I wouldn't bother unless you're worried about protecting the chute. A piston is more weight in the wrong end. Even for chute protection I'd just go with generous dog barf above and below.This rocket has (4) D12's firing off ejection charges 3 seconds after the fuse lights to fire the 2nd stage motors.
Do you folks think it would be prudent to build a piston to push out the parachute... or is that not needed?
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Maybe even a yummy dog barf and wadding sandwich on top. The Dangerwich! Better watch out...it's spicy! LET'S RIDE! A successful launch will quell the misery of all those Broncos fans in Lakeroadster's neck of the woods.I wouldn't bother unless you're worried about protecting the chute. A piston is more weight in the wrong end. Even for chute protection I'd just go with generous dog barf above and below.
Are you using traditional or flash pan for the fist stage...don't remember if it was mentioned before.
Chute-cannon. Staging is already complete so there is nothing to pull the parachutes out. Next option I can think of is a smaller tube above 2 motors on one side replicated over 2 motors on the other side. In that smaller tube is housed your parachute. It could have a fixed "piston" like PML employs or a baffle system but I'd recommend a few layers of tissue based wadding followed by dogbarf and parachute on top. This could be replaced with nomex but in this case I'd recommend not. I normally refer to this as a soft piston or a LP chute-cannon.@Daddyisabar , @boatgeek , @jqavins
The only reason I thought piston was I've read probably 30 threads here on TRF where folks make a point about "The ejection charge doesn't push the chute out. It pops off the nose cone, and the nose cone drags the chute out".
Since this is a stage and thus has no nose cone, I figured with a piston... the chute has no alternative but to exit the fuselage.
I think there may be some truth to that statement in large HPR projects or cases where the ejection charge is between the airframe break and the parachute (eg HED and drogues in "normal" dual deploy setups).@Daddyisabar , @boatgeek , @jqavins
The only reason I thought piston was I've read probably 30 threads here on TRF where folks make a point about "The ejection charge doesn't push the chute out. It pops off the nose cone, and the nose cone drags the chute out".
Since this is a stage and thus has no nose cone, I figured with a piston... the chute has no alternative but to exit the fuselage.
I've read some of those (not 30) too, and for every one I've read two or more that say the chute must be pushed out, not pulled. Popping the nose so that it pulls the chute would require ejection gas to bypass the chute on its way to the nose cone. If I were counting on that, I'd want the chute in a nomex bag (which I'm given to understand is not uncommon in the larger HP designs).The only reason I thought piston was I've read probably 30 threads here on TRF where folks make a point about "The ejection charge doesn't push the chute out. It pops off the nose cone, and the nose cone drags the chute out".
And thus my preference for a baffle. (Well, that among other possible problems that potentially result from unnecessary moving parts).Thinking it over, I'd worry more about a donut piston jamming up when one of the side motor ejection charges fire a fraction of a second before the others.
I'm going to go out on a limb and say that it's an area of disagreement because it's an area where several physical models make some amount of sense and it's really hard to actually analyze/see what's really happening. An ejection charge test with a clear airframe might do it.I've read some of those (not 30) too, and for every one I've read two or more that say the chute must be pushed out, not pulled. Popping the nose so that it pulls the chute would require ejection gas to bypass the chute on its way to the nose cone. If I were counting on that, I'd want the chute in a nomex bag (which I'm given to understand is not uncommon in the larger HP designs).
And thus my preference for a baffle. (Well, that among other possible problems that potentially result from unnecessary moving parts).
The piston would have a hole through it's center, so it would ride up the center fuse conduit tube.... but I'm thinking I'll just abandon the piston idea, and load it up with dog barf, above the chute and below the chute.I think there may be some truth to that statement in large HPR projects or cases where the ejection charge is between the airframe break and the parachute (eg HED and drogues in "normal" dual deploy setups).
In this case, I have a really hard believing that 4 ejection charges aren't going to blow that chute out just fine. You're not using a ramrod to set it into place after all. Thinking it over, I'd worry more about a donut piston jamming up when one of the side motor ejection charges fire a fraction of a second before the others.
Envision it going straight up, no angle at staging!How I envision this rocket.....
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How the non rocketeer world envisions this rocket....
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Is the fourth stage chute rear eject? And the machines say all these sustainers will be stable at speed...More work on the CAD model... I haven't stumbled across any show stopper issues.
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YesIs the fourth stage chute rear eject?
Yes... spin stabilization and base drag.And the machines say all these sustainers will be stable at speed...
The third stage chute is forward deployed by the third stage booster motor?
Nothing "popping out" for base drag? Just the tube diameter.
The adequate stabilizing spin is imparted and continues by canted fins on the first stage, immediately on and just off the rod until staging?
One example, from the Jedi archives: another MIRV (4 instead of 3)… staged & clustered … with … BP motors… How did the ancients do it???
My THUNK! GDS rocket used spin stabilization with (6) really small spin tabs (aka fins). It worked great, you can actually see the corkscrew engine exhaust trail.This may be your most impressive engineering endeavor ever, which is saying a lot!
one issue I potentially see with roll stability. Just like a potter’s wheel with the first lump of clay off center, or some washing machines that start wandering around the laundry room with a heavy off center lump of clothing, a concern you will have with spin stability, ESPECIALLY imparted spin stability (where the spin starts with canted fins on one stage and is ASSUMED to continue slowing only to surface drag on subsequent stages) is rocket packing. With those rear eject chutes on the OUTSIDE of the motor mounts, it may not take much “wobble” to cause a much more rapid loss of spin than projected. The mass off your monolithic nose cone is presumably evenly distributed, and may be such that any asymmetries from the other parts would be negligible. Then again, depends on how fast this puppy spins.
as for the last stage not being stable, but doesn’t matter, I agree. Assuming it is at any decent altitude, if it is stable it is stable, if it is UNSTABLE, since it has no fins, I doubt the imparted rocket motor thrust is going to MAKE it become stable, so it will likely do some entertaining skywriting and then burn out, hopefully popping the chute before touchdown. This was one of my beefs with Estes MIRV (the primary beef being they had no business releasing it until they had an 18 mm zero delay motor capable of lifting that stack! if/when the C5-0 comes out they should re-release it.). In any case, the MIRV sustainers were two finned rockets and were NOT stable, though again no big deal as they would stage high and just skywrite.
hope you get let’s see…..five……ten……oh heck, lots of straight trails!
So the third stage is stable even after the fourth deploys? (I would think with a now blunt nose if not a gaping hole it would start tumbling (still upwards as until drag and gravity overcome kinetic energy, which would be considerable.). If indeed it is stable, would make an interesting camera or cameraS View (one on each side to increase odds of catching it) looking DOWN from stage three and watching it overtake stage 4.The fact that you have a third stage coasting higher than the powered fourth stage is... impressively weird.
The fact that you have a third stage coasting higher than the powered fourth stage is... impressively weird.
So the third stage is stable even after the fourth deploys? (I would think with a now blunt nose if not a gaping hole it would start tumbling (still upwards as until drag and gravity overcome kinetic energy, which would be considerable.).
an interesting byproduct of combination of base drag and spin stabilization, should (I theeeeeenk) be more resistant to weathercocking than typical staged low power birds.
how big a group do you fly with? You’ll need designated spotters to track each stage if you hope for a second flight.
This is when I learned that when viewing an Open Rocket Plot, you can "left click" on the curve to identify it... which on a multi stage rocket helps a lot.
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