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#126 2018-11-16 22:26:00

kbd512
Administrator
Registered: 2015-01-02
Posts: 5,513

Re: Journey time to Mars...

Oldfart1939,

I'm going to start a separate topic entitled "Mars Communications and Navigation Infrastructure for Crewed Missions" in the "Unmanned Probe" section.  Maybe SpaceNut can selectively include whatever posts he thinks are relevant from this thread.

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#127 2018-11-16 23:08:39

Oldfart1939
Member
Registered: 2016-11-26
Posts: 2,296

Re: Journey time to Mars...

Good idea, since we've digressed considerably from transit time.

Last edited by Oldfart1939 (2018-11-16 23:08:59)

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#128 2018-11-16 23:13:58

kbd512
Administrator
Registered: 2015-01-02
Posts: 5,513

Re: Journey time to Mars...

Oldfart1939,

The new topic has been created.  SpaceNut and other mods, if you feel any posts from this thread are pertinent to the newly created thread, feel free to move them as desired.  If you feel the thread doesn't belong where I put it, feel free to move it to wherever you think it should go.

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#129 2018-11-17 14:30:07

JoshNH4H
Member
From: Pullman, WA
Registered: 2007-07-15
Posts: 2,526
Website

Re: Journey time to Mars...

louis wrote:

I think that - better than some perhaps - I conceive of the overall Mars project as requiring different approaches at different times on the development of the settlement. Indoor artificially lit agriculture makes sense when you have a population of 100 or even 1000. It doesn't make sense if you have a population of 100,000 or 1 million.

I would counter and say that, although different stages of settlement certainly will involve different configurations and technologies, artificial light for bulk farming is not one of them. 

I mischaracterized what you said about satellite dishes, and for that I apologize.


-Josh

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#130 2018-11-17 19:53:14

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 25,299

Re: Journey time to Mars...

This version of the board only lets me cut to a new topic and does not allow copy or merge to a topic. Some of those features were in other board software that we have used.

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#131 2018-11-17 20:59:22

kbd512
Administrator
Registered: 2015-01-02
Posts: 5,513

Re: Journey time to Mars...

SpaceNut,

Understood.

The new topic was created to discuss the pertinent infrastructure since this topic veered off from the problems associated with extended and excessively short travel times to Mars.  I think it's safe to say that a six month cruise to Mars is doable.  That's the standard cruise length for a US Navy carrier battle group.  UNREP (UNderway REPlenishment) is used to keep the carrier and her escorts at sea.  In this case, additional BFR flights and staging of consumables are used for the same purpose.  Getting to where you're going faster is always desirable, but not at the expense of all other aspects of the mission.  All carrier aircraft are specifically designed to take off with 30 knots of wind over the deck.  Whether the problem is easier with 60 knots of wind is immaterial to the fact that all systems required to launch and recover aircraft function adequately well with 30 knots of wind.  Some of the newer aircraft like the F-35 can take off with no wind over the deck, but only at the expense of significant fuel or weapons removal prior to launch, either of which would negatively affect mission capability.

The overriding point is that there's a reason that things work the way they do and while some aspects of a mission may involve arbitrary decision making, the engineering involved is definitely not arbitrary.  It's done the way it's done for a reason.

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#132 2018-11-17 21:11:43

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 25,299

Re: Journey time to Mars...

In that regards the mini bfr sure seems to be a good design step in that its got propellant remaining once achieving orbit after doing its business of satellite launch. It also looks like that its going to be adapted for manned flight as well.

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#133 2018-11-17 21:29:17

kbd512
Administrator
Registered: 2015-01-02
Posts: 5,513

Re: Journey time to Mars...

SpaceNut,

If you take Dragon (cargo capsule), Dragon 2 (crew capsule), Mini BFS (mini reusable cargo shuttle), Falcon 9 (medium lift), Falcon 9 Heavy (lift), Bigelow Aeropsace inflatables (radiation and debris protected habitats), on-orbit refill of LOX/LH2 upper stages with IVF, high power SEP, HIAD inflatable heat shields, and landers that use storable chemicals just like Apollo did, then you have a real lunar or Mars exploration program that doesn't require waiting a decade or more for gigantic rockets / spaceships and rocket fuel refineries.  I'm not saying Elon Musk shouldn't pursue BFR/BFS, but if he gets the reusable cargo shuttle right, then NASA has figured out the life support and everything else, so we have everything that's absolutely required to go to Mars and start exploring without an unacceptably high risk of failure.

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#134 2018-11-28 21:26:06

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 25,299

Re: Journey time to Mars...

350px-Mars_earth_orbit.svg.png

The position of mars when we could be launching from earth.

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#135 2019-07-21 10:54:45

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 9,948

Re: Journey time to Mars...

For SpaceNut ... the article from which this post is extracted concerns reducing journey time to Mars.

For Louis (who created the topic) ... I'm guessing you're going to be unhappy << chuckle >>

Today's weekend newspaper included an item which reports on research to restart thermal nuclear propulsion.

While several books have been written on the NERVA research project in the 60's, I've not seen much about ongoing research until this item appeared.

Because this article is about local people and institutions, and since my purpose here is to inform the global NewMars community, I'll omit local references.

If anyone is interested in seeing the local details, I have no doubt they can Google the article, since it is published online.

I do think it is important to credit the reporter, Beth Burger.

The last two International Astronautical Congress meetings were about missions you could fly with nuclear thermal propulsion.

...program has produced eight to 10 undergraduate-driven research papers

The president of a commercial company is interviewed toward the end of the piece.

...to advance nuclear thermal propulsion technology...

I am glad to see evidence that undergraduates at at least one institution are studying the engineering that will be needed when the human race finally decides to take on the risk of nuclear fission propulsion.

(th)

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#136 2019-07-21 12:28:59

louis
Member
From: UK
Registered: 2008-03-24
Posts: 7,208

Re: Journey time to Mars...

I'm not really opposed to nuclear power off planet Earth. I liked the atom bomb rocket - that's a technology that would genuinely work.

tahanson43206 wrote:

For SpaceNut ... the article from which this post is extracted concerns reducing journey time to Mars.

For Louis (who created the topic) ... I'm guessing you're going to be unhappy << chuckle >>

Today's weekend newspaper included an item which reports on research to restart thermal nuclear propulsion.

While several books have been written on the NERVA research project in the 60's, I've not seen much about ongoing research until this item appeared.

Because this article is about local people and institutions, and since my purpose here is to inform the global NewMars community, I'll omit local references.

If anyone is interested in seeing the local details, I have no doubt they can Google the article, since it is published online.

I do think it is important to credit the reporter, Beth Burger.

The last two International Astronautical Congress meetings were about missions you could fly with nuclear thermal propulsion.

...program has produced eight to 10 undergraduate-driven research papers

The president of a commercial company is interviewed toward the end of the piece.

...to advance nuclear thermal propulsion technology...

I am glad to see evidence that undergraduates at at least one institution are studying the engineering that will be needed when the human race finally decides to take on the risk of nuclear fission propulsion.

(th)


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#137 2019-08-20 12:50:31

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 9,948

Re: Journey time to Mars...

SpaceNut ... this post is about NASA progress preventing bone loss ...

I tried to find the best topic, and hope this topic will be acceptable.

The Space Show for August 16th is an interview with a gent who flew on the Space Shuttle, worked for SpaceX, and now teaches graduate level courses.

https://thespaceshow.com/show/16-aug-20 … in-reisman

About 10 minutes or so into the 60 minute program, Mr. Reisman reported that NASA has solved the bone loss problem, and he said that he felt that a crew could fly to Mars and not suffer bone loss.  He explained that steady experimentation on the ISS provided opportunities for medical doctors and engineers to improve the resistive exercise machine to the point that astronauts are returning to Earth without bone loss.

(th)

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#138 2019-08-20 17:59:37

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 25,299

Re: Journey time to Mars...

content is in the ISS topic under the human folder.
Exercise and drugs so far are the solutions that Nasa has rather than AG...

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#139 2019-08-21 16:37:28

louis
Member
From: UK
Registered: 2008-03-24
Posts: 7,208

Re: Journey time to Mars...

You're right TA...

I looked into this a few months ago, and everything I found suggested that the issue of muscle and bone loss has been resolved. I learend there is also wide range between people based on their genetic make-up...can't recall the exact figures but bone loss could be double or maybe treble in some people...so obviously in choosing your Mars crew you would screen out people with that disposition to bone loss.

I don't think the negative effects on the immune system have yet been resolved and there is of course the increased radiation risk. However, neither of those should have any significant long term effects, judging from ISS experience.

tahanson43206 wrote:

SpaceNut ... this post is about NASA progress preventing bone loss ...

I tried to find the best topic, and hope this topic will be acceptable.

The Space Show for August 16th is an interview with a gent who flew on the Space Shuttle, worked for SpaceX, and now teaches graduate level courses.

https://thespaceshow.com/show/16-aug-20 … in-reisman

About 10 minutes or so into the 60 minute program, Mr. Reisman reported that NASA has solved the bone loss problem, and he said that he felt that a crew could fly to Mars and not suffer bone loss.  He explained that steady experimentation on the ISS provided opportunities for medical doctors and engineers to improve the resistive exercise machine to the point that astronauts are returning to Earth without bone loss.

(th)


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#140 2019-08-21 17:09:13

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 25,299

Re: Journey time to Mars...

What we do know from the iss is that a journey out and back will have lasting effects on the body when no AG is present as was shown repeatedly on longer stays that get to the total time not on mars.
What still needs to be answered is will the long stay on mars at reduced rather than 0G is going to be much better....

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#141 2019-08-22 11:17:06

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,820
Website

Re: Journey time to Mars...

Bone loss and muscle weakness have been effects known and studied for decades.  The drug and exercise cures address these,  but not the other effects discovered more recently. 

These other effects include damage to the cardiovascular system,  which the drugs and exercise do not treat,  but which did show up in the bed rest studies (the surrogate did get us that). 

Since that discovery,  we have found vision problems that we think are due to the non-evolutionary redistribution of fluid pressures within the body over the 24 hour cycle.  We are not yet sure of this cause,  but it seems quite likely,  and there is no credible competing hypothesis.  There is no proposed treatment for this,  and it is not yet understood whether there is recovery of the damaged vision after returning to Earth. This occurs in spite of the drugs and exercise regimens that treat bone loss and muscle weakness.

There are degradations to the immune system.  We have no clue as to the mechanism,  much less the treatment,  but there is little doubt this is a bad thing.  The drugs and exercise regimes DO NOT address this.  It occurs despite them.

With the Kelley twin study,  we now know there are changes in the genetics.  We do not yet understand whether this is a health threat or not.  It seems likely that it is a threat to health,  but the fact is we are still quite ignorant. 

This trend says we have yet to discover all the ill effects of zero-gee exposure.  I confidently predict we will discover more things that limit how much zero-gee exposure we can tolerate to about a year. Or maybe less.

The real "cure" for all of this is very,  very simple:  provide artificial gravity,  to prevent any of these things from happening in the first place. 

The only physics we have to exploit for this is centrifugal force.  Do it at something close to 1 gee,  because we still have yet to determine how therapeutic reduced gee levels might be,  since we were too damned stupid to carry out spinning space station research in orbit all these decades since Gagarin flew.  THERE'S a bad management decision for you!

Artificial spin gravity might be inconvenient for enthusiasts of minimalist mission designs,  but ethics trumps all.  It is unethical to kill a crew by deteriorating their bodies in weightlessness to the point they cannot survive the high-gee rigors of atmospheric entry.  Or the rigors of operating in a hostile environment.  People for whom ethics matters cannot argue with this.

So,  if the ethics matters not to you,  then how about this selfish reason?  History of spaceflight demonstrates quite clearly that there is NOTHING as expensive as a dead crew,  ESPECIALLY one dead from bad management decisions. If you waste the money killing crews,  you never go anywhere.

So there.  That's my 2 cents' worth.

GW

Last edited by GW Johnson (2019-08-22 11:23:17)


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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#142 2019-08-22 17:15:47

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 25,299

Re: Journey time to Mars...

Thanks for stopping by GW as always with direct to the point commentary which are spot on if we are going to stay healthy.
Not sure why Oldfart1939, has not been around to aid in the health discusion as he is missed.

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#143 2019-08-22 17:55:42

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 9,948

Re: Journey time to Mars...

For SpaceNut re #142 ...

If the year of Oldfart1939's birth is encapsulated in his member ID, then it is time for an 80th birthday greeting.

(th)

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#144 2019-08-24 08:15:45

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,820
Website

Re: Journey time to Mars...

Hope Oldfart1939 is OK.  Haven't seen him post in some time. 

GW


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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#145 2019-08-24 08:40:45

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 9,948

Re: Journey time to Mars...

For GW Johnson re #144

» 2019-03-02 20:43:42

I like the fact that this post contains praise for the contribution of another forum member.  The post supports use of nuclear power to augment other propulsion systems for interplanetary orbit transitions. 

According to FluxBB, oldfart1939 created 1592 posts.

I went back to look at #1 and can see why the posts contain so much substance.

completed my Ph.D. in Physical Chemistry, with a strong orientation towards Biochemistry.

and...

my wife (also a great chemist) and I built a nice company manufacturing peptide hormones,

The "body of work" saved by NewMars.com for oldfart1939 is likely to contain a number of useful nuggets for younger forum visiters.

To see the posts, starting from the first,

Using FluxBB search:
Author: oldfart1939
Ascending Sequence
Posts (not topics)

(th)

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#146 2019-08-24 12:41:03

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,820
Website

Re: Journey time to Mars...

Thanks,  Tahanson43206.  If I can figure out what a fluxBB search might be,  I'll try it.  Are you referring to the red button top-of-page labeled "search"?  I honestly do NOT know. The only one of those buttons I have ever used is "logout",  which is something I actually did understand.  I do not know what the rest do.

You have to understand,  I know little and understand less about this modern computer stuff.  What I do get away with is monkey-see,  monkey-do,  with zero understanding,  just like the monkey.  When I first permanently entered the workforce in 1975,  we were all still using slide rules,  myself included.  Computers were big "mainframe" things you fed with a tray of paper punch cards.  So I am quite the old fart myself. 

The last computer stuff I saw were the scientific programming languages Fortran IV and QuickBASIC 4.5,  totally obsolete by today's standards.  Desktop computers appeared only a few years before I left the profession due to plant closure. I never even learned how to use all the stuff on a typical graphing calculator,  only about 10% of it.  Most of the words and phrases you younger types use,  have no meaning to an old fart like me.

GW

Last edited by GW Johnson (2019-08-24 12:42:53)


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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#147 2019-08-24 12:49:23

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 25,299

Re: Journey time to Mars...

The search button at the top is what is being referred to.

Word has it that Oldfart1939 has been having troubles logging into the forum....

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#148 2019-08-24 12:53:56

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,820
Website

Re: Journey time to Mars...

Back to topic:  journey time to Mars. 

If you fly by impulsive rocket propulsion,  journey time is maximum half the period of a (minimum-energy) Hohmann transfer ellipse.  If you fly a faster trajectory,  it requires a significantly larger departure delta-vee,  and you will arrive requiring either (1) a larger arrival delta-vee,  or (2) a free entry at a far higher entry interface velocity.  Either way,  you pay for the shorter trip with more propellant and/or a bigger heavier heat shield.

If instead you fly by electric propulsion,  the burns are much,  much longer and the gravity losses are much,  much higher,  offsetting in part some of the higher specific impulse.  You spiral out through the Van Allen belts for months,  which means you carry massive radiation shielding,  or else you kill the crew.  Arrival at Mars requires spiralling into orbit for a couple of months,  unless you do a free entry trajectory. Typically,  such transits are longer than the Hohmann min energy ellipse,  which means your supply of life support food,  water,  and oxygen is bigger,  and therefore heavier. 

The longer the transit,  the more radiation exposure you get,  and the more microgravity disease you incur.  Mars has reduced gravity,  but any gravity at all should help relative to weightlessness.  We just don't know by how much,  because in all the years since Gagarin flew,  we collectively have been too stupid to conduct the spinning space station experiments in LEO to find out.

Them's just the physics and the biology,  which no one can argue with. You picks your means,  and you pays your appropriate price.  Period.

We have had the capability to send a crew to Mars since about 1980.  We have known enough to more-likely-than-not get them home alive since about 1995.  We have yet to achieve the capability to do this at an "affordable" price (no firm definition actually exists for that),  but it looks like that is about to change (and I am NOT saying SLS will do this). Spacex and Blue Origin offer the way forward to cheaper spaceflight,  not NASA's mandated-by-Congress SLS and the overweight Orion it is supposed to carry.  To the moon,  not Mars,  it was NOT designed for Mars!

You do NOT do this mission flying a crew confined tightly within a cramped capsule.  They need the space in which to live,  to congregate,  and (most importantly) to get away from each other.  NO capsule will ever do that.  We have known since Gemini 7 that only about 3 weeks is tolerable confined in a capsule (which gets you to and from the moon,  no further).   Months to Mars like that is a recipe for cracking up into incurable insanity.

GW

Last edited by GW Johnson (2019-08-24 13:03:01)


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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#149 2019-08-24 13:05:28

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 25,299

Re: Journey time to Mars...

Nasa currently is one or the other for the propuslsion of rockets from earth orbit and seems to have little interest in a hybrid system once free of earth greater gravity well.

In that sense building on the moon for launching to other location starts with a small well of gravity to over come but that only works if you are building and launching from the moon with nothing coming from earth as there is still its penalty to account for in the cost and mass.

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#150 2019-08-24 19:39:02

louis
Member
From: UK
Registered: 2008-03-24
Posts: 7,208

Re: Journey time to Mars...

GW Johnson wrote:

These other effects include damage to the cardiovascular system,  which the drugs and exercise do not treat,  but which did show up in the bed rest studies (the surrogate did get us that). 

Since that discovery,  we have found vision problems that we think are due to the non-evolutionary redistribution of fluid pressures within the body over the 24 hour cycle.  We are not yet sure of this cause,  but it seems quite likely,  and there is no credible competing hypothesis.  There is no proposed treatment for this,  and it is not yet understood whether there is recovery of the damaged vision after returning to Earth. This occurs in spite of the drugs and exercise regimens that treat bone loss and muscle weakness.

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. 

Regarding vision...

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.  I suspect, that - as with muscle and bone loss - there is wide variation between individuals owing to genetic predispositions, meaning we can screen out people who react badly in terms of fluid effects on vision.

There are degradations to the immune system.  We have no clue as to the mechanism,  much less the treatment,  but there is little doubt this is a bad thing.  The drugs and exercise regimes DO NOT address this.  It occurs despite them.

This is one of the most interesting areas of space medicine.  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).  NASA is aware of risk factors.

With the Kelley twin study,  we now know there are changes in the genetics.  We do not yet understand whether this is a health threat or not.  It seems likely that it is a threat to health,  but the fact is we are still quite ignorant.

Sounds scary but not really.  Our gene expression changes all the time (genes getting switched on and off) and varies between twins. As I recall the study did not throw up anything untoward.

The real "cure" for all of this is very,  very simple:  provide artificial gravity,  to prevent any of these things from happening in the first place. 

The only physics we have to exploit for this is centrifugal force.  Do it at something close to 1 gee,  because we still have yet to determine how therapeutic reduced gee levels might be,  since we were too damned stupid to carry out spinning space station research in orbit all these decades since Gagarin flew.  THERE'S a bad management decision for you!

Artificial spin gravity might be inconvenient for enthusiasts of minimalist mission designs,  but ethics trumps all.  It is unethical to kill a crew by deteriorating their bodies in weightlessness to the point they cannot survive the high-gee rigors of atmospheric entry.  Or the rigors of operating in a hostile environment.  People for whom ethics matters cannot argue with this.

It might be the real cure but then it could be a case of a cure that kills you if something goes wrong.

I think this needs to be put in context. We know that some people get very sick at sea. In fact some people don't recover from sea sickness when they get back to land - their inner ear mechanisms having presumably been damaged. I am sure there are all sorts of changes to the body from breathing in salt laden air and we know that there are issues with being deprived of the fresh produce available on land. In our wisdom, rather than trying to design boats that don't pitch and roll we have basically preferred the approach of deploying "sea medicine" (ensuring sailors eat fruits like lemons and limes) and screening out people who suffer negative health effects at sea.  That approach has served us well. 

Not saying the parallels are exact (though a hurricane at sea is probably analogous to a radiation burst)but I think we do not need Artificial Gravity to get to Mars. We now know enough to ensure that carefully selected crew will return in a reasonably healthy condition.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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