'Wrongway' build: rear eject 2x cluster rocket

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Looks good and I look forward to seeing how it flies. You may want to double check the friction at the launch, as humidity and other factors can change things.
 
Maiden flight on 2xB6-4 was nominal - system worked flawlessly. Here's a crappy video. I'm bantering with the LCO, too excited to realize that he's pulling my leg! iPhone quality, as in, not very good..

[video=youtube;-7CdtvZ-DRE]https://www.youtube.com/watch?v=-7CdtvZ-DRE[/video]
 
matthewdlaudato said:
Maiden flight on 2xB6-4 was nominal - system worked flawlessly. Here's a crappy video. I'm bantering with the LCO, too excited to realize that he's pulling my leg! iPhone quality, as in, not very good..

[video=youtube;-7CdtvZ-DRE]https://www.youtube.com/watch?v=-7CdtvZ-DRE[/video]
Click to expand...

Nice launch. I like rockets that are less conventional.
 
CZ Brat said:
Nice launch. I like rockets that are less conventional.
Click to expand...

That wiggle near apogee is likely one of the motors popping out (only one remained on landing). Friction fit, so next time I'll use more tape. Didn't affect operation though.
 
Thought about it more - wiggle could also just be one motor burning out a bit before the other, giving it a thrust imbalance.
 
Looks very similar to the US Rockets "18mm Rear Eject" model. I built and flew one last year. Just make sure your chute ejects properly or else it will come in ballistic.
Uh, not that that happened to me...
 
jcantalupo said:
Looks very similar to the US Rockets "18mm Rear Eject" model. I built and flew one last year. Just make sure your chute ejects properly or else it will come in ballistic.
Uh, not that that happened to me...
Click to expand...

I will have to check that out - I'd never actually seen another rear eject model before designing it, so curious.



--
NAR #91867, L2
Member CMASS, MMMSC, RIMRA, CATO
 
Rocket is on the repair bench.. I cut it down once after it had nose dived (chute packed too tight). But it's not stable with the shorter body tube, so here it is with a 2" extension installed and primed.
ImageUploadedByRocketry Forum1472935937.496374.jpg
Looking to have it ready for the next CMASS launch in 2 weeks.
 
Very nice design. I very much like your rear eject. I am working on an alternate rear ejection design myself. (Which will get posted after some testing so I don't have too much egg on my face) ;) I am terribly worried about over pressurizing the BT-60 tube though given the shorter lengths of the tube used in rear eject. I am building a test rocket that will take D's/E's so I think its a .85 G charge. Did you gain any insight as to this? Would a BT-60 5" long hold that charge before separation? Would it hold if double lined with couplers?

Did you ever give any thought to one booster powering rear eject, and one powering front eject? It would give you redundancy.

Tinker
 
Tinker said:
Very nice design. I very much like your rear eject. I am working on an alternate rear ejection design myself. (Which will get posted after some testing so I don't have too much egg on my face) ;) I am terribly worried about over pressurizing the BT-60 tube though given the shorter lengths of the tube used in rear eject. I am building a test rocket that will take D's/E's so I think its a .85 G charge. Did you gain any insight as to this? Would a BT-60 5" long hold that charge before separation? Would it hold if double lined with couplers?

Did you ever give any thought to one booster powering rear eject, and one powering front eject? It would give you redundancy.

Tinker
Click to expand...

Wow, missed this reply. I'd have to see your design to have an informed opinion. No I hadn't thought about the front and rear approach, interesting though.
 
Tinker said:
Very nice design. I very much like your rear eject. I am working on an alternate rear ejection design myself. (Which will get posted after some testing so I don't have too much egg on my face) ;) I am terribly worried about over pressurizing the BT-60 tube though given the shorter lengths of the tube used in rear eject. I am building a test rocket that will take D's/E's so I think its a .85 G charge. Did you gain any insight as to this? Would a BT-60 5" long hold that charge before separation? Would it hold if double lined with couplers?

Did you ever give any thought to one booster powering rear eject, and one powering front eject? It would give you redundancy.

Tinker
Click to expand...

For clusters like this I've seen others use motors with different delays, such as a D12-5 and a D12-7. That way only one ejection charge fires at apogee, and then a "backup charge" fires 2 seconds later.
 
BDB said:
For clusters like this I've seen others use motors with different delays, such as a D12-5 and a D12-7. That way only one ejection charge fires at apogee, and then a "backup charge" fires 2 seconds later.
Click to expand...

That would be interesting, vent only one of the engine pods to the rear, the other forward. May have to consider that for a future design/build.
 

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