The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development •...

66
Nuclear Power in Space Exploration Nuclear Power in Space Exploration and the and the Associated Environmental Safeguards: Associated Environmental Safeguards: A Preliminary Overview A Preliminary Overview by Michael D. Campbell, P.G., P.H. Chair, Uranium Committee Energy Minerals Division, AAPG and Member of the Astrogeology Committee, AAPG and Managing Partner M. D. Campbell and Associates, L.P. Houston and Seattle Presented as Featured Speaker at the Houston Geological Society, Environmental and Engineering Geology Group Dinner. Houston, Texas January 20, 2009

Transcript of The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development •...

Page 1: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Nuclear Power in Space ExplorationNuclear Power in Space Exploration

and theand the

Associated Environmental Safeguards:Associated Environmental Safeguards:

A Preliminary OverviewA Preliminary Overview

by

Michael D. Campbell, P.G., P.H.Chair, Uranium Committee

Energy Minerals Division, AAPG andMember of the Astrogeology Committee, AAPG

andManaging Partner

M. D. Campbell and Associates, L.P.Houston and Seattle

Presented as Featured Speaker at the Houston Geological Society, Environmental and Engineering Geology Group Dinner.

Houston, TexasJanuary 20, 2009

Page 2: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Investigation ParticipantsInvestigation Participants

A Report of the Uranium Committee of the Energy Minerals Division, AAPG

by

Michael D. Campbell, P.G., P.H., (Chair)Houston

Jeffery D. King, P.G. (Associate)Seattle

Henry M. Wise, P.G. (Member)Houston

Bruce N. Handley, P.G. (Member)Houston

M. David Campbell, P.G. (Associate)Houston

Page 3: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Uranium Committee Report* OutlineUranium Committee Report* Outline

Introduction ……………………………………..

Satellites …………………………………………

Lunar-Solar or Lunar-Nuclear Power …………

Spacecraft Propulsion …………………………..

Planet-Based Power Systems ……...

Earth-Based Power Systems ………

Environmental Safeguards in Orbit ……………..

Other Environmental Considerations in Space ...

International Development

The Nuclear Genie is Out of the Bottle ………….

Research and Development: …………………….Small Earth-Based NPSs …………………

Direct-Conversion Systems ……………

Problems to be Solved …………………………..

Off-World Mining: ………………………………

The Debate on a Lunar or Mars Base …

Mining Asteroids ………………………

The Space Elevator ……………………………..

Near-Earth Asteroids and Comets …....................

Earth-Based Spin Off from Space Research ….

Conclusions ……………………………………...

Acknowledgements ………………………………

References (with links) ……………………………

* Note: The full report will be released after the 2009 AAPG-EMD Conference in Denver, Co., dated: June 7-10

Page 4: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Outline for this PresentationOutline for this Presentation

• Spacecraft Propulsion Planet-Based Power Systems Earth-Based Power Systems

• Environmental Safeguards in Orbit

• International Development: The Nuclear Genie is Out of the Bottle

• World Uranium Occurrences

• Dual Objectives: Using Nuclear Power also to Explore for Uranium, Thorium, and Special Commodities

Page 5: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Outline for this PresentationOutline for this Presentation

• Off-World Mining

The Debate on Lunar Mining

Mining Asteroids

The “Space Elevator”

The “Space Tractor”

• Earth-Based Spin Off from Space Research

Page 6: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Source of Energy in SpaceSource of Energy in Space

• Spacecraft Propulsion Planet-Based Power Systems Earth-Based Power Systems

Electrical Systems• Batteries

• Solar Cells

• Nuclear Power– Radioisotope Thermoelectric Generators

– Thermoelectric Generators

– Radioisotope Heater Units

Page 7: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

After: IAEA (2005)

Source of Energy in SpacSource of Energy in Space

Page 8: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Propulsion in SpacePropulsion in Space

• Chemical (Standard Rocket Propulsion)– Solid

– Liquid

• Kerosene/Oxygen

• Hydrogen/Oxygen

• Hydrozene/Oxygen

NASA

NASA

Page 9: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Propulsion in SpacePropulsion in Space

• Electrical (Ion Propulsion)– Chemical

• Batteries

• Fuel Cell

– Solar

– Nuclear

• Radioisotope Thermoelectric Generators

• Thermoelectric Generators

• The higher the electrical output, the higher the thrust

Homer

Page 10: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

(after IAEA 2005)

Chemical Propulsion vs. Nuclear PropulsionChemical Propulsion vs. Nuclear Propulsion

Page 11: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

(Reddy, 2008)

Page 12: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Environmental SafeguardsEnvironmental Safeguards

• Nuclear power to be used only in a stable orbit or in interplanetary space ….recent developments.

• Fuel is heat-resistant ceramic plutonium oxide:

– Reduces chances of vaporization by fire or re-entry

– Highly insoluble

– Fractures into large pieces

• Fuel has its own heat shield and impact casing to reduce chance of release in case of accident.

• Reactor will remain subcritical if immersed in fluids such as water or fuel.

• Two independent systems to reduce reactivity to a subcritical state and not subject to a common failure mode.

Page 13: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

International DevelopmentInternational Development

• The genie is out of the bottle

• Space programs in 20 countries and the European Union:

– Solar and fuel cells are sufficient for earth orbit and the inner planets– Nuclear power needed for the outer planets

• Most programs are communication, weather and surveillance

• U.S., Russia, and China have manned space programs

• China is planning to establish a mining base on the Moon

• India, Korea, and others have space programs under way

• Lunar bases will utilize nuclear power for long-term use and

• Solar power may also play a significant role.

Page 14: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

IAEA (2008)

Page 15: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Exploration Objectives in the Solar System: 1Exploration Objectives in the Solar System: 1stst –– The MoonThe Moon

• Uranium

• Thorium

• Special Commodities

• Rare Earths

• Metals

• Helium-3

NASA

Page 16: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Primary NuclearPrimary Nuclear--Fuel Resources on EarthFuel Resources on Earth

Cenozoic Deposits

Wyoming (Roll-Fronts- Developed by In Situ Methods)

Nebraska (Roll-Fronts – Developed by In Situ Methods)

South Dakota (Roll-Fronts – Developed by In-Situ Methods)

Texas (Roll-Fronts- Developed by In Situ Methods)

Kazakhstan (Roll-Fronts- Developed by In Situ Methods)

Uzbekistan (Roll-Fronts- Developed by In Situ Methods)

Australia (Roll-Fronts- Developed by In Situ Methods)

Mesozoic Deposits

Canada Western (Mining Only)

Canada Eastern (In Situ and Surface Mining Methods)

Colorado Redistributed Roll-Fronts – In Situ Methods & Surface Mining Methods)

New Mexico Redistributed Roll-Fronts – In Situ & Surface & Underground Mining Methods)

Paleozoic Deposits

Arizona (Developed by Surface Mining Methods)

Niger (Surface Mining)

Proterozoic Deposits

Canada (Surface and Underground Mining)

Australia (Surface Mining)

Guyana (Surface and Underground Mining)

Gabon (Surface and Underground Mining)

Namibia (Surface and Underground Mining)

Page 17: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

(After Kesler, 1994)

Page 18: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

IAEA (2008)

Page 19: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European
Page 20: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Now

?

Page 21: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Commodities Presently Imported to U.S.Commodities Presently Imported to U.S.

Page 22: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

NearNear--Earth Asteroids and CometsEarth Asteroids and Comets

• Monitoring Near-Earth Asteroids (NEAs) and Comets

• The Moon can be a base for monitoring NEAs

• Remote sensing satellites inside Venus’s orbit

• Ways to move NEAs away from collisions with earth

• Nuclear power will be used to power most of these

Page 23: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Defense of Earth ?Defense of Earth ?

• Improved Monitoring NEAs,

• Telescopes on Moon or

in Orbit.

• Respond with Robotics:

“Gravity Tractor” or other

Equipment.

Page 24: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

“Gravity Tractor” “Gravity Tractor”

Page 25: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

OffOff--World MiningWorld Mining

• Mining on Moon, Mars, etc.

• Mining Near-Earth Asteroids and Comets

• The “Space Tractor” (Manages Threats to Earth)

• The Space Elevator (Reduces “Lifting” Costs)

• Off-World Mining Preferable to Mining on Earth?

• When Will it Make Sense?

Page 26: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Lunar ExplorationLunar Exploration

• Lunar Prospector (1998)

– Mapped surface Indications of key elements

• H, U, Th, K, O, Si, Mg, Fe, Ti, Al, Ca, H2O

• Additional mapping to be conducted

– Ni, Co, Samarium, other rare-earth elements

– Structural geology

– Confirmation of earlier aerial photography, aerial geophysical, and remote sensing

Page 27: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Lunar Apollo Exploration Lunar Apollo Exploration –– Phase I Phase I –– 1960s1960s--1970s1970s

Copernicus

Page 28: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Lunar Apollo Exploration Lunar Apollo Exploration –– Phase I Phase I –– 1960s1960s--1970s1970s

NASA

Page 29: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

The Last Geologist on the Moon (William “Jack” Schmitt)

Apollo 17, 1972 (NASA Photo)

Apollo 17 - Reconnaissance Site 16

Lunar Sampling

NASA

Page 30: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Lunar Apollo Exploration Lunar Apollo Exploration –– Phase I Phase I –– 1960s1960s--1970s1970s

NASA

Apollo 17 - Reconnaissance Site 13

Page 31: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Lunar Exploration Lunar Exploration –– Phase I Phase I –– 1960s1960s--1970s1970s

NASA

Page 32: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Lunar South PoleLunar South Pole

Deep Shadows

Water Ice?

NASA

Page 33: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Back Side of MoonBack Side of Moon

Maria

NASA

Page 34: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Deep Shadows

Water Ice?

Aristarchus

Tycho

Copernicus

Langrenus

Mare Imbrium

Oceanus ProcellarumMare Tranquillitatis

Mare Serenitatis

Plato

Apollo 11 Site

Common Lunar Sites Common Lunar Sites

NASA

Page 35: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Anomalous Th

From Elphic, et al., 2000.

Copernicus Crater

Page 36: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

(Skinner and Gadis, 2008)

Copernicus CraterCopernicus Crater

USGS Geologic Map of the Moon

I-515 – Aristarchus – 1967 – Schmitt, Trask, and Shoemaker Approx. 30 miles

N

Page 37: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Highland AreaHighland Area

ofof

Thorium AnomaliesThorium Anomalies

USGS Geologic Map of the Moon

I-355 Kepler -1962 - Hackman Approx. 30 milesN

Kepler Crater

Page 38: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Anomalous Sm

From Elphic, et al., 2000.

Copernicus Crater

Page 39: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

HighlandHighland Area of Area of

Samarium AnomaliesSamarium Anomalies

USGS Geologic Map of the Moon

I-465 – Aristarchus – 1965 - MooreApprox. 30 miles

N

Page 40: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

HeliumHelium--3 Resources in the Maria3 Resources in the Maria

Copernicus

Tyco

Page 41: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Mining on the MoonMining on the Moon

(Courtesy of Popular Mechanics)

Page 42: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European
Page 43: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Analogues from Earth?Analogues from Earth?

Oklo Deposit Oklo Deposit -- GabonGabon

Proterozoic

Reactions Dated at 1.6 Billion Years

Natural ?

USGS

Page 44: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Natural Nuclear Reactors ?Natural Nuclear Reactors ?

Oklo Deposit Oklo Deposit -- GabonGabon

Significance?

• Mineralization may have analogues off-world.

• Would leave radioactivity behind…”breadcrumbs” to find in the Solar System.

USGS

Page 45: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Mars is Beginning to Show Some PromiseMars is Beginning to Show Some Promise

Angular Unconformity in Victoria Crater?

NASA

Page 46: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Bedding on Mars

Volcanics ?

CO2 or Ice ?

USGS

Page 47: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Mars is Beginning to Show Some PromiseMars is Beginning to Show Some Promise

Carbonates mean H20 may be present…

Yellow – Banded Olivine-bearing Rocks

Blue – Fe-Mg Smectites

Green – Alteration of olivine by

interation with H2O to form

carbonate.

NASA

NASA

Page 48: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Valles Marineris

Volcanics? Organics?

Page 49: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Mapping of Mars ImprovingMapping of Mars Improving

Page 50: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Methane on Mars: Biological or Geochemical?Methane on Mars: Biological or Geochemical?

Cross Section of Mountain

Pathways of CH4

Heat Source: Volcanic?

CH4

High CH4

• Seasonal

• North and South Hemispheres

NASA

Valles Marineris

Page 51: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Methane on Mars: Biological or Geochemical?Methane on Mars: Biological or Geochemical?

Cross Section of Mountain

Pathways of CH4

Heat Source: Volcanic?

CH4

NASA

Significance? Could be indication that Earth-type mineralization is possible on Mars

and on other bodies in Solar System.

Water Table ?

Page 52: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

USGS Gas Hydrate Research

Analogues from Earth?Analogues from Earth?

Page 53: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

USGS Gas Hydrate Research

Analogues from Earth?Analogues from Earth?

Page 54: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

NASA

Even Water ?Even Water ?

NASA

Page 55: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Mining AsteroidsMining Asteroids

• Asteroid Types

M – Metal Type

• Iron, Nickel, Cobalt, Platinum-Group

C – Carbonaceous Chondrite

• Hydrated Minerals

S – Stony Type

• Iron and Magnesium Silicates

Page 56: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

M – Metal Type

S – Stony Type

Iron, Nickel, Cobalt, Platinum-Group

Iron and Magnesium Silicates

NASA

NASA

Page 57: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

The economic and technical requirements are:

1. A market for the products produced and delivered,

2. Adequate spectral data indicating presence of the

desired materials,

3. Orbital parameters give reasonable accessibility and

mission duration,

4. Feasible concepts for mining & processing,

5. Feasible retrieval concepts, and

6. Positive economic Net Present Value, using appropriate

geological and engineering concepts.

What about the Economics of Mining in Space?What about the Economics of Mining in Space?

Page 58: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

What about the Economics of Mining in Space?What about the Economics of Mining in Space?

After Sonter, (1998)

Page 59: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

New Ways to Achieve a Stable Orbit.New Ways to Achieve a Stable Orbit.

• Need to Reduce Lifting Costs by Heavy Rockets: Present Cost is about $10,000 per Pound of Payload into Stable Orbit.

• Scram-Jet Space Planes, Lunar Catapults, etc. being Evaluated.

• Other Approaches Available but Untested.

• Favorable Science and Engineering Environments Present in Various Countries Interested in Space…China, India, Russia, etc.

• All Efforts Requires Political Will and the Funds to Support Them.

Page 60: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Orbital Achievement with Payloads

Lunar Catapults for

Return Flight Carrying

Products Back to Earth

NASA

NASA

Page 61: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Leading the List: The “Space Elevator”Leading the List: The “Space Elevator”

• The “Space Elevator”

• Conferences, including Boeing, Lockheed, Microsoft, etc.

• Carbon nanotube technology has lead to stronger materials that are strong and flexible enough for the elevator’s requirements.

• Nuclear power will be utilized to power the electric motors.

Page 62: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

NASA

Page 63: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

NASA

Page 64: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

Direct Benefit to Date?Direct Benefit to Date?

EarthEarth--Based Spin Off from Space ResearchBased Spin Off from Space Research

• Best Example: Hyperion Power Generation, Inc.

• Transportable “Pocket” Nuclear Power Plant

• $20-30 Million each

• 25 MWe - Electricity for 20,000 U.S. Residents or energy

during and after disasters, or provide power for

remote mining operations.

• 30 years life

Page 65: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

NASA

Page 66: The Need for Nuclear Power in Space Exploration · 2018. 6. 24. · International Development • The genie is out of the bottle • Space programs in 20 countries and the European

or ?

Into Space or ?Into Space or ?

xxx