Yet seems to not be modeled for AIM-9M currently, and might not be modeled for AIM-54C even if it gets reduced smoke, getting all of the benefits without the disadvantages.
@k_stepanovich Why was the AIM-9M given the smokeless motor without proper implementation? Seems bad form to add a big advantage (smokeless motor) without giving its accompanying disadvantage (lower ISP)?
Hopefully there will be a review on this.
A big problem I can see is people attempting to constantly report and have smokeless motors implemented into the game on several missiles without having an actual realistic implementation for it.
I went and found some sources, I was incorrect… it’s not 15% less ISP.
The AIM-9M uses HTPB-AP binder, and is very low viscosity so should use relatively harge % of binder (35-40%?).
If so, isp in comparison to AIM-9L should be 9.2-11.5% less.
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Even with a conservative assumption of 10% of thrust loss, I would assume the range loss would be greater than 10% compared to AIM-9L.
A decrease in ISP does not necessarily mean lower thrust. It only means less efficient propellant, which could be due to a lower exhaust velocity or higher mass flow rate.
Burn time is stated to be the same iirc, only way to reduce ISP is decrease thrust
Regardless, 10% less thrust or 10% less burn time
Assuming the burn time is the same, the ISP would decrease if
- The Thrust was less
OR - The smokeless propellant is denser. Increasing the mass flow rate (g/s) would also reduce the ISP but have marginal effect on real performance. The missile will start slightly heavier but by the end of the burn will weigh the same as the 9L
There is no mention of increase/decrease in burn time or weight of the missile aside from changes to seeker technology from any source I can find.
Seems the thread is staring off topic due to the apparent unwillingness to change the AIM-54C to a reduced smoke motor…
do we have list for missile technical data from before?
Efficiency of the reduced smoke propellant is a critical component to correctly modeling the AIM-54C.
If there is no mention of any change in it’s parameters why would we assume it’s thrust is lower? It is not clear if/why a smokeless/reduced smoke motor has to be less efficient. If all the available data says the 9M has the same performance as the 9L it probably has the same performance as the 9L
And, all known data about the 54-C seems to imply increased range and speed compared to the A model
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It specifically mentions change to HTPB, a known tradeoff is ISP in comparison to CTPB… just had to find out how much.
To be fair the situation with the AIM-54 is slightly different than the sidewinder. From what I understand the 9M kept the 9Ls motor with the only difference being the actual propellant in it. With the Phoenix however the 54C uses a completely different motor
No, it’s just the Mk47 with propellant being changed from CTPB to HTPB, same deal.
Except the Mk47 mod 1 also has 4 pounds less propellant as well.
From what I understand of the AIM-54 motor situation, its actually a bit more complex than that?
I seem to remember that there are 2 completely different motors for the AIM-54, and each has 2(?) variants as well(?)
I’ve heard of the the Mk47 mod 0 and mod 1 as well as the Mk60 mod 0 and mod 1. Both motors have (afaik) different thrust and different burn times, as for the differences in versions of each motor, im not 100% sure.
I cant really find any info on the subject right now, but ill look into it some more. IIRC though, the AIM-54’s in-game use some weird bastardized version of both motors?
AIM-54A has two companies that produce a similar motor, Mk47 and Mk60.
AIM-54C appears to solely use Mk47 mod 1.
Everything else you said is a DCS-ism.
I think you’re misunderstanding how solid propellants work. Both HTPB (Hydroxyl-terminated polybutadiene) and CTPB (Carboxyl-terminated polybutadiene) are binders. They have very limited, if any, impact on the fuel mixture’s performance. Regardless of which binder is chosen the part of the fuel mixture that actually provides the power is some combination of ammonium perchlorate and a reactive metal (aluminum/zinc/magnesium). A change in the binder will not produce a noticeable decrease in performance and perhaps most importantly Wouldn’t eliminate/reduce the smoke. An example of that is the PSLV from ISRO. All rocket stages are HTPB based but absolutely create a massive smoke plume. I would assume the part that makes a motor smokeless is the more complete combustion of it’s propellants. I honestly don’t have a clue about the chemistry around making it smokeless but changing the binder won’t do that
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