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.Īnyhow, 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". Bit of a struggle for me to accept not the science, but the existence of that engine.
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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". There's also a "matter-antimatter" engine, for the coast time to Alph Centauri. What's a "photon sail", exactly? A light sail by a cooler sounding name? It seemed to work and (in principle) could operate at intermediate expansion ratios.Īside 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.
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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.
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). There has been quite a lot of variable geometry nozzle designs.
Memory metal is sometimes called NiTiNOL so you're talking a Nickel Titanium alloy, which is promising from the PoV of high temperature resistance. 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.Įdit 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. Wikipedia is always a good place to start, Second question - What limitations do memory metals have that would preclude using it as described above? 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.įirst question - Does anyone know of efforts to make or research nozzle extensions made of memory metal? These high expansion ratio nozzles can be very long, and need a very long inner stage to contain them. The other problem of course is the length of the nozzle. 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 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. Next corrugate the memory metal of the nozzle extension lengthwise starting away from the attachment edge and to the nozzle exit. The concept is first, make a bell nozzle extension from memory metal. 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. But upper stage engines operating in vacuum have high expansion ratio which result in large diameter nozzles.
I have been looking at the size of upper stage rocket nozzles while considering using two of them together.