Are there any rocket scientists here?

Elind said:
You are right of course, the energy has to go somewhere, but let's separate the different components you mention.

An object that winks into existence at rest above a point on the earth where the atmosphere just starts, (orbiting at the same speed as the earth's spin at that height), would fall straight down at an accelleration of G (a little less at that altitude initially). That potential energy can be dissipated through parachutes or wings as is done every day, and was done by Spaceship One.

The problem is to dissipate the orbital kinetic energy in a manner that limits the heat buildup. That means do it more slowly and avoiding the denser air while above a certain speed.

For the sake of visualization, let's also not consider something the size of the space shuttle, but a smaller scientific satellite, say a couple of hundred pounds, or an emergency capsule with one human in it.

Could that not conceivably be maneuvered at the edge of the atmosphere, dissipating kinetic energy just like the slower speed objects lower down, but at a low enough rate to avoid the burnup problem?

As to how to do it; wings, or body shape will always be optimized for certain speed or density ranges, which is probably impossible for these ranges. Even if one used the "skipping" stone concept, it would probably fail at a lower altitude when the speed is still very high, for any fixed shape; but what of a variable geometry or a combination of "parachute" and wings?

I'm suggesting that it is theoretically possible, but perhaps technically too difficult to control under conditions of little margin for error, but I'm not sure.
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The whole idea to all this being?...to shed the weight of the heat tiles? To simply change the way for sake of change? Whatever though....

Could you imagine something happening to the speed descent that went wrong and you hear the astronaut's voice from mission control going, "I think it's gettin warm in here. Um...HELLLLLOOOOOOO! It's getting HOT in here!!! Um...HELLLLLLLLOOOOOOOOOOOOO? Did someone leave a light bulb going in this orbiter with moths inside?..I think I smell...God DAMN is it getting H....aeeiiiieieeieieieiei (last words. )
 
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Elind said:
After all a lot of smart people have thought about this already, but on the other hand they didn't come up with Burt Rutan's ideas earlier either.
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And after all.......they never came up with the shake-a-light until now either. You know...that Farraday's Law of Indurctioin flashlight they are selling on tv and that you can buy in stores? I have one. My brothrr-in-law bought 6. Ecman bought 4 (he gave me one for Christmas). I bet they are going to sell millions of these and bankrupt Eveready! :) How the hell do people come up with stuff that they should have come up with years ago? Why Can't *I* come up with something like this. I could be in Auba (I take that back) on the beach, having Mai Tais. :)
 
rwguinn said:
I think I'm going to call "Troll" on this one.
Elind can't seem to see that you can't "Stop" an object in orbit at a location over the earth: every bit you slow down drops the orbit; He/she/it also can't see that the shedding of hundreds of mJ of energy is essential to de-orbiting; he/she/it has a very limited mis knowledge of basic physics.
He/she/it needs to do some reading.
I'm done.
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Please don't go. Not unless you can come up with an equally tantalizing thread we can visit. :) Something like...Can light skip off a flat black object? :)
 
rwguinn said:
I deal with energy and momentum on a daily basis. The understanding has become second nature. That does not mean I can communicate it to someone without the basic knowledge to build upon.
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What do you do then? Manage demolition derbys?

You get your kicks lecturing people with your "second nature", without understanding anything different. I have a degree in engineering and several patents in mechanical and electrical devices. I don't remember too much about fluid dynamics, but I know that what you spout is self serving only. Why don't you leave this thread and we will see if any others still wish to contribute ideas?
 
Iamme said:
And after all.......they never came up with the shake-a-light until now either. You know...that Farraday's Law of Indurctioin flashlight they are selling on tv and that you can buy in stores? I have one. My brothrr-in-law bought 6. Ecman bought 4 (he gave me one for Christmas). I bet they are going to sell millions of these and bankrupt Eveready! :) How the hell do people come up with stuff that they should have come up with years ago? Why Can't *I* come up with something like this. I could be in Auba (I take that back) on the beach, having Mai Tais. :)
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All good ideas are simple in retrospect, but you have to remember that unless it's something we can continue to live without it is a whole different task to figure out how to make it, fund it, market it and price it so relatives will buy you one for Xmas.

This is one whose time has come with development of high intensity/efficiency LEDs, which we will be seeing much more of yet. The rest of the design is the only part that has been around for a while.
 
Iamme said:
The whole idea to all this being?...to shed the weight of the heat tiles? To simply change the way for sake of change? Whatever though....
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As in, If it ain't broke, don't fix it?

I think I've said that there may not be a more cost effective way to do this than is already being done.

The question, to rephrase again, is simply whether or not it is technically feasible to design a reentry method that would eliminate the heat problem to the vehicle, other than doing it with large retro rockets and fuel?

Even if such a solution would be less cost effective, it would still be interesting to consider how it could be done.

Some experts in momentum have seemed to suggest that all the reentry deceleration energy is first absorbed then reradiated by current space vehicles (the Space Shuttle does not have an ablative system). That is not correct.
 
Elind said:
What do you do then? Manage demolition derbys?

You get your kicks lecturing people with your "second nature", without understanding anything different. I have a degree in engineering and several patents in mechanical and electrical devices. I don't remember too much about fluid dynamics, but I know that what you spout is self serving only. Why don't you leave this thread and we will see if any others still wish to contribute ideas?
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One of the best stress engineers I ever knew was also an adamant "Flat Earther"
 
Elind said:
The question, to rephrase again, is simply whether or not it is technically feasible to design a reentry method that would eliminate the heat problem to the vehicle, other than doing it with large retro rockets and fuel?
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The slow reentry solution actually predates the plunging reenty with abalative or refractive heat shield. Herman Oberth in the 1920's suggested the use of a winged reentry vehicle with low wing loading that would return from orbital speeds gradually. Temperatures would be low enough for existing structural steel to tolerate.
Later Von Braun designed a series of reusable vehicles that used the same technology. A good example is the 1952 design seen in the Colliers magazine series, and the books derived from it "Across the Space Frontier" and "Conquest of the Moon". The Encyclopedia Astronautica has several good entries, see http://www.astronautix.com/lvs/vonn1952.htm .
The X-20 Dynasoar was similar in that it was a slow reentry vehicle that radiated heat fast enough for the structure (in this case titanium and K-monel metals) to tolerate without shielding.
The current reentry vehicles are descendents of the space race. While theoretically superior, the slow reentry, hot structure vehicle was harder to develop than the baistic reentry vehicle. In 1960 much work had already been done on balistic missile reentry vehicles, this knowledge base could be applied directly to the early space capsule design. The work done on Mercury and Vostok was then applied to later veicles and so on.
Some of the new generation of commercial spacecraft designs are going back to the slow reentry pattern. The veihicles are more challenging to develop, but they show promise of having longer service lives and shorter turnaround times. Both these factors are important for the commercialization of spaceflight.

Robert Klaus
 
Pope130 said:
The slow reentry solution actually predates the plunging reenty with abalative or refractive heat shield. Herman Oberth in the 1920's suggested the use of a winged reentry vehicle with low wing loading that would return from orbital speeds gradually. Temperatures would be low enough for existing structural steel to tolerate.
Later Von Braun designed a series of reusable vehicles that used the same technology. A good example is the 1952 design seen in the Colliers magazine series, and the books derived from it "Across the Space Frontier" and "Conquest of the Moon". The Encyclopedia Astronautica has several good entries, see http://www.astronautix.com/lvs/vonn1952.htm .
The X-20 Dynasoar was similar in that it was a slow reentry vehicle that radiated heat fast enough for the structure (in this case titanium and K-monel metals) to tolerate without shielding.
The current reentry vehicles are descendents of the space race. While theoretically superior, the slow reentry, hot structure vehicle was harder to develop than the baistic reentry vehicle. In 1960 much work had already been done on balistic missile reentry vehicles, this knowledge base could be applied directly to the early space capsule design. The work done on Mercury and Vostok was then applied to later veicles and so on.
Some of the new generation of commercial spacecraft designs are going back to the slow reentry pattern. The veihicles are more challenging to develop, but they show promise of having longer service lives and shorter turnaround times. Both these factors are important for the commercialization of spaceflight.

Robert Klaus
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I really appreciate that. If you have any more relevant links I'd be grateful, and I'll do a little more thorough searching myself.

Unfortunately however, you may have genuinely ended the thread. It was getting interesting, sort of ;)
 
I'm sorry I couldn't contribute much to this thread. When I was at university, I was interested in slow-speed aero and orbital mechanics, but not the bit inbetween :)
 
Elind - I think the reentry speed is too great to sufficiently slow it down in time to keep it from burning up FIRST. At about the time your skipping part would take hold, due to sufficient enough (a prerequisite) atmosphere, would be about the time things would start heating up, I'm afraid. Not cherry red yet, but sufficent to cause damage unless there were tiles.

With your plan, one could envison giant wings folding out. But by the time the wings could cause it to fly, there would be so much speed that the unprotected wings might start to warp due to heat. And if there wasn't that heat, then probably there isn't enough atmosphere, either. Sort of a catch-22.

The forward angular momentum carrying the ship into the atmosphere could not be deviated enough to overcome that inertia, I don't think. I think you have to better envision what it be like to truly alter the path of something entering the atmosphere at thousands of miles an hour, and what counteracting forces would be needed. And of course, have a ship designed that is practical (i.e., 1 acre size wings wouldn't cut it) I don't think there is enough counteracting force in the weaker atmosphere to cause deviation enough, or slowing down of the craft enough. I could be wrong, but it is what I think, when I close my eyes and envision this plan of yours.
 
Elind said:
I really appreciate that. If you have any more relevant links I'd be grateful, and I'll do a little more thorough searching myself.

Unfortunately however, you may have genuinely ended the thread. It was getting interesting, sort of ;)
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Elind,
An excellant place to start would be Sven Ninfingers' page, see:
http://www.ninfinger.org/~sven/models/models.html
The first bit is about spacecraft modelling (which is how I found it in the first place). Scroll down to the bottom of the page and you will find a batch of links to astronautical science sites. The NASA history office link is quite good. MARS.org "Lost Dreams" is also interesting, in fact all of them have some interest. Enjoy.

Robert Klaus
 
Pope130 said:
Elind,
An excellant place to start would be Sven Ninfingers' page, see:
http://www.ninfinger.org/~sven/models/models.html
The first bit is about spacecraft modelling (which is how I found it in the first place). Scroll down to the bottom of the page and you will find a batch of links to astronautical science sites. The NASA history office link is quite good. MARS.org "Lost Dreams" is also interesting, in fact all of them have some interest. Enjoy.

Robert Klaus
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Thank you
 
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