thrust to weight calculator Android app

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jackman

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Does anybody have an app to perform the T:W calc for Android? I've searched and can't find one anywhere. I get tired of always doing the mental gymnastics or using pencil and paper. It would be especially useful if doing RSO duty.
 
Not required. T/W = 4.45 pounds/Newton x Average Thrust in Newton divided by rocket weight in pounds.
 
Not required. T/W = 4.45 pounds/Newton x Average Thrust in Newton divided by rocket weight in pounds.

Dimensional analysis is hard to show on here without fancy fonts, but I think the lbs/Newtons here is either backwards or I'm reading it wrong.

1 lb-force = 4.45 Newtons.

So divide your motor's average thrust by 4.45 to get the thrust in lbs. Then divide this by 5 to get the MAXIMUM recommended liftoff weight of your rocket. (Or, divide by your rocket's weight in lbs to get the ratio)

So an N5800 exerts about 1300 lbs-force, and therefore could lift 1300/5= 260 lbs. (approximately 1 snowmobile).

OR, if you use your N5800 to launch an Estes Alpha, which weighs around 0.05 lbs, your T/W ratio is about 26,000:1, which is more than adequate, even on a short launch rod. Of course T:W may not be the only thing to think about here. :wink:

I think this is right.....


So if you were an RSO in a hurry, aside from slowing down, you could divide the motor's average thrust by 25 to get in the ballpark of a maximum safe liftoff weight and to decide if you needed to look more closely at the rocket/motor specs. But really, slow down.
 
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Easier formula:
Average thrust in Newtons /22.5= weight of loaded rocket in lbs. cannot exceed this value.
Preferably slightly less
When you cut this value too close, rocket tends to get lazy and layover slightly






Dimensional analysis is hard to show on here without fancy fonts, but I think the lbs/Newtons here is either backwards or I'm reading it wrong.

1 lb-force = 4.45 Newtons.

So divide your motor's average thrust by 4.45 to get the thrust in lbs. Then divide this by 5 to get the MAXIMUM recommended liftoff weight of your rocket. (Or, divide by your rocket's weight in lbs to get the ratio)

So an N5800 exerts about 1300 lbs-force, and therefore could lift 1300/5= 260 lbs. (approximately 1 snowmobile).

OR, if you use your N5800 to launch an Estes Alpha, which weighs around 0.05 lbs, your T/W ratio is about 26,000:1, which is more than adequate, even on a short launch rod. Of course T:W may not be the only thing to think about here. :wink:

I think this is right.....


So if you were an RSO in a hurry, aside from slowing down, you could divide the motor's average thrust by 25 to get in the ballpark of a maximum safe liftoff weight and to decide if you needed to look more closely at the rocket/motor specs. But really, slow down.
 
Last edited:
Easier formula:
Average thrust in Newtons /22.5= weight of loaded rocket in lbs. cannot exceed this value.
Preferably slightly less
When you cut this value too close, rocket tends to get lazy and layover slightly

Yes, this is the accurate short way. I suggested 25 because its an easier number to divide by, and it errs on the side of caution. Cutting it closer to 5:1, and certainly with less, requires a closer look at the rocket, motor, and weather, rather than relying on rules of thumb.
 
Dimensional analysis is hard to show on here without fancy fonts, but I think the lbs/Newtons here is either backwards or I'm reading it wrong.

1 lb-force = 4.45 Newtons.

So divide your motor's average thrust by 4.45 to get the thrust in lbs. Then divide this by 5 to get the MAXIMUM recommended liftoff weight of your rocket. (Or, divide by your rocket's weight in lbs to get the ratio)

So an N5800 exerts about 1300 lbs-force, and therefore could lift 1300/5= 260 lbs. (approximately 1 snowmobile).

OR, if you use your N5800 to launch an Estes Alpha, which weighs around 0.05 lbs, your T/W ratio is about 26,000:1, which is more than adequate, even on a short launch rod. Of course T:W may not be the only thing to think about here. :wink:

I think this is right.....


So if you were an RSO in a hurry, aside from slowing down, you could divide the motor's average thrust by 25 to get in the ballpark of a maximum safe liftoff weight and to decide if you needed to look more closely at the rocket/motor specs. But really, slow down.
Doh! You're correct. A senior moment. I've Had my head up a broken laser for the past 5, now 6 days. Should not post when thinking about something else.
 
Given all the discussion I still think it would be nice to have just a simple little app. You enter the average motor thrust and your rocket weight and it computes the ratio. If you leave out the rocket weight it computes the max liftoff weight. Unfortunately my programming skills were left behind with FORTRAN and BASIC :blush:
 
Given all the discussion I still think it would be nice to have just a simple little app. You enter the average motor thrust and your rocket weight and it computes the ratio. If you leave out the rocket weight it computes the max liftoff weight. Unfortunately my programming skills were left behind with FORTRAN and BASIC :blush:

You dont have to be an professional in computer programming
There are apps, you can use exel for mobile
Or download an app like rocksim for android
I dont know at the time what the app is called like,
But when i got home, I will look up the name of the app for you
 
Ok, so if I am doing this right a G80 should lift a max. of 3.59lbs?
80/4.45=17.97, 17.97/5=3.59. My MDRM weighs 2.5lbs, should give it a good ride!
 
Given all the discussion I still think it would be nice to have just a simple little app. You enter the average motor thrust and your rocket weight and it computes the ratio. If you leave out the rocket weight it computes the max liftoff weight. Unfortunately my programming skills were left behind with FORTRAN and BASIC :blush:

For iOS, both RocketCalc and SmartLaunch will calculate T:W ratios (and lots more). Very handy at home and the field. Not sure whats available for other platforms.
 
For iOS, both RocketCalc and SmartLaunch will calculate T:W ratios (and lots more). Very handy at home and the field. Not sure whats available for other platforms.

Yeah, I've seen RocketCalc. It almost makes me want to buy some iStuff, LOL!
 
Here's your app! Works on all smartphones (iPhone, Android, etc) with a photo viewing capability.

Store these two pictures and refer when you want to verify the T:W ratio. Be sure you choose the correct one (LPR/HPR) for the rocket in question.



:)

thrustweight_hpr.jpg
 
Here's your app! Works on all smartphones (iPhone, Android, etc) with a photo viewing capability.

Store these two pictures and refer when you want to verify the T:W ratio. Be sure you choose the correct one (LPR/HPR) for the rocket in question.


:)


I was ready to post these charts ...... Madcow as a nice tool for Iphone, Ipod and Ipad, you enter the weight and the diameter, and it give you choice of motors and give you info about the launch , they use to have one for Android but it don't work with the new Android and I guess it was not popular enough to worth an upgrade. Since my son get is Android phone he don't use is iPod, so I use it for the Madcow software.
 
I've been needing an excuse/idea to start writing Android apps, so I thought a simple thrust to weight calculator would be a good starting point. I uploaded it to the market yesterday, it takes a weight (g, kg, oz or lb) and an average thrust in newtons and displays the thrust to weight. As it's my first app, if anyone would like to see something added or changed, I'll try my best to do it.

https://play.google.com/store/apps/details?id=com.smkrchr.ttw_calculator
 
I've been needing an excuse/idea to start writing Android apps, so I thought a simple thrust to weight calculator would be a good starting point. I uploaded it to the market yesterday, it takes a weight (g, kg, oz or lb) and an average thrust in newtons and displays the thrust to weight. As it's my first app, if anyone would like to see something added or changed, I'll try my best to do it.

https://play.google.com/store/apps/details?id=com.smkrchr.ttw_calculator

That works thanks so much. Any chance you can modify it so that if there's no rocket weight entered it simply computes the max weight allowed using the 5:1 rule.
 
I would like to keep the option to enter the weight, but I may have it so if you leave the weight blank, it will calculated max allowable weight instead.

>> I changed the app so now when you leave the weight blank, it will automatically calculate the max allowable weight. The new version is already on the market.
 
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I would like to keep the option to enter the weight, but I may have it so if you leave the weight blank, it will calculated max allowable weight instead.

>> I changed the app so now when you leave the weight blank, it will automatically calculate the max allowable weight. The new version is already on the market.

I just got the update and it's exactly what I wanted. Thank you so much.
 
I was told T/W radio should be 6:1.
5lb Loaded rocket x 6 -30lbs thrust.
Is this a good rule
 
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