# Need a drogue with GPS?

### Help Support The Rocketry Forum:

#### timothyterpsalot

##### Well-Known Member
Joined
May 29, 2009
Messages
84
Reaction score
0
Noobie here with a question. I'm just thinking ahead and want to learn more about this. Do fliers often not use a drogue when using a GPS? Would it make sense not to if the rocket is going to around 20,000 ft. or less?

#### cjl

##### Well-Known Member
Joined
Jan 18, 2009
Messages
12,549
Reaction score
5
I don't see why the use of a GPS and the use of a drogue are related. I use a drogue depending on the weight and drag of the rocket (I have some that would not work well at all without a drogue, and some that work fine drogueless), and I use a GPS depending on the altitude the rocket is expected to attain.

#### timothyterpsalot

##### Well-Known Member
Joined
May 29, 2009
Messages
84
Reaction score
0
What I meant was, if using a GPS, would dual deploy be necessary?

#### cjl

##### Well-Known Member
Joined
Jan 18, 2009
Messages
12,549
Reaction score
5
Dual deployment? If you're going to 20kft without dual deploy, even with a GPS, that's a heck of a risk. I would almost always do dual deployment for a rocket going high enough to need GPS (unless you enjoy 10 mile hikes around your launch site).

#### timothyterpsalot

##### Well-Known Member
Joined
May 29, 2009
Messages
84
Reaction score
0
I was wondering becuase rocksim says that a rocket going to 15,000 ft. W/O DD then falling at 22 fps in 14mph winds will land 1.7 mi from the launch site. That doesn't seem too bad, and if launching under more calm conditions, I don't see the need for DD.

#### cjl

##### Well-Known Member
Joined
Jan 18, 2009
Messages
12,549
Reaction score
5
That's incorrect, first of all - it would land 2.65 miles away from the point of deployment. Second, that's assuming equal wind at all altitudes - wind is often higher at higher altitude. Also, having hiked after many rockets, I wouldn't really want to hike 1.7 miles with a 30lb rocket if I didn't have to. I've flown DD rockets to 12k feet that landed less than half a mile away.

#### JDcluster

##### Well-Known Member
Joined
Feb 23, 2009
Messages
5,371
Reaction score
92
Location
New Jersey
Buy their more expensive version ( https://www.apogeerockets.com/RS-PRO.asp ) & see what that says about popping the chute at 20k & see how far it lands....

JD

I was wondering becuase rocksim says that a rocket going to 15,000 ft. W/O DD then falling at 22 fps in 14mph winds will land 1.7 mi from the launch site. That doesn't seem too bad, and if launching under more calm conditions, I don't see the need for DD.

#### dlb

##### Sky Pyrate...
Joined
Jan 24, 2009
Messages
1,264
Reaction score
111
drogue at 20K in 14 mph wind = longggggggg walk!

#### Chrisn

##### Well-Known Member
Joined
Apr 10, 2009
Messages
1,506
Reaction score
0
There isnt going to be a drouge, its the main that will be deployed at apogee. Get your passport ready.

#### dlb

##### Sky Pyrate...
Joined
Jan 24, 2009
Messages
1,264
Reaction score
111
There isnt going to be a drouge, its the main that will be deployed at apogee. Get your passport ready.
:jaw:

can you say "RIP" :confused2:

TRF Supporter
Joined
Jan 15, 2009
Messages
2,390
Reaction score
85

#### ben_ullman

##### Well-Known Member
Joined
Jan 18, 2009
Messages
1,523
Reaction score
0
The standard (i.e. cheaper) version of RockSim will also tell you how far the rocket lands from the pad.
but its not as accurate. Hes saying get RS PRO and see what it has to say.

Ben

#### WillMarchant

##### Well-Known Member
TRF Supporter
Joined
Jan 15, 2009
Messages
2,390
Reaction score
85
but its not as accurate. Hes saying get RS PRO and see what it has to say.

Ben
$1000.00 is a lot of money to spend on something that probably won't give you an accurate estimate unless you feed it winds aloft data. This thread seems to be about "back of the envelope." #### falingtrea ##### Well-Known Member Joined Jan 19, 2009 Messages 798 Reaction score 1 I think there are two main questions to ask when deciding to use dual deploy: How far do you want to walk to retrieve a rocket? If 1.7 or more miles is an acceptable walk for you. That much of a walk for me and I would be like :hot: How much range area do you have for retrieval? In the desert or farmland you probably have miles of space, but some places may have retrieval space limits. I don't think locator systems, such as GPS or radio direction finding, should be the driving factor for whether to use dual deploy or not. But having a locator system would improve the chances of finding the rocket after it drifts for many miles, if you don't use dual deploy. #### talkin Monkey ##### Well-Known Member Joined Jan 18, 2009 Messages 481 Reaction score 0 THAT high!...Yes, dual deploy would be ummmm....sensible. GPS/Tracking, pretty obvious logic considering all the variables. Much cheaper than a passport and guide :2: #### JDcluster ##### Well-Known Member Joined Feb 23, 2009 Messages 5,371 Reaction score 92 Location New Jersey Wind speeds above 3k are going to change dramatically & can be blowing in opposite directions. I've gone to almost 12k & had to walk ( actually drive to the other side of the field via local roads) almost 2 miles where the winds were near 0 mph on the ground. Even with the best conditions, I highly doubt you really be able to pop the chute at 20k & get to land within a 2 mile radius. JD #### JDcluster ##### Well-Known Member Joined Feb 23, 2009 Messages 5,371 Reaction score 92 Location New Jersey I was using RS Pro as an example that RS is just scratching the surface when you try to figure out landing zone guesstimates & you really need more data. Also at 20k you might have trouble by "just popping the chute" by any means. Have you ever flown a rocket over 5,000ft? JD #### bobkrech ##### Well-Known Member Joined Jan 20, 2009 Messages 8,353 Reaction score 35 Noobie here with a question. I'm just thinking ahead and want to learn more about this. Do fliers often not use a drogue when using a GPS? Would it make sense not to if the rocket is going to around 20,000 ft. or less? Tim The recommended descent rate under a main parachute is ~15 fps. A 10 mph wind will move your rocket sideways ~15 fps. If you reached 20 kft and popped a main under such conditions, you could have a 4 mile recovery trek, and that might be conservative since the upper level winds are usually stronger and may well come from a totally different direction than at ground level. Splitting the rocket or deploying a drogue at apogee and deploying a main at 300' will likely reduce the walk by a factor of 4. To launch a rocket that gets to 20,000 you need to be L3 high power certified, and during the certification process you will need to learn all about this sort of stuff. Go find you local rocket club and attend some launches and talk to the folks. You can find out where they are at https://www.nar.org and https://www.tripoli.org Also pick up and read the following two books which will explain most of what you need to know. Handbook of Model Rocketry 7th Edition 2004. By the late G. Harry Stine and Bill Stine. Over 350 pages covering all aspects of model rocketry. If you need to find an answer to your rocketry questions, start here! This volume belongs in the library of every serious rocketeer. The official manual of the NAR. Cover price$22.95

Modern High Power Rocketry-Second Edition
By Mark Canepa. This Second Edition of Modern High-Power Rocketry contains more than 800 black-and-white photographs and illustrations specifically created to introduce the model rocket enthusiast to the exciting world of high-power rocketry. Completely rewritten, photographed, and designed, this book provides tips and simple advice on motor retention, ejection charges, the high-power launch and building your first Level One, Level Two and Level Three rockets.

$17.00 and$28.00 respectively from NARTS https://blastzone.com/nar/narts/store.asp?groupid=1080035015601

Bob

#### cjl

##### Well-Known Member
Joined
Jan 18, 2009
Messages
12,549
Reaction score
5
One note Bob: I've seen an I motor launched to 16k, and there have been K motors launched to near 30k, so you definitely don't need an L3 to get to 20k feet. Other than that though, I fully agree with your post.

#### troj

##### Wielder Of the Skillet Of Harsh Discipline, Potent
Joined
Jan 19, 2009
Messages
14,324
Reaction score
239
The recommended descent rate under a main parachute is ~15 fps. A 10 mph wind will move your rocket sideways ~15 fps. If you reached 20 kft and popped a main under such conditions, you could have a 4 mile recovery trek, and that might be conservative since the upper level winds are usually stronger and may well come from a totally different direction than at ground level. Splitting the rocket or deploying a drogue at apogee and deploying a main at 300' will likely reduce the walk by a factor of 4.
Agreed! Especially the wind direction bit -- we've had ground winds coming from the exact opposite direction of upper level winds.

To launch a rocket that gets to 20,000 you need to be L3 high power certified, and during the certification process you will need to learn all about this sort of stuff.
L2 rockets can hit 20K AGL and higher; most do not, but it can (and does) happen.

Go find you local rocket club and attend some launches and talk to the folks. You can find out where they are at https://www.nar.org and https://www.tripoli.org
That, right there, in my opinion is the best advice anyone can get, or give. Local, experienced people can teach you a LOT more than a book.

-Kevin

#### ragid

##### Active Member
Joined
Jan 27, 2009
Messages
27
Reaction score
0
20,000 feet is pretty high for popping the main. However there are some areas where is is doable (with a long walk or drive). The Black Rock desert is one of them. The Salt Flats is another. I have flown to around 10,000 twice without a drogue at the Salt Flats. One time the rocket landed 500 feet away. The other time it was 3.5 miles. Luckily on the flats you just head out in the direction the rocket went and you eventually find it. Everything shows up well against the white salt, so you can see your rocket a long ways off.

#### timothyterpsalot

##### Well-Known Member
Joined
May 29, 2009
Messages
84
Reaction score
0
I was using RS Pro as an example that RS is just scratching the surface when you try to figure out landing zone guesstimates & you really need more data.
Also at 20k you might have trouble by "just popping the chute" by any means.

JD
JD, what did you mean at 20k you might have trouble popping the chute? Is that the point where air pressure starts becoming an issue?

Also, I live in Kansas City and the closest clubs that seem to be active is Kloudbusters and the Nebraska group; both are 3 1/2 hours away. There is a Kansas City group but it doesn't seem to be very active. That's why I prefer to ask most of my questions on here as I can't make it down there for every launch.
Like I said, I'm just wanting to learn about all this.

#### Len_Lekx

##### Active Member
Joined
Jan 19, 2009
Messages
42
Reaction score
0
I think there are two main questions to ask when deciding to use dual deploy:

How far do you want to walk to retrieve a rocket? If 1.7 or more miles is an acceptable walk for you. That much of a walk for me and I would be like :hot:

How much range area do you have for retrieval? In the desert or farmland you probably have miles of space, but some places may have retrieval space limits.
There's also the question of who owns the neighbouring properties, and how amenable they are to having rockets fall on their lands. Some people will be okay with it, while others are not so accepting.

It's always a good idea to design the rocket to fall *within* the limits of your range - whatever those limits may be. For high-altitude flights, that typically means dual-deployment.

#### troj

##### Wielder Of the Skillet Of Harsh Discipline, Potent
Joined
Jan 19, 2009
Messages
14,324
Reaction score
239
It's always a good idea to design the rocket to fall *within* the limits of your range - whatever those limits may be. For high-altitude flights, that typically means dual-deployment.
It's a requirement to keep them within the limits of your waiver....

-Kevin
{"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.37159299850463867, "perplexity": 3638.8202118306144}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": false}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2021-10/segments/1614178376467.86/warc/CC-MAIN-20210307105633-20210307135633-00381.warc.gz"}