I’m sorry I haven’t been able to reply sooner.

If I have read your reply correctly, what you have said simply confirms what I wrote to blueheron.

Quite honestly, the math that you’re questioning that I can follow is, according to you, proving my statement that locomotion in a spinning container will not be like walking on Earth. In fact, as I’ve noted before, it will be dangerous to the point of non-utility.

And, respectfully, what do you ‘know’ about the dynamics of rotating bodies? Nobody has any empirical data on what it’s like to live or work in a spinning container because, obviously, you need to be in a spinning container on orbit to do the proper studies. Need I point out that no orbiting research facility exists or is planned, perhaps because the problems are quite obvious to the engineers working the issues. It’s a thought experiment where the math is elegant but non-applicable in the real world.

All the math in the world (or space) is not going to make for proper locomotion on a spinning vehicle. Given the limitations of a space station, you can be sure there won’t be any luxuries like expansive modules to allow for the arcing steps your math claims … as you be sure to land on your feet.

I’m sorry, I disagree with your example of ‘an accelerating frame of reference’. A space station spinning at a constant rate is not accelerating so there isn’t accelerative ‘gravity’. What you’ve got, as you know, is the inertial energy of your body wanting to continue in a straight line, resisted by the ‘floor’ of the station spinning at an angle. That resistance imparts the sense of ‘weight’ but it is not accelerative gravity. As long as you don’t move and stay in contact with the ‘floor’ you’ll feel this ‘weight’. Attempt normal movement and all bets are off. And that’s the deal killer for this idea. As you noted, theoretically it works… until it doesn’t. And as I noted, the engineering — if the idea had some merit — would be massive, complex and prohibitive.

And you’re right about the 1-G propulsion system being temporarily science fiction. My estimate puts it 75 to 100 years out; with a
focused program possibly sooner than that. I’d like to agree with your optimistic 50 year time frame but there are some significant engineering challeges to deal with, though none appear to be insurmountable.

As I said previously, we’ll go to Mars ‘for the hell of it’ … just to say we did it. We face the very real prospect that we may not get that first crew back. Apollo 13 proved how close we were to failure on every moon mission. Mars expeditions won’t be any better until the voyage there takes only 2 to 3 weeks with a constant propulsion drive. So, we may very well tempt the fates and make a voyage to Mars in the 2030- 2040 timeframe that NASA is positing. We might even go back if the first mission is a success. We’ll colonize, exploit for profit and live there only after we develop a constant propulsion drive.

Regards,

Frank.

I have no misunderstranding of centrifugal forces. I’ve said spinning won’t work as people expect.

The problem with spinning is that in order to benefit from angular momentum you have to stand in one place, in contact with the ‘floor’ at all times.

Attempting to walk in this environment will not be at all like walking on earth. In fact you may not be able to walk at all.

On Earth, if you jump up you have broken the bond of gravity with just the strength in your muscles. During the execution of your jump, once contact with the Earth is lost, no more energy can be imparted to your leap. So, the mass of the Earth, gravitationally weak as it is, inexorably overcomes your upward trajectory and down you come. Human locomotion (walking) is a series of graceful mini-leaps that utilizes the give-and-take of this mechanical interaction to create our mobility. We push off with enough energy in our walking gait to break free of gravity just enough to allow us sufficient elevation to reposition our feet before the Earth’s mass pulls us back down into contact with the surface. Graceful coordination makes the bipedal locomotion of humans an almost absent-minded and secondary function as we go about our lives.

That same graceful push-off that initiates and sustains our walking gait on Earth will not work on a spinning space station or space craft. Once you impart enough energy to execute a normal step you overcome the artificial 1-g imparted by the angular momentum. Up you go and you are not coming back down. You’re headed for the ceiling only to be bounced off if you can’t grab anything to hold on.

I’m afraid any attempt to move in such an environment would be next to impossible without some way of keeping you in constant contact with the ‘floor’ so the angular momentum can be imparted to your body creating this deceptively artificial gravity. Magnetic boots, anyone?

Even if this fundamental flaw didn’t exist the engineering and design of a spinning vehicle would be prohibitive. Everything that spins in space must be balanced to within fractions of a gram. A slight imbalance and an oscillation can be built that could very easily exceed the design limits of any craft. Ask NASA about out-of-balance spacecraft spinning to their destruction.

Imagine the Commander of a spinning space station with, say, a 20 person crew calling a staff meeting. Roughly 2 tons of mass would converge on one location on the station. Any movement of mass inside the space station or spacecraft upsets the balance and an oscillation starts. To counter this you’d need an active counter-balance system of masses. Now we’re into sensors, computers and interfaces with some method of moving an equalizing mass on the opposite side of the vehicle.

Then, of course, there’s the rotational torque imparted by the spin. If you want to keep any part of the vehicle stationary, say, to point your directional antennas or properly vector your engines, you’ll need an identical mass spinning in the opposite direction. We’re talking huge masses and very complex systems. Again this is all assuming that spinning works but, as I noted above, losing contact with the ‘floor’ while you walk is the ‘deal buster’.

If spinning was the solution to the weightlessness issue you could be assured NASA would be well along in the R&D of the hardware and there would be a module on ISS devoted to this R&D. I haven’t seen a dime in any appropriations for the design of a spinning spacecraft or space station. I have seen some research on a spinning bed that astronauts would take turns using to retain robust gravity-dependant physiologies (which is virtually everything about the human body). I’ve seen nothing more about it so I have to assume it wasn’t a viable technology.

Regards,

Frank

Thanks for your kind words. I’ll admit I was a bit hard on some of the writers but the cavalier regard for the difficult job of the engineer was more than I could let pass. If nothing else, I hope everyone is a little more respectful of this very difficult profession.

Regarding a spinning space station: It’ll never work, with all due respect to A.C. Clarke. We are beguiled, once again, by science fiction when we should carefully consider science fact. Rather than asking ‘What is gravity’ perhaps we should be asking ‘What is weight’? The distinction being that gravity is the force that is exerted but weight is the result. Weight is what all creatures have adapted to and weight on our bones and muscles is the reason for our morphology and why extended period without it are so damaging.

A counterintuitive aspect of gravity is that it is always accelerating us towards the center of the Earth. As you sit and read this reply you are not in motion but you are indeed being accelerated towards the center of the Earth. The resistance of the Earth’s crust counters this acceleration and you feel ‘weight’ as a result.

Since the first cyano-bacteria winked into existence the one environmental factor that has not changed is the pull of gravity. It has never stopped and is virtually unchanged since life arose. It is the only environmental factor that that can be said of. Every creature that has ever lived can trace it’s morphology and evolution to this constant acceleration towards the center of the Earth and the resistance of the crust. Take away the influence of ‘weight’, as in a 6 month freefall to Mars, and the consequences, as we are finding out, are profound and extraordinary.

Many people are transfixed with science fiction solutions to this issue. Many suggest spinning the crew quarters of a Mars vehicle. It simply won’t work. Again, our sense of ‘weight’, which is what we are adapted to is a function of acceleration. A spinning crew quarters would generate a sense of ‘weight’ as long as the spinning continued to accelerate but you can only spin it so fast before practical limits stop you.

Consider your car when you step on the gas: As long as the car is accelerating you are pressed into the back of the seat. As soon as the engine power peaks and the acceleration falls off you are no longer being pressed into the back of the seat. That is what will happen when a spinning spacecraft stops accelerating its spin. It may be doing 20, 30, 50 or 500 rpm’s but once it stops accelerating ‘weight’, the result of acceleration, ceases.

People have pointed to centrifuges here on Earth as examples of the technology that would solve the zero-g problem. They forget that all the time that the centrifuge is spinning it is in the gravity field of Earth. The test subjects are being pulled into the seat and held there by the Earth’s gravity as the centrifuge spins. As the body is being flung to the outside of the arc of the centrifuge, the angular momentum generates the g’s on the body. The Earth’s gravity field creates the illusion of the centrifuge being solely responsible for the increase in g-forces.

On a spinning spacecraft, without the mass of the Earth to create that background g force pulling the body into contact with the seat, ‘weight’ would not occur. An astronaut could stand in one place and pick his/her feet up off the floor and float in place, probably hitting the back bulkhead as the rotating structure moved beneath them. Spinning is simply not a viable solution.

If, however, an engine can be designed that would constantly accelerate the spacecraft, ideally at 32 feet per second squared, this constant acceleration would create the ‘weight’ perception to the human body without the need of an Earth-like mass. Enormous speeds would be achieved, particularly at the halfway point where the vehicle would begin a deceleration, again at 1-g thrust.

Consider the mission scenario: leaving Earth orbit the engines are powered to 1-g acceleration. All of the occupants feel normal Earth weight and function as they would if they were, say, on a submarine. At the half way point, the vehicle is turned around and for the remainder of the flight, until orbital insertion around Mars, use the engines to decelerate. The occupants still experience a normal 1-g environment during retrograde.

I have read speculative papers that say such a ship could be at Mars in 2-3 weeks. If these numbers are valid, the benefits are manifold. Gone are the tribulations of 6 months of weightlessness. The psychological effects of being cooped up in a ‘tin can’ are minimized. The long term exposure to the radiological environment of trans-Martian space is significantly reduced. And, as the engines get more powerful, the spacecraft habitat can become more protective by installing lead shielding. The efficiencies of these engines should reach a level where mass will be a minor consideration. It is, I believe, the only practical solution to a host of issues that must be dealt with for a successful mission to the Red Planet.

So, my suggestion is that we place our limited R & D space dollars into the development of an engine- be it an ion drive or a nuclear engine – that can burn for the entire transit to Mars generating 1-g of acceleration and deceleration. If we can accomplish that we will be a space faring species in the tradition of the sailing ships of old, in control of their voyage and destination, rather than a drifting raft fortuitously aimed.

Regards,

Frank

That’s capitalism:) In the end (I hope not) those will find out that money can’t be eaten…

The whole idea of the moon as a base for further space exploration is still not making much sense to me. A large rotating Space Station creating inertia as a would be gravitation, seems to me more feasible. Of course we would need to haul everything up there. But who says that the next space ship to Mars has to be build of metal? A two[+] component foam could be used to create containers and a lot else…
Our ISS is not the smartest idea. But that rotating SS has been an idea of a dreamer (A.C. Clarke)… therefore not good for practical application… ?

During the Saturn V era, correct me if I am wrong, burnt out stages floating around before burning up in our atmosphere after reentry could have been used as stages to build a circular Space Station (huge diameters), why was this not considered? Or was it.
You are of course right when you say that no-one with a solid foundation in Math and Science will go anywhere in this world, but please include imagination and creativity and have my support.

Ciao

“Look t the future, as you’ll spend the rest of your life there”
George Burns, born as Nathan Birnbaum
A US-actor and comedian
born 20.01.1896 in New York City (New York), USA
died 09.03.1996 in Beverly Hills (Kalifornien), USA

I like to say to Frank, who is probably a very decent, and warm individual. Think positiv and remember: “Scientists LOVE surprises, while Engineers don’t”
Some scientists have been called dreamers, because their were too far ahead of the crowd, like Albert Einstein, who is still ahead.
To realize the dreams, the ideas people like us, scientists and twits come up with, we need each other.
Stay cool:)

I just came across this link for the NEO mission NASA is looking at.

http://www.guardian.co.uk/science/2008/may/07/starsgalaxiesandplanets.spaceexploration

Regards,

Frank

With due respect, I have done my homework and I simply have no faith in anyone who wastes their time (we’re not talking about entertainment here) playing video games. I’m sorry, I disagree with you that these kids will be the next generation of engineers.

The next generation of engineers is tinkering with things as you read this. Those engineers-to-be are not buried in a bedroom wasting time on blithering nonsense. Our future engineers are inquisitive and rooted in the real world. They don’t fry their brains with this nonsense.

Your comment about the state of our labor pool of existing physicists and engineers is dead on. The sad state of our high-tech work force is a crime, in my opinion. We need to look seriously at Wall Street and its enablers in Congress to address the evisceration of the R & D and manufacturing base of this amazing country. We went to the Moon. We can do anything. Get the hell out of our way!

The profiteers of Wall Street have stripped and debauched this country in their headlong pursuit of money, the rest of us be damned. Witness the diminished state of America today if you harbor any doubts about the corrupting influence of ‘capitalism’.

With the lifetime earnings of our physicists and engineers it would seem that the taxes they pay and the earning power they bring to the economy (never mind the production they are responsible for designing) would justify extensive subsidies for their degrees. As long as you’re not diluting the pool of engineering candidates with H1-B, I don’t believe you can have too many engineers. It’s a demanding discipline and not everyone is up to the academics. It’s self-limiting, so to speak.

H1-B is the Wall Street ploy to get the cheapest labor to do the intellectual heavy lifting. They then charge the same prices for the finished product and stick that ‘bonus’ profit in their pocket. From their point of view, what’s not to like? From our point of view, how much is enough? When they have everything, then what?

We need to pull back the military from every base on Earth; charge them with the defense of America out to 200 miles and then redirect those obscene trillions (I can’t fathom billions of dollars and now we’re talking about trillions?… what is wrong here?) to our manned and unmanned interplanetary explorations. We need to aggressively address the issues of renewable, sustainable energy with NO carbon footprint (read: Fusion). We need the infrastructure of the nation rebuilt yesterday. And, (let me pull my bleeding liberal heart out here) there are good Americans who are in desperate need … we will be measured as a people by how we treat the less fortunate of this extraordinary nation.

Thomas Jefferson once said, “I tremble for my country when I reflect that God is just; that his justice cannot sleep forever.” We need to take that quote to heart. I don’t believe we are doomed but I believe we may have to look into the maw of Hell before we realize what we, in our inattentiveness, have allowed to be done to this magnificent nation.

**********
As to the lava tubes, since my previous posts I’ve been doing some research. This group funded by NASA has been doing what you’ve suggested by utilizing the data from Clementine and the Lunar Orbiter. According to their research, they’ve identified quite a few lava tubes.

http://ddf.gsfc.nasa.gov/report/2005/pdfs/SS_Wolff.pdf

As you noted, NASA wants to go to the best places for research and development, and lava tubes are where they are. Too, lava tubes are, more than likely, going to present a lot of variability from size to depth to interior configuration. The drilling and digging to access the interiors will be a serious issue. Lava tubes may not lend themselves very well to a standardized habitat design making each one a custom job with all the problems that that would entail. I’m just not sold on the lava tube idea. I believe habitats buried under regolith are the way to go.

All things considered, I still believe we are limited by what an Ares V can launch. As problematic as a quonset hut design covered with regolith may be, it seems to me to be the best solution at the least cost. The major issue that I see with a buried habitat is getting the regolith on top of the habitats. It would seem some variation of a front-end loader will be necessary to put the regolith on the structures. Once that is done, such a vehicle could do double duty for all of the other heavy-lift projects that will be inevitable over the lifetime of the outpost.

Here is a design NASA/JPL is currently working on for a vehicle they call ATHLETE.

http://ai.stanford.edu/~latombe/papers/athlete-06/paper.pdf

While this is hardly the front-end loader I envision, I can see multiple applications for this design that could involve a bucket/dragline of some sort to place the regolith on the habitats.

Ultimately, everything NASA shoots to the moon will need to be multi-purpose and extensively adaptable. All engineering efforts for the construction and development of the habitat should target minimal construction time, minimal-to-no crew involvement due to the danger of any construction job site and the simplest and most robust design to minimize maintenance. There are only going to be a limited number of flights to the moon. I hate to keep reminding everyone of this but moon shots are very expensive. That all by itself will greatly limit what we can do on the Moon.

My understanding of NASA’s goals on the Moon is that they plan to target Shackleton initially, quite possibly making it the ‘home’ base. From there, as the technology of building and living on the Moon gets refined, there will be a number of research outposts set up in the non-polar regions. The obvious challenge at these outposts is the 14 days of darkness causing solar power processes to cease.

The research paper of the group noted above cites their belief that a Stirling engine coupled to a buried heat sink can run through the 2 week lunar night by storing heat in the regolith. NASA is calling for 50 kW of power for the operational needs (that doesn’t seem like much) and this group seems to have a possible solution using the Stirlings. To do research on a lunar-wide basis some method of supplying power through the 2 week lunar night will have to be at the top of the list of ‘things to do’. I’m intrigued with their proposal. I’m going to follow up on it.

Here is another idea that NASA researchers are proposing that has a novel way to reject waste heat for a concentrated sunlight heat source. No mention is made of 2 weeks of lunar darkness so I can only assume this is a concept for the permanent sunlight on Shackleton’s rim. They’ve done some serious calculations without getting into the specifics of the system.

http://www.auburn.edu/research/vpr/sri/papers/A_LSR_for_a_Lunar_Stirling_Power_System.pdf

Of course, dust will be a major issue for any sunlight concentrating and radiator technology. This paper

(http://www.lpi.usra.edu/lunar/documents/NTRS/collection2/NASA_CR_4404.pdf)

goes into moderate detail about dust transport and the consequences for power system components. Dust, it seems, is going to be THE issue in the design phase of the lunar base as well as the actual application of the various designs.

****
I’m not a big fan of the concept of mining asteroids. I think the costs and technology necessary will be prohibitive. The asteroids with water, that might provide fuel for some future mission, only exists in the edge of the asteroid belt that’s closest to Jupiter. Any closer and the Sun heats it until it volatilizes and you’ve got a beautiful comet for a few loops around the Sun.

Hard, rocky asteroids, assuming they have materials to mine, will have huge problems that must be solved before we can exploit them. Not the least of which: How do you get the raw material tonnage down to the Earth where it must go to have its greatest value? You can’t just drop it into the atmosphere; you’re going to need some kind of re-entry vehicle and parachute. How many tons are you limited to with that kind of re-entry technology?

And I think it would be impossible to launch entire industries to set up zero-g manufacturing to build widgets for Earth-bound consumers. Again, how do you get enough tonnage of finished products to Earth to keep the price low enough to sell? You’ve got built-in costs due to the launching and landing of spacecraft that would make an asteroid made of pure gold too expensive to mine. We have a tough enough time mining here on Earth without taking it to the asteroids.

But we should go and have a look. There is a proposal making the rounds at NASA to have a deep space ‘shakedown cruise’ of the CEV to a NEO asteroid. When I read that, I felt you couldn’t ask for a better mission to test the CEV prior to a Mars mission. The mission is estimated to be around 30 days round trip and the rigors of a Mars mission of 2 years are avoided while technique and technology are refined in a challenging deep space mission.

Since NEO asteroids hold the potential for the end of humanity, what better mission could be conceived to develop our rendezvous techniques to ‘nudge’ a doomsday asteroid into a benign orbit. I hope to have some more information on this soon.

Regards,

Frank