PRESS RELEASE: Portal Space Systems Raises $17.5M in Oversubscribed Seed Round to Build Multi-Role, Trans-Orbital Spacecraft Powered by Solar Thermal Propulsion

Bothell,WA - April 1, 2025 - Portal Space Systems, a Seattle-based space start-up developing next-generation satellite systems, announced today that it has closed an oversubscribed $17.5 million seed round to accelerate the development of Supernova, the first multi-role, trans-orbital spacecraft engineered for contested and congested space environments. The round is led by AlleyCorp, with participation from Mach33, FUSE, First In, TFX, Offline Ventures, Atypical, and other strategic investors.

This fundraise will support the first full-scale demonstration of Supernova, including critical design review in Q2 2025, propulsion testing, system integration, and a launch scheduled for mid-2026.

“Our vision is to provide next-gen spacecraft that today’s space operations demand and our nation deserves,” said Jeff Thornburg, CEO of Portal Space Systems. "This funding is a testament to the increasing recognition that maneuverability at will is the critical need in both defense and commercial space operations. Supernova is the first spacecraft to deliver the performance of nuclear thermal propulsion without the burden of launching a reactor. With the support of our investors, we are moving from development to flight, bringing this capability to missions that need it most.”

“Portal Space Systems is introducing a new paradigm of space operations through novel breakthroughs in satellite and spacecraft technologies," said Brannon Jones, investor at AlleyCorp and former engineer at SpaceX. “We were particularly impressed by their Supernova spacecraft, which will improve maneuverability in space by over an order of magnitude, while also significantly extending operational lifespans by enabling a more sustained presence in space."

Milestones Supported by the Funding:

‍Q2 2025: Complete critical design review
Q2 2025: Conduct full-scale propulsion testing of the 3D-printed Hex Thruster
Q4 2025: Begin Supernova system integration
Mid-2026: Launch first demonstration mission

Supernova Capabilities:

‍Supernova is a multi-role, trans-orbital spacecraft, unlocking new mission capabilities across the space domain. Key capabilities include:

• Ultra-high delta-v for sustained maneuvering at will
• LEO to MEO in minutes, LEO to GEO in hours, LEO to Cislunar in days.
• Software-enabled payload flexibility supporting up-to-the-last minute payload swaps and integrations for a variety of commercial and defense customers.
• Compatibility with multiple launch providers giving customers greater flexibility and ensuring more control over mission schedules.
• Radiation tolerance for extended mission life, up to 5 years on orbit.

Thermal Propulsion Without a Reactor‍

‍Supernova uses Portal’s proprietary solar thermal propulsion (STP) system that delivers the performance of nuclear thermal propulsion without requiring a fission reactor. As a result, Supernova achieves the long-range mobility necessary for dynamic space operations at a fraction of the cost, risk, and regulatory challenges of systems with comparable performance. Unlike traditional nuclear thermal propulsion (NTP), which requires launching and operating a reactor into space, Supernova leverages an abundant, naturally occurring heat source, the Sun. Supernova’s STP-powered trans-orbital capability allows it to rapidly shift across mission environments, from Low Earth Orbit through cislunar space, in real time. This superior capability enables currently unprecedented defense, commercial, and scientific missions all from a single, adaptable platform.

Growth Since Emerging from Stealth:

• Printed the world’s first additively manufactured heat exchanger/thruster for a thermal propulsion system
• Opened an 8,000 sq. ft. headquarters in Bothell, WA with in-house propulsion testing infrastructure
• Expanded team with key leadership hires, including:
  
  ⌾ Lt. Gen. Thomas Sharpy (Ret.) – VP, Customer Development (NATO Allied Command Transformation, US Air Force)
  ⌾ Mark Bitterman – VP, Government Affairs (Formerly Stratolaunch, United Launch Alliance (ULA), Orbital Sciences Corporation)
  ⌾ Diego Arias – Engineering Director (Formerly Kuiper, Starlink)
  ⌾ Meghan Ostermann – Sr. R&D Engineer (Formerly SpaceX, Helion, Kuiper, Microsoft)
  ⌾ Petros Petros – Sr. Product Design Engineer (Formerly Meta AR Orion Glasses)
  ⌾ Neil Baleva – Director, Supply Chain & Procurement (Formerly Stratolaunch, Amazon, Crane Aerospace)
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• Completed the Supernova Interim Design Review
• Secured an additional $2M in government funding

"Jeff’s track record pioneering propulsion at SpaceX, Stratolaunch, and Kuiper gave us early confidence in Portal,” explains return investor, Mach33 Financial Group’s CEO, Aaron Burnett, “But the team’s rapid transformation of technical breakthroughs into staggering customer demand sealed our decision to double down this round."

Portal is preparing to scale production to support a fleet of Supernova spacecraft following the first demonstration mission in mid-2026.

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