Can you have Too Much Thrust?

[les]

What happens if you use a motor with too much thrust?
Or is that even possible?

Some basic observations:

1) The motor must obviously fit. You can't jam a 54mm motor into an 18mm motor tube.
2) Must consider the bigger motor weighs more, so nose weight would be required to maintain stability
3) Consider the material strength of the rocket components - avoid shredding the fins or buckling the body tube.
4) Ensure the motor in the rocket does not "bust the waiver" for the field (and lands within the specified area)

What are other considerations to be pondered?

 

[waltr]

You listed the ones I would consider.

Another is when Mach 1 and over speeds there is aerodynamic heating, addition stresses and CP shift.

 

[David Schwantz]

Best is when the rocket never leaves the pad, but the motor does!!

 

[DabCat]

one main thing I can think of is making sure that your motor stop or motor tube or centering rings can handle the thrust. This is usually solved anyways by the thrust ring on the motors.

Another would be the time to apogee exceeding the built in motor delay. However, this is easily solved in high power rockets by electronic deployment.

This is more altitude based, but another thing to consider is what type of deployment you are using. If you are popping your main at apogee, you might want to keep your altitude down. However, this can be solved by using a chute release.

 

[Steve Shannon]

The only way to have a motor that has too much thrust is if you haven’t built a rocket capable of withstanding the thrust of the motor you choose to fly.

 

[rocket_troy]

It's probably worth verifying the OP (les) is specifically referring to thrust and not total impulse? It's not completely clear reading the pointed observations?

TP

 

[lakeroadster]

If the rated thrust is above your qualification level, then you have too much thrust.

Did I just write that

 

[Steve Shannon]

If the rated thrust is above your qualification level, then you have too much thrust.

Did I just write that

Certification is not related to thrust. It’s related to impulse.

 

[cerving]

You can't have too much thrust, but you can have too little strength...

 

[Cape Byron]

My partner told me under no circumstances am I to post to this thread.




Oops.

 

[AllDigital]

Well I think we are going to find out… SpaceX just mounted Booster 7 with 33 Raptor 2’s, capable of 16.8 million pounds of thrust. As a comparison, the Apollo Saturn V first stage had 7.5 million pounds of thrust.

 

[David Schwantz]

Yes, but the Saturn V did it with only 5 engines.

 

[dhbarr]

1) The motor must obviously fit. You can't jam a 54mm motor into an 18mm motor tube.

Motors can safely hang out the back as long as they don't move the CG too far aft.

2) Must consider the bigger motor weighs more, so nose weight would be required to maintain stability

After a motor has more than half its mass above CG it does its own nose weighting.

 

[lakeroadster]

Certification is not related to thrust. It’s related to impulse.

 

[Alan15578]

Certification is not related to thrust. It’s related to impulse.

Sadly, we can not legally fly a motor with more than 80N average thrust without HPR certification.

 

[OzHybrid]

What happens if you use a motor with too much thrust?
Or is that even possible?

Some basic observations:

1) The motor must obviously fit. You can't jam a 54mm motor into an 18mm motor tube.
2) Must consider the bigger motor weighs more, so nose weight would be required to maintain stability
3) Consider the material strength of the rocket components - avoid shredding the fins or buckling the body tube.
4) Ensure the motor in the rocket does not "bust the waiver" for the field (and lands within the specified area)

What are other considerations to be pondered?

Ha Ha you're only talking about trying to jam a 54mm in an 18 mount.. Kids stuff.......

 

[3stoogesrocketry]

Certification is not related to thrust. It’s related to impulse.

AT G75 in a 29/180 case is not HP at 136ns.
A CTI G100 in a 29/3 grain case is a " high power motor " though . Even at 98 ns. Less total impulse , more thrust. Cert level 1 "required" to fly.

 

[Steve Shannon]

Sadly, we can not legally fly a motor with more than 80N average thrust without HPR certification.

AT G75 in a 29/180 case is not HP at 136ns.
A CTI G100 in a 29/3 grain case is a " high power motor " though . Even at 98 ns. Less total impulse , more thrust. Cert level 1 "required" to fly.

You’re both absolutely correct. My pedantic reply to Lakeroadster was overly simplistic. There is a set of rocket motors that are considered “high power” and therefore limited to purchase, possession, and use by certified users, even though their impulse level is less than an H. However, those motors may not be used to certify.

 

[lakeroadster]

You’re both absolutely correct. My pedantic reply to Lakeroadster was overly simplistic. There is a set of rocket motors that are considered “high power” and therefore limited to purchase, possession, and use by certified users, even though their impulse level is less than an H. However, those motors may not be used to certify.

"The Pedant" by caricaturist Thomas Rowlandson

 

[AfterBurners]

What happens if you use a motor with too much thrust?
Or is that even possible?

Some basic observations:

1) The motor must obviously fit. You can't jam a 54mm motor into an 18mm motor tube.
2) Must consider the bigger motor weighs more, so nose weight would be required to maintain stability
3) Consider the material strength of the rocket components - avoid shredding the fins or buckling the body tube.
4) Ensure the motor in the rocket does not "bust the waiver" for the field (and lands within the specified area)

What are other considerations to be pondered?

Can you have too much money?

 

[cbrarick]

Jumbo Darkstar, O9800, held together. Not enough thrust

just say'n

 

[Conway Stevens]

What happens if you use a motor with too much thrust?
Or is that even possible?

Some basic observations:

1) The motor must obviously fit. You can't jam a 54mm motor into an 18mm motor tube.
2) Must consider the bigger motor weighs more, so nose weight would be required to maintain stability
3) Consider the material strength of the rocket components - avoid shredding the fins or buckling the body tube.
4) Ensure the motor in the rocket does not "bust the waiver" for the field (and lands within the specified area)

What are other considerations to be pondered?

There is NO such thing as to much thrust!!
1) 54mm in a 18mm tube? Begginer!! Hold my beer and watch this...

2) If the entire rocket length is Motor no need for nose weight!. But seriously....

In most cases adding a "bigger" motor isnt going to cause the Cg to CP ratio to shrink causing loss of stability... if your Motor mount is a 54mm motor and you had a 12 inch long motor in it and you then put a 28 inch long motor the majority of the weight of said motor is already shifting further forward to the top of the rocket. This weight further forward offsets the the weight at the rear. Only if you Hung the motor out the rear of the rocket would this greatly change.

3) If your shredding then its not to much thrust. Its called not built strong enough.

4) big thrust isnt what breaks a waiver. You could have a very LOW thrust motor. Look at the new Aerotech end burner motors. Low thrust long burn. Were seeing H motors now hit 15,000 ft agl. Its not about huge thrust. You could have a really light rocket huge thrust motor not go very high as its not optimal mass. Goes really fast. Think about shooting a great big feather out of a sling shot pulled back really hard. It may go fast. But not go far. Same thing with big thrust really heavy at the minimum of thrust to weight ratio.

But in my opinion. No you cant have to much.

 

[roytyson]

 

[Alan15578]

I vaguely remember stories of an olive picker motor that would jerk the tree, releasing the olives for harvest.

As a more rocketry related motor, it would be nice to have a few high thrust motors with optimal nozzles having an exit diameter the same as the motor diameter.

 

[Back_at_it]

I don't think you can have too much thrust but you can have too little strength.

Beyond what has already been listed, Centering rings need to be beefed up. An F44 on a stock big daddy that had some miles on it made for an entertaining launch some years ago. The stock paper rings gave up and the motor exited the rocket and kept going. Rocket recovered about 3ft from the pad. Motor was never seen again.

Interestingly the glue joins did not fail. The paper rings were ripped. These days, anything that might fly on an E or better gets a plywood upper ring.

 

[afadeev]

Say "yes" to More Thrust (almost always):



https://www.amazon.com/Enough-Thrust-Pigs-Just-Shirt/dp/B07NVW8RQH

 

[Joekeyo]

Say "yes" to More Thrust (almost always):

View attachment 528326

https://www.amazon.com/Enough-Thrust-Pigs-Just-Shirt/dp/B07NVW8RQH

View attachment 528329


View attachment 528328

JIS LORD? Oh lord!

 

[AllDigital]

On Saturday, I had a motor over-pressurize right after launch. It was half a second into a four second burn when it decided to expend all 8000 Ns. in a few milliseconds -- creating a lot of thrust. The nozzle and snap ring blew out the back and the motor drove forward through the motor stop, through the avBay, and obliterated the vehicle into 100 pieces -- it also pegged my 200G accelerometer. My guess is the motor was momentarily going mach 15. As it turns out, sometimes you can have too much thrust.

 

[kennethgwebb63]

OK, your reply beats the heck out of mine. I was just going to say a Apogee Aspire can pull 20 Gs on a 25 Newton engine and go to about 3000 feet, but more than 200 Gs, isn't that plaid and ludicrous speed?