A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Space Science » Technology
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Radiation a Mars trip hazard?



 
 
Thread Tools Display Modes
  #21  
Old December 25th 03, 05:10 AM
Henry Spencer
external usenet poster
 
Posts: n/a
Default Radiation a Mars trip hazard?

In article ,
Remy Villeneuve wrote:
...A dense outer shell should try not to stop the particules but
refract or reflect them...


Unfortunately, there are no materials that refract or reflect high-energy
protons to any significant extent.

...like a stealh fighter mostly reflects
radar (F-117), or an X-ray telescope focuses incoming photons.


Stealth aircraft actually work fairly hard at *absorbing* radar; as an
extra, they try to concentrate any remaining reflection in a few specific
directions.

X-ray telescopes focus photons only from one very specific direction.
Solar-flare protons, unfortunately, orbit the local magnetic fields of
the proton cloud and hence come from all directions.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |
  #22  
Old December 25th 03, 05:10 AM
Henry Spencer
external usenet poster
 
Posts: n/a
Default Radiation a Mars trip hazard?

In article ,
Remy Villeneuve wrote:
...A dense outer shell should try not to stop the particules but
refract or reflect them...


Unfortunately, there are no materials that refract or reflect high-energy
protons to any significant extent.

...like a stealh fighter mostly reflects
radar (F-117), or an X-ray telescope focuses incoming photons.


Stealth aircraft actually work fairly hard at *absorbing* radar; as an
extra, they try to concentrate any remaining reflection in a few specific
directions.

X-ray telescopes focus photons only from one very specific direction.
Solar-flare protons, unfortunately, orbit the local magnetic fields of
the proton cloud and hence come from all directions.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |
  #23  
Old December 27th 03, 09:22 AM
Remy Villeneuve
external usenet poster
 
Posts: n/a
Default Radiation a Mars trip hazard?

[snip]

Stealth aircraft actually work fairly hard at *absorbing* radar; as an
extra, they try to concentrate any remaining reflection in a few specific
directions.

X-ray telescopes focus photons only from one very specific direction.
Solar-flare protons, unfortunately, orbit the local magnetic fields of
the proton cloud and hence come from all directions.



Thanks for the enlightment, as usual!

Bottomline is: you have to absorb it one way or another.
  #24  
Old December 27th 03, 06:35 PM
william mook
external usenet poster
 
Posts: n/a
Default Radiation a Mars trip hazard?

"Dr. O" wrote in message ...
http://www.nytimes.com/2003/12/09/sc...ce/09RADI.html

The thing I don't understand is that people have been spending much more
time in orbit than the round-trip to Mars. Although the upper atmosphere
does shield them somewhat, the majority of the radiation is still getting
through. Why are they so concerned then about radiation?

Also, lead shielding will have to be installed in any Mars spaceship anyway
because of the possibility of solar flares.


I'll try this again - my posts seem to be routinely ignored. Ah well.

The Earth's magnetic field traps a lot of the charged particle
radiation that emanates from the Sun. Flights into space that fly
below this field are protected from the brunt of radiation found in
interplanetary and cislunar space.

Information about your query can be found at the following site;

http://radhome.gsfc.nasa.gov/radhome/papers/seeca3.htm
http://books.nap.edu/books/030905698...5.html#pagetop
http://content.aip.org/APCPCS/v246/i1/130_1.html

Basically, the Van-Allen radiation belt sheilds astronauts in Low
Earth Orbit from deadly solar and charged cosmic radiation. Since
rocket boosters are limited in terms of speed and size, their payloads
must be miminum and travel along slow minimum energy orbits. So
called hohmann transfer orbits

http://www.ucar.edu/eo/staff/dward/s...s/appendix.htm

These orbits take years to complete, and if you're sending people, you
need to execute them twice! Once out another back.

So, folks will be exposed to a minimum of 2.5 to 3 years to very high
levels of radiation - or more. This pushes their exposure up past 130
Rems - if they're well sheilded, and far higher, if they're not!

http://srhp.jsc.nasa.gov/project/BNL.htm

NASA and Brookhaven together was able to show that even for a trip to
Mars, which is our neighbor in interplanetary space, there is a real
risk that some if not all of the astronauts would suffer ill effects
from radiation, and if sheilding were not available, may not survive
the trip!

Lead sheilding is heavy even lighter sheilding adds up. Even so, one
can imagine that with robotic systems pre-placed on Mars before their
arrival, it may be possible to send astronauts encased in sufficient
sheilding, who operate throughout their ship and beyond via
telepresence.

http://ranier.hq.nasa.gov/teleroboti...an/Chap2g.html
http://www.foresight.org/Updates/Upd...pdate08.2.html

Radiation hazards are very much the outcome of small payloads and low
final rocket velocities. Larger and more capable rockets will change
this.

Large, fast moving, heavily sheilded vehicles wouldn't require special
sheilding. Its only small, slow moving, lightly constructed vehicles
that have this problem.

http://www.astronautix.com/lvfam/orion.htm
http://www.astronautix.com/articles/probirth.htm
http://science.nasa.gov/newhome/head...p12apr99_1.htm

The nuclear pulse rockets described in the source material above are
capable of flying large heavily constructed, adequately sheilded
throughout, spacecraft on high-speed orbits throughout the solar
system.

This is the way to go in space.

(1) set up launch centers at radiation waste sites and old bomb
test sites throughout the world;

(2) convert all nuclear weapons centers into nuclear pulse
manufacturing
sites;

(3) use current inventory of nuclear materials as fuel source for a
small
fleet of very large spacecrft;

(4) fly off the nuclear material and deposit remotely operated labs
t
throughout the solar system - involving a fleet of dozens of
ships
and tens of thousands of astronauts;

(5) return to the moon, where a long term base is established and
reusable
chemical rockets maintain contact with Earth;

(6) establish an international nuclear research center on the moon,
and
continue the advance of nuclear pulse rockets, as well as space
based
defense research to enforce an enhanced nuclear nonproliferation
regime
on Earth and in space;

This will not only address radiation hazards on a Mars trip, but also
significant radiation hazards on Earth!
  #26  
Old December 30th 03, 12:16 AM
Henry Spencer
external usenet poster
 
Posts: n/a
Default Radiation a Mars trip hazard?

In article ,
Christopher wrote:
Bottomline is: you have to absorb it one way or another.


Couldn't the spacecraft have it's own magnetic field?


To be a useful barrier to incoming particle radiation, the field would
have to be immensely strong or would have to extend over a huge distance
(which means either making it immensely strong at the source, or
generating it with a physically very large structure). It's possible
in theory but impractically hard in practice, at least for now.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |
  #27  
Old December 30th 03, 11:05 PM
Paul F. Dietz
external usenet poster
 
Posts: n/a
Default Radiation a Mars trip hazard?

Henry Spencer wrote:

Couldn't the spacecraft have it's own magnetic field?



To be a useful barrier to incoming particle radiation, the field would
have to be immensely strong or would have to extend over a huge distance
(which means either making it immensely strong at the source, or
generating it with a physically very large structure). It's possible
in theory but impractically hard in practice, at least for now.


To put some numbers on this...

To deflect particles of a given energy, the strength of the magnetic
field B is inversely proportional to the linear dimensions of the
field (assuming identical geometry). Since the stored magnetic
energy is proportional to volume * B^2, the total energy stored
in the magnetic field will scale in proportion to the linear
dimensions of the protected volume.

The Earth's magnetic field outside the atmosphere has a stored
energy equal to about that of a 200 megaton bomb. To similarly protect
a 12 meter sphere (as opposed to a 12,000 km sphere) would require
a magnetic field with the energy of a 2 kiloton bomb. (This is
probably overkill, though.)

Paul

  #29  
Old January 26th 04, 02:10 PM
Toprope
external usenet poster
 
Posts: n/a
Default Radiation a Mars trip hazard?

Couldn't the spacecraft have it's own magnetic field?

To be a useful barrier to incoming particle radiation, the field would
have to be immensely strong or would have to extend over a huge distance
(which means either making it immensely strong at the source, or
generating it with a physically very large structure). It's possible
in theory but impractically hard in practice, at least for now.


Let's turn this around the other way... If we can't deflect it, can we
direct it?


What about making a large magnetic field by creating a large cage
around the ship? Doesn't use much mass and you get a large field. But
it would need to be strong enough to maintain shape while the ship
accelerates. A large magnetic field could use little energy to deflect
radiation and create a radiation free area.
  #30  
Old February 10th 04, 04:07 AM
Brian Trosko
external usenet poster
 
Posts: n/a
Default Radiation a Mars trip hazard?

Toprope wrote:

What about making a large magnetic field by creating a large cage
around the ship? Doesn't use much mass and you get a large field. But
it would need to be strong enough to maintain shape while the ship
accelerates. A large magnetic field could use little energy to deflect
radiation and create a radiation free area.


Won't effect neutrons, won't deflect high-energy photons. High-energy
photons hit the ship, you get a cascade of other high-energy particles.
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
One Way Trip to Mars? Nomen Nescio Space Shuttle 6 November 23rd 03 03:46 PM
Delta-Like Fan On Mars Suggests Ancient Rivers Were Persistent Ron Baalke Science 0 November 13th 03 10:06 PM
If You Thought That Was a Close View of Mars, Just Wait (Mars Reconnaissance Orbiter) Ron Baalke Science 0 September 23rd 03 10:25 PM
NASA Selects UA 'Phoenix' Mission To Mars Ron Baalke Science 0 August 4th 03 10:48 PM
Students and Teachers to Explore Mars Ron Baalke Science 0 July 18th 03 07:18 PM


All times are GMT +1. The time now is 12:58 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.