Thread by @SimonHoejbjerg

I always say that planning is 85% of BMD and I've been meaning to do a thread on BMD planning, Sensor cueing and Launch on Remote for some time now.

I finally got around to generate the visual aids needed, so here we go.

This is going to be a long thread!

First of all: All visuals in this thread are notional and not representative of any live systems - this thread is to highlight and discuss principles, not actual system performance og real systems. The visuals are all generated using an unclassified BMD planner and simulator.

Second of all: The examples in this thread are simplified for the sake of discussion. Obviously there are a bunch of (really deep) rabbit holes that one could go down into as well as several very complicated technical details - they might be the basis for another thread one day.

In the scenario I have generated, "Blueland" is going to defend itself against an IRBM threat from "Redland" - both countries are outlined by colored polygons.
In Redland the expected launch area is marked by a red circle.
In Blueland the defended area is marked by a blue circle.

Since we have intelligence information about the IRBM threat's performance, we can calculate all the minimum energy trajectories from the launch area to the defended area. For the rest of the threat, I will refer to these as "the threat tube", because it looks like a tube.

When it comes to planning how to defend against the threat, first we must know which portions of the threat tube are inside the atmosphere and which are outside.

The colors on this threat tube mean:
Red: Threat is boosting inside the atmosphere.
Blue: Threat is outside the atmosphere.
Black: Threat is flying ballistic (not boosting) inside the atmosphere.
This is of course important if we have both endo- and exo-atmospheric interceptors.

Now its time to deploy a land based system to defend the assumed target area.
Here the land based system is shown with its radar's field of view.

Here it can be seen, that the threat tube is passing through the radar's field of view, which is of course required if we are going to be able to defend against the threat.

This illustration shows the kinematic volume for the same system, meaning the area the interceptor can reach.

Just like with the radar's field of view, the threat tube is passing through the kinematic volume, meaning that we can intercept the threat trajectories from the launch area to the assumed target area.

Now, as @EllemanIISS have tweeted several times, detection probability is very important when it comes to BMD. Detecting the threat is the first step of intercepting it, so it's important to maximise the chance of detecting the threat. Radar ressource management matters!

Searching the entire radar's field of view for missiles, means spending vital radar ressources in volumes where we do not expect the threat to fly. This means that we spend less ressources in the area where the threat is actually expected to fly i.e. less chance of detection.

Therefore we create a radar search volume, which is a volume in the air, where the radar is spending (theoretically) all of its energy i.e. maximising the detection probability in that volume. But since we expect the threat to fly here, that's okay.

Having deployed the system and planned the radar search volume, we can take a look at the system's effectivness.
I won't go into details with this, but yellow area can be defended, meaning we are defending the assumed target area.

However, this defended area is depending on Redland only flying the threat as we have planned for. Other types of threats or other trajectories would challenge our defense laydown - especially because we are only using the radar in the search volumes.

And that's of course what will happen - this threat can also fly on a lofted trajectory, which will have a much steeper angle of descent.
This means that threat on a lofted trajectory will overfly the radar search volume, effectively rendering the defense system useless.

This is one of the reasons why having a robust sensor network is really important. By having other sensors, that are searching for threats in other volumes of air, they are able to cue each other to unexpected threats.

A radar cue is simply a message from one radar system to another containing track data on a threat. The receiving system can then predict the trajectory and generate an ad-hoc search volume specifically where the threat is expected to fly.

By introducing a forward deployed sea-based sensor system and generating a search volume that can detect and track any launches out of the launch area, the land based system will be able to recieve a cue to a threat on a lofted trajectory.

As described above, this cue will allow the land based BMD system to reallocate some amount of radar energy to the incoming tracjectory for the lofted threat and establish a track on it, that it can then engage and intercept.

Looking at the effectiveness of the land based system against threats on minimum energy or lofted trajectories, using cues from a forward based radar, we can see that we are again able to defend the assumed target area.

Hopefully, this thread will have shown why a robust sensor network is essential to BMD, and especially why being able to cue systems to unexpected events are critical.

As I said in the first tweet, BMD is 85% planning, simply because the threat fly predictably. This allows us to do detailed planning and wargaming against different threat scenarios, using high fidelity threat information based on intelligence data.

At a later time, I'm probably going to do another similar threat to illustrate the benefit of Launch and Engage on Remote over Organic engagements - and why we need to be able to do launch and engage on remote
But for now, this is the end of this threat. I hope it was interesting