DOW-UAP-D123: Positron Aerospace Propulsion - From a Round-the-World Drone to a Crewed Mars Ship

Source file: DOW-UAP-D123_AAWSAP-DIRD-Positron-Aerospace-Propulsion-March-2-2010.pdf Originating agency: Defense Intelligence Agency (DIA), Defense Warning Office, under the AAWSAP program Document type: Defense Intelligence Reference Document (DIRD), "Acquisition Threat Support" series; control number DIA-08-1003-002 Date: 2 March 2010 (information cutoff date, ICOD: 1 December 2009) Classification: UNCLASSIFIED//FOR OFFICIAL USE ONLY (the FOUO marking is struck through on every page; released to the public in 2026) Page count: 35 VIRIN: 260918-D-D0360-1112 PURSUE Release: 6

Summary

This is one of the DIRDs produced under AAWSAP (some of the program's documents call it the "AAWSA Program"), and its subject is antimatter, or more precisely positrons: the antimatter counterparts of electrons. The paper runs to 30 numbered pages plus front matter, with 22 figures and 6 tables. It was prepared by the Acquisition Support Division (DWO-3) of the Defense Warning Office, in DIA's Directorate for Analysis, and the author's name is redacted as AAP Person 69.

The introduction describes the paper in an unusual way: the studies it draws on were sponsored by the Air Force Research Laboratory (AFRL) at Eglin Air Force Base and by the NASA Institute for Advanced Concepts (NIAC), and the paper is "an anthology of that work and not a general review of antimatter propulsion." Nearly every figure is credited to one private company, Positronics Research LLC, and the author reports "our measurements" and "proprietary experiments" at that company. In other words, this is a synthesis of a single line of research by someone involved in it, not an independent assessment.

The paper moves from the physics of antimatter, through air-breathing engines, rockets and power sources, to a crewed Mars mission, and closes with the three decisive problems: production, cost and storage. It does not mention UFOs, unidentified aerial phenomena or foreign technology, and it makes no reference to any specific intelligence threat.

Research Article

The document and its place in the program

The cover carries the heading "Defense Intelligence Reference Document" and the subheading "Acquisition Threat Support," the date 2 March 2010, the information cutoff date of 1 December 2009 and the control number DIA-08-1003-002 (page 1). Page 2 carries an administrative note: the paper is "one in a series of advanced technology reports produced in FY 2009" under the Defense Warning Office's AAWSA Program, and questions are to be addressed to AAP Person 1, AAWSA Program Manager, at DIA's Washington address. The same page carries a copyright warning about the photographs.

Of the 12 technical areas defined in the program's Statement of Objectives (DOW-UAP-D110), the paper mainly serves propulsion and power generation, since it devotes a section to onboard electrical power. One paragraph also touches armament: a proposal to use micrograms of positrons as electromagnetic pulse (EMP) ordnance to disable the electronics of missiles or aircraft from up to hundreds of meters away (page 13).

The physics case: 180 megajoules per microgram

The paper's foundation is well-established physics. The positron was predicted by Dirac in 1929 and discovered by Anderson in 1932; when it meets an electron the two annihilate and their entire mass becomes radiation, according to E = mc². The specific energy, the paper says, is 180 MJ per microgram, "10 orders of magnitude" larger than chemical energy (Figure 1, page 6). In the presence of matter, a positron binds with an electron to form a short-lived atom called positronium (Ps), whose mean lifetime in a vacuum is 125 picoseconds or 142 nanoseconds depending on spin orientation, and which decays into 511 keV gamma rays.

From this the author derives three advantages over fission and over antiprotons: the reaction is fast and can be throttled, the low-energy gamma rays do not create residual radioactivity in surrounding materials, and they are easy to convert into heat. The two obstacles are stated as early as page 7: it has not been possible to produce positrons in the numbers required, and current storage methods "do not hold enough positrons long enough." A precision is in order here: the claim of "no radiation" problems refers to the absence of induced radioactivity, not to the absence of radiation. The paper itself calculates that a 13-cm lead shield, which cuts the gamma flux by a factor of 8.3x10^-11, is needed so that a person 10 meters from a 100-milligram source would receive 2 rem, within the annual limit for U.S. radiation workers (page 16).

Air-breathing engines: a drone, a missile and an SSRV

The paper first sets out the historical background: the Air Force's Nuclear Energy for Propulsion of Aircraft program (1946 to 1951), the joint Aircraft Nuclear Propulsion program, canceled in 1961 without a prototype, and the SLAM nuclear ramjet missile of Project Pluto, whose Tory-IIA and Tory-IIC engines were tested at the Nevada Test Site before cancellation in 1964 (pages 7 to 8). The proposed substitute is the positron turbojet/ramjet engine (PTRE), in which gamma rays heat tungsten shells that pass the heat to air by convection.

Three applications are examined. The first is a 60-kg drone with a lift-to-drag ratio of four that could circumnavigate the Earth on 150 micrograms of positrons, modeled on the LOCAAS turbojet at AFRL (Figure 6, page 10). A long list of "dual-use" applications follows, from intelligence, surveillance and reconnaissance and coastal patrol to iceberg tracking in shipping lanes, livestock monitoring and nonstop global passenger flights (pages 11 to 12). The second is a ramjet-assisted missile: the 440-km range of BOMARC could grow to 2,000 km with one milligram of positrons (page 13).

The third is a single-stage reusable vehicle (SSRV). Tables 1 and 2 compare two vehicles with an identical dry mass of 60,500 kg and a payload of 11,340 kg: the chemical vehicle needs 368,300 kg of propellant for a gross liftoff weight (GLOW) of 451,540 kg, while the positron vehicle needs only 176,000 kg for a GLOW of 259,240 kg, 43 percent less (page 14). The flight profile (Figure 9): horizontal takeoff from Edwards Air Force Base, acceleration to Mach 1.8 as a turbojet, transition to ramjet mode, and rocket ignition at Mach 8 for the climb to low Earth orbit (LEO). Table 3 gives the budget: 2.5 mg for launch, 76.5 mg for the ramjet phase and 7.9 mg of margin, 86.9 milligrams in all (page 15).

Three rockets and an onboard power source

The paper examines three rocket designs (pages 16 to 22). In the solid-core rocket, similar to the NERVA nuclear-thermal rocket, positronium is injected into a tungsten matrix that heats hydrogen. A thermal analysis predicts a specific impulse (Isp) of 920 seconds at a chamber temperature of 3,000 Kelvin; burn times for a Mars trip are about 30 minutes, and a spacecraft with three 72-kilonewton engines would use 6 to 9 milligrams per mission. Table 4 is candid: the fission system was "demonstrated" in NERVA/Rover, while the positron system is "conceptual" and "must demonstrate positron storage and controlled injection."

In the gas-core rocket, gamma rays heat the fluid directly. Computational fluid dynamics showed that above 300 megawatts the dense regions of the fluid move away from the gamma source and the vortex configuration breaks down, but two configurations remained promising. The prediction: 130 kilonewtons of thrust at 85 percent efficiency, 25 milligrams for a 50,000-kg burnout mass, and an Isp ceiling of about 2,500 seconds, at the ionization threshold of hydrogen.

The third design is a modified version of the "photon rocket" proposed by the German engineer Eugen Sanger in 1953. The paper concedes that "there are no materials that reflect gamma rays at large angles," so the mirror is replaced by a pressure plate coated with silicon carbide ablation material, and a lead shell shifts the gamma wavelength from 511 keV down to 1 to 10 keV at 85 percent efficiency. The result: an Isp of 1,200 to 3,000 seconds, 40 to 145 kilonewtons of thrust, and 15 to 40 milligrams for a one-way trip to Mars. Table 5 summarizes the three designs for a velocity change (delta-V) of 3.7 km per second. Alongside them the paper describes a 100-kilowatt Brayton-cycle power system at 25 to 30 percent efficiency consuming 7 micrograms per hour, and a 110-watt Stirling generator based on the NASA Glenn Research Center's radioisotope generator (page 23).

A crewed mission to Mars

The Mars section (pages 24 to 27) draws on the 1997-98 reference mission of NASA's Mars Exploration Study Team and adopts its main planning principles: several payloads instead of a single vehicle, unmanned cargo on a slow transfer, and a fast crewed transit of under 180 days, which the paper says would not require artificial gravity. Launch windows come every 778 days. Figure 16 shows a cargo flight in 2029, a crewed lander in 2031, a return in 2033 and a second lander in 2035 if necessary. Each window sees two 45,000-kg payloads launched on a Saturn V-class rocket and assembled in low orbit.

In the most ambitious version, a crew of five or six astronauts flies to Mars in the positron SSRV itself. The conclusions claim such a vehicle could take off horizontally, reach Mars for a year of research and land horizontally back on Earth "without refueling," although the architecture described on page 26 includes refueling at the Earth space station. There is also a small inconsistency in the schedule: the text says the crew arrives at Mars in late 2033, while the caption of Figure 16 assigns 2033 to the return to Earth.

Production, cost and storage: the bottleneck

Here the paper confronts the decisive question. Radioactive positron sources are limited to about 10^6 slow positrons per second, electron accelerators reach 10^10 and reactors about 10^11. Proposals for the future include a Naval Research Laboratory betatron accelerator (10^16 per second, proposed in 1996), femtosecond-laser sources, and an undulator-based source for the International Linear Collider (10^14 to 10^16 per second). Assuming 10^16 per second is achieved within ten years, 150 micrograms could be produced in six months (pages 27 to 28).

According to Table 6, positrons are cheaper than antiprotons per joule by a factor of 1,000 to 100,000, and the projected price is $720,000 per microgram: one gram would cost $0.72 trillion, "5 percent of the 2008 U.S. gross domestic product." For comparison, a 2000 NASA study put antiprotons at $64 trillion per gram. The cost of the round-the-world flight is internally inconsistent: the cost section prices it at $96 million (page 29), the conclusions at $69 million (page 32); the text also refers to "Table 5" when the cost data are in Table 6.

Storage is the hardest problem, and the paper presents it honestly. A Penning trap has held 10^9 positrons for one hour; under the Brillouin limit, a 1-Tesla field allows at most 4x10^16 positrons in a 10-cm-radius sphere, about 40 picograms. The conclusion is that the storage limit is "tens of picograms," 7 to 8 orders of magnitude short of 100 micrograms, the threshold at which practical uses begin (pages 29 to 30). The proposed alternative is to store neutral positronium atoms in a porous material such as silica aerogel, in crossed electric and magnetic fields that pull the electron and positron apart. By Equation 2, voids of 20 nanometers should give a lifetime of 82.5 nanoseconds, or 1.2 microseconds if self-annihilation is suppressed; proprietary experiments measured up to 10 microseconds, and voids of 1,000 nanometers are predicted to give 61 milliseconds. Propulsion, in the paper's words, needs "months and years"; between 10 microseconds and a single month lies a gap of more than ten orders of magnitude.

Significance

The paper illustrates one end of the spectrum of the AAWSAP DIRD library: a concept resting on entirely proven physics, matter-antimatter annihilation, yet facing engineering gaps of many orders of magnitude. When the paper itself shows that the best traps hold tens of picograms, while the most modest drone needs 150 micrograms and the Mars mission up to 100 milligrams, it is clear why the official summary calls positron propulsion "highly speculative."

The paper's tone is also worth noting. It reads as the work of an enthusiastic advocate: the author hopes the paper "will help spread that good news" about the falling cost of antimatter, and closes by declaring that long lifetimes are "but a matter of engineering." It predicts a first round-the-world flight within ten years, "approximately 90 years after" Lindbergh's 1927 Spirit of St. Louis flight; by the time the document was released in 2026, no such flight had been publicly demonstrated.

Finally, as to unidentified phenomena: there is nothing. The paper does not deal with UFOs, analyzes no sightings and attributes no capabilities to any foreign actor. Its value to the archive lies in showing what baseline knowledge the program sought on future propulsion technologies, and how close some of its sources were to the advocates of the ideas themselves.

Key People

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Key Concepts

Notable Quotes

"Antimatter is considered an extremely attractive fuel for aerospace propulsion because of its enormous advantage in energy density over all other known sources of energy. However, because antimatter does not occur naturally and is unstable in the presence of matter, no vehicles have ever flown using it." -- page 5

"This paper is an anthology of that work and not a general review of antimatter propulsion." -- page 5

"In addition, positrons could act as ordnance to destroy electronics on missiles or aircraft by electromagnetic pulse (EMP) by detonation of micrograms of positrons up to hundreds of meters from the target." -- page 13

"The GLOW of the positron SSRV is 43 percent less than that of the chemical SSRV owing to reduced propellant mass." -- page 14

"Hence, the cost of 1 gram is $0.72T, or 5 percent of the 2008 U.S. gross domestic product (GDP)." -- page 28

"Therefore, by either space charge or magnetic energy considerations, the storage limit is tens of picograms, 7-8 orders of magnitude short of 100 micrograms, where practical uses of positrons begin to emerge, as illustrated earlier." -- pages 29-30

"With the issue of stabilization in crossed fields now settled, very long lifetimes are but a matter of engineering!" -- page 33