One of my keen interest is still with regard to learning more about
what sort of radiation there is at Earth L4/L5, as I've got a fairly
good idea as to what the relatively cool zone or semi-protected pocket
at Earth L2 has to offer. In further knowing what's at Earth L4/L5,
this knowledge would enable some further understanding as to what to
expect once a mission is fully solar exposed, whereas the solar
minimum (not maximum) is by far introducing the greater risk from
creating secondary radiation. Any pointers or leads as to the
radiation dosage at L4/L5 will be looked into, subsequently applied
into a couple of ongoing research papers (along with your name as
credit for this and of whatever other you'd like to contribute).

As for regarding the planet surface radiation, such as of Mars; this
is some fairly old and thereby outdated info, where the more recent
radiation exposure estimates have been scaled considerably higher,
although this example will offer some raw insight into what's what
with regard to shielding from cosmic rays in general.

From: Ken Myrtle )
Subject: Cosmic Rays, Van Allen Belt, and Radiation Shielding

1/ free space (given as represent a full solar exposure)
2/ surface without atmosphere (1/2 of free space value of sunset to
sunrise)
3/ surface with .007 bar CO2
4/ surface with .007 bar CO2 plus 10 gm/cm^2 aluminum wall
5/ surface with .007 bar CO2 plus 10 gm/cm^2 aluminum wall
plus 50 gm/cm^2 CO2 for radiation coming from more than
45 deg above the horizon (a CO2 tank on the roof).

Dosage to Blood forming organs (calculated at a depth of 5 cm)
| Cosmic Rays REM/yr | SPE
Case | solar min | solar max | REM
1 | 65.6 | 25.9 | 391.5
2 | 32.8 | 13.0 | 195.8
3 | 15.5 | 8.3 | 4.0
4 | 14.4 | 8.0 | 1.9
5 | 13.3 | 7.8 | 0.7


The above research; indicating that the mere 0.007 bar worth of the
Mars CO2 atmosphere seems to cut the influx of cosmic radiation
roughly in half, while cutting the SPE by a good factor of nearly 50,
though as for the prospect of adding an increase in the CO2 density
within a tight space (such as utilizing a surrounding tank of
compressed CO2 @50 g/cm2) manages not more than another 8% reduction
in relation to solar minimum influx.

Obviously the secondary radiation created mostly by the 10 g/cm2 of
aluminum is not being significantly cut by the liquified CO2, whereas
the Solar Particle Event (SPE) dosage is cut by more than half.

Unlike Mars, Venus seems to be surrounded by not only nearly 15,000
times greater density (especially at night) but, it's atmosphere
extends at least a hundred fold further out, thus permitting
sufficient separation or distance for not only blocking the primary
cosmic radiation but for also the secondary radiation to expend it's
energy as it's attempting to get through all that CO2 as well as H2SO4
(30% sulfuric acid) worth of cloud muck. Thus I'm thinking, that the
Venus daytime is not actually so much a cosmic radiation endurance
factor as is the UV consideration, where the ability of near UV and of
sufficient portions of the UV a/b/c spectrums to penetrate those
clouds is considerable, whereas the CO2 aspects are essentially clear
as a bell for whatever is making it through to reaching the surface.

If it were necessary to further reduce secondary radiation by anything
other, I've been informed that hydrogen (H2) is just the ticket. This
indicates that having a thermal barrier of perhaps those H2 filled
micro-spheres, as I've mentioned for accommodating an R-256 barrier of
thermal conduction insulation, within this formula/package the H2
could in fact provide not only the desired thermal isolation but
accommodate the best job of shielding from secondary radiation affects
caused by whatever is your primary shield density. Normally H2 is not
considered such a great thermal insulator, though placing the H2
(preferably under vacuum) within micro-spheres is going to represent
quite another issue, where R-256 might be obtained within as little as
25 mm.

Mars is already providing a near vacuum, whereas Venus is not, though
as for pulling a vacuum on Venus is not such a complicated task and,
as for hot H2 is even better. So, what I'm suggesting is that an
actual surface expedition to Venus is certainly not out of the
question, especially selecting a landing site that's within their
extended season of nighttime. Though a VL2 stationed ISS would more
than suffice as far as I'm concerned, still a spendy proposition but
nowhere as costly nor as risky as for doing anything as stupid as
actually setting foot on Venus. Besides, we might not be welcome.

http://guthvenus.tripod.com/space-radiation.htm
http://guthvenus.tripod.com/vl2-radiation.htm

Regards, Brad Guth / IEIS