There are lots of programs, including many commercial programs, that will predict the maximum altitude of a model rocket. There are some inexpensive altimeters out there also that can give altitude results when placed inside your model during flight. Are they trustworthy? I wasn't sure so I had an idea to see if I could come up with a LB program that would predict accurately (within 5%) the height of a model rocket.
The main reason for my interest was that I was involved in a rocket altitude contest and as an official, I was concerned that the altimeters were subject to problems. I noticed that every once in a while, a spurious reading would occur. I wanted something that could check the validity of the readings I was getting. It was obvious to me that some readings were just not right. I wanted a program that I could enter rocket mass and motor type and the program would output a reasonable expectation of altitude.
Of course this program is more involved than the others presented on this page so I needed some help. I got a great deal of help from Mr. John Fisher who lives in Merry Old England. Some of you know him as tenochtitlanuk from the Liberty Basic Forums. He had most all of the programs already written and only needed slight modifications to satisfy some of the requirements that I had wanted. I give all credit for these programs to him.
I knew published data was available for model rocket thrust curves. I was not sure how accurate this data was as I was concerned that companies that make the motors might tend to exaggerate the numbers. I began a series of tests using an analog to digital interface and a force probe to measure force and time data and integrated these curves to obtain impulse data for various rocket motors. I have to say that the published data is very close to my measurements. The first bit of code presented here represents a rocket flight simulation for an Estes A-8 rocket motor pushing a 37 gram rocket. This includes a parachute deployment and subsequent terminal velocity to ground. Again- John Fisher is the author.
'EstesA8.bas'This program uses the thrust data to draw a position/time, velocity/time, and acceleration/time'graph for a rocket of mass 37 grams and an A-8 Estes engine.nomainwinUpperLeftX=10UpperLeftY=10WindowWidth=1100WindowHeight=700graphicbox#w.g,10,10,1010,610textbox#w.t,10,620,610,30open"Rocket vertical flight simulation"forwindowas#w
#w,"trapclose [quit]"#w.g,"size 2 ; goto 5 505 ; down ; goto 950 505"
RocketBodyMass =0.030' fixed mass of rocket body
RocketFuelMass =0.0033' 3.3 gram of fuel
EngineCasingMass =0.0164' 17gram casing & nozzle.
burntime = .7 ' burn lasts for this time
burnrate = RocketFuelMass / burntime ' assume linear reaction rate
Area =0.0004' cross sectional area of rocket
Gravity =9.81' acceleration of gravity
AirDensity =1.2' density of air
DragCoefficient =0.75' allows for the streamlined shape
y =0' initial vertical height
vy =0' initial vertical displacement
time =0' initial time
deltat =0.001' time interval between updates
acceleration =0
hasTakenOff =0global RocketBodyMass, RocketFuelMass, EngineCasingMass, burntime, burnrate
global Area, Gravity, DragCoefficient, y, vy, time, deltat , Gravity, AirDensity
[here]
force =thrust( time)- Gravity * mass( time)- drag( time)if hasTakenOff <>0then acceleration =force / mass( time)else acceleration =0if thrust( time)>( mass( time)*Gravity)then hasTakenOff =1
vy = vy + acceleration *deltat
#w.g,"color green ; set "; 5+600*time /10; " "; 505-500*vy /250
y = y + vy *deltat
time = time + deltat
#w.t," Time = "; using("##.###", time); " force = "; using("##.###", force);_
" acceleration = "; using("#####.##", acceleration); " velocity = "; using("###.##", vy);_
" and height = "; using("#######.##", y)#w.g,"color black ; set "; 5+600*time /10; " "; 505-500*y /120scanif y <500and y >-.1 thengoto[here]wait' _____________________________________________________________________function thrust( tt)
th =0if tt <=.7 then th =-0.0229*tt +2.362if tt <=0.395then th =-10.9*tt +6.662if tt <=0.27then th =-151.3*tt +44.54if tt <=0.225then th =53.49*tt -2.049if tt <0.035then th =0.0' if tt <=1.6 then th =3'if tt <=0.3 then th=10 -80 *( tt -0.2)' if tt <=0.2 then th =50 *tt#w.g,"color red ; set "; 5+600*time /10; " "; 505-500*th /50
thrust =th
endfunction' _____________________________________________________________________function mass( tt)selectcase tt
case tt <=1.6' it burns 0.0035kg in 0.7s.
m =RocketBodyMass +EngineCasingMass + RocketFuelMass - tt *burnrate
caseelse
m =RocketBodyMass +EngineCasingMass
endselect
mass =m
endfunction'____________________________________________________________________________function drag( tt)if vy >0then drag =0.5*AirDensity*vy^2*DragCoefficient *Area else drag =-0.5*AirDensity *vy^2*DragCoefficient *Area
if tt >6then drag =-0.5*AirDensity *vy^2*DragCoefficient *0.05endfunction[quit]close#w
end
There are lots of programs, including many commercial programs, that will predict the maximum altitude of a model rocket. There are some inexpensive altimeters out there also that can give altitude results when placed inside your model during flight. Are they trustworthy? I wasn't sure so I had an idea to see if I could come up with a LB program that would predict accurately (within 5%) the height of a model rocket.
The main reason for my interest was that I was involved in a rocket altitude contest and as an official, I was concerned that the altimeters were subject to problems. I noticed that every once in a while, a spurious reading would occur. I wanted something that could check the validity of the readings I was getting. It was obvious to me that some readings were just not right. I wanted a program that I could enter rocket mass and motor type and the program would output a reasonable expectation of altitude.
Of course this program is more involved than the others presented on this page so I needed some help. I got a great deal of help from Mr. John Fisher who lives in Merry Old England. Some of you know him as tenochtitlanuk from the Liberty Basic Forums. He had most all of the programs already written and only needed slight modifications to satisfy some of the requirements that I had wanted. I give all credit for these programs to him.
I knew published data was available for model rocket thrust curves. I was not sure how accurate this data was as I was concerned that companies that make the motors might tend to exaggerate the numbers. I began a series of tests using an analog to digital interface and a force probe to measure force and time data and integrated these curves to obtain impulse data for various rocket motors. I have to say that the published data is very close to my measurements. The first bit of code presented here represents a rocket flight simulation for an Estes A-8 rocket motor pushing a 37 gram rocket. This includes a parachute deployment and subsequent terminal velocity to ground. Again- John Fisher is the author.