Musk's plans for Mars

GW Johnson · 2016-06-14 14:24:10

In government contracting, what should be, and what is, have been two very different things, since before the civil war. It's gotten really, really bad starting after WW2.

Spacex has to "get along" dealing with a totally corrupt system, when dealing with NASA. Fortunately, they also get a lot of income from the private launch business. So NASA isn't their only source.

Soon they will add USAF to their sources, although that procurement system is the same old corruption as NASA's, just run out of different offices.

As long as there are private monies to be had from lobbyists and political groups, our government will be hobbled with this evil. That's an uncorrected mistake still around from the founding of the Republic.

GW

Last edited by GW Johnson (2016-06-14 14:27:23)

Tom Kalbfus · 2016-06-14 17:06:25

Corruption is a substitute for hard work, it just so happens that SpaceX does the hard work, and makes money by providing a superior product rather than by bribing someone for exclusive access.

elderflower · 2016-06-21 03:48:29

wherever it is placed, it needs to be away from steep slopes as they could be subject to landslips and cliff falls. These may be triggered by human activity and must not result in burying of the base.

Tom Kalbfus · 2016-06-21 06:51:17

elderflower wrote:

wherever it is placed, it needs to be away from steep slopes as they could be subject to landslips and cliff falls. These may be triggered by human activity and must not result in burying of the base.

Huh? What?

Rxke · 2016-06-21 07:27:17

Tom Kalbfus wrote:

elderflower wrote:
wherever it is placed, it needs to be away from steep slopes as they could be subject to landslips and cliff falls. These may be triggered by human activity and must not result in burying of the base.
Huh? What?

Terraforming, I presume.

This will lead to increased weathering.

RobertDyck · 2016-06-21 11:45:41

Is he worried of a landslide destroying a human base/habitat? Actually a relevant question.

I was part of the Mars Homestead Project, phase 1 - Hillside settlement. Location was chosen where water ice is known: side of canyons at mid-latitude. Bruce Mackenzie wanted to use bricks made of Mars regolith, and pile regolith on top to provide weight to counter air pressure. We need regolith anyway for radiation shielding, but his brick idea needs more. So we chose to use a skid-steer loader or mini-track loader to dig out a section of hillside, floor level with the valley floor. Build the base in that cut, then use the loader to push regolith down from the hill onto the base to bury it. So we never have to lift dirt regolith up, just down. An architecture student working on his masters degree at MIT helped us; our project was his thesis.

You do have to ensure a landslide won't destroy the base. In this case the habitat is buried, but greenhouses and a lot of industrial stuff are outside.

Last edited by RobertDyck (2016-06-21 12:37:46)

elderflower · 2016-06-21 12:25:33

Landslips are widespread on Mars eg in Canyons and in craters, and I suppose that many slopes are at the limit of stability and their fall could be triggered by activities involved in construction or exploration. The base may be destroyed or just buried and rendered inaccessible. It's just a consideration when selecting base sites and targets for examination.

SpaceNut · 2016-06-24 20:14:36

Musk will need to do more than provide a cheap ride for crew or cargo as its going to need a ship for the deep space trek to mars, the ability to get better than ISS closed loop effiency and a low mass power source for the base after a good indepth investigation of the perfect site....

GW Johnson · 2016-06-25 08:30:16

If one can jettison the mental straitjacket of lowest-possible launched mass, then one finds fairly quickly that there is actually an advantage to imperfect life support recycling.

There is a reduction of total deadhead mass at each burn after the first burn in the mission, if recycling isn't perfect, and waste mass gets jettisoned between burns. This reduces the mass ratio and velocity increment enough at each burn that overall the vehicle is actually smaller than you would have thought it would be.

That's just the nature of the exponential math. And it made a rather large difference in initial departure weight for the manned vehicle in my latest mission concept. That one is "Mars Mission Outline 2016" dated 5-28-16, posted over at http://exrocketman.blogspot.com

The landslide thing is sort of common on Mars. That may well restrict the initial facilities to items that can be built out on a flat spot away from the hazards. It certainly is worth worrying about.

Once there is a facility that is to be permanently manned (even if crews rotate out), we may well know enough to recycle wastes better, by means of fertilizer in the garden or greenhouse. I would recommend trying that again down here before we bet lives on it out there. The last great experiment along those lines failed (that closed cycle ecology thing out in Arizona).

That is something Musk will have to have in place as he constructs his "permanent city" on Mars. Otherwise, it cannot be permanent.

GW

Tom Kalbfus · 2016-06-25 15:13:06

SpaceNut wrote:

Musk will need to do more than provide a cheap ride for crew or cargo as its going to need a ship for the deep space trek to mars, the ability to get better than ISS closed loop effiency and a low mass power source for the base after a good indepth investigation of the perfect site....

You mean a low mass that is brought over from Earth, those structures that are made of Mars itself are an exception. One way to collect solar energy, for instance is with large mirrors that track the Sun. So could mirrors be made out of local materials? How about photovoltaics, could those be made locally? even if they are inefficient, if they are made on Mars, we can make more of them to make up the difference. I think 3-d printers are the key, if they are low mass and we can bring them to Mars, and then use them to make things out of Mars that are useful, then we don't have to bring those things from Earth.

SpaceNut · 2016-06-26 20:40:42

GW I got looking at the artifical gravity and time spent if we do not have it and here is the data:
Physical Activity in Space
Effect of Prolonged Space Flight on Human Skeletal Muscle (Biopsy) - 07.15.15

Science Results for Everyone
Maintaining strong muscles is a big enough challenge on Earth. It is much harder to do in space where there is no gravity. Calf muscles biopsies before flight and after a six months mission on the ISS show that even when crew members did aerobic exercise five hours a week and resistance exercise three to six days per week, muscle volume and peak power both still decrease significantly.

That is a large amount of time to gain back for other things on a mission.....

GW Johnson · 2016-06-27 08:08:08

Well, a crew waiting out months of travel needs something to do, and that could be exercise. What the studies show is that few-to-several hours of exercise every day are required to stay reasonably fit for a 6 month stay on the ISS. It's less effective at 1 year, and we have no data beyond 440 days (and that's only one cosmonaut).

I think reduced gravity may have some therapeutic effects, but it simply cannot be as good as full gravity. It'll fall somewhere in-between 1 and 0 gee. It has to. Some of us think it will almost as good as full gee, others think it will be about as bad as zero gee. Point is, nobody knows. When you do not know, prudence demands you assume the worst.

There are weightlessness effects beyond muscular strength, bone density, and cardiovascular health. Vision problems and immune degradation are but two discovered so far. You can bet there are more effects we simply have not discovered yet.

The first 3 paragraphs of this posting taken together are a pretty compelling argument all by themselves to provide spin gravity on deep space flights. Not to mention that gravity lets you do free-surface cooking, bathing, and laundry. Plus most of our sewage handling technology depends upon gravity. So many advantages!

If you spin the vehicle for gravity, why not oversize and over-spin it just a little? Put the gymnasium equipment in the space furthest from the spin center, where the gravity is actually a little over one gee. Make your exercise that much more effective. Cut so much exercise from your work schedule, and do more deep-space science while on the trip, while staying fully healthy. An interplanetary vehicle can serve as a temporary space telescope, among other things.

My final point is: a free-return scenario from Mars is an above-escape-speed entry, at something like 16-17 km/s interface speed. We used an 11 gee ride coming home from the moon right at escape velocity (11 km/s). This is likely a 12-15 gee ride coming home from Mars, quite unlike the 3-4 gee ride coming home from ISS. Astronauts whose health is degraded by microgravity damage will be unlikely to survive this.

That health degradation demonstrably occurs in weightlessness, despite the exercise regimen! It is way past time to face up to that inconvenient little fact of life.

GW

RobS · 2016-06-27 17:26:21

I agree, GW, that even Martian gravity is likely to be problematic. In my Mars novel, people have special pockets in some of their clothing where weights can be inserted. Children hate it. That might get one up to an effective gee of 0.6 from Mars's almost 0.4. At that point, one is accelerating and decelerating an additional mass equal to half your body, so your bones aren't getting as much as they should get, but your muscles are forced to work more than they would on Earth.

There are also exercises to use. Jumping up and down stresses your bones maximally, so I can imagine they'd be used a lot. In my Mars novel, people have settled in caves carved out of the ice crust of Titan and the floors of these caves are 100 or 150 meters below the Titanian surface. There is a spiral staircase to the top of the cavern and people jog up. If they are pretty fast, they can get their effective gee up to 0.5 or so.

I fly people to Mars in large passenger vehicles able to transport several hundred at once shaped like flattened space capsules; think of them as pancakes or pizzas with a curved heat shield bottom for aerobraking. They rotate for centrifugal gravity and have corridors that go all the way around. Sometimes one can use them for jogging. I don't remember the diameter I used, but consider a vehicle with a 50-meter radius. Zubrin in Case for Mars, page 135, gives a formula for centrifugal gravity: F = 0.0011 W2R where F is gravity in terrestrial gees, W2 is spin rate in revolutions per minute squared, and R is the radius. Let us say this 50 meter vehicle rotates three times per minute; that produces 9 x 50 x .0011 = 0.4 gees (Martian gravity). If you jog in the direction of the rotation at 6 miles per hour (that's 3 meters per second) you are going around the entire circumference in a bit less than a minute. So think of this as 4 rpm instead of 3 rpm; because of your speed jogging, you are experiencing 16 x 50 x 0.0011 = almost 0.8 gees (double Martian gravity!). So jogging in the same direction as the rotation can make a big difference!

Eight tenths of a gee may be close enough to terrestrial normal, too. Consider this: I am 5 foot 10 inches (175 cm). My ideal weight is about 170 pounds (77 kg) but I really weigh 203 (92 kg) and I have weighed as much as 235 (107 kg). The latter number is 38% too much. My bones can handle that whole range, and probably would be okay if my weight were 150 lbs (68 kg). So the skeleton and heart can handle a certain range. Of course, many women in the 50s and 60s, even if they are a bit overweight, get osteoporosis, which is basically the problem in zero gee. The medication to counter osteoporosis is still not very effective.

GW Johnson · 2016-06-27 17:34:47

"There are weightlessness effects beyond muscular strength, bone density, and cardiovascular health. Vision problems and immune degradation are but two discovered so far. You can bet there are more effects we simply have not discovered yet." -- post 87

Is it not simpler and more direct to just provide 1 gee+ spin gravity? Why risk all the unknowns? This makes no sense to me. Just because it is more convenient to ignore, does not make this issue ignorable. Convenience be damned!

GW

RobS · 2016-06-27 17:38:31

I agree with you, for space vehicles. I designed my space vehicles without knowing about the problems with the eyes and the immune system. But it'll be a lot harder on Mars and the moon where centrifugal gravity will be at right angles to the natural gravity. It may be that artificial habitats off any planetary surface will provide humans the best environment.

GW Johnson · 2016-06-27 17:49:22

Hi Rob:

Ultimately, we will eventually find that rotating space habitats will be more practical than anything we could ever build on any of the planets or their moons. But, it will take centuries before this lesson is actually learned.

GW

SpaceNut · 2016-06-27 19:16:11

The greatest of reasons for artificial gravity and why Musk must make a ship to meet the goal and not just a capsule....Sure the Mars colonial transport sounds like that might foot the bill but there are not enough details as of yet to be sure that the goal will be met.

GW Johnson · 2016-06-28 09:04:41

What little I could find on the internet about Musk's MCT plans indicated he has not yet decided whether he needs to provide artificial gravity for folks travelling one-way to Mars. I think he is still waiting to follow NASA's lead on this. And as y'all know, I think NASA has its official head up its collective rear on the artificial gravity issue.

The MCT "ship" appears to be (at least conceptually) the upper stage of his giant rocket, to be refueled on orbit before departure to Mars. There was talk about it carrying individualized containers for the occupants, to be off-loaded once down on Mars. Sort of like the spacegoing equivalent of an Earthly container ship on the high seas. There are no solid data on the geometry by which to judge how artificial gravity might or might not be incorporated into the design.

The rest of the idea seems to be to use propellant manufactured on Mars to refuel the thing for the trip home. It'll have to fly relatively unladen, in order to have the mass ratio to ascend, escape Mars, and capture at Earth for the next trip. That is, if he intends to reuse them at all. None of this is set in stone, however. Maybe we'll see more at the September meeting where he is supposed to describe some more about this plan.

Right now all we have is a few hints and a lot of speculation. The most solid hint we have is really just the announced intentions to start sending stuff one way to Mars at every opposition, followed by men about 2025.

GW

Last edited by GW Johnson (2016-06-28 09:08:28)

Tom Kalbfus · 2016-06-28 09:25:06

What of you get two capsules tethered together by a cable and rotate them. What's so hard about that? I hear a Gemini mission with Neil Armstrong aboard once did that accidentally, but with a much shorter spin radius.
https://en.wikipedia.org/wiki/Gemini_8

GW Johnson · 2016-06-28 09:36:06

There was no cable on Gemini 8. That capsule was docked to an Agena target vehicle. A stuck thruster spun them up so fast it nearly tore the Gemini apart before Armstrong got it under control. They undocked and came home immediately, since virtually all their thruster propellant was depleted, and they used the last of it during reentry.

Many propose cable-connected spin gravity. There is a very serious dynamical complication with cable systems: "you cannot push on a string". It severely limits what you can do to spin up and spin down, and it even more severely limits what disturbances you can handle. Unless you use multiple cables (an entanglement risk) then you automatically incur the single point failure mode of a broken cable killing your crew.

I'm not a fan of cable-connected spin systems.

Wheels are just too big and expensive. Truss-connected things have enormous inert weight fractions. I'm not a fan of those ideas, either.

The only thing that makes sense to me is the baton shape spun end-over-end, made up of modules you have to have anyway. Being at least a semi-rigid object, there's easier start-stop dynamics (you can use flywheels instead of thrusters!), and you are far more tolerant of disturbing forces.

GW

Tom Kalbfus · 2016-06-28 10:20:49

GW Johnson wrote:

There was no cable on Gemini 8. That capsule was docked to an Agena target vehicle. A stuck thruster spun them up so fast it nearly tore the Gemini apart before Armstrong got it under control. They undocked and came home immediately, since virtually all their thruster propellant was depleted, and they used the last of it during reentry.
Many propose cable-connected spin gravity. There is a very serious dynamical complication with cable systems: "you cannot push on a string". It severely limits what you can do to spin up and spin down, and it even more severely limits what disturbances you can handle. Unless you use multiple cables (an entanglement risk) then you automatically incur the single point failure mode of a broken cable killing your crew.
I'm not a fan of cable-connected spin systems.
Wheels are just too big and expensive. Truss-connected things have enormous inert weight fractions. I'm not a fan of those ideas, either.
The only thing that makes sense to me is the baton shape spun end-over-end, made up of modules you have to have anyway. Being at least a semi-rigid object, there's easier start-stop dynamics (you can use flywheels instead of thrusters!), and you are far more tolerant of disturbing forces.
GW

How can cables get tangled. Lets say there are four cables, much like a swing set you might have played with as a child. The swing would go back and forth, and sometimes some devious kid would twist the swing just to make things interesting. What would the swing do after you twisted it? It would unwind. Since the four points up top would be lined up with the four points on the bottom, if you twisted this swing, the tendency would be for the swing to unwind until the original state was restored. I think the same would happen between to capsules held together by four cables. The get twisted, they would unwind. Thrusters would spin it up. with four or more cables you would have some stability.

GW Johnson · 2016-06-28 11:10:02

I get that from a lot of folks, nearly all of whom have never, ever done any sort of rigging with ropes, cables, or chains (I actually have). The universe is not uncaring, it is malevolent. Cables, ropes, and chains always tangle. They always have and they always will. They will find a way to screw up no matter how carefully we try to rig.

Things don't just happen to us in the trite little scenarios we imagine (which exception is exactly what happened to Gemini-8 and to Apollo-13, by the way). Very complicated ugly stuff is what gets thrown at us. It is better not to add to our vulnerabilities, if at all forseeable.

Tangled and broken cables are quite forseeable, based on the experiences of all sorts of marine and construction riggers here on Earth. That doesn't stop us from rigging, but we expect trouble when we do it, and we are prepared to deal with it, knowing it might be disastrous, even if unlikely.

For example, imagine a little frayed spot on one of your 4 cables (there for any reason at all, including a micrometeroid strike). Now some mischance causes a twisting action, and the 4 cables twist together. The frayed wires trap the adjacent lines so that they are prevented from untwisting when you fire opposite thruster. Now what do you do? Good question.

When the cables unexpectedly jam during the untwist spin, the resulting off-center unexpected force tumbles one or both capsules, which then flip over between adjacent cables, perhaps multiple times, effectively braiding them. Now what do you do? Even better question.

None of that ever can happen, with a rigid or semi-rigid structure. Prevention is 99% of cure.

GW

Last edited by GW Johnson (2016-06-28 11:22:01)

Tom Kalbfus · 2016-06-28 12:35:07

GW Johnson wrote:

I get that from a lot of folks, nearly all of whom have never, ever done any sort of rigging with ropes, cables, or chains (I actually have). The universe is not uncaring, it is malevolent. Cables, ropes, and chains always tangle. They always have and they always will. They will find a way to screw up no matter how carefully we try to rig.
Things don't just happen to us in the trite little scenarios we imagine (which exception is exactly what happened to Gemini-8 and to Apollo-13, by the way). Very complicated ugly stuff is what gets thrown at us. It is better not to add to our vulnerabilities, if at all forseeable.
Tangled and broken cables are quite forseeable, based on the experiences of all sorts of marine and construction riggers here on Earth. That doesn't stop us from rigging, but we expect trouble when we do it, and we are prepared to deal with it, knowing it might be disastrous, even if unlikely.
For example, imagine a little frayed spot on one of your 4 cables (there for any reason at all, including a micrometeroid strike). Now some mischance causes a twisting action, and the 4 cables twist together. The frayed wires trap the adjacent lines so that they are prevented from untwisting when you fire opposite thruster. Now what do you do? Good question.
When the cables unexpectedly jam during the untwist spin, the resulting off-center unexpected force tumbles one or both capsules, which then flip over between adjacent cables, perhaps multiple times, effectively braiding them. Now what do you do? Even better question.
None of that ever can happen, with a rigid or semi-rigid structure. Prevention is 99% of cure.
GW

What if you place spacer rings in between the cables at various lengths to keep the parallel? Elevators seem to function okay when suspended by cables. and two capsules held at a fixed distance by spin a cables are a lot like elevator cars, except they don't go up and down.

You know suspension bridges are held up by cables as well, have you ever seen any of those cables get twisted? I haven't.

Last edited by Tom Kalbfus (2016-06-28 12:36:05)

GW Johnson · 2016-06-28 13:18:26

Elevators are a very well-contained, very isolated case. That's why there have been no more problems with them than there have been. And there have been problems. I've seen one, up close and personal.

As for cables tangling on a suspension bridge, yes, I have seen such a thing. It wasn't causal to anything (fortunately), but it did happen.

Murphy's Law says if it can happen, it will happen. Engineers like me are strong believers in Murphy's Law. And for very good reasons.

Neither of those examples you cite are as wide-open and vulnerable to problems, as are two objects spinning in space, connected by cables.

Suffice it to say I would not bet my life on cable-connected spin gravity.

I would bet my life on a Paul Webb MCP prototype spacesuit, but not on cable-connected spin gravity. I know the risks and the odds. And I know Murphy's Law.

GW

RobS · 2016-06-30 13:40:50

Here's a great substance to know about: ammonium carbonate, (NH4)2CO3 . It's a white solid up to 50 Celsius. It has all the major elements life needs: carbon, hydrogen, nitrogen, and oxygen. It breaks apart into ammonia, carbon dioxide, and water. And they have found it on Ceres! Both space.com and spacedaily.com have articles about it. It's one of the substances that makes the bright spots bright. Apparently they are mainly sodium carbonate, not Epson Salts as previously thought.

Since all the elements in ammonium carbonate are small atomic number, I bet it'd make decent shielding against cosmic rays, too. It might be a useful substance to ship, if a colony off-world wants volatiles.

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