Ballistic Missiles and WiC blog - blahdy

Had some interesting tech discussion with a buddy of mine and the discussion revolved around WiC MW's portrayal of ballistic missiles and the authenticity of battle space. "Battle space" in missile defense parlance, is the altitude/distance (kinematic space) and the 4th dimension, the "time" which defenders have to detect, track and engage an incoming missile.

The higher altitudes your SAMs could go, the bigger your battle space is. This is evident in history of interceptor development -- from the Reagan's SDI ("Star Wars") days, the endo-atmospheric rocket-based kinetic interceptor experiment was called "FLAGE (Flexible Lightweight, Agile, Guided Experiment)". After a successful demonstration of hit-to-kill concept with FLAGE in 1987, the SDI project moved to put this concept into practice, and a new project called ERINT (Extended Range Interceptor) was born.

Right from then in the later years of SDI during 1980's, the new paradigm shift in missile defense development was to "increase" the battle space -- intercepting targets in high altitudes gives you two benefits: (1) debris mitigation -- especially very important for chemical-bio payloads; and (2) more battle space means you have more opportunity to intercept, if first attempt fails. The "ERINT-1" prototype missile specified a much higher 28km intercept altitude, aided by low-noise seeker and 180 side thrusters to provide agility. Fast forward to 1994, the "ERINT" technology concept was chosen to become what is now known as the PAC-3 missile segment (yes, PAC-3 missiles are vastly different than the PAC-2 missiles and share no family lineage whatsoever; PAC-2 is the original Patriot missile, PAC-3 is SDI/Star Wars ERINT missile).

WiC Environment

In WiC, playfields are vastly small so we have to downscale a lot of things. Maps are only 1500 meters by 1500 meters maximum, which means, diagonally speaking, the maximum point-to-point distance you will have in game is about 2000 meters or so. So rather than calling these meters, we just call them "wic meters" or 'wm', because of the down-scaling we have to do.

One interesting feature in WiC and Ground Control EX3D world is that while playfield is limited, the game's skybox is virtually unlimited. It takes about 230km of draw distance before the game quits rendering the sky. This virtually unlimited sky box meant that ballistic missiles and anti-ballistic missiles could be portrayed with significantly less down-scaling than ever before, making the engagement feel more realistic.

Basics about Ballistic Missiles
Ballistic missiles really work in orbital and ballistic mechanics. In the simplest form, they are no different than throwing a stone up in the air and aiming it so it lands on the right spot. But since they are "missiles", they have guidance systems that make sure that the missile continues to point to the right launch angle until its booster burns out. Once it's in the space, it's total free fall. We will refer to the 'apogee' of the flight as Peak Altitude below.

Missile Data in WiC

So here is some data about ballistic missiles in WiC and their relevant speeds, altitudes, etc. Note that "wm" stands for 'wic meters' -- meters portrayed in WiC's down-scaled world.

• SS-21 Scarab (9K79 Tactical Missile Complex Tochka U):
  Peak Altitude: 4,705 wm (equivalent to about 47-50km in real life)
  Re-entry speed (speed at atmospheric ceiling interface): ~Mach 4.9 - 5.0
  Terminal velocity at impact: ~Mach 3.3
• MGM-168 ATACMS:
  Peak Altitude: 4,476 - 4,650 wm (equivalent to about 44-49km in real life)
  Re-entry speed (speed at atmospheric ceiling interface): ~Mach 4.9 - 5.0
  Terminal velocity at impact: ~Mach 3.1 - 3.3
• SS-26 Stone (9K720 Iskander M):
  Peak Altitude: 5,095 - 5,680 wm (equivalent to about 50-56km in real life)
  Re-entry speed (speed at atmospheric ceiling interface): ~Mach 5.7 - 7.1
  Terminal velocity at impact: ~Mach 3.3 - 4.4 (depending on terminal maneuvers)

Note that terminal velocity is slower than re-entry speed -- yes, this is because FLINT engine in WiC actually simulates and calculates atmospheric pressure (drag), decelerating the missile as it negotiates atmospheric pressure at lower altitudes.

You can see that Iskander M comes with highest speed and the most devastating performance of all. Its terminal velocity has the greatest variance, because it throws 10-20G lateral maneuvers while it's coming down at Mach 6+, in order to make interception more difficult. This slows down the missile and exerts great deal of energy loss -- finally, missile then locks onto IR signature and tries to hit a moving target -- another huge G's it has to pull.

Interceptors in WiC:

Let's take a look at counter defenses in WiC for ballistic missiles now:

• PAC-3 MSE:
  Maximum intercept altitude: ~3,216.2 wm (equivalent to about 32km in real life)
  Typical intercept altitude: ~900 - 2,800 wm (equivalent to about 9 to 28km in real life)
  Maximum speed in game: ~Mach 3
  Maximum defended footprint size: ~2.25 kwm^2
• PAC-2 GEM-T:
  Maximum intercept altitude: ~2,200 wm (equivalent to about 22km in real life)
  Typical intercept altitude ~450 to 1,800wm (equivalent to about 4.5 to 18km in real life)
  Maximum speed in game: ~Mach 3
  Maximum defended footprint size: ~0.42 kwm^2

Based on these factors, it takes on average of about 14-17 seconds for PAC-3 missile in game to fly out of the launcher and reach its target at about 2,200 wm altitude. ~15 seconds is very realistic feel in portraying missile defense engagement times, as it is also about the same time it takes for a real-life PAC-2 missile to intercept a ballistic missile target at low altitudes. Engagement times could last for as long as 20-30 seconds in real life, but 15 will do for us in WiC.

Some interesting facts for missile defense system in game:

You'll note that sometimes you'll see a flash "bang" effect when a PAC-3 hits something in the high altitude, but sometimes you don't see anything (yet you know target got intercepted b/c your TA/score just went up). When a target gets intercepted and you don't see the "flash", the interception had likely occurred above 2,100 wm height. Particle effects do not draw at distances longer than 1,500 wm. If you see the flash, but it seems very high, then the target got intercepted at around 1500-1900wm, which it would still be traveling extremely fast (pretty much close to reentry speed with some deceleration).

The "TLL" parameter you see next to TBM count in Patriot message display stands for "Time to Last Launch" -- the amount in seconds the system has to launch its interceptors, in order for them fly up there and hit the target before it becomes unengageable. "Unengageable" means, the target has breached the minimum altitude distance, where it is now impossible to intercept geometry-wise.

Sometimes you'll see a ballistic missile coming down with TLLs decreasing pretty fast (i.e. 13s then 12s, 9s, etc) -- it's probably an Iskander coming down at Mach 7. Or, sometimes you'll also see the rate of "TLL Drop" suddenly slow down or reverse itself where it increases -- this can be caused by one of two things: either (1) the ballistic missile has hit the atmospheric ceiling and is decelerating quite hard due to drag; or (2) it is probably an Iskander that's currently pulling 20G lateral maneuvers, burning energy and slowing down its free fall in the process.

When TLL reaches negative (number turns to red), no more interceptors can be launched -- if the existing interceptor already launched misses its target, it's now considered a "leaker" and no further intercept attempts can be made.