ERAU Space Physics Program 1

Space Physics Program College of Arts & Sciences

ERAU-Prescott

Dr. Darrel Smith

World Space Congress October 17, 2002

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Outline1. The Space Physics degree program

2. Motivation for advanced propulsion

3. Antimatter propulsion

4. Possible missions (timescales)

5. Experiment to measure Isp

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B.Sc. Space Physics Degree Program

1. Nick Devereux’s talk (yesterday)Space Science Education & Outreach

2. Program Starts Fall 2003

3. Four areas of concentration

Embry-Riddle Aeronautical University

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MotivationWhy Antimatter Propulsion ? The “long” mission

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Problems with the “long” mission

1. Prolonged zero-g environmentWeightlessness triggers a reduction in density ofweight-bearing bones

1-2% a month

severe osteoporosis

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Problems with the “long” mission

2. Radiation ExposureMars vehicle is no longer shieldedfrom galactic and solar radiation

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Advanced Propulsion Systems

Goal: Obtain the highest Isp

Antimatter Isp ~ 107 sec.

1. Antiprotons

2. Positrons

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Antiprotons

€

p = E 2 c 2 − mo2c 2

Momentum Thrust

The production of massiveparticles reduces the thrust.

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Positrons

Momentum Thrust

The production of “massless”particles (e.g., photons) enhances the thrust.

“Photon Drive”

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The Engine

Positron-electron annihilationoccurs behind an absorber/reflector at the rear of the spacecraft.

thrust

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The Photon Drive

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Spacecraft Performance

€

F = ˙ p = Ma

F = 0.9925 ˙ m c = 0.9925 × (4.03×10−3 kgs ) × (3.0 ×108 m

s )

F =1.20 ×106 N

Specific Thrust:

Thrust:

€

Isp = F˙ m g

= 1.20 ×106 N4.03×10−3 kg

s 9.8 ms2

= 3.04 ×107 s

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Mission Parameters

Minimum flight time for rendezvous (Mars, Jupiter)

Use a Direct Trajectory Optimization Method (D.A. Kluever, 1997)

• Start in a heliocentric orbit with the same position, velocity vectors as the Earth.

• The spacecraft is transferred to heliocentric orbits around Mars and Jupiter

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Mission Parameters to Mars & Jupiter

Planet Mrocket Mpropellant Travel time

Mars 400 Mt 1.336 Mt 3.84 days

Jupiter 400 Mt 3.765 Mt 10.8 days

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Mission Parameters to -CentuariMrocket Mpropellant Velocity tt (years) to (years)

400 Mt 53.9 Mt 0.10 c 45.7 45.5

400 Mt 170 Mt 0.50 c 9.59 8.41

400 Mt 360 Mt 0.98 c 5.12 1.65

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Measuring the specific thrust

Store 1015 positrons in a Penning trap. G. Smith, LLL

Release the positrons in a time window of 100 s.

The positrons annihilate the electrons on a tungsten target which is mounted on a torsion pendulum.

We expect to measure a force of ~1.3 mN by measuring the amplitude of motion of the torsion pendulum.

This will be the first measurement of the specific thrust due to matter-antimatter annihilations.

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Conclusions

Something like a “photon drive” engine will be required to achieve interplanetary and interstellar manned space travel.

The major hurdle to overcome will be the technology required to produce and store many kilograms of positrons.

High-flux, relatively low-energy accelerators will be needed to produce the volume of positrons required. New accelerator technology is needed.

The need for compact, high-energy sources of fuel will be in high demand, so commercial markets may be the “driving force” in developing thisbreakthrough technology.

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