JF Mezei wrote on Sun, 6 May 2018
15:27:18 -0400:

On 2018-05-04 09:12, David Spain wrote:

concrete. If I recall, a major objection to these being attached to the
ISS is the vibrations they would induce that would interfere with other
experiments.


One could argue ISS should have been primarily a spinning station, with
0G experiments at the centre. This would have given crews a better
environment and I have to assume that crystal growing experiments that
really require 0G don't take that much space and the module at centre of
the circular station would provide that environment.


One could argue anything. The question is whether the argument makes
sense and is executable. From the things you say, I assume you're
thinking about the old 'wheel' design for a station. Think about how
big such a station would have to be. ISS can use all the 'walls' of
the modules, since the whole works is in 0g. That wouldn't be true on
a spinning station. How many launches to get the pieces up? How do
you assemble it? How long before first occupancy?

You're also confused about 0g at the center. You'd have some small
amount of gravity with angular forces. Not a good place to do things
like trying to grow 0g crystals.


HOWEVER: while growing crystals is one aspect, one more important aspect
was studying whether humans can live in 0G for a long time and what
measures/exercises rediuce or eliminate the negative impacts.

If ISS human experiments have shown it is not possible to eliminate 0g
problems with long duration flights, this is a very important finding.


'IF'? Do you bother to know ANYTHING about the things you bring up?


And ISS has allowed to quantify body performance degradation, so that on
a flight to Mars, they can predict what conditions humans would be in
when they arrive, if they follow similar exercise regime as on ISS.


To some extent this is true.


So not having artificial gravity on ISS is/was an important step in
learning about living in space. (even if the end result is a failure to
learn how to stop body degradation).


But it also prevents any follow-on research.



I need to do the math on this hand-wave of mine. It'd be interesting to
see, given the dimensions of BFS, how much spin could be induced before
ill crew effects and to what degree of 'g' that would yield.


You also need to consider ECLSS. O2 gnerators, toilets and anything else
that uses liquids. There are vast differences how they work n 0g versus
gravity. If a component is designed with assumption bubbles don't rise,
but with artificial gravity, bubbles move, then how it is mounted
matters because bubbles may be flowing to the bottom or sides, not
nessessarily to the "top" of the unit.

So if BFS is gonna spin, it really needt to be designed as such. (and
also consider whether it will have one large burst of accelerationa and
then coast for 6 months, or use slow but constant acceleration and then
slow but constant deceleration once more than halfway to Mars).


It's not big enough. Spinning around its long axis you get a couple
hundredths of a g at the outer skin for rotation rates that humans can
tolerate. Spinning it around its short axis isn't particularly
useful, either. In either case, you'd need everything built so that
'up' could be two different directions; through the tail when landed
or under acceleration and some other direction when spinning.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn