Why should we engage in manned space flight?

Motivated by a question by Jenny Smith's brother Joey, I started to write some ideas about this question. This is a first attempt at an essay.

To echo the words of NASA administrator Sean O'Keefe, the space agency
needs "not an either/or but a combination" of unmanned and manned flights. President Bush's new budget for NASA gives about $5.6 billion to space and Earth science (unmanned missions) and human space flight -- meaning the International Space Station and the shuttles -- gets $6.2 billion.

Unmanned missions have one crucial advantage over human space flights, one this is ever in our mind after the Columbia tragedy of two months ago:
Failures are embarrassing but not fatal. Furthermore, robots don't need
astronomically expensive safety systems, so the dollar loss is less when a spacecraft goes awry.

Some unmanned missions are important for purely scientific reasons, like
the Hubble observatory. But others are seen as 'scouts,' which are paving
the way for future human explorers. Several missions to the Moon, Mars,
or more exotic places like asteroids and Jupiter's moon Europa, have as
part of their plan a determination of places which would be best suitable
for human presence.

But let's get to the crux of your question: 'Why should we
even engage in manned space flight?'

Motivation. Like it or not, we live in a world where people are
motivated by manned space flight. It's part of our desire to explore and
adapt to exotic places where we (biologically) "don't belong". If we
remove this motivation, less will be accomplished because people will be
less motivated. It is difficult to measure the dollar-worth of motivation,
but it is significant. Without manned space flight as a goal, I would
expect NASA's budget to be cut by a large fraction.

Research. Unmanned space probes still have limitations. Humans can
conduct valuable field studies far better than any probes. Manned space
travel has offered a wealth of biological and medical information that can
directly help humans on Earth. Although unmanned probes and satellites
are very useful to space exploration, manned space missions are essential
to developing a thorough understanding of a particular region or planet.

Field Studies.Astronauts are able to conduct field studies, which
require observation in the field, the creation of a conceptual model, and
the formulation and testing of hypotheses. Field study is not a simple
matter of collecting data: it requires the guiding presence of human
intelligence. Human intelligence is needed throughout a field study, as
the requirements might call upon humans to change their course to fit
their needs. For example the Mars Pathfinder discovered an unusual,
silica-rich type of rock, but because of the probe's limitations, NASA
could not determine whether this composition represents an igneous rock,
an impact breccia or a sedimentary rock. Another example was the USSR's
unmanned Luna missions, which brought back moon rocks during the 1970s.
Although the Luna missions were much cheaper than the Apollo missions, the
results were virtually incomprehensible because the Luna robots picked up
rocks indiscriminately; the Apollo missions had the knowledge and insight
of the geologically trained astronauts to decide which rocks were of
scientific interest and which rocks were not. Fields studies, which
require human presence, can be of great value to the scientific community.

Medicinal Research.Another benefit of manned space travel is the
medicinal research that can be conducted. Manned space exploration offers
valuable research into many medical fields, such as bone loss,
cardiovascular alterations, sleep and human performance, and muscular
atrophy. Outer space is a distinctly different environment compared to
anywhere on Earth, and the effects of microgravity and days that last an
hour and a half give researchers many opportunities to study how the human
functions under these conditions. The research that is performed in outer
space helps people on Earth with many different medical conditions,
including osteoporosis, heart disease, sleep disorders, muscular atrophy,
and numerous other related illnesses. Manned space exploration offers many
benefits to the people of Earth through scientific research in medicine.

Applications. If manned space flight can be made routine, cheap, and
easy, suborbital flights might become routine cheap and easy. How much
would you pay for a ticket to Australia on a one hour flight? There is
almost certainly a large market for suborbital flights, if we can make the
cost and danger sufficiently minimal. Organizations such as the X-Prize
Foundation have been actively promoting the development of manned space
vehicles by private industry to be operated on a commercial basis. The
X-Prize challenge is to construct a vehicle capable of sub-orbital flight
with three passengers, with the constraint of only allowing 10% of the
vehicle dry mass to be expendable, and a turn around of 14 days to
re-launch. There is also the possibility of more space tourism. We've
already seen two examples of multi-millionaires paying about $20 million
for a visit to space about the ISS. In a recent survey, about 30% of
Americans, Japanese, and Europeans said that they would be willing to
spend a quarter of a year's salary for a trip into space. So if the price
for a ticket to spae could be lowered, this market could have tremendous
potential. (see spacetoday.net/tourism)

War. We have never had war in space, but if war comes, any space-faring nation or coalition of nations will desire the upper hand. One important question is: are humans helpful
to war in space? The answer at the moment is possibly yes. Currently
computers have a very limited ability to plan and cope with unforeseen
events. They will cease functioning if they fall out of communication and
they are possibly even prone to subversion. Humans are much more adept at
coping with unforeseen and inimical conditions. (see spacewar.com)

Capability. There is some difficulty in assessing the value inherent
in having a capability. The cability to send men into space is inherently
valuable, just like any other capability. Some unforeseen problem might
arise requiring men in space. While this value is difficult to assess, it
should not be ignored.

Manned space travel has evolved considerably since Yuri Gagarin became the
first man in space on 12 April 1961. In the past forty years, there were
manned missions to orbit, to space stations, behind the moon, and even to
the moon's surface. Manned space travel offers the opportunities for
scientists to conduct valuable field studies, as well as helping medical
professionals better understand the human body. Unmanned probes and space
satellites can still be used for many functions such as preliminary
reconnaissance missions to collect general data on a planet or region of
space, but they cannot replace live humans who can use intelligence to
conduct much more detailed and ambitious studies. It would be foolish to
discount the uses of both unmanned space probes and manned space missions
entirely. It is important for the scientists at NASA to consider the
advantages and disadvantages of both manned and unmanned space missions to
accomplish their desired goals.