Do Rockets Need to be Broken In?

[4kids49]

I have read a number of posts by people that progressively increase the motor thrust for a rocket over a number of launches. I have done this myself. I realize the importance of ground testing ejection charges. Are there any structural reasons to progressively increase thrust before sending a newly built rocket to deep space?


Chris

 

[CarVac]

I have read a number of posts by people that progressively increase the motor thrust for a rocket over a number of launches. I have done this myself. I realize the importance of ground testing ejection charges. Are there any structural reasons to progressively increase thrust before sending a newly built rocket to deep space?


Chris

No. If you are worried at all about structural integrity during boost, it will be strongest during its first flight.

 

[4kids49]

No. If you are worried at all about structural integrity during boost, it will be strongest during its first flight.

Thanks CarVac. That was what I would have guessed. I can't get to many launches so won't have time to baby my next build.

 

[neond7]

I know I work up to bigger motors so I have a chance to verify the rocket is stable and behaves nicely before giving it a big ride. One of my LOC IV clones is a bit squirrely due to a slightly off center fin - I limit it to an H242 motor so I don't have to chase it as far if it heads off to Oz.

In the case of my Big Nuke 3E, I started with two flights on a K550. It was rock stable, so I kicked it up a notch and ordered a K700. I'm looking forward to seeing that one. After that, I might try some CTI 54mm 6XL motors such as the L1030 red lightning.

So, to answer your question, progressively increasing the impulse of the motor builds confidence in the rocket. If you start with the biggest motor you can fit in it, and it shreds, you never knew where the breakoff point was on its capabilities.

.

 

[Coop]

Not so much as broken in as to verify that it behaves as anticipated and no modifications/revisions are necessary to safely fly the desired motors.


Later!

--Coop

 

[4kids49]

Thanks Coop and Sky Pirate. I am building a Mariah 38. I have a number of inputs from various fliers for this kit. I probably should check to see if it flies straight on a lower motor to make sure that I built it well. This will go high and fast. If the trajectory is off, it could be a long walk to recover. So far I have had good success sending up a conservative first flight on a new rocket, and then letting it rip. I should probably stick with that.

Chris

 

[cbrarick]

Spanked my Gizmo on a K2045 for it's first flight. Everyone thought it was crazy but it landed about 200 feet from the pad!

Everyone has their own style.

 

[BEAR]

I use smaller motors on complicated high power rockets on the first flights. This is done so the rocket will be lower in altitude and I can then observe everything going on, ejection charges, deployment, were the charges powerful enough, how did the chute open, etc. If it all works at 1000 to 2000 feet, then it should work at 5,000, 10,000 or more feet, when I cannot see it.

 

[EeebeeE]

If I build a rocket that I think can break Mach One...why wait?

 

[JPVegh]

Yes, I break mine in by loading the biggest possible motor that will fit and launching it in a 19mph. If I get it back I consider it broke in. JK:wink:

 

[cwbullet]

Bigger is better. Right?

 

[4kids49]

Thanks for the tips everyone. Good stuff to know.

Chris

 

[Issus]

Yes, I break mine in by loading the biggest possible motor that will fit and launching it in a 19mph. If I get it back I consider it broke in. JK:wink:

Sounds like how i break my rockets in. No point designing a rocket for a motor/case size and then giving it something else! The only reason to "go small" is to stay within a waiver (and even then you should probably just leave it at home)!

 

[Threemorewishes]

I usually put the most total Ns motor that fits first, then the highest average impulse motor. If it survives those two flights then its usually good to go for all the rest.

 

[gldknght]

I have read a number of posts by people that progressively increase the motor thrust for a rocket over a number of launches. I have done this myself. I realize the importance of ground testing ejection charges. Are there any structural reasons to progressively increase thrust before sending a newly built rocket to deep space?


Chris

I'm probably going to fly my level 3 rocket on a K or an L motor before stuffing my M motor in it for my cert flight. Why? Because I can make sure the rocket flies well and all the electronics work before a stuff the rocket with a $370 motor case and a $270 reload. If something doesn't go right with a 54 mm motor, I can afford to try again as soon as I can get a reload. If something doesn't go right with the M, I gotta wait a year, due to budget constraints.

 

[4kids49]

I'm probably going to fly my level 3 rocket on a K or an L motor before stuffing my M motor in it for my cert flight. Why? Because I can make sure the rocket flies well and all the electronics work before a stuff the rocket with a $370 motor case and a $270 reload. If something doesn't go right with a 54 mm motor, I can afford to try again as soon as I can get a reload. If something doesn't go right with the M, I gotta wait a year, due to budget constraints.

Thanks. I could see that for an L3 flight. I have even been ultra conservative on my L1 and L2 cert flights. I am not really that conservative. After my L1 on an H125 or something, I reloaded on an I223 and did dual deploy. My third hpr flight was my L2 cert on a J330, reloaded and did a dual deploy on a K454. My fifth hpr flight was an L935 and broke mach 1 and went to nearly 8000 ft. I am probably most worried about recovering my Mariah 38. I would agree with Bears comments, but an H100 will probably go over 4000 ft. I am not going to stick a G in it. I will probably put in a low H and make sure everything, tracking, ejection, etc. work well. I will probably use that to also evaluate the launch rail straightness. I saw a rail that was slightly off and sent me for two long walks, as well as others. By chance I took a different pad, and a K750 flight landed a couple of hundred feet from the pad. Whoa CBrarick. You da man! This has been interesting reading. I number of people have told me to break in the rocket which does not make sense to me. I do see a number of advantages of taking a test flight. Honestly, my fins are on as straight as I will ever be able to put them on. I built it well, but stuff happens during launches. Thanks for the tips.

Chris

 

[BEAR]

4kids49, I like how you are doing it. I am ready to fly my L3, which is an Intimidator 4. I am going to fly it on a "J" which should keep it around 2500 feet. I can fly it on a "K", but RockSim reports the flight to be around 8000'. I do not know if I can visually track it at that height to watch deployment very closely, at least not as closely as 2500'. When I fly it on the "M", it will be two feet longer because the motor is 6' long. The "M" will be a RATTWorks M-900, burning for 12 seconds, and RockSims out to 17,400'. I expect it will be out of sight during that flight. Therefore, I test fly to see if the electronics work as advertised, within visual parameters. (Side note: How many can fly an "M" for less than a $100 a shot? That is one of my reasons for a hybrid.)

 

[4kids49]

4kids49, I like how you are doing it. I am ready to fly my L3, which is an Intimidator 4. I am going to fly it on a "J" which should keep it around 2500 feet. I can fly it on a "K", but RockSim reports the flight to be around 8000'. I do not know if I can visually track it at that height to watch deployment very closely, at least not as closely as 2500'. When I fly it on the "M", it will be two feet longer because the motor is 6' long. The "M" will be a RATTWorks M-900, burning for 12 seconds, and RockSims out to 17,400'. I expect it will be out of sight during that flight. Therefore, I test fly to see if the electronics work as advertised, within visual parameters. (Side note: How many can fly an "M" for less than a $100 a shot? That is one of my reasons for a hybrid.)

Thanks Bear. You should be able to see your rocket at 2500 ft. Binoculars help me with stuff at that height or below. I am blind as a bat. Binocs. have not helped at high shots for me. It is a little hard to follow up, but you can see it after the drogue comes out and the binocs. can help you see the main come out really well. At least you have a chance that there will be some people in the crowd who can see where your rocket is. Best of luck with your L3.

Chris

 

[BEAR]

Thanks Chris. I appreciate your comments. I believe I meant that at 2500', I can observe everything from the ground, I can see how the chute(s) deploy, the ejection charges at work, etc. With these observations, I can then predict how it will perform at higher altitudes. I do not expect to see it at 8000' or at 17,000'. I will be relying on the trackers. I should see the deployment at 1000', where the primary altimeter is programmed to deploy the main, and at 750', when the back-up fires, then I should certainly hear and see the deployment. To see it at 2500' is the reason I would test fly before the certification flight takes place. It is not a break in flight, it is a test flight. Unless you have something really unusual, you do not need to break anything in. That takes place on diesels and other internal combustion engines (ICE) where you have bearings, rings, valves, etc, that need a moderated and stepped break in period. Or at least that is the way it used to be, but say on helicopter turbines, we had a dyno test stand for testing for pressures, leakage around seal, and look for any other issues before it was placed back on the helicopter. It was brief though, because those engines only had a certain number of hours life span before it was rebuilt, so it was tested to see if it worked, then shut down and those minutes or hours were added to the log. That is not necessary on a rocket. I hope I am making sense here. BEAR