I am shortly going to need to make some design decisions regarding the chute packing tube on my #2001. As I will be increasing its weight with a removable engine core design as well as flying with a 5 engine cluster and longer term F & G engines, I know that I need to upgrade the recover side of the equation. I certainly plan on upgrading to nylon chutes. Until I have exact weights I really don't know how much chute area is needed or if I should go with two larger chutes or 3 slightly smaller chutes.

With those things in mind, I am deep into the design of my removable engine core setup and I am debating either a BT-50 or a BT-60 chute packing tube. I would appreciate any thoughts regarding the chutes and particularly the chute packing tube size that I should build into my design.

Thanks
David

I would go for as large a stuffer tube / parachute compartment as is practical.

I'm not sure of the reliability trade-off between one large / several small parachutes. I imagine there's a reason that NASA uses multiple parachutes . . . but they likely have redundant ejection systems and harnesses that prevent tangling.

Things to consider:
* Recovery harness to allow horizontal descent. This means a line dangling on the outside, but you have a better chance of preserving your fins
* Separate capsule recovery. Another thing to track, but one less thing to tangle, and you can use a line hang the capsule from the tower.

For sure:
* Nice long piece of elastic.
* Swivels between the anchor cord (kevlar?) and the elastic, and the elastic and the parachute / nose code.

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NAR #27085 - Oregon Rocketry - SAM

Stefanj,
Thanks for the tips. I am doing the build with the Moldin' Oldies resin cast fins/shirts and Apollo/solid LES so my SV will be a bit more tolerant on recovery. I had not considered altering the lower section chute for two point attachment, but not a bad idea and VERY doable especially with a single LARGE chute. I know that multiple chutes do offer a bit of redundancy but the risk of tangled lines is offsetting. Yes I will be using epoxy secured Kevlar shock line mounted into the base of the fixed part of the interchangeable engine core on the lower section. I am not bothered in the least at having a external cord from the separation junction to the bottom of the lower section attached with a swivel hook as the line can be detached for display (similar setup as the upper section).

Going with a single LARGE chute for the lower section may require a rethink on the chute packing tube. I will have to do some investigating on the recommended diameter for a single chute capable of handling the weight of the lower section with the 5 engine cluster (assuming that to be the heaviest of my engining options). Don't know if a 36" will do the trick or something larger will be needed. The original Estes design had 2, 24" plastic chutes. I do know that the lower section of my SV build WILL be heavier than the original design. I will be building out the original long single engine tube for weighing purposes so that I can compare to the weight of my custom interchangeable design. Yes, I am well aware that I have to watch the CG and compensate in the nose for the added weight. As I will have different engining options, I will have to adjust the added nose weight depending on how I want to fly.

I will add swivels to isolate the elastic on both ends.

On the #2001 the capsule/LES is part of the SM/SLA/3rd stage which separate as a unit at chute ejection and as designed use a separate chute with a two point attachment to the section for a upward tilted horizontal recovery. Other than switching to the Moldiin' Oldie resin cast Apollo/solid LES and a nylon chute (i.e. no plans to use the 20 year old plastic chutes in the kit), I feel the original design for the upper section is sound. I am thinking that I will make the Apollo/LES detectable for adding nose cone weight and to allow me to use the original Apollo/open structure LES for display. I am thinking that a couple of small translucent automotive trim push/lock pull/release plastic pins on opposing sides where the Apollo slips into the SM section will be the way to secure the Apollo/LES for flight and be virtually invisible. With the Apollo itself removable I can make the bottom of the 3rd stage transition ring solid rather than the original open design. The present open bottom 3rd stage transition ring just provides space to lessen the pressure on ejection as well as a place for the chutes to potentially become entangled.

Thanks again. Having the wisdom of everyone that has built and flown the SV makes this a lot more enjoyable and added confidence that I can avoid the dreaded lawn dart flight.

David

Do NOT, I repeat DO NOT try to stuff chutes for this into an internal BT-50 tube.
A single 36" quality NYLON chute will be PLENTY for the lower section, and a single 24" will be plenty for the upper section.

__________________
When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, and HAVOC !

So are you cautioning specifically against the BT-50 or the use of a chute tube in general? I realize that the original design had the dual chute laying inside the BT-101 airframe just above the termination of the core tube, but would not an appropriate sized chute tube (i.e. for the recommended single 36" chute) be more likely to deploy the lower and the upper chutes as well as eject the upper section of the @2001 SV rather than attempting to pressurize a larger upper cavity of the BT-101? I am open to just about ANY sized internal tube including the BT-80 tube that will be the fixed portion of my interchangeable engine core design. Assuming you are just advising that a BT-50 is TOO small, then what sized tube would you recommend for the 36" chute?

Thanks for the advice on the chute size. Once I have the final weight of the lower section determined, I will reconfirm that a 36" still seems appropriate.

David

I have a tough time packing a 30" nylon chute in a BT-55 for my R-7. I'd use at least a BT-60 and would seriously consider a BT-80. I built my Saturn V to separate at the top of the lower transition/bottom of the S-IVb stage and have a BT-80 parachute compartment below that.

I built a Skylab S-IVb stage (obviously, with no delicate LES on top) that I can swap out with a lunar package S-IVb stage for when its just sitting around the workbench.

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NAR 79743
NARTrek Silver
I miss being SAM 062

Awaiting First Launch: Too numerous to count
Finishing: Zooch Saturn V; Alway/Nau BioArcas; Estes Expedition; TLP Standard
Repair/Rescue: Cherokee-D (2); Centuri Nike-Smoke; MX-774
On the Bench: 2650;
Dream Stage: 1/39.37 R-7

I have a 2001 Saturn V and the only mods are heavier-duty resin fins and a 29mm heavy-duty motor mount and heavy duty retention rings for the mount from the Commonwealth upgrade kit.
I did NOT use any sort of "parachute compartment" tube and it ejects just fine on SU 29mm motors, 29mm RMS motors (the mount will fit a full 240n-sec 29mm case) and 24mm SU/RMS motors.
I have never flown it on an Estes 24mm single motor, but have used the 29mm F15-4 and there were no problems pressurizing the BT-101 with that either.
I have a 30" Semroc Nylon chute on the BT-101 lower tube and a single 24" Nylon chute on the upper section.
If you are going to use a chute tube internally, a BT-60 would be the absolute minimum diameter to pack a 36" and 24" chute into. I would use at least a BT-70 if not a BT-80 if I was inclined to do this.
I think it is a waste of just added weight though.

__________________
When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, and HAVOC !

You don't need a chute tube. Lay your upper section chute in first. Lay your main chute in on top of it. Ejection will kick the upper section away and pull both chutes out easily. If you aren't convinced, remember you will be using clusters or AP motors which have a hefty kick on the ejection. The upper section will shoot away from the lower section.

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Not that I will fly the SV on a single 24mm engine all that often, but it is an option. That said, I am a bit uncomfortable, maybe needlessly paranoid, about the ejection charge not being sufficient powerful or concentrated in that config. I have decided that rather than transition to a smaller chute tube, I will stay with the BT-80 size and just run an extension from the baffle coupling to the top of the BT-101. This will strengthen the BT-101 airframe as well. I am going to add a bulkhead at the bottom of the 3rd stage body tube coupler to seal off that area as NO need to pressurize the space in the upper section on ejection. I plan on making the Apollo/LES removable so as to add clay for CG balancing as I change engining. Yes, I am probably am over-engineering this, but I don't want a lawn dart experience if I can avoid it.

David

I've exclusively flown my Saturns on a single D12-3 or a cluster of C's and have never had an ejection failure. If there is enough ejection to separate the sections and you have packed the chutes properly, they will be pulled out by drag on the upper section. If you stuff chutes into a small chute tube and there is a weak ejection, you may have enough to separate the two sections but friction of chutes stuffed into small tube may keep them from deploying. That scenario is responsible for just about every lawn dart outside of no ejection charge at all.

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I love sanding.