opposite side.

Launch Results

Big Red 2 was launched on the December 15th, 2024 out of the Friends of Armature Rocketry launch site in the Mojave Desert. Unfortunately, the day of launch, there were a number of dust storms in the area, meaning winds were very high, right at the upper limit of what was safe to launch. We did launch, however, but unfortunately the combination of high winds and not having sufficient ballast mass meant that the sustainer wasn't stable enough to stay stable, and thus hit the tilt lockout on the flight computer, meaning the sustainer motor was never commanded to ignite. All parts of the rocket were successfully recoverd.

Flight Data

Unfortunately, due to a sensor error on the Telemega flight computer, we don't have data for how fast the rocket was traveling. We do know that it launched to an Apogee of 11,708 ft, and landed about 1.5 miles from the launch site, in the opposite direction of where it was launched, due to the extreme winds catching the parachute

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Launch Gallery

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