Artificial Gravity: punctuated gravity using a centrifuge

[Paul451]

after humans get over our initial infragravity phobia

What a bizarre comment.

[edzieba]

Again the "proper" effective solution for Mars or the Moon (vs a Starship or space colony) is just to use wearable weights.

And no, despite the prematurely confident objections of certain fiction writers, it doesn't really matter that weights don't perfectly reproduce 1 g exercise. It's "close enough," and at 1/1000th the cost of more....   fanciful approaches.   

Even on space colonies I expect — after humans get over our initial infragravity phobia — it will be common to see designs with something like 25-50% gravity, with the rest "made up for" (on an as-needed basis) by using wearable weights + more traditional exercise regimens similar to current countermeasures.

Unless you can add training weights to your eyeballs or to individual cells, that doesn't help all that much with the known microgravity health issues and introduces a whole slew of new problems (reduced 'weight' coupled with increased inertia).

The issues with 'just add weights' are well known and nothing to do with obliquely referred to 'fiction writers'.

[Twark_Main]

add training weights to your eyeballs

That's what the 25-50% gravity is for, obviously.   

I included large error bars because we don't (yet) know exactly what level of gravity is required to counter fluid effects.

a whole slew of new problems (reduced 'weight' coupled with increased inertia)

There are no "new problems" with inertia. As I said it's not an exact reproduction of 1g, but that's okay.

In some ways it's actually better that it's not a perfect simulation, because you don't need to alter your lean angle (which is very different on Earth vs the Moon!) when wearing vs not wearing the weights. This makes it less likely for "mode confusion" to cause stumbling and falling.

The issues with 'just add weights' are well known and nothing to do with obliquely referred to 'fiction writers'.

Don't tell me. Tell that to the person who "authoritatively" quoted a certain fiction writer (either Azimov or Clarke) the last time this came up. I don't have the link handy but you can search the forum.

[Twark_Main]

after humans get over our initial infragravity phobia

What a bizarre comment.

If you have any sort of argument, then please do make it.

The phobia I mention is very real, and it's on full display whenever the subject comes up here. Edzieba and his stealthily-made assumption above that "my eyeballs must need extra countermeasures for anything less than 99.9% gravity" is one example.  I think it's highly telling that his reply wasn't something like "hey I think you need 60% gravity for eyeballs instead of 50%," it was just an automatic freak-out absurd strawman the moment he saw anything lower than 1g. 

Last I checked the fluid effects are mitigated even at "merely" Mars gravity. By setting my error bars up to 50% I was being generous, actually. 


Anyway it's O/T for punctuated gravity, but I just want to give a little "fast forward" to the filthy impure compromise solution that's probably the ultimate winner (at least in certain space habitat niches). Carry on.

[Greg Hullender]

Rotating habitats are high on my list of technologies that I wish had more research funding. There are all kind of questions we needs answers to, including coping with instability, finding out how much gravity is really needed for long-term health and for reproduction, and how much Coriolis force people can handle without getting sick. There are clever ground-based experiments that give us some ideas, but we won't really know most of these until some experiments can be done in space.

[Twark_Main]

Rotating habitats are high on my list of technologies that I wish had more research funding. There are all kind of questions we needs answers to, including coping with instability, finding out how much gravity is really needed for long-term health and for reproduction, and how much Coriolis force people can handle without getting sick. There are clever ground-based experiments that give us some ideas, but we won't really know most of these until some experiments can be done in space.

I don't think anyone would argue with more funding.

But we should be clear — and I'm sure you understand this, but for the benefit of others — when we utter the requirement "without being sick," after it passes through the lens of real-world economics, it comes out the other side as "with you getting a little (non-zero amount of) sick, but not sick enough that the cost so incurred is greater than the cost of further reducing Coriolis forces."

We shouldn't expect perfection. We shouldn't expect utopia. We should expect a compromise solution that minimizes total cost.

[mikelepage]

after humans get over our initial infragravity phobia

What a bizarre comment.

If you have any sort of argument, then please do make it.

The phobia I mention is very real, and it's on full display whenever the subject comes up here. Edzieba and his stealthily-made assumption above that "my eyeballs must need extra countermeasures for anything less than 99.9% gravity" is one example.  I think it's highly telling that his reply wasn't something like "hey I think you need 60% gravity for eyeballs instead of 50%," it was just an automatic freak-out absurd strawman the moment he saw anything lower than 1g. 

Last I checked the fluid effects are mitigated even at "merely" Mars gravity. By setting my error bars up to 50% I was being generous, actually. 


Anyway it's O/T for punctuated gravity, but I just want to give a little "fast forward" to the filthy impure compromise solution that's probably the ultimate winner (at least in certain space habitat niches). Carry on.

Geez Twark, if you want people to give you credit for having nuanced thinking, you might give the same courtesy to others instead of being so quick to dismiss it as faith or phobia. The rationale for arguing for full gravity becomes clear through study of molecular biology or other biological sciences. Even the simplest bacterial cell is - objectively - many orders of magnitude more complex than any machine ever devised. When a complex system is in an equilibrium state, and is demonstrably prone to chaotic, emergent behaviour when pushed out of that state, it's not a leap of faith or phobia to make "let's just keep it in that state" your default hypothesis.

One can argue that a full 100% of G might be best whilst also accepting the economic rationale that partial-G spin gravity demonstrators will be more cost-effective in the near term. That said, I won't be surprised if the "most effective G level" - all costs considered - is a lot closer to 100% of G than most on this forum would believe or hope for.

I personally think AG systems will bifurcate into two or more G level optimisations: 1) mission/sortie-level gravity (which would be very convenient if it turned out to be around Mars G), suitable for keeping fully-grown adults comfortable and healthy for many years at a time, and 2) generational-level gravity, (probably much closer to 100% of G if not exactly 1x G), suitable for pregnancy & proper physical development of children. Like salmon returning to freshwater to spawn, I expect people will have to commute back to full (or near-full) 100% of G for many generations to come. Evolution is usually slow like that.

It makes sense to focus on the the mission/sortie level gravity spacecraft first though, for biomedical reasons, for critical equipment R&D reasons, and also for commercial/tourism reasons, so in the near-term I'll continue to argue for focussing on Mars-G level platforms in LEO.

[Twark_Main]

Geez Twark, if you want people to give you credit for having nuanced thinking, you might give the same courtesy to others instead of being so quick to dismiss it as faith or phobia. The rationale for arguing for full gravity becomes clear through study of molecular biology or other biological sciences. Even the simplest bacterial cell is - objectively - many orders of magnitude more complex than any machine ever devised. When a complex system is in an equilibrium state, and is demonstrably prone to chaotic, emergent behaviour when pushed out of that state, it's not a leap of faith or phobia to make "let's just keep it in that state" your default hypothesis.

Exactly, it's not a leap of faith. It's by definition phobia to make "zero risk or cost should be tolerable" the default. This design path is unlikely to be optimal because it's the most extremely conservative option along the entire design spectrum (see #8).

In around 1956 there were real scientific questions about whether cellular machinery would simply shut down in microgravity, and astronauts would spontaneously die. This risk was tested by launching various small animals on sounding rockets, and later on orbital flights.

There are biological impacts from spaceflight, but nowadays these are far better known than this chaos theory talk seems to suggest.

I personally think AG systems will bifurcate into two or more G level optimisations: 1) mission/sortie-level gravity (which would be very convenient if it turned out to be around Mars G), suitable for keeping fully-grown adults comfortable and healthy for many years at a time, and 2) generational-level gravity, (probably much closer to 100% of G if not exactly 1x G), suitable for pregnancy & proper physical development of children. Like salmon returning to freshwater to spawn, I expect people will have to commute back to full (or near-full) 100% of G

I actually agree with your conclusion, even if we may disagree on theory.  The total cost of motion sickness (in terms of lost business) is vastly greater on a 1,000-room LEO space hotel serving 200,000+ guests annually, as compared to a crew of 9 serving an 18-month maintenance deployment interval.

[edzieba]

It's by definition phobia to make "zero risk or cost should be tolerable" the default.

That's not 'phobia', that's just best practice.

[Twark_Main]

We should be careful. "Best practice" is, in practice, most often used as a bizdev euphemism for "minimum acceptable practice."

It's by definition phobia to make "zero risk or cost should be tolerable" the default.

That's not 'phobia', that's just best practice.

"To timidly go..."   

Maybe this should be obvious, but it's only "best practice" if you find yourself in an extremely risk-intolerant mature industry, which of course many in the West are nowadays.  And even then, a company doesn't really target exactly zero risk. In practice they just buy down enough risk to be economical, and then use insurance (or externalization) to cover the remainder.


However that only addresses the "zero risk... should be tolerable" part you quoted. In practice, the part where you agree that "zero... cost should be tolerable" is much more problematic for doing any sort of engineering in the future. You're saying — whether you know it or not — that you shouldn't do an engineering tradeoff between the cost of accepting some minor AG discomfort vs the cost of oversizing your AG system. Per your "best practices," you must oversize your system every time.

You'd think someone's cousin has a business selling oversized AG systems...   


In short, "everything must be perfect and no compromise is acceptable" is a great motto for a religious extremist, but it's lousy for engineering.

[Twark_Main]

Unless by best practice you were referring to literally the best, ie luxury level accommodations.  In that case yes, you're going to pull out all the stop, and it will be priced to match!   

[edzieba]

We should be careful. "Best practice" is, in practice, most often used as a bizdev euphemism for "minimum acceptable practice."

It's by definition phobia to make "zero risk or cost should be tolerable" the default.

That's not 'phobia', that's just best practice.

"To timidly go..."   

Maybe this should be obvious, but it's only "best practice" if you find yourself in an extremely risk-intolerant mature industry, which of course many in the West are nowadays.  And even then, a company doesn't really target exactly zero risk. In practice they just buy down enough risk to be economical, and then use insurance (or externalization) to cover the remainder.


However that only addresses the "zero risk... should be tolerable" part you quoted. In practice, the part where you agree that "zero... cost should be tolerable" is much more problematic for doing any sort of engineering in the future. You're saying — whether you know it or not — that you shouldn't do an engineering tradeoff between the cost of accepting some minor AG discomfort vs the cost of oversizing your AG system. Per your "best practices," you must oversize your system every time.

You'd think someone's cousin has a business selling oversized AG systems...   


In short, "everything must be perfect and no compromise is acceptable" is a great motto for a religious extremist, but it's lousy for engineering.

That's a lot of straw-manning there.

'Best practice' means starting from a known-good state (9.81ms^2 acceleration with head-to-toe differential acceleration within known-good ranges from prior human studies) and working to expand the envelope from there, rather than assuming the known-good state is nonviable - for no particular reason other than "it might be expensive I guess, but no point actually trying" - and scattershotting random ideas to see if anything sticks.

[Greg Hullender]

'Best practice' means starting from a known-good state (9.81ms^2 acceleration with head-to-toe differential acceleration within known-good ranges from prior human studies) and working to expand the envelope from there, rather than assuming the known-good state is nonviable - for no particular reason other than "it might be expensive I guess, but no point actually trying" - and scattershotting random ideas to see if anything sticks.

We also have lots of data about zero-g, which is short-term good but medium-term bad. Because we're looking at sending missions to Mars, it makes a great deal of sense to prioritize testing 1/3 g habitats. If there are long-term problems at 1/3 g, the sooner we know that the better.

I do think we can all agree that 1/3 g should be better than zero-g, right? (Assuming the Coriolis force isn't terrible.)

[Paul451]

Pushing back towards the topic:

Does anyone know of any research (presumably animal research), that has tested for any benefits from "preloading" adaptation to hypergravity before a flight on Skylab/STS/MIR/ISS?

Example protocol: Throw batches of mice/fish/insects/whatever into a >1g centrifuge for 1, 2, 4 weeks before launch, along with a non-centrifuged control group. Fly all four groups to a space-station (or Shuttle "lab" mission), for a stay in micro-g, then return to Earth for comparison. Does "preloading" produce protection against micro-g-adaptation damage? Does it delay onset of micro-g damage? If either/both, does increases preloading time increase the protection/delay? Or does adaptation to higher-g just make adaptation to micro-g worse?

[Lampyridae]

One can argue that a full 100% of G might be best whilst also accepting the economic rationale that partial-G spin gravity demonstrators will be more cost-effective in the near term. That said, I won't be surprised if the "most effective G level" - all costs considered - is a lot closer to 100% of G than most on this forum would believe or hope for.

I personally think AG systems will bifurcate into two or more G level optimisations: 1) mission/sortie-level gravity (which would be very convenient if it turned out to be around Mars G), suitable for keeping fully-grown adults comfortable and healthy for many years at a time, and 2) generational-level gravity, (probably much closer to 100% of G if not exactly 1x G), suitable for pregnancy & proper physical development of children. Like salmon returning to freshwater to spawn, I expect people will have to commute back to full (or near-full) 100% of G for many generations to come. Evolution is usually slow like that.

It makes sense to focus on the the mission/sortie level gravity spacecraft first though, for biomedical reasons, for critical equipment R&D reasons, and also for commercial/tourism reasons, so in the near-term I'll continue to argue for focussing on Mars-G level platforms in LEO.

Instead of a linear curve, it's looking like a collection of peaks and troughs that are all over the place. It's exceedingly complex.

T cells respond within 20s to altered gravity by altering their gene activations.

A study using a random positioning machine to mimic microgravity, Moon and Mars gravity, plus irradiation (X-ray and/or carbon ion) showed wildly different results. They measured levels of IL-2, a key "alarm signal" protein for the immune system to respond to infection, as well as its genetic activation (ie its production capability) in T cells.

Without irradiation, the Moon showed less IL-2 gene activation than Mars. Weirdly, Moon and microgravity were shown as protective against X-rays compared to 1g. (The 1µM refers to the addition of 1µM of hydrocortisol as a simulation of stress)

edit: link and reference
https://www.mdpi.com/1422-0067/24/23/16943

Miranda S, Vermeesen R, Radstake WE, Parisi A, Ivanova A, Baatout S, Tabury K, Baselet B. Lost in Space? Unmasking the T Cell Reaction to Simulated Space Stressors. International Journal of Molecular Sciences. 2023; 24(23):16943. https://doi.org/10.3390/ijms242316943

[Lampyridae]

Pushing back towards the topic:

Does anyone know of any research (presumably animal research), that has tested for any benefits from "preloading" adaptation to hypergravity before a flight on Skylab/STS/MIR/ISS?

Example protocol: Throw batches of mice/fish/insects/whatever into a >1g centrifuge for 1, 2, 4 weeks before launch, along with a non-centrifuged control group. Fly all four groups to a space-station (or Shuttle "lab" mission), for a stay in micro-g, then return to Earth for comparison. Does "preloading" produce protection against micro-g-adaptation damage? Does it delay onset of micro-g damage? If either/both, does increases preloading time increase the protection/delay? Or does adaptation to higher-g just make adaptation to micro-g worse?

I do recall that there is research looking at rebound after long-term hypergravity exposure which seems to mimic micro- or partial gravity effects somewhat. In other words, it would just make the situation worse. Cellular adaptation to different g-loads happens within minutes, so that side of things wouldn't benefit. You effectively always get hyper-g loading before a transition to micro-g. (This might explain some short-term quirks of space adaptation)

[StraumliBlight]

NASA have put out a Request for Information for SpinSat.

SpinSat is a comprehensive and flexible approach to Mars-relevant science & technology development activities.

Goal: Develop beyond-LEO multi-payload platform to provide transit-to-Mars and Mars-surface gravity-plus-radiation environments for science experiments, model validation, technology development, & risk reduction. Objectives include:

Frequent access to Mars-relevant (BLEO) space via a launch-vehicle-and orbit-agnostic platform
Use of “cubesat standard” interfaces enabling broad participation in experiments by academics, commercials, and OGA

[Paul451]

Cool.

(Though more on-topic in the Testbeds thread.)

[Twark_Main]

We should be careful. "Best practice" is, in practice, most often used as a bizdev euphemism for "minimum acceptable practice."

It's by definition phobia to make "zero risk or cost should be tolerable" the default.

That's not 'phobia', that's just best practice.

"To timidly go..."   

Maybe this should be obvious, but it's only "best practice" if you find yourself in an extremely risk-intolerant mature industry, which of course many in the West are nowadays.  And even then, a company doesn't really target exactly zero risk. In practice they just buy down enough risk to be economical, and then use insurance (or externalization) to cover the remainder.


However that only addresses the "zero risk... should be tolerable" part you quoted. In practice, the part where you agree that "zero... cost should be tolerable" is much more problematic for doing any sort of engineering in the future. You're saying — whether you know it or not — that you shouldn't do an engineering tradeoff between the cost of accepting some minor AG discomfort vs the cost of oversizing your AG system. Per your "best practices," you must oversize your system every time.

You'd think someone's cousin has a business selling oversized AG systems...   


In short, "everything must be perfect and no compromise is acceptable" is a great motto for a religious extremist, but it's lousy for engineering.

That's a lot of straw-manning there.

"Straw-manning is a synonym for miscommunication, except now it's your fault." 

Maybe consider the possibility that you are not fully understanding the other person's point,  Has the concept ever once had cause to cross your mind?  Or were you too busy reaching for your book "Debate Words For People Who Are Super Popular At Parties"? 

'Best practice' means starting from a known-good state (9.81ms^2 acceleration with head-to-toe differential acceleration within known-good ranges from prior human studies) and working to expand the envelope from there

Again, this is really "most timid practices." So it is indeed "best" in extremely risk-intolerant environments.  You're half right!

If the US with its current old guard is the leader in space, I do expect the field will remain extremely (paralyzingly?) risk intolerant. However it's a self-correcting problem, because it means we won't be the leader for long. 



Anyway, real space programs have proven to be far more risk tolerant than this thread would have you believe. Did you know they've sometimes been operating with (gasp!) no artificial gravity at all??  The horror!!!

(in case it isn't obvious, what I'm saying is that your ultra-conservative risk posture in this thread is an extreme extreme outlier back in the real world)

rather than assuming the known-good state is nonviable - for no particular reason other than "it might be expensive I guess, but no point actually trying" - and scattershotting random ideas to see if anything sticks.

We seem to be talking about two different, but related, things.

You're talking about the process. "How do you get there from here?" You imagine a maximally timid path sure, but at least there's some arguable justification.

I'm talking about the result. "Where will we eventually end up?" We don't pressurize planes to 0 feet MSL (or even 640 feet MSL, the average altitude where people live). By pressurizing cabins at 6000-8000 feet we trade off some discomfort for reduced operating cost. To do otherwise would be economically irrational.

The idea that at the end of the process we will eventually end up at exactly 1 G (not even 90%, etc) is rather unlikely, regardless of whether you follow the reasoning.   

[Paul451]

Maybe consider the possibility that you are not fully understanding the other person's point,  Has the concept ever once had cause to cross your mind?  Or were you too busy reaching for your book "Debate Words For People Who Are Super Popular At Parties"? 

Is all this relevant to whether or not there's a benefit from punctuated gravity using a centrifuge?