Permanent space stations in orbit around Mars or Venus will have to be equally radiation shielded, from all directions. Because of its high density, lunar iron or iron extracted from asteroids may be the most convenient way to internally shield permanent habitats in space– especially rotating habitats.

Assuming that interplanetary journeys are going to take less than 1.5 years to reach their destinations within the solar system, 30 centimeters of water should be more than enough to protect astronauts from heavy ions and major solar events while also keeping their general radiation exposure well within NASA short term and long term exposure limits.

Marcel

No astronaut has ever been hurt by either radiation or microgravity. Those are red herrings for the space hypochondriacs. Astronauts die because their spacecraft explodes. There are test pilots who don’t care about the theoretical 3% probability of getting cancer sometime later in life for going to Mars, if they do it completely unshielded. They don’t need a nanny to “protect” them from doing what humans do when at good spirits. Your argument is not relevant. It’s just a bad excuse for not going to school today.

But lunar resources are also the key to sustainable human space travel beyond cis-lunar space, IMO.

Lunar water and propellant derived from lunar water for reusable LOX/LH2 spacecraft could allow humans to travel to the orbits of Mars, Venus, and even Jupiter.

There’s no logical reason to confine long term human expansion into space– solely to the Moon.

Marcel

The space station to nowhere and its commercial cargo and crew albatross’, the Absurd Retrieval Mission, and the J2M all need to be unceremoniously dumped in the trashcan.

The SLS core production at Michoud needs to be expanded to support a minimum of 6 missions a year while 8 to 10 would be much better and just as easy to accomplish.

The NewSpace “entrepreneurs” who are currently the worst thing to ever happen to space exploration can turn their attention to robot lunar landers and actually do good instead of harm.

Before the upper stage wet workshops and tethers there is that most critical missing piece of hardware to invest in: the pressure fed booster originally specified for the shuttle.

Abandon the dead ends of LEO and Mars and point the agency toward the ice on the Moon.

“And, since protons produced in the thick GCR shield and spaceship, or surface vehicle, are the most essential risk issue for astronaut health, it is worth noting again:”

That should have been written as:

“And, since neutrons produced in the thick GCR shield and spaceship, or surface vehicle, are the most essential risk issue for astronaut health, it is worth noting again:”

The “protons” should have been “neutrons”. Sorry about my confusing writing mistake!

The large cascade of neutrons is apparently the main issue with using thick shielding.

A meter, or more, thick layer of Iron is a good shield against the cascade of high energy neutrons caused by the heavy nuclei among the cosmic rays hitting into thick shielding.

Due to its density and because it is the “shielding material of choice for neutrons above 20 MeV” Lunar iron might become quite useful as shielding on the Moon and as an export to Cislunar Space because of its ability to shield against GCR while using much less mass than H2O.

Lunar iron might be layered with another material on the inside and nearest to the habitat to stop neutrons below “20 MeV”.

More research seems to be needed.

“The relatively few heavier nuclei among the cosmic rays do as much or more damage than the protons because their ability to break bonds is proportional to the square
of their electric charge. An iron nucleus, for example, does 676 times more damage than a proton does.

To match the protection offered by Earth’s atmosphere takes the same one kilogram of shielding material per square centimeter, although astronauts could comfortably make do with 500 grams, which is equivalent to the air mass above an altitude of 5,500 meters. Any less would begin to be counterproductive, because the shielding material would fail
to absorb the shrapnel. If the material is water, it has to be five meters deep. So a spherical water tank encasing a small capsule would have a mass of about 500 tons. Larger, more comfortable living quarters would require even more.Water is commonly proposed because astronauts would need it anyway and because it is rich in hydrogen. Heavier elements make less effective shields because the extra protons and neutrons in their nuclei fall in one another’s shadows, limiting their ability to interact with an incoming cosmic ray. To increase the hydrogen content, engineers could use ethylene (C2H4), which has the further advantage that it can be poly merized to polyethylene, a solid, thereby avoiding the necessity for a tank to contain it. Even so, the required mass would be at least 400 tons-
Pure hydrogen would be lighter but would require a heavy pressurized vessel.”

“You really don’t need to use methane-”

Nothing can push the required kiloton range cosmic ray water shields Beyond Earth and Lunar Orbit (BELO) except nuclear energy and only one form of nuclear propulsion will work- and that form is not the pathetically inefficient Nuclear Thermal Rocket. Even if chemical propulsion could do the job (it absolutely cannot without a Battlestar Galacta full of propellant) it is a fundamentally bad idea to expect “solar powered cryocoolers” to successfully maintain several thousand tons of liquid hydrogen propellant for month after month.

Mars is a dead end anyway. No reason to go there. This fantasy that Mars will be some kind of utopian second home for humankind is bizarre in the extreme.

The last thing NASA needs right now is another ‘reset’ moment, development-wise.

Actually, we do not know who Trump’s “space advisors” are (or will be).

The things you are talking about are generally attributed to former Congressman Robert Walker, who has been a Trump supporter and assumed to be on the Trump transition team.

Scuttlebutt as of this morning is that Walker is saying he is not on the transition team.

If true one reason might be that Vice President Elect Mike Pence is now running the overall team and does not want any lobbyist on it. Walker has been a lobbyist, working in the past for (among other entities) SpaceX.