Radiation shielding for hotel at GEO?

Wouldn't it be nice if there were water on the moon?

()Sorry - broken record effect)

(Len) wrote in message om...
IMO, the real problem is shielding for the transport
vehicle carrying people to GEO, L-5 or the moon.
[...]
For a lunar hotel, the people transport from Earth-to-
moon and back might carry water shielding to the moon,
and lunar materials back. Whether or not this could
yield reasonable economics remains to be seen.

With tethers you can make a shielded transport cycle between
GEO and Lunar orbit with all the delta-vee handled by tethers.
A GEO hotel makes a good staging area for combining the small
payloads tossed every 100 minutes by the LEO tether into a
few big tosses every 2 weeks when the Moon crosses the plane
of the hotels equatorial orbit. A big hotel makes a great
ballast for tossing a big transport. The delta-vee going
from GEO toward the moon is not very high, so it is not hard
to have a tether strong enough for a big transport.

As long as a tether catches as much as it tosses, it takes
very little energy/thrust to operate it. If you are generally
sending more stuff to the moon you will want to bring some
rocks back just to balance the tether traffic. I think it
is really fun that you can sort of lower rocks from the
moon toward the Earth and use that energy to lift stuff
up to the moon.

Going from the suborbital rocket to the GEO hotel is like
4 hours (compared to like 4 days to go to the Moon). If we
could predict when there would not be any solar particle events
for the next 4 hours then this transport would not need much
shielding. If it does need good shielding then we could have
a shield that cycles between the GEO hotel and the LEO tether.

My problem is just figuring out how long the galactic cosmic
radiation will let me live on a GEO hotel before I have to
move onto the Moon, where I can easily have 5 meters of
shielding. :-)

-- Vince

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~
Vincent Cate Space Tether Enthusiast
http://spacetethers.com/
Anguilla, East Caribbean http://offshore.ai/vince
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~

You have to take life as it happens, but you should try to make it
happen the way you want to take it. - German Proverb

Len wrote:

IMO, the real problem is shielding for the transport
vehicle carrying people to GEO, L-5 or the moon.

Yes, but people might spend 3 or 4 days on the transport, but many weeks or
months in the hotel.

Given that where secondaries are concerned inadequate shielding is worse than
no shielding at all, I'd recommend no shielding, just like NASA did for
Apollo. For solar flare events, I would just recommend careful monitoring of
solar conditions, and stopping traffic flow during flare events.

--


Regards,
Mike Combs
----------------------------------------------------------------------
We should ask, critically and with appeal to the numbers, whether the
best site for a growing advancing industrial society is Earth, the
Moon, Mars, some other planet, or somewhere else entirely.
Surprisingly, the answer will be inescapable - the best site is
"somewhere else entirely."

Gerard O'Neill - "The High Frontier"

(Alex Terrell) wrote in message om...
"Passive shielding is known to work. The Earth's atmosphere supplies
about 10 t/m^2 of mass shielding and is very effective. Only half this
much is needed to bring the dosage level of cosmic rays down to 0.5
rem/yr. In fact when calculations are made in the context of
particular geometries, it is found that because many of the incident
particles pass through walls at slanting angles a thickness of shield
of 4.5 t/m^2 is sufficient.

Thanks!

If using a Rotovator you could base your hotel at L4 / L5.

I really like the potential of launching a SSTT (single stage
to tether) rocket every 100 minutes that an equatorial LEO rotovator
gives me. But the Moon or L4/L5 would only cross an equatorial
orbital plane every 2 weeks. So if I were to toss directly from
LEO I could not use my rocket or LEO tether as often. So it seems
better to accumulate stuff at GEO and then do a few big tosses
from there every 2 weeks. The smaller delta-V from GEO means we
don't need so much tether mass to handle a big payload.

This may take 1 to 2 days to reach instead of 4 hours, but the orbital
insertion requirement is less.

The toss from LEO to L5 is harder than the toss to GEO. Having some
delta-v at GEO is not bad as it is a small enough amount that a tether
can handle it.

I get about 4 days for my tosses to the Moon, and would expect similar
to L5 (would guess longer rather than shorter to L5). The shielding
for this longer time seems more troublesome.

Overall, I think radiation is a huge problem for fixed elevators and
skyhooks, but a rotovator is much less of a problem.

I agree.

-- Vince

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~
Vincent Cate Space Tether Enthusiast
http://spacetethers.com/
Anguilla, East Caribbean http://offshore.ai/vince
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~

You have to take life as it happens, but you should try to make it
happen the way you want to take it. - German Proverb

Mike Combs wrote in message ...
Len wrote:

IMO, the real problem is shielding for the transport
vehicle carrying people to GEO, L-5 or the moon.

Yes, but people might spend 3 or 4 days on the transport, but many weeks or
months in the hotel.

Given that where secondaries are concerned inadequate shielding is worse than
no shielding at all, I'd recommend no shielding, just like NASA did for
Apollo. For solar flare events, I would just recommend careful monitoring of
solar conditions, and stopping traffic flow during flare events.

I suspect that the fact that no Apollo astronauts gat
fried was more a matter of luck than good prediction
capabilty.

Best regards,
Len (Cormier)
PanAero, Inc. and Third Millennium Aerospace, Inc.
( http://www.tour2space.com )
--


Regards,
Mike Combs
----------------------------------------------------------------------
We should ask, critically and with appeal to the numbers, whether the
best site for a growing advancing industrial society is Earth, the
Moon, Mars, some other planet, or somewhere else entirely.
Surprisingly, the answer will be inescapable - the best site is
"somewhere else entirely."

Gerard O'Neill - "The High Frontier"

Vincent Cate wrote:

How much water (or pick some other) shielding would it take for a hotel
at GEO to get the total radiation down to numbers like 25 rem/year or 5
rem/year?

I do know that this has never been tested, but people have been speculating
that a M2P2 http://www.geophys.washington.edu/Space/SpaceModel/M2P2/
magnetic bubble could provide significant shielding against charged
particles just like the earth magnetic field does.

It does need a small but continous stream of plasma to keep the magnetic
bubble inflated, but that should be no problem since the masses involved
are quite small compared to the outgassing of a large manned structure.

Of course a magnetic bubble has no effect whatsoever on neutral radiation
such as gamma rays, but those could be dealt with by other means.

The good thing about a magnetic bubble is that it is very light, so it could
also be used for the transit from LEO to GEO.

regards,

Rüdiger

In article ,
Len wrote:
Given that where secondaries are concerned inadequate shielding is worse than
no shielding at all, I'd recommend no shielding, just like NASA did for
Apollo. For solar flare events, I would just recommend careful monitoring of
solar conditions, and stopping traffic flow during flare events.

I suspect that the fact that no Apollo astronauts gat
fried was more a matter of luck than good prediction
capabilty.

Correct. Flare prediction remains a black art even today, all the more so
because flare radiation does not travel in a straight line and it is
possible for radiation from a flare on the "edge" or even the far side of
the Sun to reach Earth.

Had the 4 Aug 1972 giant flare occurred during an Apollo flight, instead
of between Apollos 16 and 17, the astronauts would have taken quite
sizable radiation doses. Had the 23 Feb 1956 giant flare occurred during
a flight, they would have taken dangerously high doses and all come down
with radiation sickness, although they would *probably* have survived.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

(Vincent Cate) wrote in message . com...
From "Space Stations and Platforms", Gordon R. Woodcock, 1986, page 46,47:

"Cosmic Rays
snip
"Most of the cosmic ray particles are hydrogen and helium nuclei, but
heavy nuclei are also present as shown in Figure 4.9. Cosmic ray
particles are bare nuclei, fully ionized. The heavy nuclei carry
high charge (Z) at high energy and are often called high-LET (linear
energy transfer) or HZE (high-Z, high energy) particles.

"As these particles pass through the structural wall of a space station,
their interaction with the wall usually causes incremental loss of energy
and charge, but very few are stopped. Those that are usually create
cosmic ray showers; occasional head-on collisions with atomic nuclei
in the wall result in both nuclei being shattered into many smaller,
but still higher-energy, nuclear particles.

Does this still happen if the shielding is water? Metal hull or
regolith would cause cosmic ray showers, but what about water? For a
hotel, if there were a double hull with half a meter of water around
the main living spaces, or a storm cellar, would the high energy
daughter events still pose a threat?

Harmon