2017–2025 / Cambridge
Eight years of building and learning.
From my BA and MEng to a PhD on non-rigid linkages, Cambridge is where I developed the research behind the structures on this site.
Explore the research ↗Founding engineer · Beyond Reach Labs
Charles Gai
I design deployable structures for space, and research how one structure can hold several stable shapes.
SpaceX · 2022–23
Cambridge PhD · 2025
New York City
Connected by design
01 / Background
From a solar car to orbit
I’m a structural and mechanical engineer. I did my PhD at Cambridge and worked on Starship and Starlink at SpaceX. Now I design deployable structures for space at Beyond Reach Labs in New York.
Education and experienceCambridge, SpaceX and student projects
- 8 yrsat Cambridge: BA, MEng and PhD
- 2SpaceX teams: Starship and Starlink
- 628 kmdriven in Helia during the World Solar Challenge
- 1,000+members in the design society I co-founded
Education
- 2021–2025PhD, Engineering — On Non-rigid Linkages University of Cambridge, Advanced Structures Group, Trinity Hall. Three papers in Proceedings of the Royal Society A.
- 2017–2021BA & MEng — Structural, Mechanical and Materials Engineering University of Cambridge. Merit.
Work
- NowFounding engineer, Beyond Reach Labs Deployable structures for space. New York City.
- 2023SpaceX — Starlink satellite solar array Associate Engineer. Array mechanism and deployment.
- 2022SpaceX — Starship launch tower Associate Engineer. Tower structures.
Internships & student teams
- 2019–2025Cambridge University Design Society — co-founder Grew it to more than 1,000 members.
- 2020Neri&Hu — intern architect Shanghai. Drawing and detailing.
- 2019Siemens — QA intern Testing NX and Teamcenter, its CAD and product-lifecycle software.
- 2017–2019Cambridge University Eco Racing Bodywork lead and roll-cage designer on Helia.
Toolkit
Focus
Deployable space structures, mechanisms and linkages
Analysis
Abaqus FEA, Python, MATLAB, C++
Design
NX, SolidWorks, Fusion, Illustrator
Places and connectionsWork, research and photography
A few points along the way
Experiences & side interests
What I’ve worked on, and what I do outside work.
Select a star to explore. Smaller stars belong to the experience they orbit.
02 / Research
One structure.
Several stable shapes.
Some structures have more than one shape they hold on their own, with no motor keeping them there. This is multistability. It lets us build things that fold for transport, deploy for use or adapt to a new task.
My PhD asks how to design those shapes and the motion between them. I start with geometry: which shapes do the bar lengths and joints allow? Elasticity then shows where the structure can settle. The papers below turn this into a design method for linked frames.
- 1spring-like bar in the example below
- 6stable shapes in this example
- 3papers in Proceedings of the Royal Society A
Between geometry and motion
Try a mechanism
Explore the mechanisms behind the papers. Drag a bright joint along its compatible motion, choose a stable shape, or see how two frames share a connection.
Read the explanation ↓Part I, case (b): six zero-energy shapes on the sampled motion path.
Stable shape 1 / 6Part I · case (b)
Arrow keys explore; Enter settles.Drag the bright joint, or tap a shape. Geometric motion, not a force-response simulation.
Connect a second frame
Frame A (white) and frame B (teal) share the highlighted rigid edge. Frame B is uniformly scaled to match that connection. Move frame A above, or change frame B below.
Each frame keeps its own elastic link. This ideal geometric assembly does not check collisions or model actuation between disconnected branches.
How the mechanisms workFilms, energy plots and connected frames
How one frame holds six shapes
Start with a rigid frame: in the ideal model, its bars allow no change of shape. Remove one bar and the linkage can move. Put a spring in its place, and the motion gains stable stopping points: here, six shapes where the spring is back at its natural length. Each is a stable state, a shape the frame holds on its own.
Force-controlled model: a small disturbance returns; a larger load switches states. Based on Part I’s energy formulation, with illustrative overdamped settling.
Worked example · Part I, case (b)
One elastic bar · six stable shapes
Snap to state
The energy plot shows how much energy the spring stores. The shape map follows the same movement using three measurements of the frame, rather than its position in space. Pick a numbered shape, here or on either plot, to explore it; both markers follow the motion. You can also drag the mechanism in the corner.You can also drag the mechanism above.
Connect frames, and the shapes multiply
A larger structure can be built from these smaller frames. When the connections let each frame keep its own stable shapes, their combinations multiply. The idealised chain below adds one frame at a time: 6 × 6 × 6 × 2 = 432 possible stable combinations. In a physical design, some may be blocked by parts touching.
1 frame · 6 shapes
6
stable combinations
The papers
Building multi-stable structures based on Baranov truss, a three-part series with Keith Seffen in Proceedings of the Royal Society A. Open one for a short summary.
Other papersA conference paper, a book chapter and my thesis
03 / Projects & photography
Selected projects
A solar car, an AI prototype and four product design concepts. Open a project to see the work.
Off the clock
Photography
Six series, edited down to the frames I’d print.
1 / 3
04 / Thoughts
What I’m reading
Passages I’ve saved and reposted on Substack, newest first.
05 / Contact
Get in touch
Building something that has to fold, deploy or hold more than one shape? I’d like to hear about it.