Hard Sci-Fi: Artificial Gravity
Hi guys,

In this update, we are keeping study the science behind the Daedalus, the explicit part that makes the whole After Reset universe so special. In one of the previous updates we already took a look at our "Way to Venus" and the "Daedalus Space Station (DSS)".

And now I’d like to invite you to the topic of micro-gravity,  artificial gravity the terms of spacecraft and c-Rings of the DSS. Once  again, my studies began on NASA’s Reddit several month ago...

MICROGRAVITY HARM

In popular media, in soft sci-fi movies and games, as well as in our  childhood, zero gravity looks sweet, cool and fun, making us dream like  we fly serenely and relax. Though, the fact is that human body does not  fit for zero/micro gravity. To be more precise, microgravity degrades  human body.

According the NASA Office of Inspector General Report from October 2015,  one of the major obstacles for the long-term stay/travelling in space  is zero gravity (or weightlessness) which cause following serious  deleterious effects on human health:

1. Loss of Bone Mass (or Spaceflight Osteopenia)  – modern astronauts lose 1-2% bone mass per month spent in space. That  inflicts critical negative effect on human health. Excessive bone loss  and the associated increase in serum calcium ion levels will interfere  with execution of mission tasks and result in irreversible skeletal  damage. Current countermeasures (increasing dietary calcium, vitamin D,  clay eating) can only slow down the process. Though, the only achievable  future solution is artificial gravity.

2. Loss of Muscle Mass – another critical negative effect involves the loss of muscle mass.  Without the effects of gravity, skeletal muscle is no longer required  to maintain posture and the muscle groups used in moving around in a  weightless environment differ from those required in terrestrial  locomotion. The muscles start to weaken and eventually get smaller.  Consequently, some muscles atrophy rapidly, and without regular exercise  astronauts can lose up to 20% of their muscle mass in just 5 to 11  days. The types of muscle fiber prominent in muscles also change. Slow  twitch endurance fibers used to maintain posture are replaced by fast  twitch rapidly contracting fibers that are insufficient for any heavy  toil. Despite nowadays each astronaut spends at least two hours per day  exercising on the equipment, various treadmills (like COLBERT), the aREDs  (advanced Resistive Exercise Device), stationary bicycles can only slow  down the process. The only achievable future solution is artificial  gravity.

3. Fluid Redistribution – in space the autonomic reactions of the body to maintain blood pressure are not required and fluid is distributed more widely  around the whole body. This results in a decrease in plasma volume of  around 22%. Because it has less blood to pump, the heart will atrophy. A  weakened heart results in low blood pressure and can produce a problem  with "orthostatic tolerance," or the body’s ability to send enough  oxygen to the brain without the astronaut's fainting or becoming dizzy.  Upon return to earth, the blood begins to pool in the lower extremities  again, resulting in orthostatic hypotension. Because weightlessness  increases the amount of fluid in the upper part of the body, astronauts  experience increased intracranial pressure. Beyond that, due to  increases pressure on the backs of the eyeballs, it affects their shape  and slightly crushing the optic nerve. No cure exists; the only  achievable future solution is artificial gravity.

4. Motion Sickness (or Space Adaptation Syndrome)  – not very pleasant but for up to 52h human brain adapts. Caused by the  conflict between what the body expects and what the body actually  perceives. Can be easily surprised by transdermal dimenhydrinate  anti-nausea patches (which are usually used nowadays whenever space  suits are worn because vomiting into a space suit could be fatal).

ARTIFICIAL GRAVITY

Okay, based on the Nautilus-X drafts let’s imagine such centrifuge ("c-Gravity Ring" or "c-Ring",  as it is called on the DSS). Artificial gravity, here is a result of  the use of particularly centripetal force. The only (but decent) issue  to make such structure nowadays is the size (hence, the cost) of the  spacecraft required to produce centripetal acceleration.

But we’re speaking about realistic 2100+ AD with all resources of  NASA, ESA, Roskosmos, CNSA, ISRO, JAXA, CSA, UKSA, CSAE, CSIRO and ISA  combined... So that is what it turned out to be:

1. Dimensions of the Nodes: I shared in one of the previous updates  the first schemes of the Universal Spacecraft Pressurized Nodes (USPN)  such c-Gravity Ring might be constructed from. I marks them as “colored  Nodes”): Blue Node (with 3 gateways), Red Node (with 2 gateways and one  “window”), Black Node (with 2 gateways). As they are almost cylindrical,  each USPN is: Length: 16m; Height: 10m; Width 3m. With Pressurized  Height: 12m; Pressurized Radius: 2m. Hence, its Pressurized Volume: V =  π(r^2)h = 3.14412 = 150m3.

N.B. The whole ISS’ PV is 916m3.

2. c-Gravity Ring Radius: Than we need to attach those universal  modules into regular 16-gon (I tried various modules size combination  and came to that 16-gon for the colored modules above as the most  realistic) “ring” and calculate the radius of the proper c-Gravity Ring,  where S is the length of any side, n is the number of sides: c-Gravity  Ring Radius = S / ( 2sin(180/n) ), = 16 / (2sin11.25) = 16 / (2*0.195) =  16 / 0.39 = 41m.

N.B. Nautilus-X’s centrifuge has R of 14m.

3. c-Gravity Ring Rotation Speed: As we want to make Centrifugal  Force (F = m(w^2)Radius) be equal to the Gravity Force on Earth surface  (F = mg), that leads to (w^2)Radius = g, where g = 9,8m/s2 and Radius we  already calculated above (Radius = 41m). Thus: c-Gravity Ring Rotation  Speed = sqrt (g/Radius) = sqrt (9.8/41) = sqrt(0.239) = 0.489 rad/s =  4.67 rev/min.

N.B. Nautilus-X’s centrifuge has RS of 10 rev/min.

ENSUING DETAILS

Based on the c-Gravity concept for the DSS I also encountered two  important points of interest to bear in mind that follows the concept:  gyroscope axis stabilization and Coriolis force.

1. Axis Stabilization. Well, the rotation of Nautilus-X’s  centrifuge as well as the rotation of the c-Gravity Ring turns the  whole spacecraft into a huge gyroscope in space. That is definitely good  because it helps to fix the DSS on the exact position above the Venus  surface. Rotation of the ring is provided by the drives situated on the  c-Gravity Ring surface opposite each other.

Though, aside from Gravity-Gradient Dtabilization  to make the DSS to always point the planet, we also need to stabilize  the axis of the DSS so that it doesn’t rotate with the c-G Ring. So  despite each of the ring has flywheel stabilizers like on Nautilus-X by  default DSS’s c-Gravity Rings function as coaxial rotors on helicopters  (like Ka-50) compensating rotation of each other.

2. Coriolis force. We should keep in mind, that this  isn't really gravity we create. Once we're no longer touching a  surface, there's no force on us at all, and we'll travel in a straight  line while the ground moves under us. If you were to jump straight up,  you'd be adding your jump speed to your spin-related speed and fly off  at an angle. Odds are pretty good that you'd end up drifting spinward,  since you'd be "cutting the corner" as well as traveling faster overall  than the ground (ground speed plus your jump speed will be greater than  the ground speed), and you'll hit with a speed spinward with respect to  the ground. Jump up, come down sideways. This is a frame effect, just  one of many.

That is the time to point on c-Gravity ring’s huge radius and  rotation speed that preserves astronauts form critical effects of such  king during the mission. The case is that the most of Coriolis problems  can be minimized by having everything at a constant radius (large open  space down the middle of the ring) and spinning quickly enough that  you're not going to catch up to the spin rate. E.g. for an inner surface  of 10 meters radius, a station spinning once every five or six seconds  will simulate a comfortable fake gravity, and you'd have to sprint  before you'd start noticing changes in your effective weight.

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I hope you've liked that peace of space science and our hard  sci-fi approach, mates. I’d be glad to keep it and advance during the  development with the help of science consultants which are quite common  among After Reset fans.

Please, feel free to copy/past here in comments  your thoughts about the current subject in hand, in case other guys feel  like to add something more or just to discuss.

Thanks for your support and cheering, guys!

Sincerely,
Richard.