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On 10/4/2019 at 12:42 AM, Aperture Science said:

Why don't more gliders use the canard configuration, seeing as instead of giving negative lift (conventional tailplane) the canards contribute to it?

Probably because of canard instability in gliders. Most aircraft with canards have engines to propel them and allows recovery from stall condition. On gliders, this is a very serious matter. Most aircraft use a horizontal stabilizer on the tail to maintain stability. Let's take an example of Cessna. With the center of gravity ahead of the wing's center of lift, the aircraft wants to pitch nose-down. However, the horizontal stabilizer on the tail acts as a mini-wing, generating lift downwards (called tail down force) and pitching the nose back up. The canard is essentially moves the horizontal tail up to the nose section, and places the wing's center of lift behind the center of gravity. To balance the natural nose down tendency, the canard generates an upward lifting force - which helps oppose weight.

HOWEVER, If canards were that simple, every aircraft would use them. Aerodynamics are never that simple. Things get complicated in a stall. On a Cessna, if the wing stalls before the tail, you'll still have elevator controllability to pitch down. If the tail stalls before the wing, the aircraft will naturally pitch down. In either case, stall recovery is natural. However, if your aircraft has a canard instead of a tail-mounted horizontal stabilizer, you're in real trouble if the wing stalls first. In this case, the center of gravity would drop the wing and tail, pitching the nose up. The aircraft now enters a deeper stall and becomes unrecoverable, and you're screwed. To solve this, You need to make sure that the wing is always further away from the critical angle of attack than the canard. You can accomplish this by using a larger wing on the aircraft. This ensures that the wing never gets close to it's critical angle of attack before the canard stalls. However, this larger wing adds weight and drag, reducing the design's efficiency.

Canards can also make an airplane unstable. Simply put, if a wind gust briefly increases the angle of attack on a Cessna, the aircraft tends to pitch nose down and return to it's original attitude. In the Cessna's case, the increased angle of attack increases the wing's lift. However, it actually decreases the tail down force, because it decreases the horizontal stabilizer's angle of attack. However, the canard can actually make your aircraft pitch up further. The increase in angle of attack causes both the canard and the wing to generate more lift. If the canard's increase in lift is greater than the wing's, the nose will pitch further up. To solve this problem, designers use high wing loading on the canard. This means that the canard generates more lift per square foot than the wing. At high wing loading, an increase in angle of attack causes a smaller increase in lift than at low wing loading. But here's the downside - high wing loading generates more induced drag. To counter this, designers often use a high aspect ratio canard - which means it's long and narrow. That decreases the drag, but makes a large canard hard to build.

Edited by ARS
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  • 2 weeks later...

Could you have easier access to space on a habitable planet smaller than Earth? From what I know our planet is actually pretty small and has a relatively big core, so with a G-type star it's probably very close to being as small as possible. Any further shrinking would probably result in it being a lava-covered mess (smaller planet with the same sized core = thinner crust?).

What about a system with a K-type star and a smaller than Earth planet with atmosphere dense enough and magnetic field powerful enough to deflect the star's activity (since it's a K-type I'm assuming the activity is minimal)? How much easier can space travel be than it is on Earth?

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The core mass is proportional to the total mass (if the planet composition is same).
So, smaller planet - smaller core.

The same about total amount of water and carbon dioxide to be extracted.

But as the core extraction process would finish significantly faster (less matter to get separated), the planet would be geologically dead much faster too, so an evolution wouldn't have time to result into something edible.

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Could you defeat a tank with anti-material rifle by crippling it by first breaking it's periscope/ observation devices and other sensors, forcing the commander to poke his head out and shoot him? (Assuming the tank is alone in urban area and the sniper knows the surrounding area to flank the tank)

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5 hours ago, ARS said:

Could you defeat a tank with anti-material rifle by crippling it by first breaking it's periscope/ observation devices and other sensors, forcing the commander to poke his head out and shoot him? (Assuming the tank is alone in urban area and the sniper knows the surrounding area to flank the tank)

Yes, but actually breaking these devices on some of the old-school tanks would inherently lead to people looking through them also getting killed.

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5 hours ago, ARS said:

Could you defeat a tank with anti-material rifle by crippling it by first breaking it's periscope/ observation devices and other sensors, forcing the commander to poke his head out and shoot him?

You can defeat it even by shooting at proper place in armor where it has weak places like technological openings or auxilliary devices of the propulsion system.

Edited by kerbiloid
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On 12/7/2014 at 5:52 PM, gooddog15 said:

Could aliens understand what planet Pioneer 10/11 came from due to it's position?

Pioneer_plaque_solar_system.svg

Well this sixth planet is crossed off, so we know its not that one. Also, the antenna is pointing at Earth. What are the gray line/dashes?

------------------------------------------

Best scam ever?

https://www.snopes.com/fact-check/nigerian-astronaut-lost-in-space/

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The aliens will never find us because they will be looking for a system with nine planets and no asteroid belt, while we have the belt and just eight.

***

The picture clearly tells that the probe performed a maneuver next to the crossed planet, heading right to the third one. Probably missed.

***

The gray lines with scratches obviously depict something like a meteor shower orbiting between the two big planets.
The probe was trying to evade it but probably was hit (see this dent on its side?).
This explains why it missed the target.

***

The scratches next to each planet are obviously binary digits.
They are some binary flags.

And as you can see, the bigger is the planet, the more scratches it has.
This obviously means that additional scratches describe some additional parameters of gas planets.

We can see five gas planets, and the fartherst one is extra-small and has a lot of "ones" where others have "zeroes". Except the seventh one, too.
We don't not what does it mean, but probably it is some kind of extra-dense ice giant.

***

The probe glyph direction allows us to find the star which had sent the probe to this planetary system.

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I was watching a video about satellite building when the thought struck me: How cheaply could you feasibly build a satellite?

As the word has many definitions, let's consider a case: A satellite about the size of a washing machine, in low Earth orbit, with no functionality whatsoever except being visible to trackers (and the right type of telescope) and having your name engraved on it. Let's pretend you have a dream and much money to spare, but not that much money. Let's assume the cost of the launch itself is not a problem, but on manufacturing the satellite itself you want to cut as many corners as feasible.

Could you feasibly weld something together in your own garage, be confident enough in your own craftsmanship to know it won't fall apart from the launch forces, hoist it onto your flatbed truck and haul it off to Cape Canaveral? Or would the launch companies refuse to have anything to do with anything that isn't accompanied by a stack of signed documentation from a certified and trusted supplier, included proof of assembly by certified and trusted personnel? And if you have to order your satellite from a manufacturer, how much would they charge you? Assume that your goal is to launch an intact satellite way above cubesat size, but it doesn't have to actually do anything once up there. There's no way for the satellite itself to stop working unless it physically breaks apart, and you're building it sturdy enough to know that it won't. Does it still have to, for instance, pass all those expensive radiation and temperature tests or be handled in clean-room conditions at all times?

Edited by Codraroll
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4 minutes ago, Codraroll said:

I was watching a video about satellite building when the thought struck me: How cheaply could you feasibly build a satellite?

As the word has many definitions, let's consider a case: A satellite about the size of a washing machine, in low Earth orbit, with no functionality whatsoever except being visible to trackers (and the right type of telescope) and having your name engraved on it. Let's pretend you have a dream and much money to spare, but not that much money. Let's assume the cost of the launch itself is not a problem, but on manufacturing the satellite itself you want to cut as many corners as feasible.

Could you feasibly weld something together in your own garage, be confident enough in your own craftsmanship to know it won't fall apart from the launch forces, hoist it onto your flatbed truck and haul it off to Cape Canaveral? Or would the launch companies refuse to have anything to do with anything that isn't accompanied by a stack of signed documentation from a certified and trusted supplier, included proof of assembly by certified and trusted personnel? And if you have to order your satellite from a manufacturer, how much would they charge you? Assume that your goal is to launch an intact satellite way above cubesat size, but it doesn't have to actually do anything once up there. There's no way for the satellite itself to stop working unless it physically breaks apart, and you're building it sturdy enough to know that it won't. Does it still have to, for instance, pass all those expensive radiation and temperature tests or be handled in clean-room conditions at all times?

 

Technically it does not have to, but we are dealing with bureacracy here. They won't NOT let you do anything withouy making you swim through paperwork.

At the same time, if your sat does nothing, they won't send iy up unless you have a wad of cash for them.

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19 hours ago, Spacescifi said:

 

Technically it does not have to, but we are dealing with bureacracy here. They won't NOT let you do anything withouy making you swim through paperwork.

At the same time, if your sat does nothing, they won't send iy up unless you have a wad of cash for them.

In part is that your satellite can damage other payloads. From an fuel tank blowing up to just outgassing in vacuum who can damage optic. 
NASA complained about SpaceX changing the insulation used on the trunk on dragon for this last reason. 
NASA did not see that the outgassing was documented well enough and they was worried about an telescope they would put on the IIS.

Rocketlab is probably easiest to work with here as you get your own rocket but they are more expensive than random cube sat slots. 

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2 hours ago, magnemoe said:

In part is that your satellite can damage other payloads. From an fuel tank blowing up to just outgassing in vacuum who can damage optic. 
NASA complained about SpaceX changing the insulation used on the trunk on dragon for this last reason. 
NASA did not see that the outgassing was documented well enough and they was worried about an telescope they would put on the IIS.

Rocketlab is probably easiest to work with here as you get your own rocket but they are more expensive than random cube sat slots. 

 

Explaining the reasons behind it makes me more accepting of the paperwork. Thanks.

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If I have the capability to launch and land on Mars by my own effort, if I do an unauthorized launch, assuming it's successful and I become the first human that landed on Mars, even if it's from an illegal launch, do I still get credit for "first"? How the world would react? And what they'll do if I do get back to earth?

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I guess, "the world", i.e. other 7 billions living in other countries would not care much about legal status of your flight in your own country.
But on another hand all spies of the world will be trying to know your secret, how to build an interplanetary rocket undetected.
So, probably the rest of your life would not differ if the authorities will be trying to punish you or protect.

So, if you have a Martian interplanetary boat in your barn, keep posting Martian photos in instagram and say that they are real.
Of course nobody will believe it's the Mars, but everyone would be shocked by your photoshop skills.

Edited by kerbiloid
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3 hours ago, kerbiloid said:

Of course nobody will believe it's the Mars

Unless when I'm showing up on NASA's rover camera and my spacecraft is detected on Martian surface

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So, let's say I have two really big airtight rooms, room A and room B. The air in room A is just the same as normal air on Earth, but the air in room B has twice as much oxygen. With that in mind:

 

1. Say I light a fire in each room, and keep both of them flaming with a steady stream of fuel. Will the fire in B require only half as much fuel?

2. Say I throw a hand grenade or a stick of dynamite or a creeper into each room. Will the explosion in B be twice as strong?

3. Same as 1 and 2 except instead of only doubling the oxygen concentration, the air density is doubled for all component gases.

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2 hours ago, ChrisSpace said:

1. Say I light a fire in each room, and keep both of them flaming with a steady stream of fuel. Will the fire in B require only half as much fuel?

My guess, because I'm not 100% on it, is that it will burn the fuel faster. For reference(with a subject I am an expert on), when you add nitrous(40% oxygen vs 20% oxygen air) to a car engine if you do not add more fuel you run your engine lean and melt the combustion chambers and/or pistons because hot oxygen will react with the metal in the engine for fuel. Oxygen is not explosive nor a fuel. As it says on the bottle, it vigorously accelerates combustion. It is reactive.

2 hours ago, ChrisSpace said:

2. Say I throw a hand grenade or a stick of dynamite or a creeper into each room. Will the explosion in B be twice as strong?

Not sure what a creeper is but hand grenades and dynamite have their own oxidizing agent, outside air composition does not matter. But, if there is another fuel source to be scattered and atomized and there is a bunch of O2 present,......well I'll just say fuel air bomb.

2 hours ago, ChrisSpace said:

3. Same as 1 and 2 except instead of only doubling the oxygen concentration, the air density is doubled for all component gases.

Not sure about #1 in this but I'd assume that the fires would be similar. The way the heat convects because of increased density in room B could maybe be different, not sure how that would affect it though or that it would be different at all.

On #2 with the setup of #3 I really don't know. the increase of density in room B could amplify the damage done but the amount of energy released would be the same in both rooms. So, I have no real guess here.

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Okay, well, say I throw a bird into each room, both identical. In room A the bird can carry a total of 1 kilogram and stay airborne (this includes it's own weight). In room B with twice the air density, will the bird be able to carry twice as much since the air is twice as dense, or will it have to fly slower and thus not be able to carry any more weight at all?

 

Take into account that wing-flapping is different from using a jet engine.

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As a bird has a lot of air bubbles inside to make it light, it would be probably thinking about everything but flight, due to the unpleasant feelings and maybe barotrauma.

2 times denser = 2 atm of pressure, so like a diver at 10 m depth.

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What influences the importance of GPU for smooth gameplay in modern games? Is it geometrical complexity of 3D object? the textures? or special effects? Let's take an example of Call of Duty 1, which is a very lightweight game for current generation PCs. On high-end NVIDIA GPU, it's simply overkill to run it, but let's say we take for example Intel HD integrated graphic GPU (still a bit overkill, but insufficient for AAA games expecially newer CoD). If we increase the 3D object complexity (So a pineapple grenade no longer an egg-shaped 3d object, but actually have grooves like actual grenade, tank hulls have rivets, etc.) without improving textures and effects (so the grenade is still just plain dark green object, smoke and explosion effect still the same, no lighting whatsoever), will it still run fine on integrated graphic? Does 3D complexity has minimal or substantial impact on GPU load?

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