How To Invest In Portal Space Systems

By Daniel Maguire, ACA

Analyst

As an Analyst, Daniel primarily supports ARK’s Autonomous Technology and Robotics strategy.

Self-Directed Investors have historically had limited access to private companies like Portal Space Systems before they go public. All US investors can download the SoFi or Titan app and, with as little as $500, invest in a portfolio of private and public companies through the ARK Venture Fund.

Leveraging Falcon 9’s partial reusability, SpaceX has cut launch costs by ~95%, from ~$15,600/kg to under ~$1,000/kg in the 17 years since 2008, completing 165 orbital flights in 2025.¹ ARK’s research suggests that Starship can extend that trajectory to $100/kg at scale with a rapidly-reusable, launch-capable rocket. As declining launch costs drive a dramatic increase in the number of satellites in orbit, in-space mobility that can reposition payloads, service assets across orbital regimes, and dispose of debris on compressed regulatory timelines becomes increasingly important. Portal Space Systems is building high-mobility spacecraft to undertake those operations, and ARK believes the company's solar thermal propulsion (STP) architecture positions it to compete effectively in the emerging orbital transfer vehicle (OTV) market.

Portal's core technology concentrates sunlight to heat a propellant, generating thrust at specific impulse² levels that exceed conventional chemical systems while delivering far more responsive maneuvers than electric propulsion. Independent NASA evaluations have documented solar thermal propulsion concepts that produce specific impulse in excess of 800 seconds, well above the 300-second range typical of chemical thrusters.³ In our view, that performance profile serves missions where electric propulsion is too slow and chemical propulsion too costly per maneuver, including time-sensitive defense repositioning and multi-orbit commercial transfers.

That performance envelope maps directly to defense applications. The U.S. Department of War (DoW) released its first Commercial Space Integration Strategy in 2024,⁴ and the U.S. Space Force (USSF) Commercial Space Strategy explicitly prioritizes "speed to fielding" as a procurement criterion.⁵ In 2024, Portal was awarded a $45 million contract under SpaceWERX's Strategic Funding Increase (STRATFI) program—a U.S. Space Force initiative that matches government and private capital to accelerate commercial technology toward military adoption—to build, demonstrate, and scale-manufacture its first Supernova vehicle.⁶ On the commercial side, the U.S. Federal Communications Commission's (FCC) 5-year post-mission disposal rule, adopted in 2022, replaced a 25-year guideline and created binding demand for active debris management.⁷ We view debris removal as an early recurring-revenue wedge that could anchor commercial operations while defense contracts scale.

Portal's execution milestones support our thesis. Co-founder and CEO Jeff Thornburg previously led SpaceX's propulsion engineering department and architected the Raptor engine, lending deep hardware-execution credibility to an early-stage propulsion company. The company launched its Mini-Nova technology demonstration payload on SpaceX Transporter-16 in March 2026, validating the avionics stack that will fly on its two operational vehicles. Those vehicles, Starburst and the larger Supernova, are designed to maneuver rapidly in orbit for surveillance, in-space servicing, and debris disposal, with the first Starburst due to launch on SpaceX's Transporter-18 mission as early as October 2026 and the first Supernova expected to fly in 2027.⁸

While the early flight heritage is promising, the primary risks relate to whether Portal's STP advantage fails to translate into measurable mission-time or cost-per-maneuver superiority once demonstrated in orbit, and to whether demonstration missions slip and delay validation.

Portal Space Systems aligns with ARK's long-term conviction that declining launch costs are enabling an entirely new layer of space infrastructure. ARK's research on SpaceX documents how reusable rockets collapsed the cost of reaching orbit; Portal targets the next constraint in that value chain, the cost and speed of moving between orbits once there. With a funded manufacturing scale-up, government transition awards that compress the path to production, and a free-flying demonstration mission months away, the company has reached a stage at which on-orbit data will either confirm or challenge the STP performance thesis. The ARK Space & Defense Innovation ETF (ARKX) reflects the broader conviction that the convergence of reusable rockets, autonomous systems, and defense innovation is restructuring how capital flows into space. Portal represents a direct expression of that convergence at the venture stage, where ARK believes the risk-reward profile is compelling.

Important Information  

We offer our view of Portal Space Systems because it is part of the total ARK Venture Fund portfolio. To see the most updated portfolio, please visit here. Holdings subject to change. Not a recommendation to buy, sell, or hold any specific security. 

BEFORE INVESTING YOU SHOULD CAREFULLY CONSIDER THE FUND'S INVESTMENT OBJECTIVES, RISKS, CHARGES AND EXPENSES. THIS AND OTHER INFORMATION IS IN THE PROSPECTUS, A COPY OF WHICH MAY BE OBTAINED HERE 

There is no assurance that the Fund will meet its investment objective. The value of your investment in the Fund, as well as the amount of return you receive on your investment in the Fund, may fluctuate significantly. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. Therefore, you should consider carefully the risks at the bottom of this page before investing in the Fund. 

ARK Investment Management LLC is the investment adviser to the ARK Venture Fund. 

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