Macross Frontier Mecha/Technology Thread III *Read 1st Post*

[DarkReaper]

The project pluto link I posted has some info on thermonuclear scramjet propulsion, maybe that's a good place to start.

[sucker4meltrans]

i want to know why no series/episode of macross has been about the ethics of humanity being able to grow full grown adult clones that can have their minds programmed?? imagine the market that could exist for made to order meltran companions.

[daflip702]

i heard that Kawamori designed this particular VF-25 to be not of any "remake" of modern aircraft. I say a good way to start would to deal away with the intakes....so much sleeker in which he intended. That's how i would do it. Plus, that type of design would actually be more aerodynamically efficient.

Well in ep21 we all saw that alto made a VTO in gerwalk mode without any significant proof of any assistance/thrust from the super pack.

If a Valk can fly and sustain hoving capabilities with a Pack on and without air consumption, then why not get rid of the intakes....Id rather use that extra space to build a better propulsion system. Modern-day (meaning 2008)Nuclear engines don't neccesarily need air....they need exhaust vents....and a good cooling system.

It can fly by simply using it's own on board propellant. The only reason for the intakes is to allow the plane to conserve its on board propellant by using the air around it when in an atmosphere.

You mean to tell me it's smater to cut off the intake tract when it's needed the most? It takes more energy to lift that heavy badboy and that it's in a planet-like condition, not like the vaccum of space where any object can be propelled. Please explain. I understand that whole conserve theory when the Valk is naked and in planet-like conditions....but did you ever hear a VF-1 pilot complaining about having to "refuel"? Nuclear is an abundant energy source that lasts for a very long time. Let's just throw that out the window.

Also, of course the VF-25 can fly without air intakes. It's a trans-atmosphereic fighter craft after all, capable of operation both in the atmosphere and in space. The VF-25 has an internal cooling system and reaction mass for propulsion in a vacuum like any other Valkyrie. It's not anime magic; that's the way the variable fighters were designed from the VF-1 onward.

again...why even have intakes....apparently the 25 can VTO with the pack on just fine.....just redundant IMO

i'd just love to see a schematic on how a nuclear reactor based engine produces jet like propulsion....

Well i hope that valks has the proper radiation shielding or is that anime magic? The VF-1 was made from anime magic....BTW the shielding is very,very heavy. RAH-JAH DAT!!!!!!

[hobbes221]

daflip702,I think what people are saying about the 25 being able to fly with its intakes closed while in an atmosphere is that while it can, we have no idea as to how long the propellant would last or any other problems that might be caused. So it would be a more of a use only in emergency type thing something like an afterburner, you can use it just not all day. On a side note I like having intakes on them, keeps them a little more real to me. (and gives me more to think about as to how they work.)

And I will be working on a theory for the VF's engines so any and all ideas are welcome.

[daflip702]

and this "propellant" is?

[badboy00z]

I wonder how VFs can attain the speed that they do in GERWALK mode with just the vernier thrusters?

[DarkReaper]

The propellant could work like in Project Helios, the matter/anti-matter reactors (Pair annihilation) they use should be energetic enough to flash vaporize nearly everything.

Edited September 4, 2008 by DarkReaper

[Mr March]

Because the Valkyries are not just spacecraft; they are aircraft as well. Hybrid designs, hence why they have intakes. It makes sense that they'd sacrifice some maximum speed in an atmosphere for the trade-off of unlimited fuel and range.

As for what the propellant is, apparently it can be almost anything. The way they describe OvertTechnology Reaction engines, they can use both nuclear or non-nuclear reactant. See the Macross Compendium entry on the Thermonuclear Reaction

[J.T. Silversmith]

I have to admit I was one of the people who misunderstood the wording in the Macross Compendium, and I thought the engine output of the '19 was limited in outer space and not in an atmosphere. That made sense to me because a vacuum is a very good insulator, and thermal regulation is one of the major concerns in real world spacecraft design. In the space shuttle the inside of the cargo bay doors are radiators and as soon as it is in orbit the doors are opened to help keep the ship cool. In an atmosphere air molecules come into contact with a hot object, and pick up some of the heat. the hot air moves away by convection currents and more cold air replaces it. the cycle continues, and the object cools off. In a vacuum there is no medium to help carry away the heat, so it can only use infrared heat radiation to dissipate heat, and that is very slow. So I thought the '19 was not as fast in space, but that is not the case it is limited in an atmosphere. Since outer space is so terrible for cooling purposes, the mechanism for keeping the engines cool must be completely internal.

To me the most likely means of keeping the engine cool in a vacuum is to use the propellant itself. So if the '19 is faster in space than in an atmosphere, it means that the propellant used to produce thrust in a vacuum is more efficient at cooling the reactors than the air is in atmospheric flight. I think that would make sense if the propellant is a liquid, it will be able to transfer a lot more heat than a gas. so simply put, the '19's engines are so hot that there is no way to keep them cool at full power using only air as a coolant, but in space the propellant used can keep the engines from overheating.

We know the '19's engines can work as a jet and a rocket, so it is logical to ask, as some people are asking, why have a dual system if the engine is more powerful in rocket mode? Simple, it uses internal propellant in rocket mode, and uses the atmosphere as a propellant and coolant in jet mode. Therefore you have unlimited range in an atmosphere, and a limited duration of propulsion in outer space.

Given how radiation conscious they seem to be on Frontier, I think is is safe to assume the exhaust from a valk is not radioactive, so either the there is a heat exchanger or the OTM thermonuclear fusion reactor output is "clean". I would also assume that the exhaust temperature of the engine is relatively low, based on the lack of collateral damage to streets and pedestrians by VFs in gerwalk mode.

[Bartagama]

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.

[ChronoReverse]

The only problem is that if the exhaust is as high velocity as you (and some others have) suggested, then the same exhaust would be incredibly dangerous. They'd be like weapons in of itself which is clearly not the case in Macross.

In the end, it might just have to be left as Macross Superdimensional Energy Magic

[David Hingtgen]

Some valks clearly have thrusters used primarily for forward thrust in GERWALK mode---the VF-1 and YF-19 for instance. Others, I figure they're kind of hidden--there's lots of "undetailed, in shadow" areas in GERWALK mode drawing. What's directly above the belly plates at the rear of a YF-21 is never shown for fighter mode, it's ALWAYS in shadow. Same for some other areas of other valks in GERWALK. GERWALK has always gotten the least detail/drawings AFAIK---the only reason we see it so much in Zero and Frontier is because they have a fully rendered 3D model to work from. How often do you get a good rear/belly view of a VF-1/11/19/21 GERWALK?

Also, with how much thrust they have, just a bit of vectoring can create quite a bit of forward thrust. And the faster they go, the more they can vector it backwards, as they transition from engine-based to wing-based lift.

[Bartagama]

The only problem is that if the exhaust is as high velocity as you (and some others have) suggested, then the same exhaust would be incredibly dangerous. They'd be like weapons in of itself which is clearly not the case in Macross.

In the end, it might just have to be left as Macross Superdimensional Energy Magic

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).

[David Hingtgen]

Yup, at its simplest, thrust is simply mass times velocity. And much like the most powerful current jets being the quietest/coolest, the most powerful ones also have the most mass going the slowest. (as opposed to a 1960's jet, which tried to move the air as fast as possible)

Caveat: A plane's exhaust MUST be faster than its forward speed, or you will have no net thrust. If you want to go mach 3, you better have a mach 4 exhaust...

But if you're just hovering around in GERWALK, you could have an exhaust of only a few hundred knots, just very high mass air flow. I'd expect valk engines can switch between "high mass" and "high velocity" modes---the F120/F136 engine can do it in real life, and it is "the way of the future" for fighter jets. (and a Concorde replacement)

[ChronoReverse]

That's the thing, where's the mass?

In an atmosphere, you can draw air and that solves a lot of the problems, but what about space? If you carry a lot of mass for propellant, then the fighter is too massive to maneuver well. A solution would be to use light propellant at higher velocity but that makes the exhaust a knife (literally).

Therefore, they must have some kind of way around this hence my superdimensional energy crack =)

[d3v]

i'd just love to see a schematic on how a nuclear reactor based engine produces jet like propulsion....

Well i hope that valks has the proper radiation shielding or is that anime magic? The VF-1 was made from anime magic....BTW the shielding is very,very heavy. RAH-JAH DAT!!!!!!

Thank heavens then that thermonuclear reactors, aka fusion reactors run on simple hydrogen, and not something radioactive (Uranium or Plutonium) like a modern day fission reactor.

Edited September 5, 2008 by d3v

[Mr March]

Some valks clearly have thrusters used primarily for forward thrust in GERWALK mode---the VF-1 and YF-19 for instance. Others, I figure they're kind of hidden--there's lots of "undetailed, in shadow" areas in GERWALK mode drawing. What's directly above the belly plates at the rear of a YF-21 is never shown for fighter mode, it's ALWAYS in shadow.

There is nothing but hull in that particular section. In GERWALK mode pictures - where the rear of the YF-21 remains unaltered - you can clearly see it's simply a diamond-shaped portion of the rear fuselage, which would be the same as fighter mode. The YF-21's "GERWALK thrusters" are 2 x banks of pivoting slit nozzles (ventral fuselage) for GERWALK mode VTOL. They sit inside the rear ventral fuselage just above the legs (GERWALK mode ventral rear).

[daflip702]

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.

Professor are you enjoying yourself?....can you tell the class how much hydrogen will it take to produce thrust that will propell a Valk as intended? How bout you d3v, you want take a stab at it? Maybe you can start by measuring the kinetic output of the gas. Would it be more efficient than using combustable fuel and air in a ramjet turbine? Inquiring minds want to know!!!!!

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.

Ahh solar propellant.....to create momentum by harnessing light energy to push an object. Id rather use "reflective-like" sails to gather light energy much like a sailboat that uses wind energy. Koo....but aesthetically, looks like crap for a fighter plane.

Thank heavens then that thermonuclear reactors, aka fusion reactors run on simple hydrogen, and not something radioactive (Uranium or Plutonium) like a modern day fission reactor.

Kawamori switched to Thermonuclear because it was considered "taboo" to use just Nuclear weaponry in which he originally intended.

[sdf2501]

I asked this question in the ep 22 thread, but figured this would be a better place to ask it.

In ep 22, the VF-171s that Luca and Alto were flying were transmitting Skull 3 and 4's IFF. I thought a particular IFF was tied to the fighter and not the pilot. Can anyone explain this? Is an IFF signal being emitted by their flight suits or EX-gears? A particular pilot log in? Or is it the power of plot?

[RedWolf]

I asked this question in the ep 22 thread, but figured this would be a better place to ask it.

In ep 22, the VF-171s that Luca and Alto were flying were transmitting Skull 3 and 4's IFF. I thought a particular IFF was tied to the fighter and not the pilot. Can anyone explain this? Is an IFF signal being emitted by their flight suits or EX-gears? A particular pilot log in? Or is it the power of plot?

Nah You can change the IFF. Alto and Luca punched their IFF codes in their VF-171.

[badboy00z]

There is nothing but hull in that particular section. In GERWALK mode pictures - where the rear of the YF-21 remains unaltered - you can clearly see it's simply a diamond-shaped portion of the rear fuselage, which would be the same as fighter mode. The YF-21's "GERWALK thrusters" are 2 x banks of pivoting slit nozzles (ventral fuselage) for GERWALK mode VTOL. They sit inside the rear ventral fuselage just above the legs (GERWALK mode ventral rear).

I like how there's absolutely no way the legs can fit inside the fuselage in that picture. Got to love line art. Lol. Also does the feet provide thrust?

[Final Vegeta]

I like how there's absolutely no way the legs can fit inside the fuselage in that picture. Got to love line art. Lol. Also does the feet provide thrust?

The engine block moves forward in GERWALK and Battroid mode. Also the feet retreat inside the calfes while stored in Fighter mode.

Yes, the feet provide thrust.

FV

[Kurisama]

I like how there's absolutely no way the legs can fit inside the fuselage in that picture. Got to love line art. Lol. Also does the feet provide thrust?

The engine block moves forward in GERWALK and Battroid mode. Also the feet retreat inside the calfes while stored in Fighter mode.

Yes, the feet provide thrust.

FV

Ignore the shameless self promotion - but, one thing when I found while modeling a YF-21 a few years ago, is that the legs certainly have a hard time fitting inside the cavity - while still retaining the anime look. With this model, I used the Hasegawa colour guide for the 1/72 as a template - so I'd imagine it'd be pretty accurate to SK's vision. So I went with going about making a working model without compromising the look in it's final battroid mode. It's not going to happen unless there is some anime magic.

I was also wondering how the VF-25 can propel itself so fast forward without a really visible rear facing engine...

EDIT; The 50% and 100% in the pic indicates that the bottom bits of the plane that form the hip-wings on the '21 needed to be scaled by 50% to look more accurate and less cumbersome.

Edited September 5, 2008 by Kurisama

[Bartagama]

Professor are you enjoying yourself?....can you tell the class how much hydrogen will it take to produce thrust that will propell a Valk as intended? How bout you d3v, you want take a stab at it? Maybe you can start by measuring the kinetic output of the gas. Would it be more efficient than using combustable fuel and air in a ramjet turbine? Inquiring minds want to know!!!!!

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.

Ahh solar propellant.....to create momentum by harnessing light energy to push an object. Id rather use "reflective-like" sails to gather light energy much like a sailboat that uses wind energy. Koo....but aesthetically, looks like crap for a fighter plane.

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.

Kawamori switched to Thermonuclear because it was considered "taboo" to use just Nuclear weaponry in which he originally intended.

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.

[d3v]

Professor are you enjoying yourself?....can you tell the class how much hydrogen will it take to produce thrust that will propell a Valk as intended? How bout you d3v, you want take a stab at it? Maybe you can start by measuring the kinetic output of the gas. Would it be more efficient than using combustable fuel and air in a ramjet turbine? Inquiring minds want to know!!!!!

How about the fact that once it's moving, a valk doesn't have to burn propellant thanks to Newtons laws. Plus, if the propellant is hydrogen, it's bound to be stored in liquid form compressed in tanks (which is the safer method). As for the reactor itself, the power output of a fusion reactor is such that you'd only need a small amount of actual reactor fuel to power the plane.

Kawamori switched to Thermonuclear because it was considered "taboo" to use just Nuclear weaponry in which he originally intended.

Now, they used the term "reaction" for anything that was meant to be refer to standard nukes. Kawamori and his crew have specifically stated nuclear fusion, specifically pair annihilation as what powers valkyries. Besides, the Japanese have been using the concept in their mecha anime since the late seventies (mobile suits from the original Gundam are powered by fusion reactors as well, fueled by Helium-3 harvested in Jupiter).

You have to consider that with most older mecha series, the creators are fans of sci-fi and strived to give their the same level of details and groundedness in science (or at the very least, psuedo science) as the authors they looked up to.

Edited September 5, 2008 by d3v

[Final Vegeta]

Ignore the shameless self promotion - but, one thing when I found while modeling a YF-21 a few years ago, is that the legs certainly have a hard time fitting inside the cavity - while still retaining the anime look.

Yeah. The Yamato newest toy also shows the best you can get, at least in Fighter mode (not considering the fact that Battroid mode's proportions were different in the anime). GERWALK mode is not the best to see the space available for the legs, though because the parts change while transforming.

By the way, I was surprised that in the toy the feet were actually visible from behind, but the lineart in fact never showed some cover for the area.

I was also wondering how the VF-25 can propel itself so fast forward without a really visible rear facing engine...

Do you mean in GERWALK mode? There seem to be some verniers on the rear end of the dorsal piece. They don't look much useful for Battroid, though, a design flaw that is corrected by the FAST Packs.

FV

[Master Dex]

I told myself to not post on this discussion of Valk engines because anyone here that knows me knows I would end up with ridiculously long posts and I'd start talking really fast (well you wouldn't really notice that I guess) which usually results it people not even reading what I'm saying because they are annoyed at me or something. I am kind of proud of myself for holding back.

I have been reading it all though and I like it, lot of good information going around, and we have a professor! That's just awesome. I wish my professors (I am studying Aerospace Engineering if anyone forgot) would discuss Valkyrie stuff like this with me, but I doubt any of them know of Macross (anything is possible though).

If you want my quick thing on it, from my knowledge, Valk engines use thermonuclear reactors that heat up the air sucked in from the atmosphere to plasma and thrust it out the end to create propulsion. The nuclear reactors most likely are fusing hydrogen or helium-3 (the best fusion materials most likely, Helium-3 is also in abundance on the Moon btw) for energy. In space there is most likely on board propellant that is also most likely hydrogen like D3v said which would be best stored in liquid form as you can carry most that way. The compendium explains that super dimension space gets involved somewhere with this but I'd rather not concern myself with that stuff as that is just a way to make it even more powerful than the basic form of what I just explained.

That is my 1-2 quick explanation of what I think the Valks are doing with their engines, I have stuck by this. It may or may not be what Kawamori is actually thinking of, but it makes sense to me.

Molto-bene!

[Mr March]

I like how there's absolutely no way the legs can fit inside the fuselage in that picture. Got to love line art. Lol. Also does the feet provide thrust?

The whole rear engine and fuselage section of the YF-21 moves forward during transformation. This is why it appears the interior ventral bays are too small to hold the legs. But when it transforms back to fighter mode, the engines/rear fuselage extends back into place, creating enough length to store the legs. Refer to this picture of the YF-21 transformation (in particular, look at the picture in the lower center portion of the picture which shows a side cutway of the engines/rear fuselage moving forward during transformation).

The legs appear to have thrusters of some kind, but they may only be vernier thrusters. This is likely the case since the main engines mounted on the rear of the YF-21 Battroid would provide lift for that mode. Also, the 2 banks of verneir slits mentioned earlier provide VTOL thrust in GERWALK mode, so lift thrusters in the legs would not be necessary.

[Bartagama]

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.

Edited September 5, 2008 by Bartagama

[DarkReaper]

I guess thats the reason why more modern jets like the YF-19 carry about 40 tons of payload or fuel.

Though the VF-1 is no slouch either with 24 tons of weapons and full tanks.

The standard take-off weight of 18500kg is for atmospheric combat I guess where you only need the hydrogen fuel for short overboost situations and battroid.

Edited September 5, 2008 by DarkReaper

[Shaka_Z]

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.

there is a certain problem with using liquid hydrogen as a propellant in a fighter-sized vehicle (especially one that transforms) - density. in the liquid state, H2 has a density of 68.85kg/m^3... one really can't store very much of it to use as reaction mass, even in a fighter using a fusion engine - at least not and have any kind of useful endurance at max thrust. in cruise however, where the engine would be allowed to really heat things up, the potential for really high Isp levels (and correspondingly high delta-v's over extended periods) would be there. this of course assumes that overtech hasnt solved the problem of getting insane Isp and thrust levels simultaneously - these are usually 2 extremes that do not go well together.

this propellant storage issue is very likely the primary reason why valks before the YF19 and 21 were generally incapable of reaching escape velocity from an earth class planet without booster assistance. dont get me wrong... they were most likely quite capable of it - just not on a tactically useful timescale. it is quite likely that later engine versions like those on the -19 are capable of handling denser fuels without material compatibility issues. my own preferred candidate would be metallic hydrogen

Edited September 6, 2008 by Shaka_Z

[d3v]

I can't recall exactly where, but I remember reading something in another site to the effect that a ton of hydrogen would be able to power a fusion reactor for about 50-80 years depending on the efficiency, they even had calculations and all. But alas, since I don't have the requisite degrees and/or training, I can't really explain in detail how they got to that conclusion.

@Shaka_Z

I mentioned liquid hydrogen since it's currently what many companies in the real world are doing research on. BMW has already revealed a tank that weighs lighter than a comparative steel fuel tank. off course, storing liquid hydrogen in space has its own set of problems, which we'll have to assume are addressed with overtechnology.

Edited September 6, 2008 by d3v

[Shaka_Z]

@Shaka_Z

I mentioned liquid hydrogen since it's currently what many companies in the real world are doing research on. BMW has already revealed a tank that weighs lighter than a comparative steel fuel tank. off course, storing liquid hydrogen in space has its own set of problems, which we'll have to assume are addressed with overtechnology.

it isnt the mass of the tank that is the problem - it's the volume. there is simply no way for a valk to carry more than a few hundred pounds of H2 for propellant use without taking on the appearance of a manatee, and even if it did, that propellant would not last at all long at max thrust levels (forget about carrying several thousand pounds.

[Fade Rathnik]

Why do you have to use the reactor fuel as propellant if its so efficient. Then you could use a propellant that is more stable. What if you used a super cooled inert gas as propellant like Xenon?

[Shaka_Z]

Why do you have to use the reactor fuel as propellant if its so efficient. Then you could use a propellant that is more stable. What if you used a super cooled inert gas as propellant like Xenon?

well, to be honest, no cryogenic propellant is really suitable for something like this - too much special handling and precautions are necessary for use in an operational system (especially considering that most ordnance and fuel handlers are not likely to be trained in dealing with things like that). same goes for the common ion drive propellants like mercury (most are way too toxic for large scale usage).

I would be willing to put money down that the propellant used is good old water, while the fusion turbine itself runs an aneutronic cycle like hydrogen-boron - that way the whole system is as clean as can be from an environmental standpoint, and all the fuels and propellants are easily sourced.

Edited September 6, 2008 by Shaka_Z