AAWSAP DIRD: An Introduction to the Statistical Drake Equation, March 11, 2010 — Department of War Research Paper
This DIRD introduces the Drake Equation, a well-known thought framework for estimating how many communicative extraterrestrial civilizations might exist in the galaxy. It reformulates the equation in statistical terms, arguing that the usual approach of assigning fixed values to its variables is…
Incident Overview
This Defense Intelligence Reference Document was written under the Advanced Aerospace Weapon System Applications Program (AAWSAP), the Defense Intelligence Agency contract run by Bigelow Aerospace Advanced Space Studies, and is dated March 11, 2010. It was declassified and published on September 18, 2026 as part of the sixth tranche of the Department of War’s Presidential Unsealing and Reporting System for UAP Encounters (PURSUE). The released copy carries redactions.
What the government released
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 introduces the Drake Equation, a well-known thought framework for estimating how many communicative extraterrestrial civilizations might exist in the galaxy. It reformulates the equation in statistical terms, arguing that the usual approach of assigning fixed values to its variables is too simplistic because major inputs are uncertain and are better modeled as probability distributions. Using that approach, it concludes that, if one accepts the underlying logic of the Drake Equation, the estimated number of communicating civilizations should be treated as a range of possible values, and that the likely distance between neighboring civilizations can likewise be expressed statistically rather than as a single figure. The document is primarily a mathematical and methodological exercise, and its worked examples rely on assumed values to illustrate the framework rather than to establish a firm astrophysical estimate. Overall, it is an attempt to formalize uncertainty within the Drake framework rather than an attempt to bound the actual likelihood, prevalence, or proximity of extraterrestrial civilizations.
Primary-source excerpt
Drawn directly from the released document: “Yet, even by using the largest radiotelescopes on Earth (the 310-meter dish at Arecibo, for instance), we cannot search for aliens beyond, say, a few hundred light years away. This is a very, very small amount of space around us within our galaxy, the Milky Way, that is about 100,000 light years in diameter. Thus, current SETI can cover only a very tiny fraction of the galaxy, and it is not surprising that in the past 50 years of SETI searches, NO extraterrestrial civilization was discovered.”
Related records
This paper was written under the contract set out in AAWSAP Statement of Objectives and AAWSAP Solicitation and Original Order, which defined what AAWSAP was asked to study. Read those first: they explain why a program framed around foreign aerospace threats commissioned papers on subjects this far from any known aircraft.
The case in this archive
This record is a primary source for the Advanced Aerospace Weapon System Applications Program, written up here at length from the contemporary record. The file and the case history are worth reading against each other: the document is narrower and more cautious than the account that grew up around it, which is usually the point.
Status of the case
A Defense Intelligence Reference Document is a literature review, and the government’s own summary asks that it be read as one: a reference and synthesis product rather than original research, released without any implication that the concepts it discusses have been validated. The paper collects and summarises published work. It does not report an observation, test a device, or offer evidence that anything it describes has been built, by the United States or anyone else. That caveat matters most for the papers on warp drives, wormholes, antigravity and negative energy, which survey theoretical proposals that remain speculative and in several cases depend on physics no experiment has shown to exist. AAWSAP was a Defense Intelligence Agency contract, awarded in 2008 to Bigelow Aerospace Advanced Space Studies in Las Vegas, to anticipate foreign aerospace threats decades ahead, and its 38 reference papers show what the program chose to spend its time on. The All-domain Anomaly Resolution Office has made no finding about this document, and none is implied by its release.