For Questions That Don't Merit Their Own Thread

[Hyperspace Industries]

Why does nobody use solar thermal propulsion (not to be confused with solar sails)?:

Some of our best designs for nuclear thermal rockets release 1 kilowatt of power per kilogram of reactor.

On the earth's surface we get around 1 kilowatt of solar energy per square meter. A square meter of reflective material to concentrate that energy into heating fuel would probably weigh less than a kilogram. If you used a thin foil like sheet, you could probably easily get it below a 100 grams. This could easily get the thrust and efficiency of at least a reasonable radioisotope thermal rocket.

[Gargamel]

3 minutes ago, Hyperspace Industries said:

On the earth's surface we get around 1 kilowatt of solar energy per square meter. A square meter of reflective material to concentrate that energy into heating fuel would probably weigh less than a kilogram. If you used a thin foil like sheet, you could probably easily get it below a 100 grams. This could easily get the thrust and efficiency of at least a reasonable radioisotope thermal rocket.

I'll point you to the Mythbusters Deathray episode where they used mirrors to burn a ship.  They had a huge problem trying to get the mirrors to align perfectly to concentrate enough energy to do anything.   I would suspect your ultralight material would be no more stable a mirror as the school children they were using.     To get the effect you are looking for, you are requiring focal points of pinpoint precision.  The reflective material wouldn't be the mass of the ship, the massively rigid superstructure behind it would be the problem.  

[JoeSchmuckatelli]

It only takes one... 

Some of what I enjoy reading is 'rise of civilization' and 'early human' research.  You will often find reference to our domestication of various animals at guessed at times, but rarely do you get explication of how that happens.  How early humans who were dangerous hunters managed to capture and keep calm their 'save for later' food. 

From this (unrelated) article - I'd hazard the safe guess that we were helped by dogs. 

https://www.huffpost.com/entry/dog-raised-cheetah-cubs-coby-dies_n_61d9c356e4b0bcd2195fd7d5

(Article mourns the death of a famous zoo dog that helped infant animals to be less instinctively nervous around people.) 

[kerbiloid]

38 minutes ago, JoeSchmuckatelli said:

How early humans who were dangerous hunters managed to capture and keep calm their 'save for later' food. 

Comparing the muscle mass of a mature dog and of a puppy or a kitten, I would strong;y doubt they were ever treated as a backup food.

Also there is no much sense in keeping them for days because they need meat themselves to survive these days.

Let alone the reputation of a hunter who would eat kittens instead of the serious men's food.

Imho, it looks more probably that they were being taken from the lair just because, and brought to the village as expendable toys for the children's sadistic games.

So, the more funny and attractively a beastling was looking, the higher were the chances that some elderman's mini-daughter kept the toy for further playing, providing it with food and using the dad's authority to protect the little jerk from the citizens' righteous revenge for stolen meat or liquided boots.

That's  why the domesticated cats & dogs are neotenic version of their wild prototypes.

[JoeSchmuckatelli]

6 minutes ago, kerbiloid said:

a puppy or a kitten, I would strong;y doubt they were ever treated as a backup food

Grin - agreed.  Besides, predators taste bad.  Leaf eaters taste good. 

 

7 minutes ago, kerbiloid said:

funny and attractively a beastling was looking, the higher were the chances that some elderman's mini-daughter kept the toy for further playing

Absolutely - keeping the children entertained and exercised is a great thing for the scavenger to do. 

 

None of which was my point, however.  When we set out to domesticate the cow and sheep and goat and horse and etc. we likely had to kill most males and obnoxiously dangerous females and then teach the babies to not freak out and get all the other hoofed meat angry-scared and kicking down the enclosure.  So using the dog (which likely domesticated itself) to calm down the baby food and show that it's OK to be calm around people probably sped up the process. 

[kerbiloid]

16 minutes ago, JoeSchmuckatelli said:

So using the dog (which likely domesticated itself)

The dogs have rudimentary brow muscles which absent on adult wolves, and another constrcution of the neck, they are childish version of the wolves or other wolf-like predators.

So, this shows that they have evolved neotenically from those wolf specimens who was keeping childish anatomical features (actually, were having low male hormones causing both aggression and anatomical adulting), i.e. from those puppies who were low-aggressive and looking puppish even getting grown.

Another feature is that big dog suffer and die younger from metabolism illnesses than small dogs.
This demonstrates that the originally domesticated dog was small and wasn't used for biting, mostly for tracing and scaring the hidden prey.

So, it was either some tiny wolf species, or undergrown ones.

[Hyperspace Industries]

In a Kessler syndrome situation, could you get to orbit by going into a sub orbital trajectory which puts your apoapsis into the debris field, and then (since most of our satellites orbit the same direction), accelerate to orbital speed by having all the debris crash into a big shield on the back of your ship?

How big of a shield would you need?

[SOXBLOX]

6 hours ago, Hyperspace Industries said:

Why does nobody use solar thermal propulsion (not to be confused with solar sails)?:

Some of our best designs for nuclear thermal rockets release 1 kilowatt of power per kilogram of reactor.

On the earth's surface we get around 1 kilowatt of solar energy per square meter. A square meter of reflective material to concentrate that energy into heating fuel would probably weigh less than a kilogram. If you used a thin foil like sheet, you could probably easily get it below a 100 grams. This could easily get the thrust and efficiency of at least a reasonable radioisotope thermal rocket.

Atomic Rockets calls this kind of engine a "Solar Moth". It would have a NTR-like efficiency, and it could be fairly low-mass. One proposal on the AR page is to aluminize the interior hemisphere of a transparent balloon. (Instant reflector dish.) It looks like it would work great. You'd want to use hydrogen, though, and you have to find a way to store it for long journeys. I think that's the main issue.

[magnemoe]

2 hours ago, Hyperspace Industries said:

In a Kessler syndrome situation, could you get to orbit by going into a sub orbital trajectory which puts your apoapsis into the debris field, and then (since most of our satellites orbit the same direction), accelerate to orbital speed by having all the debris crash into a big shield on the back of your ship?

How big of a shield would you need?

The rear hold your engine who is not the thing you want anything to crash into. I would rater pass trough the field fast and circularize above, you could watch out for large parts and have an shield of thin plates spaced out to handle tiny stuff. 
Now I don't think Kessler syndrome is realistic unless specific obits GEO is vulnerable here. Say some did an GTO burn then messed up the deorbit burn and raised Pe to 1000 km instead and then the upper stage blew up because of over pressure. 
Large scale war in orbit is an issue but that would be the least concern or all is happy it did not turned into an nuclear war. 

[magnemoe]

5 hours ago, kerbiloid said:

Comparing the muscle mass of a mature dog and of a puppy or a kitten, I would strong;y doubt they were ever treated as a backup food.

Also there is no much sense in keeping them for days because they need meat themselves to survive these days.

Let alone the reputation of a hunter who would eat kittens instead of the serious men's food.

Imho, it looks more probably that they were being taken from the lair just because, and brought to the village as expendable toys for the children's sadistic games.

So, the more funny and attractively a beastling was looking, the higher were the chances that some elderman's mini-daughter kept the toy for further playing, providing it with food and using the dad's authority to protect the little jerk from the citizens' righteous revenge for stolen meat or liquided boots.

That's  why the domesticated cats & dogs are neotenic version of their wild prototypes.

Agree, now sledge dogs are know to be an backup food source. 
Amundsen in his race for the south pole did deliberately used staging as in he planned to kill off some of his dogs as they was no longer needed because dry mass had dropped and used them to feed the rest of the dogs, now he probably learned this strategy from the Inuits who he lived close to for years but they saw this as an escape system who could get the crew back to the family.
Not that the Inuits did not had their evil genius ideas. Take an rib bone sharpen both ends very sharp, cook then bend like an spring, tie ends together, put it into an cup of seal fat outdoor, cut the string and use this to bait polar bears. Not as brave as fighting them with an stone tipped spear but much more less dangerous.  

[JoeSchmuckatelli]

On 1/9/2022 at 1:39 PM, Hyperspace Industries said:

In a Kessler syndrome situation, could you get to orbit by going into a sub orbital trajectory which puts your apoapsis into the debris field, and then (since most of our satellites orbit the same direction), accelerate to orbital speed by having all the debris crash into a big shield on the back of your ship?

How big of a shield would you need?

Okay - I'm the furthest from 'a math guy' you are likely to find here - but I'm guessing you are contemplating a 'fly straight up, turn 90 degrees' thing?   

Newton probably handles this - and if you have one great big ship with a honking Viking Beard of a shield at the back... Just how much force you need to move it should be simple to work out... But I don't think we even need to. 

Problem is that the debris is tiny.  So let's analogize - how many BBs do need to shoot at a garbage truck rolling uncontrolled down hill towards your house to push it out of your yard?  Answer is 'lots'.  You need lots of BBs.  You also have a time problem.  Because you are in a race against gravity.  So you need lots of BBs hitting the truck in a short period of time.  (You also have a 'space' problem (because space is big) - so you need lots of BBs all hitting the truck in a short time and they all need to be concentrated in time and space to save your house.  You can start to guess at the weight needed, because if you have a whole bunch of BBs hitting all at the same time, rather than calculate each individual F=MA for thousands of BBs you can pretty much just smoosh all the BBs together and figure out what F=MA you get for one giant BB... But we don't like math, so we can keep analogizing.  So how big is that smooshed BB? 

Okay - shifting analogies a bit - you ever try to move a bowling ball with a cue ball?  Cue to 7 gets the 7 moving right quick, but Cue to bowling?  Man, if you chuck it hard it can shift the bowling ball and if you have a bucket of cue balls and a good arm you can get it moving.  So clearly we don't need a garbage truck sized BB. 

Now I'm guessing that a bucket of cue balls weighs more than a bowling ball an... 

... 

... 

Huh. 

 

Now I realize why people do math. 

Edited January 11, 2022 by JoeSchmuckatelli

[wumpus]

On 1/9/2022 at 10:33 AM, kerbiloid said:

Comparing the muscle mass of a mature dog and of a puppy or a kitten, I would strong;y doubt they were ever treated as a backup food.

Also there is no much sense in keeping them for days because they need meat themselves to survive these days.

Let alone the reputation of a hunter who would eat kittens instead of the serious men's food.

Imho, it looks more probably that they were being taken from the lair just because, and brought to the village as expendable toys for the children's sadistic games.

So, the more funny and attractively a beastling was looking, the higher were the chances that some elderman's mini-daughter kept the toy for further playing, providing it with food and using the dad's authority to protect the little jerk from the citizens' righteous revenge for stolen meat or liquided boots.

That's  why the domesticated cats & dogs are neotenic version of their wild prototypes.

The "just so stories" I've heard about such things imply that cats "domesticated themselves" by hunting vermin in granaries.  Those that could tolerate humans in closer proximity were the ancestors of domestic cats.  When the early farmers realized that the cats killed things that ate the grain (and not the grain), they suddenly liked that cats a lot more (although the ancient Egyptians took it to extremes.  Perhaps they had more vermin to manage?).

On 1/9/2022 at 10:47 AM, JoeSchmuckatelli said:

Grin - agreed.  Besides, predators taste bad.  Leaf eaters taste good. 

Certainly not true in fish.  I've also read anthropologists and others who ate lion insist that it is rather good.

On 1/9/2022 at 10:33 AM, kerbiloid said:

Let alone the reputation of a hunter who would eat kittens instead of the serious men's food.

While this is a serious consideration for any hunter society, you can expect boys (and old men, and sometimes women and children if the men aren't bringing enough "big game") to hunt the little stuff (and could therefore get away with "hunting" cats and dogs).  And they often bring back more total calories than their "mighty hunter" fathers.

[kerbiloid]

43 minutes ago, wumpus said:

The "just so stories" I've heard about such things imply that cats "domesticated themselves" by hunting vermin in granaries.  Those that could tolerate humans in closer proximity were the ancestors of domestic cats. 

+1
Who didn't - became wiskas for the cats who did.

Kitties are such kitties...

***

45 minutes ago, wumpus said:

On 1/9/2022 at 6:47 PM, JoeSchmuckatelli said:

Grin - agreed.  Besides, predators taste bad.  Leaf eaters taste good. 

Certainly not true in fish.  I've also read anthropologists and others who ate lion insist that it is rather good.

Bear is a traditionally delicious food in the forests of the Russian Plain.

Also this adds the intrigue: who is hunting whom.

[JoeSchmuckatelli]

1 minute ago, kerbiloid said:

Bear is a traditionally delicious food

Brown bear is like a pig - eats everything, mostly plants.  Pure carnivore is nasty.

[kerbiloid]

9 hours ago, JoeSchmuckatelli said:

Brown bear is like a pig - eats everything, mostly plants.  Pure carnivore is nasty.

The dogs aren't - from the words of the familiars who ate it.

Also they are a part of traditional Far-Eastern cuisine.

[ARS]

Why the probabiity of AWACS aircraft being shot down in large-scale air conflict is very rare? Do they fly too high to be targeted or spend the majority of their time very far from action, just using their radar and supporting the allied aircraft?

[K^2]

45 minutes ago, ARS said:

Why the probabiity of AWACS aircraft being shot down in large-scale air conflict is very rare? Do they fly too high to be targeted or spend the majority of their time very far from action, just using their radar and supporting the allied aircraft?

I don't know if there are other factors, but they have an enormous range. You would need a fighter, drone, or a cruise missile to cover the distance, which, given the altitude, would make them easy targets for counter-fire. That's my best guess.

[monophonic]

1 hour ago, ARS said:

Why the probabiity of AWACS aircraft being shot down in large-scale air conflict is very rare? Do they fly too high to be targeted or spend the majority of their time very far from action, just using their radar and supporting the allied aircraft?

Firstly, because large-scale air conflict between peers is very rare. Since WW2, only Korea, Falklands, Indo-Pakistani wars, and Iran-Iraq come readily to mind. Of those only Korea had anything like AWACS used in theater. I discount the wars of Israel because while the numbers say "peers" the results are very lopsided. Rest of the candidates either feature only little air warfare or so large imbalance of forces that the AWACS could fly about their mission unthreatened.

Secondly,  because AWACS are a very high value asset so they are protected accordingly. In case it or anybody else detects an incoming enemy that just might be a threat to the AWACS, everything in range will abandon their current mission to protect the AWACS which itself will move to evade the aggressor. Therefore, as to attack an AWACS the enemy needs to commit a very large force against a very large force, a serious attack on an AWACS is barely distinguishable from general offensive counter air warfare.

Russia, and Soviet Union in its time, has developed some very long range air-to-air (and lately surface-to-air) missiles. Those have been dubbed "AWACS killers" in public despite being more important for intercepting bombers over the vast swathes of Siberia. Other nations haven't really bothered, and as the Soviets and Russians haven't fought peers since the Sino-Soviet border conflict theirs haven't shown their true effectiveness either.

Personally, I believe had the cold war gone hot, plenty of AWACS and other C3I planes would have got shot down on both sides in short order.

[JoeSchmuckatelli]

57 minutes ago, monophonic said:

because large-scale air conflict between peers is very rare

This. 

@ARS

AWACS systems don't fly over contested airspace. 

They fly high and see far to help first tier militaries gain and maintain and extend air superiority.  Only (until recently, and because of proliferation) top tier militaries have the ability to penetrate deeply enough into the controlled airspace to threaten AWACS... And thus far top tier nations have been smart enough to not engage one another directly. 

That could change in the next few decades - unless calmer minds prevail 

[ARS]

@monophonic, @JoeSchmuckatelli So what this means is that, they fly outside the conflict zone at high altitude, yet their radar and sensor still  has enough range to reach inside the contested airspace to assist the allied aircrafts?

[JoeSchmuckatelli]

1 hour ago, ARS said:

@monophonic, @JoeSchmuckatelli So what this means is that, they fly outside the conflict zone at high altitude, yet their radar and sensor still  has enough range to reach inside the contested airspace to assist the allied aircrafts?

I'm not totally versed on the tech - but the basics are that the higher you fly, the farther is your local horizon 

https://www.google.com/url?sa=t&source=web&rct=j&url=https://sites.math.washington.edu/~conroy/m120-general/horizon.pdf&ved=2ahUKEwir-sP3_qn1AhXxdc0KHcY-AzIQFnoECAQQBg&usg=AOvVaw1-NEzYvf70gXi57tKustKo

This works for finding how far you can see something on the surface.  Things like mountains or planes can be seen further as they, too are higher. 

Now - whether you bring something into the conflict zone depends on the threat assessment and how well you control the airspace. 

From the Naval warfare aspect - think of AWACS as your unarmed spotting plane - it's job is to spot the enemy far away and give decision makers time to act as well as identifying and coordinating targets.  You create a zone of control around the fleet and your Intel assets - with the tough fast movers setting the perimeter.  If you want to extend power onto the land, you can keep your soft assets over the sea and safe while you are working on gaining air superiority and eliminating surface threats. 

Every slice you take extends how close to shore or how far inland you can go - up to and including free overflight of the entire zone.  (Largely depends on enjoying an asymmetric advantage - but that is AWACS' job, isn't it?) 

[kerbiloid]

They keep away from those who can.

[Jacke]

11 hours ago, ARS said:

Why the probabiity of AWACS aircraft being shot down in large-scale air conflict is very rare? Do they fly too high to be targeted or spend the majority of their time very far from action, just using their radar and supporting the allied aircraft?

There's a mission in the old Tornado game that outlined how hard it is to attack AWACS aircraft, "Take Down the Mainstay", the Soviet AWACS.

It's flown in a Tornado GR kitted out for air-to-air combat with 4 Sidewinders and drop tanks.  You fly a low-level approach using the Tornado's amazing ability to terrain follow until you see the Mainstay on your air-to-air radar.  You then zoom up to the AWACS altitude and go for the shootdown.  After killing it, you dive back down to low altitude and use the Tornado's top low-level high-speed to escape and return to base.

The first time I flew it, took me a few tries to pull off the attack without blowing the zoom or getting shot down.  Was an amazing mission.

[SunlitZelkova]

16 hours ago, ARS said:

Why the probabiity of AWACS aircraft being shot down in large-scale air conflict is very rare? Do they fly too high to be targeted or spend the majority of their time very far from action, just using their radar and supporting the allied aircraft?

It was rare, but may not be anymore. China has developed the PL-15, a very long range air-to-air missile (200-300km range) which is probably intended to shoot down USAF support assets, like tankers and AWACS.

Before the PL-15/AWACS-tanker vulnerability hype began though, the Soviet Union developed the R-37 air-to-air missile, with a max range of 300km. It was delayed by the collapse of the USSR and ensuing economic problems of Russia, but now is entering service.

The United States has a similar weapon called the AIM-260 Joint Advanced Tactical Missile (JATM). "Joint" refers to being used by both the USAF and USN. Its range is actually classified, Wikipedia gives it 200km while another source claims 222km. The entire program is very secret, with a special bunker being built specifically to house the missiles at Hill AFB. It could be used to attack AWACS and tanker aircraft.

The USAF is also developing a missile called the Long-Range Engagement Weapon. Not much is known about it, but it will be even longer ranged than the AIM-260.

Given how North Korea seems to be trying to mimic as many modern weapons as possible (they have revealed some sort of Abrams looking MBT and recently flown hypersonic glide vehicle prototypes), I wouldn't be surprised if they were working on one too. Whether it will actually perform well is another matter, however.

[kerbiloid]

Microprose F-117 had the Mainstay hunting on regular basis.