UNCLASSIFIED // PUBLIC RELEASERELEASE 06 · SEPTEMBER 18, 2026
PENTAGON UFO FILE · DOCUMENT · DOW-UAP-D152AAWSAP DIRD, Negative Mass Propulsion, January 2011
This DIRD, dated January 2011 and written for the AAWSAP program, takes up one of physics’ strangest hypotheticals: matter with negative mass. It asks whether such matter could exist in any meaningful sense and whether it could make spaceflight cheaper. The release describes a theoretical exploration.
Odd behavior on paper
Negative mass would behave counterintuitively. Pair a positive and a negative mass and, in some theories, the two chase each other, accelerating indefinitely without any fuel. Combine them in the right proportions and the result could have very little inertia. The paper reviews these effects and treats them as at least formally allowed by certain extended theories of gravity.
It then considers two ways to get hold of negative mass: making or separating it using extreme fields or particle energies, or finding it already separated deep in strong gravitational wells, such as the centers of galaxies or possibly the Moon. The author regards the first as effectively out of reach and the second as highly uncertain.
How speculative this is
No negative mass has ever been observed, and the paper’s second route relies on a long chain of untested assumptions about its existence, separability and large-scale behavior. The release calls it a far-reaching exploration resting on premises outside consensus physics. Compare Antigravity for Aerospace Applications and Traversable Wormholes, Stargates, and Negative Energy.
The official description
From war.gov/UFO, released September 18, 2026, quoted in full
This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed.
This DIRD examines whether negative mass could exist in a physically meaningful way and whether it could someday reduce the energy cost of spaceflight. The report reviews the unusual dynamics that would follow if positive and negative mass could interact, including self-accelerating mass pairs and matter with very low or nearly zero effective inertia, and treats such ideas as at least formally compatible with certain extensions of gravitational theory. It then considers two broad paths toward practical use: creating or separating negative mass through extreme fields or particle energies, and locating naturally separated negative matter in deep gravitational wells such as galactic centers or possibly the Moon. However, the document also concludes that the first path is effectively beyond technical reach and treats the second as highly uncertain, resting on a long chain of unverified assumptions about the existence, separability, and macroscopic behavior of negative mass. Overall, this DIRD is a far-reaching theoretical exploration of an exotic propulsion concept whose practical application depends on premises that remain unestablished in consensus physics.