[ RadSafe ] Mission to Mars
Victor Anderson
victor.anderson at frontier.com
Sat Feb 23 01:05:12 CST 2013
Mike, et. al.,
Some interesting questions and arguments. First off, you pick a high enough
orbit that the USA no longer has jurisdiction and you find a friendly
country that is willing to let you launch shuttles up to your rock. No
jurisdiction, no EIR; Naaa, Naaa; with a raspberry sound. Seriously
comrade, I am sure there are plenty of countries willing to host the
enterprise. It is all a question of money. As more mass is removed to
hollow out the rock, the lighter it gets. This means less power is needed
to move the thing. A goodly sized nuclear reactor can make a fine rocket.
You may even want to use some of that spare "rock" as reaction mass. Now
about that spin thing. You see it is all about how long the rotational
movement is about the center. The longer the arm (r), the less speed
(radians/s) is needed to achieve a given pseudo-force (centrifugal) force at
the end of r. Given that r is long enough, the differential over say 30
meters will be very small. Its all a matter of design. Actually, a lower
force of 0.75 g may be adequate. The issue is preventing loss of calcium
and degradation of the bones due to lack of gravity. The real question is
how to design the project so that it does not take up a considerable
fraction of the US national budget or your host country's budget. The other
issue is how to do the project and keep various groups such as the EPA from
getting involved. The idea of using the Moon as a base has been explored.
Good thinking because of the lower gravity well. I still think that the
elephant under the rug is the radiation environment. Any of you young
health physicists looking for a job?
Victor
-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Brennan, Mike
(DOH)
Sent: Friday, February 22, 2013 4:48 PM
To: The International Radiation Protection (Health Physics) MailingList
Subject: Re: [ RadSafe ] Mission to Mars
I, for one, would love to see you carry the Environmental Impact
Statement for capturing a rock that big and parking it in the near
vicinity of Earth. If you do so, getting the people and equipment up to
modify it probably would cost as much as the proposed mission to Mars
(which, by the way, I disapprove of, because it is a political stunt
with almost no scientific merit. At least in its current Super-Apollo
form).
Be that as it may, the problem of moving that much mass remains. If you
can't get the things you need to make a rock a home up there cheaply,
you can't move your rock to where you want it. I personally think you
still need a space elevator.
Having given it some thought, I've concluded that trying for 1g is more
problem than it's worth. The rotational velocity needed to produce 1g
depends on the radius of your ship, but it is likely to be
inconveniently large. I played with the calculus some time ago, and
found some entertaining things. For example, if you are sitting down
and stand up, your inner ear moves closer to the axis, and experiences a
different force than when you were sitting down. I think it would feel
like you were in an elevator coming to a stop, but I would have to see
if I could find my notes. There would also be a real force experienced
in the direction of rotation, and I think possibly a torque
perpendicular to it, but I don't recall what the numbers said. All in
all, playing basketball in that environment would be a hoot.
On the other hand, what's not to like about using nuclear explosions on
fast moving rocks?
-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Victor
Anderson
Sent: Friday, February 22, 2013 4:23 PM
To: 'The International Radiation Protection (Health Physics)
MailingList'
Subject: Re: [ RadSafe ] Mission to Mars
Good Afternoon,
About that shielding thing: Rocks my friends, big rocks. You find a
rock in space that is about 300 to 500 meters in diameter on one axis
somewhere in the solar system. Doesn't have to be a spherical object.
Put said rock into a high orbit around earth with low yield nuclear
explosives. Hollow the object out so that walls are about 10 meters
thick. Reinforce as needed. That should provide adequate shielding.
If not, make them thicker.
The next challenge is to design the ship so that it can be spun and
provide artificial gravity of about 1 g on the inner side of the walls.
Now install a nuclear rocket and go. Use the materials you got from
hollowing out the new space ship in building same. If you pick the
right rock, you may be able to sell some of the valuable minerals to
help fund your trip. Trips via the surface of Mars and Earth will be
via shuttle craft. Yes, this will be expensive. However, the crew of
the ship can be large and diverse enough that social-psychological
problems are minimal, if someone (gulp) dies, you can have a
replacement, and emergencies can be dealt with. What will be
interesting is the radiation environment outside the ship and the health
physics for dealing with same. My opinion is that such an expedition
should have a small health physics section. Alright, who has a few
extra billions of dollars to fund the trip? :)
Victor
-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Brennan, Mike
(DOH)
Sent: Friday, February 22, 2013 3:12 PM
To: The International Radiation Protection (Health Physics) MailingList
Subject: Re: [ RadSafe ] Mission to Mars
I saw a presentation a couple of years ago that conclude that if you
could assume the passengers were 50+ year-old men, and shielded
appropriately, the trip was doable. If, however, you had to design as
if the passengers might be pregnant 20 year-old women, the shielding
would be too massive, and you couldn't build a ship that met the other
requirements.
I, personally, would rather continue sending SPECTACULARLY successful
robotic probes until a Space Elevator is built. At that point the cost
to get mass out of the gravity well plummets, and all the constraints
for a ship that can get to Mars changes.
On a related note, I've toyed with the idea of how you could use nuclear
power (more-or-less conventional reactor, rather than using
thermoelectric tech) in microgravity, I've pretty much concluded you
need to have it in a spinning ship, with the top towards the axis, and
auxiliary equipment acting to balance the mass. Quite possibly the
design you would wind up with is a disc, or saucer. This would, however
not make for a ship you got to land anywhere.
-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Maury Siskel
Sent: Friday, February 22, 2013 2:47 PM
To: The International Radiation Protection (Health Physics) Mailing List
Cc: JPreisig at aol.com
Subject: Re: [ RadSafe ] Mission to Mars
I thought this trip remains beyond the shielding capabilities to
withstand irradiation exposure -- has this changed? Otherwise sounds
like a great adventure -- Dog also sez ok.
Maury&Dog [MaurySiskel maurysis at peoplepc.com]
========================= On 2/22/2013 12:55 PM, JPreisig at aol.com wrote:
> Dear Radsafe:
>
> Hey All. On US TV News today, Zubrin and colleagues have
announced a private effort to
> reach Mars via spaceship or whatever. The mission will start in
2018. The trip will last 501 days.
>
> Wonder if Maury and Dog will volunteer for the trip??? Get
your spacesuits and Geiger Counters ready???
>
> Regards, Joe Preisig
_______________________________________________
You are currently subscribed to the RadSafe mailing list
Before posting a message to RadSafe be sure to have read and understood
the RadSafe rules. These can be found at:
http://health.phys.iit.edu/radsaferules.html
For information on how to subscribe or unsubscribe and other settings
visit: http://health.phys.iit.edu
_______________________________________________
You are currently subscribed to the RadSafe mailing list
Before posting a message to RadSafe be sure to have read and understood
the RadSafe rules. These can be found at:
http://health.phys.iit.edu/radsaferules.html
For information on how to subscribe or unsubscribe and other settings
visit:
http://health.phys.iit.edu
_______________________________________________
You are currently subscribed to the RadSafe mailing list
Before posting a message to RadSafe be sure to have read and understood
the RadSafe rules. These can be found at:
http://health.phys.iit.edu/radsaferules.html
For information on how to subscribe or unsubscribe and other settings
visit: http://health.phys.iit.edu
_______________________________________________
You are currently subscribed to the RadSafe mailing list
Before posting a message to RadSafe be sure to have read and understood the
RadSafe rules. These can be found at:
http://health.phys.iit.edu/radsaferules.html
For information on how to subscribe or unsubscribe and other settings visit:
http://health.phys.iit.edu
More information about the RadSafe
mailing list