Caseless, nozzleless rocket

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sevenperforce
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Caseless, nozzleless rocket

Postby sevenperforce » Thu Sep 03, 2015 3:31 pm UTC

Was browsing old patents and came across this one:

US Patent 4,170,875A: Caseless rocket design

Is a caseless solid-fueled rocket possible? Apparently so. Since a picture is worth a thousand words:

caseless.png

A caseless solid-fueled rocket intended for use in an air-launched missile was envisioned. Basically, a fuel-rich solid rocket propellant body is designed to burn from the outside in, with a trailing body shockwave serving as a virtual combustion/expansion chamber. The latter part of the design seems to have a lot in common with an aerospike rocket nozzle.

Staged rocket designs are useful because you need big engines with a lot of thrust at the beginning in order to get your rocket off the ground, but as you gain altitude and speed it becomes more efficient to dump your first set of engines along with the rocket casing and use a second engine (or set of engines) to continue accelerating with now-reduced weight. That makes good sense, but it's wasteful.

However, if you could design a mass of propellant such that it burns away from the outside-in, effectively forming its own inside-out nozzle, then there is no need to dump engines or casings because the burn process itself does the work for you, lowering weight and even gradually decreasing thrust. Even more advantageously, an outside-in burn allows atmospheric air to function as part of your oxidizer, increasing your specific impulse by decreasing the amount of oxidizer you have to carry.

To take off from a standstill, of course, you'd need some sort of initial nozzle and shroud. But that might be achievable by varying binder levels to allow a portion of the propellant to function as a burn-away shroud during the initial launch, at least until the rocket reached high enough speeds to function as a burn-in design:

caseless 2.png
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Tyndmyr
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Re: Caseless, nozzleless rocket

Postby Tyndmyr » Thu Sep 03, 2015 3:42 pm UTC

*shrug* Looks like on the lower one, the slower burning propellant is acting like your case/nozzle. Which I guess could work, in theory, as long as your burns happen very precisely.

The top one, the payload isn't in front, it's in the center of the propellant. That seems just frigging odd.

Sure, you can have stuff blast off without a case or nozzle, but...there are good reasons why those components exist. On say, staged space boosters, the vast, vast majority of each stage is propellant. It seems like say, removing a nozzle would kill your efficiency far, far more than the saved weight would help. I mean...if that were not the case, we'd just not be using nozzles to begin with.

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sevenperforce
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Re: Caseless, nozzleless rocket

Postby sevenperforce » Thu Sep 03, 2015 4:20 pm UTC

Tyndmyr wrote:The top one, the payload isn't in front, it's in the center of the propellant. That seems just frigging odd.

Yes, it does. I'm not sure what the point was there.

Looks like on the lower one, the slower burning propellant is acting like your case/nozzle. Which I guess could work, in theory, as long as your burns happen very precisely.

You can have stuff blast off without a case or nozzle, but...there are good reasons why those components exist. On say, staged space boosters, the vast, vast majority of each stage is propellant. It seems like say, removing a nozzle would kill your efficiency far, far more than the saved weight would help.

The idea is that you only need a nozzle until you have enough airspeed for a virtual aerospike nozzle to form. Come to think of it, you don't really need that full nozzle design; you just need an annular aerospike:

caseless 2.png
caseless 2.png (8.3 KiB) Viewed 1869 times

As soon as you pass about Mach 0.8, you start get a shockwave and you no longer need any casing at all. With the right geometry, there's no loss of efficiency (that's the beautiful thing about an aerospike) and you get to supplement your oxidizer with atmospheric air.

With the right geometry you have function approximating a virtual sc/ramjet:

caseless 3.png
caseless 3.png (7.06 KiB) Viewed 1869 times

KittenKaboodle
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Re: Caseless, nozzleless rocket

Postby KittenKaboodle » Thu Sep 03, 2015 10:50 pm UTC

sevenperforce wrote:Was browsing old patents and came across this one:

US Patent 4,170,875A: Caseless rocket design

To take off from a standstill, of course, you'd need some sort of initial nozzle and shroud.


Or one could follow the suggestion of the patent: "To provide the supersonic velocity required by rocket 10 of this invention, a cannon or gun launching technique could be employed."

Also:
"The ordnance of the rocket is preferably carried within a hollow center section 14 in FIG. 1. In this design protection to the ordnance package is provided by the surrounding propellant and an ablative or insulating material on the ogive frontal section is not necessary"

Remember this is a weapon, it is not intended for, for example, taking people to Mars. More specifically is seems like the inventor has anti-aircraft missile in mind, hitting an aircraft with a supersonic chunk of burning rocket propellant is not entirely contradictory to the objective in that case (but against say a tank, or if your payload is nuclear, it is a bit of a waste of fuel, but as the inventor says, you probably need something for a shield anyway).

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scarecrovv
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Re: Caseless, nozzleless rocket

Postby scarecrovv » Fri Sep 04, 2015 5:09 am UTC

It's an interesting idea, but I don't see any guidance system. This is going to be wildly inaccurate unless there is something I missed (I admit to not giving the patent more than a cursory glance).

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sevenperforce
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Re: Caseless, nozzleless rocket

Postby sevenperforce » Fri Sep 04, 2015 3:05 pm UTC

The payload itself probably has a glide-guidance system of some kind. This might be better used for air-to-surface attack than air-to-air.

In a larger application, however, a caseless rocket could be used as the first stage of a launch vehicle with its own integral engines. The caseless rocket burn is self-staging and thus produces the ideal boost profile to get up to near-orbital speeds.

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Neil_Boekend
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Re: Caseless, nozzleless rocket

Postby Neil_Boekend » Sat Sep 05, 2015 10:40 am UTC

Assuming the things are cheap you could use a machine gun tactic, ie shoot enough of them to hit the target anyway, or use the more advanced Goalkeeper tactic, shoot at the target, follow the projectiles by radar to measure wind, target motion and other error inducing factors and then re-aim the gun so the trajectory of the bullets and the target intersect (with 4200 tungsten core 30 mm rounds a minute of course).
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