The long-term survival of the human race is at risk as long as it is ...

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Dec 14, 2012 (4 years and 6 months ago)

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Space Colonization

Terra
-
forming

ASTR 1420


Lecture 25


Not 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
millenia
).




Also known as space settlement, space habitation, etc.


Space colonization = self
-
sufficient human habitation outside Earth


o
on planets

o
on satellites

o
free space

o
outside the Solar System

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


“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

Space solar power station (immediate feature)


Things to be considered…




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 project will impact the Earth community

o
Use materials from Moon, Mars, large asteroids


however, these objects lack volatiles (Hydrogen and Nitrogen).


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 (watts/m
2
) = 1366 / d
2
, (
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

o
waste heats?


requires large radiator!


Transportation and Communication


Transportation

o
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!



Communication

o
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 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 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 resurfacing

o
although they recycle oxygen, it is not “closed” system.

o
they extract oxygen from sea water and dump CO
2

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 Arizona

o
a small, complex, manmade biosphere supported

8 people for 1+ years!

o
after 1 year, oxygen had to be replenished.


Bernal Sphere


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

O’Neil’s habitat


Good locations are L4 & L5 points.

Other variants

Toroidal

and Spherical colonies. Bernal Spheres.

Objections


Even if the technology were 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 cost

IRAQ+Afghanistan

war = $786 billion + $397 = about $1.2 trillion


argument of benefits

despite the high cost of initial investment…

space colonies can provides precious metals, gem stones, power, etc.

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 O
2


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 (CO
2



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


Various designs


Terraforming

Mars, Venus, etc.

Important Terms


Terraforming


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

Human and Environment

: next class!