Space X - getting ready for Mars.

RobertDyck · 2017-08-27 02:17:33

GW Johnson wrote:

We have never done electric spiraling, crewed or not.

Actually, that's not true. European Space Agency (ESA) used electric propulsion to spiral out of Earth orbit to send an unmanned orbiter to the Moon. SMART-1 Launched in 2003. I spoke to a member of ESA at a symposium and mentioned my idea of using electric propulsion to spiral out of Earth orbit, use the Moon for gravity assist, then proceed on to Mars. This was for a Mars Society mission to Mars, and something some of us wanted to send before the Columbia accident. The idea was to launch a very small, inexpensive mission as a Get-away special on Shuttle. I mentioned this idea may have difficulty getting out of LEO due to atmospheric drag. There's not much drag in LEO, but electric propulsion doesn't provide much thrust. The idea of electric propulsion is very high Isp but low thrust, you accumulate speed gradually over long time. Efficiencies of electric propulsion will be compromised until you get out of LEO. The ESA representative was interested, so used it to send a probe to the Moon as an ancillary payload on an Ariane 5 launch of a satellite into GTO. They started in GTO so avoided the problem of atmospheric drag.

Using electric propulsion for human missions would have the problems you mention. Yes, spiralling slowly through radiation belts is a bad idea. Space has zero-g, radiation, and humans consume food and water the whole time, so you want to transit very quickly. That means slow spiral works for cargo, but not crew.

As for ADEPT or HIAD: to quote Nike commercials "Just Do It!" There is no way around it, you can't design the mission to avoid it. Just Do It! I have said many times, all orbiters sent to Mars must use aerocapture to demonstrate this critical technology. Stop concocting excuses and just get it done!

This is not new! We've known what has to be done for decades. ADEPT was part of the Mars Direct mission plan. Martin Marietta ordered all their engineers to come up with practical plan to go to Mars, something Congress would actually approve. That order was right after Congress denied NASA's request for $450 billion in 1989 dollars, part of the 90-Day report. That was in 1989. Dr Robert Zubrin and his partner David Baker were one of the teams at Martin Marietta. Their work was in the last quarter of 1989 and first half of 1990, presented to NASA in June 1990. Today is end of August 2017, over 27 years later! How many more decades before work will begin? There are several critical technologies that are absolutely required. Congress explicitly stated they will not fund the 90-Day Report, they will not fund Battlestar Galactica. We need ADEPT and/or HIAD, and both need to be demonstrated by placing an unmanned orbiter into orbit about Mars. Enough times for the technology to be mature. No excuses, JUST GET IT DONE! We also need artificial gravity with a tether! Again, it has to be tested in space first! There is no way around this, you can't design a mission architecture to avoid it. JUST GET IT DONE! Return will require ISPP. Again this has to be demonstrated with an unmanned mission before we commit human lives to it. Again: JUST GET IT DONE!

To those at NASA who refuse to do the work, I am reminded of this:

Perhaps I shouldn't let my emotions get the best of me. There's a better way of dealing with this...
Screen-Shot-2015-07-15-at-11.00.46-AM.jpg

Last edited by RobertDyck (2017-08-27 11:31:26)

SpaceNut · 2017-08-27 07:59:16

Well the Hypersonic Deployable Decelerators started
Adaptable, Deployable Entry Technology and Placement (ADEPT) Project An Overview Presentation for IPPW10 EDL Short Course back in June 15, 2013 with and shows up as Advancements in Thermal Protection Materials Change the Game for Orion followed by a NASA Completes Successful Heat Shield Testing for Future Mars Exploration Vehicles and that seems to be wheere the trail goes dead as no further updates of this technology have been promoted for Mars use. IPPW-13 Program Abstracts - EDL Technologies Session

GW Johnson · 2017-08-27 10:52:22

RobertDyck makes good points, although I do NOT agree that what he suggests is the ONLY way to get these jobs done. He did seem to imply that.

I didn't know about the ESA electric spiral-out satellite. That's a very good demonstration example. I do believe multiple examples are necessary before we trust this for any sort of a crewed mission, much less an interplanetary one. One is just not enough.

Most of the unmanned satellite guys want to see more demonstrations like this, as well, before they commit to widely using this technology That's just prudence. So like RobertDyck said, let's get on with doing some of those demonstrations. Perhaps starting out as piggyback payloads riding up with other launches.

Same is true of HIAD and ADEPT. It is time to send some of these up and start testing them in/from LEO. While Earth entry might be an overtest for Mars entry from Mars orbit, it might not be such an overtest for direct entry or aerobraking from interplanetary trajectories at Mars. Point is, this flight testing stuff must be done before we deploy these new technologies, whether for unmanned or manned use. It's just part of the job, and one that is not getting done as it is now.

From what I read, there is excess payload capacity in every Dragon sent to ISS. Why not just put some test articles aboard to piggyback a ride up, and conduct these experiments from ISS?

I do disagree that tethers are the only way to do spin gravity. That path requires quite a bit of development, because we never have done much of this tether stuff (the Gemini-Agena spin experiment was a hard dock, not a tether). If instead you plan on spinning a rigid structure, there is much less development needed, simply because we already know far more about that kind of system, and we have far more experience with it, stretching back centuries.

But either way, I quite agree that we need to "get on with the war" and go do these things. Again, small initial experiments toward these things could ride up as more cargo closer to capacity on every Dragon sent to ISS. Maybe Orbital's vehicle, too.

As for NASA, they as an institution have a demonstrated history for many years now of not really wanting to go to Mars, various small groups within NASA notwithstanding. I'm not at all sure they really even want to return to the moon. The service module for Orion lacks the delta-vee to reprise Apollo-8. And where is the lander? Actions speak far, far, far louder than words. And inaction is a form of action.

We need far more practical spacesuits to get outside and do anything useful, whether on the moon or Mars. I see little going on within NASA to address that. The closest thing might be Musk's new suit, but that's NOT an EVA suit. It's not NASA either. Paul Webb (the MCP guy) is no longer with us. His closest thing to an heir apparent is Dava Newman. NASA hired her, but pulled her out of doing any MCP suit work. That alone is evidence they (NASA) don't really want to return to the moon or go to Mars.

GW

RobertDyck · 2017-08-27 12:17:26

GW Johnson wrote:

We need far more practical spacesuits to get outside and do anything useful, whether on the moon or Mars. I see little going on within NASA to address that. The closest thing might be Musk's new suit, but that's NOT an EVA suit. It's not NASA either. Paul Webb (the MCP guy) is no longer with us. His closest thing to an heir apparent is Dava Newman. NASA hired her, but pulled her out of doing any MCP suit work. That alone is evidence they (NASA) don't really want to return to the moon or go to Mars.

True. However, Dava Newman no longer works for NASA. Her employment ended the same day as Trump's inauguration. She has returned to MIT, once again a professor. Her title is now Apollo Professor of Astronautics and Engineering Systems. Perhaps she will resume work on MCP.

SpaceNut · 2017-08-27 15:44:53

This is about the best image that I have seen that shows how the thermal blanket of Adept hooks onto the landing unit...just under the heatshield....

https://gameon.nasa.gov/projects-2/depl … xible-tps/

This one has the fabric stretched on what is a hypercone structure of inflated innertubes starting small and stacked up until they reach the large diameter needed.
https://gameon.nasa.gov/projects/hypers … or-hiad-2/

Proving Ground Phase 1 Flight Test Objectives, Mapping of ongoing technology development activities in Backup

While the slides steps are happening they are going way to slow and the timeline with be about a decade off at this point for manned flight and ok for the unmanned robotic missions...

Technology Capabilities for Human Exploration of Mars

RobertDyck · 2017-08-27 17:00:14

GW Johnson wrote:

(the Gemini-Agena spin experiment was a hard dock, not a tether)

Gemini 8 did the hard dock with Agena. Gemini 11 used a tether.

SpaceNut · 2017-08-27 17:09:04

I see reading through the last link I posted that on page 10, 11 Nasa had penciled in sub scale for Mars demonstrators?

What a waste....

Slide 25 gives the clues as to what is being worked with funding indicated, which is not much

RobertDyck · 2017-08-27 22:46:11

Actually, I disagree. Technology must be demonstrated before we commit human lives. I have long argued in favour of a robotic Mars sample return mission, not for the samples themselves, but because that's the best way to demonstrate ISPP. The Mars 2001 Lander would have demonstrated generating oxygen from Mars atmosphere, but that's all. Sample return would demonstrate everything, end-to-end. It would demonstrate aerocapture as well as MAV, both sub-scale. Once that's done, do a single unmanned mission with the manned equipment. That's the human scale. It's unfortunate that MAVEN and MRO didn't use aerocapture; they should have. Now there are no plans for another NASA Mars orbiter.

Checking slide 25... It's interesting that sub-scale aerocapture is listed as fully funded, and human scale EDL is partially funded. Commercial Cargo and Crew to Cis-Lunar (both short and long stay) are shown as partially funded, but to Mars is shown as "Opportunity" in dark grey with nothing in the legend to explain that. Red is "Not Funded", but it isn't red. Exploratory ISRU is fully funded for Cis-Lunar (short and long stay), as well as exploratory ISRU & atmosphere for Cis-Mars robotic, but ISRU for Mars-Surface is not funded.

GW Johnson · 2017-08-28 10:03:56

I remembered the high altitude of Gemini 11, but had forgotten the tether experiments. That 850 mile altitude is right under the "bottom" of the van Allen belts. That's why they flew no higher.

The tether-based orbit attitude stabilization did not work at all, primarily because you cannot push on a string, and compression forces along the structure are inherently unavoidable. Rigid-attached long-body stabilization experiments have since succeeded.

The spin for .00015 gee on a long tether like that suggests that they never achieved much in the way of stable spin rate at all. That isn't so much a deploy problem, as it is a thrust-on-a-spinning object problem, since the spin was initiated after the tether was extended.

That bodes ill for all the midcourse adjustment concepts with spinning cable-connected assemblies. And THAT is why I say that approach is risky, and undeveloped.

All in all, that Gemini-11 experiment achieved very little in the way of demonstrating spin gravity in tether-connected assemblies. Very much remains to be done. Essentially everything still remains to be done.

In contrast, we have centuries of experience in designing and predicting rigid spinning things. You can see how well-developed this technology is at the tire balance machine in any auto place with such a rig. All that is required to reach 1 gee at 56 m radius and 4 rpm is four variants of the Bigelow B-330 module docked end-to-end with a hard-shell airlock-and-flywheel module in the center.

No "battlestar galactica" there (under 100-120 tons loaded with equipment and supplies). Yet it's a stick in the vicinity of 110-120 m long spinning end over end, with near 1500-1600 cubic meters of internal volume to design with. 1 full gee at each end, and every partial gee as you approach zero gee at the center. Spacecraft docking with it merely roll at 4 rpm to match spin, and then dock at the center, where centrifugal forces are essentially zero.

This could be either a space station in LEO, or the habitation of an orbit-to-orbit crew vehicle. Add engines at one end, and dock a layer of skinny propellant tanks around the periphery, and you have both propulsion and radiation shielding. You dock the departure stage to the other end. Use the propellant in the tanks to arrive at your destination. If you sent ahead more loaded tanks (or could create refill propellant at your destination), that's your return trip's arrival-at-home propellant to serve as radiation shield, and some more docked on the end for your departure home.

I don't understand why all the spin gravity proposals for rigid structures are such "battlestar galactica" items, such as that depicted in "The Martian". Giant rigid structures are totally unnecessary! They always have been! That giant-structure-with-a-centrifuge concept is just another artificial "box" to think inside of. The expense of it has been used as an excuse not to go, for decades now. But it just ain't needed! And nobody yet seems to want to admit that.

GW

Last edited by GW Johnson (2017-08-28 10:15:08)

RobertDyck · 2017-08-28 12:07:19

Well, NASA currently plans zero-G the whole way to Mars. That has all the medical problems of 6 months of zero-G, or worse. Our debate is the best form of artificial gravity. I think we can agree that developing artificial gravity is absolutely critical.

But to push the point, what you describe looks like this:
images?q=tbn:ANd9GcSanICtEZfqFc9fdMZUUBAkSEa2bnhhXGywdhTD3w68afLDg2_b6w

What is the mass, what is the rate of rotation and radius compared to:
71511-img3

GW Johnson · 2017-08-28 13:31:03

Well, what I had in mind is similar to what you posted, but not quite the same. Bigelow developed its B-330 design from NASA's Transhab, yes, but it no longer looks much like Transhab. And I don't need the big nuclear stage, or all that truss stuff that increases inert mass.

Such things will always be heavier than cable-connected structures, but they will always do far more, and be less risky. There is more than just artificial gravity here. I use the propellants as my radiation shielding.

Now the numbers are just best-guesstimates, but they are based on the B-330. What I had in mind is posted over at my "exrocketman" site as the article titled "Mars Mission Outline 2016", dated May 28, 2016. Click on year "2016" in the navigation tool to the left, then on "May". It's the only article I posted that month. The site is http://exrocketman.blogspot.com.

Take a good look at Figures 2 and 3. Figure 2 is B-330 data I gleaned from Bigelow's site at that time. The modifications are two-fold: (1) internal fold-out grate decks on which to stand in the artificial gravity, and (2) more inflatable along the core length, moving the solar panels and heat radiators to the center hard-shell airlock/flywheel module.

Figure 3 shows a two-inflatable with hardshell center, and a four-inflatable with hardshell center. Either of these could be a spinning space station or a spinning crew transfer vehicle. The larger one spins just under the easily-tolerable 4 rpm. The smaller requires some acclimatization to spin at 7 rpm. I based the Mars mission "design" around the smaller one. I say "design" because this is only a feasibility rough-out, not any detail at all.

Figure 4 shows the outbound configurations for the crewed vehicle and the return-propellant vehicle sent ahead from Earth. Ignition configurations are on the right, burnout on the left. I shed a departure stage after leaving LEO, then use the propellant in the periphery tanks for Mars orbit arrival. The propellant tanks sent ahead are for Mars departure and for Earth arrival.

Figure 7 shows the vehicle configurations for returning the crew to Earth orbit. Ignition is on the left, burnout on the right. The tanks mounted on the end are for Mars departure. The periphery tanks are for Earth arrival. I carry a free-return-capable capsule (emergency bailout if Earth orbit return fails), but the baseline design calls for using it only from LEO. The transfer vehicle is intended to be reused on subsequent missions to "wherever". You replenish stores, add loaded tanks, and a departure stage.

Figure 6 shows how I send a lander and its associated propellant supplies to Mars. Three of these get sent ahead along with the crew return propellant supplies, to Mars orbit by solar electric propulsion. That is how I saved mass drastically, eliminating the need for the big nuclear stage or anything like it.

This stuff sent ahead spirals-out from Earth, and spirals-in at Mars, but unmanned equipment and supplies don't care that this is 12-14 months one-way, or that there is radiation in the van Allen belts. The crew goes "fast" by conventional rocket. Every bit of this was NTO-MMH storables, except a LH2-LOX departure stage, and the electric propulsion.

Figure 5 shows basing-from-Mars-orbit, visiting multiple sites by flying each of the landers multiple times. These are single-stage two-way reusable landers, which means they are big, with a small payload fraction. There is no way around that. Half the crew visits a site with the other half in spin gravity in orbit, providing rescue capability with the other landers while doing science-from-orbit. I send three landers so that if one craps out, I can still do the rescue capability thing.

This plan presumes we visit up to 8 sites, about a month at each. It presumes absolutely nothing about ISPP. If that works, then more landings can be made at more sites. After all, there is about a 13 month stay at Mars before the orbits are right for the trip home.

The landers get left in Mars orbit where they can be refueled and used again by a later expedition. The tank empties are left there, too, and could be scavenged for building materials on a later expedition. Only the departure stage and Mars departure tanks are lost. The return tanks are recovered as empties in Earth orbit, along with the crew vehicle.

Nominally, I leave the electric propulsion stages in Mars orbit, but my hunch is these could return unloaded to Earth orbit for reuse. That might be another disposition for the empty tanks in Mars orbit, too. Bring them home for reuse. But I like re-purposing at Mars better.

I need no separate surface habitat. I don’t have any such thing as a “Mars ascent vehicle”. There are no surface treks required “just to get home”. The landers are big and spacious, and can serve a surface crew easily for a month at a time.

It's a 5-vehicle fleet to accomplish this expedition. The crew vehicle is under 800 tons at departure. The return propellant vehicle is under 1300 tons at departure. Each of the three lander/fuel dump vehicles is under 100 tons at departure. That is 2300 tons to send to LEO in order to go to Mars. No one of these is a "battlestar galactica". Even the entire fleet is of reasonable mass at under 2300 tons, given how much it does. And it does one whale of a lot! 2300 tons is less than one Saturn-5 launch weight!!!!

The price I show in Figure 8 presumes ~ $2500/lb ($5-6M/ton) to send these tons to LEO, using no launchers larger than a Falcon-Heavy. Those are current for Atlas-5 and Falcon-9 flying fully-loaded. It presumes that launch costs are ~20% of program cost. That in turn presumes this is NOT done "business as usual" by the usual crowd, though! (And that restriction includes the way NASA itself usually does things, not just its favored contractors.)

GW

Oldfart1939 · 2017-08-29 10:16:31

I stand in full agreement with GW! Maybe a few other nice touches added in, but if NASA hasn't figured out the health issues of zero G yet, they are hopelessly out of touch with reality.

GW Johnson · 2017-08-29 11:13:23

Artificial gravity is required for more than just health issues, as critical as those are. It enables the use of more conventional toilets. It enables the use of conventional laundry. It enables the use of free-surface water cooking, which is far more palatable food, something necessary for crew sanity in long-term isolation. It enables a proper gym. It even enables a vegetable and flower garden.

And don't kid yourself about the isolation, or that we have mastered that issue with ISS experience. We have most definitely not!

One of the things that keeps crews sane for a year or so on any of the LEO space stations is the sight of Earth "right there". Somewhere in the back of your mind, you know you can go home quickly, anytime you need to. That is utterly missing on any deep space flight, to Mars or anywhere else. And the confinement and isolation is multiple years long.

The ship required to keep a crew healthy and sane not only has artificial gravity, it must have a lot of open living space inside, for recreation. I'm not talking about a few dozen cubic meters of volume per person, I'm talking about multiple hundreds. It has to be reconfigurable. There has to be a sort of greenhouse "park" (or at least a vegetable and flower garden) in which to commune with nature. There have to be places to congregate, and places in which to be alone. There have to be facilities in which to pursue hobbies during off-hours. There has to be a big gym.

The dinky crew habitat in the cable-connected scheme (or even the nuke stage / transhab scheme) is none of those things. A crew of 6 living inside 700-1600 cu.m could possibly approach what I propose as necessary. And I arranged all that without "designing" a "battlestar galactica".

Now if a retired engineer like me can recognize the requirements and design to meet them without getting ridiculous, then our vaunted NASA should have been able to do the same thing long ago. They are many, I am only one. That they have not done this for Mars, and never did, proves something.

I interpret that "something" as no real institutional desire to go anywhere else, not since Apollo was cancelled.

GW

Last edited by GW Johnson (2017-08-29 11:18:21)

Oldfart1939 · 2017-08-29 13:44:08

My one time high opinion of NASA has been steadily going in the toilet, and not due to anything written on this forum. What does NASA want? Long term employment stability for doing little or next to nothing. At least with Elon, we have a hard-charger who is forcing hard decisions on them. Unfortunately, the decisions have been the wrong ones (cancellation of Manned Dragon propulsive landings!).

SpaceNut · 2017-08-29 15:44:55

Agreed Nasa has slipped lots down the path of workfare and little else. Even when shuttle was flying we were seeing that they still could but now what have we got is a ride on a Soyuz....
So lets get going with manned fly capability in Boeing's Starliner, and Spacex's Dragon whatever its called but keep fingers crossed as well for Seirra Nevada and its Dreamshaser as well. We want many selects for a good flight rate and not just for a competitive low price.

louis · 2017-08-29 17:00:05

I think we can disagree on that! lol

One thing is clear - space agencies keep all their medical data on surviving in zero G v. close to their collective chest.

The other is that humans have experienced zero G for over a year and performed v. well thereafter with only a v. brief recovery period.

People who think this is huge problem have to argue there is something "weird" about 0.36 G as opposed to 1G. I don't think anyone has ever been able to argue why that should be. With weighted suits people should be able to experience something v. close to 1G. But more to the point - we can check out all these assumptions with simulation journeys to the Moon and even 0.36G tethers in Earth orbit. Then we'll know for sure.

One thing I would say: don't for one moment suppose Musk hasn't thought this through long and hard.

RobertDyck wrote:

Well, NASA currently plans zero-G the whole way to Mars. That has all the medical problems of 6 months of zero-G, or worse. Our debate is the best form of artificial gravity. I think we can agree that developing artificial gravity is absolutely critical.
But to push the point, what you describe looks like this:
https://encrypted-tbn0.gstatic.com/imag … afLDg2_b6w
What is the mass, what is the rate of rotation and radius compared to:
http://www.e-reading.ws/illustrations/71/71511-img3

GW Johnson · 2017-08-30 12:38:42

Louis, I do not share your relatively casual dismissal of the microgravity health issue. The bone density and muscle strength losses are what recover fairly quickly. Those are long-known effects. But, they are NOT the only effects.

The cardiovascular damage is not yet understood well enough to say how well recovery progresses or how fast. The visual acuity damage is a newly-found item. There is no sense at all yet whether there is recovery or how fast any recovery progresses. There is also the newly-found immune system damage, about which we as yet know nothing.

That progression of new discoveries of damage modes suggests that there are still undiscovered effects.

All of our experience for long-term exposures is either at 0 gee or at 1 gee, nothing in between. What we evolved in was 1 gee. Therefore that is the design target for artificial gravity, until and unless we know better. That's just medical prudence talking. And there's no way around it, either.

Not addressing that need is precisely one of the strategies NASA has long used in order not to go to Mars. The dangers of radiation are similarly ignored, and for the same reason: an excuse not to go. Everybody yammers about cosmic rays, but it is the solar flares that are the lethal danger to a crew in space. We know how to shield those, and a plastic-lined thin-aluminum Orion spacecraft hull ain't it. 15-20 cm of hydrogen-rich water or propellant is.

The shield for that brings the slow drizzle of cosmic rays down within long-established radiation exposure limits, even in a peak cosmic ray year. And yet I keep seeing these NASA-funded academic studies in the public news releases that scream otherwise, without any distinguishing between solar flare and cosmic radiation. That lack of such distinction is the clue you need to separate the scare bullshit from the real truth.

There are bed rest studies that offer a poor-but-sort-of-acceptable simulation of some (but not all !!!) 0-gee effects. Because that works at all, we also know that we need not provide 1 full gee on sleeping astronauts. Their beds could just as easily be in the low or zero-gee portion of any ship spinning for artificial gravity.

There are no numbers to guide design, precisely because we have no experience at partial gee. But I think without data or physics to support it, that recreational and dining facilities could be at any convenient level of partial gee, for good beneficial effect, plus a lot of fun. Anything is better than 0-gee, medicinally. Cooking itself might need higher partial gee levels, just to keep the boiling water from jumping out over the edge of the pot. Same probably applies to the splashing water in a clothes washer. (Laundry isn't possible in 0-gee, or it would already be on the ISS.)

Daily work shift stations, and at least part of the gym facilities, should be located at the extreme radii so that full 1 gee is applied for hours at a time. Particularly for weight training, you want the 1-gee, or maybe even a tad more. A lot of the other gym facilities could be in low partial gee, and still be quite effective, without having to do the complicated 0-gee equipment designs. Some recreation in 0-gee should be provided, just for the fun of it.

You cannot do ANY of that effectively in a dinky transhab module, cable-connected or rigidly-connected for spin gravity, regardless of how small your crew is! You need a lot of space spread over much of the length of the ship (or space station) length to accomplish any of this effectively.

That dichotomy between the habitat designs I have seen proposed, and what is actually needed for a proper artificial gravity environment (complete with radiation shielding and the spaces to stay sane) is why I think most of the proposed designs I have seen so far are just egregious bullshit! And I really do mean egregious bullshit!!! WE ALREADY KNOW BETTER THAN THAT! Knowing better, but not utilizing that knowledge without also incorporating the insanities of building "battlestar galacticas", is another strategy used by NASA not to go. All of that falls in the "we're just not yet ready" excuse bin.

What I got when I tried to think it through with all the known requirements was a large habitation volume all along the core of the spinning baton. I wrapped all the propellant tanks and similar stuff around the circumference of the habitation core. That gave me the radiation shielding, because the effective propellant thicknesses exceed 20 cm by far, and a lot of it is hydrogen-rich MMH. The rest is NTO, which has no hydrogen, but does provide some shielding effect anyway, just because N and O are light atoms.

Now that's a different design concept I haven't seen anybody else propose. That's what went into the Mars 2016 article I posted on "exrocketman", as described in post 36 above.

If you do the transits weightless to and from Mars, you incur all the problems of 6-8 months of 0-gee exposure both ways, plus the entirely unknown effects of partial gee exposure for 13 months at Mars. Such a crew will be too weakened to survive the high-gee bailout or direct return at something like 3 minutes peaking at 12-15 gees.

If you use artificial gravity near 1 full gee for these transits instead, you have a healthy crew to withstand 13 months at 0.38 gee, whatever those effects are at Mars. And you have a healthy crew with 6-8 months recovery at 1 full gee to survive whatever return they have to execute at home.

There is simply NO comparison between those two scenarios as to which is the wiser course! And I have identified and published the best way yet to incorporate this artificial gravity and radiation shielding into manned spacecraft design.

Why are we still talking about this?

GW

Last edited by GW Johnson (2017-08-30 16:59:14)

Oldfart1939 · 2017-08-30 14:10:38

At one time about 10 years ago, I was under the illusion that microgravity only had bone decalcification related issues. More recent discoveries from the ISS astronauts indicate that the cardiovascular system undergoes similar degradation. That has a secondary effect on the visual system. With all respect to Bob Zubrin and his tether ideas, the production of artificial gravity needs to be refined in some manner as proposed by GW. This means we need to extend our thinking beyond Dragon capsule sized vehicles. Some sort of "space baton" seems to offer the best solution. In any event, we're forced to include orbital assembly of the Mars vehicle in the "new and improved" Mars Direct architecture.

Last edited by Oldfart1939 (2017-08-30 14:15:34)

louis · 2017-08-30 19:00:47

I am not trying to downplay the serious challenge of microgravity. But I think I am suggesting people are exaggerating the risks. Polyakov is the record holder for duration in zero G...he walked unaided to his reception chair on arrival back on Earth after 14 months in space. He achieved the record when he was in his fifties.

https://en.wikipedia.org/wiki/Valeri_Polyakov

He's now 75, and like most astronauts doesn't seem to have suffered any long term impairment from his time in space. His record dates back over 20 years - space medicine and space exercise must have improved since then.

The point I would make is that we wouldn't simply risk everything on a throw of the dice. We would run pilot studies using the Moon as a stand-in for Mars...give them 8 months in space and then see if their bodies can recover well using weighted suits on the moon.

SpaceNut · 2017-08-30 21:44:09

The research might not be complete but its full of tells. Weightlessness affects health of cosmonauts at molecular level

Proteins are key players in the adaptive processes in an organism, so the scientists decided to focus on them. To gain a deeper understanding of the changes in human physiology during space travel, the research team quantified concentrations of 125 proteins in the blood plasma of 18 Russian cosmonauts who had been on long-duration missions to the International Space Station.
The blood was initially taken from them 30 days prior to their flights, and again immediately after their return to Earth and finally seven days after that. This timing was chosen as it helped the scientists to identify trends in protein concentration changes and see how fast the protein concentrations returned to their normal levels prior to the flight.

Oldfart1939 · 2017-08-31 05:47:09

Louis-

What we don't really understand is how the human--or any animal's---physiology even detects the absence of gravity. Is there a "gravity receptor," or are the effects individually responses to the absence of the stimulus? The issue of making the Mars journey less stressful is important, and minimizing the issue intellectually doesn't help. One of the architectures I conceived earlier was in many respects almost identical to that which GW has suggested. The first question to be answered is whether the "baton-like" structure should be sent tumbling end over end, or with the axis of flight be perpendicular to the axis of module rotation. It would seem reasonable for the end over end tumbling to have fewer complications w/r to midcourse corrections. The spacecraft design in The Martian seemed to show the axis of bicycle wheel rotation being the line-of-flight, however.

Regarding protection from Solar Flare Radiation was initially addressed by Zubrin by using the food and water supply. I would consider enhancement by incorporation of significant HDLPE in the internal structure of the spacecraft. HDLPE = High Density Linear Poly Ethylene, which is a hydrogen-rich polymer of adequate physical properties for structure. My thought was having individual "Bunk cocoons" for the crew, with all the structure being composed of the HDLPE with maybe a water mattress included. Stack several bunks atop one another all with water mattresses would undoubtedly serve to attenuate the solar flare radiation exposure. Radiation can certainly never be completely eliminated, but CAN be adequately attenuated.

GW Johnson · 2017-08-31 10:07:00

The vision impairment doesn't seem to affect everybody the same way. The as-yet unproven hypothesis is that eyeball shape responds to the gradient of internal bodily pressures induced by sitting and standing in gravity. Its absence induces changes of shape in the eyeball, in turn affecting visual acuity. The truth is probably far more complicated, especially since we sleep prone. Point is, they don't understand this effect, they just know that it is real. And variable.

They as yet have little or no hypothesis to test, regarding microgravity damage to the immune system. Something about this affects detailed biochemistry in ways that are still unknown to us. Not understood, but known to be real. And variable.

The fluid pressure gradient (or its absence) has something to do with the known effect of cardiovascular damage (there are more effects in this classification than just weakened heart muscle, by the way). The truth is probably far more complicated than that, as not every person responds the same way. The juries are still out on this, as well as on the other two.

These are serious unresolved issues with long-term exposure to microgravity, no one can sanely dispute that.

Polyakov was exposed for 440 days in one stretch, slightly over one year. The journey to and from Mars by min-energy transfer is nearly 2.5 years (actually 29 months) long. 16 of those months are in zero-gee, the other 13 at 0.38 gee partial gravity, if wholly spent on the surface.

If you spend the transit times at zero gee, you are betting the lives of the crew on two things, one known, the other unknown: (1) it is ENTIRELY UNKNOWN whether 0.38 gee is therapeutic enough to counter 8 months of microgravity exposure, before another 8 months exposure coming home, and (2) it is reasonably certain that a crew weakened by 8 months (or more) microgravity exposure cannot withstand a 12-15 gee free return at Earth.

Their weakened hearts will quit under that kind of stress. A 3-5 gee return from LEO is survivable. Higher return gee is very likely not. Apollo from the moon was 11 gee, but the exposure was only 2 weeks. Apollo is NO guide to success with this issue.

All that being said, simple prudence and basic human ethics both say "spin the damned ship for gravity during the transits". Minimize the possible effects of the unknowns as best you can. The basic physics for this has been known, since the very first spinning space wheel space station designs appeared in 1937.

More was unknown back then, but they came to the very same conclusion for the very same reason as applies today. We evolved at 1 gee gravity. We should continue living in it, to the greatest extent possible, to stay healthy in space. Space is hostile enough without running microgravity risks, too.

It really is that simple. And that hard. Except that my ship design concepts show that it really isn't all that hard to do. Not nearly as hard as was feared.

GW

GW Johnson · 2017-08-31 10:26:58

NASA's own radiation exposure website lists the criteria applied to astronauts, which are roughly twice the exposures allowed for nuclear workers, and about an order of magnitude higher than what is thought to be OK for civilians.

There is a limit of 25 REM (radiation equivalent man, rads multiplied by an effectiveness factor) accumulated in any given month, and a limit of 50 REM accumulated in any given year, plus a career limit that varies with age and gender. But for older men and women, this career limit maximizes as 400 REM accumulated over a lifetime. How those convert to Sieverts, I dunno. Just units of measure.

For the region near Earth's orbit, the cosmic radiation dose varies with the sunspot cycle more or less sinusoidally, between a minimum 24 REM per year to a maximum 60 REM per year, on an 11 year cycle. This is a steady slow drizzle, not fitful bursts, of extremely penetrating extreme-energy particles. Any sort of shielding effective for solar flare radiation cuts this cosmic ray dosage a little, more or less to 50 REM from 60 REM, or at the low point, to 14 REM from 24 REM. If you've done your job protecting crews from solar flares, cosmic rays are just not a lethal threat.

Solar flare radiation is far less energetic, which makes shielding far more feasible. It just comes erratically in huge amounts, very much like the brief but intensely-lethal quantities of radioactive fallout after a nuclear weapon detonation. The figure of merit that adequately shields a crew from an event like the 1972 flare between Apollo missions is 15-20 cm of water. Water is hydrogen-rich, yes, but also contains the light atom oxygen, so other light atoms should not be discounted for their shielding effect. It just might take a few more cm of them. Flares are hours long, at 100's to 10,000's of REM per hour. Without shielding, death is certain, within hours. It's an ugly death, too. 300-500 REM accumulated over a few hours is the usual sort of figure of merit for a lethal dose.

The design I proposed for the spinning baton artificial gravity ship clusters the propellant tanks around the circumference of the habitation core. That way you have a variable-thickness shield about you, made of the propellants. Most of the propellant mass is NTO, which has some shielding effect. The rest is MMH which is quite hydrogen-rich. These tanks are around half a meter to a meter diameter. Even with the leakage between tanks, there should be plenty of shielding effect.

No need for adding great masses of plastic or building thick (25+ cm) aluminum hulls. Use what you already have to have, anyway, as your shielding material. These propellant tanks, plus some water and wastewater tanks associated with the life support, should make a very effective shield indeed. (Frozen food stores are another really good shielding material.)

I'd put the best shielding about the flight control station, so that critical maneuvers could be flown regardless of the solar weather. You can't de-spin and make an arrival burn if you are cowering in the bathroom behind the toilet tank, or hiding in the frozen food locker, waiting out a solar flare. Impulse timing is everything in orbital mechanics.

Not paying attention to this is a needless way to kill a crew. And as I have already shown, it is not very hard to meet this requirement without building "battlestar galactica".

GW

Last edited by GW Johnson (2017-08-31 10:36:52)

RobertDyck · 2017-08-31 13:08:51

REM and Sievert calculate effectiveness differently, but a practical conversion is 1 REM = 1 centi-Sievert. So 1 REM = 1 cSv, or 100 REM = 1 Sv.

louis · 2017-08-31 16:42:58

Everything affects health at a molecular level. Climbing a mountain does. Spending several weeks in a submarine does. Piloting a jumbo jet for 20 years does. The issue is to what extent is ability to function physically and mentally affected. I am maintaining the answer is "very little" for those people who are specially selected who then follow fully the exercise and medicinal regime.

SpaceNut wrote:

The research might not be complete but its full of tells. Weightlessness affects health of cosmonauts at molecular level

Proteins are key players in the adaptive processes in an organism, so the scientists decided to focus on them. To gain a deeper understanding of the changes in human physiology during space travel, the research team quantified concentrations of 125 proteins in the blood plasma of 18 Russian cosmonauts who had been on long-duration missions to the International Space Station.
The blood was initially taken from them 30 days prior to their flights, and again immediately after their return to Earth and finally seven days after that. This timing was chosen as it helped the scientists to identify trends in protein concentration changes and see how fast the protein concentrations returned to their normal levels prior to the flight.

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