Space Colonization Terra-forming

1. Space Colonization Terra-forming ASTR 1420 Lecture 25 Not in the Textbook

2. Space Colonization Space colonization in this lecture is in 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 the Earth • on planets • on satellites • free space • outside of the Solar System

3. Reasons why some humans living in Space • Survival of our species • $$$ : solar power satellites, asteroid mining, space manufacturing, etc. • Resources : sufficient supply of rare materials • lesson the burden on the Earth • spread our beauty(?) to the Universe Insulin crystal growth in space (left) versus on Earth (right) “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

4. 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. This simple design can generate 13.4 billion watts per second which is ~15 times more than annual energy consumption of USA

5. Things to be considered… • mass per person • radiation shielding • minimum size • leakage rates • cost • schedule

6. Materials and Energy • using material from Earth is very expensive due to larger gravity of Earth. • Also, large-scale project will impact the Earth community • Need to use materials from Moon, Mars, large asteroids • however, these objects lack volatiles (Hydrogen and Nitrogen). • solution?Jupiter’s Trojan asteroids have high content of water ice and other volatiles. • Solar energy is abundant in the space (no night, no cloud, no atmosphere). • Energy on the top of Earth Atmo. (watts/m2) = 1366 / d2, (d is distance in AU) • In developed countries, energy usage ~ 1000 watts/person • Export created energy back to Earth • Mars and Moon colonies may need to use nuclear energy • waste heats?  requires a large radiator!

7. Transportation and Communication • Transportation • expect millions of shuttle launches..  requires cheaper and less pollutant transportation devices. • hypersonic spaceplane, space elevator, mass driver, etc. • all other rocket technologies we studied last lecture! • Communication • for more distant colonies (e.g., Mars), a real time communication is impractical due to the light travel time (7 – 44 minutes lag). • email or voice mails…

8. Minimum population size • 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 long 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 “isolated” habitat population = 500

9. 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 resurfacing • although they recycle oxygen, it is not “closed” system. • they extract oxygen from sea water and dump CO2 outside. • Radiation protection: against harmful cosmic rays and solar wind. • 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. • Two experiments in1991 and 1994

10. Biosphere 2 : experiment of a “closed” ecosystem • Biosphere 2 in Arizona • a small, complex, manmade biosphere supported 8 people for 1+ years! • after 1 year, oxygen had to be replenished. savana and ocean coastal desert crew quarters Size of 2.5 football field. $200 million dollars. 1987-2007

11. 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).

12. O’Neil’s habitat (1974) • Good locations are L4 & L5 points. one of O’Neil’s three designs called “Island Three”: two very large, counter-rotating cylinders, each 5 miles (8 km) in diameter and 20 miles (32 km) long

13. Other variants Toroidal and Spherical colonies. Bernal Spheres.

14. Objections • Even if the technology was 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?

15. Counter arguments • argument of need “population growth and limited resources on Earth” By 2040, population will be 10 billion!, gem stones, power, etc. • argument of cost Cost of wars since 2001 = $1.32 trillion USD • argument of benefits despite the high cost of initial investment… space colonies can provides precious metals, gem stones, power, etc. • the smallest Earth-crossing asteroid 3554 Amun (~2km): iron, nickel, cobalt, platinum etc (30x the amount ever mined. $20 trillion USD)

16. Terraforming planetary engineering : process of deliberately modifying atmosphere, temperature, surface topography, or ecology of celestial objects to fit our purposes

17. 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 Myr to 100 Myr)? • How ? • 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.

18. Method? • Put several, large solar mirrors to direct light to the Martian surface (to increase T) • Bring one of ice moons of Jupiter or Saturn induce an impact with an ~1,000 km object to melt the whole thing which will re-liquefy the core  magnetic field!

19. Terraforming Venus Requirements : • 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

20. How? • Solar shade at L1 • reflector on the ground or in the atmosphere • use of genetically engineered bacteria which can turn CO2intoother organics • induce an impact with 500-700km asteroid (to eliminate atmosphere fast)

21. Europa • a good potential candidate for terraforming • One clear advantage of Europais the presence of liquid water Difficulties • huge radiation (in the middle of Jupiter’s radiation belt; On Europa, a human would die from the radiation within ten minutes on the surface) • 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

22. In summary… Important Concepts Important Terms Terraforming Biosphere 2 Bern sphere ONeil’s habitats • Closed ecosystem experiments • Space habitat • Pros and cons of space habitats • TerraformingMars, Venus, etc. • Chapter/sections covered in this lecture : Not from the textbook • Human and Environment : next class!