Science: Space: Launch
3 Rocket Circus   (+4)  [vote for, against]
N-Prize design

This design is in the form of yet another rockoon. My “3R Circus”© design overcomes what I always saw as a major handicap to space launches by de-linking the thrust energy supplied by a rocket from the need to lift the mass of the rocket itself into high orbit. My contraption consists of 2 large rockets “A” and “B” and a small rocket “p” carrying the payload with all 3 rockets lifted as high as possible by balloon before ignition.

Rocket “A” faces upwards and has a small smooth ring fastened to the bottom part of its fuselage through which runs a lightweight, high-tensile line (Kevlar thread perhaps?). Rocket “B”, suspended just below Rocket “A”, faces downwards with one end of the high-tensile line affixed to its fuselage. The other end of the line ends far below with another small ring attached. Hanging from this end-ring is payload rocket “p”. The hook on rocket “p” is angled so that the rocket hangs slightly canted.

When the whole contraption reaches maximum altitude and sensors in rocket “p” detect it happens to be facing east it emits a signal which releases the balloon and sets all three rockets firing. Rocket “A” goes up at velocity “x”. Rocket “B” goes down at velocity “y”. These two rockets are therefore separating from each other at velocity (x+y). The high-tensile line is drawn through the ring affixed to Rocket “A” which pulls payload rocket “p” upwards at a rate of 2(x+y). Rocket “p” also has its motor firing to add its contribution to the vertical thrust but more critically supplies the Delta Vee towards the east and hopefully into orbit after it unhooks from the line’s end-ring.

The big rockets may well be recoverable through parachutes etcetera. Calculations of burn times and the distance travelled by rockets “A” and “B” before cessation of thrust would be done to determine the length of line needed in order to maximize utility. There may be small refinements such as delaying the firing of the payload rocket until moments before hook release. Please feel free to add any comments or suggestions (puns about having a small “p” in orbit are naturally obligatory).
-- AusCan531, Aug 10 2011

Illustration of 3 Rocket Circus Design
"What am I - an Artist?" [AusCan531, Nov 17 2011]

Cunning. How do the economics (eg, payload fraction of the whole shebang) compare to just using A, B and p as a three-stage conventional rocket?
-- MaxwellBuchanan, Aug 10 2011

Why rocket "B" ? Why not just attach one end of the line to a fixed point on the surface, or a very heavy object ?

When the line is fully tensioned, rocket "A" fires, lifting rocket "p" with a 2:1 mechanical advantage.

Because rocket "A" is tethered, it's easy to find it when it lands; just follow the string.
-- 8th of 7, Aug 10 2011

Hello! What have we here... a newbie - with the pyromania complex AND the Rube Goldberg gene!

Unfortunately, I can't give you a bun on this (weight of cord, mass of cord, drag of cord, forces on rocket A, wastefulness of rocket B) but I'll just give you the ingredients. There's definitely some sugar in there, and probably something you can use as an oxidizer.
-- lurch, Aug 10 2011

You could nest these systems, gaining a velocity advantage at each nesting.
-- MaxwellBuchanan, Aug 10 2011

[Lurch], kevlar might not be the ideal material for the cord, but diamond monofillament or spider-silk protein offer interesting alternatives to keep the mass down. Frictional losses can be adressed in a number of ways. We agree that rocket" B" is wastefull, but on the other hand are eager to support and nourish pyromania.
-- 8th of 7, Aug 10 2011

Hi Halfbakers. I don’t think Rocket “B” really is wasteful as it doubles again the speed of payload rocket “p” before release. Think of the 3 rockets as a closed system where "A" acts as a fixed point. "B" going down clearly causes "p" to go up. Merely tethering the end of the line to the ground would provide “p” with double “A”s velocity (and require a heckuva lot more line) whereas adding Rocket “B”s velocity would give poor little “p” a 4 times kick-in-the-pants (actually more than 4X's when you consider the fact that “A” loses 9.8 m/s/s acceleration while “B” gains it).

All I have really come up with here is a simple pulley system. If we used [8th]’s suggestion of fixing the line to the ground I’d want to connect it to a really fast winching system (after all weight of the motive unit no longer matters) providing we first negated the weight and drag problems so we didn’t end up just yanking “A” out of the sky.

As [MaxwellBuchanan] suggested (and if you had materials up to the task) you could get fancy by also converting “B” with a pulley-ring and add rockets “C” and “D” into the mix to gain a couple more doublings of velocity. I had considered that variation but decided it’d just be silly as I’ve got enough trapeze work going on as it is and, after all, I have HIS piddling budget to work to.

I came up with the circus name because, whenever my mind’s eye visualizes this all kicking off, my mind’s ear hears calliope circus music. Try it, it really helps!

As to the economics of the 3 Rocket Circus © compared to a conventional 3-stage rocket I think the 3RC system is better. The ‘boring configuration’ entails “A” lifting the combined deadweight of “B” and “p” to altitude then having “B” lifting the deadweight of “p” even higher. All of which requires more fuel to lift the deadweight which in turn requires more fuel to lift the fuel and so on and so forth. As to proving this with real, actual calculations, etc., what am I – a rocket scientist?

Actually my pyromania is reasonably under control these days with the new medication but confess that I am a leeetle bit queasy about the possible consequences of garrotting a few dozen citizens when a kilometre or more of Kevlar thread or diamond monofilament wafts onto some hapless city. Is the £999.99 budget supposed to include the insurance costs? If not and I can pay for that separately then queasiness abated.

BTW [Lurch] thanks for the sugar and the oxidizer. Could you throw in some vinegar and baking soda as I’ve got this idea for a propellant mix I’d like to try…
-- AusCan531, Aug 11 2011

Upon further consideration, Rocket "B"s velocity is additive not multiplicative. "p" would get 2 x "A"s velocity PLUS "B"s velocity. You would still gain the benefit of "B"s 9.8m/s/s gravity-assisted acceleration though. If anyone objects to my first iteration being wrong all I can say is: "What am I - a pulley scientist?"
-- AusCan531, Aug 11 2011

Little rocket Z went Voom.
-- pashute, Aug 15 2011

// Hi Halfbakers //

Hi backatcha. You, friend, are obviously one of us.
-- Alterother, Aug 15 2011

I still don't think Rocket "B" is wasteful, as it would function very nicely by itself to give little Rocket "p" a boost by just using the balloon as a fulcrum/pulley, HOWEVER, it could be replaced by a drogue parachute in the interest of saving weight whilst still giving Rocket "A" something to pull against.
-- AusCan531, Jul 23 2012

random, halfbakery