Antares builds compact nuclear fission microreactors for U.S. defense and space applications, engineered to run autonomously for six or more years on a single fuel load. The launch marks the company's Series C, which arrived weeks after its Mark-0 reactor achieved criticality at Idaho National Laboratory, the first privately developed non-light-water reactor to go critical in the United States in more than four decades. The round comes at a moment when U.S. military installations are increasingly exposed to a commercial grid under strain, and when Executive Order 14299 directs the Department of War to have a reactor operating at a domestic base by September 30, 2028.
The company was founded in 2023 by Jordan Bramble, previously at the White House, and Julia DeWahl, formerly on the Starlink team at SpaceX. Antares operates out of Torrance, California, with additional facilities in Idaho Falls and Aiken, South Carolina, and its first customer relationships include the U.S. Air Force under the Advanced Nuclear Power for Installations initiative, with Joint Base San Antonio positioned as an early host site. The Mark-0 milestone validated reactor physics and controls in a full-scale core using TRISO fuel, moving the design toward Mark-1, an electricity-producing reactor slated for 2027.
The $470 million Series C consists of $370 million in equity and $100 million in debt, co-led by Paradigm and Caffeinated Capital, with participation from Point72 Ventures, Shine Capital, and Industrious Ventures. The capital is earmarked for the transition from a demonstrated core to fielded power systems, with initial deployments to defense customers beginning in 2028. For operators and investors tracking advanced nuclear, this launch is a signal that the sector is moving from paper designs and demo hardware to firm military contracts and a delivery timeline measured in single-digit years.
Comments (12)
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N
Nkechi OkaforJul 27, 2026
Asteroid belt is doing a lot of heavy lifting in that tagline when your first customer is probably a Virginia data center.
T
Tomek WróblewskiJul 27, 2026
The tweet cuts off mid sentence and somehow that's the most confident thing about the whole thread. Committing to the bit.
R
Ravi PrakashJul 27, 2026
Race to criticality is a wild sentence to open a launch post with. My compliance team just fainted.
M
Maeve KilbrideJul 27, 2026
Video pacing was tight until the reactor b-roll. Held that shot about four seconds too long, my dopamine dipped.
B
Benji K.Jul 27, 2026
Thumbnail is a glowing blue thing and the word ANTARES in a serif. You could have sold me a cologne with that exact frame.
J
Jun-ho BaeJul 27, 2026
Every fission startup pitches me as the next Anduril of energy. At least this one has a reactor to point at.
G
Grigor PetrosyanJul 27, 2026
Nuclear is having its moment which means we are exactly 18 months from everyone deciding nuclear is over again.
L
lilaJul 27, 2026
Genuine question from someone who just started in energy policy: how do you actually get a customer before the NRC signs off? Is that a handshake thing?
S
Søren LindqvistJul 27, 2026
Ops question nobody asks: how do you ship a reactor. Like literally, what truck.
M
Mina El TayebJul 27, 2026
Ex White House founder raising a big Series C for reactors feels less like a startup and more like a foreign policy instrument with a cap table.
P
Prachi DevarakondaJul 27, 2026
Are you hiring reactor engineers with security clearance? I know someone leaving a national lab who keeps asking me about you.
V
vukJul 27, 2026
Every energy launch this quarter has been more cinematic than the last. At some point one of you is going to release a feature film instead of a product.
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Antares builds compact nuclear fission microreactors for U.S. defense and space applications, engineered to run autonomously for six or more years on a single fuel load. The launch marks the company's Series C, which arrived weeks after its Mark-0 reactor achieved criticality at Idaho National Laboratory, the first privately developed non-light-water reactor to go critical in the United States in more than four decades. The round comes at a moment when U.S. military installations are increasingly exposed to a commercial grid under strain, and when Executive Order 14299 directs the Department of War to have a reactor operating at a domestic base by September 30, 2028. The company was founded in 2023 by Jordan Bramble, previously at the White House, and Julia DeWahl, formerly on the Starlink team at SpaceX. Antares operates out of Torrance, California, with additional facilities in Idaho Falls and Aiken, South Carolina, and its first customer relationships include the U.S. Air Force under the Advanced Nuclear Power for Installations initiative, with Joint Base San Antonio positioned as an early host site. The Mark-0 milestone validated reactor physics and controls in a full-scale core using TRISO fuel, moving the design toward Mark-1, an electricity-producing reactor slated for 2027. The $470 million Series C consists of $370 million in equity and $100 million in debt, co-led by Paradigm and Caffeinated Capital, with participation from Point72 Ventures, Shine Capital, and Industrious Ventures. The capital is earmarked for the transition from a demonstrated core to fielded power systems, with initial deployments to defense customers beginning in 2028. For operators and investors tracking advanced nuclear, this launch is a signal that the sector is moving from paper designs and demo hardware to firm military contracts and a delivery timeline measured in single-digit years.
Comments (12)
Asteroid belt is doing a lot of heavy lifting in that tagline when your first customer is probably a Virginia data center.
The tweet cuts off mid sentence and somehow that's the most confident thing about the whole thread. Committing to the bit.
Race to criticality is a wild sentence to open a launch post with. My compliance team just fainted.
Video pacing was tight until the reactor b-roll. Held that shot about four seconds too long, my dopamine dipped.
Thumbnail is a glowing blue thing and the word ANTARES in a serif. You could have sold me a cologne with that exact frame.
Every fission startup pitches me as the next Anduril of energy. At least this one has a reactor to point at.
Nuclear is having its moment which means we are exactly 18 months from everyone deciding nuclear is over again.
Genuine question from someone who just started in energy policy: how do you actually get a customer before the NRC signs off? Is that a handshake thing?
Ops question nobody asks: how do you ship a reactor. Like literally, what truck.
Ex White House founder raising a big Series C for reactors feels less like a startup and more like a foreign policy instrument with a cap table.
Are you hiring reactor engineers with security clearance? I know someone leaving a national lab who keeps asking me about you.
Every energy launch this quarter has been more cinematic than the last. At some point one of you is going to release a feature film instead of a product.