For Questions That Don't Merit Their Own Thread

[Terwin]

I thought that the propeller was in the nose for those early planes, making that unavailable for the cockpit

Also, at least on top you have the body of the plane for ablative skid armor for landings where the gear is insufficient.  (Also makes ditching from a water landing easier)

[magnemoe]

42 minutes ago, Terwin said:

I thought that the propeller was in the nose for those early planes, making that unavailable for the cockpit

Also, at least on top you have the body of the plane for ablative skid armor for landings where the gear is insufficient.  (Also makes ditching from a water landing easier)

This is true for single engine planes but not for multi engine ones except a few with front and rear propellers. 
For WW 1 and related bombers It was an position needed for the one aiming the bombs. Later bombers became large enough so the pilot could sit above him. 
Might also be inertia you sit on top and some distance back in all single engine planes who is the first you fly so it was not seen as important I guess. 

[darthgently]

2 hours ago, DDE said:

The question was inspired by pre-WW2 bombers, where this wasn't an issue, and extensive nose glazing for the navigator and gunners was present.

Ah, so pre radar domes in the nose.  I might be partially right.

[AckSed]

They don't have to be on the main body at all: https://en.wikipedia.org/wiki/Blohm_%26_Voss_BV_141

Spoiler

https://commons.wikimedia.org/wiki/File:Bundesarchiv_Bild_183-2005-0725-526,_Aufklärungsflugzeug_Blohm_-_Voß_BV_141.jpg#/media/File:Bundesarchiv_Bild_183-2005-0725-526,_Aufklärungsflugzeug_Blohm_-_Voß_BV_141.jpg

Yes, this flew.

Edited January 31 by AckSed

[magnemoe]

19 minutes ago, AckSed said:

They don't have to be on the main body at all: https://en.wikipedia.org/wiki/Blohm_%26_Voss_BV_141

  Hide contents

https://commons.wikimedia.org/wiki/File:Bundesarchiv_Bild_183-2005-0725-526,_Aufklärungsflugzeug_Blohm_-_Voß_BV_141.jpg#/media/File:Bundesarchiv_Bild_183-2005-0725-526,_Aufklärungsflugzeug_Blohm_-_Voß_BV_141.jpg

Yes, this flew.

I say this is an good idea, kind of an stealth plane but not low visibility but rather that enemies don't believe their eyes and if fail wish very much they not seen it. 

[ARS]

On 1/31/2024 at 7:00 PM, DDE said:

Dumb question: given that takeoff and landing are the most hazardous regimes, why were aircraft cockpits stubbornly placed on top instead of in the nose?

The landing area is in constant view of the pilot throughout the entire descent to landing. Aircraft descend in a nose down pitch attitude. During the landing itself, the pilot is looking down the runway instead of at it, before the aircraft is pitched nose up just before the touchdown. Any other time during the flight, it is much more important to see what is ahead and above you than it is to see what’s below you (at an appropriate altitude). Where seeing under the fuselage would be useful in some situation, it does not give any significant benefit for the pilot to worth the hassle

WW2 era bombers need glass nose for both navigator and gunner. Bombing in WW2 was highly dependent upon visual references due to the lack of GPS guidance. For navigators, bombers need to find navigation references during the run up to what the USAAF termed the “initial point” or the start of the bomb run proper. As anyone who has looked for a ground reference from the air knows, just finding the initial point alone could be challenging. The high visibility offered by the large glass nose was necessary - even if the navigation was accurate (even more so during night bombing). For nose gunners, when defending against head-on pass the gunners could only shoot back during very brief interval when the target is in range. This is both terrifying and difficult, hence why the extensive view of the nose turret is important to spot the enemy planes earlier before they come in range. Once radar technology and GPS for navigation has improved, and defense turrets no longer relevant in modern era, the glass nose becomes obsolete, replaced by much more capable radar and avionics instead of mk1 eyeball

Think of it like driving a car. Like an airplane, your car on the highway is moving forward at a great rate of speed. Having a view of what is below the car would allow you to see the pothole you are running over as you are running over it. That view is not very useful compare to the ability to see the pothole well down the road before you ever reach it. That is why cars don’t need transparent floors. Any speed above a fast walk would render it useless

Edited February 2 by ARS

[kerbiloid]

On 1/31/2024 at 3:00 PM, DDE said:

Dumb question: given that takeoff and landing are the most hazardous regimes, why were aircraft cockpits stubbornly placed on top instead of in the nose?

1. Because the pilots are afraid of altitude, so from the top they don't see the ground far below.

2. Because the planes were overturning onto the nose more often than falling upside down.

3. Because they were biplanes, so the pilot was sitting between the wings and thinking, that he is hidden in the home ("чур, я в домике!").

4. Because the pilot has enough hand work to make the motor keep working, when it had stopped in flight (by rotating magneto or pouring oil).

[JoeSchmuckatelli]

On 1/31/2024 at 12:04 PM, DDE said:

The question was inspired by pre-WW2 bombers, where this wasn't an issue, and extensive nose glazing for the navigator and gunners was present.

@darthgently offers a good reason.  I'm also guessing it's a human-scale issue; making a comfortable cockpit in a plane that also has to accommodate other systems is the most likely reason.  Tradition may also play a factor.

When I read the original question, my first mental image was the F4-U Corsair

which was apparently a pain to land and taxi given it's top placed and way back cockpit - due to the engine and propeller.  The bombers you mentioned had wing mounted engines.

Putting a powerful radar behind the pilot likely isn't good for retention.  Side mounting/wing mounting likely has drag issues.

So it's probably the sum-total of benefits and trade-offs to gain maximum efficiency / performance

Edited February 2 by JoeSchmuckatelli

[AckSed]

My limited search-fu wants to find the results of research conducted on Skylab, specifically the M553 sphere-forming and M555 GaAs semiconductor crystal growth experiments run in the M512 Materials Processing Facility. I'd also like to see the results from the M518 Multipurpose Electric Furnace System. Lots of stuff that could and should be dug out again in this up-and-coming era of heavy lift.

I found the '73 guidebook detailing what was going up, which let me narrow down the names, but nothing afterwards. Does anyone have leads?

[ARS]

What do you guys think about designing a robot with human-like arm so it could hold weapons? In many sci-fi works, whether it's cyberpunk, futuristic or post-apocalyptic setting, we often see robotic combatants, from small humanoid-sized ones holding infantry-grade firearms (ex: B1 battle droid (Star Wars)) to gigantic ones using upscaled arsenal (ex: Titans (Titanfall)). Compared to simply just forget about human hands and have the weapon being the arm itself (ex: Mechwarrior). On one hand, human-like hands allows the machine to do what human hands could, except in larger scale, offers versatility by allowing it to use different types of weapons and can be used to do more mundane tasks (lifting a person, getting up when knocked over, etc.). On the other hand, a weapon arm is much more simple to build, can get bigger guns and generally easier to maintain

Or maybe a middle ground by having a hybrid arm-weapon (lEx: some of Mechwarrior mechs or Gipsy Danger (Pacific Rim))

[SunlitZelkova]

2 hours ago, ARS said:

What do you guys think about designing a robot with human-like arm so it could hold weapons? In many sci-fi works, whether it's cyberpunk, futuristic or post-apocalyptic setting, we often see robotic combatants, from small humanoid-sized ones holding infantry-grade firearms (ex: B1 battle droid (Star Wars)) to gigantic ones using upscaled arsenal (ex: Titans (Titanfall)). Compared to simply just forget about human hands and have the weapon being the arm itself (ex: Mechwarrior). On one hand, human-like hands allows the machine to do what human hands could, except in larger scale, offers versatility by allowing it to use different types of weapons and can be used to do more mundane tasks (lifting a person, getting up when knocked over, etc.). On the other hand, a weapon arm is much more simple to build, can get bigger guns and generally easier to maintain

Or maybe a middle ground by having a hybrid arm-weapon (lEx: some of Mechwarrior mechs or Gipsy Danger (Pacific Rim))

I say both, with the constraint being economics. For example, some B2 Super Battle Droids had rocket launcher arms instead of the standard dual hand/blaster, of course at the cost of an arm. So you build a few droids with that arm like the CIS did, and then larger numbers of “handed” droids that are multipurpose, allowing the streamlining of production. More designs and more parts cost more $$$, so it would be better to have one droid for piloting capital ships, standard infantry, tanks (AATs), security, low level commanders, and so on. They even had a firefighting role onboard the Malevolence. Sounds economic and useful to me, and in Legends/EU apparently Sidious actually had to hold back battle droid production because the CIS could have won if they hadn’t been handicapped by him.

As for what would be best for a big mech? A big mech would operate like a tank instead of infantry, so it would probably be better to have a weapon arm.

[magnemoe]

6 hours ago, ARS said:

What do you guys think about designing a robot with human-like arm so it could hold weapons? In many sci-fi works, whether it's cyberpunk, futuristic or post-apocalyptic setting, we often see robotic combatants, from small humanoid-sized ones holding infantry-grade firearms (ex: B1 battle droid (Star Wars)) to gigantic ones using upscaled arsenal (ex: Titans (Titanfall)). Compared to simply just forget about human hands and have the weapon being the arm itself (ex: Mechwarrior). On one hand, human-like hands allows the machine to do what human hands could, except in larger scale, offers versatility by allowing it to use different types of weapons and can be used to do more mundane tasks (lifting a person, getting up when knocked over, etc.). On the other hand, a weapon arm is much more simple to build, can get bigger guns and generally easier to maintain

Or maybe a middle ground by having a hybrid arm-weapon (lEx: some of Mechwarrior mechs or Gipsy Danger (Pacific Rim))

I say if primary purpose is combat turrets is an better idea, but if you are jury-rigging something or want the option to arm an robot it makes sense to modify an gun so they can use it. 

[darthgently]

I think giant mechs should have hundreds of human sized arms or tentacles with hands springing from around the edges of its feet so that as the mech walks the hands can pick up dropped rifles, magazines, RPGs, etc and use them against the fleeing enemy.   Remember, you read it here first.  This will appear in a SF book now that I've posed it online.

[TheSaint]

I think the only case in which making the robots use human weapons would be if they are going to fight alongside actual human troops. In which case having hands would work better, since then the weapons and all of the associated logistics would be interchangeable. Otherwise I would build the weapons into the robots themselves. That would make it much easier to design the robots to aim, handle recoil, protect the weapon against the elements, etc. If you want to be able to change weapons for different mission profiles, make the weapons modular.

7 hours ago, darthgently said:

I think giant mechs should have hundreds of human sized arms or tentacles with hands springing from around the edges of its feet so that as the mech walks the hands can pick up dropped rifles, magazines, RPGs, etc and use them against the fleeing enemy.   Remember, you read it here first.  This will appear in a SF book now that I've posed it online.

Matrix did it.

Honestly, I think that IRL this would not be a great idea. Dropped weapons on the battlefield are nowhere near as convenient as you imagine them to be. If you're doing it right, they tend to be far away from you, in holes, behind walls, in buildings or vehicles, and they may or may not have a decent supply of ammunition with them, or even be in working condition (explosives tend to be pretty hard on equipment too). Designing your robot specifically to use dropped weapons would probably be a waste of payload mass and money that would be better spent just putting more installed weapons on it in the first place.

[DDE]

On 2/9/2024 at 9:29 AM, ARS said:

On one hand, human-like hands allows the machine to do what human hands could, except in larger scale, offers versatility by allowing it to use different types of weapons and can be used to do more mundane tasks (lifting a person, getting up when knocked over, etc.). On the other hand, a weapon arm is much more simple to build, can get bigger guns and generally easier to maintain

It's really a question of what you expect the robot to do. Earliest UGVs already taking tentative steps would likely be simple mobile gun turrets, i.e. minitanks. Unmanned logictics mules, including complete improvisations, are already a thing.

https://t.me/Artillery_Artillery/18830

And generally there's a strong expectation for specialization, and advantages to be reaped from it. So I expect even later robotic infantry and quasi-infantry to use gun arms and be supported by auxiliaries (engineers, casualty haulers, gun crewmen) with wrist guns.

[kerbiloid]

On 2/9/2024 at 9:29 AM, ARS said:

What do you guys think about designing a robot with human-like arm so it could hold weapons?

 

Spoiler

 

 

 

 

 

Edited February 11 by kerbiloid

[ARS]

18 hours ago, kerbiloid said:

 

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That's kinda neat actually

[SunlitZelkova]

So in the television series For All Mankind, it’s said that the accident at Three Mile Island was prevented with nuclear reactor technology developed for the 1970s NASA lunar base.

Could that have been possible? Is there something that would have prevented Three Mile Island that would have been built (earlier, I presume, and that such technology exists IRL after the accident) for a lunar base’s nuclear reactor?

Calling @RCgothic and anyone else with nuclear industry experience.

[TheSaint]

5 hours ago, SunlitZelkova said:

So in the television series For All Mankind, it’s said that the accident at Three Mile Island was prevented with nuclear reactor technology developed for the 1970s NASA lunar base.

Could that have been possible? Is there something that would have prevented Three Mile Island that would have been built (earlier, I presume, and that such technology exists IRL after the accident) for a lunar base’s nuclear reactor?

Calling @RCgothic and anyone else with nuclear industry experience.

Short answer: Not really, no.

Long answer: TMI2 was, at its core, an accident caused by operator error. Yes, it was exacerbated by some poor design choices. But even with the plant as it was designed, if the operators had been properly trained, if they had not been ignoring the relief valve leakage, if they had quickly recognized and responded to the loss of coolant accident, then the accident would never have happened. Manual position indicators on the primary relief valves would have made that easier for them, but that wasn't impossible technology, that was just a design choice. I can't think of a shiny new technology that can prevent operator error, aside from robotic operators.

Screenwriter's answer: If they're going to say, "We invented a new technology that prevented Three Mile Island from happening," it's an anachronism, which is crappy writing in that sort of genre. Because if Three Mile Island never happened, then nobody is going around saying, "We prevented Three Mile Island from happening." Because it never happened. There have been lots of "almost" nuclear accidents. You've never heard of any of them. They aren't household words. If we suddenly woke up in a world where a certain German dictator had instead gone to art school, then going around bragging about how you had stopped him with a time machine would be pointless. Because you would be the only person who would remember who he had been.

[DDE]

7 hours ago, SunlitZelkova said:

So in the television series For All Mankind, it’s said that the accident at Three Mile Island was prevented with nuclear reactor technology developed for the 1970s NASA lunar base.

Could that have been possible? Is there something that would have prevented Three Mile Island that would have been built (earlier, I presume, and that such technology exists IRL after the accident) for a lunar base’s nuclear reactor?

You may be overthinking it.

It's possible the showrunners think TMI and other production nuclear plants are directly used for nuclear reactor development.

[RCgothic]

There was nothing actually wrong with the TMI reactor itself.

It was mainly a failure of procedures and instrumentation.

How the accident began:

For a start the reactor should never have been at power with both the auxiliary feed water pump stop valves for the secondary loop locked off. The control room operators didn't even notice because the indicators were covered (in one case possibly by an overly fat belly!). This was a major breach of the operating license. The reactor should not have been operating.

Then an improvised filter-cleaning procedure caused water to get into an instrument line and spuriously turn off the main feedwater pumps leading to a turbine trip.

When the turbines are tripped, they no longer remove heat from the secondary loop, causing the temp and pressure in the secondary loop to rise. This is usually corrected by dumping steam and back-filling with feedwater. Except all the main and aux secondary loop feedwater pumps are all effectively inoperable and the operators don't know. In fact they can see the aux pumps running, but don't know they're doing nothing due to their stop valves being closed.

So the secondary loop is getting hotter and depressurised by steam dumping without replacement. The operators don't understand the situation.

The primary circuit is affected by the secondary loop, as the amount of heat that can be removed in the steam generators is greatly reduced.

A brief aside on pressure control in the primary circuit:

There's a pressuriser in the primary coolant loop that contains a steam bubble. Pressure can be increased by turning on heaters in the steam bubble to increase its pressure. Pressure can be also reduced by spraying cold water into the steam bubble to reduce its temperature, or by a solenoid operated pressure relief valve. The level of water in the pressuriser can simultaneously be adjusted by adding or removing water to the primary loop. Generally in the absence of coolant addition/subtraction an increasing pressuriser water level indicates increasing primary loop temperature (and due to expansion compressing the steam bubble - pressure).

Back to the accident:

So with heat not being removed from the primary loop, the primary loop gets hotter, and the coolant expands. It pushes into the pressuriser, compressing the steam and increasing the primary loop pressure. This is when the pressure relief valve is commanded open and sticks open. But it's not enough to keep the pressure down with the reactor at full power, so the reactor is tripped and the control rods inserted, reducing reactor power to ~6% resulting from decay heat which is still substantial.

But the pressuriser level continues to rise even as the primary loop pressure is falling. The operators haven't been trained for these parameters disagreeing. The pressure is falling due to the steam bubble getting vented through the stuck valve, and the level is rising due to the decreased pressuriser bubble and another steam bubble forming invisibly to the operators in the reactor pressure vessel (due to boiling in the low pressure) then displacing coolant into the pressuriser. There is basically already a minor loss of coolant accident in progress, but the operators take far too long to work this out.

It's exacerbated by bad instrumentation - the control panel doesn't show the valve's actual position, what it reports as valve position is just the solenoid power status, and as the valve is stuck this is incorrect. There was a temperature sensor downstream from the pressure relief valve that could have helped indicate coolant was passing the valve, but as it was not considered safety critical its display was located on a panel that the operators weren't  likely to notice in the heat of crisis.

Pressuriser level rising uncontrollably is normally bad - if the steam bubble disappears the primary loop effectively "goes solid", and therefore could be subject to large pressure excursions as the "incompressible" coolant fights its pressure vessel. The operators have been trained never to allow this as it can cause a loss of coolant accident. So they turn off the primary coolant feed to try and lower the pressuriser level. This is *exactly* the wrong thing to do during an actual loss of coolant accident! It stops the falling coolant level in the RPV getting topped up, and stops cold coolant being introduced to keep the temperature down.

By the time the operators work out their mistake enough coolant has boiled off that the fuel has overheated and melted.

How to fix the TMI reactor design:

Better operator training. Interlocks to prevent reactor operation with safety critical systems locked off for maintenance. Better control panel layouts. Revised, more reliable pressure relief valve. Safety critical valves to have indicator switches to report their actual position, not merely their solenoid power status.

The actual reactor design was a good and safe design. Despite the accident and radiation release there's no direct evidence of harm to anybody off-site.

Reactors for lunar bases:

The main challenge for reactors in space is heat rejection. Earth-based thermal power plants (not just nuclear) generally need to reject heat to the environment, and the best way of doing that is by releasing steam or using bodies of water as heat sinks. Neither of those is especially possible in space, and radiators are very much less effective at heat dissipation so they'd need a lot.

Water for the primary coolant loop is also very heavy, which could be prohibitive.

Perhaps a space-based reactor would be better off using a high temperature gas-cooled or liquid-metal cooled design rather than a conventional PWR using water and steam cycles. Gas is a lighter coolant than water, and liquid metal would allow a denser, more compact and therefore potentially less massive reactor as a result, and both could have higher temperature exhausts which would make their radiators more effective.

It could also be better to use much higher military/weapons grade fuel enrichments as the mass of fuel to be transported would be a lot lower, and again they'd have higher power densities allowing smaller less massive reactors as well.

I'm speculating a bit though. Presumably there are some NASA papers somewhere with some concrete plans, my experience is of AGR and PWR reactors.

Edited February 14 by RCgothic

[SunlitZelkova]

5 hours ago, RCgothic said:

[snip]

Thanks. This was a great response!

[ARS]

So... There's something that makes me curious. During WW2, armor piercing bombs are in widespread use (whether it's actual bomb purpose built for that or AP shell repurposed into a bomb), mainly for attacking hardened targets like capital ships or hardened bunkers. Now, since the bomb is designed to penetrate the target before exploding inside, the bomb relied on kinetic energy from terminal velocity after it's being dropped to achieve penetration. Since terminal velocity is the highest velocity attained by a falling object, assuming the bomb is dropped from the height sufficient enough to achieve maximum terminal velocity purely by falling, does that means bombing from higher altitude than that does no increase in penetration capability? (since the terminal velocity remains the same)

[TheSaint]

1 hour ago, ARS said:

So... There's something that makes me curious. During WW2, armor piercing bombs are in widespread use (whether it's actual bomb purpose built for that or AP shell repurposed into a bomb), mainly for attacking hardened targets like capital ships or hardened bunkers. Now, since the bomb is designed to penetrate the target before exploding inside, the bomb relied on kinetic energy from terminal velocity after it's being dropped to achieve penetration. Since terminal velocity is the highest velocity attained by a falling object, assuming the bomb is dropped from the height sufficient enough to achieve maximum terminal velocity purely by falling, does that means bombing from higher altitude than that does no increase in penetration capability? (since the terminal velocity remains the same)

Well, I don't really have the time to calculate terminal velocities, but remember that terminal velocity varies based on the density and geometry of the object that is falling. A streamlined AP bomb made of steel and TNT has a much higher terminal velocity than, say, a feather, or a human being. So in order to reach that terminal velocity the bomb would have to be dropped from a very high altitude in order to allow gravity to accelerate it for the required amount of time.

During WWII, bombs were aimed by optical sights, or (in the case of high altitude bombing) by electro-mechanical aiming computers such as the Norden bomb sight. These were not sophisticated aiming devices by today's standards. In high-altitude bombing their CEPs were hundreds of yards. So, in general, dropping your precision AP bomb from extremely high altitudes wasn't really an option. This is why most naval bombers during the era were dive bombers: they were much more accurate, and used a power dive of the aircraft to accelerate the bomb towards the target to increase its penetrating power.  So, precision bombing during WWII was much more limited by the ability of the bomber to hit its target than it was by the penetrating power of the bomb itself. If someone would have suggested dropping a bomb on a battleship from 20,000 feet to increase its penetrating power, the counterargument would have been, "Yes, but we'll never hit the damn thing."

[JoeSchmuckatelli]

3 hours ago, ARS said:

oes that means bombing from higher altitude than that does no increase in penetration capability?

Pretty much.

Gravity bombs do have some kinetic penetration ability - but the main weapon is the chemical energy charge inside.  What changes is how the fuse works; a point detonating fuse doesn't exactly go off at the moment of impact - but it's close enough. 

Hit something hard and you get very little penetration before the chemical explosive is triggered and most of the explosion is at or near the surface.  Put a delayed fuse on there and you allow the kinetic property of the bomb to (hopefully) penetrate the surface before detonating - and you get the damage inside the target (presuming a hit).  This is with simple HE.

There are a myriad of ways to design bombs and shells.  The big, air dropped ones like MOAB or MOP are going to use their weight differently.  MOAB gives you a LOT of chemical energy.  MOP gives you a LOT of penetration.  Simple gravity bomb design is going to take into account the type of effect desired and change things like the fuse timing, material of the body/nose, etc.

You can compare with tank ammo; the SABOT is pure KE where the other variations of HE, HEDP, HEAT (etc. ad nauseum) are all designed in varying ways to mix the KE and CE properties of the round to one degree or another.  With the first - speed is necessary.  With the latter?  Depends.

One difference vis altitude is the hyperkinetic weapons under development - where they're going for extreme streamlining to maximize KE.  There are a lot of ways to get the weapon up high and moving fast.

But for the simple / improved gravity bomb?  Weight, material, streamlining, etc all go into the 'what do you want to do' answer.