Poddy the Second: From Idea to Reality
Poddy the Second’s story began after the first SpaceX competition in August of 2017. HYPED had completed their first SpaceX competition and, for the first time in a year, had the intention to start from fresh to design something new with the skill and insight they had gained during the creation of Poddy McPodface. And so, with the ambitious nature that is now very easily attributed to members of HYPED, they started to list out their aspirations for the future design: Magnetic propulsion, carbon fibre structure, pressurised passenger cabin, and more.
Designing Poddy the Second
Designing and planning Poddy the Second took place between September 2017 and February 2018. HYPED’s technical team, which designs and manufactures Poddy, is divided into sub-teams that focus on general aspects of Poddy: Dynamics, Power, Software, Static and Simulations.
From the project’s inception, the Static team worked with a design philosophy aimed at making a scalable hyperloop prototype that could comfortably seat a passenger while travelling at high speed in a vacuum tube. To achieve these goals, the material choice was paramount. After various materials were ruled out due to cost or strength, the team turned to something that nobody had any experience of working with; carbon fibre. What followed over the next few months was a baptism of fire in the endless, complex manufacturing processes that working with carbon fibre entails. The manufacturing process began back in April with mould fabrication for crucial parts such as the chassis, the pressure vessel and the dynamic plates which would support most of the dynamic systems. The end hatches provided one last challenge with their design; however, the now-experienced Static team easily overcame these issues.
The Power team designs the high and low power systems for Poddy. These systems power the propulsion wheels and the control electronics, respectively. Each system consists of battery packs, switching and fusing components, and power conversion electronics. A system that can safely deliver the required 360 kW of power for the entire length of the run was developed, weighing only 80 kg. Finally, the low power system was developed with maximum safety and redundancy in mind - power density became less of an issue, as only up to 300W had to be delivered. Overall, the design of the power systems was a lengthy but rewarding process of searching the market for every option available and subsequently designing to the expectations of the team and SpaceX.
The Dynamics team focuses on the creation of any and all moving and magnetic parts of Poddy. They are responsible for the design of the magnetic propulsion wheels, levitation skis, emergency braking system and the stability system. The emergency brakes were, naturally, designed with safety as the utmost priority, so we developed a passive self-locking wedge mechanism. Each propulsion Halbach wheel consists of 20 Neodymium-Iron-Boron magnets arranged in what is known as a “Halbach” configuration. Each magnet when spun generates over 45000N of force; so, to hold the magnets in, we wrapped each wheel with one of the strongest synthetic fibres on the planet: Zylon. The creation of Halbach wheels took 9 months and 11 design iterations, during which we encountered some of the most thought-provoking challenges that HYPED has ever faced.
The Software Team is responsible for the design and development of all software systems involved in the operation of our Hyperloop pod – this encapsulates an eclectic range of systems. The team developed sophisticated navigation algorithms which serve to calculate the pod’s navigational parameters – such as velocity, acceleration, and displacement – in the Hyperloop in real time. These calculations were performed with data captured by a plethora of sensors. The team also developed a motor-control system to handle acceleration control and communication and telemetry systems to provide Poddy with a voice to the outside world. In order to test their systems, the Software Team developed a ‘virtual hyperloop’. This virtual hyperloop employs fictitious sensor data which emulates the behaviour of our sensors.
The Simulations team works alongside the Static and Dynamics teams to ensure that the engineers’ designs are suitable for the competition. COMSOL Multiphysics software was used throughout the designing of the prototype. For example, once the chassis’ design was finished, the airflow simulation of it in a low-pressure tube was performed which showed negligible drag force. The design was confirmed and the Static team were able to begin manufacturing. The biggest challenge that was faced was associated with the propulsion system, as the vibrational backgrounds needed to be, and were, confirmed to be within safe limits. The simulations team also optimises the physical geometries of the designs to minimise the amount of material used.
Bringing Poddy over from Edinburgh to Hawthorne, California was a feat in itself; every subsystem needed to be shipped 5000 miles across the Atlantic and mainland US while ensuring that appropriate safety measures are taken to transport the magnetic and power systems. After ten months of sheer tenacity in the face of countless engineering challenges, Poddy the Second was finally on its way to California. Our job at SpaceX was to put the final touches on Poddy and pass all the tests that SpaceX set forth. One by one, our main tests got approved: Safety briefing, mechanical fit check, structural inspection and the battery inspection. Soon after completing the first tests and to the mutual elation of all HYPED members, Poddy the Second was shortlisted among the six top teams.
The design of Poddy the Second was a milestone in the development of scalable Hyperloop prototypes. It was the only Pod to feature a plethora of the subsystems that we may one day see in a real Hyperloop. Our design philosophy is not just to do well in SpaceX’s competition, but to create technological precursors to what we believe is a revolutionary field. We, as enterprising students of STEM and members of a top 6 Hyperloop team endeavouring to better connect the people of Earth, are incredibly proud of our accomplishments and will continue to stay HYPED in the year to come.
Authors: Anirudh Vasudevan, Neil Buchanan, Daniel Toth, Jack Gargan, Arturas Jocas