Space Colonization

Terra-formingASTR 1420

Lecture 26Not in the Textbook

Space Colonization

Space colonization in this lecture is a narrow sense : colonization by human and in the Solar System only (say within next few millennia).

• Also known as space settlement, space habitation, etc.

Space colonization = self-sufficient human habitation outside Earth

o on planetso on satelliteso In free spaceo outside the Solar System eventually

Reasons why some humans will live in Space

• Survival of our species• $$$ : solar power satellites, asteroid mining, space manufacturing, etc.• Resources : sufficient supply of rare materials• lessen the burden on the Earth• spread our beauty(?) to the Universe

“The long-term survival of the human race is at risk as long as it is confined to a single planet. Sooner or later, disasters such as an asteroid collision or nuclear war could wipe us all out. But once we spread out into space and establish independent colonies, our future should be safe.” Stephen Hawking

Insulin crystal growth in space (left) versus on Earth (right)

Space solar power station (immediate feature)

A space-based solar power station will use an array of mirrors to concentrate the sun’s rays on photovoltaic cells. The electricity produced is converted into a powerful microwave beam directed at an antenna on Earth, where it is converted back into electricity and fed to the grid.

Advantages of space:•No atmosphere! •No day-night limitation!•No weather! •~40 times efficient!

Space Solar Power Station

• Solar energy is abundant in the space (no night, no cloud, no atmosphere).• Energy (watts/m2) = 1366 / d2, (d is distance in AU)• In developed countries, energy usage ~ 1000 watts/person• Export created energy back to Earth

Things to be considered for space habitats

• mass per person• radiation shielding• minimum size• leakage rates• cost• schedule

Materials and Energy

• using material from Earth is very expensive due to larger gravity of Earth.o Also, large-scale projects will impact the Earth communityo Use materials from Moon, Mars, large asteroidshowever, these objects lack volatiles (Hydrogen and Nitrogen).

• Jupiter’s Trojan asteroids have high content of water ice and other volatiles.

• Mars and Moon colonies may need to use nuclear energyo waste heats? requires a large radiator!

Transportation and Communication

• Transportationo expect millions of shuttle launches..

requires cheaper and less pollutant transportation devices.

o hypersonic spaceplane, space elevator, mass driver, etc.

o all other rocket technologies we studied last lecture!

• Communicationo for more distant colonies (e.g., Mars), a real

time communication is impractical due to the light travel time (7 – 44 minutes lag).

o email or voice mails…

• To prevent inbreeding reduced fertility, genetic disorders, infant mortality, malfunctioning immune system, etc.

• In 2002, anthropologist, John H. Moore.population of 150-180 would allow normal reproduction for 60—80 generations (~2,000 population for a long-term survival).

• “50/500” rule: conservation biologists, 50 is the minimum to prevent an unacceptable rate of inbreeding, 500 is required to main overall genetic variability.

Minimum population size

Life support

• We need air, water, food, mild temperature, and gravity.• In space, closed ecological systems must recycle (or import) resources

• Nuclear submarine : carry out missions for months without resurfacingo although they recycle oxygen, it is not “closed” system. o they extract oxygen from sea water and dump CO2 outside.

• Genetic engineering, terrahumanism, cyborg to be more compatible with the environment?

• Radiation protection: against harmful cosmic rays and solar wind. o Either we need 5—10 tons of blocking (absorbing) material per square meter of surface

habitat area. Or we can make the hull-metal electric to protect against charged particles.o Two experiments; 1991 and 1994

Biosphere 2

• Biosphere 2 in Arizonao a small, complex, manmade biosphere supported

8 people for 1+ years!o after 1 year, oxygen had to be replenished.

savana & ocean

coastal fog desert

crew quartersSize of 2.5 football field. $200 million dollars. 1987-2007.

Bernal Sphere

• a type of space habitat intended as a long-term home for permanent residents, first proposed in 1929 by John Desmond Bernal (Irish Scientist).

O’Neil’s habitat

• Good locations are L4 & L5 points.

Other variants

Toroidal and Spherical colonies. Bernal Spheres.

Objections

• Even if the technology becomes available, and the costs of deploying a program relatively low, and the likelihood of success relatively high, only a small number of people would directly benefit from a colony (either enthusiastic colonists or high risk commercial interests), leaving most of financial burden on the public.

• Humans are treated as assets

• If the main reason is “insurance” against the annihilation of human, then why people on Earth need to pay for something useful only after their deaths?

Counter arguments

• argument of need“population growth and limited resources on Earth” By 2040, population will be 10 billion!

• argument of costIRAQ+Afghanistan war = $813 billion + $632 = about $1.445 trillion

• argument of benefitsdespite the high cost of initial investment…space colonies can provides precious metals, gem stones, power, etc.

Space mining

• the smallest Earth-crossing asteroid 3554 Amun (see orbit) is a mile-wide (2 km) lump of iron, nickel, cobalt, platinum, and other metals; it contains 30 times as much metal as Humans have mined throughout history, although it is only the smallest of dozens of known metallic asteroids and worth perhaps USD $20 trillion if mined slowly to meet demand at 2001 market prices.

Terraforming

Terraforming

process of deliberately modifying atmosphere, temperature, surface topography, or ecology of celestial objects to fit our purposes

= planetary engineering

Terraforming Mars

• Two things: atmosphere and heating

• Once it is terraformed to be similar to Earth, will it be able to sustain the condition over geological timescales (10s Myrs)?

• Small size is the main issue…

• Re-heating the core of Mars is considered an impractical solution

• the slow loss of atmosphere could possibly be counteracted with ongoing low-level artificial terraforming activities.

How?

• Bring one of ice moons of Jupiter or Saturn

• Put several, large solar mirrors to direct light to the Martian surface (to increase T)

• Magnetic field!!! induce an impact with ~1,000 km object to melt the whole thing which will

re-liquefy the core

Terraforming Venus

• removing most of the planet's dense 9 MPa carbon dioxide atmosphere

• reducing the planet's 450 °C (850 K) surface temperature

• Addition of O2

• Reduce the length of day(?) : 117 Earth days

Terraforming Venus

How?

• Solar shade at L1• reflector on the ground

or in the atmosphere • use of genetically

engineered bacteria (CO2 other organics)

• induce an impact with 500-700km asteroid (to eliminate atmosphere)

Europa• a good potential candidate for terraforming• One advantage to Europa is the presence of

liquid water

Difficulties• huge radiation (in the middle of Jupiter’s

radiation belt)o require the building of massive radiation

deflectors, which is currently impractical• satellite is covered in ice and would have to

be heated• need for oxygen electrolysis of ocean water

In summary…

Important Concepts• Space habitat• Pros and cons of space habitats• Space mining• Various designs• Terraforming Mars, Venus, etc.

Important Terms• Terraforming

Chapter/sections covered in this lecture : Not from the textbook