Streamer Sizing

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gna

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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

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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

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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

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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

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

BEC

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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

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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

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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

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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.
 

rklapp

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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.

 
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