Re: Manned interplanetary travel is IMPOSSIBLE today, but PROBABLE soon.

H2-PV NOW a écrit :
jacob navia wrote:

There is a widespread misconception that with today's technologies
it would be possible to send people to Mars.

That is not possible. There are TWO major show stoppers.

Problem (1)

"Man" as we know it now, is not able to survive in space for
more than 6 months without damage, and after more than 1.5 years
the damage is so great as to be equivalent to a death sentence.

The longest stay of a man in space runs up to 400 days.


Since we have no data longer than one case of 400 days, we cannot know
what a terminal length duration is. Did the person die on the 400th
day, or did they live?

He was VERY sick for months and months, and the russians considered
sending him into space again. No he did not die. And I said 1.5 years,
what makes 547.5 days... After 400 days (approximately you are just
VERY sick)

I have heard of no deaths on space stations
whatsoever. The soviets, with their disregard for personal lives and
comforts, paid for the endurance records by keeping the atmospheric
pressure low, which would surely impact overall health and fitness over
time. Perhaps a two-atmospheres pressure is all it takes to stay fit
indefinitely? Nobody will know until habitats can be launched in
sufficiency to try the experiments. Nothing definite can be known yet.

NASA doesn't want to send people longer than 6 months because of this
problem. They try to play it safe.



This is due to muscle degeneration due to lack of gravity. This
is a SHOW STOPPER for any manned missions beyond the moon.

Spaceships for interplanetary travel must have artificial gravity
(spin) so they need to be much bigger than they are now.

Note that this problem does NOT go away with exercise machines.


Spaceships for Interplanetary travel need to be luxury liners, not tin
cans with all the amenities of a 3rd world jail cell, like
over-crowding and lack of bathing.

How much gravity is needed has yet to be determined.


In any case artificial gravity is a must. That makes them
much heavier than any existing vehicle, or any vehicle in
a few decades.




Problem (2)

Space is full with Gamma rays and cosmic rays. For any mission longer
than a few weeks you need shielding with at least several meters of
water. Without this, "Man" dies from cancer and DNA destruction.


This is a conjecture based on nothing meaningful.

----------------------------------------------------------------------
Please read Scientific American There is an interesting article there:
ASTRONAUTICS
Shielding Space Travelers
The perils of cosmic rays pose severe, perhaps insurmountable, hurdles to human spaceflight to Mars and beyond
By Eugene N. Parker
Mars 2006
----------------------------------------------------------------------
Radiation Research: Vol. 156, No. 5, pp. 682–688.

Space Radiation Cancer Risks and Uncertainties for Mars Missions
Francis A. Cucinotta,a, b Walter Schimmerling,c John W. Wilson,d Leif E. Peterson,e Gautam D. Badhwar,a Premkumar B. Saganti,a and John F. Dicellof

aNASA Johnson Space Center, Houston, Texas 77058

ABSTRACT

Cucinotta, F. A., Schimmerling, W., Wilson, J. W., Peterson, L. E., Badhwar, G. D., Saganti, P. B. and Dicello, J. F. Space Radiation Cancer Risks and Uncertainties for Mars Missions. Radiat. Res. 156, 682–688 (2001).

Projecting cancer risks from exposure to space radiation is highly uncertain because of the absence of data for humans and because of the limited radiobiology data available for estimating late effects from the high-energy and charge (HZE) ions present in the galactic cosmic rays (GCR). Cancer risk projections involve many biological and physical factors, each of which has a differential range of uncertainty due to the lack of data and knowledge. We discuss an uncertainty assessment within the linear-additivity model using the approach of Monte Carlo sampling from subjective error distributions that represent the lack of knowledge in each factor to quantify the overall uncertainty in risk projections. Calculations are performed using the space radiation environment and transport codes for several Mars mission scenarios. This approach leads to estimates of the uncertainties in cancer risk projections of 400–600% for a Mars mission. The uncertainties in the quality factors are dominant.
---->>>>-----
Using safety standards developed for low-Earth orbit, long-term space missions (>90 days) outside the Earth's magnetic field are currently unacceptable if the confidence levels in risk projections are considered.
----->>>>------
Because GCR exposures involve multiple particle or δ-ray tracks per cellular array, our results suggest that the shape of the dose response at low dose rates may be an additional uncertainty for estimating space radiation risks.



Earth lifeforms do not have the equivilent of several meters of water
between them and the nasty radiation. Don't be fooled by tall columns
of air. The real determination of atoms between you and all hell
breaking loose out there is 14.7 pounds of pressure per inch square,
which in metric units is 1 kilogram per cm^2. Water has a density of 1
gram per cm^3 and 1000 of those is 1 kilogram of water. So ONE exactly
kilogram of water offers all the same mass as 75 miles tall column of
air.


Nonsense. Please read the article.

It doesn't take "several meters of water", but exactly one. You could
have done this exercise yourself if you wanted to but you preferred to
buttress your opinion with gross exaggeration. That doesn't say good
things about your trustworthness as a source of information.


A cubic meter of water is 1 ton. Multiply by the surface of the
spacecraft.



This means that spaceships must carry thick shielding, what makes them
even heavier. The crew must live behind several meters of water to
survive in space.


You repeat your gross exaggeration again. Doesn't it bother you to be
wrong in public enough to check your facts first before publishing
something?


????



With time, that water becomes radioactive and must
be changed. This will not happen in short trips (Mars/Venus) but in
longer expeditions that would take several years (Uranus/Neptune).


You mind giving your source for this data. Exactly what becomes
radioactive? Is it the Hydrogen? Does it transmute to tritium? Is it
the Oxygen?

http://en.wikipedia.org/wiki/Tritium
"Tritium is radioactive with a half-life of 12.32 years. It decays into
helium-3 ... releasing 18.6 keV of energy. The electron has an average
kinetic energy of 6.5 keV, while the remaining energy is carried off
undetectably by the electron antineutrino. The low-energy beta
radiation from tritium cannot penetrate human skin, so tritium is only
dangerous if inhaled or ingested."

Hmmm, you planning to inhale the shielding or ingest it?


Probably water could be used to drink it isn't it?

http://en.wikipedia.org/wiki/Oxygen
"Oxygen has fifteen known isotopes with atomic masses ranging from 12
to 26. Three of them are stable and twelve are radioactive. The
radioisotopes all have half lives of less than three minutes."

Radioactive for three minutes. Well that scares me. NOT!


Note too that Mars does not offer any protection against radiation
since its magnetic field is VERY weak or non-existent. After eons of
being hit by cosmic rays, the surface of Mars is quite radioactive.


I was able to find no immediate sources to support a statement that
Mars is "quite radioactive"


Secondary radiation. The radioactivity from the cosmic rays knocks
atoms in the surface making them radioactive.

http://science.nasa.gov/headlines/y2005/08sep_radioactivemoon.htm?list197914

NASA claims on the subject that they will BEGIN to study radiation on
the moon in 2008. It seems you are getting your information from a
psychic friend hotline at $2.95 per minute.

http://lsda.jsc.nasa.gov/books/apollo/S2ch3.htm
"Radiation doses measured during Apollo were significantly lower than
the yearly average of 5 rem[*] set by the U.S. Atomic Energy Commission
for workers who use radioactive materials in factories and institutions
across the United States. Thus, radiation was not an operational
problem during the Apollo Program. Doses received by the crewmen of
Apollo missions 7 through 17 were small because no major solar-particle
events occurred during those missions. One small event was detected by
a radiation sensor outside the Apollo 12 spacecraft, but no increase in
radiation dose to the crewmen inside the spacecraft was detected."


Of course. In a few days exposures you do not risk anything serious.
Another thing is staying in space for more than 2 years.

It would re-radiate into any not-shielded vessel. Astronauts would
be forced underground. Gravity in mars is only 1/3 of earth's. Not
enough to avoid muscle decay. It would be necessary to have a
rotating base.


There is not enough data to know what partial gravity is sufficient for
perpetual muscle tone. We have data from a few short landings on the
moon and from zero gravity space stations. Where are you getting your
information?


So, you do not know but you want to send people there?

Conclusion:

We need to build spaceships of enormous size to get to the planets.
That technology will be ready maybe 2040-2050. Not now.


What's this "WE"?

Humans.

.

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