Re: Mars colonization versus Stanford Torus


Mike Combs wrote:
"Fred J. McCall" <fmccall@xxxxxxxxxxxxx> wrote in message
news:lg6l42tvfcc101pv93nvla3q9raeag93de@xxxxxxxxxx

Then you're just engaging in wishful thinking. Why do you think
private industry is going to spend the money to do this?

For one reason, and one reason only: to make even more money.

Not entirely. Perhaps 90%. Elon Musk is not into Spacex 100% to make
money. That said, he knows he can be fully successful onlyby making
money.

snip

Sorry, I didn't mean for the phrase "Near Earth Asteroid" to leave you with
the impression that I thought a close pass by the Earth was sufficient. The
phrase NEA is commonly used to describe this class of objects.

Best use NEO's. When you use asteroids, people think of >km size. NEO's
come in nice 10m diameter packages. Just missing the gift wrap.

Regarding structures:

You could build a ring-like maglev structure on the moon. There are
however the following problems:
1. Shielding or axial access. You can cover the ring with regolith
shielding, but you can't cover the radius with regolith, as even under
lunar gravity such a dome could not be built. Hence you have problems
with access. The only way is to accelerate / decelerate a "side car".
This is feasible but takes a lot of space as the entire area needs to
be swept out.
2. Awkward gravity gradients. This is a problem if the ring has a large
diameter. The floor of the ring is at an angle to the vertical of about
75 degrees, depending on the planetary gravity and the chosen local
gravity. Hence, as you move up / out, gravity will increase. Hence to
maintain vertical, the angle needs to reduce. So you have a curved
floor with changing gravity.
3. Fairly catastrophic failure mode. If the device is unable to stop,
everything which was resting on the floor now falls to the wall.

So IF humans need 1g (say for reproduction) then orbiting space
stations are prefereable. You can of course confine pregnant females
and young infants to a Maglev train, but this is not an ideal
situation.

Otherwise, other arguments are needed to settle the debate.
snip


Screw that up by having a bearing fail and you just
tore the center out of your station and probably wrecked the ship(s)
(only two) that are docked to your hub.

Possibly. If it turns out to be a major problem, we might dispense with the
de-spun section. Ships could dock in the same manner we saw in "2001".

I prefer a spinning section, loosely attached to a fixed section.
Between the two is an airlock than can be spun up and stopped to match
speeds with either section. That way, no rotating seals are needed, and
any number of ships can dock.

For very large stations, such as a 4km diameter cylinder, this airlock
can take the form of ring train. It then performs the role of a metro
train - taking lots of people from a spin location to a non spin
location.

Remember - if a cylinder has 100,000 people, expect perhaps 10 - 30,000
to want to move to the zero g section every day.

snip

OK, just to be clear, you are talking about a continuous torus, then? Fine,
but now we've gone back from discussing maglevs the size of shopping malls
to maglevs the size of cities.

Well - 1km diameter, 20m minor diameter. The same size as a mini torus.
This is quite feasible. If there was a substantial lunar city, it might
be worth building something like this for exercise and pregnancy.

At this sort of scale, wheels could be used for back up in case the
magnets fail.

Do you know what maglev is? THERE IS NO BEARING!

Maglev's can use attraction or repulsion. The German system uses
attraction, with active dynamic control. This can fail - a maglev train
will then skid to a halt - a "shopping mall" could do the same,
whereupon every one would fall to the walls.

The alternative approach is to use repulsion. This needs superconducing
magnetics and tend to stop watches and pacemakers.

.

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