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Open Lines, Sunday, 2-2-14 February 3, 2014

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Open Lines, Sunday, 2-2-14

http://archived.thespaceshow.com/shows/2178-BWB-2014-02-02.mp3

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Guest:  Open Lines with Dr. David Livingston.  Topics:  Artificial & natural gravity, Leonardo DiCaprio, HSF to Mars.  Please direct all comments & questions regarding Space Show programs/guest(s) to the Space Show blog, https://thespaceshow.wordpress.com.  Comments & questions should be relevant to the specific Space Show program. Written Transcripts of Space Show programs are a violation of our copyright and are not permitted without prior written consent, even if for your own use. We do not permit the commercial use of Space Show programs or any part thereof, nor do we permit editing, YouTube clips, or clips placed on other private channels & websites. Space Show programs can be quoted, but the quote must be cited or referenced using the proper citation format. Contact The Space Show for further information. In addition, please remember that your Amazon purchases can help support The Space Show/OGLF. See www.onegiantleapfoundation.org/amazon.htm.

Welcome to this two hour one minute Open Lines discussion on what turned out to be mostly about artificial gravity.  While there were actually two breaks in this program, since the topic was the same throughout the full show, I am archiving this as a single segment summary.  We started the program by my making announcements, then reading parts of an article that recently appeared in the Turlock Journal (www.turlockjournal.com/section/26/article/23874) that talked about the green efforts by actor Leonardo DiCaprio but also pointing out his having arranged to be an early passenger onboard SpaceShip2.  The author of the article, Dennis Wyatt, then pointed out the hypocracy of Mr. DiCaprio by examining the carbon footprint of SpaceShip2 & comparing it to cars & other things, pointing out the enormous consumption and carbon footprint that will be unloaded on Earth by Mr. DiCaprio’s flight.  I read parts of the article to point out the hypocracy among those that preach to us to do as they say yet they seldom if ever walk their own talk.  I also mentioned articles in the informative menu of The Black Bear Diner Gazette from their Emeryville, CA menu, one of which was an old news article saying that NASA Administrator Thomas Paine predicted & had a goal of doing a HSF mission to Mars by 1981-82.  Some of the callers for today’s discussion did offer comments on both the DiCaprio article as well as wondering if we could have gone to and from Mars with astronauts back in 1981-82.  However, by far, the topic of the day was artificial gravity, a topic which really surprised me.  The callers and those sending emails wanted to talk about artificial gravity, their understanding of it, how to achieve it, their analysis of it, and more.  The callers talked 2 RMs, 3 RPMs, 4 RPMs, we talked about some of the comments by the life scientists on this subject on previous shows, much of which was discarded by the callers who had a focus on engineering and physics and their own perspectives.  We also talked about the difference between partial gravity & full 1 g artificial gravity.  I mentioned that many were unsure that 1 g of artificial gravity would be the same as 1 g here on Earth but that was quickly discarded by all callers and those sending in emails.  Our callers also talked about experiments that should take place using free flyers adjacent to the ISS to study some of the artificial gravity questions in preparation for long duration human spaceflight.  Because of the unexpected interest in artificial gravity, I have decided to arrange for updated programming on the subject with “experts” representing aerospace medicine, life scientists, engineers that would be designing space based centrifuges, and more.  I will be announcing these programs as they are scheduled & they will appear in the weekly newsletters.

Please post your comments/questions for this show on TSS blog above.  You can reach any of the callers to this program by sending your email through me at drspace@thespaceshow.com.

Comments»

1. Robert Walker - February 11, 2014

Have written up my reply, with many more details as a Science20 article for my column there, which some of you may find helpful: http://www.science20.com/robert_inventor/blog/can_spinning_habs_solve_serious_zero_g_health_issues_can_humans_live_mars_or_lunar_g_why_nobody_knows-12942

2. Space-for-All at HobbySpace » Space policy roundup – Feb.7.14 [Updated] - February 7, 2014

[…] Open Lines, Sunday, 2-2-14 – Thespaceshow’s Blog – General discussions […]

3. Doug Plata - February 4, 2014

Check out the attached spreadsheet and Power Point that I created in regards to artificial gravity. That is at:

http://dropevent.com/Gallery/tick18351

I tried to do the calculations for each reasonable scenario.

In the Power Point, the solid circles are for 3 rpms and the dotted circles are for 4 rpms. You can see that it makes a significant difference. the circles and the lines that I have colored red indicate my choice of what I think should be done which I’ll explain presently. The numbers associated with the circles are RADII not diameters. I have included a scaled football field for comparison.

So the three major categories that I can think of are:

1) Experimental – This would be a free-flyer spinning habitat to help us determine the biologic response curve. I have chosen a single free-flyer with two cages, the masses being asymmetric such that one cage would have a primate at Mars gravity and the other being at .67 gravity. I do this so that we can get a sense of the shape of the curve whether it is linear, upsloping, downsloping, s-shaped, or reverse s-shaped. If the experiment seems to indicate that .67 gravity is insufficient (upsloping curve) then I think that we should just give full artificial gravity.

2) To “Adequate” Artificial Gravity – Of course we don’t know what “adequate” means until we do the experiment. But indications are that maybe Mars gravity is not sufficient. IF there is an adequate level of gravity then the experiment in 1) will give us an idea of what that might be.

On a long trip to Mars, it really doesn’t make much sense to give only partial gravity. The mass of the tether isn’t that great considering the overall mass of system including deceleration propellant. So I say, why bother with partial artificial gravity. Let’s provide full artificial gravity. I personally think it safer to have the astronauts have their full strength than have them accustomed to Mars gravity. But opinions may vary on that point. If necessary then we could slow their spin for the last couple of weeks just before they arrive at Mars.

So, what I see the “adequate” artificial gravity relating to is actually for permanent bases and settlements on surfaces. In this case we are dealing with either swing arm centrifuges or (my preference) what I call the “tetherball” approach in which you have a t-bar with cables coming off which swing out when operating. Look at the 5th from last past on my cislunarone.com website for a picture illustrating this concept. With trenches and shielding above the head, one could theoretically provide shielding during artificial gravity although I think that there would be the risk of striking the sides. Again, the alternate solution is a rollercoaster track in a shielded trench although this would require significant metals production.

I choose to go with 4 rpms because the swing arm length is significant when you are under the gravitational field of a planet and the faster rotation rate significantly reduces the necessary radius. If people cannot adapt to the Corliolis effect of 4 rmps then perhaps people would need to secure their heads while undergoing artificial gravity.

Do notice that achieving adequate artificial gravity on Mars means a fairly short radius, only 16 meters. That is because Mars already gets us 38% of the way to whatever the adequate artificial gravity is.

3) To Full Artificial Gravity – This would relate to a trip to Mars in which we tether between the fuel and hab and then spin up. Again, since the mass of the tether is a relative small percentage of the total mass, then I’d say, let’s provide full gee.

4. Robert Walker - February 4, 2014

Hi David,

Enjoyed the show – as I watch them afterwards, I couldn’t email or phone in.

Anyway it was a bit of a coincidence, as I’ve been having long discussions about this recently too, with a conversation with Hop David on one of my articles
http://www.science20.com/robert_inventor/trouble_terraforming_mars-126407
and continuing also on his blog
http://hopsblog-hop.blogspot.co.uk/2013/12/whats-minimum-spin-hab.html

and in other places.

So anyway, with my background in maths, and also after this discussion and looking up lots of details, perhaps I can help clear up a few things.

DIFFERENCES BETWEEN ARTIFICIAL GRAVITY AND NORMAL GRAVITY

Both you and your guests are right. Einstein with his thought experiments showed that there is no way you can distinquish between uniform acceleration in a straight line and a uniform gravitational field. However artificial gravity in a rotating habitat is not the same as uniform acceleration in a straight line, and the Earth’s gravitational field is also not uniform (though that’s probably a negligible effect here).

Then the thing is that there are several other effects, not just the Coriolis effects, though they are all less noticeable as the habitat gets larger. The effects you might notice right away are:

1. Your weight will change slightly as you move around the habitat, depending on the direction and speed of motion. In a very small spinning habitat, if you run fast enough (or cycle) in the direction opposite to the direction of spin, then you could become weightless. Cycle even faster and you gain weight again.

2. You also have the spining motion itself. This is different from the coriolis effect. For instance if you took a perfectly balanced gyroscope, you’d notice that from your point of view, it turns around on the spot once every revolution.

3. On a small spinning habitat you’d notice that the gravitational effect on your head is different from the effect on your feet. For instance if you bend to pick something up and then stand up again you might notice that your ears and tongue suddenly feel lighter.

All those effects are subtle but in a small rotating habitat the first two would be perceptible, and all of them might also have health effects.

There are other differences of course. On Earth then you can tell that the gravitational field is non uniform because the stars directly overhead change depend on your exact geographical location, but only if you travel a long way.

On the spinning habitat you’d notice that the upwards direction is different for you and for your friend a quarter of the way around the habitat.

Then there is an effect a bit like 2 of the spining motion itself on Earth also, but of course more subtle. Anywhere except at the equator, the Foucault’s pendulum changes direction gradually as it swings. Anywhere on the Earth, you could notice that a perfectly balanced giroscope changes the direction of its spin axis in a 24 hour cycle.

And we have minute coriolis effects here as well, but also too subtle to be important except at the scale of large scale weather effects such as hurricanes.

TESTING IN A CAROUSEL

Yes you could test in a Carousel. But sadly it’s not the same as artificial gravity. The axis of rotation is parallel to the direction of the perceived g force (or at an angle if you spin it fast enough to go above 1g) while the axis of rotation in a habitat in space under artificial g is perpendicular to the perceived g force.

So, the coriolis effects work in a different way from a carousel, and we can’t simulate this on Earth. You get coriolis effects as a result of vertical motions rather than horizontal motions. For instance as you stand up in a small rapidly spinning habitat, you will find you tend to tip over slightly in the direction opposite to the spin, and don’t get this effect at all in a carousel, while with a carousel, you will get horizontal coriolis effects – if you try to walk in a straight line you get pushed sideways.

Also you don’t have the difference in gravity between head and feet you get in a small rapidly rotating habitat under artificial g.

Then of course you can’t test the combination of the rotation effects with gravity below Earth gravity. The effects might be worse under low g, or not so noticeable, and is no way to tell with carousel experiments on Earth.

That’s enough of a difference that I think it’s not really possible to draw any firm conclusions about artificial gravity from ground studies.

RESULTS OF CAROUSEL TESTS ON EARTH

However the experiment has been done.

First, humans can adapt to spinning in carousel type motion. Figure skaters particularly learn to spin many times on the spot, very rapid spins that would make anyone else sick. They start with just one or two rotations and gradually build up to eight, so that shows you get some adaptation to spinning motion.
http://www.slate.com/articles/news_and_politics/explainer/2010/02/spin_dance_jump_repeat.html

As for someone who spent a lot of time on a carousel, well there was this story of someone who spent over 52 hours on a circus carousel
http://staugustine.com/stories/041403/new_1465728.shtml
Carousel rider breaks record after 52+ hours
And someone else who spent 25 hours in a Ferris wheel
http://losangeles.cbslocal.com/2012/06/01/lapd-detective-completes-25-hour-ferris-wheel-ride-for-charity/
Seems no reason why that couldn’t last for longer.

But, NASA has also tested this too. No need to do a kickstarter experiment to do the tests, have already been done.

TESTS IN CAROUSEL TYPE ROTATING ROOMS

However the experiment has actually been done, series of experiments by NASA with people living in a rotating room for hours at a time. They did find that people adapted to it and that they no longer perceived the Coriolis effect but learnt to compensate for it.

http://science1.nasa.gov/science-news/science-at-nasa/2004/23jul_spin/

They found that people could adapt to 25 rpm in their rotating room. So that’s pretty fast, much faster than the often quoted 3 rpm.
http://www.bio.brandeis.edu/faculty01/dizio_lackner.html

If you can get the authors, Lackner and DiZio on your show could be interesting to hear what they say.

EXPERIMENTS WE COULD DO

First, you could fly some small mammals to the ISS together with a lightweight carousel for them to live in for a few months of artificial gravity – but would it be conclusive for human adaptation?

There doesn’t seem to be much risk in using human “guineapigs”, humans could spend some time in artificial g with no more ill effects than zero g. You could start off with micro g as for Gemini 11. Then once you see what effect that has, gradually increase the artificial g and try lunar, then Mars gravity and then finally full gravity, of course monitoring health all along.

Joseph Carrol suggested that as an experiment that astronauts could do before they dock with the ISS, using a spent booster stage as the counterweight for the artificial gravity.

I believe myself that humans would probably adapt to artifical gravity even in a small habitat, say the size of the ISS or smaller, spinning fast enough for artificial gravity. Also that you could have centrifuge type sleeping quarters, and since the astronauts just lie down in their quarters rather than walk and move about and spend most of their time there asleep, then I think those could probably be even smaller, just a few meters across.

Here are a couple of links to Joseph Carrol’s work:

http://www.artificial-gravity.com/IAC-10-D1.1.4-presentation.pdf
– powerpoint slides presentation

http://ssi.org/2010/SM14-proceedings/Design-Concepts-for-a-Manned-Artificial-Gravity-Research-Facility-Carroll.pdf
artificial gravity – joseph carrol

There are many more papers here by various authors:
http://www.artificial-gravity.com/

Hall’s paper on the subject:
http://www.artificial-gravity.com/SSI-1991-Hall.pdf

Oh, and I’m sure that if we had attempted to send humans to Mars in the 1980s inspiration Mars style, we’d have failed with dead astronauts as I think might well happen with inspiration Mars even with our current technology if they just try to do it in one go with no precursor missions close to Earth first.

But perhaps they would have done it step by step. After all that was the key to success for Apollo. I think once the plan got filled out surely they’d send humans into space for long duration flights close to Earth, first, and would have encountered the zero g health issues sooner, and then tested ways of generating artificial gravity. Surely NASA even back then wouldn’t have sent humans straight to Mars in one go. Then they’d also need to work out all the problems involved in keeping humans alive long term in a closed habitat without supply from Earth.

After that research, surely they’d have sent the astronauts under artificial g and would be way ahead of us in their understanding of artificial g and closed habitats. But would surely have cost a lot more than expected because they wouldn’t know in advance about all the issues that can arise with zero g. As for delta v then a fly by of Mars or just entering Mars capture orbit and return, then that’s the same as for Apollo, so one way or another I think they could have done it. Landing on Mars is a whole new ball game though in terms of delta v, massively harder to do. They could have done it with many launches from Earth first. But personally I’m glad they didn’t because of the potential contamination issues.

As you know from the space show and my science20 articles, as someone with both an enthusiastic interest in space exploration, and deep interest in the scientific and biological results that could come out from those explorations, sadly I find those two interests at odds with each other when it comes to human missions to the Mars surface (unless the contamination issues can be addressed and I can’t see how that is possible with current technology) though not a problem at all when it comes to missions to Mars orbit or telerobotic exploration of the surface.

But I’m with the Mars explorers all the way as far as orbital missions to the planet and telerobotic explorers. Hopefully even back in the 1980s they’d have realised the contamination issues before they actually landed on the surface, but I’m not totally sure they would as we are far more aware of such issues now. For instance with the Apollo mission then the quarantine regulations were issued on the day of launch of Apollo 11 giving no-one a chance to inspect them and ask for changes. That would not be permitted today. We, all of us including myself, with few exceptions such as Carl Sagan of course, simply didn’t pay much attention to such things back then.


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