Author Topic: Maintaining health on a Mars-bound Starship  (Read 37509 times)

Offline Ionmars

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Re: Maintaining health on a Mars-bound Starship
« Reply #20 on: 09/19/2022 05:09 pm »
Why? Being actually docked makes them more susceptible to common failures. On explosion on one may damage both of them.

They could still occasionally meet up and hang out or exchange personnel.
Ships floating in tandem could bump against each other, but not if they are firmly docked together. As long term co-travelers, I believe this is safer.

In regards to exchanging personnel between ships, I think you have a different plan in mind. How would that look?


Offline Robotbeat

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Re: Maintaining health on a Mars-bound Starship
« Reply #21 on: 09/19/2022 05:15 pm »
Why? Being actually docked makes them more susceptible to common failures. On explosion on one may damage both of them.

They could still occasionally meet up and hang out or exchange personnel.
Ships floating in tandem could bump against each other, but not if they are firmly docked together. As long term co-travelers, I believe this is safer.


They wouldn’t be merely floating but spinning. No chance of accidental recontact if the cable is cut while spinning as they’d be flying in opposite directions compared to their center of mass.
« Last Edit: 09/19/2022 05:15 pm by Robotbeat »
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Offline Lampyridae

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Re: Maintaining health on a Mars-bound Starship
« Reply #22 on: 09/19/2022 06:21 pm »
Why? Being actually docked makes them more susceptible to common failures. On explosion on one may damage both of them.

They could still occasionally meet up and hang out or exchange personnel.
Ships floating in tandem could bump against each other, but not if they are firmly docked together. As long term co-travelers, I believe this is safer.


They wouldn’t be merely floating but spinning. No chance of accidental recontact if the cable is cut while spinning as they’d be flying in opposite directions compared to their center of mass.

A simple truss, basically attaching where the chopsticks hook under the forward flaps, could connect the two to spin baton (or nunchuck) style, engines outward. It would solve the problems you get with tethers in space snapping around, wobbling etc. Assemble from a kit in the orbital staging area, maybe it has some solar panels for extra transit power. Discard before Mars interface.
« Last Edit: 09/19/2022 06:22 pm by Lampyridae »

Offline Greg Hullender

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Re: Maintaining health on a Mars-bound Starship
« Reply #23 on: 09/19/2022 06:25 pm »
No, I mean send a depot by itself to Mars leave it there. Then use it for all return traffic from Mars. That might make sense, e.g. if you were sending very heavy loads back for some reason. (I thought, though, that a fully fueled Starship could go from Mars surface back to Earth orbit without needing extra fuel. Did I imagine that?)

But, even so, that's one depot in LEO and one depot in LMO. Maybe two each for redundancy. But I don't see the value in sending a depot there and back with every starship. Not for refueling purposes, anyway.

Offline Ionmars

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Re: Maintaining health on a Mars-bound Starship
« Reply #24 on: 09/19/2022 08:07 pm »
,,,
A simple truss, basically attaching where the chopsticks hook under the forward flaps, could connect the two to spin baton (or nunchuck) style, engines outward. It would solve the problems you get with tethers in space snapping around, wobbling etc. Assemble from a kit in the orbital staging area, maybe it has some solar panels for extra transit power. Discard before Mars interface.
A simple truss to rigidly join two ships sounds like a step in the right direction.

But if you join them at their noses with engines outward, you loose the advantage of distance between the crew and the far end of the other ship. With crew closer to the center of rotation you must spin faster to get the same effective g-force and with more coriolis effect.

Offline Ionmars

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Re: Maintaining health on a Mars-bound Starship
« Reply #25 on: 09/19/2022 08:16 pm »
No, I mean send a depot by itself to Mars leave it there. Then use it for all return traffic from Mars. That might make sense, e.g. if you were sending very heavy loads back for some reason. (I thought, though, that a fully fueled Starship could go from Mars surface back to Earth orbit without needing extra fuel. Did I imagine that?)

But, even so, that's one depot in LEO and one depot in LMO. Maybe two each for redundancy. But I don't see the value in sending a depot there and back with every starship. Not for refueling purposes, anyway.
ISTM your approach would work just fine.

 I was aiming to kill two birds with one stone. First, you need a counterweight to balance a rotating crew ship to Mars. When preparing for a return trip to Earth you will need an accumulator in LMO in the same way you would employ one in LEO. The same accumulator ship can perform both roles.

Offline Coastal Ron

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Re: Maintaining health on a Mars-bound Starship
« Reply #26 on: 09/19/2022 08:24 pm »
One way to accommodate gravity reversals is to design a gravity couch that can adjust to both takeoff and artificial gravity during transit. A gravity couch that could be removed from the floor and latched onto the ceiling would meet this requirement. This couch could be incorporated into an arrangement of sleep/EDL cubicles inside one level of a multi-level crew cabin, as suggested by the sketch below.

This can't work because the center of rotation is not stable. Reference the intermediate axis theorem (aka tennis racket theorem).

Connecting the two Starships end-to-end creates a long cylinder. Any imbalance along the cylinder immediately starts a wobble, which quickly devolves into the two tips of the Starships rotating over each other - while the cylinder is still spinning on its original short axis. So you have rotations happening in two different dimensions at the same time, creating centripetal forces that are not what you want. Not good.

In the short term Elon Musk is assuming that humans will be able to get to surface of Mars quick enough before any zero-G issues arise. Long term if this turns out not to be the right strategy then I think we'll see some form of Mars cyclers being built that still can leverage the advantages of the Starship.
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 edzieba

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Re: Maintaining health on a Mars-bound Starship
« Reply #27 on: 09/20/2022 08:34 am »
One way to accommodate gravity reversals is to design a gravity couch that can adjust to both takeoff and artificial gravity during transit. A gravity couch that could be removed from the floor and latched onto the ceiling would meet this requirement. This couch could be incorporated into an arrangement of sleep/EDL cubicles inside one level of a multi-level crew cabin, as suggested by the sketch below.

This can't work because the center of rotation is not stable. Reference the intermediate axis theorem (aka tennis racket theorem).

Connecting the two Starships end-to-end creates a long cylinder. Any imbalance along the cylinder immediately starts a wobble, which quickly devolves into the two tips of the Starships rotating over each other - while the cylinder is still spinning on its original short axis. So you have rotations happening in two different dimensions at the same time, creating centripetal forces that are not what you want. Not good.

In the short term Elon Musk is assuming that humans will be able to get to surface of Mars quick enough before any zero-G issues arise. Long term if this turns out not to be the right strategy then I think we'll see some form of Mars cyclers being built that still can leverage the advantages of the Starship.
That's not how the intermediate axis theorem works. Simple (single cable) bola configurations have problems with oscillation modes (which can be resolved with additional cables and/or active damping, and reduces the problem down to cylinder bending modes), but there is no intermediate axis being spun about: there are two maxima axes and one minima, and you're spinning about one of the maximas. This is unlike the long-axis spin of an O-Neill Cylinder where any flexing can lead to axis change because you're spinning about the minima.

Offline mikelepage

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Re: Maintaining health on a Mars-bound Starship
« Reply #28 on: 09/20/2022 10:05 am »
Glad that you're keeping spin-G as an ongoing conversation, but I think as a general rule, we spin-G proponents need to make sure any spin-G design takes away as many constraints as it adds, so you're helping the SpaceX engineers solve problems they already have, not just adding new ones to the list. Otherwise Spin-G is never going to get any traction.

Does having a spin-G/cruise phase optimised ship help with harvesting solar energy? or is it better at thermal management? what about propellant cryo-cooling or transfer? Does having a dedicated spin-G ship allow you to *not* take space-optimised equipment down to Mars surface? (assuming it can aerobrake into Mars orbit).

I'm increasingly liking the idea of taking a dedicated spin-G starship (with very large solar arrays and radiators) for every n regular starships. So for example, you might have one spin-G starship for every 5 regular ships. The simple act of keeping the crew for each fleet mainly on the one ship during the transit, and that starship having large solar arrays to shield the rest of the fleet from solar heating in its shadow, allows you to keep all the other starships at fridge/freezer temperatures (or lower) during the transit, and that could mean you don't need dedicated cryo-coolers/large solar arrays/radiators on all those other starships. Without crew onboard for most of the cruise phase, the regular starships might be able to make do with whatever solar tiles can fit on the dorsal side of starship, similar to the trunk of Dragon 2.

The trick I think would be to have some large inflatable wing structure that would allow the specialised starship to aerobrake into orbit at both ends of the transit, plus having the extra flights to refuel the special starship prior to trans-Earth injection. 

I was aiming to kill two birds with one stone. First, you need a counterweight to balance a rotating crew ship to Mars. When preparing for a return trip to Earth you will need an accumulator in LMO in the same way you would employ one in LEO. The same accumulator ship can perform both roles.

Sorry but I don't think this is correct on either count. A single Starship spinning end over end (20-25m radius) will be long enough to keep spin rates at 4rpm or below for Mars equivalent G (not ideal of course, but sufficient). The issue (and ongoing argument across many of these threads) has been about having an internal structure that needs to be reconfigurable for zero-G, upside-down and right-way up operations. Having a dedicated cruise phase starship that would be able to just do nose down spin G helps this issue too.

Also, the idea of needing an accumulator in LMO is news to me(?) I thought the whole Starship architecture was elegant precisely because Mars-surface return to Earth surface was equivalent delta-V to that of the LEO-Mars surface leg.

Offline Ionmars

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Re: Maintaining health on a Mars-bound Starship
« Reply #29 on: 09/20/2022 11:24 am »
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 A single Starship spinning end over end (20-25m radius) will be long enough to keep spin rates at 4rpm or below for Mars equivalent G (not ideal of course, but sufficient). The issue (and ongoing argument across many of these threads) has been about having an internal structure that needs to be reconfigurable for zero-G, upside-down and right-way up operations. Having a dedicated cruise phase starship that would be able to just do nose down spin G helps this issue too.
Mike, I think you are correct. For the first few flights to Mars, early pioneers will have to put up with a higher rate of spin and its coriolis effects to achieve artificial gravity at 0.38g to Mars. Returning to Earth this way may be problematic for their health because they would not be in good shape to tolerate Earth 1.0g.

As far as I can tell, this is not a solved problem in either NASA or SpaceX quarters.

When we start getting paid passengers for the Mars trip it may be time to consider my approach to achieve a more comfortable and healthful passage.

Offline RamsesBic

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Re: Maintaining health on a Mars-bound Starship
« Reply #30 on: 09/20/2022 11:35 am »
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 A single Starship spinning end over end (20-25m radius) will be long enough to keep spin rates at 4rpm or below for Mars equivalent G (not ideal of course, but sufficient). The issue (and ongoing argument across many of these threads) has been about having an internal structure that needs to be reconfigurable for zero-G, upside-down and right-way up operations. Having a dedicated cruise phase starship that would be able to just do nose down spin G helps this issue too.
Mike, I think you are correct. For the first few flights to Mars, early pioneers will have to put up with a higher rate of spin and its coriolis effects to achieve artificial gravity at 0.38g to Mars. Returning to Earth this way may be problematic for their health because they would not be in good shape to tolerate Earth 1.0g.

As far as I can tell, this is not a solved problem in either NASA or SpaceX quarters.

When we start getting paid passengers for the Mars trip it may be time to consider my approach to achieve a more comfortable and healthful passage.

Has anyone shown what the effects of any gravity between 0 and 1g would do to the human body long term?
Are we building hypothetical ship designs on assumptions.

Offline Ionmars

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Re: Maintaining health on a Mars-bound Starship
« Reply #31 on: 09/20/2022 11:46 am »
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Has anyone shown what the effects of any gravity between 0 and 1g would do to the human body long term?
Are we building hypothetical ship designs on assumptions.
We have experience with missions at ISS in essentially zero gravity. Returning after 6 months astronauts are still alive, but not much more. We do not have experience at 0.38g, which is better than ISS but would be for longer duration, at least two years between synods. Some of these conditions are not feasible to simulate on Earth.

Offline Ionmars

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Re: Maintaining health on a Mars-bound Starship
« Reply #32 on: 09/20/2022 12:01 pm »
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This can't work because the center of rotation is not stable. Reference the intermediate axis theorem (aka tennis racket theorem).

Connecting the two Starships end-to-end creates a long cylinder. Any imbalance along the cylinder immediately starts a wobble, which quickly devolves into the two tips of the Starships rotating over each other - while the cylinder is still spinning on its original short axis. So you have rotations happening in two different dimensions at the same time, creating centripetal forces that are not what you want. Not good.

In the short term Elon Musk is assuming that humans will be able to get to surface of Mars quick enough before any zero-G issues arise. Long term if this turns out not to be the right strategy then I think we'll see some form of Mars cyclers being built that still can leverage the advantages of the Starship.

Thank you for pointing out the potential awkward gyrations that could occur with a dual rotating body. You referred to a nice article about the Intermediate Axis Theorem (Tennis Racket Theorem) from which I copied the first image below. 

From the article: “The (Intermediate Axis) theorem describes the following effect: rotation of an object around its first and third principal axes is stable, while rotation around its second principal axis (or intermediate axis) is not.” Referring to the sketch, this means that rotating bodies should rotate around axis ê1 or ê3 , but avoid spinning about secondary axis ê2. In the case of the tennis racket, avoiding this secondary rotation can be accomplished by turning the racket upward so that the plane across the racket head is vertical rather than horizontal. Then when the racket is flipped you don’t get that awkward double-turn.

The second image (rough sketch by me) shows similarities between a tennis racket and crew Starship. The plane across the ship and the fins is analogous to the plane across the head of a racket. To avoid secondary axis gyration, dual Starship should rotate about axis ê3 .

When you flip the tennis racket with the head vertical  you still get very uneven turning during the flip. This is because the racket head is not mass-balanced with the grip. Attaining mass balance between Starship and accumulator would be important for the comfort and health of crew and passengers. This is addressed in Reply #8 above.

Offline Robotbeat

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Re: Maintaining health on a Mars-bound Starship
« Reply #33 on: 09/20/2022 12:11 pm »
...
...
Has anyone shown what the effects of any gravity between 0 and 1g would do to the human body long term?
Are we building hypothetical ship designs on assumptions.
We have experience with missions at ISS in essentially zero gravity. Returning after 6 months astronauts are still alive, but not much more. We do not have experience at 0.38g, which is better than ISS but would be for longer duration, at least two years between synods. Some of these conditions are not feasible to simulate on Earth.
You exaggerate. Polyakov demonstrated 437 days and walked out of his Soyuz.
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Offline Lampyridae

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Re: Maintaining health on a Mars-bound Starship
« Reply #34 on: 09/20/2022 01:35 pm »
...
...
 A single Starship spinning end over end (20-25m radius) will be long enough to keep spin rates at 4rpm or below for Mars equivalent G (not ideal of course, but sufficient). The issue (and ongoing argument across many of these threads) has been about having an internal structure that needs to be reconfigurable for zero-G, upside-down and right-way up operations. Having a dedicated cruise phase starship that would be able to just do nose down spin G helps this issue too.
Mike, I think you are correct. For the first few flights to Mars, early pioneers will have to put up with a higher rate of spin and its coriolis effects to achieve artificial gravity at 0.38g to Mars. Returning to Earth this way may be problematic for their health because they would not be in good shape to tolerate Earth 1.0g.

As far as I can tell, this is not a solved problem in either NASA or SpaceX quarters.

When we start getting paid passengers for the Mars trip it may be time to consider my approach to achieve a more comfortable and healthful passage.

Has anyone shown what the effects of any gravity between 0 and 1g would do to the human body long term?
Are we building hypothetical ship designs on assumptions.


We have a handful of bed-rest studies, and partial weight-bearing studies in rodents. Generally, any g is better than no g.

Regarding short radius and coriolis forces, I found this video of Tim Peake doing an impromptu experiment and trying to make himself dizzy in space. He gets up to like 60RPM and feels virtually nothing.



So there is a question as to what level of low g this "benefit" emerges.

Offline RamsesBic

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Re: Maintaining health on a Mars-bound Starship
« Reply #35 on: 09/20/2022 01:44 pm »
...
...
Has anyone shown what the effects of any gravity between 0 and 1g would do to the human body long term?
Are we building hypothetical ship designs on assumptions.
We have experience with missions at ISS in essentially zero gravity. Returning after 6 months astronauts are still alive, but not much more. We do not have experience at 0.38g, which is better than ISS but would be for longer duration, at least two years between synods. Some of these conditions are not feasible to simulate on Earth.
You exaggerate. Polyakov demonstrated 437 days and walked out of his Soyuz.

Ask yourself for how long did he walk? Long enough to take some photos, or was it longer? It only proves he can endure a lot, that's all.

I was wondering if anyone did a test with humans living at say 0.3g for months then returning to 1g? To my knowledge no one has. Do we even know if 0.1 g is not enough to be fine after a few days adjusting?
I am astounded by the lack of any tests done during the last 50 years. It has only been 0g for all those years - and extrapolations.

Offline Lampyridae

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Re: Maintaining health on a Mars-bound Starship
« Reply #36 on: 09/20/2022 01:48 pm »
Ask yourself for how long did he walk? Long enough to take some photos, or was it longer? It only proves he can endure a lot, that's all.

I was wondering if anyone did a test with humans living at say 0.3g for months then returning to 1g? To my knowledge no one has. Do we even know if 0.1 g is not enough to be fine after a few days adjusting?
I am astounded by the lack of any tests done during the last 50 years. It has only been 0g for all those years - and extrapolations.

Polyakov is also a sample size of one. The eye damage is particularly serious and currently irreversible.

JAXA actually did some 1/6g experiments in their mouse habitat in 2020 but have never published any results. It's extremely frustrating.

Offline RamsesBic

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Re: Maintaining health on a Mars-bound Starship
« Reply #37 on: 09/20/2022 01:55 pm »
Ask yourself for how long did he walk? Long enough to take some photos, or was it longer? It only proves he can endure a lot, that's all.

I was wondering if anyone did a test with humans living at say 0.3g for months then returning to 1g? To my knowledge no one has. Do we even know if 0.1 g is not enough to be fine after a few days adjusting?
I am astounded by the lack of any tests done during the last 50 years. It has only been 0g for all those years - and extrapolations.

Polyakov is also a sample size of one. The eye damage is particularly serious and currently irreversible.

JAXA actually did some 1/6g experiments in their mouse habitat in 2020 but have never published any results. It's extremely frustrating.

I would love to find out if the eyes would be damaged at say 0.1g or not. Because we would really be in trouble if the eyes need 1g to avoid irreversible damage.

Offline Robotbeat

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Re: Maintaining health on a Mars-bound Starship
« Reply #38 on: 09/20/2022 02:00 pm »
Ask yourself for how long did he walk? Long enough to take some photos, or was it longer? It only proves he can endure a lot, that's all.

I was wondering if anyone did a test with humans living at say 0.3g for months then returning to 1g? To my knowledge no one has. Do we even know if 0.1 g is not enough to be fine after a few days adjusting?
I am astounded by the lack of any tests done during the last 50 years. It has only been 0g for all those years - and extrapolations.

Polyakov is also a sample size of one.
There have been a bunch of folk now who’ve done year-long stunts. And a sample size of one is all that’s needed for proof of concept.
Quote
The eye damage is particularly serious and currently irreversible.
Id like to see that latter claim. Sounds like a game telephone with conservative study findings.

Quote
JAXA actually did some 1/6g experiments in their mouse habitat in 2020 but have never published any results. It's extremely frustrating.
Seconded!
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline Greg Hullender

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Re: Maintaining health on a Mars-bound Starship
« Reply #39 on: 09/20/2022 02:34 pm »
I was wondering if anyone did a test with humans living at say 0.3g for months then returning to 1g? To my knowledge no one has. Do we even know if 0.1 g is not enough to be fine after a few days adjusting?
I am astounded by the lack of any tests done during the last 50 years. It has only been 0g for all those years - and extrapolations.
That's because no one has any way to conduct such experiments. You'd have to build a centrifuge big enough for people to stand up in. That means not just designing something like that, but solving all the stability problems that everyone keeps talking about. You're talking years of engineering and testing before you can even attempt the experiment.

I do wish we saw funding for at least the initial experiment. E.g. launch a cylinder on a F9 and do experiments rotating it, using different kinds of hardware trying to stabilize it. Then launch one with mice in it, maybe. What troubles me is that no one in authority seems to even be talking about it.

 

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