Easier way to get to Mars and back to moon...

[cosmictotem]

In post 41, you suggest 40,000 biospheres in the first circular orbit, at about 1AU from the sun. You have also suggested that they each house 100,000 people and be sized like there largest stadiums.

These "stadiums" will need to be enclosed in spherical mass shells, for protections from cosmic rays. For life time long protection these shells will need to be at least 30 meters (40 feet) thick. So my most important "remaining objection" is the one i've already asked at least 4 times now:

Where does all this mass come from?

Here is how to estimate it:

If R is the mean radius of the 40 foot thick spheres and we call pi = 3.14 then the surface Area of the spherical shells is A= 4x3.14R^2 and the Volume of mass in each is V = TxA, where T is the Thickness of the mass shell.

For good shielding, the average density of the mass should be more than that of water. You would want the outer most layers to be lead, to convert each high energy cosmic ray into a dozen or more "daughters" of lesser energy, which could be converted into more than 100 still lesser energy "grand-daughters." The material doing this could be only half as dense as lead. Finally, the two innermost layers should be even lower density. Innermost is mainly carbon as the 10,000 great, great grand daughters of each primary ray need to collide with modest weight atoms - best for "sucking" energy out of them with the struck atom's recoil. The layer next to the carbon layer should have about twice the density of water. The overall density of the shell, averaged, would be more than 3 times that of water, but I'll call it 3. If we work in feet (water is 64 pounds/ ft^3)

So the mass of your 40,000 bioshells is 40,000x3x64x4x3.14xT(R^2) =32,153,600T(R^2) pounds where both T & R are given in feet. If T = ~31 feet (probably to little, but makes for nice round number.) I. e. 1,000,000,000R^2 pounds. I think R must be at least 1000 (length of 10 foot ball fields is very small to cram 100,000 people inside) then here it the weight, of just the innermost of a set of rings between Earth and Mars: 1,000,000,000x1000x1000 pounds or in scientific notation: 1E15 pounds. That is about equal to taking the top layer half a mile deep from all the dry land parts of the earth. Doing that might reduce the dry land to only 80% of the present area.

So again, for the fifth time, where will you get all the needed mass, just for the cosmic ray shield? (and then more for the rest of the biosphere)?

Also, note that the area growing food for 100,000 people can't be inside the opaque (no sunlight) bioshield. Perhaps some fungus growing outside can survive bombardment by cosmic rays, but I doubt it. This is the 2nd problem I would raise.
Facts are very ugly enemies, arn't tthey.

Didn't I address this objection using potential advances in cellular maintanence and rejuvenation? In other words, injured cells could be periodically replaced with healthy cells generated in internal rooms which are smaller versions of your spheres with 40 foot thick walls. (See Aubrey de Grey for a rundown of coming advances in human cellular maintenance).

As for the food, well, if solar panels are used to collect light, the plants could be placed in opaque rooms fitted with LED lighting. But I see your point of having to enclose the plants in large rooms. But again, if we can master cell maintanence in humans, it's foreseeable we could do it for plants, raise them in smaller rooms, then bring them out later to the large exposed farms.

But, as our cells would be periodically replaced with healthy cells, it doesn't really matter if we are eating plants exposed to some radiation, does it? We'll just replace those sick cells with healthy ones generated in those much smaller protected rooms I suggested.

Additionally, haven't scientists proposed hydrated plastic as an alternative shielding?

 

[billvon]

So are you saying most docking in science fiction is highly oversimplified or the true physics involved is generally ignored?

Generally glossed over.

Note that once you have matched speeds AND are within a few meters, then it's pretty simple; driving towards the target results in you getting closer. But if you are farther away it's a lot harder. Let's say you are chasing a space station a few hundred miles behind it. You fire your engine to accelerate towards it. You are now going faster, and so you start rising into a higher orbit. Higher orbits are slower, and thus you end up moving AWAY from the station.

So if you are inexperienced, you might boost towards the station. Then you'd rise above and behind. That might make you want to fire your engine to drive you down - which would put you in front of the station. Then you might fire backwards, towards the station. That would put you below. If this goes on for a while, you end up flying circles around the station. Early Gemini astronauts fell victim to these mistakes. Mike Collins called the resulting spiral-looking flight pattern a "whifferdill."

 

[Russ_Watters]

So are you saying most docking in science fiction is highly oversimplified or the true physics involved is generally ignored?

The true physics is generally ignored.

In particular, propulsion (fuel), mass, acceleration, velocity and gravity are all ignored. It is like they are in a big swimming pool and can easily move around between different places, without using a noteworthy amount of fuel. It just isn't that way.

A good movie discussing the real physics (because it is real) is Apollo 13. They had a choice to turn right around and go home or fly around the moon and they flew around the moon because it was easier/safer. The decision making process and physics are discussed in the movie.

 

[DaveC426913]

Note that once you have matched speeds AND are within a few meters, then it's pretty simple; driving towards the target results in you getting closer. But if you are farther away it's a lot harder. Let's say you are chasing a space station a few hundred miles behind it. You fire your engine to accelerate towards it. You are now going faster, and so you start rising into a higher orbit. Higher orbits are slower, and thus you end up moving AWAY from the station.

So if you are inexperienced, you might boost towards the station. Then you'd rise above and behind. That might make you want to fire your engine to drive you down - which would put you in front of the station. Then you might fire backwards, towards the station. That would put you below.

Forward takes you out.
Out takes you back.
Back takes you in.
In takes you forward.

That was a mantra learned by the denizens of the zero-g orbital environment called the Smoke Ring in Larry Niven's Hugo and Award winning The Integral Trees.

 

[cosmictotem]

Forward takes you out.
Out takes you back.
Back takes you in.
In takes you forward.

Sounds like space is skitzoid.

 

[cosmictotem]

Generally glossed over.

Note that once you have matched speeds AND are within a few meters, then it's pretty simple; driving towards the target results in you getting closer. But if you are farther away it's a lot harder. Let's say you are chasing a space station a few hundred miles behind it. You fire your engine to accelerate towards it. You are now going faster, and so you start rising into a higher orbit. Higher orbits are slower, and thus you end up moving AWAY from the station.

So if you are inexperienced, you might boost towards the station. Then you'd rise above and behind. That might make you want to fire your engine to drive you down - which would put you in front of the station. Then you might fire backwards, towards the station. That would put you below. If this goes on for a while, you end up flying circles around the station. Early Gemini astronauts fell victim to these mistakes. Mike Collins called the resulting spiral-looking flight pattern a "whifferdill."

Fascinating stuff. My concept of space I think just evolved from one of a continuous ocean to one of concentric slices or sections. I don't know why ignore that fact. Everyone was told this in grade school

 

[Billy T]

... Additionally, haven't scientists proposed hydrated plastic as an alternative shielding?

Yes that is the inner most carbon layer I spoke of. The outer most layer must be a high atomic number material. Gold would be good but lea is more economical. Its function it to have a primary ray strike the nuclus, which has about a hundred particles (neutorns and protons) splattering them into a dozen or so lower atomic nunber pieces. - that can make a dozen "daughters" with much lower energy. As I noted, the innermost layer is low atomic number - Plastic is good as carbon is the highest atomic number and there is lots of hydrogen it. The great, great, great grand daughters slam into those nucli and make them recoil - good transfer of energy.

It you want to remove energy by recoil, the fast particle need to hit one of about its mass. For example, if it is a baseball it needs to hit another base ball, on averge losing half its energy. If it hits a bowling ball it bounces off with little reduction in energy.

 

[cosmictotem]

The true physics is generally ignored.

In particular, propulsion (fuel), mass, acceleration, velocity and gravity are all ignored. It is like they are in a big swimming pool and can easily move around between different places, without using a noteworthy amount of fuel. It just isn't that way.

A good movie discussing the real physics (because it is real) is Apollo 13. They had a choice to turn right around and go home or fly around the moon and they flew around the moon because it was easier/safer. The decision making process and physics are discussed in the movie.

Watched Appollo 13 many times. Love the science parts. And I can get a good idea of the delicacy of the physics they are struggling with in space travel by the panic on the actor's faces.

What kind of burns me about this thread (and I know it's physics, not personal) is that a Dyson Sphere-- where a civilization basically puts their entire star in a gift box and gives it to themselves-- is considered possible by scientists but I need to account for the mass of my biosphere stations.

Where is an alien civilization going to get the mass for a Dyson Sphere?

 

[Janus58]

Watched Appollo 13 many times. Love the science parts. And I can get a good idea of the delicacy of the physics they are struggling with in space travel by the panic on the actor's faces.

What kind of burns me about this thread (and I know it's physics, not personal) is that a Dyson Sphere-- where a civilization basically puts their entire star in a gift box and gives it to themselves-- is considered possible by scientists but I need to account for the mass of my biosphere stations.

Where is an alien civilization going to get the mass for a Dyson Sphere?

By salvaging all the material in the star system (including the planets). By the time a civilization has reached this stage, it has already had to develop cheap and easy travel in its own star system (and the ability to break up planets for raw material)
But the point that others are making is that until you have cheap and easy travel through the solar system, you won't have a way to collect and deliver the materials you need to build your space habitats in the numbers you suggest. It's not that the material isn't out there in the Solar system, its just that its not easy to get to and then maneuver into position.

 

[cosmictotem]

By salvaging all the material in the star system (including the planets). By the time a civilization has reached this stage, it has already had to develop cheap and easy travel in its own star system (and the ability to break up planets for raw material)
But the point that others are making is that until you have cheap and easy travel through the solar system, you won't have a way to collect and deliver the materials you need to build your space habitats in the numbers you suggest. It's not that the material isn't out there in the Solar system, its just that its not easy to get to and then maneuver into position.

This talk of Dyson spheres makes me wonder what if an alien species DID build a ring of biospheres at one or two orbits around their star? And suppose it was fairly substantial.

Would we be able to detect a halo of biospheres around a distant star the same way we might be able to detect a Dyson sphere? Would there be a detectable split in the star's light?

 

[Janus58]

Ok so progressively more difficult if they are adjacent, not impossibly more difficult?

In other words, if the biosphere stations are in close adjacent orbits and on the same Equatorial plane, it is only slightly more difficult to jump from one nearby orbiting station to the next?

If that's the case, does that resurrect my idea of using a station supply line -- provided craft move from one nearby orbiting station to another nearby orbiting station without trying to skip orbits--- and don't try to stop at stations with vastly different orbiting velocities?

Because, essentially, that was my original point...to just move along the "line" from one nearby station to the next.

Here's the thing. Moving between stations in concentric orbits isn't as simple as pointing in its direction and firing your engines. For one, there is a minimum velocity that you have to leave one station to even get to the other station. Secondly, doing so and using the minimum fuel can take a long time. If you leave one station on such a minimum fuel trajectory, you won't reach it until both stations until over half an orbit later. If station 1 is at Earth distance from the Sun and station 2 at bit further out, it would take a bit over 6 month to travel from station 1 to station 2 along the minimum fuel trajectory.

So let's see how this would work in "leap frogging" from Earth to Mars in 8 stages ( each orbit would be ~10,000,000 km apart)
Earth to way point 1..............192.58 days
Way point 1 to way point 2...221.52 days
Way point 2 to way point 3..231 days
Way point 3 to way point 4..251.12 days
Way point 4 to way point 5..271.75 days
Way point 5 to way point 6..292.92 days
Way point 6 to way point 7..314,61 days
Way point 7 to Mars............336.82 days
Total trip time*.....................2102.32 days

Direct Earth to Mars...........261.37 days


*not including possible wait times for the next station to move into the proper relative position at each stage.

So you can get to Mars directly in ~8 1/2 months directly or spend 5 yrs 9 months leap frogging from way point to way point.

Now you could move from station to station faster by using more than the minimum fuel. But that is going to be wasteful. If you leave station 1 with enough velocity to get to station 2 faster than you would at minimum speed, you are moving at a speed that would, if uninterrupted, take you out further from the Sun than station 2. In other words, to get there faster you have to aim to overshoot the mark. When you get to station 2, you will have to match velocities with it, and in doing so you burn fuel to shed that extra velocity that would have carried you further out. It is the equivalent of stomping on the accelerator and then slamming on the brakes between stop signs (except in this case, the brakes use up fuel too.) So again, it would just make more sense to use all the extra fuel to get to Mars faster by the direct route.

 

[Russ_Watters]

What kind of burns me about this thread (and I know it's physics, not personal) is that a Dyson Sphere-- where a civilization basically puts their entire star in a gift box and gives it to themselves-- is considered possible by scientists...

I seriously doubt that.

 

[cosmictotem]

Here's the thing. Moving between stations in concentric orbits isn't as simple as pointing in its direction and firing your engines. For one, there is a minimum velocity that you have to leave one station to even get to the other station. Secondly, doing so and using the minimum fuel can take a long time. If you leave one station on such a minimum fuel trajectory, you won't reach it until both stations until over half an orbit later. If station 1 is at Earth distance from the Sun and station 2 at bit further out, it would take a bit over 6 month to travel from station 1 to station 2 along the minimum fuel trajectory.

So let's see how this would work in "leap frogging" from Earth to Mars in 8 stages ( each orbit would be ~10,000,000 km apart)
Earth to way point 1..............192.58 days
Way point 1 to way point 2...221.52 days
Way point 2 to way point 3..231 days
Way point 3 to way point 4..251.12 days
Way point 4 to way point 5..271.75 days
Way point 5 to way point 6..292.92 days
Way point 6 to way point 7..314,61 days
Way point 7 to Mars............336.82 days
Total trip time*.....................2102.32 days

Direct Earth to Mars...........261.37 days


*not including possible wait times for the next station to move into the proper relative position at each stage.

So you can get to Mars directly in ~8 1/2 months directly or spend 5 yrs 9 months leap frogging from way point to way point.

Now you could move from station to station faster by using more than the minimum fuel. But that is going to be wasteful. If you leave station 1 with enough velocity to get to station 2 faster than you would at minimum speed, you are moving at a speed that would, if uninterrupted, take you out further from the Sun than station 2. In other words, to get there faster you have to aim to overshoot the mark. When you get to station 2, you will have to match velocities with it, and in doing so you burn fuel to shed that extra velocity that would have carried you further out. It is the equivalent of stomping on the accelerator and then slamming on the brakes between stop signs (except in this case, the brakes use up fuel too.) So again, it would just make more sense to use all the extra fuel to get to Mars faster by the direct route.

That could not be explained any better. Thanks for doing all the math, as well. Very clear now. This is going to help improve my future science fiction writing. So my idea may be okay for a single orbit ring of stations but it's not a very good idea to employ as a space road or accompaniment for space travel beyond its own orbit.

 

[DaveC426913]

What kind of burns me about this thread (and I know it's physics, not personal) is that a Dyson Sphere-- where a civilization basically puts their entire star in a gift box and gives it to themselves-- is considered possible by scientists but I need to account for the mass of my biosphere stations.

Where is an alien civilization going to get the mass for a Dyson Sphere?

A Dyson sphere is possible by the laws of physics - as is your waypoint concept - but we assumed you were proposing yours within the next century or two, and with known (or at least, near future) technology.

We've been treating your concept as a serious proposal (i.e. that's a compliment), which means we do look at the nitty-gritty - the practicality. There's absolutely no such seriousness attributed to a Dyson sphere. A Dyson sphere is not going to be possible in the next millennium or two. It is definitely fantasy for us.

 

[Billy T]

... Where is an alien civilization going to get the mass for a Dyson Sphere?

It is a concept, not a fact. Very unlikely even one exists in our galaxy. If it did, and its star had many dense planets, also highly unlikely, and they had the technology to first flatten the bigger ones into disks then ribbons (mammoth "terra forming") they could slowly, millions of years, get all into a hoop spinning around the sun/ going around the sun / in one circular orbit.

After that they would need to have material much stronger than any we have even dreamed of to make self supporting arches from one point on the circular orbit mass to another half an orbit away (opposite side). Note that the part of the arch, which goes over the orbit poles of the circular orbit has no centrifugal force, balancing out the gravitational pull of the sun - why these arches must be unbelievable strong, and yet low mass as every Kg in part going over the pole add directly to the force trying to collapse it into the sun.

That is why the Dyson sphere concept is science fiction. Almost certainly does not exist anywhere in the entire universe. But hey, that will not stop you from postulating they could, not more than your postulating ionizing radiation passing thru cells need not kill human cells, some day.

For the sixth time: Where does the mass for the 40,000 spherical cosmic ray shields come from?
and now adding: if about 80% of earth's land surface is flooded by that land surface being lowered more than 1/3 of a mile to supply the mass for the first orbiting ring, why would people now living on that land politically support your plan (huge inconveniences for them and new tax burden)?

PS If you think Europe has a problem with the influx of refugees, how many orders of magnitude greater would be the problem of craming in the world's population into 20 percent of the present dry land area? (Only the tops of the mountains would still be above the ocean when about 1/3 of a mile of the upper crust of the earth has been placed into your first orbit rings 40,000 cosmic ray shields.)

 

[cosmictotem]

.... than your postulating ionizing radiation passing thru cells need not kill human cells, some day.

I am just extrapolating based on what Aubrey de Grey has said about the future prospects for cellular maintenance.

Cosmic rays cause cancer, correct? Do you not think it's feasible we could figure out a permanent cure for cancer in the near future either through cellular maintenance, genetic manipulation or a combination of both?

 

[Billy T]

I am just extrapolating based on what Aubrey de Grey has said about the future prospects for cellular maintenance.

Cosmic rays cause cancer, correct? Do you not think it's feasible we could figure out a permanent cure for cancer in the near future either through cellular maintenance, genetic manipulation or a combination of both?

Please give me a link to the papers* you have been extrapolating from to get idea humans could survive decades of exposure to cosmic rays.

Yes they can cause cancer, but most of the time, they just cause the cell to die in less than a week. To cause cancer, they need to do genetic damage. The nucleus of the cell, where the genetic material is, is tiny fraction of its cross section. Wild guess: Less than 1% of the cosmic ray (which is actual a very much smaller nuclear particle than the cell nucleus, not a "ray") will pass thru the cell nucleus.

* They probably have many papers. I want to read the one you extrapolated from.

 

[cosmictotem]

Please give me a link to the papers you have been extrapolating from to get idea humans could surivive decades of exposure to cosmic rays.

Yes they can cause cancer, but most of the time, they just cause the cell to die in less than a week.

I never said new breakthrough technologies didn't need to come online before we could attempt biosphere colonies in space, et al, my admission and agreement that we still needed to perfect functioning biospheres. I would place genetic and cellular rejuvenation techniques in that same vein.

 

[Billy T]

I never said new breakthrough technologies didn't need to come online before we could attempt biosphere colonies in space, et al, my admission and agreement that we still needed to perfect functioning biospheres. I would place genetic and cellular rejuvenation techniques in that same vein.

I asked for your reference link, and for 7th time, where do you get the mass for the cosmic ray shield and construction of the rest of the 40,000 biospheres (of the first ring)?

 

[cosmictotem]

For the sixth time: Where does the mass for the 40,000 spherical cosmic ray shields come from?
and now adding: if about 80% of earth's land surface is flooded by that land surface being lowered more than 1/3 of a mile to supply the mass for the first orbiting ring, why would people now living on that land politically support your plan (huge inconveniences for them and new tax burden)?

Again, postulating a breakthrough in cellular maintenance and genetic manipulation, why would shielding to the extent you have detailed be required? And I know, I know...there's no paper.

Now, where would the material come from?

Granting my hypothetical population of 100,000 per station was only an arbitrary number, as was the size of each station (minus your calculations for adequate shielding), there is more room for recalculating the numbers to to possibly more manageable totals.

As a prelude to the updated calculations I suspect you'll present, I will simply ask you how many, say, 30 story buildings exist on the planet and where did the material for them come from?

As far as getting that material into space without polluting the planet, again, I freely admit another possible breakthrough in clean Earth to space payload transfer may be required.

But, again, I never said breakthroughs in certain areas were not required. If I gave you the impression, I apologize