Rocket question (STEM Question)

I went today and watched my daughter's class fire model rockets. Wish we did that as a class when i was in 5th grade! They worked in groups of 3 to build. Her group was the first to launch, she was chaser. It went with no hitch, 500 ft, streamers popped, and a feather soft touchdown.

VERY PROUD DAD!

She now wants to build one from scratch and launch it with me.

VERY HAPPY DAD!

So, my question is: can anybody give me a formula to calculate streamer size versus rocket weight so we can get a safe recovery?

And not to be a jerk, can you give me an explanation an 11 year old can understand so I can explain why it works?

I usually talk over her head when it comes to what I do...RF Engineering and Network Engineering...but she is super smart ( Not bragging ) and i want to keep her engaged in STEM knowledge cause I know she can do it if she has the desire.

Thanks ya'll!

a reply to: theatreboy

Wow, I haven't thought of model rocketry for a long while. I'm glad they are enjoying it so much, my friend.

My friends and I were RABIDLY into Estes model rockets in the 70's, and it's a fantastic hobby for ANY kid!

I'm not really sure about streamer size, though. Back then we avoided streamer recovery like the plague, and almost always flew rockets with chute recovery. Even so, chutes have their own inherent problems, especially if they aren't perfectly packed.

I pretty much always assumed that streamer recovery was really only practical for small and very lightweight models.

I'll poke around and see what I can find on it. I've seen formulas for chute size, according to weight, so it's most likely out there somewhere.

Thanks though, for the OP. It brought back some great memories, and it's really nice to see that kids nowadays still get a thrill out of it, as I did. I hope they have lots of fun!

If you don't mind me asking, how old are your girls, or what grade?

Oh, I completely missed the "11 year old" sentence, haha. Sorry 'bout that.

Are you looking to explain how rockets work, or a simple explanation for why streamer recovery works?

Or both?

Oh, S+F, too, my friend.

a reply to: theatreboy

Forget the streamer and go to Walmart and pay $10 for a toy parachute. It is 12" in diameter and will safely lower up to a pound of rocket. There are too many variables to figure the correct surface area for a streamer, like rocket weight, streamer fabric porosity, etc.

a reply to: theatreboy
Streamers not recommended for rockets over 30 grams.
It is all right here for you.
Chart is on page 3.
Have fun! apogeerockets.com...

a reply to: F4guy

Streamers are nice when you don't have a huge LZ. They are also a bit more reliable.

I'd recommend the largest streamer you can loosely pack into the rocket.

We used to use streamers instead of chutes because we used heavier rockets (more altitude) and had a relatively small recovery area. The streamer will typically fall faster (closer to launch site). The downside here is ... The rocket typically falls faster. Depending on your recovery area (or how fragile your rocket), it may not be ideal.

You could, in theory, get just as much retardation from a streamer as a chute. You'd just need a lot more streamer. There is no size/weight limit for streamers. It just needs more area than a chute.

Crepe paper is cheap and makes a great streamer (pleated, more drag). Just powder them with talc or baby powder to help them deploy. Mylar streamers and caution tape also work and are easy to come by.

10:1 is generally considered the best L/W ratio.

There is no real precise way to measure the requirement, because each type of rocket has it's own coefficient of drag on recovery, and the shape of the streamer and material used also have a large effect. We did a lot of trial and error.


Here's someone with a little more confidence: streamer calc.

Honestly, it may be a fun project for you both to start with a stock rocket kit that comes with a streamer, and then experiment with different materials and sizes/shapes and have her measure the difference it makes (time the decent). That's basically what we did.


ETA: As for why it works, it's just drag. Have her run or ride a bike with a bed sheet behind her haha

This brought up a recollection.

A rather nutty hang glider pilot buddy once had a "great" idea. He mounted a couple of Estes rockets on the corners of his control bar. Theory being that he could fire them and the smoke trail would indicate a thermal if the rocket passed through it. Pretty good idea. On the surface.

He used his rig once and it was a glorious sight. Thing is, the pilot is quite close to the corners of his control bar. Bob didn't do it but the once.

a reply to: RadioRobert

Easier way to explain the drag (and safer). Get her to put her hand outside the moving car (just hand, I don't want to be responsible to any loss of limbs here). Get her first to have it flat like a aircraft wing. Then get her to turn her hand up like a wall.
She will feel the drag then! And no sheet in a bike chain!

a reply to: Qumulys

And you can then seque into lift, by tilting the hand in the airflow.

I used that with my student hang glider pilots.

originally posted by: theatreboy
I went today and watched my daughter's class fire model rockets. Wish we did that as a class when i was in 5th grade! They worked in groups of 3 to build. Her group was the first to launch, she was chaser. It went with no hitch, 500 ft, streamers popped, and a feather soft touchdown.

VERY PROUD DAD!

She now wants to build one from scratch and launch it with me.

VERY HAPPY DAD!

So, my question is: can anybody give me a formula to calculate streamer size versus rocket weight so we can get a safe recovery?

And not to be a jerk, can you give me an explanation an 11 year old can understand so I can explain why it works?

I usually talk over her head when it comes to what I do...RF Engineering and Network Engineering...but she is super smart ( Not bragging ) and i want to keep her engaged in STEM knowledge cause I know she can do it if she has the desire.

Thanks ya'll!

This could be a teachable moment. The natural thing would be to introduce her to Newton's laws of motion and show how they operate in the case of aerodynamic drag. What is her highest level of mathematics education? That would determine what approach you could take. If she's not ready for a purely mathematical explanation, it can be done qualitatively, and the math can be added later, when she is ready.

Thanks! Great replies, suggestions and stories.

Watching her brought back memories for sure. My cousin and i wondered what would happen if we just fired an engine. In the city. I kid you not, the engine went in my neighbors open window and out her other window. We never tried again.