@JoshMan Keeping the engine bells parabolic as almost all engines are today the calculations could been done as algebraic expressions of four variables (length, width, flatness/length points along parabola, and the pressure within the compression chamber [which would be a property of the material used and would impact how much fuel the rocket used per unit time]), if engine parts were characterized by their combustion chamber volumes and pressures omitting combustion chamber material as a factor and instead just provided static values for volume and initial pressure of the combustion chamber then the pressure at the end of the chamber is given by:
p=(V0*p0)/([((4piB)/(3(sqrt(N+L)+B_0))[((N+L)^3/2)-(N^3/2)])+2piB_0*L])
where;
B is the radius of the end of the nozzle
L is the length of the nozzle
N is a factor defining the flatness of the nozzle.
Then constants which would be properties of the particular engine part are as follows:
V0 is the initial volume of the combustion chamber
B0 is the radius at the base of the nozzle
p_0 is the initial pressure of the combustion chamber (this is where higher/lower thrust parts come in)
This calculation gives a nice closed form expression taking only given and defined inputs and providing the exhaust pressure which can easily be related to the efficiency of the engine. And considering closed forms are what computers excel at doing this calculation should take no more then one line of calculation, excluding variable declarations. If for example the computer had to constantly do the integration I just did it may be more intensive, but a general solution like this taking only inputs and providing answers seems, at least from my programming experience, to be a fairly straight forward thing to do.
I've been doing various test runs and delta V required to achieve LDO appears to be approximately 5.57 km/s
Atmosphere air pressure can also be roughly approximated by the function:
p(h)=14.7exp(-(x/40000)^2)
units being PSI,
that was calculated experimentally taking engine thrust measurements every kilometer to look at dropoff, best fitting a gaussian packet, determining engine chamber pressure in vacuum, then solving for external air pressure as a function of altitude.
@MrTaco I feel like if given a selection of default engine configurations with pre determined tasks, for example a landing engine, or a vacuum specialized engine it would allow people to bypass this mechanic if they so choose, and for others in the edit part menu these options will be available to play around with an see what they do, engine plumbing and design is a fun aspect of rockets I have not seen in a game yet and could show further diversity in rocket science. It by no means has to be something players are required to use, even an option by which we can modify the shape of the nozzle and choose whether it behaves according to its shape, or follows presets just for the sake of modeling historical rockets more accurately.
@JoshMan I have put together a program as you suggested, it is currently able to take in all the variables I listed in the OP with a few shortcuts applied to omit temperature and fuel type considerations, in the current form it has no trouble spitting out reasonable Isp values practically instantly, so computational power shouldn't be an issue.
@jacksawild Your delta V may be slightly more accurate. I solved deltaV by using the rocket equation but alas I utilized the vacuum exhaust velocity for both atmospheric and orbital flight which will contribute some error. My method was manual reading of rocket masses at each stage using 8 different rockets all entering into a 115x115 then summing a total dV.
I'll try to put together a much more thorough experimental run at some point over the next few days.
The average atmospheric density between surface and 100km is about 5.21 PSI
@AndrewGarrison This did end up being the issue, forgot I had two spent boosters sitting around on the runway. Running a clean save now without issues.
computer is able to run other, significantly more intensive games on ultra and has no problem with SR2 after initial minute of lag. Machine was made specifically to run FEA and CFD on fairly complex CAD files. Should be significantly more beefy then anything this game requires. I didn't have issues in the early closed beta either.
weapons work just fine in orbit and vacuum environments
My impressions on this are that weapons would be a relatively trivial thing to add to the game, and being a sandbox game, more capabilities can never hurt.
@JoshMan yea I might try to do the same but I have no real modding experience, I can provide you with the math though if you decide to go for it. The main reason I actually broke my silence and made an account was to post this :P
@JoshMan Keeping the engine bells parabolic as almost all engines are today the calculations could been done as algebraic expressions of four variables (length, width, flatness/length points along parabola, and the pressure within the compression chamber [which would be a property of the material used and would impact how much fuel the rocket used per unit time]), if engine parts were characterized by their combustion chamber volumes and pressures omitting combustion chamber material as a factor and instead just provided static values for volume and initial pressure of the combustion chamber then the pressure at the end of the chamber is given by:
p=(V0*p0)/([((4piB)/(3(sqrt(N+L)+B_0))[((N+L)^3/2)-(N^3/2)])+2piB_0*L])
where;
B is the radius of the end of the nozzle
L is the length of the nozzle
N is a factor defining the flatness of the nozzle.
Then constants which would be properties of the particular engine part are as follows:
V0 is the initial volume of the combustion chamber
B0 is the radius at the base of the nozzle
p_0 is the initial pressure of the combustion chamber (this is where higher/lower thrust parts come in)
This calculation gives a nice closed form expression taking only given and defined inputs and providing the exhaust pressure which can easily be related to the efficiency of the engine. And considering closed forms are what computers excel at doing this calculation should take no more then one line of calculation, excluding variable declarations. If for example the computer had to constantly do the integration I just did it may be more intensive, but a general solution like this taking only inputs and providing answers seems, at least from my programming experience, to be a fairly straight forward thing to do.
Thanks for the feedback!
+2 6.0 years agoI've been doing various test runs and delta V required to achieve LDO appears to be approximately 5.57 km/s
Atmosphere air pressure can also be roughly approximated by the function:
p(h)=14.7exp(-(x/40000)^2)
units being PSI,
that was calculated experimentally taking engine thrust measurements every kilometer to look at dropoff, best fitting a gaussian packet, determining engine chamber pressure in vacuum, then solving for external air pressure as a function of altitude.
+1 5.5 years ago@AndrewGarrison I just posted a streamlined version of this on user voice.
+1 5.9 years ago@MrTaco I feel like if given a selection of default engine configurations with pre determined tasks, for example a landing engine, or a vacuum specialized engine it would allow people to bypass this mechanic if they so choose, and for others in the edit part menu these options will be available to play around with an see what they do, engine plumbing and design is a fun aspect of rockets I have not seen in a game yet and could show further diversity in rocket science. It by no means has to be something players are required to use, even an option by which we can modify the shape of the nozzle and choose whether it behaves according to its shape, or follows presets just for the sake of modeling historical rockets more accurately.
@JoshMan I have put together a program as you suggested, it is currently able to take in all the variables I listed in the OP with a few shortcuts applied to omit temperature and fuel type considerations, in the current form it has no trouble spitting out reasonable Isp values practically instantly, so computational power shouldn't be an issue.
+1 6.0 years agoIf anybody's up for making me #8
5.5 years ago@jacksawild Your delta V may be slightly more accurate. I solved deltaV by using the rocket equation but alas I utilized the vacuum exhaust velocity for both atmospheric and orbital flight which will contribute some error. My method was manual reading of rocket masses at each stage using 8 different rockets all entering into a 115x115 then summing a total dV.
I'll try to put together a much more thorough experimental run at some point over the next few days.
The average atmospheric density between surface and 100km is about 5.21 PSI
5.5 years ago@AndrewGarrison This did end up being the issue, forgot I had two spent boosters sitting around on the runway. Running a clean save now without issues.
5.5 years ago@Caveman999 Lenovo 80X7 with GTX 1050
computer is able to run other, significantly more intensive games on ultra and has no problem with SR2 after initial minute of lag. Machine was made specifically to run FEA and CFD on fairly complex CAD files. Should be significantly more beefy then anything this game requires. I didn't have issues in the early closed beta either.
5.5 years agoweapons work just fine in orbit and vacuum environments
5.5 years agoMy impressions on this are that weapons would be a relatively trivial thing to add to the game, and being a sandbox game, more capabilities can never hurt.
If you want a meme look at the Saturn V, it couldn't even carry itself 3.5 miles, ACROSS LAND, without assistance. P A T H E T I C
5.6 years agoMore then 10.
5.8 years ago@JoshMan yea I might try to do the same but I have no real modding experience, I can provide you with the math though if you decide to go for it. The main reason I actually broke my silence and made an account was to post this :P
6.0 years ago