While a fusion reactor can't be built in three months, YC pushes hardware and deep tech founders to create a tangible Minimum Viable Proof. This forces them to de-risk the venture by hitting a critical milestone, such as building a small-scale desert prototype or securing key letters of intent, proving traction on a non-obvious timeline.

Unlike software, where customer acquisition is the main risk, the primary diligence question for transformative hardware is technical feasibility. If a team can prove they can build the product (e.g., a cheaper missile system), the market demand is often a given, simplifying the investment thesis.

Instead of building its final passenger jet, Boom first developed a smaller, sub-scale prototype to prove its Mach 2.2 technology. This startup-like, sequential approach proves the core concept at a much lower cost, making the capital-intensive project more manageable and fundable.

Unlike SaaS startups focused on finding product-market fit (market risk), deep tech ventures tackle immense technical challenges. If they succeed, they enter massive, pre-existing trillion-dollar markets like energy or shipping where demand is virtually guaranteed, eliminating market risk entirely.

Fusion reactors on Earth require massive, expensive vacuum chambers. Zephyr Fusion's core insight is to build its reactor in space, leveraging the perfect vacuum that already exists for free. This first-principles approach sidesteps a primary engineering and cost hurdle, potentially making fusion a more commercially viable energy source.

After massive cost overruns on traditional nuclear projects, no utility will build a Small Modular Reactor (SMR) alone. The only viable path forward is for a tech giant to provide both a purchase agreement for the power and direct equity investment in the SMR manufacturer to fund capital expenditures.

Base Power's founder identified the energy sector as ripe for disruption by pattern-matching. Like autos before Tesla or aerospace before SpaceX, energy was a massive, incumbent-dominated field that was not yet technology-focused, R&D-driven, or engineering-led.

Afeyan distinguishes risk (known probabilities) from uncertainty (unknown probabilities). Since breakthrough innovation deals with the unknown, traditional risk/reward models fail. The correct strategy is not to mitigate risk but to pursue multiple, diverse options to navigate uncertainty.

For deep tech startups lacking traditional revenue metrics, the fundraising pitch should frame the market as inevitable if the technology works. This shifts the investor's bet from market validation to the team's ability to execute on a clear technical challenge, a more comfortable risk for specialized investors.