Bartagama

I just hope that isn't our only chance to see the VB-6 battroid!

Okay, thanks to a very long and very boring meeting I've had the chance to run some numbers. These calculations are based on the following stats for the VF-1 that I found on the Macross Compendium: reactor power: 650 MW engine thrust: 11 500 kg x g weight, take-off: 18 500 kg weight, empty: 13 850 kg Lacking any data, I assumed an exhaust temperature of 10 000 K, which is about 4 times as high as a ramjet but much much lower than the temperature inside a fursion reactor. [edit: more accurately, I assumed that the kinetic energy of the exhaust is equivalent to 10 000 K; it technically isn't the same thing] I'll spare you the calculations, but the listed value for the thrust leads to a minimum propellant consumption rate of 7.14 kg/s. Assuming that most of the difference between take-off and empty weight comes from hydrogen propellant, this gives 2325 kg of hydrogen per engine, for a maximum flight time of 326 s, about 5 1/2 minutes, at full power, which seems about right. All that assumes that all of the hydrogen is thrown out into space rather than used as fuel, but that isn't a problem: a 650 MW fusion reactor would only consume about half a gram of hydrogen fuel in 326 seconds. That means you can use almost all of your hydrogen as propellant. In an atmosphere, you can use air as a propellant. Based on some quick calculations, an air intake cross-section of 0.1 meter^2 would provide enough airflow for the engines; that seems about right, too. In that case, of course, you don't need to worry about using up your onboard propellant and you can essentially fly forever.

Indeed I am enjoying myself--how can you tell? You wouldn't need much hydrogen to drive a valk; in principle a few atoms could do it. The problem is that it takes time to transfer enough energy to the hydrogen. I've got a meeting coming up this morning, which will give me a chance to do some back-of-the-envelope calculations for what you'd need for a practical engine. Regarding the fuel/air ramjet, all that the combustion does is produce heat to warm up the air passing through; the combustion itself produces negligible thrust. So using a thermonuclear reactor to heat the air would be just as efficient, if not more so (as long as the shielding for it isn't too heavy). Interestingly, the problem of needing time to heat the propellant is an issue for modern jets as well: at high speeds, the air just doesn't spend enough time in the engine to heat up enough. As a result, air intakes are specially designed to slow down the incoming air stream to give it more time to absorb heat in the engine. The SR-71 had an innovative nacelle design for just this purpose, IIRC. Actually, I wasn't talking about a solar sail, but rather using light radiated from the reactor for propulsion. You could use a flashlight to push you around in space, if you were patient enough. Still, light propulsion probably wouldn't work very well; I'd guess that you'd need something of the order of a Macross-class beam to get enough thrust. Is that so? I would have thought that thermonuclear (as in H-bomb) is what he meant all along--it packs much more of a punch than mere nuclear weaponry.

True enough. But you don't need such high-velocity exhaust when you're in an atmosphere, since you have more mass at your disposal. Also, in GERWALK mode the valk can take advantage of the ground effect. To be sure, there's still a lot of anime magic in what we're shown. On the other hand, we did see valk thrusters used as a defensive weapon at least once, when Hikaru tried to fend off Britai in "Blind Game" (IIRC).

I'm really enjoying the discussion of valk propulsion; here's my take on the subject. I'm a professor of physical chemistry, so I can't say much about the engineering aspects of valk engines, but I know a bit about how energy works, and this is a fun problem to think about. Bottom line: within the limits imposed by our materials' ability to withstand heat and mechanical stresses, the designer of an engine faces a trade-off between power and efficiency. Any propulsion system works by transferring momentum. Momentum (mass times velocity) is an object's tendency to keep moving--objects in motion tend to stay in motion. If we want to accelerate our valk, we need to increase its forward momentum. Thanks to the law of conservation of momentum, the only way to do this is to simultaneously increase the momentum of some other object(s) in the opposite direction: if we want to move forward, something else has to move backward (that's what Newton meant by "any action has an equal and opposite reaction"). Think about Hikaru trying to reach the tuna floating outside the Macross: he threw some brick-like objects backward so that he would move forward. In a jet engine, air is what we throw backwards. I'll come back to that. That's also how lift is generated, by the way: by forcing some of the surrounding air downwards, the plane is forced upwards. This means that we need something (call it "propellant") to throw backwards from the valk, and some way to do the "throwing". This is where energy comes in. Kinetic energy is equal to momentum squared divided by twice the mass. That means lighter objects have more energy than heavy objects with the same momentum. If that seems counter-intuitive, think about Hikaru and those bricks again. After he threw those bricks, Hikaru wasn't moving very fast and didn't do much (if any) damage when he bumped into the tuna. But the brick he threw was moving pretty fast and if it hit something could have done a lot of damage (would you like to be hit by a flying brick?). So we'll need energy for our engine: some energy will go into driving the valk forwards; the rest will go into driving the propellant backwards. Valk and propellant are getting the same amount of momentum (in opposite directions), but if their masses are different, then the lighter one will end up with more energy. If we want to be efficient, then we want the valk to be as light as possible and the propellant to be as heavy as possible: that way more of the energy goes into moving the valk rather than the propellant. Overtechnology helps to make the valk lighter, but what about the propellant? Clearly if the valk is restricted to onboard propellant, there are severe restrictions on the amount of mass that can be thrown backward by the engines. In atmosphere, we can use the air around us as propellant: all we need to do is add energy to the air (for example by compressing and/or heating it), and direct the high-energy backward and we're all set. That's how an ordinary jet engine works and is almost certainly how the valk's engines work. To increase efficiency, you'd want to maximize the amount of air that you heat up. That's why commercial jet aircraft have huge high-bypass turbofan engines. Efficiency is less of a concern with a thermonuclear engine, which presumably produces more energy than we would ever need. In that case, we can take a relatively small amount of air and accelerate it to very high speed before throwing it out the back of the engine. The simplest way to do that is by a combination of heating and compression like a normal jet engine, but a magnetic-induction system might also be made to work. In a vacuum, a valk would have to use onboard propellant. If you wanted to be energetically efficient, you'd use a high-mass propellant, but that would weigh down the valk and make it less maneuverable. But since we have a thermonuclear engine, who cares about efficiency? Let's use the lightest propellant possible: hydrogen perhaps. There's no physical limit on the amount of thrust we can get: as the speed of the jet exhaust approaches the speed of light, its momentum (and hence the thrust of the engine) goes to infinity. The only limits on the engine's thrust would come from how quickly we can deliver propellant to the engine, and how quickly we can add energy to the propellant once it's there. One interesting possibility is to use _light_ as a propellant. Presumably the thermonuclear reactor emits light, whether visible, infrared or otherwise. Light has momentum even though it has no mass, so if the light were directed backward, it would push the valk forward. This turns out not to be a very good option, though: a 300 gigawatt reactor (the size of a modern fission reactor), if all of its energy were emitted as light in a single direction, would produce about 1000 newtons (225 pounds) of thrust, which is not much. It might be usable as a last-resort "get me home" propulsion, but not much else. Using the same energy to accelerate matter in a jet would produce at least a million times as much thrust: that's clearly the way to go.

As for me, I felt that the Vajra were cleared away much too easily. Episode 20 was filled with foreboding thanks to the swarming Vajra infestation; I expected them to be around for a while. The Ranka/Island 3/MDE tactic did make narrative sense, but it seemed like a Magic Reset Button to me.

There is a vibrant community of LEGO mecha builders out there, with a wealth of useful ideas for constructing very big robots. A good place to browse is the mecha newsgroup at LUGNET: http://www.lugnet.com/build/mecha/ Keep us posted! Unfortunately, I won't be able to work on my Konig Monster for a while, thanks to a long vacation abroad (the wife won't let me bring my LEGO collection with us ). But you'll be seeing more of it later this summer.

Those uniforms look to be custom-made stickers attached to their torsos. Very cute! Heh, I knew those Harry potter sets must be good for something.

Fokker's Fate: that's pretty cool. I've always thought that the destroids were well suited for constructing with LEGO. How about posting some pics of your Macross minifigs?

Thanks for all the comments. Just to dispel any confusion, my model is real; if it looks like an LDRAW image, that's just a consequence of my wife's talented photography. As far as stability goes, it's pretty good so far. Getting it to balance will be tricky, but I'm sure it can be done. I'm running out of "good" pieces, though, so it may take me a while to put the legs together. That and the fact that I'm constantly tweaking the parts that are already "finished." (Heh, would that be Building Over and Over aGain with Endless Revisions = BOOGER??) I haven't had this much fun in a long time; this project combines two of my first loves, Lego and Macross. - Bartagama, who is not Japanese at all but just realized that his member name does sound a bit like that.

Basel, Switzerland Lat 47.56374691 Long 7.57943275

The links should be OK, at least the "deep links", and they work fine for me. 'Course, Brickshelf might be letting me in because it's my page, but I don't seem to be logged in. Egh. As a fallback, I've also posted the pictures at this site. Hope that works!

I'm still working on my own monster; thanks to everyone for all the encouragement. Once the it is moderated, you can find some pictures of my version in my Brickshelf folder. Until then, here are some deep links: Shuttle Destroid Battroid The shuttle is 32 "studs" (25.6 cm) long, which works out to 1:116 scale. For comparison, Glagla's model is 34 studs long, which would be 1:110. Bigger models are indeed easier to build in some respects, but they require many more pieces. They're heavy, too, which adds a new set of challenges for a project like this. I have to say that I admire Glagla's building style; it's a couple of levels above mine. The smooth surfaces in his model result from what the LEGO community calls "SNOT" construction (for "Studs Not On Top"). My version looks more LEGO-ish because I still use what has been dubbed the "MUCUS" technique ("Mostly Upward Construction Using Studs"). As haterist pointed out, most LEGO building is by trial-and-error, although people can and do create their own printed instructions. It would actually be a fun project to make some instructions for this guy, if there is much interest.

Well, that takes some of the wind out of my sails. I've been working on my own LEGO Konig Monster for a while now, but it's still a work in progress. I'm trying to follow Kawamori's sketches as faithfully as possible, rather than basing my design on the resin model, as this guy seems to have done (down to the color scheme ). FWIW, my model is at the same scale as this one, about 1:110, so it should be comparable in size to the Yamato version. I'll post some pics tonight if anyone wants to see them. I've got a 1:48 version on the drawing boards, but that project will wait until I've worked all the kinks out of the smaller one.