On 19-07-26 20:54 , David Spain wrote:
On 7/26/2019 12:58 PM, Niklas Holsti wrote:
On 19-07-24 20:18 , wrote:
On Tuesday, May 21, 2019 at 2:15:19 PM UTC-4, Niklas Holsti wrote:
The SpaceX plans for the first Mars trips involve two Starships
making the trip at the same time. The SpaceX videos show a Starship
flying alone, in a fixed attitude (pointing away from the Sun) thus
in free fall. From other sources there is some concern that a
multi-month weightless trip may incapacitate the pilots and
passengers, for example resulting in blurred vision when they are
again subjected to acceleration or gravity. Here I propose a
possible solution: cable the two Starships together in a
nose-to-nose attitude and rotate them to provide simulated gravity
during the trip.

Do you have any numbers on this? How much propellant would be
necessary to spin up the rotation?

Assuming a 50 m radius of rotation and a desired acceleration
(pseudo-gravity) of 3 m/s/s, a rotational speed of about 12.2 m/s is
enough. So quite small compared to orbital velocities.


Have you calculated as to whether it would be necessary to use curved
decks to preserve gravity normal vectors across the entire radius of
deck surface that would be off-axis from the rotation?

If the Starship outer diameter is 9 m, the inside walls are perhaps 4 m
from the ship's center. With a 50 m radius of rotation, the centripetal
acceleration at 4 m from the ship's centerline is tilted by some 4.6
degrees to the ship's long axis (that is, to the "vertical" at ship's
center). This is clearly noticeable but I think it would be tolerable.
However, you shouldn't fill your soup-plate to the very edge and then
set it down on a table close to the ship's wall... leave some free-board
and take "seconds" instead. Or the table could have some adjustable
levelling mechanism.

Better keep the decks flat, I think.

I suppose it would depend on the rotational radius.

Doubling the rotational radius halves the off-axis angles, but increases
the required velocity by sqrt(2).

Also let's not forget the centrifuge approach ala the movie 2001: A
Space Odyssey. One (or two) sections of the Starship could be put in
(counter)rotation to provide artificial gravity within the section(s).
It does introduce issues of vibration and spacecraft stability.

That would require major changes to Starship design, or meet with the
same problems as the next suggestion:

Or even
more simply, just put the spacecraft into a spin along the flight path
vector. Thus no 2nd ship required or fancy rendezvous and un-tether
maneuvers needed.

Spinning (rolling) around the long axis would give a rotational radius
of only 4.5 m, max, giving disorientating Coriolis and other effects.
The pseudogravity would be radial, 90 degrees offset from the real
longitudinal gravity when the ship stands on its rear fins. Not good, IMO.

This would also allow incremental build-up of
spacecraft by joining future Starships together in LEO to make a larger
spacecraft.

I don't understand how the spin/roll is related to incremental joining
of Starships. In a Starship, one end "kicks" (the aft end) and the other
"penetrates" (the front end); they are not easily connected together to
form a larger living space. At most, one could dock two Starships
front-to-front. Can you clarify what you mean?

Underlying all of lunar & planetary habitation is the assumption that
the human body does not develop strange new diseases from not being in
1G, or that there is some conditioning (PT) needed near 1G to stave off
these effects. Subsequent generations, if born in that environment might
not need that, but might not be able to comfortably live back on Earth
either. Data points we just don't have right now.

Yes, it's a shame that there is no pseudogravity experiment on the ISS.
It seems one was planned, but then cancelled
(https://en.wikipedia.org/wiki/Centri...ations_Module), but it
would have been too small for human use anyway.

--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
. @ .