Help checking missile acceleration calculations.

[KJakker]

I would like to ask some people to please check my math for me with regard to SF2 missile acceleration.

 

First, I recommend opening the links below as tabs in a separate browser window, plus your Windows calculator in scientific mode with the unit conversion panel open.

 

Calculating rocket acceleration<-----Formula Source.

 

Convert Meters Per Second Squared to Standard Gravity

 

Convert Standard Gravity to Meters Per Second Squared

 

Convert Pounds-force to Newtons

 

Velocity, Acceleration and Time Calculator

 

Uniform motion (travel distance) Calculator

 

WesternElectricNikeHerculesBrown.pdf<-----The bulk of the missile data was drawn from this document.

 

Missile Data <-----This was used to fill in some blanks. 

 

 

Now, here is the issue. I am calculating the booster and sustainer acceleration g-force for two missiles.

 

||-----Formulas-----||

 

Weight (in kg) = Mass (in kg) x 9.81

 

Resultant Force (newtons, N) = Thrust (in N) – Weight (in kg)

 

Acceleration (m/s²) = Resultant Force (newtons, N) ÷ Mass (kilograms, kg)

 

//-----MIM-3 Data-----\\

 

The MIM-3 missile has a combined missile-booster weight of 2499.3 lbs (1133.663410341 kg).

The missile’s weight is 1193.3 lbs (541.271775121 kg).

The booster’s weight is 1306 lbs (592.39163522 kg).

 

The booster produces 59,000 lbs of thrust (262445.0753 N) for 3.5 seconds.

The sustainer produces 2600 lbs of thrust (11565.3762 N) for 20.8 seconds.

 

//-----MIM-3 Calculations-----\\

 

Missile With Booster

 

11121.23805544521 kg = 1133.663410341 kg x 9.81

 

251323.83724455479 N = 262445.0753 N– 11121.23805544521 kg

 

221.69176049261208816117588018214 m/s² = 251323.83724455479 N ÷ 1133.663410341 kg

 

22.606268 g = 221.69176049261208816117588018214 m/s²

 

Missile With Sustainer

 

5309.87611393701 kg = 541.271775121 kg x 9.81

 

6255.50008606299 N = 11565.3762 N – 5309.87611393701 kg

 

11.557040979394478940811698611408 m/s² = 6255.50008606299 N ÷ 541.271775121 kg

 

1.178490g = 11.557040979394478940811698611408 m/s²

 

For Data File...

 

BoosterDuration=3.500000

BoosterAccel=22.606268

 

SustainerDuration=20.800000

SustainerAccel=1.178490

 

\\-----MIM-14 Data-----//

 

The second missile has a combined missile-booster weight of 10,550 lbs (4785.3995035 kg).

The missile’s weight is 5,250 lbs (2381.3599425 kg).

The booster’s weight is 5,300 lbs (2404.039561 kg).

 

The booster produces 173,600 lbs of thrust (772211.272409 N) for 3.4 seconds.

The sustainer produces 13,750 lbs of thrust (61163.04721 N) for 29 seconds.

 

\\-----MIM-14 Calculations-----//

 

Missile With Booster

 

46944.769129335 kg = 4785.3995035 kg x 9.81

 

725266.503279665 N = 772211.272409 N – 46944.769129335 kg

 

151.55819336488235166633669125594 m/s² = 725266.503279665 N ÷ 4785.3995035 kg

 

15.454635g = 151.55819336488235166633669125594 m/s²

 

Missile With Sustainer

 

23361.141035925 kg = 2381.3599425 kg x 9.81

 

37801.906174075 N = 61163.04721 N – 23361.141035925 kg

 

15.874083333403933748247300082398 m/s² = 37801.906174075 N ÷ 2381.3599425 kg

 

1.618706g = 15.874083333403933748247300082398 m/s²

 

For Data File...

 

BoosterDuration=3.400000

BoosterAccel=15.454635

 

SustainerDuration=29.000000

SustainerAccel=1.618706

Edited March 16, 2016 by KJakker

[Fubar512]

Interesting....this has been hashed over several times over the years. I was using tables that were available on NASA's website for my calculations.

 

The big issue is with Missiles like the MIM-14 and the SA-5, which in RL fly different profiles depending on the range of the target.  If the target is at the short end of the missile's engagement envelope, they basically fly a direct intercept profile, like any  medium-range SAM would.  If the target is at the outside edge of the envelope, they both use a "loft" profile, and the final engagement involves the missile descending into it's target (or ahead of the target's flight path, as would the case with the nuclear-tipped variants of both birds).  

 

If one were to set the weapon data entries up with a loft altitude, it would more than likely affect their ability to effectively engage most targets in-game. Damned if you, Damned if you don't 

[Snailman]

You are lucky if you have data!  I did this for 50+ missiles for the RSSW pack...  In many cases it's a pain in the big A, even with available RL data - but what to do. With this system we have and tools it is a happy result if we produced something near similar.

 

What I did, was entering real life values into the missile range calculator proggy, then thought it over, which values must stay, which can be altered.

My goal was end-user performance, with priority

1. Correct range (including passive flight,) with correct lifetime (self-destruct)

2. Correct engine operating time

3. Correct speed - if possible - it is hard to test because missile range  calculator has only one height setting (IAS/TAS) so you have to check at low alt (0.95) medium (0.8616) and probably high (0.6 or 0.40) - then test fire against actual targets in-game and watch the speed value in debug mode +custom weapon view

5. Correct to-hit chance - another story of radar/jammer/missile issues

6. Altitude range, it has to be set in the attached SAM_Radar class network object (MinRadAlt + MaxRadarAlt), in mind with intermediate zones I mentioned

7. Misc features like maneuverability/guidance etc etc - have to consider guidance types here - as with Rear60 IRMs Beam-Rider (tail chasing) guidance routine is also useless.

    I changed all SA-2 to SemiAuto - which is a bit strong but there is no such guidance which would  be in-between the two (command guidance with lead-computing)

 

Before

 

After

 

 

Use the cutoff speed to fix the operating time.  In case the missile system can guide a single missile only, it's important to optimize missile lifetime. The stock SA-2 after a miss, cannot fire a second missile for an entire minute until the previous one ends it's run on ballistic.

Edited March 17, 2016 by Snailman