[ RadSafe ] [RadSafe]Mission to Mars---Fission Propulsion
Sam Iverstine
sam_iverstine at yahoo.com
Thu Oct 2 08:07:16 CDT 2008
Space exploration was the main impetus that got myself and many other scientists interested in science [I actually thought becoming a health physicist with nuclear navy background would qualifiy me to do work on spacecraft]. Even if the space exploration challenge is pie in the sky, it still motivates me to this day to do better science. Perhaps over-extended space exploration will motivate a generation of scientists and the US will one day have a scientist president (vs. lawyer) and we will all achive nirvanna and have Plato's philosopher-king as our leader.
Cheers!
Sam Iverstine, MS, CHP
----- Original Message ----
From: "Brennan, Mike (DOH)" <Mike.Brennan at DOH.WA.GOV>
To: radsafe at radlab.nl
Sent: Tuesday, September 30, 2008 5:39:27 PM
Subject: RE: [ RadSafe ] [RadSafe]Mission to Mars---Fission Propulsion
While I am a big time fan of space exploration, I believe that, at this moment, the focus should not be on manned missions. I think that there is VAST amounts that can be learned, and learned sooner and cheaper, without sending people. This applies both to the Moon and to Mars.
Now, if the transportation costs drop a great deal, the balance may shift. But for now, the best man for the job is a robot.
I do not believe, however, that the need to address problems on Earth is a good reason to not pursue science in space. What we have learned from men and machines in space, and what we have learned to be able to put them there, has changed our understanding of our universe, our world, and ourselves in ways that are mostly for the good. It would be almost impossible to name all the ways the lives of most people have been impacted by the knowledge and attitudes the greater "we" have gained from going into space.
-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On Behalf Of Franz Schönhofer
Sent: Tuesday, September 30, 2008 2:03 PM
To: 'Jerry Lahti'; Rainer.Facius at dlr.de; radsafe at radlab.nl
Subject: 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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------- End of Original Message -------
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