Another project I have been mulling over is a new take on the two-stage rocket.
I don't know if this is even feasible, but you folks would be the best sounding board. So, here goes.

I want to build a (big enough) rocket that will act as a 'launch silo' for a smaller rocket, which will be slid down inside the tube of the big rocket, mating the small rocket's engine in some manner over the opening for the big rocket motors' ejection charge. Using a D engine (or less, and I'll explain) with a zero-second ejection delay will light the engine of the smaller rocket (as it works with a regular two-stager) and theoretically - if I've pondered all the issues to address well enough - the small rocket will force the NC of the big rocket up and off the big tube and out of the way, allowing the little rocket to fly up and out...



Yes. Well, several issues immediately come to mind:
1) Nose cones- I think that an NC for the big rocket (probably balsa) would have a rounded bottom and just loose enough to let it get pushed easily up out of the way when the small rocket pushes. I think the rounded NC bottom would keep the NC of the small rocket from getting hung up on anything (depending on what NC gets used here).

2)Recovery equipment - For the big rocket, the original idea was to fold the parachute in the right way to stack it on top of the small rocket (once inserted) and it would get pushed out of the way along with the NC. Yeah... will the parachute get snagged on the small rocket, or vice versa? Great question. This one has me the most worried... unless the big rocket is designed to fall back to earth without damage from a small altitude (and grass field)... read on.

As for the shock cord, I have a couple of schemes in mind: We want the shock cord out of the way - along with the NC and parachute - but the standard installation for this equipment won't work in this scheme.

So, the thought is to install the shock cord outside of the big rocket's tube - the first scheme involves using the thin stretchy cord from the fabric shop, cut to just the right length to put enough tension on the NC attachment so that when the NC gets pushed out of the top of the big rocket tube the shock cord tension will help yank the NC down out of the way (I imagine attaching this cord to one of the fin edges)... and hopefully the parachute with it.

Another scheme is simpler, involving a shock cord attached to the outside of the big NC as well and the rest of the cord kept tucked inside a side tube on the big rocket until the NC falls away and drags the shock cord out and away with it.

3) Einstein - Can the big rocket conceivably act as a good enough platform for the little rocket to get away from? I want to use a zero-second ejection motor for a couple of reasons: if the big rocket is on a straight-up trajectory it'd be best to light the small rocket while the big one is still pointed up. The small rocket would be designed with just enough clearance between the fins and the inside walls of the big rocket's tube to keep it pointing (straight up?). I would imagine the 2nd motor would push against the inside of the big rocket and out of the way, but how good of a chance for a foul-up can the 2nd motor lighting add to all this craziness? Can Einstein save the day? Am I gonna need Vaseline for the inside of the big rocket tube?

And, I envision this rocket as not attaining much altitude before the election launch, so that there's a chance of spectators seeing everything that's going on up there. A smaller motor would give less altitude for the same size payload, and might help here. The small rocket motor itself may not want to be too much (A or B?) so that it doesn't get too far out of sight itself.

This is also a rocket perfromance parameter that you could completely surprise the heck out of people with if they didn't know it was coming...

Your comments on this scheme are welcome.

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-Brain
SKY AYE ROCKETRY
Follow Your Impulse!

Here's a quickie answer with only a little thought behind it...

Typical of some of my responses, of course...

This sounds like a combination of a PISTON LAUNCHER (for the inner bird) and a REAR-EJECTION system (for the booster)...

The idea is still vague in my mind, so I cannot fully explain it yet. There is so much going on in your concept that has to work right. But, you need to think of it as two separate and discreet systems (inner bird, outer booster).

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Craig McGraw

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SAM 0044
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I think somewhere in the history of old Estes Model Rocket News (possibly another publication) there is a 2 stage rocket where the upper stage comes out of the booster and has folding fins. Maybe not quite the same but, along the same lines. I do enjoy all of your designs and the fact that you are looking at rockets a little differently. Keep it up.

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Rick Randol
NAR #28062, ROCI Section #625
http://www.newwayspacemodels.com
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NewWay Space Models-We Cornered Model Rocketry

Yeah, you might be better off with something like a reverse helicopter recovery. Have it spring open and move out of the way. Kind of like in the James Bond movie.

You might be thinking of this:

http://plans.rocketshoppe.com/narts...iddenWonder.pdf

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Bill Spadafora
http://www.billsplumbing.com
billspad@comcast.net bill@billsplumbing.com

You've boiled it right on down!
The two top issues: Getting the big NC and recovery system out of the way & unfouled somehow & getting the small rocket motor to light. The rest is finger-crossing.

Another bullet point is what to do about the 'launch silo' interior of the big rocket. When that small rocket lights it obviously has a pretty fair chance of burning something in there until it's away. I have thoughts of lining the interior with aluminum foil, but then there's the issue of the tolerances of the small rocket (which I think shouldn't rattle around in there much), and in particular the mechanism by which you'd mate the small rocket business end to the ejection vent of the big rocket... that would need to be protected if you wanted to re-fly it. But I don't necessarily want to have to replace the shielding every time I fly it. Hmmm...

I have attached a pic of the basic design concept. I wanted both rockets to be mirrors of each other in design, compact design (I figured the small rocket proportions would call the shots for the style of the big rocket), and not be fancy-fins that could get busted if all this fails and falls. But, all kinds of revisions are up for grabs at this point.

Thanks, all!

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__________________
-Brain
SKY AYE ROCKETRY
Follow Your Impulse!

I still think this would be cool.
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This concept kept me up last night and I even dreamed about it (darn you!)

I had a couple of thoughts you might consider... if you want to go with conventional fins on the interior rocket,
I'd suggest adding some at the top too, that way it would stay more stable while in boost phase. I also thought
that maybe a single ring fin at the base might be feasible if it was small enough to not worry about hanging up,
with the standard fins at the top.

Also, another option would be to have the interior rocket be a two-stager. The "top" of the interior rocket could
be a transition that fits into the outer tube. Which would also have an engine mount in it. When it boosts out,
the interior booster then fires the final sustainer, which is actually the whole top part of the original rocket. That
way you get a three-stage rocket out of what looks like a single stager.

As for the recovery system of the outer rocket, if you go with the conventional nosecone theory, you might also
consider running a couple of "booster" pods on the outside of the main booster, and hiding a parachute in one of them,
but to really make it work you'd have to put engines in the pods. Then attach the main nosecone with kevlar
thread glued to the *inside* of the main booster section so when it gets pushed out it stays attached to the body
and if you glue the thread down you wouldn't have to worry about it getting fouled in the fins of the inside rocket.

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Dale Marshall, San Antonio Texas
NAR #90990
Semroc SAM #083

BAR Since 2008
Enjoying model rocketry since 1977.
The Spotted Dragon
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"Son-ah say son slow down there! Yer talkin' nonsense, boy - drivel! It's like I'm talkin' to a rocket surgeon or somethin'... one o' them eggheads!"

Like Foghorn said - one step at a time. But I like the way you think...

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__________________
-Brain
SKY AYE ROCKETRY
Follow Your Impulse!

Looking at your drawing I was thinking , how about if both the outer and inner rockets shared the same nosecone? A nosecone like the Honest John, or a cone to fit the outer tube with a transition where the shoulder ends to taper it to fit onto the inner rocket. Still not sure how recovery of the booster would work but solves the problem of getting the upper cone out of the way. Wouldn't really be quite the same thing , just a thought.

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