In the world of rocketry, every launch day is filled with anticipation and excitement, but few experiences are as memorable as what transpired during our recent attempt to launch our first two-stage rocket, affectionately named Venessa. As someone who never considered themselves a blogger, I found myself compelled to document this endeavor after a rather comical series of events unfolded.

The day began as you would expect: the rocket was prepped, the atmosphere was buzzing, and amid the excitement, I found myself shouting 'start!' even though our rocket was barely visible in the distance. With a full-hearted countdown echoing in the air, we joyfully shouted together, '3 2 1 LAUNCH!'

However, what transpired next was not quite the flight we had envisioned. Venessa managed to lift off just a few meters before she appeared to hesitate, almost as if contemplating her fate, and proceeded to topple over onto the launch pad. The motor had ignited, but the thrust was insufficient to achieve anything remotely impressive. In that moment of silence that followed, someone mustered the courage to clap, and soon enough, laughter erupted among the team.

This blog serves not just to recount our humorous misadventure but also to share the lessons we learned along the way, especially for fellow enthusiasts, curious novices, or anyone intrigued by explosions. Welcome aboard!

The Dream

Before diving into the specifics of Venessas design, the challenges we faced, and the nail-biting 'what just happened' moments, lets take a step back and explore our motivation behind building a two-stage rocket.

The primary reason was simple: its undeniably cool. Yet, its also incredibly challenging, which adds to the allure of the project. Two-stage rockets introduce a complexity that single-stage rockets lack. In constructing Venessa, we weren't just launching a rocket; we were creating one that would deliberately separate into two parts mid-flight, and both sections had to operate flawlessly.

Our objective was straightforward: to design, construct, and successfully execute a stage separation event, where the upper stage separates cleanly after the first stage burns out. This endeavor was not about chasing records or achieving breathtaking altitudes; it was a crucial learning opportunity that would pave the way for our more advanced rocket, Asthsiddhi, which is currently in development. Venessa was our experimental stepping stone.

From day one, we adhered to a guiding principle: 'Do it in the simplest way that still teaches you the hard stuff.' This philosophy influenced every aspect of our projectfrom how we built the motors and selected materials to our avionics design and the deliberation of which components deserved overengineering and which could be hastily assembled with glue.

Our journey involved months of designing, testing, failing, and refining. But all of this stemmed from one foundational question: Can we build a rocket that intentionally breaks apart in mid-air without succumbing entirely to gravity? Lets explore how that unfolded.

Venessa's purpose was not to achieve unprecedented heights or blistering speeds; it was about smart design and effective execution. Our focus was on mastering stage separation rather than striving for perfection. Thus, instead of obsessing over every performance metric, we concentrated on the core challenge: ensuring that Venessa would separate mid-flight in a controlled and reliable fashion. All other considerationsstructure, propulsion, avionicswere built around this singular goal.

We anticipated compromises and were comfortable with that notion. Not every component needed to be aerospace-grade. We didnt require high-end materials like fiberglass or carbon fiber; we simply needed parts that could get us to our learning moment.

Every decision revolved around the question: 'Whats the easiest and most effective way we can build this to facilitate learning?' At times, this meant utilizing cardboard parts that could have been 3D-printed or opting for paper tubes instead of costly composite bodies. In other instances, it meant allowing a stage to fall ballistically without a recovery system (farewell to our first stage; you fulfilled your purpose). This is the beauty of a learning prototypethe freedom to make mistakes intentionally.

Venessa was not a rocket designed for fame; it was a rocket engineered to educate us.

Propulsion

When it came to propulsion, we knew it was time to move away from our previous use of unreliable PVC and embrace the advantages of metal.

We developed solid rocket motors featuring stainless steel casings, aluminum end caps, and mild steel nozzles. It may sound high-tech, but the truth is that while PVC is lightweight, it lacks the structural integrity needed under pressure. Metal, though more challenging to work with, provided us with reliability and peace of mind (not to mention fewer heart-stopping moments during static tests).

For our fuel, we opted for KNDX, a combination of Potassium Nitrate as the oxidizer and Dextrose as the fuel. This choice was mostly due to our extensive experience mixing this sugary compound over the past yearour team had become practically expert bakers in this regard. The process involves precisely mixing the components in their stoichiometric ratio, followed by melting, casting, and curing them into grainsthose essential little cylinders that deliver thrust and determine the burn profile.

To simulate and design the motor, we utilized OpenMotor, an open-source software tool that allows users to input their grain geometry, number of grains, nozzle dimensions, and more to predict performance. The first two things we focused on when designing our motors were thrust (the speed we aimed for) and impulse (how far we intended to go).

Ultimately, we ended up with two motors: G136 and G96. The names are significant; the number following the letter denotes average thrust in Newtons. Hence, G136 delivers a greater punch than G96. Each stage was equipped with its own motor: G136 powered the first stage, while G96 took over after separation. We relied solely on our calculations and hope, as the ignition system was quite basic.

Thus, propulsion became an intricate blend of physics, mathematics, and a bit of wishful thinking. Remarkably, the combination didnt result in total chaos.

Structure

In the same way that propulsion provides the fire, the structure serves as the skeleton holding everything togetheryet ours was made from paper. Yes, you read that correctly.

The main body tube of our rocket was crafted using strips of paper salvaged from old Engineering Drawing sheets left behind by students. Instead of purchasing a pre-made cardboard tube, we repurposed these sturdy sheets. This not only made the build process more engaging and hands-on but also saved us some costs (although that wasnt our primary motivation).

The construction method was quite innovative. We built the body tube layer by layer, spirally winding strips of paper over a PVC pipe. Each layer consisted of 5-6 strips, and every new layer was wound in the opposite direction of the previous one. This alternating spiral pattern provided impressive strength and rigidity. In total, we applied around 5-6 layers, all bonded with our trusty Fevicol-and-water mixtureessentially a well-constructed paper-mch shell engineered for flight.

The nose cone boasted a clean ogive profile and was 3D printed using PLA filament. Although we had experimented with paper-crafted nose cones before, 3D printing offered us consistency, precision, and speed. If you have access to a printer, its the obvious choice.

The fincan and fins were also 3D printed. While this decision compromised some strength compared to fiberglass or carbon fiber, for this flight, structural integrity was secondaryour main concern was testing stage separation. The 3D printing process allowed us to prototype quickly and focus on what genuinely mattered: functionality over excessive engineering.

The first stage was designed to be as simple as possible. It consisted of a 3D printed fincan, fins, and a solid rocket motor. We intentionally refrained from using any mechanical separation system, ensuring that the first stage would simply detach after burnout or experience a hot staging as the second stage ignited (part of us secretly hoped to witness that hot staging).

The avionics bay housed the brains of the rocket. We created a 3D printed mounting plate with slots for the power switch, along with two discs that allowed for secure mounting inside the rockets body using screws. This bay contained two flight computers, one situated on each side of the plate.

Above the avionics, we installed a spring-loaded ejection system, firmly secured with screws (more on that later in the Recovery section). To prevent the motor from sliding upward within the rocket, we included a wooden engine blocka simple disc cut from plywood that was epoxied into place. This solution was effective, strong, and ensured thrust was directly transferred to the airframe.

We utilized OpenRocket, an incredible open-source simulator, to model our complete design. This tool enabled us to estimate stability, center of gravity, center of pressure, and overall flight performance. OpenRocket serves a purpose in structural design similar to that of OpenMotor for propulsionboth are beginner-friendly and immensely useful.

Avionics

The avionics system was vital to our mission; our primary objective was to develop a system capable of actively managing stage separation.

In traditional two-stage model rockets, stage separation is typically passive. These rockets often utilize commercial motors with well-documented thrust curves, making it easy to design a system that triggers separation after a predetermined time delay or altitude using predictable motor behavior. However, our situation was different; given that we were employing in-house manufactured motors, we lacked precise thrust profiles. Consequently, we needed to trigger separation actively and intelligently based on real-time sensor data.

To achieve this, we devised burnout detection logic that relied on acceleration values. During thrust, acceleration remains significantly positive, but when the motor burns out, the acceleration drops sharply, often becoming negative due to drag. We utilized this sudden shift as our primary indicator of burnout, employing redundant logic to verify the duration of negative acceleration to avoid false triggers.

Hardware redundancy is critical in avionics, and utilizing different hardware architectures enhances reliability. While we excelled in some areas, we recognized opportunities for improvement. We operated two independent flight computers:

• Grace Based on an Arduino Nano
• RocketNerve Based on a NodeMCU featuring 4MB of internal flash (used for logging)

Both systems adhered to a similar basic architecture:

1. A main microcontroller processes sensor data and triggers events
2. A BMP280 sensor for barometric pressure and altitude
3. An MPU6050 sensor for 6-axis inertial sensing (measuring acceleration and angular velocity)
4. Two pyro/ejection channels controlled via transistors acting as switches
5. Powered by a 1S LiPo battery

This modular arrangement allowed us to analyze real-time flight data and reliably trigger both stage separation and parachute ejection.

Firmware & Control Logic

Both flight computers operated on custom firmware designed to:

• Continuously monitor acceleration and altitude
• Detect burnout based on declining acceleration
• Trigger stage separation
• Monitor altitude for apogee detection
• Initiate parachute ejection

We plan to delve into detailed firmware and flowcharts for this process in a future blog post, but the key takeaway is that everything functioned in real-time and was event-driven rather than time-based.

Recovery

For this initial flight, we opted to recover only the second stage. Technically, we did recover the first stage too, but not through any dedicated systemit simply fell ballistically. Given that the rocket wasnt designed to reach extreme altitudes, this seemed acceptable.

The second stage featured a spring-loaded parachute ejection system paired with a spherical ripstop nylon parachute. This parachute was connected to both the ejection mechanism and the nose cone, facilitating the safe recovery of both components after reaching apogee.

Ejection System Mechanics

The ejection system operated with a spring mounted above the avionics bay, supported by a basic structure made of wood and PVC. The spring was compressed and held in place by a thread tied between two screwsone at the top and another at the bottom of the ejection assembly.

A disc-like platform rested atop the spring, serving as a base for the neatly folded parachute. The thread securing the spring was rigged with an e-match (electronic match) surrounded by a bit of gunpowder and secured with paper tape.

This e-match was wired to both flight computers, granting either the ability to trigger deployment.

Deployment Logic

Once apogee was detected, either flight computer could activate the e-match. Upon firing:

1. The e-match incinerates the thread.
2. The spring is released, propelling both the parachute and nose cone outward.
3. The parachute unfurls mid-air, ensuring a safe recovery for the second stage.

This system was ingeniously simple, robust, and lightweight; it operated just as plannedno pistons, no CO canisters, just basic mechanical ingenuity coupled with a sprinkle of explosive magic.