Defense Intelligence Reference Document Positron Aerospace Propulsion

UNCLASSIFIED//509 QFFIQl.l1ls WlilE 8HL\i
Assuming that 10 16 positrons/sec can be realized in the next 10 years, then 150
micrograms could be produced in 6 months to enable a globe-encircling flight of a small
air-breathing turbojet UAV as discussed earlier.
Positron Costs
An independent study has been done to determine future costs of positrons and, for
comparison, antiprotons as well. The results, shown in Table 6, are based on data for
existing sources and proposals for future sources. 60, 61 , 62
Table 6. Positron and Antiproton Expected Costs in the Next 10 Years
Source Trap Injection Filling Rate When $/JOULE
Enerav (MeV) (sec1) (annihilation)
CERN AD (pbart· 0.01 -0.1 4 X 10° Now ?
Fermilab lnbar)"" <0.002 2.8 X 10' Now 333•
e+/14 MeV e- linac"'/ILC~· 0.1 5 x10··/10" 2011/19 04/0.004 ..
* $100 million/year (est. op. cost).
** $5 million/year (est op. cost, adJusted for inflation)/$100 million/year (est. op. cost).
Two clear results of the study should be noted.
First, measured on a scale of dollars per joule of annihilation energy, positrons cost less
than antiprotons by a factor of 1,000-100,000. Because each antiproton produces 1,836
times more energy per annihilation than a positron, this result appears to defy logic.
However, the laboratory energy threshold for producing antiprotons is 6,000 times
greater than for positrons, requiring a relatively complex proton synchrotron that is
costly to construct and run. In addition, antiprotons are made at much higher
laboratory energy than positrons and require costly apparatuses to decelerate them to
trapping energies.
On the other hand, because electrons and positrons are relativistic at very low energy,
their electron production and secondary systems are comparatively simple and less
costly to operate and maintain than proton systems. These factors, combined with the
absence of radioactive residue associated with positron annihilation, make positrons the
obvious choice over antiprotons.
Second, the cost of positrons is projected to be $0.004/l x 180 Ml/μg = $720K/μg.
Hence, the cost of 1 gram is $0.72T, or 5 percent of the 2008 U.S. gross domestic
product (GDP). A 2000 NASA study 63 on which this author collaborated placed the cost
of antiprotons at $64T/g, consistent with the $333/J figure in the second line of Table
5, and roughly six times the 2000 GDP. Unfortunately, this is still being quoted in U.S.
scientific and government communities. The dramatic reduction in the unit cost of
antimatter since 2000 is due to a new emphasis on positrons by the physics
community, and hopefully this paper will help spread that good news.
Earlier, a nonstop flight around the globe by a small positron UAV was described as
equivalent to the 1927 Spirit of St. Louis transatlantic flight of Charles Lindbergh. From
23
UNCLASSIFIED/ 1«F81it 8FFI@Itllt ~:!II!! 8HLV