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As filed with the U.S. Securities and Exchange Commission on May 20, 2026.

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Registration Number 333-

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM S-1

REGISTRATION STATEMENT

UNDER THE SECURITIES ACT OF 1933

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Deep Fission, Inc.

(Exact name of registrant as specified in its charter)

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2001 Addison Street, Suite 300

Berkeley, California 94704

(707) 400-0778

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Elizabeth Muller

President and Chief Executive Officer

2001 Addison Street,

Suite 300

Berkeley, California 94704

(707) 400-0778

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

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From time to time after this registration statement is declared effective.

(Approximate date of commencement of proposed sale to the public)

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box. ☐

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

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If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Exchange Act. ☐

The registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, as amended, or until this Registration Statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

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The information in this preliminary prospectus is not complete and may be changed. The securities described in this prospectus may not be sold until the Registration Statement filed with the Securities and Exchange Commission is effective. This preliminary prospectus is not an offer to sell these securities and is not soliciting offers to buy these securities in any jurisdiction where the offer or sale is not permitted.

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SUBJECT TO COMPLETION, DATED MAY 20, 2026

PRELIMINARY PROSPECTUS

6,000,000 Shares

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Deep Fission, Inc.

Common Stock

Deep Fission, Inc. (“Deep Fission”, the “Company”, “we”, “our”, or “us”) is offering 6,000,000 shares of our common stock, par value $0.0001 per share (our “common stock”).

There is not currently, and there has never been, any established public trading market for our common stock and this will be our first listed public offering. We have applied to list our common stock on the Nasdaq Global Market (“Nasdaq”) under the symbol “FISN”, and we will not consummate this offering of our common stock unless our common stock is approved for listing on Nasdaq.

We anticipate a public offering price between $24.00 and $26.00 per share of our common stock offered hereby. The public offering price of the shares of our common stock offered hereby will be by agreement between us and the representatives of the underwriters (the “Representatives”), and may not be indicative of the price at which shares of our common stock will trade in the public market after this offering.

We are an “emerging growth company” and a “smaller reporting company” as defined under the federal securities laws and, as such, have elected to comply with reduced public company reporting requirements. See “Prospectus Summary - Implications of Being an Emerging Growth Company and a Smaller Reporting Company.”

Investing in our common stock involves a high degree of risk. See “Risk Factors” beginning on page 32 to read about factors you should consider before buying shares of our common stock.

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Neither the Securities and Exchange Commission (the “SEC”) nor any state securities commission has approved or disapproved of these securities or passed upon the accuracy or adequacy of the disclosures in this prospectus. Any representation to the contrary is a criminal offense.

(1)See the section titled “Underwriting” for additional information regarding underwriting compensation.

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This offering is being conducted on a firm commitment basis. The underwriters are obligated to take and pay for all the shares of common stock offered by this prospectus if any such shares are taken.

We have granted the underwriters the option, solely to cover over-allotments (if any) in this offering, to purchase up to 900,000 additional shares of our common stock, at the public offering price set forth above less the underwriting discounts set forth above. The underwriters can exercise this right at any time and from time to time, in whole or in part, within 30 days after the date of this prospectus.

At our request, the underwriters have reserved up to 300,000 shares of our common stock, or 5% of the shares offered hereby, for sale at the public offering price, through a directed share program to our directors, officers, certain of our employees and other individuals we identify. For more information on our directed share program, see “Underwriting—Directed Share Program.”

Delivery of the shares of common stock will be made on or about    , 2026 through the book-entry facilities of The Depository Trust Company.

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The date of this prospectus is      , 2026

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ABOUT THIS PROSPECTUS

General

We and the underwriters have not authorized anyone to provide any information or to make any representations other than those contained in this prospectus or any amendment or supplement to this prospectus. We and the underwriters take no responsibility for, and cannot assure you as to the reliability of, any other information that others may give you. This prospectus is an offer to sell only the shares of our common stock offered hereby, but only under circumstances and in jurisdictions where it is lawful to do so.

The information contained in this prospectus is current only as of the date of this prospectus, regardless of the time of delivery of this prospectus or of any sale of shares of our common stock. Our business, prospects, results of operations and financial condition may have changed since those dates.

We and the underwriters have not done anything that would permit this offering or possession or distribution of this prospectus in any jurisdiction where action for that purpose is required, other than in the United States. Persons outside the United States who come into possession of this prospectus must inform themselves about, and observe any restrictions relating to, the offering of the shares of our common stock and the distribution of this prospectus outside the United States.

This prospectus contains forward-looking statements that are subject to a number of risks and uncertainties, many of which are beyond our control. Please read “Risk Factors” and “Cautionary Note on Forward-Looking Statements.”

Basis of Presentation of Financial Information

The Company was incorporated on July 17, 2023, under the laws of the state of Delaware. Surfside Acquisition Inc. (“Surfside”) was incorporated in the State of Delaware on December 10, 2021. On September 5, 2025, pursuant to an Agreement and Plan of Merger and Reorganization (the “Merger Agreement”), a wholly owned subsidiary of Surfside merged with and into Deep Fission Nuclear, Inc. (formerly known as Deep Fission, Inc.), a private Delaware corporation (“Legacy Deep Fission”), with Legacy Deep Fission continuing as the surviving corporation and becoming a wholly owned subsidiary of Surfside. In connection with the transaction, Surfside changed its name to Deep Fission, Inc. Following the consummation of the Merger, the business previously conducted by Legacy Deep Fission became the business conducted by the Company.

For financial reporting purposes, the transaction was treated as a recapitalization and reverse acquisition, with Legacy Deep Fission considered the acquirer for accounting purposes. As such, the historical financial results of Legacy Deep Fission prior to the Merger are considered our historical financial results under applicable accounting principles. Accordingly, the historical financial statements included in this prospectus, for all periods prior to the Merger, are those of Legacy Deep Fission and not Surfside. For additional information regarding the accounting treatment of the Merger or the basis of presentation of the financial statements and related information included herein, see Note 1: Description of Business and Basis of Presentation to our audited consolidated financial statements and our unaudited condensed consolidated financial statements included herein.

Totals and percentages in this prospectus and the Registration Statement of which this prospectus forms a part may be affected by rounding.

Restatement

As previously announced in our Current Report on Form 8-K filed with the SEC on April 9, 2026, on April 9, 2026, the Audit Committee (the “Audit Committee”) of the board of directors, in consultation with management, concluded that the audited consolidated financial statements for the fiscal year ended December 31, 2024 and for the period from July 17, 2023 (inception) through December 31, 2023, and the unaudited condensed consolidated financial statements for the six month periods ended June 30, 2024 and 2025, and the three- and nine-month periods ended September 30, 2024 and 2025 of the Company could no longer be relied upon as a result of material accounting errors identified by management subsequent to the issuance of the Company’s unaudited interim condensed consolidated financial statements as of and for the fiscal quarter ended September 30, 2025. Accordingly, the consolidated financial statements for the year ended December 31, 2024 included elsewhere in this prospectus were previously restated by the Company in order to reflect the correction of identified errors (the “Misstatements”) related to valuations of Simple Agreement for Future Equity (“SAFE Notes”) and stock-based compensation expense (the “Restatement”). For additional information, see Note 2. Restatement of Previously Issued Consolidated Financial Statements and Note 12. Restatement of Interim Financial Information (Unaudited) to our audited consolidated financial statements included elsewhere in this prospectus.

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In connection with the Restatement, the Company also restated certain other financial statements that are not included in this prospectus.

Control Considerations

Our management, with the participation of our Chief Executive Officer and Chief Financial Officer, has evaluated the effectiveness of our disclosure controls and procedures as of March 31, 2026. The term “disclosure controls and procedures,” as defined in Rules 13a-15(e) and 15d-15(e) under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), means controls and other procedures of a company that are designed to ensure that information required to be disclosed by a company in the reports that it files or submits under the Exchange Act is recorded, processed, summarized and reported within the time periods specified in the SEC’s rules and forms. Disclosure controls and procedures include, without limitation, controls and procedures designed to ensure that information required to be disclosed by a company in the reports that it files or submits under the Exchange Act is accumulated and communicated to our management, including our principal executive and principal financial officers, or persons performing similar functions, as appropriate to allow timely decisions regarding required disclosure. Management recognizes that any controls and procedures, no matter how well designed and operated, can provide only reasonable assurance of achieving their objectives and management necessarily applies its judgment in evaluating the cost-benefit relationship of possible controls and procedures.

Based on such evaluation, our Chief Executive Officer and Chief Financial Officer have concluded that our disclosure controls and procedures were not effective as of March 31, 2026 as a result of material weaknesses in internal control over financial reporting. Management will be implementing changes to strengthen our internal controls and remediate the material weaknesses. See “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Material Weaknesses in Internal Control over Financial Reporting” for additional information related to the material weaknesses in internal control over financial reporting and our related remediation activities.

Notwithstanding the identified material weaknesses, management believes that the financial statements and related financial information included in this prospectus fairly present, in all material respects, our financial condition, results of operations and cash flows as of, and for, the periods presented in accordance with U.S. generally accepted accounting principles.

Agreements and Other Instruments

This prospectus and the Registration Statement of which this prospectus forms a part contain summaries of certain agreements and other instruments. Reference is made to the actual agreements and other instruments for complete information, and all of the summaries are qualified in their entirety by the actual agreements and other instruments. Copies of such agreements and other instruments may be filed as exhibits to the Registration Statement of which this prospectus forms a part, and you may obtain copies of those agreements and other instruments as described under “Where You Can Find More Information.” Moreover, such agreements and other instruments are intended to provide you with information regarding the terms of such agreements and other instruments and not to provide any other factual or disclosure information about the Company, its subsidiaries or any other parties to such agreements and other instruments. Such agreements and other instruments may contain representations, warranties, covenants and other agreements by each of the parties to the applicable agreement or other instrument. These representations, warranties, covenants and other agreements have been made solely for the benefit of the other parties to the applicable agreement or other instrument and:

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Market, Industry and Other Data

This prospectus contains estimates, projections and other information concerning our industry and the markets in which we operate, including the markets for nuclear energy and related technologies. Unless otherwise expressly stated, the estimates, projections and other information concerning our industry and the markets in which we operate that is contained in this prospectus is based on management’s knowledge of and experience to date in our industry and the good faith estimates of management. Much of this information consists of forward-looking statements subject to the disclaimers and risks described herein. However, even the historical information is based on estimates, forecasts, projections, market studies or similar methodologies that are inherently subject to uncertainties and assumptions, and actual results may differ materially from those expressed or implied by such information. In addition, the estimates, projections and other information contained in this prospectus, including those based on management’s knowledge of and experience to date in our industry, may rely on inputs from reports, research surveys, studies and similar data prepared by third parties, industry sources and governmental sources that we believe to be reliable. However, we have not independently verified such third-party information and do not make any representation as to its accuracy or completeness.

Industry, market and other data are subject to change and may be limited by the availability of raw data, the voluntary nature of the data gathering process and other limitations inherent in any statistical survey of such data. These and other factors could cause results to differ materially from those expressed in the estimates made by third parties and by us. Accordingly, you are cautioned not to place undue reliance on such market and industry data or any other such estimates.

Trademarks, Service Marks and Trade Names

We own or have rights to use various trademarks, service marks and trade names used in this prospectus and the Registration Statement of which this prospectus forms a part, which are protected under applicable intellectual property laws. This prospectus and the Registration Statement of which this prospectus forms a part may also contain trademarks, service marks and trade names of other companies, which are, to our knowledge, the property of their respective owners. Solely for convenience, certain trademarks, service marks and trade names referred to in this prospectus or the Registration Statement of which this prospectus forms a part appear without the ®, ™ and ^SM symbols, but such references are not intended to indicate, in any way, that we or the applicable owner will not assert, to the fullest extent under applicable law, all rights to these trademarks, service marks and trade names. We do not intend our use or display of other parties’ trademarks, service marks or trade names to imply, and such use or display should not be construed to imply a relationship with, or endorsement or sponsorship of us by, these other parties.

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CAUTIONARY NOTE ON FORWARD-LOOKING STATEMENTS

This prospectus contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”), and Section 21E of the Exchange Act, and is intended to qualify for the safe harbor from liability established by the Private Securities Litigation Reform Act of 1995. All statements contained in this prospectus other than statements of historical fact are forward-looking statements.

Forward-looking statements generally relate to future events or our future financial or operating performance. In some cases, you can identify forward-looking statements because they contain words such as “may,” “should,” “expect,” “intend,” “plan,” “anticipate,” “believe,” “estimate,” “predict,” “project,” “target,” “potential,” “continue,” “could,” “will,” “would,” or similar expressions, or the negative of these terms or similar expressions, although not all forward-looking statements contain these identifying words.

Forward-looking statements contained in this prospectus include, but are not limited to, statements regarding:

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Forward-looking statements involve known and unknown risks, uncertainties and other factors that may cause our actual results, performance or achievements to differ materially from those expressed or implied by the forward-looking statements. Important factors that could cause actual results to differ materially from those in the forward-looking statements in this prospectus include, among other things, the factors summarized below:

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The foregoing does not represent an exhaustive list of factors that could impact the forward-looking statements contained herein or the risk factors that we are faced with. Moreover, we operate in a highly regulated, capital-intensive and evolving industry, and new risks and uncertainties may emerge from time to time that could affect our business, prospects, results of operations, or financial condition.

Forward-looking statements in this prospectus are based on management’s current expectations, estimates, forecasts, projections, beliefs and assumptions and on information available to us as of the date of this prospectus. Although we believe that the expectations reflected in these forward-looking statements are reasonable, we cannot assure you that such expectations will prove to be correct. Forward-looking statements are inherently subject to known and unknown risks, uncertainties and other factors, many of which are beyond our control, that could cause our actual results, performance, developments or achievements to differ materially from those expressed in or implied by the forward-looking statements.

Accordingly, you should not place undue reliance on forward-looking statements. Forward-looking statements speak only as of the date of this prospectus. Except as required by applicable law, we undertake no obligation to update or revise any forward-looking statements to reflect events or circumstances after the date of this prospectus or to reflect the occurrence of unanticipated events.

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PROSPECTUS SUMMARY

This summary highlights certain information about us, this offering and selected information contained elsewhere in this prospectus. This summary is not complete and does not contain all of the information that you should consider before deciding whether to invest in our common stock. You should read and consider carefully this prospectus or any amendment or supplement to this prospectus in their entirety before making an investment decision, including the information set forth in this prospectus in the sections titled “About this Prospectus,” “Cautionary Note on Forward-Looking Statements,” “Risk Factors,” “Business” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” as well as our consolidated financial statements and the notes thereto included elsewhere in this prospectus.

Company Overview

Deep Fission, Inc. (“Deep Fission,” the “Company,” “we,” “our,” or “us”) is a nuclear energy technology company developing a small modular reactor (“SMR”) based on established pressurized water reactor (“PWR”) technology, with novel emplacement in deep boreholes approximately one mile below the Earth’s surface. Our reactor, which we refer to as the Gravity Reactor, will leverage subsurface conditions to support key containment and operating functions, including the use of hydrostatic pressure from a water column within the borehole to support reactor operating pressure and cooling, and the surrounding geological formation to provide structural confinement and shielding. This approach is intended to reduce reliance on large surface containment structures and other safety-related infrastructure associated with conventional nuclear power plants, support faster deployment timelines, improve security, enhance safety, and enable lower capital and operating costs relative to conventional nuclear facilities, while reducing exposure to environmental and other surface-level hazards.

Each 3x3 Gravity Reactor is targeted to produce up to 15 megawatts of electric power output (“MWe”), as further described in “—Our Technology—Reactor Architecture”. Individual reactors may be deployed as standalone installations or grouped in clusters of boreholes at a single site, which may enable longer refueling cycles through coordinated fuel management, staggered refueling schedules and more efficient utilization of shared infrastructure, and support larger installations capable of supplying hundreds and potentially thousands of MWe of generation capacity.

Our commercialization strategy is based on a phased deployment plan designed to move toward commercialization in the next three years. Given that reactor criticality using established PWR technology is well understood, we are prioritizing validation of the hardest and most differentiated parts of our system, to reduce risk earlier and move more directly toward a commercialization outcome. Our key demonstration objectives include drilling to depth at commercial scale, installing and integrating a nuclear system a mile underground, and operating as part of a complete energy ecosystem. Critically, we aim to prove that each of these milestones can be achieved on a timeline sufficient to meet the AI-driven surge in demand for energy. We are currently participating in the U.S. Department of Energy (“DOE”) Reactor Pilot Program and expect to demonstrate our system as part of that program.

The first phase of our phased deployment plan involves engineering validation and proof of concept wells. We have a long-term lease for approximately 100 acres located within the Great Plains Industrial Park in Parsons, Kansas (the “Kansas Site”) and have commenced initial field development activities at the site. As part of this phase, we have already drilled our first data acquisition well to gather real-world data up to 6,000 feet deep. Next, we will demonstrate our ability to drill a commercial-scale borehole and safely deploy a prototype reactor. We continue to advance our reactor design in parallel with these activities, including planning additional drilling activities and conducting related engineering and emplacement work, and we are targeting completion of these activities in the coming months. The balance of this year and into early 2027 will be focused on the delivery of key components for full-system installation, including well casing, our reactor canister, and heat exchanger, as well as LEU fabrication and loading.

The second phase of our phased deployment plan involves DOE authorization and one or more commercial pilot wells. Specifically, subject to DOE authorization, we intend to demonstrate the Gravity Reactor, and to apply for a commercial license with the U.S. Nuclear Regulatory Commission (“NRC”) in the first half of 2027, converting the same pilot reactor to commercial operation. We are working closely with both the DOE and the NRC to align demonstration and licensing, as we are aiming to move these efforts forward together rather than advancing them in sequence.

The third and final phase of our phased deployment plan involves the construction of surface facilities and seeking high-volume commercial licensing for deployment of multiple reactors at a single site through clustered boreholes, and subsequently, at multiple sites. We are targeting as early as 2027 to seek such high-volume commercial licensing with the NRC, and anticipate a one-year lag between the start of construction and revenue recognition.

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Our approach to subsurface reactor deployment is supported by our intellectual property portfolio, which includes issued patents and pending patent applications relating to reactor configuration, deep subsurface emplacement, drilling and casing techniques, thermal-hydraulic performance, instrumentation and monitoring, and other technologies supporting the deployment of underground nuclear reactors. We believe that our intellectual property, together with our engineering expertise and ongoing development activities, supports our competitive position.

Legacy Deep Fission was incorporated in July 2023 and remains in the development stage. The Gravity Reactor remains in conceptual and early engineering stages, and we have not constructed or operated a commercial reactor or generated revenue. Current activities include reactor development, geological evaluation, large-diameter borehole drilling research and development, geothermal testing, safety analysis, regulatory engagement, site development, and commercialization planning.

Our Competitive Strengths

We believe the following competitive strengths position us to commercialize our Gravity Reactor and differentiate it from other nuclear energy solutions, including conventional large-scale nuclear power plants, above-ground SMRs and other advanced reactor concepts currently under development:

Established PWR technology adapted for subsurface deployment: The Gravity Reactor is based on PWR technology, which is the most widely deployed reactor technology in the global commercial nuclear fleet and has been licensed by the NRC for decades. Unlike other advanced reactor concepts currently under development by certain other companies that rely on novel reactor designs (such as sodium-cooled, molten salt or high-temperature gas reactors) or specialty fuels (such as HALEU or TRISO fuel), the Gravity Reactor is designed to utilize standard LEU fuel and conventional PWR fuel assemblies. This approach is intended to reduce technology risk, leverage well-understood NRC licensing pathways for PWRs, and benefit from existing commercial fuel supply chains and operating experience.

Energy transfer to the surface using proven geothermal components and processes: Our design involves transfer of thermal energy from the subsurface reactor to a turbine generator located at the surface using components and processes that have been deployed extensively in the geothermal industry, including conventional steam turbine generator equipment. We intend to leverage established drilling, completion, casing, fluid-handling and heat transfer components, together with surface power generation equipment commonly used in the geothermal and broader power generation industries. This approach is intended to reduce technology development risk for the surface and energy-transfer portions of our system, simplify supply chain qualification, and benefit from a mature base of vendors and operating experience in the geothermal and conventional power generation industries.

Inherent safety features from subsurface emplacement: A column of water approximately one mile deep above the reactor is expected to provide approximately 160 atmospheres of hydrostatic pressure, which is intended to support reactor operating pressure and primary cooling without reliance on the large forged reactor pressure vessels, engineered active emergency core cooling systems with pumps and back-up power, and above-ground reinforced concrete and steel containment structures used in conventional surface-level PWRs. The surrounding geology and depth of emplacement are intended to perform containment and shielding functions that, in conventional above-ground reactors, are provided by engineered surface structures. We believe these features may also reduce certain risks associated with surface-level hazards and public exposure, and may help mitigate the siting challenges that have contributed to project delays and cancellations of conventional above-ground nuclear facilities.

Accelerated speed of deployment target relative to other nuclear energy solutions: We believe that traditional surface-level large-scale nuclear reactors typically require approximately six to ten years from breaking ground to completion, and that above-ground SMRs currently under development are generally expected to require approximately three to four years from breaking ground to completion. By contrast, we are designing the Gravity Reactor with the objective of our later reactor deployments taking as little as approximately six months for a single reactor from commencement of installation activities. This targeted timeline is intended to be supported by drilling-based installation methods that draw on established drilling techniques, factory-assembled and modularized reactor canisters that are lowered into a drilled and cased borehole, and a standardized, replicable site configuration that we believe may streamline construction execution, licensing efficiency and supply chain readiness. Our targeted deployment timelines are subject to a number of factors, many of which are outside our control, including regulatory approvals, drilling performance, supply chain availability, site characteristics and customer requirements, and there can be no assurance that we will achieve them.

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Improving per-reactor unit economics from FOAK 2x2 to NOAK 3x3 deployment: Our deployment plan is designed to transition from our initial first-of-a-kind 2x2 fuel assembly configuration (“FOAK 2x2”) to a larger 3x3 fuel assembly configuration in our later deployments (“NOAK 3x3”), which we believe will help improve per-reactor electric power output, capital efficiency and operating economics. Targeted reactor-level improvements over this transition include (i) increased target electric power output per reactor from up to approximately 8 MWe (FOAK 2x2) to up to approximately 15 MWe (NOAK 3x3), (ii) reduced estimated capital cost of deployment per reactor from approximately $152 million (FOAK 2x2) to approximately $84 million (NOAK 3x3), in each case including initial fuel load, (iii) increased estimated run-rate annual revenue and operating cash contribution per reactor, and (iv) longer targeted refueling cycles, from approximately every six years to approximately every seven to ten years, in each case based on a targeted design life in excess of 40 years. In addition to the transition from FOAK 2x2 to NOAK 3x3, these improvements reflect the benefits of learning-curve efficiencies from earlier deployments, design stabilization, scaled manufacturing, maturation of strategic supplier relationships, process optimization, and reduced customization and rework. The reactor-level estimates set forth above are management estimates, are based on a number of assumptions described in “—Our Technology—Reactor Architecture,” and are subject to significant uncertainty.

Scalable, modular reactor architecture: Each Gravity Reactor in a 3x3 fuel assembly configuration is targeted to produce up to 15 MWe of electric power output. Individual reactors are designed to be deployed as standalone installations or grouped in clusters of boreholes at a single site, which we believe may enable installations capable of supplying hundreds, and potentially thousands, of MWe of generation capacity. We believe this modular and scalable architecture is intended to allow customers to add capacity incrementally to match electricity demand, and to support deployment across a range of end-use markets, including data centers and digital infrastructure, industrial and energy-intensive facilities, utilities and grid-scale generation, and government and defense installations.

Experienced management team and deep bench of nuclear, engineering and operational expertise: We have assembled an executive leadership team and technical and operations workforce with substantial experience in nuclear engineering, regulatory affairs, project development, drilling and completion, supply chain management and finance. Members of our executive leadership team have collectively held senior positions at, or have prior experience with, organizations including NuScale Power, Kairos Power, Deep Isolation, Great River Energy, the Hanford Site and the La Crosse Boiling Water Reactor. Our broader technical and operations team includes engineers and operators with prior experience at organizations including the NRC (including a former NRC reactor engineer), the U.S. Navy nuclear propulsion program, Westinghouse, Holtec, the Tennessee Valley Authority, GE Vernova and Fluor, as well as licensed reactor operators. Our board of directors and expert advisors include senior leaders drawn from government, the national laboratories, the energy industry and academia. We believe the breadth and depth of nuclear, engineering and operational experience across our team provides a substantive foundation for executing our development, licensing and commercialization plan.

The competitive strengths described above, and the other information set forth in this prospectus regarding the development, deployment and benefits of the Gravity Reactor, reflect management’s current expectations and beliefs regarding the Gravity Reactor and our business plan, are forward-looking in nature and are subject to significant risks and uncertainties, including those described under the sections titled “Risk Factors” and “Cautionary Note on Forward-Looking Statements.”

Our Technology

The Gravity Reactor integrates established PWR technology with subsurface emplacement in a borehole environment. The system is designed to deliver reliable electricity at lower expected costs relative to conventional nuclear facilities by reducing surface infrastructure requirements and enabling faster deployment than conventional nuclear power plants, while also limiting exposure to environmental and other surface-level hazards. The design of our technology and associated drilling methods described below remains subject to further development and applicable regulatory approvals.

Reactor Architecture

The Gravity Reactor is based on PWR technology, the most widely deployed nuclear reactor technology in the global commercial nuclear fleet. PWRs use water as both coolant and moderator and have been deployed for decades in commercial power generation.

The Gravity Reactor adapts this established reactor architecture for installation within a deep vertical borehole. The reactor is being designed as a compact unit to be positioned within a drilled and cased vertical borehole at depths of approximately one mile below the Earth’s surface.

The Gravity Reactor is expected to contain all nuclear fuel assemblies, coolant circulation systems, and structural components required to safely sustain controlled nuclear fission and transfer thermal energy for conversion into electricity.

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We currently expect our initial reactor deployment to utilize a 2x2 fuel assembly design (i.e., an arrangement of four fuel assemblies in a square configuration) targeting output of up to approximately 8 MWe per reactor. We selected this fuel assembly design for our initial reactor in order to increase speed of deployment. Over time, we also intend to deploy a reactor with a larger 3x3 fuel assembly configuration (i.e., an arrangement of nine fuel assemblies in a square configuration) targeting output of up to approximately 15 MWe per reactor. We believe the larger 3x3 fuel assembly configuration will improve project economics relative to our initial 2x2 fuel assembly configuration, due to improved neutron efficiency, increased power generating capacity and extended refueling intervals. The following table illustrates our current expectations and targets, as applicable, for these reactor fuel assembly configurations:

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We also expect our later reactor deployments to benefit from the experience and efficiencies gained through earlier deployments, including design standardization, manufacturing learning-curve effects, reduced engineering and development costs, supply chain efficiencies, stronger supplier relationships, and improved deployment execution with reduced customization and rework.

We believe that these experiences and efficiencies gained through earlier deployments, together with the improved project economics from the larger 3x3 fuel assembly configuration, will help us to achieve estimated:

We do not, as a matter of course, make public projections as to future revenues, costs, cash flows or other results. However, management has prepared the estimates of per reactor capital costs, annual cash operating expenses, revenue generation and operating cash contribution set forth above to illustrate certain of the current estimates and assumptions being used internally by management in developing and executing our business model. These estimates are reactor-level conceptual estimates only and do not represent projections of company-wide financial performance or expected consolidated results; there are additional costs and expenses that we will incur that will be included in consolidated results and are not included in these reactor-level conceptual estimates. These estimates were not prepared with a view toward public disclosure or with a view toward complying with the guidelines established by the American Institute of Certified Public Accountants with respect to prospective financial information. In the view of management, these estimates were prepared on a reasonable basis based on information currently available to management; however, these estimates should not be relied upon as being indicative of future results, and potential investors are cautioned not to place undue reliance on these estimates. For example, these estimates are based on a range of assumptions, including relating to our expected pricing, reactor performance and output, market demand and reactor utilization, operating life and performance, deployment scale, project structure, supply chain (including fuel) availability and pricing, operating expenses and regulatory approvals. Among these assumptions are a 40-year design life; that output achieves target levels (i.e., 15 MWe and 8 MWe for 3x3 configuration and 2x2 configuration, respectively); operation as high-utilization baseload assets, with approximately 93% uptime; that PPAs are secured for the entire amount of assumed output, with initial pricing of

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approximately $110 per MWh (which represents our estimate based on a survey of market pricing in certain U.S. markets in 2024); a two-year and one-year development and deployment timeline for 3x3 configuration and 2x2 configuration, respectively; refueling intervals of approximately 7.4 years and 6 years for 3x3 configuration and 2x2 configuration, respectively; that reactor design remains standardized and repeatable; and that deployment conditions remain constant (e.g., deployment in same portion of same site). Moreover, the estimates of annual cash operating expenses, revenue generation and operating cash contribution are averages of such items over a projected ten year period (representing the first ten years of the assumed 40-year design life), based on our estimates of pricing, costs and other amounts as of 2024 with a 3% annual inflation adjustment per year across the forecast period, and the estimates of annual cash operating expenses are management estimates based on third-party publications of industry-wide data. Because our technology is in an early stage of development and has not yet been commercially deployed, there is limited historical data on which management can base these estimates, making it even more difficult to source reliable information and formulate reliable assumptions. Actual results may differ materially from those contemplated by these estimates due to a variety of factors. See “Cautionary Note on Forward-Looking Statements” and “Risk Factors—Risks Related to Our Business and Industry.” 

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Subsurface Deployment

A defining feature of the Gravity Reactor is the emplacement of the reactor within a deep subsurface vertical borehole rather than within a conventional above-ground containment structure. The borehole is expected to be lined with steel casing and cement intended to maintain structural integrity and isolate surrounding geological formations. The reactor will be installed within the borehole, surrounded by a column of water intended to provide external hydrostatic pressure and support cooling. Thermal energy produced within the reactor core will be carried by the primary coolant system to a heat exchanger located in the borehole, where it will be transferred to surface power conversion systems for conversion into electricity. The primary coolant will be a closed system that recirculates through the reactor core and primary heat exchanger.

Subsurface emplacement is intended to provide several safety benefits, including the availability of hydrostatic pressure and water inventory intended to support cooling, geological shielding and separation between the reactor system and the surface environment, reduced exposure to certain external hazards, increased security, and reduced reliance on safety-related surface infrastructure footprint relative to conventional nuclear facilities.

Deep Borehole Drilling

Deployment of the Gravity Reactor is expected to require the construction of 30- to 50-inch-diameter vertical boreholes extending to depths of approximately one mile below the Earth’s surface. Boreholes are expected to be drilled using technologies, service providers, and operational practices developed in the oil, gas, and geothermal industries.

We have already drilled our first data acquisition well to gather real-world data up to 6,000 feet deep. Next, we will demonstrate our ability to drill a commercial-scale borehole and safely deploy a prototype reactor. Our test drilling activities are intended to support evaluation of drilling methods, casing systems, and borehole stability. In parallel, we are conducting engineering studies and modeling activities to refine borehole design parameters, including diameter requirements, drilling techniques, and casing systems.

Reactor Installation and Emplacement

Following completion of borehole drilling and casing, the reactor is expected to be lowered into the prepared borehole using specialized lifting and handling equipment and placed within the casing structure at the designated depth. Surface infrastructure, including monitoring systems, electrical equipment, and power conversion systems, is expected to be connected to the subsurface reactor system. We are conducting engineering studies and modeling activities to refine installation procedures and equipment specifications.

Hydrostatic Pressure and Cooling

The Gravity Reactor incorporates a column of water within the borehole above and surrounding the reactor. The hydrostatic pressure generated by this water column is expected to provide approximately 160 atm of reliable pressure and is intended to support the pressure conditions required for safe reactor operation.

Water within the borehole also serves as the primary coolant. Thermal energy produced within the reactor core will be carried by the primary coolant system to a heat exchanger located in the borehole, where it will be transferred to surface power conversion systems for conversion into electricity.

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Modular Reactor Units

Each 3x3 Gravity Reactor is targeted to produce up to 15 MWe, as further described in “—Our Technology—Reactor Architecture”. Individual reactors may be deployed as standalone installations or grouped in clusters of boreholes at a single site.

Multiple boreholes deployed at a single location are intended to support larger installations capable of supplying hundreds and potentially thousands of MWe of generation capacity. This modular architecture is intended to allow reactor capacity to be added incrementally as electricity demand grows.

Fuel and Core Systems

Nuclear fuel for Gravity Reactors will consist of low-enriched uranium (“LEU”). LEU is produced and fabricated by qualified nuclear fuel suppliers and is more readily available than High Assay Low Enriched Uranium (“HALEU”) fuels. We expect that commercial reactor deployments will require long-term fuel supply arrangements with qualified enrichment, fabrication, and related fuel-cycle service providers. A single reactor is expected to enable longer refueling cycles, potentially up to 10 years between cycles.

The availability or cost of LEU may be influenced by uranium market conditions, enrichment and fabrication capacity, transportation constraints, regulatory requirements, geopolitical factors, or other supply chain disruptions. Global enrichment capacity is concentrated among a limited number of suppliers, including facilities in jurisdictions that may be subject to geopolitical developments, trade restrictions, or regulatory actions, which could affect the availability or cost of LEU.

Within the reactor, nuclear fuel assemblies will sustain controlled fission reactions that generate heat. We currently expect our initial configuration to utilize a 2x2 fuel assembly design (i.e., an arrangement of four fuel assemblies in a square configuration). We also intend to develop a larger 3x3 fuel assembly configuration (i.e., nine fuel assemblies). The design, timing, implementation, and performance of these configurations are subject to technical, regulatory, and other uncertainties. Reactor control mechanisms will regulate the rate of the fission reaction to maintain stable operating conditions.

Like other nuclear reactors, operation of the Gravity Reactor will generate used nuclear fuel, which must be stored and ultimately disposed of in accordance with applicable regulatory requirements and nuclear waste management frameworks. Depending on the long-term disposal pathway, this may require interim on-site storage, transportation, and coordination with governmental authorities or third-party service providers. Our deployment model currently anticipates safe interim storage, pending identification of national, long-term storage solutions. The management and disposition of used nuclear fuel will be conducted in compliance with applicable laws and regulations.

Safety and Reactor Protection

The Gravity Reactor incorporates multiple layers of safety systems derived from established PWR technology and its safety is enhanced by the characteristics of deep subsurface emplacement.

The reactor design includes engineered safety systems intended to regulate reactor operation, remove residual heat following shutdown, and maintain safe operating conditions during both normal operating states, where the reactor is operating under routine operating conditions and planned changes in operating conditions, and off-normal operating states, where the reactor deviates unexpectedly from expected operating conditions (including equipment malfunctions and system disturbances).

Subsurface emplacement of the reactor within a deep borehole is intended to provide physical separation between the reactor system and the surrounding environment. Surrounding geological formations will provide structural confinement and natural shielding, and underground placement is intended to reduce exposure to certain external hazards, such as extreme weather events, earthquakes, wildfires, aircraft impact, potential acts of sabotage or terrorism, or other events that may affect surface facilities.

The safety characteristics of the Gravity Reactor remain subject to ongoing engineering analysis, safety evaluations, and regulatory review as part of our reactor development process and our efforts to obtain requisite licenses from relevant authorities.

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Surface Supporting Systems

Although the reactor is located underground, limited supporting systems are expected to remain on the surface. These systems are expected to include power conversion equipment used to convert thermal energy into electricity, monitoring and control systems for reactor operation, electrical interconnection infrastructure that will connect the facility to the grid or to local power users, and other operational functions associated with the generation and delivery of electricity.

Manufacturing and Supply Chain

The Gravity Reactor is designed to leverage existing industrial supply chains where possible. Major reactor components are expected to utilize established materials and manufacturing processes drawn from the nuclear and broader industrial sectors, while the reactor’s compact and simplified design is intended to enable greater use of standard industrial fabrication methods in place of conventional large-scale nuclear construction practices.

The reactor is designed as a compact unit that may be manufactured in qualified facilities and delivered to project sites for emplacement within drilled boreholes. Fuel installation may occur at a manufacturing facility or at the borehole site, depending on the local environment and regulations around the transportation of a fueled reactor. This approach is intended to support repeatable and controlled manufacturing and assembly environments.

Deep borehole drilling required for reactor emplacement is expected to use technologies, service providers and operational practices developed in the oil, gas, and geothermal industries. Surface power conversion and balance-of-plant equipment associated with the Gravity Reactor are expected to utilize commercially available industrial components.

Site Requirements and Geological Considerations

The Gravity Reactor is designed for deployment in geologic settings that support the drilling and long-term structural stability of deep vertical boreholes. Site selection is expected to focus on optimizing geologic, operational, project development, and regulatory factors.

We have secured a long-term lease at the Kansas Site and have commenced initial site development activities, including geological evaluation, borehole planning, and initial drilling activities. We are conducting geological surveys and site characterization studies at the Kansas Site. These activities are intended to inform borehole design, drilling techniques, and site suitability for future reactor deployment.

In addition to the Kansas Site, we have entered into multiple non-binding letters of intent (“LOIs”) with potential development partners for candidate commercial sites in the United States. These LOIs relate to potential deployment opportunities in Kansas, Texas, and Utah as well as other locations in the United States and internationally.

In addition to geological considerations, deployment sites must be capable of supporting surface infrastructure, as described above in “Surface Supporting Systems.”

Site-specific engineering analyses will be required for each proposed deployment location to confirm drilling feasibility and compliance with applicable regulatory requirements. Such analyses are ongoing with respect to the Kansas Site and are expected to be required for any future deployment locations, including Texas and Utah, if applicable.

DOE Reactor Pilot Program and Development Activities

We are advancing development and demonstration activities to support the future commercial deployment of the Gravity Reactor. Current demonstration efforts are focused on our planned pilot reactor under the DOE Reactor Pilot Program, together with related engineering, site development, and construction of initial boreholes and test infrastructure. The pilot reactor is not expected to reflect the full output, configuration or commercial economics of any future commercial deployments. We have commenced initial field development activities, including test drilling, at the Kansas Site and we continue to advance our reactor design.

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U.S. Department of Energy Reactor Pilot Program

In August 2025, we were selected by the DOE as one of 11 projects across ten companies eligible to participate in the DOE Reactor Pilot Program, which is intended to enable advanced reactor developers to construct and test prototype reactors under DOE authorization to demonstrate technical feasibility, operational performance, and safety characteristics.

On November 17, 2025, we entered into an Other Transaction Agreement for Reactor Authorization (the “OTA”) with the DOE, effective as of November 14, 2025. The OTA establishes the framework under which the DOE will review the safety basis for our planned demonstration reactor, evaluate supporting engineering analyses, and approve certain commissioning and testing milestones prior to operation. If authorized, the demonstration reactor would be constructed and operated under DOE oversight. Data generated through this process is expected to inform our reactor design, safety analysis, and potential future licensing submissions to the NRC. DOE authorization does not permit commercial operation and does not replace the requirement to obtain NRC licenses.

The DOE Reactor Pilot Program is an authorization and oversight program and does not provide direct funding to us under the OTA. Accordingly, we are responsible for funding development, construction, and operation of our pilot reactor and related infrastructure, including our borehole development program. While initial activities, including the drilling and development of our first well (as further described below), are currently funded, subsequent stages of development, including additional boreholes and the planned pilot reactor, are not fully funded and will require substantial additional capital. We expect to seek such funding through equity issuances (such as this offering), debt financings, strategic investments, partnerships, or other arrangements, although there can be no assurance that this offering or any such additional financing will be available on acceptable terms or at all.

We have updated certain previously identified development milestones, including those related to the timing of reactor criticality, to better align with our current development priorities. Given that reactor criticality using established PWR technology is well understood, we are prioritizing validation of the hardest and most differentiated parts of our system, to reduce risk earlier and move more directly toward a commercialization outcome. Our key demonstration objectives include drilling to depth at commercial scale, installing and integrating a nuclear system a mile underground, and operating as part of a complete energy ecosystem. The timing of DOE authorization and related testing activities remains subject to completion of engineering development, regulatory review, and the availability of funding.

Pilot Reactor Site Development

In support of our participation in the DOE Reactor Pilot Program, we have secured a long-term lease for approximately 100 acres at the Kansas Site. We intend to use this site for development and testing activities associated with our borehole development program and planned pilot reactor, subject to applicable regulatory approvals and the availability of sufficient funding.

Current activities at the Kansas Site include geological analysis, engineering design work, borehole planning, and test drilling (including the drilling of our first well (described below)), as well as preparation for subsurface infrastructure development. These activities are intended to support drilling operations, reactor emplacement procedures, and the design and development of associated monitoring and power conversion systems, subject to the availability of capital and continued project development.

Phased Deployment Model

Our commercialization strategy is based on a phased deployment plan designed to move toward commercialization in the next three years. Given that reactor criticality using established PWR technology is well understood, we are prioritizing validation of the hardest and most differentiated parts of our system, to reduce risk earlier and move more directly toward a commercialization outcome. Our key demonstration objectives include drilling to depth at commercial scale, installing and integrating a nuclear system a mile underground, and operating as part of a complete energy ecosystem. Critically, we aim to prove that each of these milestones can be achieved on a timeline sufficient to meet the AI-driven surge in demand for energy. We are currently participating in the DOE Reactor Pilot Program and expect to demonstrate our system as part of that program.

Phase 1

The first phase of our phased deployment plan involves engineering validation and proof of concept wells. We have a long-term lease for approximately 100 acres located within the Kansas Site and we have commenced initial field development activities at the site. As part of this process, we have already drilled our first data acquisition well to gather real-world data up to 6,000 feet deep. Next, we will demonstrate our ability to drill a commercial-scale borehole and safely deploy a prototype reactor. We continue to advance our reactor design in parallel with these activities, including planning additional drilling activities and conducting related engineering and

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emplacement work, and we are targeting completion of these activities in the coming months. The balance of this year and into early 2027 will be focused on delivery of key components for full-system installation, including well casing, our reactor canister, and heat exchanger, as well as LEU fabrication and loading.

While these wells are not regulated by the DOE as part of the DOE Reactor Pilot Program, engineering data will be used to support our request for the DOE’s authorization of the planned pilot reactor as described below.

Phase 2

The second phase of our phased deployment plan involves DOE authorization and one or more commercial pilot wells. Specifically, subject to DOE authorization, we intend to demonstrate the Gravity Reactor, and to apply for a commercial license with the NRC in the first half of 2027, converting the same pilot reactor to commercial operation. We are working closely with both the DOE and the NRC to align demonstration and licensing, as we are aiming to move these efforts forward together rather than advancing them in sequence.

Phase 3

The third and final phase of our phased deployment plan involves the construction of surface facilities and seeking high-volume commercial licensing for deployment of multiple reactors at a single site through clustered boreholes, which may enable longer refueling cycles through coordinated fuel management, staggered refueling schedules and more efficient utilization of shared infrastructure, and support greater aggregate power generation capacity than the pilot installation, and subsequently, at multiple sites. We are targeting as early as 2027 to seek such high-volume commercial licensing with the NRC, and anticipate a one-year lag between the start of construction and revenue recognition.

Commercial deployment of Gravity Reactors will require additional regulatory approvals, including licensing by the NRC, which we are pursuing in parallel with DOE-related activities. We expect that a DOE-authorized pilot reactor will inform key design, operational and licensing considerations for commercial deployment, although subsequent deployments are expected to involve different configurations, site-specific integration activities and additional engineering development. Additional project financing will also be required.

Ongoing Development Activities

In addition to borehole construction, our current activities include reactor design, safety analysis, thermal-hydraulic modeling, regulatory engagement with the DOE and the NRC, and supply chain development for reactor components and drilling operations. The Gravity Reactor remains in conceptual and early engineering stages, and key aspects of the design continue to be refined through ongoing engineering and analysis.

We expect that data generated through these activities will inform continued development of the Gravity Reactor and future regulatory licensing efforts.

Commercial Strategy

Our commercial strategy is focused on deploying Gravity Reactors in markets with rapidly growing electricity demand and increasing need for reliable, affordable baseload power. Our initial commercial focus is on hyperscale data centers and other large power users, and over time may expand to include utilities, industrial operators, and government or defense installations, as described further below in “Target Markets.”

Commercial Gravity Reactor installations are expected to be deployed at sites capable of supporting multiple reactor units installed through clusters of deep boreholes. This modular architecture is intended to allow reactor capacity to be added incrementally as electricity demand grows.

Our business model is designed to generate revenue from (i) project-level equity participation, including indirect participation in project-level cash flows from electricity sales, (ii) one-time upfront revenue, generally expected to be associated with Gravity Reactor deployment and related upfront project development services and (iii) recurring revenue, generally expected to be associated with technology licensing and operations and maintenance services of Gravity Reactor installations, as described in more detail below in “Business Model and Revenue Streams.”

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Strategic Relationships

We have entered into strategic relationships intended to support commercialization of the Gravity Reactor, including relationships focused on digital infrastructure demand, project development, power offtake opportunities, and project-level financing.

In February 2026, we entered into a non-binding memorandum of understanding (“MOU”) with Blue Owl Digital Infrastructure Advisors LLC (“Blue Owl”) to establish a framework for potential collaboration in support of the development and deployment of nuclear energy projects utilizing our technology. The MOU contemplates potential collaboration relating to customer and utility outreach, project development activities, and evaluation of potential power offtake and project-level financing opportunities associated with Blue Owl’s digital infrastructure portfolio and developments.

In connection with execution of the MOU, investment funds affiliated with Blue Owl made an equity investment in us in the amount of $20 million. We also granted Blue Owl non-exclusive rights of first offer with respect to certain potential future power offtake opportunities and project-level financing opportunities, in each case subject to the terms of the MOU and related transaction documentation. The power offtake right of first offer applies to potential future opportunities where a potential data center or similar large-load end user offtake need is identified in our project developments, and the project financing right of first offer applies to potential future project-level financing opportunities originated by us.

The MOU does not require either party to enter into any specific project, power offtake arrangement, financing transaction, or other commercial arrangement unless agreed in separate definitive written documentation executed by the parties. The MOU also does not grant Blue Owl exclusivity with respect to any future projects or require us to consummate any specific offtake or financing transaction.

In November 2024, we entered into a non-binding strategic relationship term sheet with Endeavour Energy, LLC (“Endeavour”) designed to support commercialization of the Gravity Reactor. The contemplated collaboration is intended to facilitate coordinated site development, access to potential data center customers, and joint evaluation of multi-reactor deployments. The relationship framework contemplates potential deployment configurations of up to 1.5 gigawatts of generation capacity at a single location, within a broader potential co-development framework of up to 2 gigawatts across multiple projects.

The Endeavour relationship is governed by a non-binding term sheet and does not create commitments to purchase electricity, finance projects, construct facilities, grant exclusivity, or deploy a specified number of reactors.

We have also established or are pursuing strategic supplier and technical relationships intended to support reactor development, demonstration, manufacturing, and commercialization activities. These relationships include:

Except as otherwise disclosed, these supplier and technical relationships are generally governed by non-binding purchase orders, service agreements, memoranda of understanding, preliminary engagement arrangements, or other limited contractual frameworks. These arrangements may be non-exclusive, subject to future negotiation, contingent on project milestones or regulatory developments, and may not result in long-term commercial supply or deployment arrangements.

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Project Development Model

We expect that many commercial deployments of the Gravity Reactor may be structured as project-level developments in which we participate in the development, ownership, and operation of reactor installations. Under this model, electricity generated by Gravity Reactor facilities may be sold to customers under long-term power purchase agreements (“PPAs”) or similar contractual arrangements; these potential PPAs are more particularly described below in “Project-Level Equity Participation; Electricity Sales.”

We believe that individual projects may be financed using a combination of corporate capital, strategic capital, and project-level financing structures. This project-level development model is intended to enable us to pursue and retain equity ownership in large-scale infrastructure projects while using external financing sources where appropriate to support construction and long-term operation.

In addition to participating in project-level equity and electricity sales, we may provide project development, reactor delivery, integration, and related deployment support in connection with Gravity Reactor installations, as described below in “Upfront Revenue Streams.” We expect that the specific commercial structure of any project will vary, including based on customer requirements, site characteristics, local power delivery infrastructure, financing arrangements, regulatory requirements, and project counterparties.

Great Plains Industrial Park and Early Deployment Sites

A key element of our commercialization strategy is the development of suitable sites capable of supporting early deployments of the Gravity Reactor. One such location is the Kansas Site, where we have secured a long-term lease for approximately 100 acres for site development and related activities. We view this site as an important early location for development of the Gravity Reactor, including pilot reactor activities and evaluation of potential future commercial deployment opportunities.

We have also entered into a non-binding letter of intent with the Great Plains Industrial Park in connection with potential future development activities at the site, which contemplates potential development of up to 2,000 MWe of generation capacity. The Kansas Site offers an established industrial setting and other site characteristics that we believe may support future reactor development activities, subject to applicable regulatory approvals, state and local support, site studies, and project-specific engineering and infrastructure considerations.

In addition to the Kansas Site, we have entered into multiple non-binding LOIs with potential development partners for candidate commercial sites in the United States. These LOIs relate to potential deployment opportunities in Kansas, Texas, and Utah as well as other locations in the United States and internationally. These LOIs contemplate evaluation of multi-reactor installations. The LOIs generally describe preliminary concepts for site access, project development coordination, power delivery, and development sequencing. Collectively, as of the date of this prospectus, the discussions reflected in our non-binding LOIs relate to potential reactor deployments that could support up to 15 gigawatts of generation capacity if fully developed over time.

These LOIs are non-binding and do not contain commitments to purchase electricity, finance projects, construct facilities, grant exclusivity, or deploy a specified number of reactors. Either party may terminate these arrangements without penalty.

Commercial Deployment Strategy

Our initial commercial development plan contemplates a first commercial facility involving multiple Gravity Reactors deployed at a single site. This initial commercial deployment is intended to serve as a bridge between pilot-scale demonstration and subsequent scaled commercial deployments by supporting validation of construction methods, operational procedures, project development processes and commercial structures. While this initial facility is expected to generate power, it is not necessarily intended to reflect optimized economics, refueling strategies or generation capacity expected for future commercial deployments.

Subject to successful completion of pilot reactor activities, future regulatory approvals, site development progress, project financing, and customer arrangements, we may, following initial commercial deployment, pursue larger deployments at suitable locations where reliable baseload electricity is needed and where conditions support borehole construction and reactor emplacement. Our target for some of these later installations is to involve clusters of reactors capable of producing hundreds of MWe to more than one gigawatt of generation capacity at a single site that could support large-scale electricity generation installations capable of supplying power to data centers, utilities, industrial facilities, and other high-demand energy users. We are targeting as fast as six months for a single reactor construction period for later deployments.

We intend to pursue commercial deployments initially within the United States, with potential future opportunities in international markets.

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The timing, scale, and structure of commercial deployments remain subject to a number of factors, including engineering progress, regulatory approvals, export control requirements, applicable international nuclear cooperation agreements, successful completion of pilot reactor activities, financing availability, supply chain and fuel availability, interconnection and infrastructure considerations, site conditions, and customer demand.

Business Model and Revenue Streams

Our business model is designed to generate revenue from (i) project-level equity participation, including indirect participation in project-level cash flows from electricity sales, (ii) one-time upfront revenue, generally expected to be associated with Gravity Reactor deployment and related upfront project development services and (iii) recurring revenue, generally expected to be associated with technology licensing and operations and maintenance services of Gravity Reactor installations. We expect that the specific commercial structure of any project will vary, including based on customer requirements, site characteristics, local power delivery infrastructure, financing arrangements, regulatory requirements, and project counterparties.

Gravity Reactor installations are expected to be developed as long-lived energy infrastructure assets. We may participate in multiple stages of the project lifecycle, including project development, reactor deployment, commissioning, and ongoing operations and maintenance.

Project-Level Equity Participation; Electricity Sales

For certain projects, we intend to participate in the ownership, development, and operation of Gravity Reactor facilities. In these projects, electricity generated by the reactors may be sold to customers at the project-level under PPAs or similar offtake arrangements, and we may benefit from the cash flows of such sales, in many cases through our retained equity in the project.

These agreements may include fixed-price or market-linked electricity pricing structures and may be structured as direct power supply agreements at the project-level with end users or through arrangements involving local utilities or grid operators. Such agreements are commonly used in energy infrastructure projects to support long-term revenue stability and project financing.

Under this model, we intend to benefit from project-level cash flows associated with electricity generation and sale over the operating life of the facility, in many cases through our retained equity in the project. We expect that many such projects may be structured using project-level financing and infrastructure partnerships, which may allow individual reactor projects to be financed and operated through project-specific capital structures.

In many jurisdictions, the delivery of electricity generated by Gravity Reactor facilities will require coordination with local electric utilities, transmission operators, or regional grid operators. Depending on the location of a project and applicable market structures, electricity may be delivered directly to an end user through dedicated infrastructure, through utility-sleeved arrangements, or through interconnection to regional transmission systems. As a result, the development of reactor projects may involve engagement with utilities, transmission providers, and grid operators to obtain necessary interconnection approvals and coordinate power delivery arrangements. The structure of these arrangements may vary depending on local regulatory frameworks, transmission availability, and project-specific commercial agreements.

Upfront Revenue Streams

In connection with the deployment of Gravity Reactor facilities, we intend to generate revenue from activities associated with reactor delivery, integration, and project development.

Reactor Delivery and Integration

We intend to generate revenue through services including engineering support, reactor delivery, integration of reactor systems with subsurface and surface infrastructure, and related services necessary to support installation and commissioning of Gravity Reactor units.

Project Development and Engineering, Procurement and Construction (“EPC”) Support

We may also generate revenue from project development and EPC-related support activities, which may include engineering support, project planning, site evaluation, permitting coordination, borehole development planning, construction coordination, installation, commissioning support, and other services required to advance a reactor installation from development through construction.

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We may provide these services directly or in coordination with engineering, drilling, construction, and infrastructure partners involved in the development and installation of reactor facilities.

Recurring Revenue Streams

Technology Licensing

We intend to generate revenue from licensing our proprietary technology in connection with the development and operation of Gravity Reactor facilities. These revenues may include recurring intellectual property fees associated with the use of our reactor platform, subsurface deployment methods, and related systems and know-how.

Technology licensing arrangements may apply to projects developed by us (but owned in whole or in part by third parties) or to projects developed or owned by third parties utilizing our technology platform. Licensing structures may include recurring fees, milestone payments, and/or other arrangements depending on the structure of the underlying project.

Operations and Maintenance Services

We also intend to provide ongoing operational and technical support for deployed reactor facilities. These services may include reactor operations support, maintenance planning, monitoring, refueling coordination, regulatory support, and other services associated with the operation of Gravity Reactors over time.

These services may generate recurring revenue streams throughout the operating life of reactor installations and may be provided either directly by us or indirectly through arrangements we may establish with qualified nuclear operations partners.

Flexibility of Project and Commercial Structures

We expect that project structures and commercial arrangements may vary across projects. In some cases, we may participate directly in project ownership and project-level electricity sales. In some cases (which may include cases where we participate directly in project ownership), we may provide technology, development, deployment, licensing, or operational services in support of projects owned or financed by third parties.

As a result, the mix of revenue that may be derived directly or indirectly by us from electricity sales, project development activities, technology licensing, and operations support may differ depending on the structure of a particular project.

Target Markets

Our target markets consist of electricity customers and energy markets that require reliable, affordable baseload power and that may benefit from modular nuclear generation located near the point of demand. We believe that the Gravity Reactor may be well suited for applications where electricity demand is large, continuous, and difficult to satisfy using other generation sources alone.

While we have not yet deployed commercial reactors, we are evaluating potential opportunities across several end-use markets where long-term electricity demand growth and reliability requirements may support the deployment of Gravity Reactor facilities.

Data Centers and Digital Infrastructure

Our initial commercial focus is on hyperscale data centers and other digital infrastructure facilities that require large quantities of reliable electricity. Data centers supporting cloud computing, artificial intelligence workloads, and large-scale data processing often operate continuously and require stable baseload power supply.

Demand for electricity associated with digital infrastructure has increased significantly in recent years as the scale of computing infrastructure has expanded. Many data center operators seek long-term energy supply arrangements to support the continuous operation of these facilities, particularly in regions where grid capacity is constrained or where new generation resources are required to meet projected electricity demand.

We believe that modular nuclear generation may provide an attractive solution for data center operators seeking reliable, cost-efficient power over long time horizons, with the ability to scale capacity as demand increases.

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Industrial and Energy-Intensive Facilities

Industrial facilities represent another potential market for Gravity Reactor deployments. Certain industries—including advanced manufacturing, mining, chemical production, and large-scale processing facilities—require significant quantities of reliable electricity to support continuous operations.

These facilities may benefit from dependable baseload power generation capable of supporting uninterrupted operations and reducing reliance on weather-dependent energy sources. In some cases, industrial operators may also seek to reduce emissions associated with electricity consumption, which may increase demand for low-carbon power generation technologies.

Utilities and Grid-Scale Generation

Electric utilities and other power generation developers may represent another potential customer group for Gravity Reactor installations. Utilities are responsible for maintaining reliable electricity supply within their service territories and may seek additional sources of firm generation capacity to support growing electricity demand, replacement of retiring generation assets, or integration of intermittent renewable generation resources.

Modular nuclear generation may provide utilities with an additional option for reliable, affordable electricity generation that can operate continuously and provide stable grid support.

Government and Defense Installations

Government and defense facilities represent potential deployment opportunities for our Gravity Reactor technology. Certain installations require reliable electricity supply to support mission-critical operations and may seek energy solutions capable of operating independently of external grid disruptions.

In some cases, distributed nuclear generation may offer advantages for installations requiring high levels of energy security, resilience, and long-term operational reliability. Multiple boreholes allow for smaller, independently operable assets that can be reset quickly. Because the Gravity Reactor is not dependent on weather conditions or fuel logistics, and its refueling cycles are expected to be longer than traditional fueling cycles, it could deliver persistent power in remote or contested locations. A deep underground environment also has the potential to offer significant security benefits. Limited above-ground exposure could furnish inherent physical protection for critical systems, enhance their survivability and reduce the facility’s targeting profile. Additionally, deep underground placement could provide natural shielding against drones, missiles and surface-level sabotage.

Geographic Focus

Our initial market focus is within the United States, where electricity demand growth, expanding digital infrastructure, and evolving energy policy are creating increasing demand for reliable, affordable electricity generation.

We are evaluating international opportunities, particularly in jurisdictions that maintain civil nuclear cooperation agreements with the United States and that support the deployment of advanced nuclear technologies. Any international deployment would be subject to applicable export control regulations, international agreements, and local regulatory approvals.

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Implications of Being an Emerging Growth Company and a Smaller Reporting Company

As a company with less than $1.235 billion in revenue during our last fiscal year, we qualify as an “emerging growth company” as defined in the Jumpstart Our Business Startups Act of 2012 (“JOBS Act”). An emerging growth company may take advantage of reduced reporting requirements that are otherwise applicable to public companies. These provisions include, but are not limited to:

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We may use these provisions until the last day of our fiscal year in which the fifth anniversary of the first sale of our common stock pursuant to an effective registration statement occurs. However, if certain events occur prior to the end of such five-year period, including if we become a “large accelerated filer,” our annual gross revenues exceed $1.235 billion or we issue more than $1.00 billion of non-convertible debt in any three-year period, we will cease to be an emerging growth company prior to the end of such five-year period.

We have elected to take advantage of certain of the reduced disclosure obligations in this prospectus and may elect to take advantage of other reduced reporting requirements in future filings. As a result, the information that we provide to our stockholders may be different than other public reporting companies.

The JOBS Act provides that an emerging growth company can take advantage of an extended transition period for complying with new or revised accounting standards, until those standards apply to private companies. We have elected to take advantage of the benefits of this extended transition period and, therefore, we will not be subject to the same new or revised accounting standards as other public companies that are not emerging growth companies, until these standards apply to private companies. Our financial statements may therefore not be comparable to those of companies that comply with such new or revised accounting standards. Until the date that we are no longer an emerging growth company or affirmatively and irrevocably opt out of the exemption provided by Section 7(a)(2)(B) of the Securities Act upon issuance of a new or revised accounting standard that applies to our financial statements and that has a different effective date for public and private companies, we will disclose the date on which we will adopt the recently issued accounting standard. We are also a “smaller reporting company,” as defined in the Exchange Act, meaning that the market value of our stock held by non-affiliates was less than $700 million and our annual revenue was less than $100 million during the most recently completed fiscal year. We will continue to be a smaller reporting company until the last day of the fiscal year in which either (i) the market value of our stock held by non-affiliates is more than $250 million measured on the last business day of our second fiscal quarter or (ii) our annual revenue is more than $100 million during the most recently completed fiscal year and the market value of our stock held by non-affiliates is more than $700 million measured on the last business day of our second fiscal quarter. If we are a smaller reporting company at the time we cease to be an emerging growth company, we may continue to rely on exemptions from certain disclosure requirements that are available to smaller reporting companies. Specifically, as a smaller reporting company we have chosen, and may in the future choose, to present only the two most recent fiscal years of audited financial statements in this prospectus and our other filings from time to time and, similar to emerging growth companies, smaller reporting companies have reduced disclosure obligations regarding executive compensation. Likewise, if we are an emerging growth company at the time we cease to be a smaller reporting company, we may continue to rely on exemptions from certain disclosure requirements that are available to emerging growth companies.

Corporate Information

We were incorporated as Surfside Acquisition Inc. (“Surfside”) in the State of Delaware on December 10, 2021. Prior to the Merger (as defined below), we were a “shell company” (as defined in Rule 12b-2 under the Exchange Act). On September 5, 2025 (the “Merger Closing Date”), Surfside completed a merger (the “Merger”) with Deep Fission Nuclear, Inc. (formerly known as Deep Fission, Inc.), a private Delaware corporation (“Legacy Deep Fission”), pursuant to an Agreement and Plan of Merger and Reorganization (the “Merger Agreement”), under which a wholly owned subsidiary of Surfside merged with and into Legacy Deep Fission, with Legacy Deep Fission continuing as the surviving corporation and becoming a wholly owned subsidiary of Surfside. In connection with the transaction, Surfside changed its name to Deep Fission, Inc. For financial reporting purposes, the transaction was treated as a recapitalization and reverse acquisition, with Legacy Deep Fission considered the accounting acquirer.

Our principal executive offices are located at 2001 Addison St., Suite 300, Berkeley, California 94704. Our telephone number is (707) 400-0778. Our website address is www.deepfission.com. The information contained on, or accessible through, our website is not incorporated by reference into this prospectus, and the references to our website are intended to be inactive textual references only.

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Recent Developments

SAFE Notes Settlement

In May 2026, we issued 188,701 shares of our common stock (the “SAFE Notes Settlement”) to former holders of our previously issued SAFE Notes. The issuance related to our September 2025 financing activity and, in connection with this issuance, the investors executed settlement agreements releasing us from any potential future claims related to the SAFE Notes.

2026 Annual Meeting; Proposed Amendment to 2025 Equity Incentive Plan

Prior to the closing of this offering, we expect to file our definitive proxy statement related to our 2026 annual meeting of stockholders, which will be held in July via live webcast. Our board of directors expect to fix the record date for our 2026 annual meeting of stockholders to a date that is prior to the closing of this offering, meaning that shares of our common stock offered and sold in this offering will not entitle their holders to notice of or to vote at our 2026 annual meeting of stockholders. Among the proposals to be voted on at our 2026 annual meeting of stockholders is an amendment to our 2025 Equity Incentive Plan to increase the number of authorized shares of our common stock available for issuance thereunder by 5.0 million shares (the “2025 Plan Proposed Amendment”).

Summary of Risk Factors

Investing in our common stock involves a high degree of risk. You should carefully consider the risk factors discussed below and other risks, which are discussed in more detail in the section of this prospectus entitled “Risk Factors”, together with all of the other information contained in this prospectus and the Registration Statement of which this prospectus forms a part. The risk factors set forth below and in the section of this prospectus entitled “Risk Factors” are not the only risks we face; we may also face risk factors not presently known to us or that we currently believe to be immaterial. If any of the following risk factors, any risk factors described in the section of this prospectus entitled “Risk Factors” or any other risk factors actually occur, our business, prospects, results of operations, and financial condition could be materially adversely affected. In such event, the trading price of our common stock could decline, and you might lose all or part of your investment.

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THE OFFERING

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⁽¹⁾ Unless otherwise indicated, references in this prospectus to the number and percentage of shares of our common stock outstanding before, or to be outstanding upon completion of, this offering are based on 57,927,788 shares of our common stock outstanding as of May 14, 2026, which is comprised of 56,396,123 shares of our common stock actually outstanding as of May 14, 2026 and the issuance of an additional 1,531,655 shares of common stock after giving effect to the Expected RSU Settlement and the Expected Option and Warrant Exercise (each, as defined below). The amount of shares of our common stock actually outstanding as of May 14, 2026 and, unless otherwise indicated, other information presented in this prospectus, (i) includes 19,362,274 shares of our common stock that were issued as restricted stock awards, (ii) includes the shares of our common stock that were issued in the SAFE Notes Settlement, which closed prior to May 14, 2026 as described in “Prospectus Summary—Recent Developments—SAFE Notes Settlement,” and (iii) excludes:

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Unless otherwise indicated, references in this prospectus to the number and percentage of shares of our common stock outstanding before, or to be outstanding upon completion of, this offering gives effect to:

In addition, unless otherwise indicated, the information presented in this prospectus assumes (i) no exercise of the underwriters’ option to purchase additional shares of our common stock from us to cover over-allotments, (ii) except for the Expected RSU Settlement and the Expected Option and Warrant Exercise, no settlement of any RSUs and no exercise of outstanding warrants or options to purchase our common stock, in each case, subsequent to May 14, 2026 and (iii) does not reflect any purchase by our directors, officers or employees of any shares of our common stock in this offering pursuant to the directed share program.

The assumed 50.9% tax withholding rate used in this prospectus is an assumed blended withholding rate for the stock options that are subject to withholding in the Expected Option Exercise. The estimates in this prospectus relating to the RSU Settlement and the Expected Option Exercise and related share withholding may differ from actual amounts due to, among other things, the actual public offering price and other terms of this offering determined at pricing, forfeitures, and actual tax withholding rates.

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SUMMARY CONSOLIDATED HISTORICAL FINANCIAL DATA

The following summary consolidated financial data as of and for the years ended December 31, 2025 and 2024 are derived from audited consolidated financial statements and the accompanying notes (in the case of financial data as of and for the year ended December 31, 2024 as restated in the Restatement) that are included elsewhere in this prospectus. The following summary interim consolidated financial data as of March 31, 2026 and for each of the three months ended March 31, 2026 and March 31, 2025 are derived from unaudited consolidated financial statements and the accompanying notes that are included elsewhere in this prospectus.

The summary consolidated financial data below is only a summary and should be read together with the other information included in this prospectus, including “About this Prospectus,” “Prospectus Summary—Recent Developments,” “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and our consolidated financial statements and the accompanying notes. The summary financial information set forth below does not purport to indicate our financial condition or results of operations as of any future date or for any future period. Totals may be affected by rounding.

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Consolidated Balance Sheets

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Consolidated Statements of Operations

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Consolidated Statements of Stockholders’ Equity (Deficit)

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Consolidated Statements of Cash Flows

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