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York Space Systems (NYSE: YSS) has entered into a definitive agreement to acquire Solestial, Inc.

York Space Systems to acquire Solestial, securing critical space solar capability with u.s.-based manufacturing. DENVER - May 19, 2026 - York Space Systems (York) (NYSE: YSS), a leading, US-based national defense and commercial prime providing a comprehensive suite of mission-critical solutions, today announced it has entered into a definitive agreement to acquire Solestial, Inc. ("Solestial"), a leading provider of next-generation space solar technology. The acquisition secures a critical space solar capability within York's supply chain through U.S.-based manufacturing, strengthening control over a key subsystem while reducing reliance on Chinese-controlled materials and manufacturing. Upon closing, Solestial will operate as a wholly owned subsidiary of York, continuing to serve customers across commercial, civil, and national security markets. "York has consistently invested in U.S.-based manufacturing as a core part of how we deliver for our customers," said Dirk Wallinger, CEO of York. "This acquisition builds on that approach, strengthening our supply chain by investing in a proven U.S. company, supporting the domestic industrial base, and reducing reliance on foreign sources for critical materials and manufacturing." Solestial has developed a differentiated approach to space solar, producing ultrathin, radiation-hardened silicon solar cells and modules engineered specifically for the space environment. Solestial is the only space solar provider with self-healing silicon technology proven on orbit, enabling performance while maintaining a path to high-volume manufacturing. As demand for power in space accelerates, the industry faces a growing gap between mission requirements and available, scalable solutions. Legacy III-V solar solutions remain expensive and capacity constrained, with lead times exceeding two years, while terrestrial silicon alternatives are not designed for space and degrade rapidly under radiation exposure. Both approaches also depend heavily on Chinese-controlled materials and manufacturing, creating supply chain risk for critical missions. "Solestial has proven a scalable, space-optimized solar technology that is designed to perform in ways legacy and terrestrial solutions cannot," said Mike Lajczok, CTO of York. "That will give us the ability to build more capable platforms with better performance, lower cost, and greater design flexibility." Headquartered in Tempe, Arizona, Solestial has established a growing U.S. manufacturing footprint and is advancing toward a fully domestic supply chain. With approximately 95 percent of its supply chain already based in the U.S. and a clear path to full domestic production, the company is uniquely positioned to scale manufacturing in support of growing demand. Solestial recently expanded its production capabilities through the acquisition of advanced high-volume solar manufacturing equipment, enabling wafer-to-module manufacturing in the U.S. "Solestial was founded to solve the space power bottleneck," said Margo de Naray, CEO of Solestial. "Our customers need a solution that can scale, perform in space, and be manufactured reliably. Partnering with York allows us to accelerate all three; expanding production, deepening technical integration, and delivering a resilient, American-made capability to a broader set of missions." The acquisition represents a strategic step toward selectively integrating critical subsystems, strengthening York's control over key capabilities while improving manufacturing reliability, scalability, and cost efficiency. Solestial will continue to serve as a trusted supplier to the broader ecosystem. The consummation of the acquisition of Solestial is subject to regulatory approvals and customary closing conditions and is expected to occur in the second quarter. About York Space Systems York Space Systems (NYSE: YSS) is a leading, U.S.-based national defense and commercial prime providing a comprehensive suite of mission-critical solutions for national security, government, and commercial customers. York is one of the only space and defense primes with proprietary hardware and software capabilities designed to address customers' complex mission requirements across the critical elements of the entire space ecosystem throughout the mission lifecycle. York is purpose built to address evolving national security space challenges and to adapt to the ongoing shift in the U.S. government's mission needs and procurement processes. About Solestial Solestial exists to deliver abundant energy in space. The company's breakthrough technology is a silicon solar cell engineered for space to self-cure radiation damage under sunlight at operating temperatures as low as 65°C. Solestial solar cells are packaged in an ultrathin, low-mass, flexible solar power module designed to withstand up to 10 years in a variety of destinations in space. The flexible solar power modules can be produced on automated machines resulting in costs lower than traditional III-V multijunction solar products. From today's satellite constellations and research projects to tomorrow's lunar settlements and services in space, Solestial's innovative technology represents a paradigm shift for space solar; an affordable, scalable solution to power sustained development. Solestial is a US company manufacturing solar cells and flexible solar power modules in Tempe, Arizona. To learn more, visit the Solestial website and follow Solestial on social media. Forward-Looking Statements This press release contains "forward-looking statements" within the meaning of, and we intend such forward-looking statements to be covered by, the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Forward-looking statements are inherently subject to risks and uncertainties, some of which cannot be predicted or quantified. In some cases, you can identify forward-looking statements by terminology such as "anticipate," "believe," "could," "emerging," "expand," "expect," "feasibility," "intend," "may," "objective," "plan," "potential," "should," "will," "would," or the negative of these terms or other comparable terminology. In particular, statements about the proposed acquisition of Solestial, including satisfaction of closing conditions and timing of consummation, expected benefits of, and opportunities created by, the proposed acquisition, such as control of the supply chain and scaling manufacturing, the future capabilities of Solestial and its capabilities, following the proposed acquisition, market demand, its growth strategy and its expectations, beliefs, plans, strategies, objectives, prospects, assumptions, or future events or performance contained in this press release are forward-looking statements. Factors that could cause actual results to differ materially from those expressed or implied by the forward-looking statements include: failure to obtain regulatory approvals and otherwise satisfy closing conditions to close the proposed acquisition, timely or at all; the occurrence of any event, change or other circumstances that could give rise to the termination of the agreement governing the proposed acquisition; failure to integrate Solestial into the Company following the consummation of the acquisition; failure to realize the expected benefits of the proposed acquisition in the expected timeline or at all; cost overruns on its contracts, including before final receipt of a contract; significant competition in the global space and satellite market; any failure of its spacecraft systems and related software to operate as intended, resulting in warranty claims for product failures, schedule delays or other problems with existing or new products; its revenue, results of operations and reputation may be negatively impacted if its products contain defects or fail to operate in the expected manner; its failure to establish and maintain important relationships with government agencies and prime contractors; the scarcity or unavailability of critical components used to manufacture its products or used in its development programs; disruptions in U.S. government operations and funding and budgetary priorities of the U.S. government; the inability to comply with any of its contracts or meet eligibility requirements to obtain certain government contracts; and the other factors set forth in its filings with the Securities and Exchange Commission. You should not place undue reliance on these forward-looking statements, which speak only as of the date stated, or if no date is stated, as of the date of this press release and the related conference call. Actual results may vary from the estimates provided. Solestial, Inc. undertake no intent or obligation to publicly update or revise any of the estimates and other forward-looking statements made in this press release, whether as a result of new information, future events or otherwise, except as required by law. References and links to websites have been provided as a convenience, and the information contained on such websites is not incorporated by reference into this press release. York is not responsible for the content of third-party websites. Media Contact Sarah Nickell Investor contact Christopher Evenden