Jan 8, 2026 · 15m · y-combinator
Inside The Startup Building Reusable Rockets · Y Combinator
gold bands on the timeline = statements, start to end. Hover to read, click to jump. CC turns on captions
In this Y Combinator 'HARD TECH' feature, host Aaron Epstein tours Stoke Space in Kent, Washington, where co-founders Andy Lapsa and Tom Feldman showcase their mission to build fully and rapidly reusable rockets. The video explores how Stoke Space aims to revolutionize the space economy by overcoming upper-stage atmospheric reentry challenges through rapid prototyping, vertical integration, and innovative launch architecture.
How this conversation actually went
Every chapter scored 0–10 on four independent dynamics. Hover any point for the reasoning behind the score. How this is scored →
speaking balance: gold is the partners, purple is the guest (3 minute bins)
Tom frankly dismisses the 150 competing rocket startups of 2019 as unviable PowerPoint pitches that lacked real hardware grounding.
Hardest push from the partners ▶ 5:20 Host presses founders on facing 150 competitorsAaron presses the founders on why they believed they could outcompete more than 150 existing rocket companies in a crowded field.
Biggest teaching moment ▶ 2:19 Andy details the bottleneck of non-reusable upper stagesAndy educates the host on how throwing away expensive second-stage rockets restricts launch capacity across the entire space economy.
The partners hold their own ▶ 2:59 Host explains Andromeda capsule re-entry mechanicsAaron demonstrates deep research by walking through the specific technical mechanics of the liquid hydrogen heat exchanger and thrusters during atmospheric re-entry.
the scores for every segment, with the reasoning behind each
| Chapter | Topic | The partners as informed peer | Guest teaching | Guest disagreement | The partners pushing back | Why |
|---|---|---|---|---|---|---|
| Unlocking Space Economy Potential | 4 | 6 | 0 | 0 | Aaron introduces Stoke Space's mission to achieve complete rocket reusability. Andy and Tom explain the technical limits of current partial reusability and how their hydrogen-cooled second stage heat shield solves atmospheric re-entry. | |
| Tom Feldman's Early Passion for Propulsion | 3 | 4 | 1 | 0 | The founders detail leaving Blue Origin with young families to start Stoke Space. Tom dismisses the flood of competitor rocket companies at the time as mostly PowerPoint concepts lacking hardware viability. | |
| Backyard Container Testing and First Engine Firing | 2 | 5 | 0 | 0 | Andy and Tom describe welding and building their first hydrogen-oxygen test thruster inside a backyard shipping container. Andy recounts their initial difficulties fundraising as a hardware startup during early COVID lockdowns. | |
| Factory Tour: 168,000 Sq Ft Manufacturing Hub | 3 | 5 | 0 | 0 | Touring their 168,000 sq ft Kent manufacturing facility, Andy explains why in-house manufacturing is essential to compress failure-analysis and iteration cycles from a month down to one or two days. | |
| Proprietary Software Infrastructure and Boltline | 3 | 5 | 0 | 0 | Andy explains how rapid reusability requires building internal software like Boltline to automate maintenance tracking and scale compliance from garage builds to orbital FAA standards. | |
| Future Vision and Ultimate Conviction | 2 | 3 | 0 | 0 | The founders reflect on their ultimate goal of achieving daily flights and their core conviction that full reusability had to be attempted. |