h a l f b a k e r yMake mine a double.
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I was thinking about rocket casing. Along for the ride, that casing is. Yes yes it contains important rocket innards. But is there no way to make a rocket casing do more work?
I propose that the casing be used as a heat reservoir. By doing so one could obviate the need for fuel, which is expensive
and gets used up. On the ground, the iron casing will be heated to glowing with an induction current. A ceramic insulating shell over this will reduce heat loss to the exterior air.
An air intake in the rocket front is attached to a screw which traverses the interior length of the hollow rocket. This screw and intake is spun up with a hand drill.
The longitudinal screw divides the rocket interior into sections. Air enters the top and as it progresses downwards, turns the screw and also increases in volume as it heats. The divisions along the screw prevent expanding air from leaving back through the top and preventing further air ingress.
At the bottom of the screw, the air is now very hot and is expelled thru the rocket nozzle, propelling the rocket upwards.
This rocket can be recovered, heated back up and launched again.
I would like for this rocket to have no moving parts but I cannot think of a better way to do this than the screw.
Air-augmented rocket
http://en.wikipedia...ir-augmented_rocket
Similar to what [NRM] described [Custardguts, Nov 06 2014]
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OK. Where does one begin? |
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Can I suggest some elementary maths? |
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I think I will suggest some elementary maths. Go do
some elementary maths. |
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Pretty sure this is a jet, not a rocket. |
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Also pretty sure that the total amount of heat that can
be contained in an metal casing is significantly less than
the fuel that can be carried, for the same weight, in a
lighter casing. |
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Iron - Specific Heat: .45 J/C*g, Melting Point: 1538 C |
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So, assuming a starting point just a few degrees below
melting (not a safe assumption, Iron softens before it
melts), and an ending point at 0C, a gram of casing
material can carry 692.1 J. Or 1/62 of the energy of jet
fuel. Therefore, you're better off with a lighter casing
with a fuel tank. |
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[MechE], please don't shout the answers out - I was
asking [bungston]. And [8th] - don't think I can't see
what you're doing at the back there. Put the cat
back in your desk and give [MechE] back his
compasses. |
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Didn't see your post until I hit submit on mine. Took me a
bit to look up the numbers. |
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Ooh, if you built the shell and screw from Fullerene, then sections of the shell could be Fresnel lenses which could heat the screw to thousands of degrees and continue to generate heat while in flight. |
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I am ashamed to say that although I more or less understand the concept of specific heat I am unable to apply this mathematically. MechE I am grateful that you can. Thank you! |
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I speculate about other materials which can get hotter / retain more thermal energy but none will be enough better to equal jet fuel. |
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But few things have as much energy as jet fuel. Few people are as beautiful as supermodels. Let us consider this idea in itself, not compared to the platonic form. Could a jet based on this principle (hot tube with an interior screw) even throw air out the back? |
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Could a supermodel based on this principal (hot tube with an interior screw) even throw air out the back? |
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//supermodel based on this principal (hot tube with an interior screw) |
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As to using heat, refers to own idea about ramjet-type airduct that goes over the rocket combustion chamber...presumably filed in Nasa's crank mail pile sometime circa 2003. |
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//ramjet-type airduct that goes over the rocket combustion chamber// |
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Have you read up on air-augmented rockets? They're like a hybrid rocket/ramjet, where the rocket exhaust feeds a ramjet. In that heat is transferred with the exhaust products, I think it does what you describe with the added benefit of already being developed. See link. In use on some of the latest-gen missiles in development and in use. |
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As to the idea, I very much doubt that stored thermal energy could possibly compete with stored chemical energy in the form of fuel, certainly not on a per-weight basis. And no, I doubt you could do much without moving parts, although I would look into valveless pulse-jets for inspiraiton. Perhaps a very low frequency resonance could be set up with a large pulse jet with chambers optimised for heat transfer from the chamber walls to the charge air. Might work for a handful of cycles before it cools down too much to work. Lots of work was done in the 60's on nuclear aircraft propulsion, some of which would be applicable to your concept. The problem is one of energy density. All of the work I found and read up on relied on an external heat source (an onboard nuclear reactor) used to provide the heat for an otherwise conventional jet engine concept. |
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Dammit, there's a queue outside that time machine, with all the people going back in time to think of my ideas before I have... |
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On the other hand, research into Soviet missile programs confirm that smoking can be good for your health, Nedelin missile disaster.. "....Mikhail Yangel and test range commanding officer survived only because they had left to smoke a cigarette behind a bunker" |
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(holds out hand for tobacco industry slush money) |
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//Elementary maths// Basic math, yes, basic. As basic as
cow hydroxide. |
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<leans on desk lid to try and suppress sound of yowling and
scratching from within> |
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<looks furtively around to see if anyone has noticed> |
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As to the idea, "what everyone else said". It's a sort of ramjet,
not a rocket. And one of the benefits of a rocket is that as the
fuel is consumed, the overall mass of the system decreases,
giving greater acceleration for the same thrust. This design
neatly avoids that advantage. |
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phosphorous...if you made the casing out of phosphorus...just thinking aloud mind you.. |
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I can see how it might make the Soviet Nedelin missile disaster look like a mere firecracker, and extra hydrogen, and pusher plates made out of fulminate of mercury.... |
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I was thinking metallic sodium. If the sodium is
heated to a very high temperature (as in this idea),
then the humidity in the air is more likely to react,
but there may be a small enough moisture content
that it won't explode violently, just help maintain
the heat until it is eaten away. The problem is that
sodium still has less than a 3rd of the energy per
pound compared to jet fuel, which has about a 3rd
of the specific energy of hydrogen. |
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… caesium … caesium, and phosphorous … and hydrogen
peroxide … |
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Shouldn't waste heat be converted to charge to
effect molecular flow passing over the casing. Or
failing that, just very impressive front headlights. |
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//Could a supermodel based on this principal (hot
tube with an interior screw) even throw air out the
back?// I will not make a fart joke. I will not make a
fart joke. |
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