Discovery Science Fastest to 10,000' Race (LDRS30)

[kopius]

As you are probably aware, A few of us recently had the great opportunity to attend LDRS30 in Argonia, Kansas, hosted by our good friends from K.L.O.U.D Busters.

Discovery Science channel were there filming a number of flights and events including their own Fastest to 10,000 Feet race. With some last minute planning, I teamed up with Cryoscum to enter this challenge.

Nic did an amazing job on rolling the tube and turning the NC and coming in at just over 300grams including everything except motor, SideShow4 was born and definitely a force to be reckoned with!

SideShow 4

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Packaged up and ready to travel, SideShow4 was an interesting topic of discussion through various airport security points. Most were more interested about rocketry in general throughout the discussion so it was a great opportunity to plug what we do.

SideShow 4 packaged for flight

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Many people were blown away with the build and I was very proud to announce that it was 100% Australian made. Discovery Science paid for a Featherweight Raven to fly, so that coupled with an EasyAs RDF from Wooshtronics was payload of choice for the flight. Prior to flying, contestants had a number of interviews with the TV crew and I quickly earnt the title of "Media Hog" (OK hog was actually another word, but this is family friendly site ). They were quite fond of the Australian crew, could have been because of the Wagon Wheels and Australian Rocketry Stubby Holders I gave them, but I think it was just coz we had traveled so far and were participating with so much gear. It was really kewl to meet Kari from Myth Busters and CJ and I had fun chatting to her (For all the fans out there, yeah she is real cute in person).

Crazy Jim and Blake chatting with Kari Byron from Myth Busters before the fast to 10,000' Drag Race

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Enough of the media and lead up, it was time to fly this sucker! Now original plan was to use a J570W (38/1080), however being the Wildman Distributor that was going to be an issue. (For those who are not aware of the Wildman Oath, you need to buy a kit and learn it!! (Yes this is a sales pitch) Once you have read it, you will understand why a J570 is an issue for this flight. If you want to know the story of how it started email, me, quite a funny story and good work Crazy Jim! haha) Where were we... oh yeah, Tim "Wildman" Lehr found in his stash a J510W which for those who don't know fits a 38/1320 case, has 189 more total Ns than the J570 and burns for .4 of a second longer, needless to say, this was a wild motor that left no airframe space for the faint hearted! With this being said, I used two 3"x3" nomex blankets as a legal form of (vertically challenged) streamers.

SideShow 4 loaded into tower

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There were many different styles of rockets, of all shapes and sizes. SideShow 4 was the smallest and lightest by far. Before I forget, a huge thanks to Coop for lending me his 38mm tower launcher. Best viewed in HD, I am on the far right...


As you can see, SideShow 4 was CLEARLY the fastest rocket, however unfortunately just under 2 seconds into the burn, we suffered from fin flutter which (by my sad face) can be seen below.

SideShow 4 Blake sad face

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SideShow 4 broken fins

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Unfortunately the ejection charge, which was only .4grams was a little too much and sheared the steel wire. After some SARTIME, the nose was recovered, however an already weak signal quickly disappeared and no electronics (or sled) were found.

SideShow 4 broken nose cone

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A few interesting points:
1. None of the fins tore completely off.
2. The fillets are still in perfect condition and all damage is above them.
3. The kevlar shockcord although partially torn, is still in one piece meaning that it has more than likely sheared through the steel cable.

we have learnt a lot from this project and SideShow 5 is now underway. With the design changes we think it will survive the biggest challenge yet. Unfortunately I can't elaborate too much just yet, but well over Mach 3 in the 38mm configuration is the goal.

[rocket_troy]

Awesome stuff!

I reckon you're soon bound to be the world foremost expert on what energy and force can do to rocket airframes and whatnot from aggressive flight profiles Blake [chuckle]

TP

It ain't rocket surgery...

well...

[ROCKet STAR]

Very impressive despite the problems. It's a shame the flight computer wasn't found, I can only imagine how fast it must have been going for the carbon fiber to disintegrate like that. Was there any blistering on the nose cone similar to to what Simon and David experienced with their rocket?

Can't wait to see the next one!

[kopius]

Thanks for the reminder, yes there was a lot of blistering on the NC, so I can only assume that it was well into Mach 2 when it fluttered.

haha, you're spot on there TP. It's not aggressive though, just assertive

[cryoscum]

Strange! The 2pack paint I use didn't blister at all on the Williams mach 2.2 flight, so this must have been quite a bit faster. Also, this was a Von Karman NC and not just some guessed shape like the Williams one, so it should generally deal with the speed better.

[Scoop1261]

Here is Media W....; I mean Hog explaining to the Discovery Channel folks just where it all went pear shaped!

Not sure if he actually knew what he was saying, or if he was just trying to impress Kari!

[hybridhighflyer]

Great work.

I must say I dont think you did anything wrong. Though that does happen when you live life on the edge.

[Sumo310]

We had blistering on the nose and fins, and the tip of the nose was ablated

[Kryten]

Probably an over-simplification:
The fins weren't stiff enough, or too stiff to absorb the vibrations.
Were these just CF/epoxy? How thick?
Increasing the thickness would make them stiffer - you could use a balsa core which wold add very little weight.
However, thicker fins will increase the drag (bit of a Catch-22 situation)

For the result your're trying to achieve, I wouldn't paint it. Just sand & polish

[Andrew Burns]

Yeah fin flutter is just a feedback system between aerodynamic oscilations of the fins and the structural stiffness of the fin. If the aerodynamic frequency of the fins matches to the structural resonance frequency of the fins or one of its harmonics you get destructive levels of oscilation. As flight velocity increases the frequency of aerodynamic oscillation on the fins increases so the faster you go the stiffer your fins need to be to keep their resonant frequency above the oscillation frequency. As Kryten suggests, an easy way to add stiffness without much weight is to make the fins thicker by adding in a balsa or foam core, you do however increase your drag a bit.

[PK]

Not saying it applies to this case, but there's another modality when the leading edge sweep angle is less than the propovation angle of the shock wave created where the leading edge-body tube discontinuity. The shock wave is incompressible and, if it hits the fin the you get very high point loadings.

I have a spreadsheet somewhere that does the calcs for this and also estimates the chance of fin flutter for a given material, thickness, planform combination.

PK