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

Though it is hard to disagree with some of your points, it pays to do your homework when you criticize others. Those kids who are playing the games are going to be the ones doing whatever engineering is done in the next generation. In my generation(I'm 60), there were bunches of PhD physicists and engineers pumping gas, so many people chose other jobs. Once the Moon program wound down, many of those who were so committed to such work were forced to seek other employment. If we want competent engineers, we need to offer them consistent opportunity for employment after we educate them. Right now, many degreed and experienced U.S. engineers and physicists cannot find jobs in the face of H1-B immigrants and the shipping of the majority of manufacturing and even development jobs overseas. If we want to rebuild our base, we have to offer them a way to make a living. In addition, those who do the usual 5 year programs for even such bachelor's programs, end up owing tons of money from student loans, which they have a hard time repaying. Now, if we were to offer them government service to repay those loans, more might be willing to take the risk.

But let us get back to the subject. Many lava tubes are found in the horizontal/slightly slanted mode over fairly long runs, so that problem is not likely to be quite the issue that you have portrayed. Now, whether such could be found at the preferred location is another issue entirely. It is really not that difficult to discern some of these things. A fairly powerful orbital radar can map such subsurface features fairly easily, and robots can prospect to confirm results. These are not missions that require a huge commitment, but even these have not been done, so the process seems more dog and pony show than realistic mission. I don't believe that the current administration has or ever had any realistic plans to actually do this mission, only to appear interested in "space" to deflect those who actually are interested and see the need.

As far as power sources, the biggest problem is not heat creation, but heat rejection in a vacuum. Any closed system has to have a fairly efficient means to reject heat from the system, to close the cycle, and that is going to be a problem, no matter the method of power production. Solar voltaic has the least problem, but all the others have major issues. Now, with a rim that is permanently exposed to daylight, and a base in permanent shadow, we have the perfect situation for heat gain and heat rejection. We need not necessarily have our facility on the rim or in the base and power on the rim. Very lightweight mirrors on the rim can reflect light down to a power facility far enough down to be largely in the dark or even all the way to the bottom. A stirling engine run by such a unit could produce quite a lot of power in such a situation, certainly enough for intermediate power needs. I do believe that a ton of those nuclear SRG's and some initial panels would produce more than enough power for initial purposes, while the first solar engine units were set up. It has already been shown that sufficiently accurate solar reflectors can be inflated with hardening foam that is quite light and quite strong, especially in a low gravity, vacuum environment with no "weather" loads. Both trough-style and parabolic reflectors can be created in this manner, and using light and mirrors obviates the need for long, heavy cables that would require maintenance. As for movement in and out of the crater, a very lightweight boom and cable can move astronauts and small to medium equipment up and down without too much strain. For safety, they can ride one of the old type of thruster units should a cable break, though I consider that somewhat overkill. Construction on the Moon will certainly be difficult, so any natural features such as lava tubes or other caves that we can take advantage of should be used. It is a lot easier to seal the inside of such than it is to build and cover any manmade structure. We certainly have materials that should be quite adequate for the task. Also, if we have firm rock, we can blast a hole much easier than we can do any other thing. We also can drill explosively to place the larger explosives.

As for dust problems, if we found out a way to deal with taconite ore dust after WWII, I suspect that we will manage lunar dust. Certainly, your suggestions or some similar should be pursued, as they seem to have some merit.

Now, if it were me, I would boost a nuclear engine out to a small asteroid known to contain water, and use that as fuel to go get another one with the rest of the materials needed to build a real orbital habitat around the Earth and then the Moon, making so much of this need for Earth or Moon resources so much less critical.

Excavating into those would produce a safer orbital habitat than any we can boost, while providing raw materials for almost anything that one can imagine, the most important being space based solar power. Engineering is certainly required for each and every one of those things to be accomplished, but someone, engineer or otherwise, must have the dream, first.

NASA seems to have its heart set on Shackleton Crater at the south pole. The crater's rim is in permanent sunlight. A rotating parabolic mirror would keep the sunlight focused on the furnace virtually forever. I think that would solve the night issue.

The only problem I see with the base in the crater in the permanent shadows and the power plant up on the rim is cabling the power down the slope. I'm a little uneasy laying a megawatt cable on the regolith.

High voltage is very tricky. There is a powerful magnetic field that surrounds a high-tension wire. One weak point in the insulation/shielding and, just like lightning, a passing magnetic field no stronger than golf club during a swing or an astronaut in a space suit and a huge arc will jump to ground through the disturbing magnetic field. I've seen birds get killed flying close to a high voltage wire where they disturbed the magnetic field of the flowing electricity and draw a lightning-like arc to their bodies. Smoke and feathers were all that was left.

This isn't a fatal flaw to the idea but it must be carefully considered if an exposed cable is used.

My guess is that towers to suspend the cables are out of the question from a purely construction logistics standpoint.

Regards,

Frank

And yes, I do agree solar thermal would be an excellent system for use on the Moon. It does have one major drawback compared to nuclear: the 14 day lunar night. Personally, I think the best solution to it is a sort of hybrid system, with solar thermal providing main power during the day (hopefully most power-intensive activities on the base could be done then), and some minimal suplimentary or keep-alive power during the night span. This is the main use I see for nuclear reactors, although there are many non-nuclear methods for storing energy available for slightly higher mass.

If I recall correctly, the Artemis society's Reference mission would have provided keep-alive power for the early base's electrical systems (etc.) using residual hydrogen and oxygen gas from the decent stage's propellant tanks, for use in fuel cells. From the numbers I saw, they could look forward to perhaps 300-400W of power during the night span. How about replacing that system (which would involve designing the propellant tanks to double as pressure vessels) with a sterling-cycle radioisotope generator? Those are relatively compact systems, so a base crew could probably just pile up some dirt around a box with the generator inside (allowing some method for heat to be radiated away, of course) to provide rad shielding While this isn't exactly a "light up Las Vegas" type of system, it should work for an early lunar base.

Now there are issues with that plan if a non-governmental agency (or rich visionary individual…) wanted to use plutonium-237… But from a technical standpoint it seems plausible to me.

Sincerely
-Michael P.

I just came across this on Salon. It's terrestrial but it makes an unspoken case for the moon.

http://www.salon.com/news/feature/2008/04/14/solar_electric_thermal/index.html

Regards,

Frank

For any truly significant electrical output, you're stuck with a steam cycle (or some variant) just like the solar furnace for power generation. Nuclear reactors achieve their temperatures by fissioning the nuclear pile. This requires a cooling loop to keep the reactor from overheating and melting the core; the classic China syndrome we hear so much about. This cooling loop is run through steam generators that transfer the heat to the steam cycle water. I just don't see, even absent any shielding, a way to get a reactor that would be small enough for launch and still generate enough power for a respectable moon base. I would think that if NASA goes for it (a lunar base) they'd want to have more than enough electrical capacity for any future expansion. I'd sure rather have too much than not enough. But, as always, there's that trade-off — the bigger the reactor the more power you've got but the more weight you have to throw up at the moon. It's a maddening problem.

And still, the shielding is ultimately going to be needed. While refueling can be virtually eliminated with a nuclear sub type reactor using highly enriched U-235, basically bomb grade U-235 (25-30 years per core) maintenance would be impossible without shielding. I can't imagine going to all of the expense and labor of putting a reactor on the moon only to abandon it in place when a minor maintenance issue renders it unusable because it can't be approached. Fissioning nuclear reactors, I'm afraid, are just too problematic.

And, on a side note, what would you have to deal with just to launch the reactor? I still remember the stink that was raised when Cassini was launched because it had an RTG for power. Environmentalists even raised hell on the Earth fly-by that Cassini did to gain speed for its outbound flight. I can't imagine the uproar if an actual nuclear reactor pile was launched.

I found this on Wikipedia. It's info about the only full-fledged US nuclear reactor to fly in space. It used thermocouples to generate electricity and its output was only 500 watts

http://en.wikipedia.org/wiki/SNAP-10A

NASA seems to be showing some interest in Stirling radioisotope generators which seem to generate 4 times as much power as an RTG. You're still looking at only 100-120 watts of power, not a lot for a moon base.

http://en.wikipedia.org/wiki/Stirling_Radioisotope_Generator

I had a discussion today at the launch of the ICO-G1 Communication satellite (launch pics here: nasatech.net) and the consensus is that any nuclear reactor is too much nuclear reactor. These guys weren't the planners and engineers but they are very much up on the current state of the art, such as it is.

I'm going to start asking my contacts at KSC who the lead engineer for the power generation design group is and get his/her thoughts. I'm getting very curious about this. Stay tuned.

Regards,

Frank

I actually thought the ascent stage RCS used the same tanks with/as the main engine. Thanks for that link.

On the subject of lunar power: I agree that a solar furnace may be one of the best options for powering a lunar base. However for nuclear power, I usually assumed that all that would leave earth would be the reactor core and some sort of heat engine. Just land the thing a few kilometers away from the base, perhaps on the other side of a hill or mountain and use that mass (and distance) as rad shielding.

I've often heard estimates about small reactors weighing less than a tonne, of course with outputs usually less than 100kw, but still easily under the capacity of the Atlas V and Delta IV vehicles. Not quite on the same scale as what you work with. What do you think the output of a reactor could be, if the shielding is the moon itself, of a reactor weighing somewhere around 3 tonnes or so? No need to rely on NASA finishing project constellation or anything, I only really care about what could be done today or with programs unlikely to be canceled.

If you ask me about the cost of Aries I and V, tho, I'd say closer to $800 million and $2B, respectively.

Perhaps I've heard too many horror stories about Aries I, Orion, and Constellation in general, tho.

The showstopper for nuclear is the radiation component. It's going to need a considerable shield to contain the radiation. Water, concrete and lead are excellent shields but all are extremely heavy and would be nearly impossible to transport to the moon in any kind of a cost effective way.

Please keep in mind that for the forseeable future our access to the moon is going to be limited to what an Ares V can lift to the moon, which is about 55,000 to 60,000 kg. There are no figures I was able to find for the lunar landing vehicle but whatever the mass of the landing vehicle is you can immediately subtract that from your deliverable payload. It wouldn't surprise me if the landing vehicle for anything you want to land on the moon is half of the total lunar payload, or about 25,000 to 30,000 kg.

You're also limited by the shroud length and diameter. The numbers may change slightly but at present the baseline Ares V 8.4 meter shroud has a 7.5 meter dynamic inner envelope diameter and an 18 meter envelope height. Alternative shrouds being considered include one with a 12 meter outer diameter, 10.3 meter payload diameter and 21 meter total height.
(ref: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070038373_2007037046.pdf). So, whatever gets launched can't exceed these maximum values in height, width and weight.

Another often overlooked factor is the cost. The vehicles are roughly estimated to cost from $350M to $500M per vehicle. Expect the vehicle cost to rise and I'm sure that number is empty, not 'wet' on the pad ready for launch. With this in mind, there is going to be a lot of incentive for the designers, planners and engineers to get as much to the moon in as few trips as possible. This is going to place a premium on low mass, compact design and minimal-to-no construction when the payload gets there. Nuclear reactors, even the small ones, are going to be prohibitively heavy.

And there is the catastophic failure factor. An explosion on the moon of a reactor or any of its components would not only knock out the major source of electrical power and destroy a critical asset but would, more than likely, scatter some very nasty radiological debris making the area inaccessible for centuries! It would be next to impossible to clean up. It would be an "Abandon in place" resolution. I honestly don't see nuclear as an option.

Solar cells will more than likely provide initial power but as demands for watts goes up– and it will as the construction project gets serious– the demand for power will exceed the solar cell output very quickly. Would a solar furnace provide the answer?

Questions abound on a solar furnace: can a system be designed that's small enough, light enough, with high enough efficiencies to justify the investment of an Ares V or two? Is a steam cycle even possible in a low gravity environment without air? The steam loop would have to be in a pressurized enclosure to preserve the water. And even with the best of design, water would still be lost and need to be periodically "topped off". If the indications of water ice in Shackleton Crater pan out this may not be a problem but if the water ice is not there or impossible to get to, you're transporting water from Earth, a very expensive proposition.

Failure modes of a solar furnace might make this a showstopper as well. Steam is a nasty, temperamental critter. If there was a catastrophic failure, as in a steam explosion, there wouldn't be any radioactive residuals but there would be one heck of a mess and it's quite possible you'll be left without enough electricity to continue the mission. It's safe to say the lunar mission would, at the least, be highly compromised and quite possibley be over for a while as the colonists high-tail it home.

And all this surmise proceeds from the assumption that a small solar furnace can generate the power output required to make it a viable lunar colony technology. Truth is, I don't know enough about the intricasies of the solar furnace to make anything but a guess about its efficacy. I would very much like to be a fly on the wall as the arguments go back and forth in the planning meetings for the lunar colony.

Concerning the CG, the perpendicular fuel tanks you mention are for the RCS system and, yes, they were located equidistant from each other around the center of the crew area. The center of mass of the LM, however, was not through the center axis of the engine (the center of thrust). Look at the schematic of the LM ascent here:

http://www.clavius.org/techlmstab.html

for a very good description of the stability issues of the ascent stage of the LM. Note his reference to the off-axis thrust and the consequent rotations in the paragraph above Fig. 6

The oxidizer/fuel ratios also contributed to the rotations as the tanks emptied. Here is a space souvenir I wouldn't mind having and, yes, it would be in my livingroom too. The oxidizer/fuel ratio is noted as 1.60
http://www.apolloartifacts.com/2007/09/tr-201-bipropel.html

I recall an interview on the History Channel where Aldrin commented on the LM rocking from side to side during the ascent. If memory serves, he said, even though it was expected, it was a bit unnerving until the fuel supply became low enough that the oscillations were small to non-existent. I couldn't find a copy of the interview.

Here is a video of the launch of Challenger during the Apollo 17 mission. Watch closely and you can see it tip to the left and then right itself as the RCS makes its correction.
http://history.nasa.gov/alsj/a17/a17v_1880127.mpg

Concerning the Star Trek tech: Automatic sliding doors have been around since the '50's in malls and shopping centers. (ref: http://inventors.about.com/library/inventors/blshopping.htm)

And cellphones I don't think are a good comparison to the communicators. A closer comparison might be the satellite phones that people use in the middle of nowhere to call for a rescue or to call their friends to say "Guess where I am right now.". They're bigger than the Star Trek communicators but I'll give you that one even though it can't call an orbiting starship.

Regards,

Frank

Frank:

You commented earlier about how massive a nuclear reactor would be, and seemed to refer to land-based reactor designs. Are you familiar with the design of reactors used in nuclear submarines? Most space reactor proposals are scaled down versions of those, not reactors used to supply power to the main grid of many cities.

About CG motion on the LM ascent vehicle, I'm not sure I can agree with what you said, unless you mean vertically toward the engine. The two propellants (N2O4 and Aerozene-50) have noticeably different densities, and in any hypergolic engine are not used in the same proportion. From what I have heard, the earliest concepts had two N204 (oxidizer) tanks opposite each other, and two fuel tanks opposite each other perpendicular to the first two. The two tank design worked because the two tanks did not need to be equidistant from the engine as would be necessary in an aerodynamic vehicle. While the lighter fuel tank was loosing mass more slowly than the heavier oxidizer tank, it was also the further away of the two, so the overall affect (side to side) on the CG was to keep it still. Vertically, fuel was always forced to the bottom of the tanks by the acceleration of the vehicle, so as fuel was used, the CG would move down… but have very little affect on the vehicle's CG. This is also a very good thing, as the RCS thrusters had only about 1/40 th the thrust of the main engine, and that engine was non-vectorable, so any major change side to side in the CG would lead to the vehicle loosing control on the way up. Those RCS thrusters may have been strong compared to what is used on satellites, but not quite that strong.

On a side note, about the earlier mention of Star Trek. We do have at least two technologies that were inspired by that show: sliding doors (straight off the set, I've heard the production crew received calls from engineers on how they did it, the response was stage crews holding ropes behind the set) and cellphones (remember those "communicators" from the original series… ?)

Sincerely
-Michael

You're making reference to the solar furnace. Designs vary but the one in Nevada uses an enormous field of concave mirrors focused on a sodium filled 'furnace' that does indeed heat it to a liquid state. The sodium is in a closed loop and transfers its heat to water for steam.

My guess is that this would be the most practical power plant for a lunar station. It would take up a lot of space but not as much as a solar cell array. The technology is established and radiation-free but still quite huge and lunky to transport. It would, however, generate mega watts of power. Its safety and useablity in a lunar environment is an unknown.

Keep in mind that the first moon base, more than likely, will be inside Shackleton Crater at the lunar south pole. It has permanent shadows that shield parts of the floor from any solar radiation and light. Being at the south pole, however, provides about the only location that will get constant sunlight above the crater floor for the entire 28 day lunar cycle. At the equater all the way down almost to the south or north pole there are 14 days of darkness. This is an enormous challenge because you just can't put your laboratory or living facilities into hibernation for 14 days.

If current plans work out, the habitat will be in the permanent shadow on the floor of Shackleton. This protects the outpost from the intense solar radiation. It doesn't do a thing for the rain of meteorites so using lunar regolith to cover the habitats will be the most practical solution.

Now we're back to electric vehicles, such as a lunar front end loader, to scoop up regolith and deposit it on the top of the habitats. Ignoring the huge weight that must be launched and landed on the lunar surface, you'll need a lot of power to run such vehicles. Your solar furnace, or a variation would be, for all it's weight and complexity and assuming it works in the lunar environment, the most practical, simplest and efficient power source.

Having said that, it will have to be located on the permanently illuminated rim of Shackleton with a power feed line going over the edge, down the slope to the outpost at the bottom.

If the images I've seen of Shackleton are accurate, that's a long way down. For research access to the rim and for maintenance of the furnace there will have to be a lift of some sort because no one will be able to climb the slope. So now we're into the cable car noted in the article. This could double as a power cable support. Now we're into the problem of building the towers on a slope that you can't walk up or down on. It's a frustrating engineering problem.

Another issue in the article is getting around on the surface. Some posters have mentioned using rockets to liftoff and transit horizontally setting down wherever you need to go. That's a very dangerous and costly method that should be reserved only for return flights home. Any combustion of fuels for such a purpose expends a very precious resource that you won't have a lot of. Any time you fire up an engine you risk explosion. It has to work perfectly every time… one burp and you crash on the surface.

In my years working at a nuclear plant I had the priviledge of working with one of the former engineers for Grumman who's team helped develop the ascent engine for the LM with the Bell Aerospace subcontractor. He related the enormous difficulties of designing a lightweight but powerful engine that had to work the first time in a vacuum. The rocket scientist's axiom of "Simplicate and add lightness" was in full force during the development of the engine. The final engine design was exquisite but it was designed for a one-time use.

It was a hypergolic engine design where all you had to do was open valves and let the liquids come in contact with each other in the combustion chamber and you had thrust. As simple as that sounds, the oxidizer had to enter the combustion chamber a split second before the fuel. If the fuel got there first there was the possibility of the engine exploding when the oxidizer entered.

The engines used a fuel of Aerozine 50 ( half-and-half mixture of hydrazine and unsymmetrical dimethyl hydrazine) and nitrogen tetroxide as the oxidizer. Both very nasty if you come in contact with it and explosively deadly if these two liquids made contact outside of the combustion chamber. You couldn't afford leaks in your tanks or degraded seals in this caustic environment in your valves or out-of-sequence implementation. The consequences would be catastrophic. A crash on the surface, in all likelyhood, would result in a large explosion and some very dead human beings.

Always keep in mind that any rocket firing anywhere, especially on the moon, even to just to hop a mile or so "over there" is a major technical feat and is never taken lightly. The chance of failure for such casual use is too high to risk it as a method of lunar transportation except for the return ride home.

Also, putting aside the explosive nature of the engines, because of density differences in the fuel and oxidizer, the tanks empty at different rates affecting the center of gravity. The LM's slowly rocked side-to-side on ascent as the RCS fired to bring the vehicle back to vertical. This would preclude using it to lift any kind of usable mass for any kind of lift as in a crane replacement operation.

So, what is the solution to transport on the surface? I really don't know. Lunar rovers, for all their drawbacks seem to be the best solution right now.

I don't believe it's impossible to colonize the moon but it ain't gonna be easy. As the article above noted, dust is a difficult and perplexing problem. You can't bring it into the habitat or you'll be breathing it and, like it or not, it will manage to get into every piece of hardware that is exposed to it.

I think the idea of building a 'roadway' is technically prohibitive. Assuming you could do it, you'd only have a road between point A and point B. It's a safe bet there's going to be something interesting to go look at over on point C, D, E, F etc. It's simply impractical to build a road everywhere you want to walk or drive. I think the solution for the exposed vehicles is better design on seals and rigorous maintenance.

For the space-suited lunarnaut I think a mylar-type coverall going from the top of the boot sole to the helmet and down the arms to the gloves and secured to seal off the interior of the coverall would provide several things for the lunarnaut. The smooth metalized surface would provide the least surface area for dust to adhere. It would provide another layer of solar radiation protection because of its reflective surface. It would also provide a possible dust removal method that's simple and effective.

Upon entering the airlock and as the air pressure returns, the dust-covered lunarnaut would connect low-voltage electrodes to the mylar-like coveralls and induce a current that alternates between negative and positive. At the same time, the lunarnaut would stand in a high-tech 'boot polisher' that would scrub the soles and suck the dust down to a hepafilter to be trapped and contained. At the same time as the air pressure in the airlock builds an air shower, not unlike what cleanroom technicians use prior to entering the cleanroon, would blast the exterior of the mylar-like coveralls. As the voltage goes back and forth the charge on the dust would cause it to be repelled as the polarity flips back and forth. The airshower would blow the dust away from the lunarnauts and be sucked toward a hepafilter to be trapped. A minute or so of this and the airlock area and the lunarnauts should be dust-free and ready to get out of their moonsuits.

I don't know if it would work but it's simple and the technology already exists.

Regards,

Frank

That’s quite a thorough response. Although I don’t agree with everything you wrote, you do make some valid points.
I won’t dwell further into this because I don’t see that much would come from it. There are also many more articles that I would like to read and possibly respond to with my own suggestions/opinions.
See you out there………………
Cheers//

Your first point couldn't be more wrong. Humanity did things because there was a need, not because some ancient forebear sat down one day and dreamed of something. No one dreamed up fire. An ancient hominid was near freezing to death or perhaps having his or her clan members dragged off by a predator in the middle of the night that focused his or her mind on a solution. Constant observation and the ability to draw relationships between disparate occurences led to the control of fire and changed our species as it conferred a survival advantage no other creature could comprehend, much less utilize.

Humanity from its outset was beset by the scourge of survival. Not a single mastadon walked into their camp and obligingly dropped dead so they could eat for the winter. All it took was a belly-wrenching hunger and a few near-death experiences and the mind of our ancestors was focused on the need to survive. From that need, not dreams, came the spears to bring down prey and, over time and continual observation, the spear throwers, that multiplied the distance and striking power of the spear, became another of the contrivances of our survival.

Natural selection weeded out the dimwitted as those with organized minds were able to develop successful tactics in the hunt. If your tribe had smart people who were more clever in the hunt than the tribe over the hill then you survived and the other guys didn't. Life back then, as it has been observed, was nasty, brutish and short with not a dream among them.

But here we are, so they did something right. And that "right" thing was focusing all of their early brain power on the pressing and incontrovertible needs of survival. This is what spurred the innovation and the engineering, primitive as it was, and added, bit by bit, to the survival base of our species. This will to survive that is imbued in our DNA is the driving force of our innovative nature giving rise to such ancestors as the tool maker, homo habilus, the handy man. Not a dream coursed through his brain that woke him up at night with an idea he had no use for and wouldn't contribute to his survival.

Dreams, my friend, confer nothing to the grand scheme of things. Cold, unforgiving experience is our guide. We ignore it at our very great peril. As I noted in a previous post, we, as a species, can't know what we don't experience. That said, even the "dreams" you hold in such high acclaim are rooted in reality we've experienced. Distort that reality with nonsense and we get the vapid traipse of the undisciplined mind as evidenced here in these posts.

When our species went from a hunter-gatherer society to an agricultural one we were transformed again as a species. Never again would we be able to go back to our hunter-gatherer ways because agriculture conferred a survival advantage so great that it would be like giving up our ocean-going ships so we could return to swimming to cross the ocean. Agriculture was not dreamed up. It was the constant observation of the environment, the seasons and our unique ability to see cause and effect that brought crops to harvest and ensured our survival as a species.

And we don't educate engineers to make our dreams come true. The marketplace dictates what an engineer will design and build, not your dreams. Some entrepreneur has an idea, perhaps based on a suggestion by someone, which he or she thinks will make them very rich, conferring a decided survival advantage to the entrepreneur and his or her children. At that point they hire an engineer to build their idea. Is that a dream? Nope. A need was identified and exploited for profit. At its root it's the need to survive.

No matter what you think of space travel and the reasons we, as a species choose to take the enormous risk and expense involved, it's ultimately about finding something that makes us fabulously rich or confers in some other way a profound advantage in survival. How many times has it been written that we must go into space to colonize another world for the eventual time when we finally wear this tired orb out and we can't live here anymore. A bit farfetched at this point in time, but not wrong in its overall conclusion.

On your second point: Yes, it is wrong to express silly "dreams" when the original article tries to convey just how difficult colonizing the moon will be from the infrastructure and transportation angle. Read the article again. Florian Ruess, a contributor, was dismissive on this particular point "…And please forget about the much-cited lunar concrete! There are so many showstoppers for this imaginary material that I don't even want to start mentioning them." This man, without saying it, doesn't want to be bothered with "dreams". And "lunar concrete" is a far cry from the silly sci-fi Star Trek "dreams" put forth in the subsequent comments. I'm not the only one who thinks that these challenges require rational, logical minds to innovate for the needs of a real, practical moon base. Dreamers need not apply.

You're right that it shouldn't be 'just for “Bachelor of Science degree” and above'. I'm a firm believer that sometimes the best solutions to some intractable problems come from those that aren't inculcated with the "company philosophy". But even an outsiders contribution, someone thinking outside the box, so to speak, still needs to be in the same room that the box is located in!

And concerning your "Oh, by the way…", there isn't a single thing on Star Trek that can be found in our technology today. No warp drives. No transporters. No replicators. No tricorders. No phasers. No photon torpedoes. This fantasy entertainment, and that's all that it is, has done nothing for the advancement of society except entertain the rational among us and fill the foolish heads of the rest with nonsense and contempt for real science. It is not, by any stretch of the imagination, a template for our future or a standard by which to organize society. It is entertainment and nothing more.

Point 3: Video games and sci-fi as entertainment is fine. It's the descent into an all-consuming abuse that's the issue. I prefer chess as entertainment. But, be assured, that my wife would be making appointments with a therapist if I locked myself in the bedroom for hours on end playing chess on line. It's the waste of time that I take issue with. And all indications are that there are way too many people — young and old, sad to say — that fry their brains on this crap and then can't navigate a logical thought process much less achieve anything of note in school or life. Then they show up in forums such as this with their addlepated notions of science and engineering taking great umbrage at any criticism of their silliness.

Point 4: Lighten up? Sorry, their prating foolishness needs to be called to task. Again, I point to the serious nature of the original article above and the need for rational thought and not the fatuous yammering put forth here.

Which brings me to my original point that the puerile posts on this thread are insulting to the real engineers who labor to bring a real and functioning moon base to the benefit of all humanity. As I've said before, without a strong foundation in math and science, nobody goes anywhere in this world.

Are these posters stupid? No, I've seen no indication that they lack the ability to understand the difficult lessons of science or math. It's obvoius, though, that no one has called them on their nonsense or held their feet to the fire to understand the real world as it really is. That is the underpinning of my trenchant criticism.

Oh, and a final note, I don't need to find myself a girl or get rid of the one I have. My beautiful wife loves me just as I am and for all the "geezer" that I am.

Respectfully,

Frank

I agree that to spend your life fantasizing without ever making an effort to apply your ideas in some useful way is an exercise in futility. I maintain that science fiction is not without some redemptive merits but I also agree that to waste hours fixating on Video Games and Television does absolutely nothing for society. Take that inspiration and put it to use.

In any case I enjoyed the discussion, I apologize to the audience, whom I can only assume has read my tirades with a few long suffering shakes of the head and as for the Challenge Extended, I suppose at some point I may indeed need to attend College, for now I will continue earning a living doing what I enjoy.