Streamer Sizing

[gna]

I'm trying to design a LPR rocket, and I want to use a streamer for recovery, as it may go quite high. What is a good descent speed under a streamer? I've picked some common sizes and materials in OR, and I was surprised at how high some of the speeds were.

 

[BEC]

I just went and looked at some of my FlightSketch logs to see. The typical descent rate for my Checkmate's sustainer is 17 ft/s. This is a mini-motor two stager and the upper stage weighs less than an ounce. For this model, this is a safe descent rate, even when landing on a hard surface.

Sterling Silver data range from 17-22 ft/s (again, a two-stager based on BT-20, but this time using 18mm motors.

My modlerockets.us Nexus, which is BT-50 based, also falls at ~20 ft/s.

My BMS School Rocket seems to come down at ~22 ft/s. That will break a fin (they are balsa) landing on a hard surface.

There are some examples from altimeter data.

(overbuilding is not your friend here)

 

[gna]

I just went and looked at some of my FlightSketch logs to see. The typical descent rate for my Checkmate's sustainer is 17 ft/s. This is a mini-motor two stager and the upper stage weighs less than an ounce. For this model, this is a safe descent rate, even when landing on a hard surface.

Sterling Silver data range from 17-22 ft/s (again, a two-stager based on BT-20, but this time using 18mm motors.

My modlerockets.us Nexus, which is BT-50 based, also falls at ~20 ft/s.

My BMS School Rocket seems to come down at ~22 ft/s. That will break a fin (they are balsa) landing on a hard surface.

There are some examples from altimeter data.

(overbuilding is not your friend here)

Thanks. I was looking at a 2"x20" streamer in OR, and I was getting over 40 ft/s for a BT-50-sized rocket. What size/type streamer were you using for the Nexus?

I built a BMS school rocket but gave it to the club's FITI program, so I have no idea of how it performs. I seem to recall that had a mylar streamer in the kit.

 

[teepot]

A safe descent rate is 15 fps. See how long a streamer you need for that. I have used mylar as a streamer. Something like 6 feet. Rolled it up around a drill bit with my drill. You can get it tight that way. The school rockets I've built I put chutes in.

 

[gna]

I found this Googling around. It seems shorter and wider is better for streamers. I'll go bigger and see what OR says,

 

[BEC]

What size/type streamer were you using for the Nexus?

The modelrockets.us Nexus uses a couple of feet of the wide plastic flagging tape (about 2 inches wide). The Estes models I mentioned (Checkmate, Sterling Silver) use 1 inch flagging tape.

Another streamer model I have is the Sidekick (a two-motor cluster model that looks like siamese twin rockets)—and on its last flight, which landed on a hard surface, both body tubes were damaged above the fins. The only measured descent rate I have on it is less than 10 fps (not that flight). It uses a fairly large mylar streamer in each body tube.

 

[BABAR]

I'm trying to design a LPR rocket, and I want to use a streamer for recovery, as it may go quite high. What is a good descent speed under a streamer? I've picked some common sizes and materials in OR, and I was surprised at how high some of the speeds were.

if you haven’t already committed to a rocket design:

Especially for streamer rockets, fins which do NOT extend below the base of the body tube (and ideally fins where the trail edge sweeps FORWARD) are more durable

the rocket’s first impact with the ground will be the motor casing, which is both harder and more importantly disposable for single use motors, compared with a classic rocket like the Alpha with aft trailing fins. The “price” is that more forward placed or swept fins are SLIGHTLY less efficient, but the difference is small and outside of the competition realm, not significant.

 

[gna]

if you haven’t already committed to a rocket design:

Especially for streamer rockets, fins which do NOT extend below the base of the body tube (and ideally fins where the trail edge sweeps FORWARD) are more durable

the rocket’s first impact with the ground will be the motor casing, which is both harder and more importantly disposable for single use motors, compared with a classic rocket like the Alpha with aft trailing fins. The “price” is that more forward placed or swept fins are SLIGHTLY less efficient, but the difference is small and outside of the competition realm, not significant.

I'm trying to keep the fins forward, and keep the trailing edge forward. Somewhat like BMS school rocket.

I'm starting to suspect a problem in OR, though, because I played around with both Wizard and Alpha designs using a 2x20 nylon streamer, and they both came back with over 40 ft/sec descent speeds.

 

[Dotini]

I'm starting to suspect a problem in OR, though, because I played around with both Wizard and Alpha designs using a 2x20 nylon streamer, and they both came back with over 40 ft/sec descent speeds.

Van Milligan (2008) gives the formula, "at least 8.5 cm^2 (1.3 in^2) of a single sided surface area per gram of returned model mass". Thus, a 16 gram rocket with empty casing of 4.12 grams would get a streamer 4.14 cm x 41.4 cm.

Van Milligan gives the general rule for parachute descent rate to be 3.5 to 4.5 meters per second (11.5 to 14.8 feet per second). I have experimentally obtained 18 feet per second with horizontal spin recovery, which dispenses entirely with parachute and streamer.

I have successfully used a streamer of pleated mylar 6" x 60" to safely return models of over 3 oz to a grassy surface without damage.

 

[DaHabes]

This > https://www.rocketreviews.com/streamer-calculator.html

 

[Ronz Rocketz]

I had several great streamer launches yesterday despite the Q-jet catos. The trick is to get the rocket to land sideways, which might be easier to accomplish in >10mph winds.



The Diamondback has an awesome streamer system with tough fins for hard landings. I added a swivel to the shock cord. The bounce at lift-off was particularly spectacular. The landing for the second launch was less aerodynamic, probably because I added the cam. I wonder if it would be more streamlined if I used the Astrocam instead.

 

[Dotini]

I'm building an under 2 ounces small field BT-50 model to recover on a streamer. I can fit up to a 4" streamer. I have a couple of questions.
1) Is there a performance difference between pleated mylar and thin mil fabric, taking into consideration the small weight addition of the fabric?
2) Which material would be more resilient to ejection charge damage?

 

[PhilC]

My 3d printed BT50 rocket uses a streamer all the time. The streamer is made from offcuts of kite nylon and is about 2 inches side and 6 ft long. It flutters a lot and is really draggy, yet rolls well in a BT50 tube. To overcome scorching I made a simple 3d printed piston.

 

[Alan15578]

I think the old NAR rule was at least 22 square inches of parachute area or 44 square inches of streamer area per ounce.

 

[dhbarr]

External attachment of the streamer where the burnout CG and CP meet is your friend.

 

[DigBaddy]

Good thread. Thanks all for sharing! Thinking of making a two-stage Hi-Flier XL and doing streamer recovery but honestly have not done anything larger than BT-50 stuff with streamers; so new territory. OR was still having it smack the ground at ludicrous speeds with two 6x60" streamers. The calculator linked above, and Tim's formula shows 6x30" should suffice. Seems like reality says this should be easily doable.

 

[Ez2cDave]

I'm trying to design a LPR rocket, and I want to use a streamer for recovery, as it may go quite high. What is a good descent speed under a streamer? I've picked some common sizes and materials in OR, and I was surprised at how high some of the speeds were.

Landing damage is, primarily, a function of descent rate . . . The higher the rate, the greater the damage.

The main advantage of a Streamer over a Parachute is a lower rate of downrange drift, compared to a parachute.

Dave F.

 

[Ronz Rocketz]

Good thread. Thanks all for sharing! Thinking of making a two-stage Hi-Flier XL and doing streamer recovery but honestly have not done anything larger than BT-50 stuff with streamers; so new territory. OR was still having it smack the ground at ludicrous speeds with two 6x60" streamers. The calculator linked above, and Tim's formula shows 6x30" should suffice. Seems like reality says this should be easily doable.

Don't have to worry too much about the booster landing on the ground. The Hi-flier XL probably won't buckle. with a streamer hard landing. The fins would survive better if they were TTW but would need tabs added or rebuilt. The bottoms of the fins can be strengthened with carbon fiber strips.

 

[Ez2cDave]

I'm building an under 2 ounces small field BT-50 model to recover on a streamer. I can fit up to a 4" streamer. I have a couple of questions.
1) Is there a performance difference between pleated mylar and thin mil fabric, taking into consideration the small weight addition of the fabric?
2) Which material would be more resilient to ejection charge damage?

Yes, pleated Mylar has much higher drag than thin fabric, because the hard-creased folds provide much more air resistance. Get the thicker Mylar ( 2 Mil, or thicker )

https://www.rocketreviews.com/tools.html

https://www.rocketreviews.com/streamer-calculator.html

https://www.nar.org/wp-content/uploads/2014/05/Streamer-Duration-Wolf.pdf

https://www.nar.org/wp-content/uploads/2014/05/Streamer-Optimization-Kidwell.pdf

https://www.narhams.org/library/rnd/StreamerDuration.pdf

Dave F.

 

[lakeroadster]

Has anybody ever compared Open Rockets calculated streamer information with the Rocket Reviews? From what I'm seeing there is a huge discrepancy between the two.

Open Rocket

I loaded the example "Simple Model Rocket" and replaced the parachute with a 4" x 40" streamer.​

Ground hit = 39.7 mph​

Rocket Review

I plugged in a 4" wide streamer and used the 2.29 ounce full up weight of the rocket. Rocket Review says a 21.93" streamer is adequate.​

What am I missing?

 

[SolarYellow]

I went down that rabbit hole last August/September. There's a thread or two around here I started on the topic. I am pretty sure I remember OR just treats the whole rocket as a point weight pulling down on the streamer and neglects its drag entirely. As does the calculator at Rocket Reviews. That leads to excessively high descent speed calculations. Another issue is that the literature on the effective CD of streamers varies wildly. I dug up everything I could dig up without yet having spent the money to access the tech archives at NAR, and it was clear that the question was not answerable with confidence given the available information.

I finally decided that the only way to deal with it is to go to the lab: make something that looks kinda like what's already demonstrated to work well, then experiment and measure the effects of changes on any particular rocket design.

 

[lakeroadster]

I went down that rabbit hole last August/September. There's a thread or two around here I started on the topic. I am pretty sure I remember OR just treats the whole rocket as a point weight pulling down on the streamer and neglects its drag entirely. As does the calculator at Rocket Reviews. That leads to excessively high descent speed calculations. Another issue is that the literature on the effective CD of streamers varies wildly. I dug up everything I could dig up without yet having spent the money to access the tech archives at NAR, and it was clear that the question was not answerable with confidence given the available information.

I finally decided that the only way to deal with it is to go to the lab: make something that looks kinda like what's already demonstrated to work well, then experiment and measure the effects of changes on any particular rocket design.

Thanks for the reply. I'll dig into the NAR archives and see what's there.

Update 2023-3-31:

There are a number of articles in regard to streamers on the NAR's Technical Bibliography area. There's a lot of data collection, using various designs and the newest article is dated 2010.

I might have missed it, but I didn't find anything related to calculating the Cd of a streamer.

 

[JoePfeiffer]

OR's default drag coefficient for streamers looks ×really× low to me, but we haven't had a chance to look in to it.