LF: Launch site size and motor size recommendations

[redleder]

In my area it is hard to find a site large enough to launch rockets on anything bigger than B/C anymore. I used to have a great site but it was purchased by the town and turned into a "Park Reserve" which strictly prohibits the use of rocketry. They are concerned it could hurt the "flora and fauna". Anyway, I have found a new location that I would like your thoughts on. Attached is a Google Earth image with measurement pins that are showing me ~1.6M sq. ft., which is approximately 37 acres. Although the area is not perfectly square, if I setup near the center, it would allow for a good size launch area. My question is what would most people here feel safe with launching motor wise or altitude wise that would give me the highest probability for recovery? I have some smaller rockets that OpenRocket say can reach 2000ft and some bigger heavier rockets that show 1000 ft on F motor. I have a 54mm rocket that I would like to launch locally, but not sure I can keep below the ceiling I need for recovery. I haven't modeled it yet, but suspect that it would reach 2500+ ft.

Thanks for the advice,

Jarod

 

[Bat-mite]

Assuming this is all non-HPR, here are the safety code site dimensions tables. The dimension listed is the minimum field dimension, which looks to me like your upper left line. 1000' will get you a G.

However, depending on wind, turf, chute size, etc., it is not always practical to launch to 2000' in a 1000-sq-ft field.

Streamers or chutes? Descent rate? Any Chute Release, dual deploy, or cable cutters?

 

[redleder]

Assuming this is all non-HPR, here are the safety code site dimensions tables. The dimension listed is the minimum field dimension, which looks to me like your upper left line. 1000' will get you a G.

However, depending on wind, turf, chute size, etc., it is not always practical to launch to 2000' in a 1000-sq-ft field.

Streamers or chutes? Descent rate? Any Chute Release, dual deploy, or cable cutters?

It would be all LPR/MPR aside from the possibility of L1 cert testing on an H motor. Not sure this is possible here, but will model it out.

So, I updated the site map and include a circle plus radial line indicating a radial launch zone assuming 0 degree launch angle. We would be using standard parachutes for LPR and MPR and chute release for any rocket with motor larger than F set to 400-500ft for release.

I have approximately 600 linear ft to deal with assuming I am at the center point or ~1200 linear ft from diameter perspective.

 

[Bat-mite]

So here's a trick to help you. Go to this descent rate calculator, put in your various rocket weights and chute sizes, and see how long it takes them to come down. Then multiply that by the wind speed to see how far away it will come down.

Far from perfect due to weathercocking and arching over, but it will give you some idea.

I put in a one-pound rocket with a 36" hex chute and got a descent time of 85 seconds. Assume a 5 mph wind, which equates to about 7.5 fps. If it's moving 7.5 fps laterally for 85 seconds, then it comes down 637.5 feet away. In 10 mph winds, it's coming down 1275 feet away.

Again, not perfect. The rocket will weathercock into the wind, which means during descent, it will pass over the flight line. Maybe it comes down 500 feet away. Or maybe it hits a thermal, or winds aloft are 20 mph. But it's a start.

 

[samb]

Based on the proximity of rocket-eating trees, park structures and parking areas, I don't think the proposed launch site in your first post is practical. Here's my guess at the usable area:

 

[redleder]

Certainly, I was looking at the largest possible perimeter for worst case. And then will pull it back for a more conservative field. I will do some sim work but a good heavy rocket should be safe on a f motor. Assuming low wind conditions. Will test it out on some LPR's first and see what I get. Who knows what kind of wind [emoji100] is lurking above that tree line.


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