Like a hot melt glue gun stood on end
... with the payload on the top of the glue stick? Doesn't that mean that the rocket gets shorter as it burns, that must give some interesting aerodynamic problems.
Scottish boffins, along with colleagues in Ukraine, have developed a "self-eating" rocket engine that could affordably fling a cubesat into orbit. The solid-fuel rocket does away with heavy tanks, with the propellant itself forming much of the launcher's structure. As the engine burns its way through that structure, the rocket …
>> interesting aerodynamic problems. <<
Possibly not too many, the aerodynamic impact will lessen rapidly with altitude and thrust gimballing will become more important. CoG will stay somewhere in the middle between the converging motor & payload.
Having the fuel sufficiently stiff to survive launch stresses does sounds like a new rocket problem though.
For small rockets no payload separation system may be needed, the spent motor can just ride along until the whole thing drops out of orbit.
" The problem of directing the thrust thus produced, and avoiding also combusting the payload, has however proven hard to solve."
This rocket has a relatively conventional combustion chamber with convergent (and, in practice -divergent) nozzle to direct the thrust in the usual way. Steering also needs adding, as it does for any rocket, and is a mature technology. A non-combustible stub between the payload and the fuel rod should protect the former from combustion.
But sending a plastic spear through an oxygen-rich atmosphere at high Mach number may prove less practicable.
"But sending a plastic spear through an oxygen-rich atmosphere at high Mach number may prove less practicable."
It's not a bug, it's a feature, though probably only for version 2.
You add some inlets to your device, figure out the amount of oxygen available to you at different points in the flight, and so reduce the amount of oxidant needed in your stick at those points (as measured up the stick).
<iI love the $5 multimeters in the picture</I>
Ha Ha - that's the first thing that struck me about the picture too, but I didn't like to say until someone else mentioned it!
I hope they've patented the tech so that they can capitalize on it in a few years - micro satellites and micro rockets are the future! (Well, some of it).
I hope they've patented the tech so that they can capitalize on it in a few years - micro satellites and micro rockets are the future!
You don't think that MoD will be thinking how they can muscle in, seize and monopolise the technology, exclude all beneficial and commercial applications, and turn it into a multi-billion quid failed weapon system? Just like they did with Reaction Engines.
No casing? I don't see how you could provide the needed shove to get the rod into the engine without some form of supporting structure. And you need a place to put the electronics and payload. It might not be the traditional sort of motor casing associated with a solid fuel motor that has to withstand the full operating pressure over it's entire length, but I'd still call it a motor casing.
Well there are a few options to avoid the weight of a casing.
One is to pull the top part toward the bottom with a pair (or three) of winches.
Another is to have no "top" and mount everything around the chamber, with rod being fed in by a pair of pinch rollers.
It's one of those "That's so obvious, why did no one else do it before" ideas.
But I don't think anyone has. Keeping the oxidizer from the fuel would in principal make for safer propellant.
On a flight dynamics basis I think that (unlike conventional solids) the shortening compensates for the mass loss so the CoG (roughly) stays in the same position, potentially making the control problem a bit simpler. Maybe.
outer casing made of self lubricating plastic. How about a simple coarse thread in plastic above reaction chamber where plakki still firm and rotate a feeder nut ? I do wonder how any non-metal or ceramic will handle the upper chamber combustion pressure no matter what method is used. Concept is worth playing with.
The bottom of the stick is being melted by the heat of the combustion chamber. Some downward force is applied by the upward acceleration of the rocket. This is "mg" just prior to launch, when the stick is heavy, is slightly larger when the engine starts or else it won't lift off, and remains at that slightly larger value throughout the flight as long as you are burning the stick at a uniform rate. Note also that the thrust is constant even as the stick gets lighter, so the actual acceleration is presumably pretty huge near the end of the burn. Probably not person-friendly. Stick to cube-sats.
The cube-sat itself might reasonable be placed at the other end and be given a heat-resistant beanie to wear for the flight, thereby reducing the problem (mentioned further up) of firing an inflammable stick through oxygen at high Mach numbers. I imagine the sides of the stick would see less atmospheric friction and might be protected by a thin layer of something air-tight.
When will the Chinese run a high speed maglev rail launcher up the side of the Himalayas ? See end of "The Moon is a Harsh Mistress". Aside from that Shadow*, orbital or close missiles have been launched from under planes for years. Merkins sat killer was launched from an F15. Orbital Sciences also come to mind.
Given the sort of market this "hobby" rocket is aimed at, the cost of aerial boost is high and one can be sure aviation/space management will be anxious to control anything likely to go near low earth orbit, let alone higher.
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