Non-Acoustic Horn Applications

[D-MAN]

Same capsule from the front - this version is not manned. The large "box" on the right side holds the parachutes when stowed. For scale, you can see a couple of "kosmonaut" feet/lower legs in a seat to the right side of the pic.

DM

[Jay481985]

With constant thrust from the rocket exhaust, the rocket will continue to increase in speed until the resistance force of the atmosphere levels it off. But this resistance of the air varies with density (elevation) and prevents one from using 100% at all altitudes. The shuttle, for example, does not use a constant throttle for its ascent. If you have ever listened to a shuttle launch, in the early part of the ascent the 'throttle' is backed off for a speed below 100% so that the ascent is slower during the part of the ascent in dense air. As it gets up higher into the thinner air, listen for the mission controllers to say, "Go for throttle up, 110%." This is done because the dynamic load of the lower atmosphere is so strong at these dense levels that a too high speed can be damaging to the craft, but as it gets up into the thinner air - no problem, and they allow speed greater than 100% sacrificing maximum efficiency for a safety margin to get up to orbital speed.

At lower altitudes the space ship must go slower not only cause the dynamic load, its done to prevent the rockets from stressing the vehicle and also its done to prevent the shockwaves from damaging the craft. This is sound shockwaves, remember guys this craft is around 180 db taking off, our atmosphere allows for 189 db tops and that amount of noise causes alot of windows to break and things shatter. They are worried about the spaceship breaking itself up while taking off. The higher the altitude, the less dense air is and since sound travels better in denser matter it slowly loses sound while traveling, in space there technically is no sound (its a vacuum) This is where Danley comes in with his super tapered horn subwoofer technology etc, they asked his help to determine the effects of sound on the space ship.

Also they throttle the rockets at full force since there is less gravity the higher you go, its like doing burnouts while trying to get best quartermile. Yeah you can give it the full throttle at the get go but your going to (lose traction in the car and spin your tires) or waste necessary fuel that can be used when your vehicle gets to proper speed or height. They rather use full throttle when gravity is not telling them to come back at sealevel, as opposed to 10 miles in the sky, also they lose weight as the secondary thrusters are jettison and use the main (red) fuel tank to get into orbit. The secondary rockets are actually recovered while the red fuel tank is burned up upon reentry (that was why the Nasa team really didn't care to much about falling foam prior to the Columbia disaster until they noticed that in big enough chunks it can do damage to the spacecraft)

As with the jet plane horn, I believe sprucewood is much stronger than metal for early planes, hence the wright brothers uses spruce wood, the spruce goose etc etc is cause spruce wood is superior to metal is strength per weight requirements. Metal just is more durable and less maintenance.

[Jay481985]

Those zany Russians! They built a golfball without any dimples!

Here's the question - why doesn't this tumble/rotate/fly all over in re-entry? Check out the burn marks...

DM

There is very little air up in reentry for it to tumble, air = the reason why ping pong balls and golf balls curve, hook, slice etc. Since its traveling around 14000 mph already it should be either spining if it was spining before or just move in a constant motion when it reaches space.

Oh btw I forgot which one but either the space shuttle or the the russian spacecrafts skip when they come back to earth. They skip across the atmosphere to reduce their speed like a rock skipped on water.

[Jay481985]

Sort of the reverse of a horn, this is a wind-tunnel model entirely of machined metal (these are about 6 feet tall and very beautifully made) used for testing the exhaust plume(s) of the space shuttle! Why the exhaust plumes need to be tested who knows?

Anyway that seems like an unbounded horn-like application (i.e., phase plugs).

DM

to be more efficent. You can have the plume do nothing for you or gain more efficency. Sorta like placing the plume eactly behind you so the engine exhaust can push off the plume. Since the smoke (oxymoron) is heavier than the air for a split second (the space ship uses hydrogen as fuel so you get watervapor, a hell of a lot on the terms of like billions of gallons while lifting off) you can have the ship push off the watervapor thus increasing efficency and not having to need more fuel so more payload for other essentials and scientific experiments.

[pauln]

So the question is, does the sprinkler turn? I think no...

Pauln

[pauln]

Those zany Russians! They built a golfball without any dimples!

Here's the question - why doesn't this tumble/rotate/fly all over in re-entry? Check out the burn marks...

DM

There is very little air up in reentry for it to tumble, air = the reason why ping pong balls and golf balls curve, hook, slice etc. Since its traveling around 14000 mph already it should be either spining if it was spining before or just move in a constant motion when it reaches space.

Oh btw I forgot which one but either the space shuttle or the the russian spacecrafts skip when they come back to earth. They skip across the atmosphere to reduce their speed like a rock skipped on water.

Now this is a good question. I think the craft would be subject to tumbling rotation unless something prevents that. Clearly something is do so... maybe they trail something behind, not so subtancial as a parachute? I would think that without any specific prevention, the heating up of the leading side of the sphere would cause an imbalance of pressure (or maybe the hot side actually creates a stabilizing effect?). Maybe it really does tumble and burn the surface on all sides, but when it lands in the snow, the bottom side gets "cleaned" of the burn marks?

By the way, you know that in the beginning of the space race the USA used chimps, the Russians used dogs. They had to quite using dogs because they kept poking their heads out the window with their tongues wagging in the wind during the re-entry phase.

[Jay481985]

most nasa and russian spacevessels used the tri parachute design when low enough to prevent it from spinning etc. I still think the lack of air during reentry inhibits tumbling. Just like a bullet does not spin unless the barrel is rifled. Smoothbore guns create no spin to give maximized force, spin decreases force but is subject to less crosswind effects and greater accuracy.

Also if the pod does spin, doesn't nasa and russians train for it using that antigravity 3 dimension spining device found at some carnivals?

[hwatkins]

most nasa and russian spacevessels used the tri parachute design when low enough to prevent it from spinning etc. I still think the lack of air during reentry inhibits tumbling. Just like a bullet does not spin unless the barrel is rifled. Smoothbore guns create no spin to give maximized force, spin decreases force but is subject to less crosswind effects and greater accuracy.

Also if the pod does spin, doesn't nasa and russians train for it using that antigravity 3 dimension spining device found at some carnivals?

I am interested in the reaction of this non dimpled thingy as well. Using the above bullet example - the reason barrels are 'rifled' is that the early weapon's bullets became dramatically irratic as soon as the propulsion effects wore off. In other words the bullet would turn into a knuckle ball and lose speed quickly and start a tumbling act. There is point where increasing velocity has limited effect on the distance accuracy of a flat trajectoried, non spinning object.

Now - that is all quite different if you decide on a parabolic trajectory. That may be more akin to reentry. There is much less of the knuckle ball effect comparatively when you use an arching shot (much like cannons). Rifling is still a great idea here as well, but you can manage greater distance and accuracy even when the ball is not spinning.

[DrWho]

I thought the shape of spacecraft upon reentry had to do with the

insane heat from the friction with the atmosphere and the insane speed

the craft is travelling. They talked about it at the Houston Space

Museum or whatever they call it...I remember them talking about some

fancy method of stabalization and how they have a 3 degree angle of

error upon reentry. Too steep and they melt to death, too shallow and they bounce

off the surface.

[Jay481985]

I am interested in the reaction of this non dimpled thingy as well. Using the above bullet example - the reason barrels are 'rifled' is that the early weapon's bullets became dramatically irratic as soon as the propulsion effects wore off. In other words the bullet would turn into a knuckle ball and lose speed quickly and start a tumbling act. There is point where increasing velocity has limited effect on the distance accuracy of a flat trajectoried, non spinning object.

That was when people still made their own bullets. As bullets became more refined the need for less rifling happened. Not as deep grooves to cut into the bullet upon shooting as the bullet became machined and better toleranced.

Also the limited effects on distance accuracy of a flat trajectory, non spinning object, does that account for gravitational loss? If so, that's that reason why.

Now - that is all quite different if you decide on a parabolic trajectory. That may be more akin to reentry. There is much less of the knuckle ball effect comparatively when you use an arching shot (much like cannons). Rifling is still a great idea here as well, but you can manage greater distance and accuracy even when the ball is not spinning.

In the near future, when rail guns become cheaper and more problems are solved, rifling will become obsolete due to the nature of a rail gun. There is no real barrel and going around mach 14 out of the rails and what the navy says has a range of upto 500 miles is quite impressive. Also a hell of alot cheaper than tommahawk cruise missles with the ability to have precise bombing if the shell has guidance control.

[pauln]

My guess is that the spherical re-entry vessel becomes stable during descent because the super hot surface of the leading face becomes 'slippery' with a layer of super heated air whereas the sides are cooler and provide more drag. This would establish a natural self correct ion to any rotation because the presentation of a cooler surface toward the leading edge would be 'pushed back' - in essence a control system using negative feedback. Once the leading edge got hot, it would tend to be the preferred part of the surface to present to the head-on air. This is similar to the dihedral angle of wings on an airplane (the way they angle slightly upwards in a slight 'V' shape as viewed from head on) so that any displacement of one wing being higher than the other (like in a banked turn) causes the lift component vector of the upper wing to be angled away from the alignment with the vertical opposing gravity force, while flattening the other wing to increase the same alignment, thereby increasing the vertical conponent of lift in the lower wing and decreasing the vertical component of lift in the upper wing so as to tend to bring the plane back to flat flight. Again, a negative feedback control system. It shows up everywhere, except in my SET amps!

Paul

Now how about that spinkler question???

[Jay481985]

although american made and different shape, America used retro rockets:

"

Reentry

At the time of reentry, the spacecraft would be maneuvered to the appropriate

orientation and equipment adaptor section would be detached and jettisoned,

exposing

the retrorocket module. The retrorockets consisted of four

spherical-case

polysulfide ammonium perchlorate solid-propellant motors

mounted near the center of

the reentry adaptor module, each with 11,070 N

thrust. They would fire to initiate

the spacecraft reentry into the

atmosphere, with attitude being maintained by a

reentry control system of 16

engines, each with 5.2 N thrust. The retrorocket

module would then be

jettisonned, exposing the heat shield at the base of the reentry

module.

Along with the ablative heat shield, thermal protection during reentry was

provided by thin Rene 41 radiative shingles at the base of the module and

beryllium

shingles at the top. Beneath the shingles was a layer of MIN-K

insulation and

thermoflex blankets. At an altitude of roughly 15,000 meters

the astronauts would

deploy a 2.4 meter drogue chute from the rendezvous and

recovery section. At 3230

meters altitude the crew releases the drogue which

extracts the 5.5 meter pilot

parachute. The rendezvous and recovery section

is released 2.5 seconds later,

deploying the 25.6 meter main ring-sail

parachute which is stored in the bottom of

the section. The spacecraft is

then rotated from a nose-up to a 35 degree angle for

water landing. At this

point a recovery beacon is activated, transmitting via an HF

whip antenna

mounted near the front of the reentry module."

http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1965-024A

[Jay481985]

another good website

http://www.russianspaceweb.com/soyuz.html

with detailed pictures

and the reason why the spacecraft does not spin out of craziness

Julian

Allen pioneered and developed the Blunt Body Theory that made possible

the heat shield designs that were embodied in the Mercury, Gemini, and

Apollo space capsules, enabling astronauts to survive the fiery reentry

into the Earth's atmosphere. A blunt body produces a shockwave in front

of the vehicle-visible in the photo-that actually shields the vehicle

from excessive heating. As a result, blunt body vehicles can stay

cooler than pointy, low-drag vehicles.

Credits - NASA

I guess the blunt body theory that has the shockwave in front also prevents the craft from rotating

http://www.centennialofflight.gov/essay/Evolution_of_Technology/reentry/Tech19.htm

hmm more interesting facts from the website

By 1956, some

researchers were noticing that reinforced plastics had proven more

resistant to heating than most other materials. They proposed using

these plastics in the inlets of supersonic cruise missiles. GE

engineers realized that they could use this same technique. They could

coat the reentry vehicle with a material that absorbed heat, charred,

and either flaked off or vaporized. As it did so, it took away the absorbed heat.

The key was

selecting the right material. Ultimately, they decided upon a phenolic

resin plastic. They decided to use a nylon cloth impregnated with the

phenolic resin and molded into the needed shape. Eventually, this and

similar materials were used to coat the surfaces of nuclear missile

warheads.

isn't phenolic resin plastic used in the making of the Synergy F series cones??? hmm space age material klipsch uses []