We’re excited to launch Valley of Depth, our new podcast taking the place of our beloved (formerly known as) Pathfinder (RIP) podcast.

Valley of Depth is about the technologies that matter—and the people building them. We talk to founders, investors, government officials, and military leaders shaping the future of national security and deep tech. From breakthrough science to strategic policy, we dive into the high-stakes decisions behind the world’s hardest technologies.

In our inaugural episode, EP 001, we’re joined by Bryon Hargis, co-founder and CEO of Castelion, a venture-backed defense startup building affordable, mass-producible hypersonic missile systems for the U.S. and allied militaries. Castelion, founded by former SpaceX engineers, is taking a vertically integrated, fast-iteration approach to strike weapons—redefining how complex defense hardware is built.

In this episode, we unpack the story behind Castelion’s formation, the rising hypersonic threat from China, how startups are challenging the dominance of traditional primes—and much, much more…

• Chapters •

00:00 Intro

00:52 What inspired Bryan to leave SpaceX and start Castelion?

03:06 Non-nuclear deterrence

05:15 How SpaceX's culture influenced Castelion

07:44 Current team size

08:07 Cultural shift in defense hiring

10:04 Hypersonic missile advantages

12:03 US vs China capabilities

13:32 Tradeoffs vs exquisite systems

16:08 What's behind Bryon

18:02 Recent test results

20:54 Iterating safely

24:27 Castelion's DoD buyer

26:56 Navigating defense acquisition

32:11 Championing innovation

35:17 The Golden Dome concept

37:10 Requirements for Golden Dome

39:21 Startups vs primes race

40:49 Scaling missile production timeline

42:48 European market potential

44:19 Competition with defense primes

45:49 Capital requirements

47:26 Company vision

49:13 World impact if successful

50:48 Next milestones

52:14 Story behind the name

• Show notes •

Castelion’s website — https://www.castelion.com/

Bryon’s socials — https://x.com/hargsb

Mo's socials — https://twitter.com/itsmoislam

Payload’s socials — https://twitter.com/payloadspace / https://www.linkedin.com/company/payloadspace

Ignition’s socials — https://twitter.com/ignitionnuclear /

https://www.linkedin.com/company/ignition-nuclear/

Tectonic’s socials — https://twitter.com/tectonicdefense / https://www.linkedin.com/company/tectonicdefense/

Valley of Depth archive — Listen: https://pod.payloadspace.com/

• About us •

Valley of Depth is a podcast about the technologies that matter — and the people building them. Brought to you by Arkaea Media, the team behind Payload (space), Ignition (nuclear energy), and Tectonic (defense tech), this show goes beyond headlines and hype. We talk to founders, investors, government officials, and military leaders shaping the future of national security and deep tech. From breakthrough science to strategic policy, we dive into the high-stakes decisions behind the world’s hardest technologies.

Payload: www.payloadspace.com
Ignition: www.ignition-news.com

Tectonic: www.tectonicdefense.com

Showgirls (1995) and The Hand That Rocks The Cradle (1992)