AAWSAP DIRD, Aneutronic Fusion Propulsion I, November 2010

This Defense Intelligence Reference Document, prepared in fiscal year 2010 by the Defense Intelligence Agency's Defense Warning Office under the Advanced Aerospace Weapon System Applications (AAWSA) Program, reviews aneutronic fusion as a way to propel spacecraft. It compares chemical, ion, fission, fusion and antimatter propulsion, and it also covers radiation shielding and relativistic rocket calculations. It looks at research needs over the next 30 years for missions from low Earth orbit to Mars, Jupiter and Alpha Centauri.

From the source:Release of 2026-09-18 Incident: 11/1/10, Las Vegas, Nevada. Released with redactions. 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 surveys aneutronic fusion as a possible advanced space-propulsion method, focusing on fusion reactions that release most of their energy in charged particles rather than neutrons and therefore offer potential advantages over more neutron-intensive fusion concepts, especially in radiation shielding, direct energy conversion, and thrust generation. The report reviews the underlying rocket physics, compares candidate fusion fuels and ignition conditions, and gives particular attention to proton-boron and related schemes, while also discussing Bussard’s concepts and other fusion projects as representative development paths. It also makes clear that the central obstacle remains ignition and sustained net-energy fusion under practical conditions, and it notes additional problems such as x-ray energy losses from the hot plasma, extreme temperature requirements, and the gap between theoretical specific impulse and what proposed systems had demonstrated experimentally. Overall, the document presents aneutronic fusion propulsion as an attractive long-range concept for deep-space travel, but one whose practical realization still depended on major unresolved advances in fusion engineering.

UNCLASSIFIED//POlt Offl@IAL WS& &NkY
Appendix A: Relativistic Rockets
Since the application of a constant acceleration for a long period of time can lead to
very high velocities, these spacecraft may reach relativistic ve locities where V > 0.5 c
(speed of light). At these velocities, time dilation and Lorentz contraction can be
significant. 22 Special Relativity ca n be used to compute these effects based on the
Lore ntz factor, y, as shown below:
(A.2)
Specific impulse for relativistic rockets is usually expressed in dimensionless form:
I;, = y ( v,x; rns,) (A.3)
Treating Earth as a nonaccelera t ing reference frame, time intervals measured on a
rocket traveling at a velocity with respect to Earth will be "dilated" according to the
following equation:
!!i_tearth = y !!i_trocket (A.4)
Time intervals measured by the crew on the rocket will be longer than the interval
measured on Earth. The ratio of time measured on the rocket to t ime measured on
earth follows the graph in Figure 12. When a spacecraft reaches 86% of the speed of
light, t heir "clock" will run at half the speed of a clock located on earth.
For a constant acceleration, equations for rocket performance can be written in terms of
the following variables:
t = time measured on the rocket
t' = time measured in the rest mass frame (Earth)
D = distance traveled
a = acceleration
C = speed of light
V final = final rocket velocity at rocket time t'
(A.5)t' =~ smh (a/)= (~r+ ~
(A.6)
D< [cost') -,]< [ 1+(":J - 1]
(A.7)
UNCLASSIFIED/fF&A &FFI&I:.l.k W&li &NkY
30