InigoMontoya

OK, so you want to burn hydrogen in an O2 environment. Where are you getting the hydrogen from? And why hydrogen rather than any number of other similar fuel sources?

What do you even mean by "would hydrogen power be good enough?" You're already throwing known physics right out the window with the anti-gravity thing. If you want to declare trained frogs rubbing sticks together as your energy source, why not? It's no less realistic. Now, it might not have the "cool factor" of "hydrogen power" (whatever that means) but it's no further beyond reality than your basic principal. As such, if you want it to be hydrogen powered... Make it so!

I've no idea regarding your first question, but at least in my experience the answer to your second question is "No."

Well, the good news on that front is that I have one tank that is not used to experiment with. If I crush the tank, no loss. If it survives... Hey, 8 more just like it that I actually use.

Again, we've had desicant-based dryers in the past. The maintenance requirements and fragility of them make them show stoppers for us. While the small amounts of water that get past our dryers are annoying, they aren't show stoppers. Dryers that are down for maintenance, on the other hand, ARE show stoppers. Appreciate the feedback.

Well, with unlimited money and resources.... Sure, you could put the world's population in orbit in just a few years. Alas, "unlimited money and resources" is every bit as realistic as colonizing the Sun.

Money is not a factor... That right there could have unintended consequences. How much havoc are you willing to cause the rest of the world? By that I mean things like.... Global shortages of food and goods because you're using enormous amounts of petroleum to launch stuff (thereby not leaving enough for people to transport food around). How many lives are you willing to destroy for your city? So while money may not be a factor... What else may be?

That's what we've done in the past. It's taken *weeks* to dry the tanks out. I suspect much of this is because we have a lot of "dead ends" in the configuration wherein it's difficult or impossible to get steady flow over certain interior surfaces. Nope. It's just water. All piping is stainless steel. The tanks are steel. No flex lines or anything like that involved. We have had chemical-based desicators in the past (similar to your link, but larger). The maintenance requirements and fragility of the design kills us. We then switched to refrigeration cycle type desicators. They're low maintenance and very robust, but they don't quite remove all the moisture. Oh, I will, but I like getting 3rd party opinions. I've been burned many, many times by vendors who look you straight in the eye and then sell you something that won't work for the application you asked about. Take it to our legal department and they're like, "What? $100,000? That's not even worth our time trying to recover. Call us when somebody burns you for a few million..." Thus, I've learned to take sales reps not with a grain of salt, but with an ore cart full.

At the office I have a few air tanks that combine for a volume of roughly 1200 cubic feet. They are normally used for the storage of 3000 psi air (Note: When I say they're 1200 cubic feet, I don't mean that they hold 1200 scf of air; I mean that they have a combined volume of 1200 cubic feet.). In any event, despite the use of air dryers, we get condensation in the tanks. This is bad (mmmkay?). What I'd like to do: Periodically vent the tanks and then pull a vacuum on them to force any condensation in the tanks to boil off thereby drying the tanks out. Early in the process this should be easy, but as the vacuum hardens (read: pressure reduces to < 0.5 psia) things could get dicey. More to the point, it is my understanding that pulling high concentrations of water vapor through a vacuum pump can destroy a vacuum pump. CAN destroy. Not WILL destroy. Again, it's my understanding that the difference between "can" and "will" in those two sentences is primarily depending upon the type/quality/etc. of vacuum pump. I confess to knowing virtually nothing about vacuum pumps. Thus, with all that said I am asking: Does anybody here know enough about vacuum pumps to recommend one for my situation/application?

Only if you knew that the woman in question had an intense fire fetish and would be turned on beyond belief. Can't say that I've met many women who would be turned on by such a toy, but ya never know....

Composite materials and highly optimized designs (use FEA to remove all unnecessary structural weight).

Every river in the world and it's only good for 13%? Doesn't sound very promising. Might work for niche applications, but that's about it.

Some day we will have the technology to colonize the Sun! See how easy that is to say? Now, do you honestly believe that it will EVER be possible? From my perspective, asserting that we will ever have the tech to send millions of people into space daily is equally believable. You're not even talking science fiction, you're talking pure fantasy. Re-read my post. See where I said, "or you get all the raw materials to the city and build the rocket there?" Yeah, I'm conceding that perhaps you'll want to build the rockets in the city. But it doesn't make any difference, you can't make that rocket out of vacuum. You have to make it out of *something*. That means that you have to get the RAW MATERIALS to your city. Raw materials are hard to come by in space, ya know? Sure there's the odd asteroid, but they aren't exactly known for their diversity. And how do you propose to move that city without a steady supply of reaction mass? In other words... DeltaVelocity = ExhaustVelocity * ln (MassRatio). Please explain the technology you plan to use to invalidate that equation. Trivial compared to the other issues in this post. I never said you would have to send them back to Earth. I said you would have to change orbits. Like it or not, moving from one asteroid to your city requires enormous amounts of energy (ie, you have to change orbits). That right there makes the process "ridiculously expensive." In other words, you're back to that DeltaVelocity equation. Sure. And all it takes is a space ship that weighs in at 10^22 kg and was gifted to us. Find a way to replicate that cheaply. I'm not assuming building in your backyard tomorrow. I am, however, assuming that we more or less have the Laws of Physics down. Now, if you're saying we get to throw out those laws then I propose that this isn't a topic on the future but rather a topic on creative writing.

Yeah, but war is expensive. Disease is cheap though.

Nah... Over population is self correcting and very cheap to correct. It's called "famine."

And you're fooling yourself if you think space is the answer to over population. Global population increase is roughly 1% per year. There are 7,000,000,000 people on Earth. That means that to simply maintain our current population we would have to launch 191,000 people PER DAY into space. Every day. Not gonna happen. Space may be the answer to a lot of problems, but that ain't one of them. Yes, yes, I can. You're forgetting a little something called logistics. It's all well and good to say that you're going to launch a rocket from your orbiting city and that this would be cheap but you're forgetting that you first had to get that rocket to the city. Whether you build that rocket on the ground and launch it to the city or you get all the raw materials to the city and build the rocket there is largely irrelevant... You still have to get the mass to the city in the first place and that has never been a cheap/easy proposition nor are there any realistic proposals to make it cheap/easy in the future. You say that like we don't already have such. We do. Space mining will be ridiculously costly. Period. I'll grant the exception for (say) a mine on Mars with intended usage for the mined materials being the Mars colony next door. But once you start talking about moving the mined materials from one orbit to another you're talking about ridiculously expensive. Tell ya what... As a dry run, build a self-sustained city in Antarctica. Or maybe 500 feet under water at the bottom of the ocean. Either of those tasks will be ridiculously easy compared to any orbiting platform. And yet....

Granted, it's not something I've studied extensively but.... My understanding is that the advantage of current generation airborne space launch platforms has less to do with the 900 km/hr velocity boost and more to do with the ability to hit *ANY* orbit at *ANY* time. IE, "infinite" launch windows and minimal course corrections to hit an orbit.

And sticking your hand in one can hurt like a mutherFer!

I believe Lego makes a whole line of toys that are geared towards children and robotics. They're programmable and advanced enough that (IIRC) there are college competitions where the ground rules are that everything in the robot has to be made by Lego... But they're still simple enough that a child can do it.

It will tell you how fast the other guy's head will snap back when you hit it.

Missed this post until just now.... True, the rise is potential energy and it would provide a minimum value, but the energy contained in a punch is not likely to be efficiently converted to potential energy in the pendulum. Significant amounts are going to be lost to things like deformation of the tissues of the hand/arm. You know, watch high speed video of a punch. See all the waves moving through the flesh? That represents energy that will not show up in your pendulum. In other words, while energy IS conserved, that doesn't mean it is effectively converted to kinetic/potential energy within the pendulum. Momentum, on the other hand, *is* effectively converted.

Well, you could argue that it's semantics but... "Energy" has a very specific meaning in engineering. "Force" has a very specific meaning in engineering. "Impulse" has a very specific meaning in engineering. You've been trying to use the words somewhat interchangably, but none of those three words mean the same thing and they can not be used interchangably in an engineering context. So.... Could you use a ballistic pendulum to measure impact energy? Not without knowing the precise mass (which we don't). Could you use a ballistic pendulum to measure impact force? No. Could you use a ballistic pendulum to measure impact impulse? Yes.

No, that's not how a ballistic pendulum works. It doesn't measure force. It measures momentum (aka impulse). Nope. You could produce a scale that says... Height A = Impulse A Height B = Impulse B etc. ....But that's not the same thing as force. Force. Momentum. Apples. Oranges.

Not really. If you were talking about a bullet or something? Sure, you could. But you're asking about a punch. With that in mind... What is the effective mass of the "projectile?" Is it just the hand? The arm? How much of the shoulder's mass would be involved? The torso? Much is going to depend on body build and technique. Thus, while you could in theory come up with some energy numbers, I would put precisely zero faith in them. Are you familiar with the concept of a ballistic pendulum? Here, read the wiki article. There is no need to produce a scale. You just measure the mass of the pendulum and how high the pendulum swings. True, there's still the issue of the mass involved, but you don't really care. Mass is only needed if you want to back out a velocity. But if you're just interested in *impulse* (ie, momentum), simply using a heavy pendulum will minimize errors.

Not necessarily. Just because the water flows up doesn't mean it actually does anything once it gets there. If it's a continuous flow, OK, it's interesting. But if the liquid simply fills in the groove in a manner similar to wetting action (what the article implies) then there isn't any energy to be extracted.