For almost everything in the Southeast Asia region really. Ro-Ros are really common in Indonesia, the Philippines and other nearby countries because you can have them dock on pretty port rudimentary facilities - no need for a pier or a large crane. The Philippines and Indonesia use them so much because we have a huge number of islands and most of them can't support a proper port - with the Ro-ros generally carying both passengers and freight. It took us only about 2-3 years to setup a Ro-Ro network for most of our 7,000 islands for instance; when previously most of those relied exclusively on smaller wooden vessels.
Problem is Ro-Ros are not really that seaworthy, and the article frankly misses the real story - which is that China in fact has pretty terrible sealift capability if it has to rely on civilian Ro-Ros and needs them ready for mass mobilization in case of war.
If you had actual military sealift capability you'd rely instead on LSTs - which operate in a similar manner to the civilian Ro-Ros with a large forward opening; but the LSTs are generally more seaworthy and they have the added advantage of being able to offload cargo on a beach without even a rudimentary dock (some beaches can also support Ro-ros directly, but not all).
This is why the Philippine Navy still has an LST that literally saw action on D-day even though we're never going to do an amphibious landing. And that's because despite their age they're still more seaworthy (one - the Benguet - was a veteran of Operation Dragoon, suffered a grounding in 2004, and yet is still in service today) than most of the flimsy civilian ro-ros plus they can offload supplies in case the dock is destroyed by a disaster as was the case in Yolanda.
I like the one with the drawing of the radiation shadow.
"See? With a lead bulkhead, the crew and passengers are protected from the harmful effects of the reactor's radiation."
"Yeah, but what about the ground crews, people in the terminal, local traffic, other taxiing aircraft, etc.?"
"Fuck 'em!"
"This aircraft was originally called the "Joseph Stalin" aircraft, and had previously appeared in another book. It was said that the aircraft would be built in the near future, and completed before 1960."
"After Stalin's death, this project was modified, becoming the A-10 "Sovietskiy Soyuz""
Some expressed particular dissatisfaction with Germany, the fourth largest economy in the world, which does not meet the 2 percent threshold.
I for one prefer to live in a world where Germany under spends on defense. There track record over the last century when given access to a lot of weapons is a bit disturbing.
Something that has interested me for a while, are shape stabilised projectiles. As in, projectiles that are stable due to their shape. Everybody has heard of rotation stabilised and fin stabilised projectiles, but shape stabilised is kind of different. I guess most of you here have seen shape stabilised projectiles without actually knowing how and why they work.
Geek sidenote: Fin stabilised projectiles are actually fin and rotation stabilised.
As I said, shape stabilised projectile have a stable flight path due to their unique shape.
Figure 1: A 84mm Carl Gustav shape stabilised HEAT-round
Note the slightly ogive front and the stand-off, which are characteristic of shape stabilised projectiles (SSP). Both features are absolutely crucial for the SSP to work. I'm going to throw you guys into the deep end by showing a .gif of the airflow in front of an SSP. Here's a link because I can't embed .gifv apparently The first thing you should notice is the air circulating in some-sort of pocket, and that this airflow is subsonic. Before I continue, here's the airflow in front of a blunt projectile: Clicketyclick While that projectile has a subsonic airflow in front of it as well, it is not circulating.
Here's the airspeed of both projectiles as a normal picture:
Figure 2: Airspeed in front of an SSP
Figure 3: Airspeed in front of a blunt projectile
It's clear that an SSP has a ogive-shaped subsonic airpocket in front of the projectile. This basically emulates the ogive of a normal rotation stabilised projectile. In other words, it makes it more aerodynamic. But does that airpocket stabilise the projectile? No it does not.
So why is this projectile stabilised? The key is in what happens when it starts to tumble. Right now, there is nothing stopping the projectile from tumbling, and that's the interesting thing. There is literally nothing stopping the projectile from tumbling, except...
the projectile itself.
Lets take a look at what happens when an SSP starts to tumble. (If I remember correctly, I rotated the projectile 10 degrees) First off, the airflow in front of the projectile. It's fairly obvious that the airflow has changed. Lets check that again, but this time as a picture.
Figure 4: Airflow in front of a tumbling SSP
Again, it's obvious that the airflow has changed. The subsonic pocket has mainly shifted to one side and the air itself isn't really circulating in the pocket. This change causes a huge change in the Cd of the projectile. Let me show you why.
Figure 5: Pressure in front of a tumbling SSP
Next, the pressure in front of an SSP flying straight.
Figure 6: Pressure in front of an SSP flying straight
Please note the approximate pressure in front of both projectiles. The tumbling projectile has, on one side, twice the pressure as the projectile that's flying straight. Very interesting. What's even more interesting is that the pressure occurs on the opposite of the side it's turning to! The projectile is turning upwards, but the pressure builds up at the bottom. This pressure forces the projectile to start turning down again, forcing the projectile in a state where the pressure on all sides is equal.
Voila, a shape stabilised projectile.
But... why does it work?
The subsonic airpocket is created by the stand-off and that little flange, or whatever you want to call it. The dimensions and placement of both are equally important. The stand-off and its side create the airpocket and the flange give the airpocket the required shape. The stand-off size can vary, but the flange size and placement is very important. If the flange is too far forward or too far back, the airpocket will be either too small or too big. Why does the size of the pocket matter? Because of this:
Figure 7: Subsonic pocket in front of an SSP
I changed the parameters slightly and made all airflow above Mach 1 red. Whatever is not red, is trans- or subsonic. The interesting thing to note here, is the pocket extends to the edge of the projectile (if I made the projectile better it should be exactly on the edge). (Sidenote: Here's the same picture of an SSP at a 10° angle) While the airpocket does not start at the flange, the flange determines where the pocket starts. If, at this velocity, the flange was further back, there would be supersonic flow hitting the front of the projectile, massively increasing drag. If the flange was further forward, the airpocket would be further forward too. This would mean the airpocket would not end at the edge of the projectile, but further out. Creating an airpocket which is wider than the projectile. This would allow the projectile to tumble a bit, because pressures wouldn't change much unless there is supersonic flow hitting the projectile.
It is also possible to change the size of the airpocket by changing the front of the projectile itself. If the radius connecting the front and the stand-off is too big, the airflow inside the pocket would disrupt the circulation. The same would happen if the radius is too small. The angle of the front is important as well, but I haven't expermented that much with it so I don't know how important it exactly is, but it has an effect on the airflow.
By the way, if the flange did not exist at all, the airpocket would start at around a third to half of the stand-off. Which would completely ruin the airpocket. Without a flange, the stand-off itself would have to be way bigger and longer to create the same kind of airpocket.
But Bronezhilet, I hear you cry, if the airspeed changes, the pocket changes as well!
I'm glad you brought that up, because you are right.
A shape stabilised projectile only works properly within a certain flight envelope. If the projectile is moving too fast, the airpocket would compress allowing supersonic flow to hit the front of the projectile. Which in turns increases drag. By a lot. If the projectile is moving too slow the airpocket widens, allowing the projectile to tumble a bit before it would stabilise.
I've been brainstorming with Colli a bit, and we've come to the conclusion that is why some projectiles are both shape stabilised and fin stabilised. When the projectile is moving too slow for shape stabilisation, the fins would keep it pointing in the right direction.
And that concludes today's lesson. Thank you for reading.
AdmiralTheisman reacted to Zinegata in China using civilian Ro-Ro barges for power projection.
