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#151 2019-08-24 20:03:44

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,833
Website

Re: Journey time to Mars...

I'm sorry Louis,  but your responses to my post are simply not credible.

Regarding CV damage:  "I think the cardiovascular problems are likely overstated. No astronaut I know of has ever died of a CV problem during an ISS mission, however long, or on return." -- they haven't died of anything else,  either,  with the exception of bad management decisions.  So what?  Why does that reassure you?  It should not. Damage is damage,  whether it has yet killed anyone or not.  Sooner or later,  it will,  if not prevented,  because we humans have no spare heart.  What do you NOT understand about that?

Regarding vision damage:  "The NASA site states: "Distribution of the fluids in your body will be closely monitored, to help evaluate any connection to changes in your vision. Compression cuffs worn on your thighs will help keep the blood in your lower extremities to counteract those vision changes." So the vision issue is being addressed. Compression cuffs worn on your thighs will help keep the blood in your lower extremities to counteract those vision changes. So the vision issue is being addressed." -- that does NOT address body fluid pressure distributions at all!  Applying pressure on the legs forces blood out of,  not into,  the legs;  that's exactly how a gee suit works for a fighter pilot,  since the 1950's.  Forced out of the legs,  that blood goes to the head.  That's exactly the hypothesized cause of eyeball shape changes,  thus degrading vision.  Louis,  you ought to know better than that!  This NASA statement is just propaganda to deflect the ignorant public from the fact that how to deal with evident vision degradation is entirely unknown!  "will be closely monitored, to help evaluate any connection to changes in your vision" is the phrase that lets you know that they as yet know nothing about this at all. 

Regarding immune degradation:  "Again it doesn't seem to cause long term problems. One good thing is that there isn't much for a human to catch out in space, apart from re-activated viruses from fellow crew members (ie pathogens they were already carrying when they got on board and which might multiply)." -- the real problem isn't out in space,  it is when they come home.  A dead crew after return is still a dead crew!  Again,  NASA knows precisely NOTHING about why immune degradation occurs,  much less what to do about it.  You are grasping at straws.  Those straws have no substantiality. 

Regarding genetic changes:  "Sounds scary but not really.  Our gene expression changes all the time" -- an unwarranted if not entirely irrelevant statement.  Cancer is one form of genetic change.  Because we do NOT understand how this change occurs,  and because we do NOT understand what sort of threat it might be,  then there is NO reason to think this is an ignorable problem,  as you suggest.  You cannot disprove a negative.  Louis,  you know better than that,  if you even only graduated from public school.  Use your logic,  man!

Regarding providing artificial gravity:  "It might be the real cure but then it could be a case of a cure that kills you if something goes wrong." -- and just how might prevention go wrong?  Only if you use an untested technology and screw that up.  I have already described why rigid-body spin is far less a risk than any of the cable-connected spin-system approaches.  We humans have almost 3 centuries dealing very effectively with rigid body spin.  Not much to go wrong there.  Just do it.

"I think this needs to be put in context. "  --  the real context here is basic human ethics.  How dare we NOT provide spin gravity,  when we already know how to do it safely,  and it prevents all these ill or unknown effects,  both those understood,  and those not yet understood?

We may not need artificial gravity to get to Mars,  as you say.  But to survive there (in a very hostile environment),  and more especially to get home alive and in decent health,  there is very little doubt about the wisdom of providing artificial gravity. 

GW

Last edited by GW Johnson (2019-08-24 20:28:36)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#152 2019-08-24 21:23:30

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 10,438

Re: Journey time to Mars...

For GW Johnson re Reply to Louis ...

GW Johnson wrote:

We may not need artificial gravity to get to Mars,  as you say.  But to survive there (in a very hostile environment),  and more especially to get home alive and in decent health,  there is very little doubt about the wisdom of providing artificial gravity. 

GW

Louis has a knack for stimulating the most amazing responses from knowledgeable contributors on the forum.  kbd512 has impressed me as the most prolific responder to sallies by Louis, but the list is probably long and distinguished.

In the case of your post above, I've selected the key element to offer a thought or two.

First, I pondered why none of the space faring nations have allocated a single least-significant-monetary-element to artificial gravity over the decades since Sputnik.   The wisdom of using spinning habitats has been known since at least 1903 ...

https://en.wikipedia.org/wiki/Rotating_ … ce_station

History
Both scientists and science fiction writers have thought about the concept of a rotating wheel space station since the beginning of the 20th century. Konstantin Tsiolkovsky wrote about using rotation to create an artificial gravity in space in 1903.

In the end, it must be (or at least so it seems to me) that when program designers are doing the trades given the constraints of their budgets, they must have decided to stay with non-rotating habitats and vehicles because they appear to be able to get away with it, and because their other objectives are more pressing.

With the arrival of Calliban to the forum recently, and the consequent re-opening of discussion of expeditions to Apophis, it occurred to me this evening that there may be a way to take another look at the problem of justifying rotating habitats.

A factor which must weigh heavily (pun noted) on the minds of space system designers is the cost of mass to be lifted into orbit to accommodate the needs of human workers or passengers. 

If Apophis contains materials which could be adapted for fabrication of a rotating habitat, potentially the cost could be spread over a sufficient number of visitors to a facility.

Thus, in contrast to national space programs, commercial undertakings might have sufficient incentive, vision and fund raising capability to support an initiative to collect useful material from Apophis and allocate it to construction of one or more rotating habitats, including one which would warm the heart of Buzz Aldrin.

(th)

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#153 2019-08-24 21:36:23

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 25,731

Re: Journey time to Mars...

https://www.telegraph.co.uk/science/201 … in-damage/

Astronauts on a mission to Mars could losen early half their muscle strength during the long trip, giving them the physiques of senior citizens by the time they arrived, according to a new study.

Prolonged exposure to weightlessness could cause astronauts to lose more than 40 percent of their muscle strength even with regular exercise, researchers said. On a long voyage, a healthy 30- to 50-year-old astronaut could end up with the strength of an 80-year-old.

A 10-month trip to Mars would cause such extreme muscle deterioration that astronauts would find it difficult to perform even routine tasks, let alone move around the Martian surface in spacesuits, according to the study, which was led by Robert Fitts of Marquette University.

During their six-month stints aboard the International Space Station, astronauts exercise about 2.5 hours per day, six days a week...

So just how many do any of us do a day?

https://www.nasa.gov/hrp/bodyinspace

https://www.apa.org/monitor/2018/06/mission-mars

This contains lots of details on the effects
http://planetary-science.org/planetary- … s-to-mars/

https://en.wikipedia.org/wiki/Effect_of … human_body

Something are slightly mitigated but the effects linger long after....

Among the top health hazards for three-year, round-trip Mars missions: space radiation that could cause cancer, central nervous system damage, cataracts or infertility; extreme isolation, which could lead to psychological problems; and prolonged weightlessness, already known to weaken bones, muscles and vision.

https://nei.nih.gov/news/pressreleases/010809

https://aerospaceamerica.aiaa.org/featu … d-to-mars/

AA_Nov18_Mars_Opener-1200x675.jpg

If propelled by conventional chemical rockets, and depending on the trajectory, a round-trip mission to the red planet including time on the surface could take as long as 900 days.

That would mean spending about twice as many consecutive days in weightlessness as the all-time record holder, Russian cosmonaut Valeri Vladimirovich Polyakov, and nearly three times more days than the U.S. record holder, astronaut Scott Kelly.

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#154 2019-08-24 21:39:27

kbd512
Administrator
Registered: 2015-01-02
Posts: 5,730

Re: Journey time to Mars...

I tend to think artificial gravity is a hard requirement for extended duration space flight, even if microgravity is not immediately lethal to the people onboard.  We have "fixes" for the bone loss problem that have been proven to work with a small sample set, but no fixes at all for cardiac muscle deterioration and no fixes for some of the thigh muscle deterioration, which, when last I checked, was required to walk.  All in all, extended duration microgravity looks like a really bad idea to me.

What are you supposed to do on Mars after you get there if you can't see or walk very well?

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#155 2019-08-25 09:10:33

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,833
Website

Re: Journey time to Mars...

The AG thing is like the radiation thing for NASA:  an excuse not to go to Mars.  They'd rather just go to the moon,  because (for shorter stays) it requires only what they have already done before.  That is to ride in capsules (same as since 1961),  with no more than a Skylab for hab volume (same as in 1973),  weightless in space (same since 1961),  and without significant radiation shielding (same since 1961). 

They can go back to the moon or cis-lunar space like that,  reprising Apollo with shuttle (same as since 1982)  and ISS technology (same as since 1990).  Until they kill a crew from solar flare exposure. Which will put an end to NASA-led human spaceflight with the political consequences.

Going to Mars requires that NASA and its favored contractors do things they have never done before:  (1) provide radiation shielding in some way that does not overwhelm the dead weight,  and (2) provide AG in some way that does NOT require building "Battlestar Galacticas" which no one can afford.  NASA resists doing that because it is not the NASA of 1958-1963. It is now a huge bureaucracy trying to be all and do all for everyone,  while its projects are dictated by powerful congressmen incompetent to make those decisions.

The radiation shielding problem is somewhat addressed by insulated inflatables such as Bigelow and maybe some others.  A meter's thickness of polymer fabric layers (see Bigelow B-330),  at an average volumetric solidity of say,  20%,  and an average solid density near that of water,  corresponds to about 20 g/sq.cm shielding with low molecular weight materials that reduce the secondary shower effect as well.   That's not too bad as a solar flare shield. 

Musk claims his Starship also has a solar storm shelter,  but he has not released any details of how this is done. 

NASA is doing none of this.  See the difference?

NOBODY is as yet addressing the AG thing,  except to propose crews riding in capsules or small modules at the ends of cables.  Cable connected systems are subject to complex dynamics just for spin-up and spin-down,  much less applying thrust while spinning.  There is much engineering development to be done there,  because the only real experience we have with this concept is the sling and the South American bolo weapons.  That experience is not applicable to this AG application.

In contrast,  the dynamics of rigid-body spin is well-understood and has centuries of experience behind it.  Far less engineering development work is needed to apply it successfully to the AG problem.  But you have two choices:  (1) spin a Battlestar Galactica like a rifle bullet,  or (2) spin a long, narrow (but much less massive) vehicle like a baton-twirler's baton at a Friday Night Lights football game.

NOBODY is doing this,  yet.  But it needs to be done,  to go routinely to Mars,  or anywhere else outside cis-lunar space,  because of the long travel times. Long,  regardless of how you are propelled to go there!!!

Musk is betting (betting,  mind you,  because nobody yet knows!!!) that Mars's 38% gee surface gravity is enough to be therapeutic for microgravity diseases.  That's likely a fairly-good bet,  but it is also not likely to be a perfect solution.  No one knows what reduced-gee health degradations might look like,  because those experiments (while proposed since the early 20th century) have never been done. Stupid is as stupid does.  Or does not.

We have known about the solar flare radiation death risk since Apollo.  We have known the health risk is serious due to microgravity exposure since about 1995 on ISS (and all earlier stations back to Skylab). NASA has done nothing substantive about either since then,  except to search vainly for ways to fend-off the microgravity diseases.  They just keep uncovering more and more unexpected deleterious effects as the research continues,  far beyond bone density and muscle-weakness problems.  THAT has been the real trend of all these years of microgravity research.

Non-NASA entities are beginning to seriously address the radiation shelter issue.  NOBODY (non-NASA or NASA) is as yet effectively addressing the AG issue.  And THAT's what the state-of-the-art looks like to me. 

GW

Last edited by GW Johnson (2019-08-25 09:53:20)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#156 2019-08-25 12:59:11

kbd512
Administrator
Registered: 2015-01-02
Posts: 5,730

Re: Journey time to Mars...

GW,

You're preaching to the choir here, but I do hope NASA will actually solve the problem since nobody else is.  There's only one known complete solution for microgravity diseases, namely more gravity.  Until Star Trek technology comes along, that's what humans will require for extended duration space flight.  I, too, favor the inflatables for their ability to expand in space to something the size of what's required for AG to work, along with much greater resistance to penetration by space debris and modest radiation protection rather than enhancement properties.

Anyway, apart from durability during reentry, a stainless steel can is no better than an Aluminum can for deep space flights.  As a result, we're going to need advanced fibers like CNT and BNNT for the habitable inflatable section.  The Kevlar and Spectra fibers in use today won't cut it.

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