13 June 2018 Nuclear Propulsion in Space 1

Nuclear propulsion in space

Intercan Technologies

Acknowledgments

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Ad Astra for copyright material on their ion engine

NASA Tech Docs and archives

Jet Propulsion Labs JPL/Caltech

Fraunhofer Institute for Physical Measurement Techniques IPM

Fundamentals

Nuclear has been associated with Fission, Fusion and Weaponry

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Public associates nuclear with weaponry

Science defines it as “…. Anything that relates to, or pertains to, the nucleus of the atom “

Has Recycled Weaponry Been Used For Space Propulsion ?

The US began Project Prometheus in 2003 with a budget of $430 M but demised it in 2005 …. But why?

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Russia started it decades ago, abandoned it, recently restarted.

Cite: Cosmos 954 accident over Canada scattering radioactive debris over 100000 sq. km. Some fragments at around 5 Sv/h

Energies in Fusion vs Fission

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Σ x = 1+ x + x2 + x3 + x4 ………………+ x70 +.…+ x75 +.......+ xn-1

2.6 x 10+14 n/cm2/s

Where:x = number of neutrons released

For Uranium x = 2.43 neutrons per disintegration, and can accelerate to 5 neutrons per disintegration.

For Plutonium x > 3.5 neutrons per disintegration and accelerates too.

Using Nuclear Energy ?

The Chain Reaction

in sustained nuclear fission follows a definite

mathematical equation……Geometric Progression:

Make Up of Fission Weapon

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Nuclear Propulsion in Space13 June 2018 8

Explosion Baker July 25, 1946 21 Kilotons

Nuclear Propulsion in Space

Initiation of Blast in Slow Motion

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TRINITY – first nuclear explosion

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"Now I am become Death, the destroyer of worlds."

Robert Oppenheimer, the father of atomic weaponry quoted from the Bhagavad Gita

(Sanskrit) भगवद्गीता

Nuclear Propulsion in Space

Fusion Weapon Triggered by Fission Weapon

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Edward Teller, father of the hydrogen bomb

Nuclear Propulsion in Space

Hydrogen Weapon

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From what we have seen …. Neither fission nor fusion are pragmatic methods of propulsion

Pu-238 is used. 1 kg Pu-238; golf ball sized ≡ 22MWh of energy

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Pu-238 cannot sustain a nuclear reaction e.g. in a reactor nor for nuclear weapons

Pu-238 decay produces a bounty of alpha particles. If enclosed in a noble gas, the alpha strips the electrons which then migrate to an anode, producing electricity. The decay heat of the Pu is used to keep the instruments warm. Projected for use in cardiac pacemakers,

space satellites and navigation beacons

Decay heat is 0.56 W/g

560 W/kg

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Why not use Pu-239Pu-238 β decay to U-234 releases 5.593 MeV per disintegration

Pu-239 β decay to U-235 releases 5.245 MeV per disintegration

Russia and USA stopped producing Pu-238 due to political treaties on nuclear disarmament and non proliferation. Pu-238 has become scarce

How to Make Pu-238

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Pu-238 is obtained by bombarding Uranium-235 with Deutrons (Heavy Water hydrogen).Neptunium-238 results as an intermediate product, which then decays to formplutonium-238. Plutonium-238 decays to Uranium-234 and then further along theRadium decay chain series to Lead-206

Generating Power from Pu-238

Thermoelectric Generator (RTG or RITEG)

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Thermocouples !!!

Used on Curiosity Martian Rover comprises 572 thermocouples. Producing 4410 W using Silicon Germanium that can produce >300 µV/°C.

Thermocouple Outputs

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Type K thermocouple output 46.8 µV/°C. Typical outputs are in region of 1 µA/°C

An RTG Assembly produces 10A - 8.75 A from Silicon Germanium junctions even after several months decay of Pu-238

Conversion rate is 0.12We /Wt

Hence a new material is being researched

Skutterudite Cobalt-Arsenide material named after Skotterud, a

city in Norway, with varying amounts of Ni and Fe

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Skutterudites with zinc antimonide tested at JPL exhibited higher conversion efficiency

Skutterudite thermocouple electricity generators are also being developed to convert car exhaust heat to electricity to recharge batteries or enhance hybrids.

Volt-Amp relationship of a 32 SkutteruditeThermocouple cluster

Multiple module Skutterudite generator that works up to 500 °C. Source Franhaufer

Also considered to power heart pacers !!

Space Craft Power

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RTG Power for Successful Space Missions

Mission Destination Longevity after BOM

Quantity of Pu-238

BOM Electrical Output

Flight Mass

kg

Operating

Voltage

Internal Ω

Resistance

Galileo Jupiter orbiter 4.2 years

(71000 h)

8.1 kg per

RTG

470 We for two

RTG’s

55.95 30 2.197

Ulysses Sun’s Polar

Mission

4.7 years

(42000 h)

8.1 kg per

RTG

245 We 55.81 28 2.279

Cassini Saturn and Moon

Titan

At BOM

After 16 y

8.1 kg per

RTG

826 We

596 We

56.31 30 2.229

New

Horizons

Pluto and Moon

Charon; then to

Kuiper Belt 2020

At BOM

On-going 9.5 y

orbit Pluto

8.1 kg per

RTG

237 We

191 We

57.91 30 2.229

Acronyms:

BOM: Beginning of Mission. Longevity and hours do not match due to fuel enrichment and what decay had already

occurred.

EOM: End of Mission. Source Bennet & Lombardo etal.

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Radioisotope Thermoelectric Generators Used On :

Galileo Spacecraft Orbiting Jupiter. One of two RTG’s shown at top

New Horizons Spacecraft flying by Pluto . Moon Charon in background. RTG shown on left

Cassini Spacecraft shown over Titan , a Saturn Moon. Two of three RTGs shown near top

Radiation from Pu-238

Rate of neutrons released from PU-238 is ~5.9 x 103/s per gram

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Equivalent to 0.2 – 0.5 mSv/h in the shown configuration

Gamma dose rate varied from 0.05 mSv/h (twice allowable in nuclear power plants) to 0.10 mSv/h

Not considered damaging for this type of equipment

Nuclear vs Chemical Rockets

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Why Nuclear ?

Introduce Ion Thrusters and Specific Impulse Isp (s)

Comparisons of Ion Thrusters

Engine Propellant Specific Impulse Isp Power kW Thrust mN

NEXT Xenon 4190 6.9 236

Annular Engine Xenon 5000 14 Under test

VASIMR Argon 3000-30000 200 ~ 5000

Hall Effect Bismuth 8000 140 2500

Hall Effect Xenon 2900 75 2900

Dawn Spacecraft Xenon 3100 Solar panels10 kW on Earth

90

Specific Impulse (Isp) is a way of describing the efficiency of a rocket. It represents the impulse, the change in momentum, per unit amount of propellant fuel used. Its units are in seconds (time)

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under test and futuristic

Has 2 gimballed thruster assemblies Logged 51000h ground testing without failure

13 June 2018 Nuclear Propulsion in Space 25Source : NASA Glenn Research Center

NEXT: Nasa Evolutionary Xenon Thruster Ion Engine

VASIMR Engine Variable Specific Impulse Magnetoplasma Rocket

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Hall Effect Thrusters Based on the Lorentz Force

Metallic Hydrogen

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Pressure Comparisons

Location Typical Pressure psi

Sea Level 14.7

Marianna Trench 7 miles salt water8 tons = 17820

Carnegie Institution Diamond Anvil

50 M

Centre of Jupiter 109

Neutron Star 1021

When cooled further it becomes a solid

Used as rocket fuel in its super cold liquid

At intense pressures, >50 M psi it becomes metallic and superconductive

Metalization occurs: 67.4 – 72.53 Mpsi at 5.5 °K

Diamond anvils were used for pressurization

Claimed energy ensity as 270 kJ/cm3 about 35 times more explosive than TNT

Source Harvard University Diaz & Silvera

Still a lab experiment

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RTG

What is the time NOW on Mars ?

http://mars.nasa.gov/msl/mission/instruments/environsensors/rems/

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Thankyou for

Your Attention

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Lengths of videos

Explosion Baker 1:58

Slow motion 0.05

H-weapon 0.36

Spacecraft Power, NASA 3.09

Why nuclear 1:20

VASIMR 1:25

Time on Mars 1:30

TOTAL 10.03

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