Using Autodesk Fusion 360 and Generative Design to Make Lighter Rockets in Less Time

CHARLIE AVELINE: Designing and building rockets is one of the most technically-complex engineering challenges of the modern age. It requires a multidisciplinary approach, involving many different fields, ranging from aerodynamics and structural analysis to model-based control system design.

In 2018, four aerospace engineering students at Imperial College London aspired to enter the Spaceport America Cup, an international rocketry competition hosted here in the States. Since then, our team, Imperial College London Rocketry, has grown to over 100 members. And with that, our ambitions have too.

TANVI GIR: Based in London, we strive to enrich students' aerospace engineering education through the design, build, and launch of actual rockets, giving students exposure to real-life engineering problems. The team is divided into four major technical subthemes, each developing various aspects of rockets.

The airframe and recovery team design the structural and aerodynamic framework of the rocket as well as the critical systems that ensure that we can recover our rockets successfully. The propulsion team handles the systems that generate the thrust produced by the rocket in order for it to reach a set altitude.

KIRAN DE SILVA: The electronics team focuses on the avionics, telemetry, and power systems that control the various subsystems during launch and flight, as well as providing critical data for performance analysis. Last but not least, the systems and integration team ensures that cohesive design of whole rocket and performance trajectory simulations to ensure our rockets perform optimally.

Since our inception, we have developed numerous rockets, each of increasing size and complexity. Our first two rockets, A.P.O.G.E.E and November, built the foundations and taught us the basics of rocketry. We then developed Constant Impulse, a 3.4 meter, 30 kilo rocket, which we took to the second edition of the European Rocketry Challenge also known EuRoC.

CHARLIE AVELINE: Before going any further, I think it's worth explaining what a rocket is and how it works. All rockets are powered by engines, and these come in 3 variants, solid, hybrids, or liquids. And this depends on the different propellants used. All engines produce thrust, which propel them upwards. It's down to the airframe to keep all of the internal components safe during flight and to provide an aerodynamic shape to help reach its target altitude.

The electronics are the brains behind the rocket. They track and transmit data about the flight, as well as control different systems, such as the engine or recovery system to ensure that it touches down safely.

KIRAN DE SILVA: The European Rocketry Challenge is Europe's largest student rocketry competition. Taking place in Portugal every year, it brings over 400 students from Europe's top universities to design, build, and launch rockets to a set altitude.

Teams competing at EuRoC must design and launch a rocket carrying a defined payload to a target altitude. We were required to reach an altitude of 10,000 feet above the ground level carrying around 6 pounds of scientific payload.

The rocket can either be powered by student research and developed propulsion system or a commercially-available rocket engine. It must also meet several design test and evaluation criteria to be cleared for launch.

TANVI GIR: The integration of Fusion 360 into our workflow has streamlined our design process and accelerated our rockets development on a budget. We originally chose Fusion simply because it was extremely user friendly. It worked on everyone's computers, didn't take up too much space, and was extremely easy to pick up even for first year students who hadn't used CAD before.

At the most basic level, the design of a rocket involves the design of components. These components then integrate to form systems, which then integrate to make the rocket. The design of a component starts by defining its requirements. We cannot design anything unless we really know what it needs to do.

So in general, these requirements can include size constraints. They could include load constraints so that the path must be able to withstand, or interfacing constraints to ensure that the components of the rocket fit together nicely.

Requirements also outline what would make the design optimal. Typically, this is done via some form of an objective function. So I'm designing a part to minimize the mass or to minimize the manufacturing cost.

CHARLIE AVELINE: After the requirements are defined, the conceptual design can begin. And this starts by designing an initial part. We then go and simulate that part and check if it meets our requirements. But rarely does a part meet its requirements on the first time, so it's more of an iterative process. We redesign and resimulate until we're happy with our design and check that it's optimal.

COVID-19 presented a particular challenge in the development of Constant Impulse. Since all of us were working from home, we had to adapt our workflow to work online. However, since all of our files were online already, this was not too much of a challenge. Multiple people could access a file at once, and we could discuss and make design evaluations. So therefore, our process didn't really change that much.

KIRAN DE SILVA: Critical to our efficiency were the simulation tools embedded within Fusion 360, allowing us to analyze the effects of launch and shock loads on all the structural components of the rocket. Traditionally, design and simulation tools are separated, requiring manual export and import across programs with many differing file types.

Fusion integrates the two seamlessly, allowing us to make design adjustments and resimulate the parts easily. Being able to run structural analysis simulations on the cloud has also been a real game changer for us. It doesn't matter what laptop a student might have. We are all able to run structural simulations from any computer anywhere.

Furthermore, rather than local simulations where you have to monitor their progress, with cloud simulations, we can submit and solve the job in the background while we work on another task.

CHARLIE AVELINE: Structural simulations are run for multiple load cases, but what is a load case? A load case is made up of two parts, the constraints and the loads. Constraints define how a part is attached to its surroundings. So for example, a bolt or an adhesive may attach a component to the rest of the airframe. The loads include forces, moments, or accelerations that act on a part.

For different sections of the flight, we have different load cases. However, there are three main load cases that the rocket sees throughout the flight. The first of which is on ascent, where the engine produces thrust which tries to compress the rocket.

The second major load case is the shock load. The shock load is when the parachute deploys and creates drag, and this drag is transmitted through the rope that attaches it to the rest of the rocket and jerks the rest of the rocket. This creates a tension force which tries to rip the rocket apart.

The third load case is the bending force due to the fins. As the rocket moves through the air, the fins generate lift, which tried to snap the rocket in half.

All of these load cases must be tested to check whether the stress is fit within the yield stress of the part. If it is above the yield stress, then the part will break. A safety factor allows us to quantify how protected a part is against uncertainty. Achieving a higher safety factor means that our part is less likely to break but often comes at the cost of extra maths. So therefore, it's about finding a balance between the two.

TANVI GIR: A key part of our design workflow was generative design. This offered a solution for optimal designs in a limited time frame. For all structural components, generative design was integrated straight after the initial 3D model. No manufacturing constraints were applied, and the algorithm was right.

The output was a set of manufacturable outcomes which would highlight the applicability of generative design to that specific load case and a set of non manufacturable outcomes which provide valuable insights into the nature of the load case, and what a truly optimal solution would look like.

Now although, much of our racket doesn't look generatively designed, it definitely has informed the design of the majority of the components. And in doing so, has accelerated the development of the entire rocket.

For some components, the weight saving provided meant that it was worth exploring this more exotic manufacturing method, such as for the aluminum-based stopper that you see here on the screen. This weigh just 78.3 grams even though it was designed to withstand 400 pounds of force with a minimum safety factor of 2.7.

Using generative design, the team was able to reduce the mass of the booster interface by 27% compared with the baseline design that we had originally started with.

CHARLIE AVELINE: Every component was evaluated by the entire team at design reviews which took place at critical points during the year. And once we were all happy with the designs, we created an assembly of the entire rocket and Fusion. This allowed us to discover incompatibilities between parts or assembly issues prior to the manufacturing stage. We could also check that our designs enabled us to meet Europe's requirements.

For the manufacturing, engineering drawings are often the standard, but it can be difficult to understand complex parts or assemblies from a 2D static diagram. When we were in the workshop, we often found it a lot easier to just pull up the Fusion file and inspect the part in 3D so that we could give critical interfaces the attention to detail that they needed.

After months of manufacturing, two weeks prior to the launch, the completed rocket was packed in a box and sent off to Portugal for Europe 21. Much to our relief, the rocket had arrived in Portugal in one piece. We arrived at our home for the next week, the paddock.

After a day of unpacking our rocket and settling in, the team started to prepare for the Flight Readiness Review, better known as the FRR. This review consists of a panel of expert engineers inspecting and questioning every single aspect of our rocket.

Most Flight Readiness Reviews are a multiple hour-long grilling of each team's rockets. Any part which does not meet their strict requirements would drown the rocket and ruin any dreams of a launch.

KIRAN DE SILVA: The first step in this process was to perform a successful ground test of our recovery system. This involved the ignition of an explosive black powder charge and the pressure created by this explosion which split the rocket in half, allowing the parachutes to deploy and the rocket to recover safely.

Following a successful ground test, we move straight onto the assembly of our rocket. This was where we found our first major issues. One of the joints in the rocket was loose, and as a result, the rocket was able to bend. Immediately, we had to design a solution, which given the limited resources available, was difficult.

After hours of discussion, brainstorming, and modeling, a small group of people made the hour and a half journey to Lisbon to pick up crucial supplies for a make or break solution.

The solution we settled on was to create a fiberglass tube which would fit around the joints and add rigidity. Wrapping sheets of fiberglass around a tube in the middle of the night was not what we had imagined a week before, but it was necessary to ensure our rocket passed the Flight Readiness Review.

TANVI GIR: We woke up the following morning after minimal sleep, and it was judgment day, the Flight Readiness Review. Two officials approached us, and the review began. This would come to be the beginning of a 12-hour long battle to prove our rocket safety so that we could launch the next day.

The officials went through a very detailed checklist which all vehicles needed to comply with. During the stressful period, we were able to show the officials the CAD designs of parts in Fusion 360 and simulations to demonstrate the integrity of each component.

Being able to collaborate and run simulations on the cloud help us to pass our designs through this intense grilling. 12 hours following the beginning of the review, standing outside the paddock with our rocket, the officials finally shook our hands, and they gave us the green light to launch. The team worked through the night once again to make final preparations for the next day.

CHARLIE AVELINE: This was the moment launch. Day was here. Fueled by adrenaline and anticipation, we packed the rocket in our van and traveled to the military base where the launch would take place. After we received the green light from the officials, we began the long walk down to the rail.

As we walked, quiet thoughts ran through our heads, as many possible outcomes played out. We spent years working on this rocket and, it all came down to this one moment, all our hard effort and work, all in this one moment.

With the rocket on the rail ready to launch, we waited for the countdown. We held our breath as the countdown began. When the countdown hit zero, our rocket accelerated off of the ground and shot straight up into the sky. Relief filled our hearts. Our hard work had paid off. All of those long days in the workshop and late nights all became worth it in that one moment.

Cheering it on, it ascended up into the sky and eventually reached the peak of its flight. This was the moment of truth. We waited as time seemed suspended. The rocket needed to split. The parachutes needed to come out, but unfortunately, this never happens, and the rocket began to fall back towards the ground. Eventually, it plummeted into the ground over 100 meters per second.

KIRAN DE SILVA: Although our rocket did not come back in one piece, we were still thrilled from the adrenaline rush of seeing it soaring into the sky. Experience over that week had tested our resilience, creativity, and ingenuity. It had built us into better engineers and was the beginning of better things to come.

TANVI GIR: EuRoC taught us a lot about how we can improve. We have set our sights on this year's edition of EuRoC to take place in October. This year was all about eliminating the mistakes of the past and building an even more impressive rocket Sporadic Impulse. Standing at over 5 meters tall and incorporating our very own student-developed hybrid engine, this is a massive step forward for us.

[MUSIC PLAYING]

CHARLIE AVELINE: Modularity and accessibility was a key feature of this year's rocket. Fusion 360 allowed us to design a completely new and innovative airframe from the ground up in a matter of months. The new internal structure allows for improved accessibility and a stiffer design, which has eliminated the bending issues of the past.

We also made our first composite parts this year, with the whole of the external airframe being made out of an advanced carbon fiber and fiberglass skin. This should hopefully make our rocket lighter, stiffer, and stronger.

KIRAN DE SILVA: Sporadic Impulse is controlled by the most advanced avionics system we have ever designed. A complex control system manages the engine's thrust while calculating the rocket's current velocity and position to ensure it hits its three kilometers as accurately as possible.

To enable more interesting research, a scientific payload on Sporadic Impulse will be deployed from the rocket at Apogee. The main experiment on board the payload integrates both traditional, flexible solar panels and novel, fabric solar panels onto the parachute. The goal is to try to characterize the performance and investigate the viability of using solar-powered parachutes as a power source for the payload.

The propulsion system for our rocket this year is a custom designed and manufactured throttleable hybrid engine called Hypnos. Three is in the making. It is capable of producing over 450 pounds of force. Our engine uses a solid paraffin wax as the fuel, not too dissimilar to that found in candles, and a nitrous oxide oxidizer. The oxidizers stored in a tank at high pressure, and is released into the combustion chamber, where it burns with the paraffin.

Designing our own rocket engine has not been easy, and the team has been busy testing and fine tuning the performance of the engine to make it as powerful and as reliable as possible. Our efforts culminated in a full test fire of the rocket last month as we prepared to send the rocket to this year's edition of EuRoc.

TANVI GIR: We have continued to incorporate Fusion 360's generative design into this rocket, with two key components being metal 3D printed to allow for the more sophisticated mass saving geometries. Compared to the conventional design parts, we were able to create a 57% mass reduction.

In order to improve the chances of a successful recovery, we also decided to design our own custom mechanical recovery system. That powder is often temperamental and ultimately cost us our rocket last year. Our system this year uses a spring loaded plate to push the rocket apart and eject the parachutes.

Black powder explosives are also heavily regulated here in the UK, so switching to a mechanical system has allowed for a more rapid and more comprehensive testing.

KIRAN DE SILVA: Aside from the flagship rockets, the team has also explored two additional development streams. Firstly, a subset of the electronics team participated in the annual concert competition hosted at Machrihanish Airbase in Scotland. With a limited size constraint, they develop innovative payload designs, which when launched from a rocket land safely while also performing a scientific experiment.

In 2021, they were awarded the Design Award, and this year they were announced as winners of the cancer category, with a cancer testing the initial prototype of the solar panel parachute being launched on the payload for Sporadic Impulse. The hope is that the technologies they develop can eventually be integrated into our flagship rockets.

CHARLIE AVELINE: The second stream of development takes place within the advanced research project subgroup called the altitude record team. As the name implies, their goal is to break as many of the different UK altitude records for various sizes of rockets. They have developed a series of rockets over the last few years, lighter and faster rockets, some of which reach supersonic speeds.

Series of successful launches over the past couple of years culminated in the breaking of the UK L1 altitude record by their Apex rocket a few months ago. They have developed a wealth of experience in high speed flight, and their rockets act as useful test beds for novel subsystems that are intended for use in our flagship rockets.

TANVI GIR: [AUDIO OUT] --that reaches the edge of space. At 100 kilometers, the common line signifies the edge of space and is a massive goal for a lot of student rocketry teams. This target brings with it a whole host of new engineering problems to solve as well as a number of logistical challenges too. But having been part of this team now for four years, I can wholeheartedly say that this is a matter of when, not if.

KIRAN DE SILVA: Right now, EuRoC remains our utmost priority. And while we are here talking to you, work continues back in London to ensure we give ourselves the best possible chance of successfully launching and recovering Sporadic Impulse.

Spaceport America here in the States also remains a goal of the team as we hope to return here later with future bigger and faster rockets. We are so proud to see how far ICOR has come since its inception. And every year, we welcome your new set of budding engineers who will go on to drive the future of the team.

CHARLIE AVELINE: Designing, building, and launching rockets of this scale requires a lot of time and a lot of effort. Given that we are all students and have degrees to work towards in addition to launching rockets, a great deal of planning is required to make sure that we can reach our goals.

It is fair to say that the design of our rockets is as much a managerial challenge as it is an engineering one, but it is something that we all love. Fusion 360 has allowed us to collaborate through a global pandemic while streamlining our workflow and enabling more sophisticated designs.

I hope that today we were able to convey our passion and drive for rocketry, as well as highlighting how Fusion 360 has enabled us to develop lighter rockets faster. Thank you.