30,197' 75mm Minimum Diameter-Camarillo High School

[edwinshap1]

Last time the chute was packed improperly which allowed it to open at apogee, which in the low winds was fine.

Yesterday, the winds were close to 20 mph, so we packed more tightly. I think separation happened at main deploy.

 

[dixontj93060]

I may be stupid here, but how does the tightness of packing a main chute affect its deployment timing? Was this not a dual deploy rocket with electronics? Are you talking about the time from main separation to when the canopy is fully inflated? This may be delayed be a tighter packing, but you would need to utilize some staging of the shock cord and lines so they break free sequentially (much better to use a d-bag for this).

Last time the chute was packed improperly which allowed it to open at apogee, which in the low winds was fine.

Yesterday, the winds were close to 20 mph, so we packed more tightly. I think separation happened at main deploy.

 

[New Ocean]

It was 750pound test. And we have used it on the previous flight. We cut it shorter this time.

It sliced itself on the lip of the body tube.

Things we learned...

Well 7.5 lbs rocket with 100 G recovery = 750 lbs. I would want 2000 - 4000 lbs from start to end on that recovery system, so 3/8ths kevlar or so. A rocket this fast, on a windy day, can deploy at 50 mph+ and take a real hit. Thanks for pushing the limit so others know where the limit is! Sorry that it cost you the booster. Perhaps someone will find it later and return it?

 

[troj]

I may be stupid here, but how does the tightness of packing a main chute affect its deployment timing? Was this not a dual deploy rocket with electronics? Are you talking about the time from main separation to when the canopy is fully inflated? This may be delayed be a tighter packing, but you would need to utilize some staging of the shock cord and lines so they break free sequentially (much better to use a d-bag for this).

How tight it's packed doesn't affect it. It just affects the volume.

The packing technique (not tightness) will affect the way, and the rate at which a canopy inflates, as well as having impact on the force generated on deployment.

'tis part of why skydivers are so very particular about how their rigs are packed.

-Kevin

 

[dixontj93060]

That is exactly what I thought, thus my confusion with the first post in this page.

How tight it's packed doesn't affect it. It just affects the volume.

The packing technique (not tightness) will affect the way, and the rate at which a canopy inflates, as well as having impact on the force generated on deployment.

'tis part of why skydivers are so very particular about how their rigs are packed.

-Kevin

 

[troj]

That is exactly what I thought, thus my confusion with the first post in this page.

FWIW, I agree with you 100% on the deployment bag thing. A properly used deployment bag is a wonderful thing.

-Kevin

 

[babp1011]

Our GPS gave lock nearly the entire boost phase

What GPS system did you guys use? It's impressive that you held lock for most of the boost phase. Pretty rare in rockets traveling past Mach 1.

 

[bandman444]

What GPS system did you guys use? It's impressive that you held lock for most of the boost phase. Pretty rare in rockets traveling past Mach 1.

Garmin Astro. Amazing piece of work. Couldn't fly high power night flight without it.

It is the only piece of my personal gear in the rocket.



A couple things about the parachute.

First flight we deployed our parachute at apogee and had 100ft of the 750# Kevlar.

Second flight dual deploy worked as it should and apogee separated our two parts which fell together on our shortened Kevlar piece which was 25ft long. At 700 ft we deployed our main via the tender descender which three things caused it to fail.

Added stress from successful DD vs. first flight

Shortened Kevlar not enough spring to distribute forces.

Added nose weight tripling the weight in nose may have been too much force.


30 mph winds didn't helps either.


All in all we should have in my opinion used 3/8-1/2 Kevlar and about 50ft. Of course that is in retrospect and not discussed at the time.


I hope our search party is successful.

Bryce

 

[bandman444]

Perhaps someone will find it later and return it?

the chances are very slim. Unlike the Lucerne lake we normally fly at that has shacks and house around its perimeter. FAR is surrounded by more dry lakes and BLM land. We have a map planned out on where to search and we will hopefully be able to recover the booster to further analyze the problem.

 

[AHansom]

Shortened Kevlar not enough spring to distribute forces.
Bryce

100' is a long harness but even at that length Kevlar don't spring.

 

[bandman444]

100' is a long harness but even at that length Kevlar don't spring.

Correct. Sorry I meant to say something like that a longer length allows the rocket to slow itself down via drag before coming to the end of the line.

A longer cord would have been better than the shorter cord.

 

[tfish]

Tony

 

[Burner]

At least you have the GPS data to help determine the search area. I have found many interesting things wondering around the property...

Was the wind already up earlier in the morning? Or did it get progressively worse throughout the morning?

 

[bandman444]

View attachment 85353

Tony

Yep. I'v done it on most of my rockets, but that would have relieved stress apogee, but we separated after main deployment. I don't think it would have helped this time.

 

[bandman444]

At least you have the GPS data to help determine the search area. I have found many interesting things wondering around the property...

Was the wind already up earlier in the morning? Or did it get progressively worse throughout the morning?

Winds were 15-30 almost all afternoon, and getting worst as the day went on.

If it weren't for the amazing facilities at FAR (Sealed hanger) setup would have sucked a lot more.

 

[mikec]

...but we separated after main deployment.

How do you know this again? I assume you searched upwind from where you found the nose cone. Surprising the body and nose cone would have ended up very far apart if they only separated at main deploy, though I guess with high winds and light chute loading it's plausible. Also surprising that your kevlar would have snapped just from main deployment forces, especially with a tether. I've used 1/8" kevlar and it's pretty robust.

 

[bandman444]

We found the nosecone 2.85 miles from the pad. It is extremely unlikely that a 4 pound nosecone would drift that far without the aide of the booster.

We did of course search upwind from the nose cone site. Because the booster has the parachute if must have drifted pretty far. The terrain of shoulder high brush makes recover very difficult unless you are within feet of them.

We hope to find it next week.

 

[edwinshap1]

I should add to what Bryce said as I was the one complaining on the 6 mile walk we made in recovery.

We found that the kevlar sheared at the edge of upper carbon tube, which would have made the nosecone/payload bay very aerodynamic. While possible, I don't think it would have floated 15000 feet from its apogee point if it were aerodynamically stabilized. The most likely scenario is that at main deployment (which could easily have happened earlier due to the non-ideal wind conditions), the body and payload separated, which would make more sense as the nose was weighted with 2.5 lb of weight for stability. The wind was pointing east south-east, but when we walked, we veered north slightly, so we may have easily missed the rocket.

The wind was between 25 and 30mph with gusts to 35mph during our recovery efforts. By the time we left it was a constant 30mph.

The one thing I can be sure of is that the main did not deploy at apogee. The chute was wrapped extremely tightly in the tender descender. However, with a 36" chute, and a booster mass of 5lb, it could have drifted very far. I still need to do alt sims to figure out how far it actually drifted.

 

[AHansom]

a booster mass of 5lb.

That's impressive with 6LB motor hardware stuffed inside! Im not sure about the high winds theory causing the failure. The rocket will be traveling sideways with the wind during descent and will have a significantly lower apparent wind speed during main deployment Also If the nosecone became separated at apogee in 30 mph wind it could have drifted a couple of miles easily. A 30mph drift for 5min is 2.5 miles.

 

[edwinshap1]

I have to admit I didn't actually measure the mass of the booster myself, I just threw a number in the air. I would leave it for Bryce to answer, but I don't think the transmitter was in the air for 5 minutes. Or at least it didn't feel like 5 minutes.

I don't think the wind speed caused a failure, but it made the search miserable. dust storms, sand blasting, and shoulder high brush in 30 mph winds is not a fun environment to hike in

I'll have to get the actual values from Bryce, but our best bet is to head to where we found the nose and search from there. Otherwise we have no frame of reference. What's worse is that if separation did happen at another time, or if the main deployed earlier than we think, we also have no real frame of reference.

I think they will be heading out to FAR again next weekend, but I will be unable to go, so I'll have to do my best with sims to give them a better jumping point.

 

[AHansom]

We found that the kevlar sheared at the edge of upper carbon tube,
.

any way to tell if it sheared from a sudden shock or if 1/8 was just to thin wore through on the ride down.

 

[mikec]

any way to tell if it sheared from a sudden shock or if 1/8 was just to thin wore through on the ride down.

1/8" is admittedly too thin for this application but it's not that weak -- I used it for a dozen flights on a 3" rocket, drogueless, and it was fine, so I think "wore through" is unlikely.

Depending on the trajectory the rocket could have had a fairly high horizontal velocity at apogee and that could have produced a lot of shock load.

I guess I don't follow where the chute was attached and what you recovered. A 36" chute with 7-8 lbs is going to have a pretty high descent rate though not as high as a bare nose cone clearly.

Probably too late to query for winds aloft from https://rucsoundings.noaa.gov but that might be helpful.

 

[daveyfire]

We hope to find it next week.

Hey if you guys find an unpainted carbon 6" rocket or an 8" glass one painted white (both with P cases in them) out there, lemme know, we've sent lots of search parties out but never found either...

 

[Rocketjunkie]

If the chute was on the booster and it's slower descending than the bare nose cone, it should be downwind of the nose cone.

 

[Nerull]

That's impressive with 6LB motor hardware stuffed inside! Im not sure about the high winds theory causing the failure. The rocket will be traveling sideways with the wind during descent and will have a significantly lower apparent wind speed during main deployment Also If the nosecone became separated at apogee in 30 mph wind it could have drifted a couple of miles easily. A 30mph drift for 5min is 2.5 miles.

Another thing to consider is that 30mph winds on the ground can be 80-100mph winds at 30000ft.

This sounding plot shows ~15kt winds near ground level and 70kt at 300mb (approx 30000ft in the Standard Atmosphere model), and 110kt at approx 35000ft. It is always important in high altitude flights to remember that the atmosphere is not uniform. Wind speeds and directions will change on the way up.


(I should note that this is only an example, and not conditions from this launch)

 

[AHansom]

Not trying to knock what the team has done but how many duel deploy rockets have you successfully flown? Its no secret you went from JR. level 1 and skipped right to flying big rockets and MD M motor rockets. So now we have 2 smallish M motors with 2 less than optimal recovery's. I think you should slow down a little and scale back for some rocket testing. Maybe get your level 2 on a similar size rocket and fly it a bunch to work out, adjust and perfect your recovery's along with everything else you learn just from flying. Then go for the N5800 challange with confidence not just a hope and a prayer

Good luck and I am on your side

Andy

 

[mikec]

Winds aloft data for Edwards AFB, just down the road, during your flight can be found at https://rucsoundings.noaa.gov/plot_...false&startSecs=1338058800&endSecs=1338062400

For example, wind speed at 30 Kfeet was about 75 knots. At least it seems like the direction was fairly constant at all levels.

 

[edwinshap1]

The only time I really looked closely at the actual kevlar was when I was walking back to the truck. It was frayed, but I do not think the CF would have frayed it in the time span of the descent. Also, my values for the booster were a good bit off. Booster weight w/motor case 8lb, and parachute was 58". I just designed and milled the fins, so that's my excuse

Admittedly we did walk in the wrong direction, so there is a chance it is within the area we walked around, though I wouldn't hold my breath too much.

In looking at this image:
LINK

I think that about 2/5 of the way down, the horizontal airspeed slowed, but it is possible that the kevlar did snap at that point. However, from 36500 ft, to get 15000 ft away from the launch point, it would need to be moving pretty quickly horizontally to get that far. I need to get that info, and then I can start figuring it all out.

Also, We had main at apogee last time, and the kevlar sheared this time, both issues that I noted prior to launch, but I did not have the time to fix before launch. I have been a part of this project since the beginning, but for our 4" rocket I will be a part of the design and "checklist" phase from the beginning, so barring issues we cannot actually deal with, we will be very well covered. Also, you don't learn anything from a perfect launch, but you learn everything from a failure. From the last two launches, we learned that we need a well designed and rigid launch tower, we need to pack the chute tightly enough to keep it from opening no matter how fast it's falling, and we need to pre-test the kevlar to make sure we don't have a shearing issue.

I will also be testing a rail attachment system for the 4" rocket that I will need to physically test. I'll have a picture for it soon. I'll update it on my fin attachment thread.

 

[AHansom]

you don't learn anything from a perfect launch, but you learn everything from a failure. .

Absolutely! but this lesson cost the team big bucks. Lost 75mm motor hardware, Raven, backup altimeter, CD3 ejection, time and materials on the booster section. I think you could have learned the same lesson and made adjustments by flying 4 or 5 K motors to 10.000' Also as others have suggested try a deployment bag it contains the main parachute for the long fall until the descender releases it

 

[edwinshap1]

Very true. We'll have to characterize and test our 4" rocket before sending it up. However, it would be a loss to test it and lose everything on a test, before we even got to make the final launch. I'm hoping ground testing of the components and load testing of all the parts will help give us the information we need.

Check out my High Strength Fincan thread for my basic rail design. Also, time to start studying, talk to you all later

Will you be at ROCstock?