Why was'nt the idea of making the legs separate from the engines of a Variable Fighter not further developed after the YF-21/VF-22?

[cheemingwan1234]

Okay, the YF-21 introduced a lot of technologies, many of which such as the BDI/BDS had to be toned down or in the case of it's composite material wing, abandoned....but the idea of   the legs being separate from the engines was an idea that was'nt pursued further after the YF-21/VF-22. Why is it so?

Especially since it makes it more resilient to damage that way since in more traditional VFs (such as the VF-19) , take out the legs and you can screw over the pilot a lot. As seen with the YF-21 against the Ghost X-9, it was still able to fly and fight (and it was helped by Guld disabling the safety systems of his VF to keep up with the Ghost at the cost of his life)  when it's limbs were shot off thanks to the legs being independent of it's engines

Surely the additional durability of keeping the legs separate from the engines that the YF-21 pioneered would be something worth developing for future Variable Fighters? 

Edited November 5, 2023 by cheemingwan1234

[Knight26]

Not really.  The legs being separate makes sense for a battroid or gerwalk-roid, but not a full VF.  In fighter mode a significant portion of the internal volume would be taken up by dead weight.  In a normal VF, only the arms might be considered dead weight in fighter mode, but they usually have some form of weapons integrated into them, or weapon mounts.  Having two legs tucked into the fuselage also limits the amount of fuel and weapons it could carry since they do not have any other purpose outside of battroid mode.

[pengbuzz]

3 hours ago, cheemingwan1234 said:

Okay, the YF-21 introduced a lot of technologies, many of which such as the BDI/BDS had to be toned down or in the case of it's composite material wing, abandoned....but the idea of   the legs being separate from the engines was an idea that was'nt pursued further after the YF-21/VF-22. Why is it so?

Especially since it makes it more resilient to damage that way since in more traditional VFs (such as the VF-19) , take out the legs and you can screw over the pilot a lot. As seen with the YF-21 against the Ghost X-9, it was still able to fly and fight (and it was helped by Guld disabling the safety systems of his VF to keep up with the Ghost at the cost of his life)  when it's limbs were shot off thanks to the legs being independent of it's engines

Surely the additional durability of keeping the legs separate from the engines that the YF-21 pioneered would be something worth developing for future Variable Fighters? 

We're talking about savailable airframe space, which is always going to be at a premium in aircraft. The YF-21's setup was different. as General Galaxy 's design encases the arms and legs for stealth purposes (within the main fuselage), and they were probably going for a larger airframe design anyways. But keep in mind that any sort of modification or redesign such as dedicated limbs comes with tradeoffs such as added mass (which means fuel consumption for the extra weight), extra wiring/ servos to hand;e that setup, added armor for the limbs (protection from enemy fire), and separate power conduits to the engines and limbs (instead of a main bus that splits when it gets to those parts in the engine nacelles/ legs).

As far as "resilient to damage", that only works insofar as not damaging the limbs and the engines at the same time. The YF-21's engines were on its' back, meaning you could still take them out with directed weapons fire at that part. That would still "screw over the pilot" regardless of where your mech's limbs are located.

In most VF's, you're simply not going to have the luxury of having separated limbs/ engines/ et al; they have to go somewhere and that's going to have costs. UN Spacy/ NUNS kept going with the current paradigm because frankly, having engines in the legs means you don't have to have separate nacelles for them and the required mechanics/ electronics/ software for it.

@Seto Kaiba This is pretty much my take on it, but  I'm certain with your experience and access to the various Macross publications that you'd have an official (and far more concise) explanation than mine. I'd really like your input on this if you get a chance.

[Seto Kaiba]

7 hours ago, cheemingwan1234 said:

Okay, the YF-21 introduced a lot of technologies, many of which such as the BDI/BDS had to be toned down or in the case of it's composite material wing, abandoned....but the idea of   the legs being separate from the engines was an idea that was'nt pursued further after the YF-21/VF-22. Why is it so?

An explicit explanation isn't given in any of the technical materials that I've seen.

Of course, we can make some reasonable assumptions based on what we know about why the YF-21/VF-22 ended up designed the way it was and what concessions had to be made in its design to compensate for those unconventional decisions.

Variable Fighter Master File and Macross Chronicle both lean into the idea that the YF-21's unconventional transformation was a product of two things: the design's basis in the Queadluun-Rau battle suit and the design team's goal of maximizing passive stealth performance.  Macross Chronicle's coverage of the YF-21's GERWALK mode makes a brief note about how most VFs mount their engines in the (lower) legs because it makes for a more efficient transformation.  (This probably helps stability a fair bit too, putting the heaviest single part of the Battroid closest to the ground.) 

The YF-21's unconventional design required some additional considerations to preserve GERWALK mode operation.  Most VFs use the main engines to produce thrust for lift and vector that thrust to maneuver while supplementing that vectoring with a sub-engine for forward thrust.  The YF-21's unconventional design meant that General Galaxy had to get weird with it.  The legs are basically deadweight in GERWALK mode, containing only verniers.  The main engines have to produce both forward thrust AND lift thrust, so how they went about it was to essentially install a set of large slats in the underside of the engine compartment so that bypass airflow from the engines could be redirected downward to produce lift while the main engines produced thrust for forward motion.  This is probably rather hard on the engines (which Master File alleges already suffer from a significantly reduced operating lifespan due to being overtuned to compensate for the YF-21's greater mass and energy requirements) and the extent to which that thrust can be vectored to maximize maneuverability is far more limited.

Master File also notes that putting the engines in the main body instead of the legs makes them more difficult to service... which is more of a problem for the YF-21/VF-22 than many other VFs since as noted above its overtuned engines need more TLC from the mechanics than those of other VFs.

The loss of maneuverability from being less able to vector main engine thrust was presumably compensated for by the Inertia Vector Control System.  That's probably a double-edged sword on its own, since that system is extremely expensive and difficult to produce.

 

7 hours ago, cheemingwan1234 said:

Especially since it makes it more resilient to damage that way since in more traditional VFs (such as the VF-19) , take out the legs and you can screw over the pilot a lot. As seen with the YF-21 against the Ghost X-9, it was still able to fly and fight (and it was helped by Guld disabling the safety systems of his VF to keep up with the Ghost at the cost of his life)  when it's limbs were shot off thanks to the legs being independent of it's engines

Surely the additional durability of keeping the legs separate from the engines that the YF-21 pioneered would be something worth developing for future Variable Fighters? 

The ability to purge the limbs and keep flying is a very niche and not particularly useful feature.

Mind you, it doesn't make the VF itself more resistant to damage... it just means that hits to the limbs are less disabling than hits to center mass, while the opposite would be true for other VFs.  Even then, if other VFs had the same energy generation improvements applied to their engines and were willing to make the same design compromises to get that greater output, they'd still be better off since they'd have far more energy to throw at energy conversion armor and pinpoint barrier systems at the expensive of engine lifespan.

What you might gain in terms of stealtiness and tolerance for a lost limb you lose in terms of ease of maintenance, a larger airframe, and greater burden on the active stealth system.

[cheemingwan1234]

9 hours ago, Seto Kaiba said:

An explicit explanation isn't given in any of the technical materials that I've seen.

Of course, we can make some reasonable assumptions based on what we know about why the YF-21/VF-22 ended up designed the way it was and what concessions had to be made in its design to compensate for those unconventional decisions.

Variable Fighter Master File and Macross Chronicle both lean into the idea that the YF-21's unconventional transformation was a product of two things: the design's basis in the Queadluun-Rau battle suit and the design team's goal of maximizing passive stealth performance.  Macross Chronicle's coverage of the YF-21's GERWALK mode makes a brief note about how most VFs mount their engines in the (lower) legs because it makes for a more efficient transformation.  (This probably helps stability a fair bit too, putting the heaviest single part of the Battroid closest to the ground.) 

The YF-21's unconventional design required some additional considerations to preserve GERWALK mode operation.  Most VFs use the main engines to produce thrust for lift and vector that thrust to maneuver while supplementing that vectoring with a sub-engine for forward thrust.  The YF-21's unconventional design meant that General Galaxy had to get weird with it.  The legs are basically deadweight in GERWALK mode, containing only verniers.  The main engines have to produce both forward thrust AND lift thrust, so how they went about it was to essentially install a set of large slats in the underside of the engine compartment so that bypass airflow from the engines could be redirected downward to produce lift while the main engines produced thrust for forward motion.  This is probably rather hard on the engines (which Master File alleges already suffer from a significantly reduced operating lifespan due to being overtuned to compensate for the YF-21's greater mass and energy requirements) and the extent to which that thrust can be vectored to maximize maneuverability is far more limited.

Master File also notes that putting the engines in the main body instead of the legs makes them more difficult to service... which is more of a problem for the YF-21/VF-22 than many other VFs since as noted above its overtuned engines need more TLC from the mechanics than those of other VFs.

The loss of maneuverability from being less able to vector main engine thrust was presumably compensated for by the Inertia Vector Control System.  That's probably a double-edged sword on its own, since that system is extremely expensive and difficult to produce.

 

The ability to purge the limbs and keep flying is a very niche and not particularly useful feature.

Mind you, it doesn't make the VF itself more resistant to damage... it just means that hits to the limbs are less disabling than hits to center mass, while the opposite would be true for other VFs.  Even then, if other VFs had the same energy generation improvements applied to their engines and were willing to make the same design compromises to get that greater output, they'd still be better off since they'd have far more energy to throw at energy conversion armor and pinpoint barrier systems at the expensive of engine lifespan.

What you might gain in terms of stealtiness and tolerance for a lost limb you lose in terms of ease of maintenance, a larger airframe, and greater burden on the active stealth system.

So, yeah, the YF-21/VF-22 is gonna to have some balance abnormalities when walking compared to a more 'traditional' VF.

 

Point noted, still wonder if the tech could be pursued further since this would be good for combat. Bust the limbs of a VF and this could screw with how it transforms. 

[Seto Kaiba]

59 minutes ago, cheemingwan1234 said:

Point noted, still wonder if the tech could be pursued further since this would be good for combat. Bust the limbs of a VF and this could screw with how it transforms. 

Further development based on the YF-21/VF-22 seems to have been based entirely upon improving the brainwave control system. The one late model that we see that was being used as an experimental test bed (VF-22HG Schwalbe Zwei) was being used to develop improvements to the BCS that eventually evolved into the cybernetic version of the system seen on the YF-27 and VF-27.

Development of VF defensive measures seems to have focused far more on making sure that the limbs stay on rather than trying to work around losing a limb. The focus being on improvements to structural materials, energy conversion armor, and pinpoint barrier systems to make the limbs more resistant to damage.

[cheemingwan1234]

37 minutes ago, Seto Kaiba said:

Further development based on the YF-21/VF-22 seems to have been based entirely upon improving the brainwave control system. The one late model that we see that was being used as an experimental test bed (VF-22HG Schwalbe Zwei) was being used to develop improvements to the BCS that eventually evolved into the cybernetic version of the system seen on the YF-27 and VF-27.

Development of VF defensive measures seems to have focused far more on making sure that the limbs stay on rather than trying to work around losing a limb. The focus being on improvements to structural materials, energy conversion armor, and pinpoint barrier systems to make the limbs more resistant to damage.

Well, that's one way to ensure that limbs don't get blown  off.

[azrael]

1 hour ago, cheemingwan1234 said:

still wonder if the tech could be pursued further since this would be good for combat. Bust the limbs of a VF and this could screw with how it transforms. 

Considering a VF's primary weapons are either located or used by the limbs, having detaching limbs adds no benefit if your only only way to use your armaments is blown off/rendered ineffective. Standard doctrine always calls for aiming for center mass since it's the biggest target and has the greatest chance of making sure your opponent doesn't stay combat effective. Aiming for limbs or headshots are acts of luck and chance. If I hit a wing or something, that's nice but I'm still aiming for the main fuselage of the aircraft since that's where the engines, avionics, etc. are.  Oh you're talking about battroid mode? Might as well paint a target on the main body since that's where the pilot is and happens to be the biggest target of a Battroid VF.

[Big s]

21 hours ago, cheemingwan1234 said:

Okay, the YF-21 introduced a lot of technologies, many of which such as the BDI/BDS had to be toned down or in the case of it's composite material wing, abandoned....but the idea of   the legs being separate from the engines was an idea that was'nt pursued further after the YF-21/VF-22. Why is it so?

Especially since it makes it more resilient to damage that way since in more traditional VFs (such as the VF-19) , take out the legs and you can screw over the pilot a lot. As seen with the YF-21 against the Ghost X-9, it was still able to fly and fight (and it was helped by Guld disabling the safety systems of his VF to keep up with the Ghost at the cost of his life)  when it's limbs were shot off thanks to the legs being independent of it's engines

Surely the additional durability of keeping the legs separate from the engines that the YF-21 pioneered would be something worth developing for future Variable Fighters? 

I think the in world reasons have been explained above.

As far as those like Kawamori designing these for an anime, it probably comes down to the fact that jets coming from the feet look cool. If the plane brings down the legs for gerwalk, it looks cool. And as far as battroid doing a quick boost to get out of the way of a missile barrage, it looks cool to change direction based on how the leg and feet movements almost as if jumping away

[sketchley]

22 hours ago, cheemingwan1234 said:

Surely the additional durability of keeping the legs separate from the engines that the YF-21 pioneered would be something worth developing for future Variable Fighters?

Would just like to point out that the YF-21 was neither the first, nor was the VF-22 the last to have engines not in the legs:

 

VA-3 Invader and its derivatives:

• http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VA-3/VA-3.php
• VA-3C Kai Invader: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VA-3/VA-3CKai.php
• VA-3M Invader: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VA-3/VA-3M.php
• EVA-3 Invader: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VA-3/EVA-3.php

Variable Gurāji and its derivatives:

• http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VariableGuraaji/VariableGuraaji.php
• VBP-1/VA-100 Neo-Gurāji Bis [Kai]: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VariableGuraaji/VBP-1neoGurajiBis.php
• VBP-1/VA-100 Neo-Gurāji: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VariableGuraaji/VBP-1neoGuraji.php

VAB-2 and its derivatives:

• VAB-2 speculative appearance: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VAB2/vab-2.php
• FBz-99 Zaubāgeran: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VarohtaFighters/FBz99.php

Pheyos Valkyrie (Enemy Valkyrie):

• http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/Pheyos/pheyos.php

VB-6 König Monster:

• http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VB-6/VB-6.php

Variable Police vehicles:

• Variable Police Air Patrol Craft: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VariablePolice/VariablePoliceAir.php
• Variable Police Space Patrol Craft: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VariablePolice/VariablePoliceSpace.php
• Variable Police Ground Patrol Craft: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VariablePolice/VariablePoliceGround.php

 

and the more esoteric OCTOS Variable Amphibious Destroid:

• http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/Octos/Octos.php

 

 

I haven't listed them chronologically, but the YF-21 comes after the development of the VA-3 Invader, Variable Gurāji, etc, and the VF-22 predates the development of the Pheyos Valkyrie, VBP-1/VA-100 Neo-Gurāji Bis [Kai], etc.

[Big s]

30 minutes ago, sketchley said:

Would just like to point out that the YF-21 was neither the first, nor was the VF-22 the last to have engines not in the legs:

 

VA-3 Invader and its derivatives:

• http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VA-3/VA-3.php
• VA-3C Kai Invader: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VA-3/VA-3CKai.php
• VA-3M Invader: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VA-3/VA-3M.php
• EVA-3 Invader: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VA-3/EVA-3.php

Variable Gurāji and its derivatives:

• http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VariableGuraaji/VariableGuraaji.php
• VBP-1/VA-100 Neo-Gurāji Bis [Kai]: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VariableGuraaji/VBP-1neoGurajiBis.php
• VBP-1/VA-100 Neo-Gurāji: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VariableGuraaji/VBP-1neoGuraji.php

VAB-2 and its derivatives:

• VAB-2 speculative appearance: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VAB2/vab-2.php
• FBz-99 Zaubāgeran: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VarohtaFighters/FBz99.php

Pheyos Valkyrie (Enemy Valkyrie):

• http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/Pheyos/pheyos.php

VB-6 König Monster:

• http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VB-6/VB-6.php

Variable Police vehicles:

• Variable Police Air Patrol Craft: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VariablePolice/VariablePoliceAir.php
• Variable Police Space Patrol Craft: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VariablePolice/VariablePoliceSpace.php
• Variable Police Ground Patrol Craft: http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/VariablePolice/VariablePoliceGround.php

 

and the more esoteric OCTOS Variable Amphibious Destroid:

• http://sdfyodogawa.mywebcommunity.org/Stats/Statistics/Octos/Octos.php

 

 

I haven't listed them chronologically, but the YF-21 comes after the development of the VA-3 Invader, Variable Gurāji, etc, and the VF-22 predates the development of the Pheyos Valkyrie, VBP-1/VA-100 Neo-Gurāji Bis [Kai], etc.

A few of those examples have engines in the legs. The variable monster and Gurajii both have them, but they aren’t main engines like in most Valkyrie models. I’m not as familiar with the other designs since they were kinda in the oddball category 

[pengbuzz]

5 hours ago, cheemingwan1234 said:

Point noted, still wonder if the tech could be pursued further since this would be good for combat. Bust the limbs of a VF and this could screw with how it transforms. 

Here's a novel concept: make sure the pilot is skilled enough and trained enough to not "get limbs blown off" the Valkyrie.

You do realize that in the middle of a dogfight, by the time you're done trying to just blow off the legs, the opposing pilot's already trashed your main body on your valk? It's not like they're just going to do like "The Fish Slap Dance" and stand there while you open fire:

Limbs and other parts are considerably small, in light of targeting the main body as a whole. The damage incurred on the limbs of the YF-21 was due to the large numbers of missiles and the incoming fire from the AI controlled Ghost X-9.  If you're facing that kind of craft, you've got problems no matter what you do.

3 hours ago, azrael said:

Considering a VF's primary weapons are either located or used by the limbs, having detaching limbs adds no benefit if your only only way to use your armaments is blown off/rendered ineffective. Standard doctrine always calls for aiming for center mass since it's the biggest target and has the greatest chance of making sure your opponent doesn't stay combat effective. Aiming for limbs or headshots are acts of luck and chance. If I hit a wing or something, that's nice but I'm still aiming for the main fuselage of the aircraft since that's where the engines, avionics, etc. are.  Oh you're talking about battroid mode? Might as well paint a target on the main body since that's where the pilot is and happens to be the biggest target of a Battroid VF.

Right? You blow one limb off, the pilot and mech are still in the fight; you blow up the main body and it isn't going to matter how many limbs are left.

Not to mention the other pilot's probably going to guess after the first second or two what you're trying to do and do something about it (like target YOUR main body and light you p like a Christmas Tree).

Edited November 6, 2023 by pengbuzz

[sketchley]

4 hours ago, Big s said:

A few of those examples have engines in the legs. The variable monster and Gurajii both have them, but they aren’t main engines like in most Valkyrie models. I’m not as familiar with the other designs since they were kinda in the oddball category 

The YF-21/VF-22 has sub-engines in the legs, too.

I'll submit that the VB-6 is unique as its sub-engines are "normal" engines (aka thermonuclear reaction engines), however every VF that doesn't have "normal" engines in the legs has rocket motors or vernier-like engines in the legs (like the YF-21/VF-22 does).

[cheemingwan1234]

3 hours ago, pengbuzz said:

Here's a novel concept: make sure the pilot is skilled enough and trained enough to not "get limbs blown off" the Valkyrie.

You do realize that in the middle of a dogfight, by the time you're done trying to just blow off the legs, the opposing pilot's already trashed your main body on your valk? It's not like they're just going to do like "The Fish Slap Dance" and stand there while you open fire:

Limbs and other parts are considerably small, in light of targeting the main body as a whole. The damage incurred on the limbs of the YF-21 was due to the large numbers of missiles and the incoming fire from the AI controlled Ghost X-9.  If you're facing that kind of craft, you've got problems no matter what you do.

Right? You blow one limb off, the pilot and mech are still in the fight; you blow up the main body and it isn't going to matter how many limbs are left.

Not to mention the other pilot's probably going to guess after the first second or two what you're trying to do and do something about it (like target YOUR main body and light you p like a Christmas Tree).

Unless you're one of those Windermereans with an overgrown sense of chivarly.

[Seto Kaiba]

12 hours ago, azrael said:

Aiming for limbs or headshots are acts of luck and chance.

To a point, yeah... though there is one notable exception.

Missiles using infrared guidance - the most common primary guidance system on micromissiles - are going to overwhelmingly target a Valkyrie's engines no matter where they're situated in the airframe because that's the part of a Valkyrie that emits the most heat.  For most Valkyries, this means they'll home in on the legs.

 

 

[Devil 505]

The way I see it, having another set of thrusters in the legs while being separate from the main engines could make for some Harrier-style VIFFing (Vectoring In Forward Flight).

[Seto Kaiba]

1 hour ago, Devil 505 said:

The way I see it, having another set of thrusters in the legs while being separate from the main engines could make for some Harrier-style VIFFing (Vectoring In Forward Flight).

VFs have thrusters all over the place independent of the engines in the legs... around two dozen of 'em, in most cases.  The vernier thrusters used for attitude control in space and, in some cases, in atmosphere.

The low-thrust verniers used for most maneuvers don't have huge output on their own, but when you can throw a dozen of them at the problem it adds up.  The high-thrust verniers used for braking and roll control on the VF-1 Valkyrie can put out up to 24.5kN apiece, around a quarter the total engine output of the Harrier (105kN).  They're not fixed nozzles either, they can ALL thrust vector.

Edited December 28, 2023 by Seto Kaiba

[azrael]

1 hour ago, Devil 505 said:

The way I see it, having another set of thrusters in the legs while being separate from the main engines could make for some Harrier-style VIFFing (Vectoring In Forward Flight).

Unfortunately, that only works for the Harrier since the exhaust nozzles are closer to the middle of the aircraft. Deploying the legs like that is akin to changing to GERWALK-mode mid-maneuver. And when dealing with another VF-type aircraft, the effect negated since the other aircraft could pull the same tactic (essentially hitting the brakes, and they fly past you).

[pengbuzz]

3 hours ago, Devil 505 said:

The way I see it, having another set of thrusters in the legs while being separate from the main engines could make for some Harrier-style VIFFing (Vectoring In Forward Flight).

One issue is going to be your fuel budget. In atmosphere, it's not that bad for a VF, but in space, propellant and fuel is at a premium. In Macross Delta, Arad had to remind Hayate to watch his propellant levels" during one sortie, as after a couple of maneuvers, you could be out of propellant or even low on fuel.

Additionally: the more thrusters and engines you put into a mech, the more weight and mass that will be added by said dry mass, but the more fuel you will have to carry. While the fuel issue is (one again) not so bad for a VF in atmosphere, the systems still take up space in the airframe. 

In space...  that mass costs big.

On top of that: added thrusters/ engines and such are going to add to the overall cost in time, money and materials in the form of maintenance. If those systems cannot be maintained at a reasonable level, then all they are doing is taking up mass and room on an airframe that needs every ounce working towards its' performance.

One thing many folks forget when it comes to airframe design: it becomes a series of tradeoffs, where you have to decide what the goal of the craft is and what matters most. This is why in Macross, you don't see too many "just like a Gundam" type craft; there are costs and supplies are used up, as is endurance. Not to mention that what seems like a good idea on paper often doesn't work in the real world.

One reason there aren't rocket launchers that fire chainsaws...

[JB0]

42 minutes ago, pengbuzz said:

One reason there aren't rocket launchers that fire chainsaws...

... is because people lack VISION.

[sketchley]

2 hours ago, JB0 said:

... is because people lack VISION.

Did someone say chainsaws on a VF?

https://www.deviantart.com/studiootaking/art/VT-1CS-Silviculture-Valkyrie-Lineart-605492693

[JB0]

8 hours ago, sketchley said:

Did someone say chainsaws on a VF?

https://www.deviantart.com/studiootaking/art/VT-1CS-Silviculture-Valkyrie-Lineart-605492693

It... it's beautiful.

[Big s]

10 hours ago, sketchley said:

Did someone say chainsaws on a VF?

https://www.deviantart.com/studiootaking/art/VT-1CS-Silviculture-Valkyrie-Lineart-605492693

It’s funny that the chainsaws are actually in the missile launchers. 
VF-1FU Trees!!!!

[Seto Kaiba]

16 hours ago, pengbuzz said:

One issue is going to be your fuel budget. In atmosphere, it's not that bad for a VF, but in space, propellant and fuel is at a premium. In Macross Delta, Arad had to remind Hayate to watch his propellant levels" during one sortie, as after a couple of maneuvers, you could be out of propellant or even low on fuel.

Additionally: the more thrusters and engines you put into a mech, the more weight and mass that will be added by said dry mass, but the more fuel you will have to carry. While the fuel issue is (one again) not so bad for a VF in atmosphere, the systems still take up space in the airframe. 

In all fairness, the mass per unit of volume of hydrogen slush is not exactly huge... 0.085 kilograms per liter (about 0.71 pounds per gallon), a bit more than 1/10th what the same volume of JP-5 weighs (0.81kg/L or 6.76lb/gal).

The full internally-carried fuel load of a VF-1 weighs only about 1.5x what the pilot does.  (1,410L @ 0.085kg/L is 119.85kg or 264lb.)  

Weight isn't the problem for a VF,  it's more a matter of consumption rate and available internal tank capacity.

 

16 hours ago, pengbuzz said:

On top of that: added thrusters/ engines and such are going to add to the overall cost in time, money and materials in the form of maintenance. If those systems cannot be maintained at a reasonable level, then all they are doing is taking up mass and room on an airframe that needs every ounce working towards its' performance.

The other beautiful thing is that the supplemental thrusters for maneuvering are pretty darned simple.  The thrust vectoring nozzle aside, it's basically just a channel for propellant and either an electrically-driven laser diode or just an electrical arc across the propellant stream to flash-heat it.  Simple, lightweight, and effective.

[pengbuzz]

5 hours ago, Seto Kaiba said:

In all fairness, the mass per unit of volume of hydrogen slush is not exactly huge... 0.085 kilograms per liter (about 0.71 pounds per gallon), a bit more than 1/10th what the same volume of JP-5 weighs (0.81kg/L or 6.76lb/gal).

The full internally-carried fuel load of a VF-1 weighs only about 1.5x what the pilot does.  (1,410L @ 0.085kg/L is 119.85kg or 264lb.)  

Weight isn't the problem for a VF,  it's more a matter of consumption rate and available internal tank capacity.

 

The other beautiful thing is that the supplemental thrusters for maneuvering are pretty darned simple.  The thrust vectoring nozzle aside, it's basically just a channel for propellant and either an electrically-driven laser diode or just an electrical arc across the propellant stream to flash-heat it.  Simple, lightweight, and effective.

...and.... I'm out of ideas here.

19 hours ago, sketchley said:

Did someone say chainsaws on a VF?

https://www.deviantart.com/studiootaking/art/VT-1CS-Silviculture-Valkyrie-Lineart-605492693

*retires to faraway planet and takes up origami*

[Devil 505]

11 hours ago, Seto Kaiba said:

In all fairness, the mass per unit of volume of hydrogen slush is not exactly huge... 0.085 kilograms per liter (about 0.71 pounds per gallon), a bit more than 1/10th what the same volume of JP-5 weighs (0.81kg/L or 6.76lb/gal).

The full internally-carried fuel load of a VF-1 weighs only about 1.5x what the pilot does.  (1,410L @ 0.085kg/L is 119.85kg or 264lb.)  

Weight isn't the problem for a VF,  it's more a matter of consumption rate and available internal tank capacity.

I apologize for bringing up Robotech, but I seem to recall the use of metallic hydrogen in recent versions of their RPG instead of slush hydrogen.

[Seto Kaiba]

5 hours ago, Devil 505 said:

I apologize for bringing up Robotech, but I seem to recall the use of metallic hydrogen in recent versions of their RPG instead of slush hydrogen.

Your recollection is accurate.  The circumstances behind that are somewhat involved and off topic, so I'll answer by way of spoiler tag.  I was actually able to discuss that with the very people who made that decision back in the mid-2000s, so I've got firsthand knowledge as to the why.

It was indirectly inspired by the Macross setting's use of thermonuclear fusion as the default power source for any kind of giant robot though...

Spoiler

Long story short, after Harmony Gold brought in Tommy Yune to replace Carl Macek as creative director following the failure of Robotech 3000, he set out to create an official setting and canon for Robotech as part of a brand-wide effort to rehabilitate the franchise's image and reinvent it as a respectable sci-fi anime property.  Part of that effort to create an official canon meant official stats for the mecha based on the animation source material.  He outsourced that work to a fan group who did a pretty poor job overall but got most of the details right or right-ish for the mecha in Macross and MOSPEADA.  

This created a problem.  By numbers and any rational analysis, the performance of the Macross VF-1 Valkyrie was far superior to that of the MOSPEADA AFC-01 Legioss (the "Alpha fighter").  This led to fans not-unreasonably pointing out that it doesn't make any sense to replace the VF-1 with the Legioss and TLEAD (Alpha and Beta) since it can do everything both of those aircraft can do, and do it better.  The complaints about this eventually got loud enough that Tommy Yune resolved to do something.  Around the time Palladium Books was going to print with the core book for their Robotech: the Shadow Chronicles role-playing game, Tommy decided the best explanation that wouldn't involve tweaking the stats was to establish that the mecha from before Robotech's New Generation ran on fusion power instead.  This made the Alpha more advanced than the VF-1, even though its performance was lower.  It was hoped that this would appease fans.  Harmony Gold didn't go any farther than just saying "fusion powered".  It was Palladium Books who, after receiving this information, decided that the fuel needed to be something "exotic" and "more sci-fi" in order to make it distinctive.  They settled on "stabilized liquid metallic hydrogen", albeit without any knowledge of or interest in what the actual properties of metallic hydrogen are.  It sounded cool so they went with it, and when it landed on Tommy's desk for editorial review he saw no reason to say "No" so it went to print.  

This nominally solved the original problem, by having the RPG state that the VF-1's fusion powerplant had a much shorter runtime than the Alpha's "protoculture" one... but it left the VF-1 a far superior combat aircraft and it introduced a new problem.  Namely, the VF-1 and other Macross mecha were now game-breakers in Robotech's later eras... the lack of a "protoculture" power system meant they were invisible to the Invid.

You can make hydrogen slush in industrial quantities with 1960's technology.  Metallic hydrogen is something we're still struggling to reproduce at all even in the tiniest of experimental quantities, because it only exists in nature under enormous pressures like the atmospheres of gas giants.  It's something NASA is very interested in as a rocket fuel, because it's just very very compressed hydrogen that'll let you pack an order of magnitude more fuel into the same space and it'll burn more energetically.  Stabilized, it would hold its density at STP, making it extremely storage-friendly rocket fuel... if it weren't Made of Explodium to a cartoonish extent in the presence of any kind of oxidizer.

 

[Areoborg]

Wouldn't a metallic hydrogen be more like a solid rocket fuel, rather than a liquid fuel (or mostly liquid with the hydrogen slush)?  Its not like you can close the valve or anything like that, unless you're going to rely solely on the presence of an oxidizer to turn it off an on when using it in space.

[Seto Kaiba]

1 hour ago, Areoborg said:

Wouldn't a metallic hydrogen be more like a solid rocket fuel, rather than a liquid fuel (or mostly liquid with the hydrogen slush)?  Its not like you can close the valve or anything like that, unless you're going to rely solely on the presence of an oxidizer to turn it off an on when using it in space.

"Metallic" hydrogen refers to a phase of hydrogen where it gains the electrical conductivity of a metal.  It doesn't necessarily imply a particular state.

The elemental properties of hydrogen and the pressures necessary to achieve metallicity in it (over 3.9 million atmospheres) suggest that naturally-occurring metallic hydrogen will exist as a liquid in the middle and lower atmospheres of gas giant planets.  Theories regarding the possibility of metastability in metallic hydrogen (the ability for it to stay metallic after being removed from the high pressure environment) suggest a metastable or stable metallic hydrogen would be a supersolid... a sort of liquid crystal with the zero viscosity of superfluids.  It'd work like liquid rocket fuel, assuming the real thing meets the properties physicists say it should.  (Of course, if you're storing your fuel under 4 million atmospheres or more of compression, just releasing that pressure would be enough to get some pretty impressive propulsion... never mind burning the stuff.)

As I noted, the RPG writers in question picked it purely because it sounded "Sci-Fi" without any familiarity with the material's hypothetical properties.

 

Macross, as noted previously, uses a real world material: hydrogen slush.  It's mercifully quite light so even thousands of liters doesn't add a significant amount of mass to the VF and it can pull triple duty as both fuel for the compact thermonuclear reactor, the laser and arcjet thermal rockets used for verniers, and as a system coolant for the engines in space.  The rocket motors in Macross are a mixed bunch, but the ones used as boosters for VFs and so on are often hybrid rocket systems with a solid fuel putty and liquid oxidizer.  The VF-25's Super Pack boosters are described as using a weird inert fuel gel that contains both fuel and oxidizer in suspension that evaporates under high voltage for combustion.

[JB0]

11 hours ago, Areoborg said:

Wouldn't a metallic hydrogen be more like a solid rocket fuel, rather than a liquid fuel (or mostly liquid with the hydrogen slush)?  Its not like you can close the valve or anything like that, unless you're going to rely solely on the presence of an oxidizer to turn it off an on when using it in space.

Metallic hydrogen's a liquid, much like metallic mercury.