https://community.gaijin.net/issues/p/warthunder/i/RfdZe2n1F4OA
This isn’t true. The propellant weights are switched. Check the standard characteristics page.
Additionally, it is an outlier in regards to drag values compared to peers of similar caliber because the thrust is too high - the drag is also adjusted up. If the thrust was to account for the excessive drag, it is likely all the result of them screwing up the propellant mass fractions which is known data.
https://web.archive.org/web/20221006100904/http://www.alternatewars.com/SAC/AIM-7F_Sparrow_III_SMC_-_January_1977.pdf
37.65kg = 83 pounds
23.58kg = 52 pounds
Hmmm
Here is a report from 2019 showing HTPB propellants finally capable of 300s impulse. The I-HAWK still uses the outdated and poorly aging CTPB… who’s poor aging properties are well known.
Source
It wasn’t an assumption. K_Step went onto the AIM-7 thread on the old forums before the AIM-7F was added, and he said he was modeling the AIM-7F and had issues meeting the range specification while implementing the missile using the given thrust values. That is when, MaMoran (either him or someone else) suggested to him that the thrust values should be increased to compensate due to the longer burntime since the missile has reduced drag during burn.
These are probably because the propellant mass fractions were wrong the entire time - and the drag value has been adjusted too high to account for the excess thrust. If the thrust was set higher to meet range criteria, why is the drag value also adjusted higher than anything else of similar caliber and size / performance?
It would be cool if we could get this actually modeled in-game at some point, doesn’t seem like it would be that hard to do.
A study that provides average thrust over the total burn time:
A sounding rocket payload experiment on zero gravity fuel gauging using modal analysis
https://www.researchgate.net/publication/273308323_A_sounding_rocket_payload_experiment_on_zero_gravity_fuel_gauging_using_modal_analysis
That indicates a higher limit of 210,134 lb-s total impulse based on that median value. Doesn’t do much for us but certainly adds to the available datapool.
My analysis of this study that I’ve added to the report:
A study that provides accurate average thrust over the total burn time of their test launch:
A sounding rocket payload experiment on zero gravity fuel gauging using modal analysis
https://www.researchgate.net/publication/273308323_A_sounding_rocket_payload_experiment_on_zero_gravity_fuel_gauging_using_modal_analysis
The total impulse for M112 according to this study:
36800 N * 25.4 s = 934720 N.s
This is higher than the total impulse we get from the 2023 NASA rockets handbook thrust & burn time values:
6 s * 88964 N + 18 s * 17793 N = 854058 N.s
But this is because in this study, the M112 motor is the second stage, and it burns at high altitude, which results in a higher specific and total impulse.
Whereas the values listed in 2023 NASA rockets user handbook, are for ground launch.
This also explains why the total burn time is 25.4s in this study (second stage, high altitude) but 24s in NASA’s handbook (ground launch). As rocket motors have lower burn rate at lower ambient pressures.
This further validates that the values given in 2023 NASA rockets user handbook are in fact, average thrust, and fairly reasonable at that.
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I understand that the 295.6s specific impulse that we get from NASA’s handbook might seem high for propellants of that era.
But keep in mind that:
1- There is a reason why this motor has been also used extensively for space applications.
(Perhaps the composition that it uses sacrifices stability for higher specific impulse.)
2- The study I posted above further validates that this rocket really does have a quite high specific impulse.
While the values presented by this study are for high altitude burn, it does confirm that the values that NASA’s handbook provides for ground launch are not unreasonable.
How did you come to that result? The impulse can’t be that high. It simply isn’t possible for the fuel used.
Your propellant mass fractions must not be correct.
The median thrust value cannot be used to determine the total burn time’s overall impulse.
Yes, its always better to have more source materials. So I’d include everything but if I understand this right this is a debate between one doc giving very specific figures and one giving more general figures but also both from NASA?
If it was in the form of a report sure.
No
We have two sources that actually provide thrust figures
1- 2023 revision of NASA’s rockets user handbook: This handbook has revised and changed the thrust and burn time values that it lists for M112 (Improved Orion) as compared to the 2005 revision of the same handbook.
(from 4s @ 19000 lbf + 21s @ 3000 lbf in 2005 revision to 6s @ 20000 lbs + 18s @ 4000 lbf in 2023 revision)
2- The study that I’ve posted above which gives accurate average thrust for the whole burn time, from which we can calculate the total impulse.
The burn happens at high altitude (second stage), but it results in a very high specific impulse, even higher than NASA’s values, which validates NASA’s handbook’s values for a ground launch.
Also the burn time in this study, which happens at very high altitude, is 25.4 seconds which further validates the 24s burn time for ground launch that the NASA’s handbook provides.
This also means that the 26s burn time figures are incorrect (or most likely for when the rocket is used as second stage booster, at very high altitudes)
I made a report here:
https://community.gaijin.net/issues/p/warthunder/i/EaLuXWmNnW4F
@MiG_23M is trying to guesstimate the thrust from studies that don’t directly provide thrust values, but only acceleration charts. And he’s assuming the drag to be zero which completely invalidates his results.
He’s claiming the NASA source is average thrust and trying to justify it by blinding himself from viewing the other sources.
His claim would indicate an impulse well and above what the propellant type is capable of, which imo is a dead giveaway that the thrust values given are not “average”.
The boost is a neutral burn, ramps up to peak and plateaus before burning off and starting the sustainer propellant burn. Since the sustainer is a circle with no grain pattern - it is a progressive burn. It increases thrust as it burns because surface area increases as the propellant is burned away closer to the sidewall.
^ this is evident in the acceleration chart as we see the sustainer increase average G load as propellant mass is burned off. This is both from the reduction in mass as well as the increase in thrust.
Since the sustainer cannot be properly modeled in the game (they don’t model dynamic thrust)… gaijin needs to adjust the sustainer to use average thrust values. His calculations assume the values given are already average and this isn’t possible if impulse reaches beyond 260s.
I did no such thing, lying to the tech mod will only show your truly biased intentions.
Well that’s exactly what you did.
Did you take drag force into account when calculating the thrust from the acceleration charts?
Where are your drag calculations?
Where are your mass charts/calculations?
How maneuverable is the Fakour supposed to be? Is it just going to be a re-branded aim-54?
I’m not pushing gaijin to use the thrust values that I came up with. You are pushing for them to insert peak values and cause it to overperform.
In theory both should be more maneuverable than they are in-game but we don’t know.
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I’ll simplify it for you - the Fakour-90 is like a AIM-54 with the engine of the R-27ER + less manoeuvrability (by a tiny bit). It will beat all missiles to target by a large margin (what I’ve seen so far), this will make it pretty nice to use.
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They are not peak values.
NASA’s rockets user handbook does not list peak values for any other motor. So there is no reason why they would list peak values for this one. Because peak thrust is not very useful. What is useful to the audience of the NASA rockets user handbook (engineers and scientists looking to choose a motor) is average thrust. Peak thrust is useless to them …
For other motors they use the term “average thrust” but for this one they use “approximate thrust”.
Which essentially means “approximate average thrust” … They just don’t provide an “exact” value unlike for other motors.
The study above is also providing average thrust as is very clear from both its wording and the value that it is providing: “8273 lbf = 36800 N”
Your claim that this is the “Median thrust” is completely made up …