"My math tells me that the transportation costs are too high for practical development, and a 10 person lifeboat won't make it with the other 6,000,000,0000 people left on the "sinking ship"."

I assume when someone states "My Math" it implies they've actually tried to calculate something.

I have done the math EP. I understand the concepts. The delta V issue is not related to anything you are talking about. It is about whether it makes sense to go to Mars by first going to the Moon. Whatever mass you need to send to Mars is the same for a given mission profile whether you leave from the Moon or the Earth as it does not substantially change the time or shielding involved. Talking about shielding mass in this context is irrelevant, which is why people who know what their talking about don't bring it up. You need less fuel to launch a given mass from the Moon than the Earth, but it takes you more energy to land it on the Moon than to send it straight to Mars. This arguement is for people who propose Mars by way of the Moon. It has nothing to do with the arguement of which is a better destination which your comments seem to imply. Or at least that's the only way I can make any sense out of them. It's an arguement made for the Moon fans who actually realize that Mars is a better destination, but think we should go to the Moon first.

Heres's the math on shielding:

density of rock roughly 3.0 g/cm3

density of water 1.0 g/cm3

3/1=3 times as much depth of water as rock to give the approximate same level of shielding. It's approximately the same because different types of radiation san cause different types of secondary radiation depending on which type of atoms they strike. Being on any large solid body cuts your radiation exposure in half simply by having a large mass beneath you.

The density of our atmosphere is 14.67 lbs/in2 which is sufficient to block cosmic rays to the level we are used to.

3 g/cm3 X 1 lb/453.56g X (2.54cm/inch)^3 = 0.108 lbs/in3 for a density of rock.

14.67lbs/in^2/(0.1084 lbs/in^3) = 135.4 inches of depth of rock to provide the same mass density per square inch as the column of air over our heads.

135.4/12 = 11.28 feet
11.28/3 = 3.76 yards of solid rock
11.28*3 = 33.84 feet of water. A depth easily reached in many lakes let alone ocean worlds.

This means it's easy to provide enough water to shield life from radiation regardless of the condition of the atmosphere as long as it is high enough pressure to accomodate liquid water. This does not even address the protection likely provided by a planetary atmosphere nor a magnetosphere. I understand that you didn't grasp the protetective power of an atmosphere alone, but I still don't see anything in your comments that indicate why you would assume such planets don't have a magnetosphere.

A final note on your very tangential comments. Mars will never be a lifeboat for humanity as individuals. It will never have a carrying capacity equivalent to Earth's which is why any sane space fan should always be for protecting Earth from dangers like pollution, impacts, nuclear war, biological warfare, and global warming. Mars' value as a lifeboat is like the titanic's, some will survive even if Earth is wiped out. Secondly it serves as a potential island of stability in the event of a global disaster to help rebuild Earth much as the US and developed world has for third world disasters. I will also agree that costs are too high to make colonization feasible at this time. Elon Musk is trying to change that. NASA's job is to play Lewis and Clark not the Jamestown company - explore and find out what resources are there so individuals can judge whether it is worth the risks to colonize. Unlike Lewis and Clark though science will be the primary goal of a NASA Mars mission not a secondary one.

Regards,
Mark