Author Topic: Shape changing rocket nozzle.  (Read 18124 times)

Offline aero

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Shape changing rocket nozzle.
« on: 07/26/2014 07:17 am »
I have been looking at the size of upper stage rocket nozzles while considering using two of them together. But upper stage engines operating in vacuum  have high expansion ratio which result in large diameter nozzles. Two of them side by side don't fit so easily within the confined space of the launch vehicle inner stage so I had the idea to make the nozzle extension from memory metal.

The concept is first, make a bell nozzle extension from memory metal. Next corrugate the memory metal of the nozzle extension lengthwise starting away from the attachment edge and to the nozzle exit. The corrugation would become more extensive near the nozzle exit with the objective of reducing the diameter of the nozzle while it is stowed within the inner stage. Once the engine started, the exhaust heat would quickly cause the memory metal to return to its original bell nozzle shape, because that is what memory metal does.

The other problem of course is the length of the nozzle. These high expansion ratio nozzles can be very long, and need a very long inner stage to contain them. I can envision the corrugated nozzle described above resuming its bell shape, and I can envision a similar folding around the nozzle circumferentially to reduce its length but I'm at a loss to imagine a pattern to accomplish both on the same nozzle extension.

First question - Does anyone know of efforts to make or research nozzle extensions made of memory metal?
Second question - What limitations do memory metals have that would preclude using it as described above?

Wikipedia is always a good place to start, http://en.wikipedia.org/wiki/Shape-memory_alloy
This is cute,

I easily find references using the force generated by shape changing memory metals, but little (read that as nothing) about changing the volume of anything similar to a nozzle or a container.

Edit Add: After sleeping on it, it occurs to me that corrugation of the nozzle extension in a spiral pattern would reduce both the diameter and the length of the nozzle extension.

« Last Edit: 07/26/2014 05:31 pm by aero »
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Offline cosmicvoid

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Re: Shape changing rocket nozzle.
« Reply #1 on: 07/27/2014 08:25 am »
Interesting idea.

I wonder if there are any memory-alloys that would remain solid at exhaust temperatures.
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Offline aero

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Re: Shape changing rocket nozzle.
« Reply #2 on: 07/27/2014 01:30 pm »
It turns out that memory metal is a challenge to make with repeatable properties batch to batch. Its also a challenge to weld to maintain the memory properties. The market currently offers sheets a few inches square as well as longer 3 inch rolls. Its also a little pricey although I didn't compare its price per gram to gold so I can't say how pricey.
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Offline ANTIcarrot

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Re: Shape changing rocket nozzle.
« Reply #3 on: 07/27/2014 03:23 pm »
I strongly suspect that any performance gains could just as easily be achieved with a larger conventional nozzle and interstage - at a fractio of the R&D cost.

While we're on the subject though...

Has anyone ever looked into making linear rockets variable geometry? In a back of an envelope way, it seems far easier than doing it for circular designs. At the simplest you're talking about one hinge joint, and two small amounts of flexible piping for the coolant. I know circular bells are more efficient and simplier to make than linear 'bells' (channels?) and the ends are a problem. But IIRC, that wasn't a show stopper for the X-33.

Anyone know of any research along these lines?

Offline john smith 19

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Re: Shape changing rocket nozzle.
« Reply #4 on: 07/27/2014 09:42 pm »
First question - Does anyone know of efforts to make or research nozzle extensions made of memory metal?
Second question - What limitations do memory metals have that would preclude using it as described above?

Wikipedia is always a good place to start, http://en.wikipedia.org/wiki/Shape-memory_alloy
This is cute,

I easily find references using the force generated by shape changing memory metals, but little (read that as nothing) about changing the volume of anything similar to a nozzle or a container.

Edit Add: After sleeping on it, it occurs to me that corrugation of the nozzle extension in a spiral pattern would reduce both the diameter and the length of the nozzle extension.
Memory metal is sometimes called NiTiNOL so you're talking a Nickel Titanium alloy, which is promising from the PoV of high temperature resistance.

There has been quite a lot of variable geometry nozzle designs. The classic solution that's actually been used was the 2 piece reinforced carbon carbon nozzle on some versions of the RL10 (AFAIK only fired when both sections had been fully extended and locked) The classic unused option is the plug nozzle (suggested for space tug applications) and "scarfed" (but conventional) nozzles wrapped around an "expansion" structure (also essentially a plug nozzle).

In the late 60's or early 70's Bell Aerospace also did a project based on using (IIRC) fairly thin Rhenium foil layers as a sort of "sock." A series of ribs had rollers on their ends which extended, pulling the foils taunt into their correct shape. It seemed to work and (in principle) could operate at intermediate expansion ratios.

Aside from the additional complexity (always a major fear in the aerospace business) there is the risk that wall discontinuities will trigger flow separation, specifically uneven flow separation, giving substantial (and random) side forces. Not good.  :(
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Offline cordwainer

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Re: Shape changing rocket nozzle.
« Reply #5 on: 07/27/2014 10:22 pm »
Here is an idea. Use the memory metal as an actuator for the movement of a dual skirted nozzle and make the individual skirts out of lamellared sections like some jet nozzles. Now run a sticky fuel rich mixture of methane, propane or butane through it and you have a highly "throttleable" vectored thrust thrust pulse jet/rocket motor. I think Bob Lizzard worked on something similar.(I think he's a bit of kook with his ET claims but his scientific and engineering credentials are real) Don't know how well it would work with a higher thrust lean air fuel mixture, though. Butane would make an excellent fuel for this since you could use it as both a bipropellant and monopropellant and it can be made to deflagrate as a monopropellant at high enough pressures. 

Offline Rocket Science

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Re: Shape changing rocket nozzle.
« Reply #6 on: 07/27/2014 10:55 pm »
The aerospike engine eliminated the need for a nozzle and compensated with altitude...

"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline Raj2014

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Re: Shape changing rocket nozzle.
« Reply #7 on: 07/28/2014 12:23 am »
NASA should continue research in Aerospike engine technology, since it has been over 13 years when the X-33 was cancelled if it is needed and start using them if they can. Also an aerospace company will be using aerospike engines for their rocket, Firefly Space Systems.   
« Last Edit: 07/28/2014 12:25 am by Raj2014 »

Offline JohnFornaro

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Re: Shape changing rocket nozzle.
« Reply #8 on: 08/20/2014 01:40 pm »
Hey!  Just noticed this thread, looking for something else.

To the OP:  Excellent idea.  Haven't read the thread, but there are extendible nozzles.  I'd like to think that the idea of a flexible nozzle profile  could be implemented.  no time now, but I'll be back.
Sometimes I just flat out don't get it.

Offline MP99

Re: Shape changing rocket nozzle.
« Reply #9 on: 08/26/2014 07:33 am »
I had wondered about shape memory alloys for vacuum optimisation of an SL engine with a fixed nozzle.

Engines cannot use a high area ratio at sea level, so a large nozzle requires a wide throat.

However, in vacuum this leaves some efficiency on the table, so make the throat of shape memory alloy, but at launch keep it below its transition temperature with heavy regenerative cooling.

Once in vacuum, allow the temperature to rise by reducing the cooling. The high temperature shape would reduce the throat area, so increasing the area ratio.

But, I don't think the resulting throat could be circular - maybe hexagonal with folds at the corners to "lose"  some of the larger circumference. The shape change would probably also screw with the regen cooling channels, and it would be critical to maintain those.

Cheers, Martin

Offline R7

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Offline ChrisWilson68

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Re: Shape changing rocket nozzle.
« Reply #11 on: 08/26/2014 09:36 am »
Obviously, all they need to do is send up a 3-D printer, and print a new nozzle while the rocket is flying. :-)

Offline Stormbringer

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Re: Shape changing rocket nozzle.
« Reply #12 on: 08/26/2014 11:52 am »
We used to call that occupational slot the inflight missile repairman.
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Offline aero

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Re: Shape changing rocket nozzle.
« Reply #13 on: 08/26/2014 03:50 pm »
We used to call that occupational slot the inflight missile repairman.

Automation taking over another career path.  :(
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Offline ThereIWas3

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Re: Shape changing rocket nozzle.
« Reply #14 on: 08/26/2014 03:59 pm »
Wouldn't hydraulic actuators be more reliable than memory-metal?  I am thinking of something like the tailpiece of some military fighter jets that have 'petals' that can squeeze the exhaust.  They would have to be pretty beefy though.

Offline RanulfC

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Re: Shape changing rocket nozzle.
« Reply #15 on: 08/26/2014 04:23 pm »
Wouldn't hydraulic actuators be more reliable than memory-metal?  I am thinking of something like the tailpiece of some military fighter jets that have 'petals' that can squeeze the exhaust.  They would have to be pretty beefy though.

"Turkey Feather" nestled variable exhaust nozzles:
http://www.projectrho.com/public_html/rocket/realdesigns.php
("Thrust Diverters" and continue with "Cascade Vanes" below it)

They are much heavier and more complex (costly) than a "simple" nozzle extension but I'd still suggest a plug or aerospike nozzle as the best choice.

Randy
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Offline JohnFornaro

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Re: Shape changing rocket nozzle.
« Reply #16 on: 08/28/2014 12:25 pm »
From the site that Randy posted:

Quote
In the Sol departure phase, a battery of orbital lasers illuminates a 16 kilometer diameter photon sail attached to the ship's nose (sail not shown)

What's a "photon sail", exactly?  A light sail by a cooler sounding name?

There's also a "matter-antimatter" engine, for the coast time to Alph Centauri.  The top of the page has the web author stating , "The good starship ISV Venture Star from the movie Avatar is one of the most scientifically accurate movie spaceships it has ever been my pleasure to see".  Bit of a struggle for me to accept not the science, but the existence of that engine.   Certainly "Dr. Pellegrino is one of the worlds greatest living experts on the Titanic", but it's rather a stretch to parley that expertise into interstellar spacecraft design.

Anyhow, those engines "burn for 0.46 year, producing 1.5 g of thrust, thus braking the ship from a velocity of 70% c to zero". 0.7c, huh?

The site is still chock full of interesting stuff.  Moving on to Thrust vectoring...

The first thing that came to my mind was the "turkey feathering" trick, used on some jets these days.  It was interesting to me to study the adjustable "plug nozzle" design.  I also liked the idea of a magnetic nozzle.
Sometimes I just flat out don't get it.

Offline Jet Black

Re: Shape changing rocket nozzle.
« Reply #17 on: 08/28/2014 02:57 pm »
The aerospike engine eliminated the need for a nozzle and compensated with altitude...



firefly are working on this now:

http://www.fireflyspace.com/
For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled. -- Richard Feynman

Offline Stormbringer

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Re: Shape changing rocket nozzle.
« Reply #18 on: 08/28/2014 03:53 pm »
From the site that Randy posted:

Quote
In the Sol departure phase, a battery of orbital lasers illuminates a 16 kilometer diameter photon sail attached to the ship's nose (sail not shown)

What's a "photon sail", exactly?  A light sail by a cooler sounding name?

There's also a "matter-antimatter" engine, for the coast time to Alph Centauri.  The top of the page has the web author stating , "The good starship ISV Venture Star from the movie Avatar is one of the most scientifically accurate movie spaceships it has ever been my pleasure to see".  Bit of a struggle for me to accept not the science, but the existence of that engine.   Certainly "Dr. Pellegrino is one of the worlds greatest living experts on the Titanic", but it's rather a stretch to parley that expertise into interstellar spacecraft design.

Anyhow, those engines "burn for 0.46 year, producing 1.5 g of thrust, thus braking the ship from a velocity of 70% c to zero". 0.7c, huh?

The site is still chock full of interesting stuff.  Moving on to Thrust vectoring...

The first thing that came to my mind was the "turkey feathering" trick, used on some jets these days.  It was interesting to me to study the adjustable "plug nozzle" design.  I also liked the idea of a magnetic nozzle.

the venture star was based with almost perfect fidelity on a real design study for a type of antimatter rocket known as a tethered beamed core design. it's tether approach saves so much mass that it has a top end of .92 C even before you get to later developments on optimized magnetic nozzle designs since those were not calculated until years later.
(the real design) not the movie.

the movie had semi realistic radiators and instead of a tether they went with a rigid truss but other than that the design was fairly true to the inspiration ship design.
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Offline RanulfC

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Re: Shape changing rocket nozzle.
« Reply #19 on: 08/28/2014 04:13 pm »
From the site that Randy posted:

Quote
In the Sol departure phase, a battery of orbital lasers illuminates a 16 kilometer diameter photon sail attached to the ship's nose (sail not shown)

What's a "photon sail", exactly?  A light sail by a cooler sounding name?

A Photon Sail is considered a specific type of light-sail in that its designed and built to use laser light instead of 'standard' light.

Quote
There's also a "matter-antimatter" engine, for the coast time to Alph Centauri.  The top of the page has the web author stating , "The good starship ISV Venture Star from the movie Avatar is one of the most scientifically accurate movie spaceships it has ever been my pleasure to see".  Bit of a struggle for me to accept not the science, but the existence of that engine.

The AM engine described has a lot of research behind it and is based on the AM catalyzed fusion drive described in the engine section of the webpage. The "Valkyrie" starship design has been the subject of several papers and is a pretty well known and accepted way of getting around some of the mass constraints on an interstellar vehicle. See:
http://www.projectrho.com/public_html/rocket/slowerlight.php#valkyrie

Robert Forward verified the math on both the AM-Cat-Fusion and even a pure AM rocket. The major obstacle of course is producing that much AM :)

Quote
Certainly "Dr. Pellegrino is one of the worlds greatest living experts on the Titanic", but it's rather a stretch to parley that expertise into interstellar spacecraft design.

He's also a sci-fi author and it was his expertise on the Titanic which first put him in touch with James Cameron :)

Anyhow, those engines "burn for 0.46 year, producing 1.5 g of thrust, thus braking the ship from a velocity of 70% c to zero". 0.7c, huh?

Quote
The site is still chock full of interesting stuff.

Boy-n-howdy and how :) I have to keep checking it from end to end ever couple of weeks or I miss a lot :)

RAndy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

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