AW: [ RadSafe ] [RadSafe]Mission to Mars---Fission Propulsion
Rainer.Facius at dlr.de
Rainer.Facius at dlr.de
Wed Oct 1 05:53:21 CDT 2008
Dear Franz,
regarding the Luna versus Mars option I consider it axiomatic that prior to a mission to Mars the moon (in addition to the ISS) will be utilized as a testbed where all the technology advances will have to be tested exhaustively which yet have to be realized for a long-term mission through interplanetary space. Monitoring and management of radiation exposure is just one though important part of these tasks. In addressing Mike's comment, I would add that also numerous robotic missions will be part of the preparation for man's habitation on Mars' surface.
OFF TOPIC now:
Regarding the Terra versus Mars option I do sympathize with your reservations. Yet, I hold that they are founded upon an unrealistic conception of the forces driving human behaviour.
Whereas "ratio" admittedly is an important part of our setup, my impression is that we utilize it predominantly to pursue our own personal (petty) goals. Collectively, our behaviour appears to be exceedingly susceptible to the irrational visions, which enables capable demagogues of any colouration to summon large enough followings to pursue their own personal petty (and often dreadful) goals. Paradoxically, human history is particularly rich in pertinent examples subsequent to the "great enlightenment" which proclaimed the enthronement of "Ratio". Nationalism, Racism/Nazism, Communism furnish only 'crowning' examples of the mental diseases which affected mankind succeeding this area of would-be 'emancipation'.
In apologizing for this off-topic diversion I would repeat my prognosis that eventually manned missions to Mars will come about and hence it makes sense to be well prepared.
Best regards, Rainer
PS: I am pleased to note that you are very well able to argue "sine ira et studio".
(no harm intended :-)
________________________________
Von: Franz Schönhofer [mailto:franz.schoenhofer at chello.at]
Gesendet: Di 30.09.2008 23:03
An: 'Jerry Lahti'; Facius, Rainer; radsafe at radlab.nl
Betreff: AW: [ RadSafe ] [RadSafe]Mission to Mars---Fission Propulsion
Dear Jerry, dear Rainer, dear et al. of this thread,
Thank you for your contributions, they really are extremely interesting and
show a lot of knowledge in this field. I really appreciated them!
But may I ask a provocating and probably "nasty" question: Why should
mankind fly to Mars and why should we establish a station there? As far as I
understand there are hardly any concrete plans yet for a manned moon
station. The moon is much closer and the radiation protection considerations
are much less negative.
It seems that there are enough problems on our "Mother Earth", which should
be solved before flying to Mars....
Sine ira et studio,
Best regards,
Franz
Franz Schoenhofer, PhD
MinRat i.R.
Habicherg. 31/7
A-1160 Wien/Vienna
AUSTRIA
-----Ursprüngliche Nachricht-----
Von: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] Im Auftrag
von Jerry Lahti
Gesendet: Dienstag, 30. September 2008 22:00
An: Rainer.Facius at dlr.de; radsafe at radlab.nl
Betreff: Re: [ RadSafe ] [RadSafe]Mission to Mars---Fission Propulsion
As I recall, the principal doses were delivered by cascaded nuclei from high
energy proton bombardmant. The first several g/cm**2 acted as a dose
AMPLIFIER rather than shielding.
--
Jerry Lahti
Naperville IL
---------- Original Message -----------
From: <Rainer.Facius at dlr.de>
To: <radsafe at radlab.nl>
Sent: Tue, 30 Sep 2008 19:02:40 +0200
Subject: [ RadSafe ] [RadSafe]Mission to Mars---Fission Propulsion
> Mike,
>
> to my knowledge Bremsstrahlung intensities from charged particles
> other than electrons are negligible. Hence only during passages
> through the (mainly outer) radiation belts, Bremsstrahlung photons
> contribute to space radiation doses. While operating, nuclear
> propulsion engines of course are intense sources of gamma rays and
> neutrons. After engine shutdown, decay of fission products by
> predominantly beta decay will be the source for rather soft and
> hence negligible Bremsstrahlung photons. Fission product decay
> ceases quite rapidly.
>
> So, for all space flight mission scenarios other than geostationary
> orbits (and of course in the vicinity of Jupiter :-), Bremsstrahlung
> contributes only negligibly to space radiation exposures.
>
> Regards, Rainer
>
> Dr. Rainer Facius
> German Aerospace Center
> Institute of Aerospace Medicine
> Linder Hoehe
> 51147 Koeln
> GERMANY
> Voice: +49 2203 601 3147 or 3150
> FAX: +49 2203 61970
>
> -----Ursprüngliche Nachricht-----
> Von: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] Im
> Auftrag von Brennan, Mike (DOH) Gesendet: Dienstag, 30. September
> 2008 18:05 An: radsafe at radlab.nl Betreff: RE: [ RadSafe ]
> [RadSafe]Mission to Mars---Fission Propulsion
>
> I suspect that the key to using nuclear propulsion in space is
> getting in and out of our gravity well. Most of the schemes for
> using reactors to accelerate reaction mass can not achieve the
> acceleration needed to go from Earth's surface to orbit. Even if a
> nuclear rocket could develop that kind of acceleration, I foresee
> non-trivial political obstacles to such a launch. I am also a fan
> of having the spacecraft for the trip be rather larger than it would
> be practical to launch as a single package.
>
> I believe that a necessary first step for a manned mission to Mars
> is development of a way to put packages in orbit for tens or
> hundreds of dollars per kilo, rather than thousands or tens of
> thousands of dollars per kilo. It would be nice if it could be done
> without high accelerations, too. Of the systems I've seen proposed
> (and as a science fiction fan, I've seen a fair few), the Space
> Elevator concept looks the best. Although some very interesting
> work has been done, and I think it has potential for actually coming
> to pass, I decline to hold my breath until it happens.
>
> Rather than focusing on sending people to Mars, I think we should
> send progressively more sophisticated robots, all the way up to
> robots build some of the infrastructure that will be needed for an
> extended stay by people.
>
> As for the radiation issue during the trip; I read an interesting
> article that contended a big source of radiation would be
> Bremsstrahlung radiation from the interaction of high energy
> particles and the metal ship around the crew. The proposed fix was
> to use a very large inflated spaceship for the voyage, with small
> landers for the trips to and from the surface of Mars. Selling the
> "balloons in Space" concept may take some work, however.
>
> -----Original Message-----
> From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl]
> On Behalf Of Rainer.Facius at dlr.de Sent: Tuesday, September 30, 2008
> 5:58 AM To: JPreisig at aol.com; radsafe at radlab.nl Subject: AW: [
> RadSafe ] [RadSafe]Mission to Mars---Fission Propulsion
>
> Joe,
>
> as long as human astronauts (instead of chimpanzees) are manning the
> spacecraft, mission duration is the NUMBER ONE factor driving the
> risks to their health and hence the (counter-) measures to be taken
> to ensure a safe and healthy return.
>
> The probabilities of encountering life-threatening medical
> conditions (physiological and psychological) or critical technical
> equipment failures are roughly proportional to mission duration. The
> risk of acute early radiation effects (and secondary risks from
> associated performance decrements) due to unforeseen large solar
> energetic particle events adds to these risks for untoward mission
> outcomes and is again roughly proportional to mission duration
> (solar activity held constant). The risk for late radiogenic cancer
> from (chronic) exposure to galactic cosmic radiation again is
> proportional to mission duration. For reference missions to Mars of
> about 1000 d duration during phases of minimum solar activity (such
> as now), galactic cosmic ray exposures behind conventional mass
> shielding can accumulate to 1 Sv.
>
> So, dollars spent into attempts to reduce mission duration are by
> far the most cost effective in reducing the health risks of Mars
> travelling astronauts.
>
> Fundamental physical/technical constraints limit the specific
> impulse achievable by chemical propulsion to somewhere between 400
> to 500 seconds. With solid nuclear power propulsion, specific
> impulses between 500 and 1000 s are achievable whereas with a gas
> core nuclear rocket specific impulses between 1000 and 6000 s can be
> obtained, thereby reducing mission durations by the respective
> factors. The technologies for solid nuclear power propulsion - and
> hence for a reduction of mission duration by a factor of two - are
> at hand but certainly not the limit. Los Alamos has spent quite some
> efforts for advancing the gas core nuclear rocket technology - at
> least theoretically - and reductions of mission durations by factors
> up to 10 are conceivable thereby.
>
> My personal prognosis is: If manned missions to Mars will occur,
> they will use nuclear propulsion. Given that man's strive to extend
> his limits historically has only been limited by the laws of nature,
> my guess is that manned missions to Mars will take place. Whether
> this will generate sizeable job opportunities for health physicists
> remains to be seen.
>
> Regarding fusion propulsion, the experience of my lifetime with
> announcements of fusion energy as lurking just around the corner of
> the next decade makes me sceptical when or even whether we will see
> it working. Five to six decades of such announcements have worn out
> my 'faith' into this energy option
>
> Thank you for your stimulating note - and good luck at your work.
>
> Kind regards, Rainer (going back to work :-)
>
> PS: At http://www-pub.iaea.org/MTCD/publications/PDF/Pub1197_web.pdf
> you can download the IAEA publication STI/PUB/1197 (2005), The Role
> of Nuclear Power and Nuclear Propulsion in the Peaceful Exploration
> of Space. Note, in some instances they have specific impulses too
> large by a factor of ten. Dr. Rainer Facius German Aerospace Center
> Institute of Aerospace Medicine Linder Hoehe 51147 Koeln GERMANY
> Voice: +49 2203 601 3147 or 3150 FAX: +49 2203 61970
>
> -----Ursprüngliche Nachricht-----
> Von: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] Im
> Auftrag von JPreisig at aol.com Gesendet: Montag, 29. September 2008 23:17
> An: radsafe at radlab.nl
> Betreff: [ RadSafe ] [RadSafe]Mission to Mars---Fission Propulsion
>
> Dear Radsafe:
>
> This is from: jpreisig at aol.com .
>
> Hello Again Radsafers:
>
> Hope you all are well today and don't require a US Federal
Bailout....
>
> I've been thinking about space travel to Mars again using
fission
> propulsion. I refer you to several articles by Freeman Dyson
> in the beta volume of the book "Adventures in Experimental
> Physics" --- Bogdan Maglich, editor. I hope you can find it in
> your library. In one of the articles Dyson indicates that one
> can use fission propulsion (without resorting to bomb propelled
> rockets> to achieve exhaust velocities that are twice as large
> as the velocities that can be reached via chemical propulsion.
> >From this,
> I infer that a readily achieveable fission propelled rocket can
> ultimately be designed which can go twice as fast as chemically
> propelled rockets (at least>. This would reduce the round trip
> time to Mars from 3 years to about 1.5 years. This is helpful
> if one is living in a spaceship for such a long time. Further
> additional techniques used to reduce the total travel time to
> Mars would also be desirable.
>
> So, considering use of Uranium to power such a trip, how
> could such trip be safely made? For takeoff, the fission
> reactor propelling the rocket
> (or whatever> would largely contain Uranium (and not so much Cesium
> or Strontium which are produced via fission>. So, let's assume
> a safe launch can be made.
>
> The rocket and astronauts (hopefully not
> Chimpanzees???!!!> would fly to Mars, land on the planet's
> surface, and do whatever science and other tasks which need to
> be done. If necessary, a chemically propelled lunar/Mars type
> lander could be used to get to Mars surface from the original
> rocket or Mother ship. Upon completion of their time on Mars,
> the astronauts would direct their spaceship towards Earth, to return
> to home.
>
> However, instead of returning directly to Earth, the
> spaceship would land on the Moon, not using a lunar/Mars type
> lander. The spaceship would land directly on the Moon's surface,
> not to return to Earth anytime soon. The spaceship would be
> left on the Lunar surface, complete with its reactor intact.
> There's not much weather or wind storms on the Moon, so the
> spaceship could stay there a long time without dispersal of any fission
> products or the original Uranium fuel.
>
> So, this leaves the astronauts on the Moon with the
> scientific samples, stored data on computers, etc. What happens
> next??? A second chemically propelled rocket is sent to the
> Moon, and using a Lunar lander the astronauts are picked up and
> return to Earth in the second spacecraft. Mission accomplished.
> I didn't say the space mission would be inexpensive.
>
> In 200 years (a fair number of half-lives) the original
> fission reactor could be picked up from the lunar surface and
> returned to Earth for processing and/or storage.
>
> If we ever perfect a fusion propelled rocket system, much
> of the preceding described effort becomes unneccessary.
>
> Just something to think about. I think such a fission
> propelled rocket system could be built in the relatively near
> future. Oh my, jobs for Health Physicists and/or Nuclear
> Engineers in space.
>
> The airplanes/jets which takeoff vertically are called Harriers.
>
> Another few years of relatively few (named> hurricanes
> and/or tropical storms like 2008 (so far> and I'll have to
> say that the global warming hypothesis is fizziling out.
>
> Now, get back to work????
>
> I hope you have a wonderful week.
>
> Regards, Joseph R. (Joe> Preisig, Ph.D.
>
> <BR><BR><BR>**************<BR>Looking for simple solutions to
> your real-life financial challenges? Check out WalletPop for the
> latest news and information, tips and calculators.<BR>
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