Discussion of Military, real or fictional

[mlooney 3,417]

Some details about the balloon.  And why they didn't use auto-cannon on it.

[Darth Fluffy 302]

1 hour ago, mlooney said:

Weather type balloons don't pop as easily as smaller balloons do.  

It didn't have to pop. It just had to leak. Also, the guns on a fighter are machine guns. You could not fire just one round. If you hit, you will have hit multiple time, and created a sieve, possibly tearing the fabric.

The articles didn't say, but the AIM 9 likely did not detonate, unless it was modified to do so, likely passing through the fabric. Maybe they put a remote detonate on it they could command from the cockpit. They usually track, arm, and trigger based on IR. Bear in mind, the point was to recover the electronics intact; that was probably the warmest part of the balloon.

There are two commonly used buoyant gasses used in balloons, helium and hydrogen. (Hot air is a third, but it is far less buoyant, so won't go up that high, takes quite a bit of fuel to keep the air hot, so not for long distances nor long duration flights, and the fuel is heavy. Not practical for this application.) Hydrogen is the lightest element, the gas is H2, so molecular weight 2. It is highly flammable. Helium is monatomic, atomic weight 4, so half as buoyant, and is inert. It is often used for safety reasons. The Goodyear blimps use helium. The Hindenberg used hydrogen.

Helium is also expensive and leaks like crazy. In as much as you can say an atom has a size, helium is the smallest atom. With two protons, it pulls it's outer shell electrons in tighter than hydrogen, and it has only one shell. It will leak through anything eventually.

Hydrogen is cheap, you can make it on site, and if you are sending a spy balloon you expect will be shot down, safety is not a big concern; hoping the entire thing burns up might lead you to consider the flammability to be a bonus.

My guess is China used hydrogen in the balloon, and I don't know how the USAF did not ignite the balloon with the AIM 9. You'd think even passing through would have touched it off.

[ijuin 572]

On 2/2/2023 at 4:48 PM, Don Edwards said:

Ah, the Winged Hussars arrive!

Also my favorite song from Sabaton:

 

[mlooney 3,417]

[Amiable Dorsai 70]

On 2/8/2023 at 9:04 AM, mlooney said:

Some details about the balloon.  And why they didn't use auto-cannon on it.

Thanks, I wish I'd seen this sooner. I'm not sure it would be such a bad thing to have to wait a few days for the balloon to come down, presumably, it would have landed intact and the Navy could be right there to grab it. There is the danger of a booby-trap, of course, but that would completely demolish the Chinese pretense that this was nothing but a weather balloon.

[Darth Fluffy 302]

On 2/21/2023 at 7:20 PM, Amiable Dorsai said:

Thanks, I wish I'd seen this sooner. I'm not sure it would be such a bad thing to have to wait a few days for the balloon to come down, presumably, it would have landed intact and the Navy could be right there to grab it. There is the danger of a booby-trap, of course, but that would completely demolish the Chinese pretense that this was nothing but a weather balloon.

The US wanted to grab it in US territorial waters to avoid the question of our right to do so, because examining the package was a priority. Also, it was not particularly descending; some weather balloons circle the earth multiple times. While not a weather balloon, this was similar in flight characteristics, and was high up, so descent would take a long time. Shooting it down was necessary.

There could have been a self destruct, triggered by descent. In hindsight, that may have been smart, from a Chinese P.O.V. I'm guessing they expected to recover it. It would also add weight, I'm sure keeping the payload light was one of the design goals.

A booby-trap would not be smart. Four reasons: It does not guarantee the self destruct, which is a higher priority. It can be legitimately construed as an act of war. (Think about how it would look if the balloon had a mishap, came down, and was handled by civilians. The Kim's in North Korean might get off on that brinksmanship bullshit, but China is actually civilized and has something to loose.) China probably expected to recover the electronics package, so making it dangerous to do so would be counterproductive. Again, they wanted to minimize payload weight.

Payload weight is particularly important because it affects the altitude the balloon floats at. That it operated at over 60,000 feet is why it was tricky to shoot down, so it's a big part of the balloon's survivability. Also, higher altitude means it can see further, I'm sure that was also a consideration.

[mlooney 3,417]

[Darth Fluffy 302]

Balloons

 

 

[mlooney 3,417]

8 hours ago, Darth Fluffy said:

Balloons

 

 

Given that at least one of the balloons shot down was a hobby nano balloon people might want to start clearing their flights with, if not the DoD, at least the FAA

[Darth Fluffy 302]

12 hours ago, mlooney said:

Given that at least one of the balloons shot down was a hobby nano balloon people might want to start clearing their flights with, if not the DoD, at least the FAA

I head from a buddy that knows HAM radio that at least one of the balloons was a HAM relay.

I think these are allowed by the FAA. I've seen ads for personal weather balloons for many years; Edmund Scientific used to advertise them in kids' magazines. You can't exactly plan a flight path, it begs the question of what happens when one intrudes on restricted airspace.

One mitigating factor is that personal balloons don't seem to reach the altitude that would be a hazard to airlines. Helium is expensive, and leaks like crazy.

The Chinese balloon was impressive in maintaining a high altitude.

[ijuin 572]

You can’t plan a flight path, but above a certain mass, the FAA may require an identification transponder—any object that fails to identify itself in such a manner is regarded as a possible hostile in some situations.

[Darth Fluffy 302]

4 hours ago, ijuin said:

You can’t plan a flight path, but above a certain mass, the FAA may require an identification transponder—any object that fails to identify itself in such a manner is regarded as a possible hostile in some situations.

The FAA rules for weather balloons. Yes, you are allowed to launch one, but there are rules you must follow. I'm going to take a wild guess that other countries have somewhat similar rules. The main concerns are 'stay out of the way' and 'be visible' (to radar as well). There are requirements to track where you are.

I was wrong about the operational altitude, maybe not for home brew balloons. 90,000 to 125,000 is typical (more than one site quoted this, although they might be all quoting the same source). One balloon reached 173,900 feet. I wonder, too, if hydrogen would be a better choice if you were going for altitude and were not too concerned about immediate safety in the vicinity of the balloon.

[mlooney 3,417]

The way around the ATC doesn't see slow moving objects that wouldn't require any change in the ATC systems would be have the balloon squawk Mod 2 IFF. 

[Darth Fluffy 302]

3 hours ago, mlooney said:

The way around the ATC doesn't see slow moving objects that wouldn't require any change in the ATC systems would be have the balloon squawk Mod 2 IFF. 

They could also just choose to not ignore slow moving objects. The balloon systems are required to reflect radar; probably include a dedicated corner reflector. I am curious now how we spotted the Chinese balloon, assuming it wanted to be stealthy.

.You'd think that 'slow moving airborne objects in your airspace above n0,000 feet would be noteworthy. I would pick n at least down to 2. Also, select by sheer size.

[mlooney 3,417]

If you don't reject returns under a given speed you get hits off of birds and some clouds.  Moving Target Indicator is an important part of search radars, less important for tracking radars.

[Darth Fluffy 302]

11 hours ago, mlooney said:

If you don't reject returns under a given speed you get hits off of birds and some clouds.  Moving Target Indicator is an important part of search radars, less important for tracking radars.

Birds is why size matters, although a flock will still throw you off. Most birds fly pretty low, hence 20,000 feet. You could probably do 10,000.

Radar warning of stuff to avoid, if you are in a plane, you probably don't want to ignore the birds.

[mlooney 3,417]

48 minutes ago, Darth Fluffy said:

Birds is why size matters, although a flock will still throw you off.

The radar cross section of most modern western military aircraft is about the size of a large hawk, never mind a stealth aircraft.  There was an incident during the testing phase of Nike-Ajax where a vulture was mistaken for the drone target they were supposed to be firing on and was blown out of the sky.  They only found out about them firing on the wrong thing when they got a call from the range controller wondering what they were firing on as there was a problem with the drone and it had not been launched yet.

[Darth Fluffy 302]

4 minutes ago, mlooney said:

The radar cross section of most modern western military aircraft is about the size of a large hawk, never mind a stealth aircraft.  There was an incident during the testing phase of Nike-Ajax where a vulture was mistaken for the drone target they were supposed to be firing on and was blown out of the sky.  They only found out about them firing on the wrong thing when they got a call from the range controller wondering what they were firing on as there was a problem with the drone and it had not been launched yet.

Obviously, the birds need to evolve better stealth.

Nike Ajax is some ancient history. Appropriate, named for Greek gods and godesses.

[Pharaoh RutinTutin 1,586]

I thought Nike Ajax was a shoe cleaner.

 

[mlooney 3,417]

Snort.  More or less, assuming you want to clean your shoes with red-fuming nitric acid.

[ijuin 572]

I believe that nitric acid is used as a cleaning chemical in some applications?

[mlooney 3,417]

Maybe.  It's a strong oxidizer, so it could act like hydrogen peroxide. 

[Darth Fluffy 302]

14 hours ago, mlooney said:

Maybe.  It's a strong oxidizer, so it could act like hydrogen peroxide. 

Over the counter hydrogen peroxide solution is weird in that it is fairly gentle, while still being a strong oxidizer. I don't know enough chemistry to understand why that works.

[mlooney 3,417]

6 hours ago, Darth Fluffy said:

Over the counter hydrogen peroxide solution is weird in that it is fairly gentle, while still being a strong oxidizer. I don't know enough chemistry to understand why that works.

It's just that higher strength hydrogen peroxide is so much a stronger oxidizer.

[mlooney 3,417]

23 hours ago, Darth Fluffy said:

Nike Ajax is some ancient history.

I was the last tracking radar mechanic to work on a Nike-Hercules site as the duty mechanic.  Nike Herc lasted until the mid 80s, Nike Ajax was phased out in the early 60s for US forces.