Author Topic: Artificial Gravity Testbeds  (Read 41637 times)

Online Coastal Ron

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Artificial Gravity Testbeds
« on: 05/04/2019 08:30 pm »
As we move humanity out into space we will need a variety of artificial gravity systems. The two most prominent are artificial gravity spaceships and artificial gravity space stations, but before we build operational versions of those we may need testbeds to validate our assumptions.

We have a topic thread for "Realistic, near-term, rotating Space Station", and a new one for "Rotating Spaceship Concepts". This one will be dedicated to testbeds that we can use to prove out the technology and techniques necessary to building artificial gravity spaceships and space stations.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Online Coastal Ron

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Re: Artificial Gravity Testbeds
« Reply #1 on: 05/04/2019 08:49 pm »
A concept I've been working on is to build a rotating testbed that can be used to validate that micro-gravity space stations and spaceships will actually provide a benefit to humans when they are in space for long durations. We assume artificial gravity can provide some benefit, but we will need to understand what the minimum will be to provide an identifiable benefit.

The design I've been working on is like a giant "X" that spins, and it was designed to be built using existing and near-term reusable launchers. This proposed testbed would provide a maximum of Mars-level gravity at the ends furthest from the center of rotation, and lesser amounts of gravity as you move towards the center of rotation.

Each arm could be occupied, but I'm thinking some of the space would be needed for power equipment, environmental equipment, water and air storage, food and equipment storage, etc. So in reality two opposing arms would likely be occupied, with the crew spending most of their time there for purposes of the research.

In the picture below the green cylinder is a cargo pod that is moving towards the center of rotation of the testbed to dock. Not shown is a docking system that compensates for off-center rotation. The cargo pod is 5m in diameter and 10m in length.
« Last Edit: 03/17/2020 11:22 pm by Coastal Ron »
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline HMXHMX

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Re: Artificial Gravity Testbeds
« Reply #2 on: 05/04/2019 09:30 pm »
I"ll throw this into the mix, but – fair warning – I may not be able to check into this thread very often.

Offline sanman

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Re: Artificial Gravity Testbeds
« Reply #3 on: 05/04/2019 10:33 pm »
Is one of the requirements for the testbed that it demonstrate some actual human/vertebrate habitation?

Otherwise, what other things need to be demonstrated in space that can't be demonstrated on Earth?

Online Coastal Ron

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Re: Artificial Gravity Testbeds
« Reply #4 on: 05/04/2019 10:38 pm »
Is one of the requirements for the testbed that it demonstrate some actual human/vertebrate habitation?

Otherwise, what other things need to be demonstrated in space that can't be demonstrated on Earth?

No specific requirements, other than the testbed trying to determine an answer to a question, or to validate a theory.

As to demonstrating things on Earth, while you could do testing of components on Earth, validating that they perform the same on a rotating space station would be important before you design a rotating spaceship or space station that depends on those components.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Online Coastal Ron

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Re: Artificial Gravity Testbeds
« Reply #5 on: 05/04/2019 10:44 pm »
I"ll throw this into the mix, but – fair warning – I may not be able to check into this thread very often.

I think you have shown this previously, and this is the type of design that I started out with originally. I went from the "I" configuration to the "X" configuration in order to deal with the "intermediate axis theorem" issues, but there may be ways to deal with it using active measures (i.e. thrusters for instance).

And this type of configuration is a very simple design, and doesn't have the issues related to using cables to connect two free flying bodies. Plus it would lend itself to being built fairly quickly, and the cost of the modules would be kept low due to their common configuration. Lots to like about it.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline HMXHMX

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Re: Artificial Gravity Testbeds
« Reply #6 on: 05/04/2019 11:52 pm »
I"ll throw this into the mix, but – fair warning – I may not be able to check into this thread very often.

I think you have shown this previously, and this is the type of design that I started out with originally. I went from the "I" configuration to the "X" configuration in order to deal with the "intermediate axis theorem" issues, but there may be ways to deal with it using active measures (i.e. thrusters for instance).

And this type of configuration is a very simple design, and doesn't have the issues related to using cables to connect two free flying bodies. Plus it would lend itself to being built fairly quickly, and the cost of the modules would be kept low due to their common configuration. Lots to like about it.

Thanks.  I haven't fully got my head around that effect (no time to ponder the issue, unfortunately).  The problem with four arms vs. two is obviously that we double the launch cost.  Hopefully there are other less expensive solutions though growing to four arms is certainly to be desired for other reasons.

Offline sanman

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Re: Artificial Gravity Testbeds
« Reply #7 on: 05/06/2019 12:40 am »
How about a conventional-looking roughly cylindrical section (since that's what existing launch vehicle payload bays look like), which has the ability to alter its geometry once it arrives in space?

Maybe it could open up like a clamshell or pocketknife, by being hinged at one end of the cylinder. Once that swivel was fully completed and the structure fully extended/unfolded into the final shape, then the hinge would lock.

Or what if you started out with a cylinder shape that had an accordion section in the middle? Once in space, the accordion section would expand to increase the separation distance between the sections on either end of it.

Is it possible to imagine mechanical actuations like these, which would somehow still allow a single contiguous volume across the entire structure, spanning across both sides of the actuated joints?

Online Coastal Ron

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Re: Artificial Gravity Testbeds
« Reply #8 on: 05/11/2019 02:36 am »
...Is it possible to imagine mechanical actuations like these, which would somehow still allow a single contiguous volume across the entire structure, spanning across both sides of the actuated joints?

I've seen many such assemblies proposed, including designs that unfolded that were proposed by NASA back in the 60's.

Lots of mechanical designs are possible. Normally you start with a goal for the testbed, then figure out how it can be built. However if there are existing systems that can be cobbled together, and some form of experimentation can still be done, then that might be a better approach.

The design I proposed above relies on modules that can be mass produced, transported to space using the New Glenn, and be assembled without major construction needs. And because the design allows for docking, it could run micro-gravity experiments for quite a long time. However the design is not optimal for being a space station due to the lack of work space, which is why I put it in the testbed section.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline punder

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Re: Artificial Gravity Testbeds
« Reply #9 on: 05/11/2019 08:43 pm »
The SSI design looks great to me, and the author is one of my NewSpace heros from way back.  :)

I have always advocated variable-g research, even though (most of) our betters at NASA have studiously ignored the idea (among many others that seem like no-brainers...). Engineering is so much easier and quicker than medical research, especially in the context of spaceflight. Look how long it takes to develop and approve drugs and therapies on Earth, with practically unlimited facilities available. How long will it take to develop therapies to combat the effects of microgravity on the ISS? Practically forever is a good guess.

The problem is that we are in a period of time where it might take just as long to field such a facility as it will to establish a crewed lunar base, with a Mars base following in relatively short order. Soon we will may have real data on two unfamiliar intermediate g-levels, simply as a byproduct of NASA and SpaceX ambitions. Those are enough for a curve. It's true a variable-g facility could complete that curve in detail.

I already know Coastal Ron thinks me silly for saying this!  ;D  But I'm firmly of the opinion that a variable-g facility on the Moon or Mars is more likely now than an orbital one. Because humans are absolutely at home working in g, and designing stuff to work in g. A centrifuge is a deeply known thing. So is a banked track or rail for a rolling vehicle. Either concept works for generating arbitrary levels of g above local gravity.

Rotating space stations will happen, then habitats... but early research to establish lowest effective g and highest acceptable spin can be done on the Moon or Mars, with (relatively) conventional engineering.

Offline Eer

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Re: Artificial Gravity Testbeds
« Reply #10 on: 05/11/2019 10:24 pm »
I don’t agree that variable G artificial gravity will first appear on some surface. Things have changed. We’re seeing relatively heavy sheets of stainless steel being welded together on what amounts to a seaside beach I open air. They’re being used to assemble a super heavyweight reusable launcher.

Whether you subscribe to the notion that these heavy lift ships themselves would make good building blocks for an orbital spinning research facility or not, the lift capacity and, cubic volume capacity, and ready research into orbital welding, 3D printing, and robotic operations makes larger, more robust construction more possible and less expensive.

Outfitting with life support, workable docking facilities and so forth leave plenty of new Engineering yet to be done. But optimization objectives have changed.

In my opinion.
From "The Rhetoric of Interstellar Flight", by Paul Gilster, March 10, 2011: We’ll build a future in space one dogged step at a time, and when asked how long humanity will struggle before reaching the stars, we’ll respond, “As long as it takes.”

Offline punder

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Re: Artificial Gravity Testbeds
« Reply #11 on: 05/11/2019 11:02 pm »
I don’t agree that variable G artificial gravity will first appear on some surface. Things have changed. We’re seeing relatively heavy sheets of stainless steel being welded together on what amounts to a seaside beach I open air. They’re being used to assemble a super heavyweight reusable launcher.

Whether you subscribe to the notion that these heavy lift ships themselves would make good building blocks for an orbital spinning research facility or not, the lift capacity and, cubic volume capacity, and ready research into orbital welding, 3D printing, and robotic operations makes larger, more robust construction more possible and less expensive.

Outfitting with life support, workable docking facilities and so forth leave plenty of new Engineering yet to be done. But optimization objectives have changed.

In my opinion.

Two Starships docked nose-to-nose, or with some other structure between them for larger radius, would indeed make a good testbed. The thing is (imho) Musk isn't going to bother. The whole point of Starship is to go straight to the real thing, as fast as possible. He will get the data as a matter of course. NASA doesn't have the time or resources to reach their existing goals, much less pursue research they've historically ignored. Given Bezos' interest in space habitats, BO is the most likely player to go for it, but given their pace and current priorities, all the data will be available long before they get there.

Offline spacenut

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Re: Artificial Gravity Testbeds
« Reply #12 on: 05/11/2019 11:20 pm »
Each of the modules on the X could have solar panels attach that would extend to provide power for the station.  Kind of like Dragon I service module or Soyuz.  Don't know why ISS didn't do something like this. 

Offline Joseph Peterson

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Re: Artificial Gravity Testbeds
« Reply #13 on: 05/12/2019 03:28 am »
One testbed I would like to see in a milligravity research facility.  A facility that can support research between 0 and 30 milli-Gs purpose is to test hardware to be used on Ceres, asteroids, comets, and small moons.

The other testbed I would like to see determines things like maximum spin rates and minimum acceptable gravity.  The purpose is to determine the minimum required radius.

The end goal is learning how to build minimal mass deep space artificial gravity ships that can conduct multiyear missions.

Offline Shevek23

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Re: Artificial Gravity Testbeds
« Reply #14 on: 11/22/2019 05:15 am »
....
Whether you subscribe to the notion that these heavy lift ships themselves would make good building blocks for an orbital spinning research facility or not, the lift capacity and, cubic volume capacity, and ready research into orbital welding, 3D printing, and robotic operations makes larger, more robust construction more possible and less expensive.

Outfitting with life support, workable docking facilities and so forth leave plenty of new Engineering yet to be done. But optimization objectives have changed.

In my opinion.

Two Starships docked nose-to-nose, or with some other structure between them for larger radius, would indeed make a good testbed. The thing is (imho) Musk isn't going to bother. The whole point of Starship is to go straight to the real thing, as fast as possible. He will get the data as a matter of course. NASA doesn't have the time or resources to reach their existing goals, much less pursue research they've historically ignored. Given Bezos' interest in space habitats, BO is the most likely player to go for it, but given their pace and current priorities, all the data will be available long before they get there.

I don't think SpaceX is going to divert themselves to such projects, no, though recent medical news
https://forum.nasaspaceflight.com/index.php?topic=49470.msg2017452;topicseen#new
underscores we actually don't know nearly as much about space medicine, including effects of free fall even, which we do have data on but evidently not nearly enough even so, and nothing whatsoever about low gravity as on Luna or Mars. This might cause the company to quite suddenly, in classic fashion, go all in on it.

But if another agency, governmental, private, or some consortium of universities or what have you, could scrape up the budget, I don't think SpaceX would resist the idea of this customer purchasing two or three or five Starship hulls and ordering customization of them. They won't divert budget to it gratis, but if someone pays them that someone can order up whatever modifications they like, subject to regulations, I would think.

If such modules are in fact repurposed to be permanent test station units, it would be possible to simply remove all the Raptor engines, and return them to Earth (or keep them stored somewhere in orbit as spares); as Raptor production is currently a pacing item, offering to buy the hull but merely lease the Raptors for one launch and return them to SpaceX might sweeten the deal for the company considerably.

Offline WH2OPaddler

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Re: Artificial Gravity Testbeds
« Reply #15 on: 02/11/2020 08:20 pm »
The pieces of an Artificial Gravity Testbed will, in all likelihood, be flying by the end of 2020. All that's needed is for people to recognize it as such. In my view, the test bed needed to study artificial gravity will be created every time a Starship and a Tanker are mated. In Elon speak: "The best part is no part, and the best process is no process." It follows, from that prospective, that if people can get past the 180° flip in Up & Down that will take place when the paired vehicles are spun (which I’ll comment on later), the advantages of using existing vehicles, mechanisms, and mating techniques will become evident.


SpaceX is already planning for an around-the-moon mission in 2023, a mission that cannot happen until in-orbit refueling is perfected. That means that the major components of an Artificial Gravity Testbed are already on the books. These include: a ship with all necessary life support equipment already included; repeatable rendezvous and tail-to-tail docking procedures; designs for the latching mechanisms that will secure Tankers to both Starships and Cargo carriers; and a far-reaching test program for transfer of propellants on-orbit. These developments constitute the vast majority of efforts needed to create an Artificial Gravity Testbed. Note that as a consequence of spinning joined pairs of Tankers and Starships, SpaceX will be able to utilize the acceleration created to settle propellants to the tops of their respective tanks. Once initiated, the spin-created artificial gravity will dispense with the need for the long-axis thruster firings that will otherwise be required. Eliminate those thruster firings, and you also eliminate the perturbations to orbital parameters that will otherwise need to be compensated for.

The Artificial Gravity Testbed is, in this view, a natural consequence of Starship development. Medically relevant studies of the effects of artificial gravity will likely require use of dedicated vehicles, flight-worthy ships that have been obsoleted by revision, for instance. Due to the flight durations required – months at least – research into the effectiveness of artificial gravity will likely be performed under the auspices of NASA and/or other space agencies.

And now to the 800-pound gorilla in the room: the 180° shift in direction from earth-bound gravity to spin-actuated gravity. Some people will view the need to move furnishings, workstations, and all the other accoutrements from 'floor' to 'ceiling', and back again, as an insurmountable problem. I do not. Interior designers have been crafting small, tight, and odd shaped living and working quarters for literally centuries. And they did that with paper and pencils! With the CAD environment available today, I have no doubt whatever that any of a vast number of interior design houses would jump at the chance to design the staterooms that would occupy the interiors of the first interplanetary spaceships. What doing so will take is a change in perspective and a healthy dose of Imagineering.

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Re: Artificial Gravity Testbeds
« Reply #16 on: 02/12/2020 01:07 am »
Note that as a consequence of spinning joined pairs of Tankers and Starships, SpaceX will be able to utilize the acceleration created to settle propellants to the tops of their respective tanks. Once initiated, the spin-created artificial gravity will dispense with the need for the long-axis thruster firings that will otherwise be required. Eliminate those thruster firings, and you also eliminate the perturbations to orbital parameters that will otherwise need to be compensated for.

I presume that the thruster firings will do double duty as orbit-raising burns, so little fuel is actually wasted. Presumably this would be an apogee raise burn, to maintain a low perigee and maximize the Oberth effect. Far from needing to be "compensated for," the burns are instead doing useful work.

And now to the 800-pound gorilla in the room: the 180° shift in direction from earth-bound gravity to spin-actuated gravity. Some people will view the need to move furnishings, workstations, and all the other accoutrements from 'floor' to 'ceiling', and back again, as an insurmountable problem. I do not. Interior designers have been crafting small, tight, and odd shaped living and working quarters for literally centuries. And they did that with paper and pencils! With the CAD environment available today, I have no doubt whatever that any of a vast number of interior design houses would jump at the chance to design the staterooms that would occupy the interiors of the first interplanetary spaceships. What doing so will take is a change in perspective and a healthy dose of Imagineering.

Of course it's possible, but nevertheless this additional constraint will mean the design will be worse vs what those same clever, CAD-equipped Imagineers could produce if saddled with fewer constraints.
« Last Edit: 02/12/2020 01:09 am by Twark_Main »

Offline edzieba

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Re: Artificial Gravity Testbeds
« Reply #17 on: 02/12/2020 10:47 am »
Some people will view the need to move furnishings, workstations, and all the other accoutrements from 'floor' to 'ceiling', and back again, as an insurmountable problem. I do not. Interior designers have been crafting small, tight, and odd shaped living and working quarters for literally centuries. And they did that with paper and pencils! With the CAD environment available today, I have no doubt whatever that any of a vast number of interior design houses would jump at the chance to design the staterooms that would occupy the interiors of the first interplanetary spaceships. What doing so will take is a change in perspective and a healthy dose of Imagineering.
Moving furniture is not the concern. A complete flip of load path is the issue. Starship has been designed to be either within a 1g field in one orientation, in a 0.376g field in that same orientation, in microgravity, or under very small acceleration from RCS thruster firings. Not only static structural loads, but things like plumbing (vapour locks now in the nadir rather than apex), load surfaces, etc. The same applies to a Starship on its side rather than inverted.
Think of a building: works very well indeed right side up, but if you were to glue all the furniture to the ceiling then flip the building upside down (or glue it to the wall and put it on its side) you would have a very bad time indeed. Same problem as with satellites designed for vertical integration.

Offline Paul451

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Re: Artificial Gravity Testbeds
« Reply #18 on: 02/12/2020 06:18 pm »
Moving furniture is not the concern. A complete flip of load path is the issue. Starship has been designed to be either within a 1g field in one orientation, in a 0.376g field in that same orientation, in microgravity, or under very small acceleration from RCS thruster firings.

And vertical at 3+g. And the reverse-direction jerk-force of 3g to 0g. And horizontally, belly-side, at however many g's it pulls during re-entry, plus the bending force from aerodynamic pressure in that horizontal position. Also, if they stick with the crane idea to lift it onto Super Heavy, then the structure will also need to support the loaded-but-unfuelled mass hanging from the nose.

It needs to be quite robust in several orientations.

but if you were to glue all the furniture

"Doctor, it hurts when I do this!"
« Last Edit: 02/12/2020 06:20 pm by Paul451 »

Offline edzieba

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Re: Artificial Gravity Testbeds
« Reply #19 on: 02/13/2020 11:33 am »
And vertical at 3+g. And the reverse-direction jerk-force of 3g to 0g. And horizontally, belly-side, at however many g's it pulls during re-entry, plus the bending force from aerodynamic pressure in that horizontal position.
Re-entry loads are spread across the entire heatshield surface. If you want to lift (or 'hang', for spin-gravity) in the same orientation, either you need to bring up a Starship-sized cradle or strengthen the structure for point-loading.
Quote
Also, if they stick with the crane idea to lift it onto Super Heavy, then the structure will also need to support the loaded-but-unfuelled mass hanging from the nose.
Hence all the suggestions to 'hang' it from the nose for spin-gravity. The lifting lugs are after all right there...

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