Astronauts and other spaceflight participants
have observed their religions while in space; sometimes publicly,
sometimes privately. Religious adherence in outer space poses unique
challenges and opportunities for practitioners. Space travelers have
reported profound changes in the way they view their faith related to
the overview effect, while some secular groups have criticized the use of government spacecraft for religious activities by astronauts.
ISS crew with festive Christmas hats aboard the Zvezda service module of ISS in 2009.Christmas morning in Node 3 in 2010.
Protestantism
Apollo 11 astronaut Buzz Aldrin, a Presbyterian, performed a communion service for himself using a kit provided by his church. Aldrin had told flight director Chris Kraft of his plans and intended to broadcast the service back to Earth but opted not to at the request of Deke Slayton, due to the continuing controversy over Apollo 8's reading.
A microfilm Bible that had been to the surface of the Moon was auctioned off in 2011. It was a King James Version created after three astronauts lost their lives in the Apollo 1 fire. Ed White, one of the astronauts who perished, had wanted to take a Bible to the Moon.
Several members of the crew of the Space Shuttle Challenger tragedy mission STS-51-L were people of faith. Among them were Commander Dick Scobee and Pilot Michael J. Smith. Scobee was a Baptist who met his wife June at a church social event. After the tragedy, she would go on to write an article in Guidepost Magazine
about how their faith helped her through the tragic time. Smith and
his family attended a non-denominational Christian church in a community
close to their home near Houston's NASA JSC Space Center.
Rick Husband, the Commander of the ill-fated STS-107Columbia
tragedy mission, was also a devout Christian. On the last-request forms
that astronauts fill out before every flight, he left his pastor a
personal note: "Tell them about Jesus; he's real to me." Later his wife
Evelyn wrote a book about their life with him as an astronaut and the
importance of their Christian faith entitled High Calling: The Courageous Life and Faith of Space Shuttle Columbia Commander Rick Husband(Audiobook). Likewise, his STS-107 crewmate Michael P. Anderson was also a devout Christian and when not on a mission for NASA, was an active member of the Grace Community Church choir.
Catholicism
A signed message from Pope Paul VI was included among statements from dozens of other world leaders left on the Moon on a silicon disk during the Apollo 11 mission. Following the mission, William Donald Borders, Bishop of the Roman Catholic Diocese of Orlando, told the Pope that the 1917 Code of Canon Law
placed the Moon within his diocese, as the first explorers had departed
from Cape Kennedy which was under his jurisdiction. The claim was
neither confirmed nor denied by the Pope, and the Moon is not recognized
as part of the diocese in any official capacity.
The Blessed Sacrament
(the body and blood of Christ in the form of consecrated sacramental
bread and wine) has been carried into space at least twice. Three Catholic astronauts on Space Shuttle mission STS-59 received Holy Communion on 17 April 1994. NASA astronaut Michael S. Hopkins took a supply of six consecrated hosts to the International Space Station in September 2013, allowing him to receive the Eucharist weekly during his 24-week mission.
A Russian Orthodox priest blesses the Soyuz rocket for ISS Expedition 31
Russian Orthodox Christmas was celebrated on the International Space Station, on January 7, 2011. Cosmonauts had the day off, but one of the other crew posted on Twitter, "Merry Christmas to all Russia." The whole crew also celebrated on December 25, two weeks prior.
Cosmonauts sometimes at the request of Russian Orthodox church
carry religious icons to space, which upon return to Earth are
distributed to churches.
Islam
Muslims
in space struggle with fulfilling their religious obligations including
kneeling and facing Mecca to pray in microgravity traveling at several
kilometres per second. The issue first came up when Sultan bin Salman bin Abdulaziz Al Saud, a Saudi prince, flew aboard STS-51-G and again when Anousheh Ansari flew as a tourist to the International Space Station. In preparation for Malaysian Sheikh Muszaphar Shukor's trip to the ISS in 2007, the National Fatwa Council
created "Muslim Obligations in the International Space Station"
outlining permissible modifications to rituals such as kneeling when
praying (not required in space), facing Mecca (or just Earth) when praying (left to the astronaut's best abilities at the start of prayer), and washing (a wet towel will suffice).
In February 2014, the General Authority of Islamic Affairs and Endowment (GAIAE) from Saudi Arabia issued a fatwa forbidding devout Muslims from participating as crew members in Mars One's proposed one-way mission to Mars.
Speaking for the clerical group, Farooq Hamada explained that,
"Protecting life against all possible dangers and keeping it safe is an
issue agreed upon by all religions and is clearly stipulated in verse
4/29 of the Holy Quran: Do not kill yourselves or one another. Indeed,
Allah is to you ever Merciful."
American astronaut Jeffrey Hoffman took multiple Jewish objects to space on his space flights from 1985 to 1996: a miniature Torah scroll, a yad, a Torah breastplate, mezuzot, menorahs, a dreidel, hand-woven tallit, and kiddush cups.
No space settlement has been constructed yet, but many design
concepts, with varying degrees of realism, have been introduced in
science-fiction or proposed for actual realization.
Space settlements include orbital settlements (also called orbital habitat, orbital stead, orbital city or orbital colony) around the Earth or any other celestial body, as well as cyclers and interstellar arks, as generation ships or world ships.
Space settlements are a form of extraterrestrial settlements, which more broadly includes habitats built on or within a body other than Earth, such as a settlement developed from a moonbase, a Mars habitat or an asteroid.
Habitat: pressurized volume(s) within which humans live and work, including relevant facilities for life support.
Settlement: group of permanently inhabited habitats installed near each other, possibly interconnected.
Infrastructure: set of constructed elements supporting
habitats and/or settlements such as (and not limited to): power plant,
water plant, greenhouse and waste management facilities, communication
facilities, transportation facilities, EVAs, roads, spaceport, research
platforms, and so on.
While not automatically constituting a colonial entity, a space settlement can be an element of a space colony. The term "space colony" has been viewed critically, prompting Carl Sagan to propose the term space city.
"The Brick Moon" – an 1869 serial by Edward Everett Hale – was the first fictional space station or habitat. (Described by other sources as a station or habitat.)
The idea of space settlements either in fact or fiction goes back to the second half of the 19th century. "The Brick Moon", a fictional story written in 1869 by Edward Everett Hale, is perhaps the first treatment of this idea in writing.
In 1903, space pioneer Konstantin Tsiolkovsky speculated about rotating cylindrical space settlements in Beyond Planet Earth.In 1929 John Desmond Bernal speculated about giant space settlements. Dandridge M. Cole
in the late 1950s and 1960s speculated about hollowing out asteroids
and then rotating the to use as settlements in various magazine articles
and books, notably Islands In Space: The Challenge Of The Planetoids.
Around 1970, near the end of Project Apollo (1961–1972), Gerard K. O'Neill, an experimental physicist at Princeton University, was looking for a topic to tempt his physics students, most of them freshmen
in engineering. He hit upon the idea of assigning them feasibility
calculations for large space-settlements. To his surprise, the habitats
seemed feasible even in very large sizes: cylinders 8 km (5 mi) in
diameter and 32 km (20 mi) long, even if made from ordinary materials
such as steel and glass. Also, the students solved problems such as
radiation protection from cosmic rays (almost free in the larger sizes),
getting naturalistic Sun angles, provision of power, realistic
pest-free farming and orbital attitude control without reaction motors.
O'Neill published an article about these colony concepts in Physics Today in 1974. He expanded the article in his 1976 book The High Frontier: Human Colonies in Space.
NASA Ames/Stanford 1975 Summer Study
Stanford torus exteriorCollage of figures and tables of Stanford Torus space habitat, from «Space Settlements: A Design Study» book. Charles Holbrow and Richard D. Johnson, NASA, 1977.
The result motivated NASA to sponsor a couple of summer workshops led by O'Neill. Several concepts were studied, with sizes ranging from 1,000 to 10,000,000 people, including versions of the Stanford torus. Three concepts were presented to NASA: the Bernal Sphere, the Toroidal Colony and the Cylindrical Colony.
Exterior of a 1970s Stanford adaptation of the Bernal sphere
O'Neill's concepts had an example of a payback scheme: construction of solar power satellites
from lunar materials. O'Neill did not emphasize the building of solar
power satellites as such, but rather offered proof that orbital
manufacturing from lunar materials could generate profits. He and other
participants presumed that once such manufacturing facilities had
started production, many profitable uses for them would be found, and
the colony would become self-supporting and begin to build other
colonies as well.
The concept studies generated a notable groundswell of public interest. One effect of this expansion was the founding of the L5 Society
in the U.S., a group of enthusiasts that desired to build and live in
such colonies. The group was named after the space-colony orbit which
was then believed to be the most profitable, a kidney-shaped orbit
around either of Earth's lunar Lagrange points 5 or 4.
Space Studies Institute
In 1977 O'Neill founded the Space Studies Institute, which initially funded and constructed some prototypes of the new hardware needed for a space colonization
effort, as well as producing a number of feasibility studies. One of
the early projects, for instance, involved a series of functional
prototypes of a mass driver, the essential technology for moving ores efficiently from the Moon to space colony orbits.
A number of arguments are made for space settlements having a number of advantages:
Access to solar energy
Space has an abundance of light produced from the Sun. In Earth orbit, this amounts to 1400 watts of power per square meter. This energy can be used to produce electricity from solar cells or heat engine based power stations, process ores, provide light for plants to grow and to warm space settlements.
Outside gravity well
Earth-to-space
settlement trade would be easier than Earth-to-planetary habitat trade,
as habitats orbiting Earth will not have a gravity well to overcome to export to Earth, and a smaller gravity well to overcome to import from Earth.
In-situ resource utilization
Space settlements may be supplied with resources from extraterrestrial places like Mars, asteroids, or the Moon (in-situ resource utilization [ISRU]; see Asteroid mining). One could produce breathing oxygen, drinking water, and rocket fuel with the help of ISRU. It may become possible to manufacture solar panels from lunar materials.
Asteroids and other small bodies
Most
asteroids have a mixture of materials, that could be mined, and because
these bodies do not have substantial gravity wells, it would require
low delta-V to draw materials from them and haul them to a construction site.
There is estimated to be enough material in the main asteroid
belt alone to build enough space settlements to equal the habitable
surface area of 3,000 Earths.
Population
A 1974 estimate assumed that collection of all the material in the main asteroid belt
would allow habitats to be constructed to give an immense total
population capacity. Using the free-floating resources of the Solar
System, this estimate extended into the trillions.
Zero g recreation
If a large area at the rotation axis is enclosed, various zero-g sports are possible, including swimming,hang gliding and the use of human-powered aircraft.
A space settlement can be the passenger compartment of a large spacecraft for colonizing asteroids, moons, and planets. It can also function as one for a generation ship
for travel to other planets or distant stars (L. R. Shepherd described a
generation starship in 1952 comparing it to a small planet with many
people living in it.)
Requirements
Configuration of a Stanford torus
The requirements for a space settlement are many. They would have to
provide all the material needs for hundreds or thousands of humans, in
an environment out in space that is very hostile to human life.
Regulation
The
governance or regulation of space settlements is crucial for
responsible habitation conditions. The physical as well as
socio-political architecture of a space settlement, if poorly
established, can lead to tyrannical and precarious conditions.
Initial capital outlay
Even
the smallest of the settlement designs mentioned below are more massive
than the total mass of all items that humans have ever launched into
Earth orbit combined.
Prerequisites to building settlements are either cheaper launch costs
or a mining and manufacturing base on the Moon or other body having low delta-v from the desired habitat location.
The optimal settlement orbits are still debated, and so orbital stationkeeping is probably a commercial issue. The lunar L4 and L5
orbits are now thought to be too far away from the Moon and Earth. A
more modern proposal is to use a two-to-one resonance orbit that
alternately has a close, low-energy (cheap) approach to the Moon, and
then to the Earth. This provides quick, inexpensive access to both raw materials and the major market. Most settlement designs plan to use electromagnetic tether propulsion, or mass drivers
used instead of rocket motors. The advantage of these is that they
either use no reaction mass at all, or use cheap reaction mass.
Protection can be attained through passive or active shielding. Passive shielding through the use of materials has been the method to shield current spacecrafts.
Water walls or ice walls can provide protection from solar and
cosmic radiation, as 7 cm of water depth blocks approximately half of
incident radiation.
Alternatively, rock could be used as shielding; 4 metric tons per
square meter of surface area could reduce radiation dosage to several
mSv or less annually, below the rate of some populated high natural background areas on Earth.
Alternative concepts based on active shielding are untested yet
and more complex than such passive mass shielding, but usage of magnetic
and/or electric fields, like through spacecraft encapsulating wires, to deflect particles could potentially greatly reduce mass requirements.
Air pressure, with normal partial pressures of oxygen (21%), carbon dioxide and nitrogen
(78%), is a basic requirement of any space settlement. Basically, most
space settlement designs concepts envision large, thin-walled pressure
vessels. The required oxygen could be obtained from lunar rock. Nitrogen
is most easily available from the Earth, but is also recycled nearly
perfectly. Also, nitrogen in the form of ammonia (NH 3)
may be obtainable from comets and the moons of outer planets. Nitrogen
may also be available in unknown quantities on certain other bodies in
the outer Solar System. The air of a habitat could be recycled in a number of ways. One concept is to use photosyntheticgardens, possibly via hydroponics, or forest gardening.
However, these do not remove certain industrial pollutants, such as
volatile oils, and excess simple molecular gases. The standard method
used on nuclear submarines, a similar form of closed environment, is to use a catalytic
burner, which effectively decomposes most organics. Further protection
might be provided by a small cryogenic distillation system which would
gradually remove impurities such as mercury vapor, and noble gases that cannot be catalytically burned.
Food production
Organic materials for food production would also need to be provided. At first, most of these would have to be imported from Earth. After that, feces recycling should reduce the need for imports.
One proposed recycling method would start by burning the cryogenic
distillate, plants, garbage and sewage with air in an electric arc, and
distilling the result.
The resulting carbon dioxide and water would be immediately usable in
agriculture. The nitrates and salts in the ash could be dissolved in
water and separated into pure minerals. Most of the nitrates, potassium
and sodium salts would recycle as fertilizers. Other minerals containing
iron, nickel, and silicon could be chemically purified in batches and
reused industrially. The small fraction of remaining materials, well
below 0.01% by weight, could be processed into pure elements with
zero-gravity mass spectrometry,
and added in appropriate amounts to the fertilizers and industrial
stocks. It is likely that methods would be greatly refined as people
began to actually live in space settlements.
Long-term on-orbit studies have proven that zero gravity weakens
bones and muscles, and upsets calcium metabolism and immune systems.
Most people have a continual stuffy nose or sinus problems, and a few
people have dramatic, incurable motion sickness. Most habitat designs
would rotate in order to use inertial forces to simulate gravity. NASA studies with chickens and plants have proven that this is an effective physiological substitute for gravity.
Turning one's head rapidly in such an environment causes a "tilt" to be
sensed as one's inner ears move at different rotational rates.
Centrifuge studies show that people get motion-sick in habitats with a
rotational radius of less than 100 metres, or with a rotation rate above
3 rotations per minute. However, the same studies and statistical
inference indicate that almost all people should be able to live
comfortably in habitats with a rotational radius larger than 500 meters
and below 1 RPM. Experienced persons were not merely more resistant to
motion sickness, but could also use the effect to determine "spinward"
and "antispinward" directions in the centrifuges.
Meteoroids and dust
The habitat would need to withstand potential impacts from space debris, meteoroids,
dust, etc. Most meteoroids that strike the earth vaporize in the
atmosphere. Without a thick protective atmosphere meteoroid strikes
would pose a much greater risk to a space settlement. Radar
will sweep the space around each habitat mapping the trajectory of
debris and other man-made objects and allowing corrective actions to be
taken to protect the habitat.
In some designs (O'Neill/NASA Ames "Stanford Torus" and "Crystal
palace in a Hatbox" habitat designs have a non-rotating cosmic ray
shield of packed sand (~1.9 m thick) or even artificial aggregate rock
(1.7 m ersatz concrete). Other proposals use the rock as structure and
integral shielding (O'Neill, "the High Frontier". Sheppard, "Concrete
Space Colonies"; Spaceflight, journal of the B.I.S.) In any of these
cases, strong meteoroid protection is implied by the external radiation
shell ~4.5 tonnes of rock material, per square meter.
Note that Solar Power Satellites are proposed in the multi-GW
ranges, and such energies and technologies would allow constant radar
mapping of nearby 3D space out-to arbitrarily far away, limited only by
effort expended to do so.
Proposals are available to move even kilometer-sized NEOs to high
Earth orbits, and reaction engines for such purposes would move a space
settlement and any arbitrarily large shield, but not in any timely or
rapid manner, the thrust being very low compared to the huge mass.
Heat rejection
The habitat is in a vacuum, and therefore resembles a giant thermos bottle. Habitats also need a radiator
to eliminate heat from absorbed sunlight. Very small habitats might
have a central vane that rotates with the habitat. In this design, convection
would raise hot air "up" (toward the center), and cool air would fall
down into the outer habitat. Some other designs would distribute
coolants, such as chilled water from a central radiator.
Attitude control
Most mirror geometries require something on the habitat to be aimed at the Sun and so attitude control is necessary. The original O'Neill design used the two cylinders as momentum wheels to roll the colony, and pushed the sunward pivots together or apart to use precession to change their angle.
A dumbbell-shaped self-sufficient and self-reproducible habitat for 10 personsVarious concepts merging into a cylindrical station
A dumbbell-like spacecraft or habitat, connected by a cable to a counterweight or other habitat. This design has been proposed as a Mars ship, initial construction shack for a space habitat, and orbital hotel.
It has a comfortably long and slow rotational radius for a relatively
small station mass. Also, if some of the equipment can form the
counter-weight, the equipment dedicated to artificial gravity is just a
cable, and thus has a much smaller mass-fraction than in other concepts.
For a long-term habitation, however, radiation shielding must rotate
with the habitat, and is extremely heavy, thus requiring a much stronger
and heavier cable. This speculative design was also considered by the NASA studies.
Small habitats would be mass-produced to standards that allow the
habitats to interconnect. A single habitat can operate alone as a bola.
However, further habitats can be attached, to grow into a "dumbbell"
then a "bow-tie", then a ring, then a cylinder of "beads", and finally a
framed array of cylinders. Each stage of growth shares more radiation
shielding and capital equipment, increasing redundancy and safety while
reducing the cost per person. This concept was originally proposed by a
professional architect because it can grow much like Earth-bound cities,
with incremental individual investments, unlike those that require
large start-up investments. The main disadvantage is that the smaller
versions use a large structure to support the radiation shielding, which
rotates with them. In large sizes, the shielding becomes economical,
because it grows roughly as the square of the colony radius. The number
of people, their habitats, and the radiators to cool them grow roughly
as the cube of the colony radius.
Further concepts
Interior of a Bernal sphere
Island One, a Bernal sphere settlement for about 10,000–20,000 people.
Lewis One,
a cylinder of radius 250 m with a non-rotating radiation shielding. The
shielding protects the micro-gravity industrial space, too. The
rotating part is 450m long and has several inner cylinders. Some of them
are used for agriculture.
Island Three, an even larger O'Neil cylinder design (3.2 km radius and 32 km long).
McKendree cylinder,
another concept that would use carbon nanotubes, a McKendree cylinder
is paired cylinders in the same vein as the Island Three concept, but
each 460 km in radius and 4600 km long (versus 3.2 km radius and 32 km
long in the Island Three).
Kalpana One, revised, a short cylinder with 250 m radius and 325 m length. The radiation shielding is 10 t/m2 and rotates. It has several inner cylinders for agriculture and recreation. It is sized for 3,000 residents.
Kalpana One concept
Bubbleworld or Inside/Outside concept, originated by Dandridge M. Cole in 1964, calls for drilling a tunnel through the longest axis of a large metallic asteroid and filling it with a volatile
substance, possibly water. A very large solar reflector would be
constructed nearby, focusing solar heat onto the asteroid, first to weld
and seal the tunnel ends, then more diffusely to slowly heat the entire
outer surface. As the metal softens, the water inside expands and
inflates the mass, while rotational forces help shape it into a
cylindrical form. Once expanded and allowed to cool, it can be spun to
produce centrifugal pseudogravity, and the interior filled with soil,
air and water. By creating a slight bulge in the middle of the cylinder,
a ring-shaped lake can be made to form. Reflectors would allow sunlight
to enter and to be directed where needed. This method would require a
significant human and industrial presence in space to be at all
feasible. The concept was popularized by science fiction author Larry Niven in his Known Space stories, describing such worlds as the primary habitats of the Belters, a civilization who had colonized the asteroid belt.
"Bubbleworld" is also the name of a different concept of space settlement thought of by Dani Eder in 1995 (it is alternatively known as an Ederworld).
This is a relatively thin, spherical shell surrounding a mass of gas
great enough to be held together by gravity. If hydrogen is used as the
gas, the shell would have a radius of about 240,000 km. The outside of
the shell would have a living space 2,400 km thick (filled with
breathable air) with an additional outer shell (possibly made of 500 m
of steel) above it to hold in the air.
Bishop Ring, a speculative design using carbon nanotubes:
a torus 1000 km in radius, 500 km in width, and with atmosphere
retention walls 200 km in height. The habitat would be large enough that
it could be "roofless", open to outer space on the inner rim.
Space
settlements are in principle space stations, developments in space
station construction therefore share many elements.
The following projects and proposals, while not truly space settlements,
incorporate aspects of what they would have and may represent stepping
stones towards eventually building of space settlements.
The Lunar Gateway is a planned lunar space station, the first outside of Low Earth Orbit, therefore being the first spacecraft designed in unshielded space.
The ISSCentrifuge Demo was proposed in 2011 as a demonstration project for an artificial gravity compartment, preparatory for a similar module of a Nautilus-X
Multi-Mission Space Exploration Vehicle (MMSEV). The ISS module would
have an outside diameter of 30 feet (9.1 m) with a 30 inches (760 mm)
ring interior cross-section diameter and would provide 0.08 to 0.51g
partial gravity. This test and evaluation centrifuge would have the
capability to become a Sleep Module for ISS crew. The subsequent vehicle
design would be a long-duration crewed space transport vehicle
including the artificial gravity compartment intended to promote
crew-health for a crew of up to six persons on missions of up to two
years duration. The partial-gtorus-ringcentrifuge would utilize both standard metal-frame and inflatable spacecraft structures and would provide 0.11 to 0.69g if built with the 40 feet (12 m) diameter option.
The Bigelow Commercial Space Station
was announced in mid-2010. Bigelow has publicly shown space station
design configurations with up to nine modules containing 100,000 cu ft
(2,800 m3) of habitable space. Bigelow began to publicly refer to the initial configuration as "Space Complex Alpha" in October 2010.
Space settlements have been elements of different science-fiction stories, across different media, from books to movies like Elysium (2013) for a wheel shaped Stanford torus type and Interstellar (2014) for a cylindrical O'Neill type.
The Space Frontier Foundation is an American space advocacynonprofitcorporation
organized to promote the interests of increased involvement of the
private sector, in collaboration with government, in the exploration and
development of space. Its advocate members design and lead a
collection of projects with goals that align to the organization's goals
as described by its credo.
The Space Frontier Foundation is an
organization of people dedicated to opening the Space Frontier to human
settlement as rapidly as possible.
Our goals include protecting the Earth’s fragile biosphere and
creating a freer and more prosperous life for each generation by using
the unlimited energy and material resources of space.
Our purpose is to unleash the power of free enterprise and lead a united humanity permanently into the Solar System.
History
The foundation was founded in 1988 by space activists led by Rick Tumlinson,
Bob Werb and Jim Muncy who felt that:
"it was technically possible to realize their shared vision of
large-scale...settlement of the inner solar system... [but] they knew
this was not happening (and couldn't happen) under the status-quo
centrally planned and exclusive U.S. government space program."
Since 2005 the foundation has relied heavily on NASA funding,
including a recent $110,000 award for business competition. Thomas Olson
appeared on The Space Show to promote the competition. The competition
takes place during the foundation's New-Space 12 conference, which is
sponsored by NASA.
The foundation supported the George W. Bush Administration's Vision for Space Exploration.
In March, 2005, the foundation praised the selection of Dr. Michael
Griffin as the next administrator of NASA. A press release said "Mike
Griffin will be a good captain for NASA." Bob Werb, the foundation
chairman, said "Mike Griffin knows more about space and capitalism than
the last three administrators combined. Vision-killing bureaucrats
inside and outside of government should be trembling in their boots."
Richard Tumlinson said, "This bodes well for the emerging New Space
industry."
Activities and policies
In recent years, the Space Frontier Foundation has been supportive of various private sector efforts such as the Ansari X Prize, the SpaceShipOne project, and entrepreneur Robert Bigelow's plans to build a space hotel. The foundation has been critical of the U.S. government's efforts in space, particularly those of the National Aeronautics and Space Administration. For example, the foundation has criticized NASA's Space Shuttle and Ares I,
claiming that the shuttle's work could be better done by private sector
companies. However, the foundation has supported some recent NASA
efforts, such as NASA's Centennial Challenges
prize program for stimulating private-sector innovation and the new
NASA direction of cancelling Constellation in favour of technology
development and supporting commercial companies.
The foundation's current strategic focus is to enable the growth of the NewSpace community. The foundation's board of directors has endorsed the following objectives:
The Space Frontier Foundation's mission is to open the space frontier to permanent human settlement;
An open frontier can only be achieved by unleashing the power of free enterprise;
Government's role in unleashing the power of free enterprise is
critical and best accomplished by adopting the proven frontier paradigm
of catalyzing the private sector;
All parts of all governments must embrace and fully utilize the potential of the emerging NewSpace Industry, and;
Regarding NASA, the near-term focus of the foundation is on
maximizing the market share of goods and services that the NewSpace
industry is permitted to capture.
The
foundation's membership is composed of volunteers who typically fall
into one of two groups. The regular members are those who provide a
large amount of the volunteer work necessary to operate the projects
that support the conferences and many other less obvious processes
associated with a corporate office. Regular members donate time and
money as they can in accordance with other demands upon them. Advocate
members are those who are invited to step to the next level and help run
the projects, start new ones, and fund the foundation's activities.
Advocates are those who have demonstrated a high degree of understanding
and commitment to the foundation's goals along with a track record of
action toward these goals. Advocates are asked to donate more time and
money on a regular basis and are the voting members that decide
elections for the foundation's board of directors.
Projects
are the primary means by which the foundation acts in support of its
goals. Projects are advocate managed activities with their own
objectives, budgets, and volunteer support teams. Each project pursues
what its members think they can accomplish using the skills they have.
Advocates working each project assume the responsibility for keeping
them aligned with Foundation objectives as best they can. This mostly
decentralized approach to action is intentional and a core tradition of
the foundation.
Past projects include The Watch, an asteroid and comet detection and research project, Permission to Dream, connecting students around the world through the wonder of space and astronomy,
sponsorship of conferences, and the Space Settlement Project in
marketing space to the general public. Current projects include
Teachers in Space, a program to offer American teachers rides on future sub-orbital spaceflight launches.
Furthermore, the foundation hosts its annual NewSpace conference every year in July, which enables NewSpace leaders to meet and collaborate regarding the future of the movement.
Artificial gene drive using a CRISPR-Cas9
system: gRNA instructs Cas9 to cut at the rival allele, causing the
repair mechanism to replace the damage with the Cas9-containing allele
A gene drive is a natural process and technology of genetic engineering that propagates a particular suite of genes throughout a population by altering the probability that a specific allele will be transmitted to offspring (instead of the Mendelian 50% probability). Gene drives can arise through a variety of mechanisms. They have been proposed to provide an effective means of genetically modifying specific populations and entire species.
The technique can employ adding, deleting, disrupting, or modifying genes.
As with any potentially powerful technique, gene drives can be misused in a variety of ways or induce unintended consequences.
For example, a gene drive intended to affect only a local population
might spread across an entire species. Gene drives that eradicate
populations of invasive species in their non-native habitats may have
consequences for the population of the species as a whole, even in its
native habitat. Any accidental return of individuals of the species to
its original habitats, through natural migration, environmental
disruption (storms, floods, etc.), accidental human transportation, or
purposeful relocation, could unintentionally drive the species to
extinction if the relocated individuals carried harmful gene drives.
Gene drives can be built from many naturally occurring selfish genetic elements that use a variety of molecular mechanisms. These naturally occurring mechanisms induce similar segregation distortion in the wild, arising when alleles evolve molecular mechanisms that give them a transmission chance greater than the normal 50%.
Most gene drives have been developed in insects, notably
mosquitoes, as a way to control insect-borne pathogens. Recent
developments designed gene drives directly in viruses, notably herpesviruses.
These viral gene drives can propagate a modification into the
population of viruses, and aim to reduce the infectivity of the virus.
Mechanism
In sexually-reproducing species, most genes are present in two copies (which can be the same or different alleles),
either one of which has a 50% chance of passing to a descendant. By
biasing the inheritance of particular altered genes, synthetic gene
drives could more effectively spread alterations through a population.
Typically, scientists insert the gene drive into an organism's
DNA along with the CRISPR-Cas9 machinery. When the modified organism
mates and its DNA mixes with that of its mate, the CRISPR-Cas9 tool cuts
the partner's DNA at the same spot where the gene drive is located in
the first organism. The cell repairs the cut DNA by copying the gene
drive from the first organism into the corresponding spot in the DNA of
the offspring. This means both copies of the gene (one from each parent)
now contain the gene drive.
Molecular mechanisms
Molecular mechanism of a gene drive based on Cas9 and guide RNA.
At the molecular level, an endonuclease gene drive works by cutting a chromosome at a specific site that does not encode the drive, inducing the cell to repair the damage
by copying the drive sequence onto the damaged chromosome. The cell
then has two copies of the drive sequence. The method derives from genome editing techniques and relies on homologous recombination. To achieve this behavior, endonuclease gene drives consist of two nested elements:
An endonuclease that selectively cuts at the "target sequence", i.e. the rival allele. This can be one of:
A homing endonuclease, which is what natural inteins use to propagate. They are, however, very difficult, if not impossible, to retarget.
An RNA-guided endonuclease (e.g., Cas9 or Cas12a) and its guide RNA, which can be easily altered to set the target. Cas9 is the most promising technology identified in a 2014 review. Cas9 gene drives have been successfully tested in 2015, and Cas12a in 2023.
Any other programmable endonuclease system, such as modular zinc finger nucleases and TALEN.
One such drive has been successfully tested in fruit flies, but it
turned out to be evolutionarily unstable due to the many-repeat nature
of those endonucleases.
A template sequence used by the DNA repair machinery after
the target sequence is cut. To achieve the self-propagating nature of
gene drives, this repair template contains at least the endonuclease
sequence. Because the template must be used to repair a double-strand break at the cutting site, its sides are homologous
to the sequences that are adjacent to the cutting site in the host
genome. By targeting the gene drive to a gene coding sequence, this gene
will be inactivated; additional sequences can be introduced in the gene
drive to encode new functions.
As a result, the gene drive insertion in the genome will re-occur in
each organism that inherits one copy of the modification and one copy of
the wild-type gene. If the gene drive is already present in the egg
cell (e.g. when received from one parent), all the gametes of the
individual will carry the gene drive (instead of 50% in the case of a
normal gene).
Spreading in the population
Since it can never more than double in frequency with each
generation, a gene drive introduced in a single individual typically
requires dozens of generations to affect a substantial fraction of a
population. Alternatively, releasing drive-containing organisms in
sufficient numbers can affect the rest within a few generations; for
instance, by introducing it in every thousandth individual, it takes
only 12–15 generations to be present in all individuals.
Whether a gene drive will ultimately become fixed in a population and
at which speed depends on its effect on individual fitness, on the rate
of allele conversion, and on the population structure. In a well mixed
population and with realistic allele conversion frequencies (≈90%),
population genetics predicts that gene drives get fixed for a selection
coefficient smaller than 0.3;
in other words, gene drives can be used to spread modifications as long
as reproductive success is not reduced by more than 30%. This is in
contrast with normal genes, which can only spread across large
populations if they increase fitness.
Gene drive in viruses
Because the strategy usually relies on the simultaneous presence of an unmodified and a gene drive allele in the same cell nucleus, it had generally been assumed that a gene drive could only be engineered in sexually reproducing organisms, excluding bacteria and viruses. However, during a viral infection,
viruses can accumulate hundreds or thousands of genome copies in
infected cells. Cells are frequently co-infected by multiple virions and
recombination between viral genomes is a well-known and widespread source of diversity for many viruses. In particular, herpesviruses are nuclear-replicating DNA viruses with large double-stranded DNA genomes and frequently undergo homologous recombination during their replication cycle.
These properties have enabled the design of a gene drive strategy that doesn't involve sexual reproduction, instead relying on co-infection
of a given cell by a naturally occurring and an engineered virus. Upon
co-infection, the unmodified genome is cut and repaired by homologous
recombination, producing new gene drive viruses that can progressively
replace the naturally occurring population. In cell culture
experiments, it was shown that a viral gene drive can spread into the
viral population and strongly reduce the infectivity of the virus, which
opens novel therapeutic strategies against herpesviruses.
Technical limitations
Because
gene drives propagate by replacing other alleles that contain a cutting
site and the corresponding homologies, their application has been
mostly limited to sexually reproducing species (because they are diploid or polyploid
and alleles are mixed at each generation). As a side effect, inbreeding
could in principle be an escape mechanism, but the extent to which this
can happen in practice is difficult to evaluate.
Due to the number of generations required for a gene drive to
affect an entire population, the time to universality varies according
to the reproductive cycle of each species: it may require under a year
for some invertebrates, but centuries for organisms with years-long
intervals between birth and sexual maturity, such as humans. Hence this technology is of most use in fast-reproducing species.
Effectiveness in real practice varies between techniques, especially by choice of germline promoter. Lin and Potter 2016 (a) discloses the promoter technology homology assisted CRISPR knockin (HACK) and Lin and Potter 2016 (b) demonstrates actual use, achieving a high proportion of altered progeny from each altered Drosophila mother.
Issues
Issues highlighted by researchers include:
Mutations: A mutation could happen mid-drive, which has the potential to allow unwanted traits to "ride along".
Escape: Cross-breeding or gene flow potentially allow a drive to move beyond its target population.
Ecological impacts: Even when new traits' direct impact on a target
is understood, the drive may have side effects on the surroundings.
The Broad Institute of MIT and Harvard added gene drives to a list of uses of gene-editing technology it doesn't think companies should pursue.
Bioethics concerns
Gene
drives affect all future generations and represent the possibility of a
larger change in a living species than has been possible before.
In December 2015, scientists of major world academies called for a moratorium on inheritable human genome edits that would affect the germline, including those related to CRISPR-Cas9 technologies, but supported continued basic research and gene editing that would not affect future generations. In February 2016, British scientists were given permission by regulators to genetically modify human embryos by using CRISPR-Cas9 and related techniques on condition that the embryos were destroyed in seven days. In June 2016, the US National Academies of Sciences, Engineering, and Medicine released a report on their "Recommendations for Responsible Conduct" of gene drives.
A 2018 mathematical modelling studies suggest that despite
preexisting and evolving gene drive resistance (caused by mutations at
the cutting site), even an inefficient CRISPR "alteration-type" gene
drive can achieve fixation
in small populations. With a small but non-zero amount of gene flow
among many local populations, the gene drive can escape and convert
outside populations as well.
Kevin M. Esvelt
stated that an open conversation was needed around the safety of gene
drives: "In our view, it is wise to assume that invasive and
self-propagating gene drive systems are likely to spread to every
population of the target species throughout the world. Accordingly, they
should only be built to combat true plagues such as malaria, for which
we have few adequate countermeasures and that offer a realistic path
towards an international agreement to deploy among all affected
nations.". He moved to an open model for his own research on using gene drives to eradicate Lyme disease in Nantucket and Martha's Vineyard.
Esvelt and colleagues suggested that CRISPR could be used to save
endangered wildlife from extinction. Esvelt later retracted his support
for the idea, except for extremely hazardous populations such as
malaria-carrying mosquitoes, and isolated islands that would prevent the
drive from spreading beyond the target area.
Researchers had already shown that such genes could act selfishly
to spread rapidly over successive generations. Burt suggested that gene
drives might be used to prevent a mosquito population from transmitting
the malaria parasite or to crash a mosquito population. Gene drives based on homing endonucleases have been demonstrated in the laboratory in transgenic populations of mosquitoes and fruit flies.
However, homing endonucleases are sequence-specific. Altering their
specificity to target other sequences of interest remains a major
challenge.
The possible applications of gene drive remained limited until the
discovery of CRISPR and associated RNA-guided endonucleases such as Cas9 and Cas12a.
Target Malaria, a project funded by the Bill and Melinda Gates Foundation,
invested $75 million in gene drive technology. The foundation
originally estimated the technology to be ready for field use by 2029
somewhere in Africa. However, in 2016 Gates changed this estimate to
some time within the following two years. In December 2017, documents released under the Freedom of Information Act showed that DARPA had invested $100 million in gene drive research.
Scientists have designed multiple strategies to maintain control over gene drives.
In 2020, researchers reported the development of two active guide RNA-only
elements that, according to their study, may enable halting or deleting
gene drives introduced into populations in the wild with CRISPR-Cas9 gene editing.
The paper's senior author cautions that the two neutralizing systems
they demonstrated in cage trials "should not be used with a false sense of security for field-implemented gene drives".
If elimination is not necessary, it may be desirable to
intentionally preserve the target population at a lower level by using a
less severe gene drive technology. This works by maintaining the
semi-defective population indefinitely in the target area, thereby
crowding out potential nearby, wild populations that would otherwise
move back in to fill a void.
CRISPR
CRISPR is the leading genetic engineering method. In 2014, Esvelt and coworkers first suggested that CRISPR/Cas9 might be used to build gene drives. In 2015, researchers reported successful engineering of CRISPR-based gene drives in Saccharomyces,Drosophila, and mosquitoes.
They reported efficient inheritance distortion over successive
generations, with one study demonstrating the spread of a gene into
laboratory populations.
Drive-resistant alleles were expected to arise for each of the
described gene drives; however, this could be delayed or prevented by
targeting highly conserved sites at which resistance was expected to
have a severe fitness cost.
Because of CRISPR's targeting flexibility, gene drives could
theoretically be used to engineer almost any trait. Unlike previous
approaches, they could be tailored to block the evolution of drive
resistance by targeting multiple sequences. CRISPR could also enable
gene drive architectures that control rather than eliminate populations.
In 2022, t-CRISPR, was used to pass the “t haplotype” gene to
about 95% of offspring. The approach spreads faulty copies of a female
fertility gene to offspring, rendering them infertile. The researchers
reported that their models suggested that adding 256 altered animals to
an island with a population of 200,000 mice would eliminate the
population in about 25 years. The traditional approaches of poison and
traps were not needed.
Applications
Gene drives have two main classes of application, which have implications of different significance:
introduce a genetic modification in laboratory populations; once
a strain or a line carrying the gene drive has been produced, the drive
can be passed to any other line by mating. Here, the gene drive is used
to much more easily achieve a task that could be accomplished with
other techniques.
introduce a genetic modification in wild populations. Gene drives
constitute a major development that makes possible previously
unattainable changes.
Because of their unprecedented potential risk, safeguard mechanisms have been proposed and tested.
Disease vector species
One possible application is to genetically modify mosquitoes, mice, and other disease vectors so that they cannot transmit diseases, such as malaria and dengue fever in the case of mosquitoes, and tick-borne disease in the case of mice.
Researchers have claimed that by applying the technique to 1% of the
wild population of mosquitoes, that they could eradicate malaria within a
year.
Invasive species control
A gene drive could be used to eliminate invasive species and has, for example, been proposed as a way to eliminate invasive species in New Zealand.
Gene drives for biodiversity conservation purposes are being explored
as part of The Genetic Biocontrol of Invasive Rodents (GBIRd) program
because they offer the potential for reduced risk to non-target species
and reduced costs when compared to traditional invasive species removal
techniques. Given the risks of such an approach described below, the
GBIRd partnership is committed to a deliberate, step-wise process that
will only proceed with public alignment, as recommended by the world's
leading gene drive researchers from the Australian and US National
Academy of
Sciences and many others.
A wider outreach network for gene drive research exists to raise
awareness of the value of gene drive research for the public good.
Some scientists are concerned about the technique, fearing it could spread and wipe out species in native habitats. The gene could mutate, potentially causing unforeseen problems (as could any gene).
Many non-native species can hybridize with native species, such that a
gene drive afflicting a non-native plant or animal that hybridizes with a
native species could doom the native species. Many non-native species
have naturalized into their new environment so well that crops and/or
native species have adapted to depend on them.
The Predator Free 2050 project is a New Zealand government program to
eliminate eight invasive mammalian predator species (including rats,
short-tailed weasels, and possums) from the country by 2050. The project was first announced in 2016 by New Zealand's prime minister John Key and in January 2017 it was announced that gene drives would be considered in the effort, but this has not yet been actualised.
In 2017, one group in Australia and another in Texas released
preliminary research into creating 'daughterless mice' using gene drives
in mammals.
California
In 2017, scientists at the University of California, Riverside developed a gene drive to attack the invasivespotted-wing drosophila,
a type of fruit fly native to Asia that is costing California's cherry
farms $700 million per year because of its tail's razor-edged ovipositor that destroys unblemished fruit. The primary alternative control strategy involves the use of insecticides called pyrethroids that kill almost all insects that it contacts.
Wild animal welfare
The transhumanist philosopher David Pearce has advocated for using CRISPR-based gene drives to reduce the suffering of wild animals. Kevin M. Esvelt,
an American biologist who has helped develop gene drive technology, has
argued that there is a moral case for the elimination of the New World screwworm through such technologies because of the immense suffering that infested wild animals experience when they are eaten alive.
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