How many grams of rocket will a motor push?

[techrat]

I know there are already some statistics of how many grams can be lifted by some of Estes black powder motors, for example in a chart found on the internet, I can state that a D12-7 will lift 226 grams of rocket. Is there a chart like this for Aerojet/Q-Jet motors?? My Super Big Bertha is clocking in at about 410-420 grams. I have an E30-4T and 29mm-24mm adapter planned for its first launch in Feb, where, due to the possible weather situation in Feb, I'd prefer a low and slow flight. An "F" would be overkill this time around. Do we know how many grams of rocket can be pushed off the pad by the E30??

 

[DigBaddy]

Search for the terms "thrust to weight". Should turn up a lot of threads and posts on it.

 

[techrat]

Wow, thrustcurve.org seems to say that the minimum is an F47, although I have a heavier rocket that flew quite high on an F23, so I'm doubting this is 100% accurate.

 

[techrat]

OK....
My rocket weighs 0.9 pounds. The E30 has an average thrust of 32.4 newtons for a thrust to weight ratio of 7.8, which is more than 5x, so according to that data, I am safe to fly.

 

[SolarYellow]

Download Open Rocket and make sure your velocity off the rod is good. Export the detailed sim output as a .csv and check your stability off the rod.

 

[tsmith1315]

The E30 has an average thrust of 32.4 newtons for a thrust to weight ratio of 7.8

Look at initial thrust, as that’s what gets the rocket up to a speed where the fins are working before it leaves the rail.

For that, you need to look at the motor’s thrust curve.

 

[dhbarr]

AT E30
* 49.30 newtons peak
* 32.95 newtons avg

You have 420 grams (is that with or without the mass of the motor?) so at peak you're 12:1 and on average 8:1

 

[waltr]

Yep, lots of rules of thumb to use.
3:1 TTW ration is minimum by NAR and most clubs want to see 5:1 TTW which is based on Average motor thrust.

ThrustCurve.com is useful but a sim is most useful. Speed off the rod/rail (as stated above) is very important to ensure stable flight (why 5:1 TTW).

The other consideration, which is in the Estes recommendations, is the Delay time. Reason is a heavier rocket will reach apogee in a shorter time so needs a shorter delay time to ejection.
The Estes Chart should also have delay time to select max weight.
Delay times is also info to obtain from a good sim to help select the correct motor delay or drill delay to correct time..

Now all that is for a 'safe' launch and recovery.

Op's question is: What weight rocket can a motor lift?
Well if the Peak Thrust is higher the the rocket weight it will lift.
How far and how fast is not going to be much.
Easiest to play with this in a sim. Pick a rocket and a motor, run sim, add weight (mass object) and rerun sim.

 

[Scott_650]

Wow, thrustcurve.org seems to say that the minimum is an F47, although I have a heavier rocket that flew quite high on an F23, so I'm doubting this is 100% accurate.

TC’s default safe launch speed can be a bit on the conservative side - which makes sense considering it’s not meant to be a full simulation program - you can plug well known rocket/motor combos into TC and it’ll down check them for being too slow off the rail. As already mentioned a good sim file run in OR or RocSim is better tool if you’re looking for more than “will motor A fly rocket B safely?”.

 

[lakeroadster]

... .Is there a chart like this for Aerojet/Q-Jet motors?? ...

From the Aerotech website:

Maximum Liftoff Weight: Due to the variables involved, AeroTech/Quest currently does not list or post recommended maximum lift-off weights for their mid-power and high-power rocket motors. Instead, we recommend utilizing either the RockSim software available at www.apogeerockets.com or OpenRocket Simulator available at www.openrocket.info.​

 

[techrat]

Bummer. I'm going to have to start learning that OpenRocket software now. I have been putting that off because I build from my head and my hands, not from a computer. I have never modeled parts or weighed them, I just throw stuff together and see what works and what doesn't. I've literally been doing it this way since I was a child, and now I have to change the way I do things.

 

[BigMacDaddy]

Not sure where I found it (maybe Apogee?) but I have max lift data on Estes and Quest... (I launch heavy rockets so calculate max lift vs motor weight to find most efficient motors.

 

[DigBaddy]

Bummer. I'm going to have to start learning that OpenRocket software now. I have been putting that off because I build from my head and my hands, not from a computer. I have never modeled parts or weighed them, I just throw stuff together and see what works and what doesn't. I've literally been doing it this way since I was a child, and now I have to change the way I do things.

Look at it from the positive aspects. It's a tool that can allow you to "build" things you can validate before you start down some path that may not work. It can also let you get even more creative with ideas that come to mind.

The software is also a good teacher of many rocketry concepts. You can see the effects of rod angles and wind speed, expected drift once chutes open, flight profiles based on nosecone and fin shapes, and so on. With curiosity, it's a great way to learn things. Once you know those things better, designing and building off the cuff will improve and retain the safety that our hobby typically enjoys.

I love that if I come across some random tube, I can, in minutes, make sim to see what may be possible and how it would fly. That's pretty neat. Another way I enjoy using it is if I give myself criteria/limitations and then make a design; like 29mm motored rocket than can still fly great on some 24/40 reloads using some parts I have on hand. I can tinker with all kinds of things before firing up the bandsaw and drill press.

 

[teepot]

I have tried using a sim program. Can't get past go. I only use ThrustCurve. It's worked well so far.

 

[rharshberger]

Bummer. I'm going to have to start learning that OpenRocket software now. I have been putting that off because I build from my head and my hands, not from a computer. I have never modeled parts or weighed them, I just throw stuff together and see what works and what doesn't. I've literally been doing it this way since I was a child, and now I have to change the way I do things.

Actually learning to use OR will give you a better idea on how shapes and parts affect the rockets flight characteristics, and stability...and less design issues.