If the previous values were for poorly aged rocket motors, it would be all the more reason to give it the revised thrust and burn time values (that were calculated for the “not so poorly” aged rocket motors).
You’re not understanding what I was saying.
Also a 38% increase in peak numbers means nothing because we know the sustainer is progressive as I stated earlier. It may actually be “worse”.
Elaborate please
The sustainer is progressive. That means thrust increases over time until burnout. The peak numbers given do not tell us it has a direct 38% increase in performance, rather that the peak thrust output is a bit higher. The initial and subsequent NASA calculations were not necessarily wrong… at least that is not “obvious” as you claim. What likely happened was they tested a poorly aged motor as well as a better example later on and revised it.
We also do not know how they calculated it or what the accuracy of the calculation was. What we do know is that the official museum placard states 5s boost and 21s sustained which is in-line with the expected performance and propellant mass / fractions shown in the cutaway.
Could you move this information to the correct thread and link the sources?
Of the charts you posted, the R-27ER fails to reach the speeds given in the top one in-game and the second one looks dubious at best. Off a glance appears to lack required deltaV to reach the top speeds shown in the first chart.
It definitely is not worse because if you compare the Apogee-Payload chart between the two versions, it has actually slightly improved.
As compared to the 5s boost and 21s sustained? Follow along.
Yes, I have linked both versions in the report.
Just go to the Improved Orion section and compare the Apogee-Payload charts.
I was discussing as compared to the original fresh motor with the claimed 5s boost and 21s sustained, not the initial worse performing NASA motor.
The museum placard doesn’t provide thrust values anyways. So you can’t really say the NASA data from either versions are worse or better than the placard.
The thrust data is derived from the sounding rocket accelerations claiming 5s boost 21s sustained
Can we please see your calculations?
They stated 19.4 and 20G for the accelerations of the rocket. Calculating the acceleration and weight brings us to 85-95kN rough figures. The math isn’t hard.
Please, do the math and show us how you calculate the boost and sustain thrust from those figures.
I did not say anything about the sustainer thrust.
The peak acceleration claimed in this source is 20G.
In this source it is 19.4G.
Interestingly I was mistaken to believe the 19.4 or 20G figure was for the HAWK motor. The I-HAWK motor is the second stage, and this shows a peak acceleration of approximately 15G with the motor being unable to maintain the peak thrust for a smooth climb. This is likely due to propellant degradation over time in my opinion. The start pattern should hold a better neutral plateau at the top than that.
Although we can more carefully re-create the thrust over time chart if you’d like because the acceleration is given for the rocket over the entire duration of the flight. We know the propellant mass fractions.
When I read this chart it is showing a total burn time from motor start to minimum thrust value of 7.11 seconds peaking at 15G and from there the thrust picks up for a total of 18.96 seconds peaking at 5G. Since the booster struggled to burn efficiently at the top end - it took longer to burn. The propellant didn’t just disappear. We can expect slightly higher peak figures, a shorter burn time, and thus a smoother plateau at the top of the burn on a “fresh” motor.
The mass of the rocket is 514kg. 15 * 9.81 = 147.15 m/s² acceleration.
Force is equal to mass times acceleration, a simple calculator will tell you that the resultant force of this acceleration and mass is approximately 75635.1 Newtons.
When I input this mass and adjust the fuel fractions I can find the reasonable ~255-260 ISP expected of this type of propellant (which is the same type and make as the AIM-7F/M’s… even produced in the same building)… I find the fuel fraction used in the booster to be close to ~212kg for this burn time and thrust. Although the thrust is likely lower and the acceleration increase is caused by the loss of mass over time which is why the booster goes from ~12.5 to 15G peak but I’m not taking that into consideration yet.
Thus, the sustainer starts at ~2G and with a remaining mass of ~301kg for the sounding rocket.
Again, F = MA. I’m going to use the nice round number of 3.75G average acceleration arbitrarily. (2 + 5 / 2 = 3.5, add a bit for benefit of the doubt).
We find a thrust average of 5905.62 Newtons over 18.96 seconds.
Using the correct values for mass and propellant mass specifically I’ll share my data;
Left is the real world expected performance based on my thrust calculations and the proper mass… the right one is the in-game missile.
We know from the grain pattern and acceleration chart that it should have a progressive burn. The available surface area increases as it burns since it is a simple circle pattern. I did the math earlier to determine it should have ~15% more surface area than the start of the burn by the time it ends.
Source
@David_Bowie You can go ahead and forward this chart so the devs can ascertain the proper burn time and thrust for the rocket motor. This is far more comprehensive than any other source we have at the moment.
The mass of the rocket is given in this source;
Not only does it have acceleration over time, but also the altitude over time which gives us the necessary information to determine thrust changes by air pressure and temperature. All of the necessary information is in these two sources. They both claim 5s boost, 21 seconds sustain contrary to the data which shows it always differs slightly from that. This is actually the case with all rocket motors of the era.
I’m sorry, But your calculations are useless, because they don’t even take drag into account.
Acceleration is the result of not just thrust on the mass of the vehicle, but rather the result of the net force, which is the vector sum of thrust, drag and vehicle’s weight.
Perhaps you should leave the calculation of the thrust to actual scientists at NASA and just use their reference rockets handbook?! :)
So even your own source essentially confirms the revised values in the 2023 NASA rockets handbook, but you go through some mental gymnastics to claims that “it’s because it wasn’t a fresh motor” :)
@David_Bowie
No we don’t need that, because we don’t know the drag values for the orbital vehicle in order to subtract the drag from the net force, to be able to calculate the thrust of the rocket motor.
Plus the M112 motor is used as “second stage” motor of this orbital vehicle, meaning it is burning essentially in space, not at sea level …
So it’s useless …
Plus, this is JUST A SINGLE LAUNCH!
So you think the value that you are (incorrectly) calculating from a single launch, is more accurate and representative than NASA’s reference rockets handbook that is most likely taking many many launches into account?!
Atmospheric drag at 20km+ is near zero, you’re looking at fractions of a percent difference. Next slide.
Air pressure at sea level is 14.7 psi… at 10km around 3.84 psi given temperature is the same (it is not). At 20,000m it is even less at 0.79psi.
The aerodynamic drag accounts for a very very small percentage of the missiles’ overall net force here.
Seeing as the missile is being implemented as an air launched missile with lofting in-game and will be operating at practically the exact same altitudes outlined by the charts I shared, it is absolutely the exact source material we need to ascertain burn time and thrust. They know the fuel fractions, and now also the burn time. If they want accurate thrust they can simply adjust until the ISP is around 255-260 and well… there you have it. The missile is accurately modeled.
Surprise surprise, the accurate thrust is around 80kN for the booster and the sustainer is overperforming IMO.