Pods on Mega Der Red Max? --- GOT MY LEVEL 1 CERT

Yeah, 3 point landing on the second flight. One of the lower pod cones looked a little out of wack, but not to bad.
We will have to hear from Thirsty about the any repairs needed.

Good to meet you TB

rbelknap said:

Eric - the video is uploading right now. I'll post embed it here once YouTube has finished chewing on it. I should taken a couple of stills to throw into the video too. Maybe if SCrocketfan posts his, I can do a digitally remastered director's cut.

I noticed that Tony congratulated me on the flight, I think that was because I asked him to wait so I could run out and record it. Sometimes he gets confused. 4 hours in the sun as LCO on a couple hundred flights will do that to the best of us. (That's my estimate for the day. Easily could have broken 300 flights if we hadn't had to hold for the C-17 and the Ospreys)

Here's the video, but now for some reason I think I've spelled your name wrong.

[video=youtube_share;1Vfs0MnfxFk]https://youtu.be/1Vfs0MnfxFk[/video]

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Robert, thanks for recording and posting this video! It turned out great! You've got my name spelled correctly, so no worried there.

I won't hold it against Tony for getting mixed up on the names. He does a great job, and so do all of you guys running the launch. It's a really well run, efficient, and fun launch. And you guys manage to get a huge number of rockets in the air, even with so many new kids who have never flown a rocket in their lives. The only improvement I could suggest is that maybe the club could arrange for an acre of padding for the tarmac. You might need a bigger trailer for that.

I was really happy with how the rocket flew. Beforehand, I was a bit nervous about it, because it turned out much heavier than I expectd, so I was concerned about speed off the rail, and because I had altered the CG and CP positions so much with the modifications, I was concerned about stability. But it looked rock-solid stable to me during flight. And it went straight off the rail with no weathercocking whatsoever, as far as I could tell, so I think the speed off the rail was fine too. I think maybe it has a high moment of inertia and is resistant to turning. This was exactly the kind of flight I was hoping for!

Looking at the video, does it look like the rocket is still traveling upward at ejection? It's not going fast, so the delay was probably as good as it could be, but I'd like to know what people think about the exact timing, so maybe I can dial it in for other motors. Was it at apogee or a bit before?

Thanks again for capturing this great video!

SCrocketfan said:

Here's some pics from today's launch. This was the G77R-4 flight, it was an awesome flight and the rocket flew perfect and deployed right at apogee. I didn't get any video, just a few shots from the high speed camera.

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Thanks for posting these photos, SC! Great job! The high speed camera seems like it worked really well.

Your G Force was the next rocket to go after mine --- in fact, I think mine hadn't landed yet. And I also think you were flying on exactly the same motor, G77-4R. You rocket put in a great flight and it definitely made for a great contrast in how different kinds of rockets fly --- I think yours went several hundred feet higher on the same motor.

It was great meeting you! You've got a very cool and unique fleet of rockets. I think the ones I saw fly were the G Force (flew really well, and was probably the most "standard" rocket you flew, I think), the two-stage mega mosquito (worked great, and was a first flight, correct?), and Caffeinator (very entertaining!). Did you also fly a saucer? I liked the variety.

Thanks again for the photos and also for the advice you gave in several of the threads during the building of this rocket! Onward to TCC's October Skies! Hopefully I'll see you there!

ChrisAttebery said:

Here's the video I captured. The MDRMWP flew great.

[YOUTUBE]_1rwkkXWERQ[/YOUTUBE]


Sent from my iPhone using Rocketry Forum

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Thanks for posting this video, Chris! This is the second flight, which was on a G78-4G. It did pretty well on this motor too.

It was great to see you and your family again. And it was fun to see the bomb-rocket in person and to see it fly with the air-brake recovery. Very cool!

Hopefully we will all meet up again at October Skies --- I want to see the Doorknob go up!

ThirstyBarbarian said:

Thanks for posting these photos, SC! Great job! The high speed camera seems like it worked really well.

Your G Force was the next rocket to go after mine --- in fact, I think mine hadn't landed yet. And I also think you were flying on exactly the same motor, G77-4R. You rocket put in a great flight and it definitely made for a great contrast in how different kinds of rockets fly --- I think yours went several hundred feet higher on the same motor.

It was great meeting you! You've got a very cool and unique fleet of rockets. I think the ones I saw fly were the G Force (flew really well, and was probably the most "standard" rocket you flew, I think), the two-stage mega mosquito (worked great, and was a first flight, correct?), and Caffeinator (very entertaining!). Did you also fly a saucer? I liked the variety.

Thanks again for the photos and also for the advice you gave in several of the threads during the building of this rocket! Onward to TCC's October Skies! Hopefully I'll see you there!

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It was great meeting you too! I flew two saucers, an Estes Snitch (normal 18mm C powered saucer) and a Fliskits Trifecta (3 stage 13mm A10 saucer, unfortunately the sustainer either destroyed itself or went missing). Almost all of my A-C motor rockets are oddrocs. G-Force went to 702 feet according to my Altimeter2, it's about 40% lighter than the MDRMWP. The mosquito has flown before, but this was my first 2 staged attempt and it worked successfully. I also flew my Leviathan on an F23-4FJ right at the end of the day.

I'm definitely going to October Skies for saturday and sunday. I'm going to attempt to certify L1 on a Minie Magg I'm building. See you there! You going to certify on the MDRMWP there?

Mr G said:

Awesome first flight! Glad to see the G77-4 worked for you. I had to run so I missed it if you tried the G78 or G79. Let me know if you need more of the same or want to get into G reloads - I've got them too. And it came so close to sticking the landing...
View attachment 184937View attachment 184938View attachment 184939


And nice to meet another forum member in person!
View attachment 184940
The Thirsty Barbarian -sans helmet- ready for launch.

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Thanks for posting the pics Mr. G! And also thank you for meeting up with me and selling me the motors! The G77-4R worked great, and the next one I flew was the G78-4G. That one worked perfectly too, and the rocket actually did stick the landing on that one!

I am definitely interested in getting more of the motors before October Skies on 10/17-10/19. I didn't want to commit to too many before knowing how the rocket would fly and how the delays would work out, but now I am definitely interested in more. This means my wife may hold you partially responsible for creating the monster I am becoming...

It was nice meeting both you and Mrs. G. I'll PM you about meeting up sometime to take a few more motors off your hands.

Thanks again!

Coop said:

Nicely done! Damned-near stuck the landing--any pod damage?


Later!

--Coop

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ChrisAttebery said:

TB flew it a second time and I'm 99% sure it stuck the second landing.


Sent from my iPhone using Rocketry Forum

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SCrocketfan said:

It definitely stuck the second landing, although I think it had some pod damage on the second landing.

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423yjl said:

Yeah, 3 point landing on the second flight. One of the lower pod cones looked a little out of wack, but not to bad.
We will have to hear from Thirsty about the any repairs needed.

Good to meet you TB

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Yep. The second flight came down and landed perfectly on all 3 pods and stuck the landing. That was fun to see! I think this design may be pretty good at that, with a wide base and a very low center of gravity once the nose cone is out. It's an unplanned an unintended consequence of the design but kind of a cool feature.

Unfortunately, there was pod damage on the second flight. I would have flown it one more time on a G79-4W, but the pod was too damaged, and I wanted to bring it home to repair and not try a field repair. Actually, on the first flight, one of the pods looked damaged at first glance, but it must have just flexed slightly and popped some paint off, because it still felt really solid on closer inspection. But the second flight caused more substantial damage to one of the other pods. I'll post some pictures later, but basically the lower nose cone tore out of the body tube that forms the pod. It was all still stuck together, but it was obviously damaged, and when I wiggled it a bit, the NC pulled loose.

If I want to put it back together the same way, it will be an easy matter to glue the NC back in and glue the torn tube back into place. But I need to think through if that's the best plan or if I can come up with something that will be more resistant to damage. I'm thinking I'd like to attempt an L1 cert flight using this rocket, so I want something that will not get damaged for that. I could put on a slightly larger chute and count on landing on a softer surface than Moffett concrete, and that would probably work.

But it turns out that this rocket does great on G motors and does not get anywhere near the 1,000-foot ceiling at Moffett, so that makes it a fun rocket for Moffett, if I can find a way to keep from breaking the pods on the concrete. I'm not sure a bigger chute will be enough for that. I might need to find something that will have some cushion for the bottom of the pods. I'm open to suggestions!

Landing at TCC should be much more gentle if you fly it at October Skies, especially if you use a different chute. What motors are you looking at for L1? Cesaroni has a lot of H options in 29mm, and you can apparently fly the entire 29mm motor range (except 6GXL) with just a 3 grain starter set and 6 grain case.

I just put another coat of paint on my G-force. The landing yesterday (3rd flight but the first 2 flights were before paint) really damaged a lot of the paint on both the fin can and the payload section, and dropping it taking it out of the car didn't help. I think I'll try krylon clear coat over the paint this time. I totally agree, Moffet is a great place to fly, except for the concrete.

For my L1 cert attempt, I'm thinking I might try one of the Single-use Aerotech motors, like the H135W, and then consider reloads later. Because I don't have any experience with reloads, I think single-use would be the most foolproof way to attempt the certification flight.

On the other end of single-use motors, I'm thinking the rocket flew stable enough and straight enough off the rail to try one of the lower average thrust, longer burning G motors, like the G79 or G40.

According to the OR sims, the G77 left the rail at 40.1 fps, and the G78 left the rail at 39.8 fps, so both of those were at the lower end of the rule of thumb limits for a good takeoff speed. Both of those flights looked stable and straight to me. The G79 sim shows a speed of 36.0 fps. That is slower, but I think it would probably be fine with this rocket. The Aerotech G40 shows a speed of 33.8 fps, so even slower. I actually have Estes G40-4 motors from the Fry's clearance sale, and I have not tried simming those, but I think they are different from the Aerotech motors.

I'd be interested in what other people who saw this rocket fly think about those slower takeoff speeds. Would it be too slow, or do you think it would work?

About the parachute, I think I will order a bigger one. If you remember, I did use a larger one than what came with the kit. When it looked like the rocket was going to weigh more than expected, and I new I would fly it at Moffett, I ordered a 45" chute from Top Flight Recovery. But that was before finishing the rocket, and then it ended up even HEAVIER. It's about 60 ounces with motor, so a little lighter after burnout. I might get something in the middle 50's or even as big as 60 inches for Moffett and for the cert flight. It really does not go very high, so I'm not as concerned about it drifting away as I am about it landing hard. Plus, big chutes look cool coming down!

SCrocketfan said:

I just put another coat of paint on my G-force. The landing yesterday (3rd flight but the first 2 flights were before paint) really damaged a lot of the paint on both the fin can and the payload section, and dropping it taking it out of the car didn't help. I think I'll try krylon clear coat over the paint this time. I totally agree, Moffet is a great place to fly, except for the concrete.

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I hope the new paint works out for the G-Force. That's a nice rocket and put in a good flight.

I think the Estes G40 and Aerotech G40 are actually almost the same, the F50s certainly are. You could probably try the G79 and G40 at October skies, I think the launch rails there may be longer than 6 ft.

SCrocketfan said:

I think the Estes G40 and Aerotech G40 are actually almost the same, the F50s certainly are. You could probably try the G79 and G40 at October skies, I think the launch rails there may be longer than 6 ft.

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That sounds good. I'd definitely give it a try if the rails were a bit longer.

ThirstyBarbarian said:

For my L1 cert attempt, I'm thinking I might try one of the Single-use Aerotech motors, like the H135W, and then consider reloads later. Because I don't have any experience with reloads, I think single-use would be the most foolproof way to attempt the certification flight.

I'd be interested in what other people who saw this rocket fly think about those slower takeoff speeds. Would it be too slow, or do you think it would work?

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+1 on using a DMS motor, both the H115DM and H135W will have a higher initial (and average) impulse than the G78. Once certified, then you will find all kinds of interesting opportunities in assembling reloads, adjusting delays and so forth.

The winds at Moffett were very light for much of the day, that helps a lot on stability with slow lift off speeds as it keeps the angle of attack low for low velocities off the rod/rail. You can estimate the impact of increasing crosswind in OR by increasing the angle of attack in the Component Analysis menu. However, I'm not sure how well OR is at simulating the dynamic CP of this rocket (just not my area of expertise, it may be totally capable of this).

The NAR "Launching Safely in the 21st Century" summary calls out a 4:1 minimum ratio of velocity to wind/gust speed as a best practice since at an AOA of 14 degrees CP can move forward 1 to 1.5 calibers, depending on the rocket.

timro said:

+1 on using a DMS motor, both the H115DM and H135W will have a higher initial (and average) impulse than the G78. Once certified, then you will find all kinds of interesting opportunities in assembling reloads, adjusting delays and so forth.

The winds at Moffett were very light for much of the day, that helps a lot on stability with slow lift off speeds as it keeps the angle of attack low for low velocities off the rod/rail. You can estimate the impact of increasing crosswind in OR by increasing the angle of attack in the Component Analysis menu. However, I'm not sure how well OR is at simulating the dynamic CP of this rocket (just not my area of expertise, it may be totally capable of this).

The NAR "Launching Safely in the 21st Century" summary calls out a 4:1 minimum ratio of velocity to wind/gust speed as a best practice since at an AOA of 14 degrees CP can move forward 1 to 1.5 calibers, depending on the rocket.

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Thanks Timro. That's some good info, and I'll check out the OR simulations for wind speed. It was good to see you at the launch.

I'll have to find out who the vendors are at October Skies and see about arranging for a H135 or H115 DMS motor for certification. Ad if I'm going to try to cert at a Tripoli event, I'll need a membership, I assume, and a few other things in place as well, I would guess.

Congrats on successful Flight.

TopRamen said:

Congrats on successful Flight.

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Thanks, TopRamen. It was a really fun day, and I had a blast seeing the rocket finally fly!

looks great! landing on the pavement or concrete is HARD on rockets! glad it shouldn't be too hard to fix.

Here are some pictures of the damaged pod.












I think this can easily be repaired with glue. In fact, I could have done a field repair with epoxy and flown it again. The question is, what can I do to make a rocket that is not going to get damaged every time I fly it at Moffett field, and it lands on concrete?

One thing I could try would be a larger chute to bring the descent rate down. It has a 45" chute, which means it hits the ground at about 19.3 fps, according to OR. Total flight time is right around 30 seconds on most of the G motors, and around 6 of that is on the way up, so it really does not spend much time coming down.

If I increased the chute size to 60", it would descend at around 14.6 fps, and it would only add about 6-8 seconds to the descent time, depending on the G motor. Longest is 43 seconds. On an H115, total flight time is predicted to be around 75 seconds, and on an H135 it would be 104 seconds. On the 45", those times would be around 60 and 81 seconds. Unless it was really windy, I'm not concerned about these flights drifting too far.

Would this difference in descent rate make much of a difference in the force of the impact on the pods? It would reduce the impact by a good amount, I think, but would it be enough to make a difference? In other words, is the problem really the speed, or is it really that for any kind of practical descent rate, the mass of the rocket landing on such a hard surface is going to create too much shock for a pod constructed this way? The weak spot is apparently the BT60 tube of the pod, and maybe it can't take much shock.

The parachute solution would be the easiest for me, but if there are any engineers or anyone else that can make a suggestion, that would be great. I'd hate to spend money on a chute and find out it made no difference other than just making the rocket drift further.

Too bad about the damaged pod TB but great flight anyway.

bill2654 said:

Too bad about the damaged pod TB but great flight anyway.

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Thanks. It was a fun flight. The pod should be easy to fix --- I just need to figure out the best way to make a fix that will last through more flights.

As big a parachute as you can get into it and have it reliably deploy. You can even have a slow descent and have the rocket swing as it comes down and damage the fins. A big chute will minimize this, just don't fly it if it is really windy.

Great flight!

If you could find a rubber version of the bottom pod cones .. although they wouldn't retain paint and might bounce.

The Estes G40 is the same as the current AT G40, but you might come across some older, higher impulse data for the AT version -- use the Estes version data for both. Ran the sim and getting OK speed but poor altitude. I don't know what they were thinking with the -7 recommendation even for the stock rocket. Incidently I'm not sure if it was you or me but the G80's in the your/my OR sim are old 100 N-s versions. With the DMS motors you can cut the delay to 6 seconds.

ThirstyBarbarian said:

Robert, thanks for recording and posting this video! It turned out great! You've got my name spelled correctly, so no worried there.

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Yeah, and I botched the name of the Rocket. "Mega Der Red Max with Pods" isn't it?

The only improvement I could suggest is that maybe the club could arrange for an acre of padding for the tarmac. You might need a bigger trailer for that.

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I'll make sure to bring that up at the next officer's meeting :wink:

Thanks again for capturing this great video!

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You're welcome, I wish I'd had a better angle so I hadn't lost it in the sun. And you almost stuck the landing the first time, just a bit of sideways drift pulled it over.

I was thinking, tennis balls. But getting them to hold silver paint could be an issue. (Also finding some in the correct diameter to fit the tubes.)

I'm sure that Mike from BAR will be at October Skies. If not I can deliver the motor to you. Just place an order and tell him that you'd like me to pick it up. I think the H115DM would be a great motor for this rocket. It needs that 1930's sci-fi movie sparky flame effect.

rbelknap said:

Yeah, and I botched the name of the Rocket. "Mega Der Red Max with Pods" isn't it?




I'll make sure to bring that up at the next officer's meeting :wink:



You're welcome, I wish I'd had a better angle so I hadn't lost it in the sun. And you almost stuck the landing the first time, just a bit of sideways drift pulled it over.

I was thinking, tennis balls. But getting them to hold silver paint could be an issue. (Also finding some in the correct diameter to fit the tubes.)

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I guess I haven't really figured out a good permanent name yet. At the launch, I was filling out the card MDRM-P for lack of anything better. Maybe "Mega Der Pod Max," or would that sound too much like "Mega Derp Odd Max?" What did you call it? "Der Silver Pod Max?" That it s actually pretty good. I'll have to give it some thought.

A squishy foam rubber ball of some kind might work as a pod bottom cushion. I'm going to look around for some kind of off-the-shelf thing or a material that I can shape into something workable that would have some shock absorbing properties. If that doesn't work, then maybe a bigger chute would do the trick. The nice thing about the nosecone pods is they can be sanded smooth, and the seam filled for a nice smooth finish on the pods, but they may not be practical. If I add more paint detailing to other parts of the rocket, then it is not as important that the pod bottoms be silver --- it'll just look like another color detail.

ChrisAttebery said:

I'm sure that Mike from BAR will be at October Skies. If not I can deliver the motor to you. Just place an order and tell him that you'd like me to pick it up. I think the H115DM would be a great motor for this rocket. It needs that 1930's sci-fi movie sparky flame effect.

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Yes! That Dark Matter would be a cool motor! Thanks for the offer to pick up the motor if need be. I'm not sure, but I think maybe Mike lives in Castro Valley, which is pretty close to where I live. Hopefully he will be at October Skies, but if not, maybe I can drop by and pick it up from him.

ThirstyBarbarian said:

Would this difference in descent rate make much of a difference in the force of the impact on the pods? It would reduce the impact by a good amount, I think, but would it be enough to make a difference? In other words, is the problem really the speed, or is it really that for any kind of practical descent rate, the mass of the rocket landing on such a hard surface is going to create too much shock for a pod constructed this way? The weak spot is apparently the BT60 tube of the pod, and maybe it can't take much shock.

The parachute solution would be the easiest for me, but if there are any engineers or anyone else that can make a suggestion, that would be great. I'd hate to spend money on a chute and find out it made no difference other than just making the rocket drift further.

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Impact energy absorbed (assuming a perfectly inelastic collision which to me is a pseudo-fair assumption because we're talking about plastic & concrete interacting) is proportional to the square of the impact speed. So cutting the impact velocity by approximately 25% using your fps impact numbers would cut the impact energy by about 50%. The more complex nature of the problem is that what shattered wasn't the plastic pod, but the cardboard BT60 itself. You might consider epoxying a bulkhead into the pod itself to give some structural support at that area of the cardboard? Also you might be able to take a small bit of packing foam, cut it into a ring, and put it between the shoulder of the pod and the BT60 tube there... If you re-fill it with foam, it should lock the "shock absorber" in there and you could trim the outside where it hangs over the edge with your hobby knife, cover it with bondo before paint.

Mike emailed me, he will be at October Skies (I'me buying some motors from him there). He had the H115DM in stock a few weeks ago (but not the H135), but it might be good to preorder the motor from him to make sure.

I was at Hobby Lobby today and picked up a sheet of "Craft Foam." It is EVA foam. EVA is a flexible, dense, closed-cell foam that is used in a lot of products to absorb shock --- things like running shoes, exercise mats, and toys that need to bounce off of things (stomp rockets, toy arrows, etc). I wanted to find a block of the stuff, or maybe a cylinder, but haven't been able to. So I bought a sheet that is 5mm thick and also some foam glue. My plan is to cut out a bunch of circles, stack and glue them into a cylinder, and make shock-absrobing bottoms for the pods to replace the bottom cones.

From looking at some of the products I've seen made from EVA, it looks like a lot of them were cut to shape or turned on a lathe, so I'm hoping it is easy to shape with a blade and maybe even sandable. If I have any success working with this stuff, I'll post some info about it.