Can battroids fly?

[grebo guru]

Ahoy,

Yeah, this is probably a stupid question. Still, I'm gonna ask it.

Can Battroids fly?

I'm not talking about booster-assisted jumps, and I'm not talking about zero-G. I'm talking about sustained atmospheric flight.

I'm pretty sure I've seen them do it in plenty of animated segments, but then again, I've seen a lot of Mobile Suits do the same thing -- and technically, regular Mobile Suits are not supposed to be able to fly in atmosphere. According to their specs, traditional MSs can perform rocket-boosted jumps and can (of course) fly in space, but in atmosphere? No.

I'm fairly sure Battroids are supposed to be able to fly, but I just wanted to check.

Thanks!

Grebo

[Macross73]

You know i cant think of a time when a Battroid stayed up in the

air for an extended period of time. I can only recall short jumps.

Mostly i recall Battroids "flying" in space.

[The6ftTallAZN]

I dunno, but I would say no (I know I don't know much about planes and stuff ) because wouldn't a battroid need wings and a certain amount of lift to be able to fly in an atmosphere? Or something along those lines, maybe just extending the wings

[kensei]

In the final Pineapple salad and also the second last ep of SDF Macross there is an example of Battroids flying in the air.

[sketchley]

First episode of Macross Plus too (VF-11, YF-21.) Battroids ARE able to fly. The prime limitation is the same as the Harrier - engines overheating when hovering in place. The compendium has some specific times (usually for gerwalk), but the anime routinely ignores them. So...

[Roy Focker]

Yeah they can fly. It happens a few times in Macross TV (and not the anime friend episodes). Of course they don't seem to fly was good as say in fighter mode.

[azrael]

Roy flew his VF-0 in battroid mode in M0....

[The6ftTallAZN]

Roy flew his VF-0 in battroid mode in M0....

O yeah I forgot about that

[op4_delta]

Indeed he flew it, but as I understand even with wings extended, the aerodinamic capabilities are not as good as in fighter mode and compensating this with the engine´s thrust consumes more fuel.

Edited November 5, 2006 by op4_delta

[sketchley]

The question asked was 'can they fly', not 'how well can they fly.'

How do they fly? Engine thrust alone.

[David Hingtgen]

Which technically isn't flying... (The wings make NO lift in battroid mode, extended or not---they're only spread out in battroid mode so the missiles have room)

With the power valks have, there really shouldn't be any time limitation for hovering. If the Harrier could shed 2,000lbs it could hover for as long as it had the fuel to do so.

GERWALK mode is far more interesting, for the feet are delivering vertical thrust, and all forward thrust is from the backpack, thus the wings also develop lift so long as you're moving forward. (so you should actually have the most lift in that mode) And as we see in M0, aerodynamic controls certainly play a big part.

[sketchley]

Max hovering time: using 13000 kg [x g] x 2 thrust 70 seconds

using 11500 kg [x g] x 2 thrust 420 seconds

http://macross.anime.net//mecha/united_nat.../vf1/index.html

It has nothing to do with weight, but everything to do with cooling (in regards to the Harrier.) In fact, the Harrier carries water to cool it's S/VTOL systems, and it is when that water runs out that the jet can't use the S/VTOL system without risk of series damage.

[David Hingtgen]

It has everything to do with weight. There is no "V/STOL system", it's simply water injection. Old and simple way to temporarily increase the thrust of jet engines. You get increased thrust for as long as you have water to inject. There's a zillion Harrier variants out there, and an equal number of engine variants, but here's an example:

Harrier weighs 20,000lbs. Engine normally can put out 19,500lbs of thrust---not enough to takeoff or hover. But with water injection, thrust can be boosted to 20,700lbs. That's enough to take takeoff. But it only carries enough water to do that for 60 secs.

But if the Harrier only weighed 18,000lbs, then the engine at 19,500lbs of thrust could easily lift it, without resorting to water injection--and it could keep it up for quite a while. 19,500lbs would probably be the 5 min takeoff limit, but if the Harrier was that light, you could probably have the engine set at max continuous thrust--which is exactly that, and the Harrier could hover indefinitely.

Harriers use water injection for both power and cooling---but the more you overstress the engine, the more it's relied on for cooling. But it still comes down to weight--if the plane weight less, the increased thrust wouldn't be needed, and the engine wouldn't have to work as hard, and it'd have no cooling issues at all. Every little bit weight at the upper end makes the engine work a LOT harder to get that extra thrust to carry the weight.

Weight=more power and fuel needed. (even in level flight) More power=more heat. Cooling issues are the result, not the cause.

[sketchley]

Thank you, but could you please explain how adding water to fire (engine exhaust) makes for more thrust. Logic has me thinking that the fire (thrust) would be reduced, as water generally puts out fire (stressing generally, because there are some elements that react more when water is added.)

To help you: what I have seen is that the water is used in cooling the engine, and the parts of the vehicle that redirect thrust downward. I also know that the Harrier sometimes sucks hot exhaust into the engine, causing a backfire, of sorts.

[myk]

Can't wait for Dave's response.

Anyway no, Battroids can't fly because they're not real...

[David Hingtgen]

The heat the engine makes has little direct influence on thrust. The most powerful jet engine ever built is among the coldest-running ever built. Heat=noise and fuel consumption, mainly. The goal is to make thrust, not heat the atmosphere. Heat coming out of the engine is basically "wasted fuel energy"---it would have been better for that heat to be converted to kinetic energy to increase the velocity of the exhaust.

Jet engines have always preferred dense air, it directly influences thrust produced. Every jet in the world has a "engine performance based on density of the outside air" chart. Density of air is affected by temperature. Cold air=denser.

Airliners were the main users of water injection, but no longer. If it was really cold out (below freezing or so) you could operate the engine at "water injected thrust levels" without actually using the water--because the air was so cold and dense anyways, water injection would be pointless (and it might freeze).

Anyways, the water is injected in the compressor section, not the combustion section. The point is to increase the density of the airflow. Thrust is change of momentum, momentum=mass x velocity. (that is how a jet engine works, nothing more--mass and velocity of the air---not its temperature)

Anyways, say you inject water into the airflow going into an engine. As the air is compressed, it heats up. It'll heat up enough to vaporize the water. The water didn't heat up by itself, the heat was transferred to the water from the air. So the air is cooled.

Ideal gas law (chem 101): p=p/Rt or Density=pressure/(R*temp)

If temp goes down, density goes up. Increased density means more mass per unit time. Since thrust only cares about mass and velocity, more mass at the same speed means more thrust. The short version has always been "the water fools the engine into thinking its sucking in more air than it really is".

Cooling effects and reasons (and how the Harrier uses it and why) are another topic, I'll post that tomorrow. (Nitty-gritty jet physics are always taxing---I have to get my books out to get the formulas right, etc)

PS--water injection often leads to black exhaust, a big reason it's no longer used. Not simply "smokey" like many old jets are, but BLACK, like this: http://www.airliners.net/open.file/0541868/M/

[jenius]

I was wrong

Edited November 5, 2006 by jenius

[F-ZeroOne]

Further to Davids comments on the Harrier, the old role-playing game Cyberpunk 2020 actually used Pegasus engines - the same as in a Harrier - to create flying vehicles; IIRC the rulebook specifically mentioned that they were able to do this this because of the engine thrust alone and not having to haul round a full size jet body. I can't remember what they called these flying vehicles, though - aerodynes?

[Graham]

While Battroid mode flight time with early VFs certainly seems extremely limited, that certainly doesn't seem to be the case with the more advanced VFs that have insane thrust to weight ratios, such as the the Mac Plus& Mac 7 Valks. There's lots of Battroid mode flight shown in M7.

Graham

[Mr March]

I think there's at least one example of Battroid flight in almost every Macross show. Max flew his Valkyrie in battroid mode fighting Milia within the atmosphere in SDF Macross. There are several examples of atmospheric battroid flight in Macross Zero, typically Roy and Ivanov. In Macross Plus, both the YF-19 and YF-21 meet in the air and hover in battroid mode.

With the insane amount of power and thrust available to the Valkyries, hovering in any mode shouldn't be a concern. The durations given in the official literature don't sound realistic for the Valkyries nor representative of the anime.

[grebo guru]

Heyyyy, a fellow Cyberpunk 2020 player! (Have you seen the third edition? It SUCKS!) Anyway, you're talking about the AV-4 and its many variants. CP2020 generally referred to these pure-thrust flyers as AVs, but they did also call them Aerodynes (AV = Aerodyne Vehicle?). Although, technically, "aerodyne" is an awfully vague and broad term to use for such a specific type of vehicle. But yeah, these Pegasus-powered "flying trucks" were basically CP2020's "poor man's Spinners" (spinner = cool flying cop car from Blade Runner). In Cybergeneration, set 7 years later, actual Spinners were introduced -- they used some kinda super-fancy micro-engines.

Anyway, I'm really enjoying this thread! I didn't expect such fascinating replies... I was really just expecting responses like, "Duh! Of course Battroids can fly, moron!" Nice to see my question wasn't as lame as I thought it might be.

Grebo!

Further to Davids comments on the Harrier, the old role-playing game Cyberpunk 2020 actually used Pegasus engines - the same as in a Harrier - to create flying vehicles; IIRC the rulebook specifically mentioned that they were able to do this this because of the engine thrust alone and not having to haul round a full size jet body. I can't remember what they called these flying vehicles, though - aerodynes?

[F-ZeroOne]

Heyyyy, a fellow Cyberpunk 2020 player! (Have you seen the third edition? It SUCKS!) Anyway, you're talking about the AV-4 and its many variants. CP2020 generally referred to these pure-thrust flyers as AVs, but they did also call them Aerodynes (AV = Aerodyne Vehicle?).

Anyway, I'm really enjoying this thread! I didn't expect such fascinating replies... I was really just expecting responses like, "Duh! Of course Battroids can fly, moron!" Nice to see my question wasn't as lame as I thought it might be.

Grebo!

I wouldn't go quite so far to say I played - I dabbled in RPGs when I was younger but probably spent more time reading the rule books than actually playing!

"AV" may also have been a tribute to the Harrier, as in US service the Harrier is "AV-8" (Attack VTOL...?).

As to the replies, if theres anything likely to start a detailed conversation on Macross World, its anything involving aircraft and thrust-to-weight ratios certainly fits the bill!

Just touching on Gundams again - in the original series, I'm reasonably certain that in atmosphere, the Gundam "leaped" rather than flew (except in space colonies, I think, because of reduced gravity at the end-caps), but this rule appears to have been relaxed as time has gone on. I think in the much later SEED series, although in early episodes Mobile SUITs are seen leaping, as the series goes on this also seems to be more and more ignored (although some MS appear to be full-flight capable anyway... )

Edited November 5, 2006 by F-ZeroOne

[evirus]

Ahoy,

Yeah, this is probably a stupid question. Still, I'm gonna ask it.

Can Battroids fly?

I'm not talking about booster-assisted jumps, and I'm not talking about zero-G. I'm talking about sustained atmospheric flight.

I'm pretty sure I've seen them do it in plenty of animated segments, but then again, I've seen a lot of Mobile Suits do the same thing -- and technically, regular Mobile Suits are not supposed to be able to fly in atmosphere. According to their specs, traditional MSs can perform rocket-boosted jumps and can (of course) fly in space, but in atmosphere? No.

I'm fairly sure Battroids are supposed to be able to fly, but I just wanted to check.

Thanks!

Grebo

i think that battroid are only capable of "falling with style" as buzlightyear would put it.

[David Hingtgen]

Quick comment:

"AV-8" is one of the "wrong" designations in the US military that really doesn't fit/conform. It's out of sequence and the letters are backwards, or both. It's often said it might actually be a joke---A V 8. Aviate.

[sketchley]

Thanks David, I look forward to your input on cooling effects and reasons.

As for why the VF-1 cannot hover in place for very long - I believe the answer has to do with cooling of the engines. It's best to keep in mind that VFs (aside from the VF-0, and SV-51) have thermonuclear engines. The only real further explanation that I have come across is in the compendium's write-ups for the YF-19, VF-19, YF-21, and VF-22:

In atmosphere, the engines use air as coolant/propellant, but due to problems of cooling efficiency (caused by exceeding output and melting the core) the maximum thrust is limited to 40% to 60% of thrust in space.

http://macross.anime.net//mecha/united_nat...yf19/index.html

The implication being that an AVF could hover longer in an atmosphere, with potentially greater loadouts, than in places without an atmosphere.

As there is little to no further information on the VF-1, my suspicions rest on the engines having a lower thrust output, and lacking the ability to suck in more atmosphere - thus forcing them to rely more on reactant to keep the engines going, thus causing them to overheat. Though the lack of mention in the write-ups for the AVFs doesn't mean that they could have a similar limitation (relying on reactant as not enough atmosphere can be sucked into an unmoving engine.)

Edited November 6, 2006 by sketchley

[David Hingtgen]

Ok, part 2 of how water injection works. This is going mostly on memory, as the cooling function (as opposed to mass increasing) tends to be glossed over in most references I can find.

The first part described how the water cooled the air to directly increase mass, thus increasing thrust. Now we get to the other way. (Water injection is a 2-for-1 deal)

Jet engines are usually limited in their power by the turbine inlet temperature (TIT)--seriously. (it could also be considered the combustion chamber exhaust temp) The first stage of the turbine is where the blades will be the hottest, and is thus the limiting factor. Exhaust gas temperature is also a common limit, particularly when stating the engine. (Jet engines usually have multiple red-lines---different places and different numbers under different conditions)

A jet's turbine exists to extract power from the heat of air passing through it, to turn the compressor. The more heat in the air, the more the turbine can get power to turn the compressor. You get more heat by burning more fuel, but jet engines at full power are operating at the absolute limit of the turbine blades' ability to withstand heat.

Most of the air passing through a jet's core goes to cooling--not to be burned with fuel nor contribute to thrust. Jets are air-cooled, for obvious reasons. Combustion chambers and turbine blades have amazingly complex passages for cooling---but they can only cool the turbine so much.

Assume that for "X" amount of air, "Y" amount of fuel can be added and burned, increasing the energy of the air. Note that due to sheer compression, the air entering the combustion chamber can easily be several hundred degrees hotter than ambient. However, if said air was cooled (say 100 degrees) before getting to the combustion chamber, you would "gain" 100 degrees that you could heat via the combustion chamber by adding more fuel. (since cool air is denser, there is effectively "more air", thus countering the loss of kinetic/heat energy in said air)

More fuel being burned (without exceeding the TIT limit) results in a faster-spinning turbine, which turns the compressor faster, thus sucking in more air, faster---which is what makes thrust.

Alternatively, you could just inject the water directly into the turbine, cooling it that way (which will also increase the mass, but at a later stage than injecting water into the compressor)---I believe this may be how the Harrier operates, as the Pegasus engine is quite unique in that it has 4 exhaust nozzles, with the forward two operating purely off bypass air, and the rear two purely off of core air. Adding water increases mass and cools, period---but where you add it will affect the ratio-----cool a lot and increase mass a little, or vice-versa. All depends on how the engine is designed, and what you need---pure cooling, more mass, etc.

If nothing else, always remember that a jet engine makes thrust by MOVING AIR. Nothing more. It cares about how much air, and how fast the air is going.

10lbs of air moving 200mph produces the same amount of thrust as 2lbs of air moving 1000mph. Due to various factors (speed of the aircraft, altitude, etc) airliners tend to favor lots of air, slowly, and fighter jets prefer less air, quickly.

Burning a lot more fuel results in spinning the blades faster, thus pumping the air faster----hotter air doesn't increase thrust by itself. It's easy to build a very, very cool-running jet engine--just use an electric motor to spin the compressor, instead of a combustion chamber and turbine---it's how many model jets fly.

[Zinjo]

I feel like I'm in school!!

Thanks for the info DH, very informative!

[sketchley]

Ah, thanks. I think I understand it.

Though there is one question I have: I have heard that the Harrier (Pegasis) engine uses water only while hovering. Did I hear that wrong, or is it related to the 'adding more into the engine to get more thrust out of it'?

[David Hingtgen]

I'd certainly suspect it of using water to takeoff vertically as well, as that requires even more thrust than hovering. It's not some special ability that water lets it hover, nor that it requires water to hover (60 sec water supply, but can hover over 5 minutes)---it's just that water injection is so rare nowadays. Also, it's a sheer scale factor. The larger/more powerful the engine, the less water injection seems to be worth. The most powerful engine I know of that can use water injection only gets a 3% boost in power for most variants. It was primarily used in the 50's and 60's when any increase in thrust was worth it. And the Harrier certainly needs it, as it has such a tiny payload etc---as the thrust increase is about equal to a Harrier's typical bombload.

Water injection adds power, in multiple ways. The exact method is tweaked for each engine.

[Retracting Head Ter Ter]

So how does the black smoke factor in? What causes it? Always been curious about those B-52 pics where they smoke from all 8 jets on takeoff.

Edited November 7, 2006 by Retracting Head Ter Ter

[David Hingtgen]

If it's simply "smokey", it's just a B-52 with old engines. If it looks like there's 8 coal-burning locomotives under the wings, then it's using water injection.

Convair 880's are a good reference for how bad "old smokey jets" can be WITHOUT water injection:

http://www.airliners.net/open.file/0004414/M/

http://www.airliners.net/open.file/0004413/M/

The Convair 990 was a bit cleaner:

http://www.airliners.net/open.file/0138424/M/

For water injection, the extra-black smoke is simply because the water prevents complete combustion of the fuel, same as any old car or truck spewing out black exhaust. For other jet engines, same problem, just not as bad.

[Retracting Head Ter Ter]

I don't even recall pics of Me-262s being so smokey.

Got a link to a pic of a B-52 or other plane smoking under water injection?

Since water-injection results in small power gains but I assume those massive amounts of unburnt fuel represent fuel consumption hikes, isn't it better to just have reheat on the engines?

[David Hingtgen]

The incomplete(wasted) fuel is far, far less than an afterburner would impose. Full afterburner can easily triple fuel burn. The black smoke is caused by "imperfectly" burnt fuel--it was still burnt and providing energy, just not as ecologically-friendly as normal, and wasting a bit of it.

Afterburners add a lot of weight and complexity--mainly the nozzle. You're hauling around that extra weight and paying to maintain it constantly. Water injection weighs almost nothing when it's not being used, and requires little maintenance. Basically--water injection is a simple way to occasionally get a little boost. Afterburners are a complex way to frequently get a big boost.

I posted this pic earlier in the thread, it's a 707 using water injection: http://www.airliners.net/open.file/0541868/M/

[Retracting Head Ter Ter]

I understand but water does take up weight too. And afterburners get you up to 50% more compared with the <10% you mentioned for water-injection. Could you save weight by having _small_ afterburners if you are looking for just 5-10% thrust increase?

To extract something like 3-10% more power using water-injection from say a 15000 lb class engine. How many litres of water per second are we looking at?

Did they ever make an afterburning water-injection combo? Or is that an engineering dumb move?

[sketchley]

I think he already answered the question on afterburners - it's an all or nothing affair.

I can't give any numbers on the second question, but given that jet engines suck in many, many litres of air per second, water consumption is fast. I don't have any figures, but what comes to mind is that the Harrier, with whatever engine it has, and whatever water load it carries, can only use water for anywhere between 1.5 and 5 minutes - basically used for take-off and landing only only. In a way it's like the Concord, using afterburners to get to cruising speed, or something like that (late, tired, no idea if this is coming across clearly.)