1) The document proposes an antimatter driven sail concept for deep space exploration, using antiprotons to induce fission in uranium and propel the sail. 2) Key challenges include the need for further testing to determine the number of atoms ejected per fission ("Nat"), as a high Nat value is required to achieve sufficient thrust. 3) An antimatter fission power system is also proposed to provide onboard power, with further work needed to optimize the scintillator and photovoltaic cell coupling. 4) Initial missions to the Kuiper Belt within 10 years may be possible with mg quantities of antihydrogen, helping demonstrate the concept, while interstellar missions could potentially launch within the next

1. Antimatter Driven Sail for Deep Space ExplorationDeep ExplorationDr. Steven D. HoweDr. HoweDr. Gerald P. JacksonDr. JacksonHbar Technologies, LLCHbar LLC

2. ““Any technology being presented to
you at this workshop will need at
least one miracle in development in
order to enable an interstellar
mission” -
Dr. Steven D. Howe
Interstellar Robotics Missions for the 21 21st st Century
Workshop, JPL/Cal Tech, 1998

6. Velocities Required for Deep
Space Missions
4.5e14
30,000
A Centauri ––
270,000 au –– 40 yrs
7.2e11
1200
Oort Cloud Cloud-
10,000 au au- 40 yrs
6.8e09
117
Kuiper Belt Belt-
250 au - 10 yrs
Energy Density
(j/kg)
Velocity
(km/s)
MISSION

7. Energy Densities
of Known Sources
90000e06
Antimatter
750e06
Fusion (100%)
71E06
Fission (100%)
15
Chemical
Specific Energy (MJ/kg)
Reaction

11. Antimatter Sail Concept
zz Any conversion cycle to produce thrust that
uses Local Thermodynamic Equilibrium
(LET) will be heavy
zz Antiprotons will induce fission in uranium
with 100% efficiency
zz Antiproton fission produces two products,
(roughly Pd Pd-111) each with near 1 MeV/amu
zz A particle with 1MeV/amu has a velocity of
around 1.38X10 1.38X107 m/s
zz Thus, an Isp of over 1 million seconds is
possible

12. Specific Impulse
zz For a given mission and ΔΔV, an optimum
V, specific impulse exists for minimum
energy consumption
zz Vex ex= 0.6 = ΔΔVmission mission
zz Mass Massfinal final/Mass /Massinitial initial = .2
zz For ΔΔV of 117 km/s, V V Vex ex=67 km/s
=(Isp Isp=6800s)
=

14. Variable Isp
zz Sail concept may have the ability to adjust
the Vex by varying the incident pbar energy
or sail material
zz Depositing the antiproton deep into the
uranium may lead to multiple atom ejection
resulting in increased thrust and reduced Isp
zz Momentum is transferred by ingoing particle
zz What is momentum from multi multi-atom burst?
zz Mechanism causing burst is not known

15. Potential Advantages
zz Extremely lightweight
zz Does not require ultra thin sail material
zz Ability to tack –– course correct
zz Ability to stop
zz Variable acceleration
zz Variable Isp

16. Phase I

17. Missions
zz An interstellar mission is the eventual goal but is
very tough
zz Kuiper Belt in 10 years demonstrates the
architecture
zz Did not consider periapsis pumping, gravity
boosts or more complex transfers transfers- believe these
are a 10 10-20% effect, i.e. 10km/s out of 100 km/s
zz Assumed departure from 1AU orbit but beyond
Earth orbit

19. Micro Payload
zz Assume a total instrument payload of 10
kg including communications
zz JPL report report- Deutsch, Salvo, & Woerner ––
10 10-50 kg by 2003
zz JPL report –– Hemmati & Lesh –– ACLAIM:
laser communications
zz Interstellar Robotics Missions for the 21 21st st
Century Workshop, 1998 1998- 10 kg

20. Sail Subsystem
zz Uranium coated carbon
zz Carbon is thick enough to stop FF
zz Examined the use of carbon only only- Isp
higher but not variable
zz Key parameter is Nat Nat- #atoms/fission
zz Diameter dictated by pellet expansion
zz Temperature dictates max pbar rate
zz Acceleration dictated by solar gravity

21. Sail Issues
zz Ejection and expansion of antihydrogen
pellet
zz Uniformity of deposition is not critical due
to carbon recoil contribution
zz Single most critical factor is Nat –– if Nat is
low then Isp is too high and mass goes up
and thrust is insufficient.

22. Antimatter Storage

23. Antimatter Storage

26. Antimatter Storage
zz Solid antihydrogen has energy density
zz Pbar + positron ÆÆ Hbar (Athena Athena-2002)
zz Hbar + Hbar ÆÆ H2bar bar
zz H2bar bar ÆÆ condensation ÆÆ solid pellet
zz Pellet + electrons ÆÆ pellet pelletn-
zz 10 1014 14 H2bar bar has diameter of 160 μμ
zz Pellets Pelletsn- are held in an electrostatic trap
array

29. Storage issues
zz Creation of solid H H2 pellet
zz Confinement of pellet in macro macro-scale
electrostatic trap
zz Containment of H H2bar in trap?
bar zz Condensation rate and confinement
zz Formation and control of pellet
zz Evaporation of pellet

30. Power
zz RTGs have 88 kg/kW
zz Voyager has 400 W and 35 kg
zz This would require 238 GJ of energy (13
mg pbars pbars) )
zz Had to develop new power source
zz Have on on-board the highest energy source
known
zz Antimatter Fission Conversion (AFC)

31. AFC
zz Utilize antiprotons extracted from storage
just as in the propulsion system
zz Impact conical receptor consisting of
uranium coated scintillator
zz Scintillator tailored to emit photons
“matched” to photo photo-voltaic (PV) cell

32. AFC
zz Wavelength of scintillator determines
conversion efficiency –– 25 eV per photon
required
zz Must operate at high temperatures
zz PV cell efficiencies and spectral response
zz Conclude CdWO4 –– high light output at
450 nm
zz Total efficiency = .044
zz Specific mass = 6.6 kg/ kw

34. Power Issues
zz AFC needs Proof Proof-of of-Concept (POC)
zz Temperature dependence is crucial
zz Coupling to radiator in pulsed mode
zz Z2 dependence could strongly impact
design
zz N2 emits at 350 nm (5 ev ev): can we find a
): PV cell that works in that range? Potential
efficiency = 8 8-10 %

35. System Studies

41. Technology roadmap
zz Power
zz Demonstrate AFC on planar disks
zz Optimize for scintillator scintillator/PV Cell coupling
/zz Evaluate temperature sensitivity
zz Evaluate hetero vs homogeneous
zz Demonstrate stand stand-alone prototype
in space environment conditions

42. Technology Roadmap
zz Antimatter Storage
zz Demonstrate storage in electrostatic trap
zz Demo storage of macro macro-particle
zz Demo accumulation of hydrogen molecules
into pellets
zz Store pellets of SH SH2 in solid state units
zz Improve formation rate of Hbar atoms
zz Demo formation of H H2bar molecules
bar

43. Technology Roadmap
zz Antimatter Production
zz Demonstrate deceleration of FNAL beam
zz Construct cooling ring at FNAL –– 5e14/yr
zz Improve current and production at FNAL FNAL-
X100 to 1000
zz Build new production machine optimized for
pbar accumulation accumulation- 1-10 mg/yr

45. Phase II
zz Detailed mission profiles with g assist,
solar fly bys,
zz Full technology path development
zz Torsion experiment –– measure ΔΔp; ; ejecta
zz AFC Power cell demonstration
zz Storage –– electrostatic trap demo of pellet;
pellet formation and vaporization

46. ““Nat” is the Key
zz Two experiments in the past indicate a
range of 10,000 –– 100,000 atoms/fission
zz NOT surface fission but volumetric
zz NOT fast fission but SF
zz Ejection mechanism may depend on light
fragment/heavy fragment of normal fission
zz Real question is what is the momentum
transferred by the ejecta cloud

48. Summary
zz Kuiper Belt mission in 10 years is possible with
mg quantities of antihydrogen antihydrogen- not gm to kg
zz Sail concept appears feasible IF Nat is above
1000
zz New power concept may be applicable to
intrasolar system missions within next decade
zz Pbar sail is the lowest mass/lowest energy
consuming concept yet developed
zz POCs can be performed in Phase II
zz Concept may allow interstellar mission to be
launched within next 2 decades