Author Topic: Thermal Protection Systems  (Read 47694 times)

Offline Jim

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Re: Thermal Protection Systems
« Reply #40 on: 05/24/2010 04:26 pm »
Jason, 

That doesn't negate the fact that if you put an insulator behind the metal, yes, it protects the structure behind the metal but it only makes it so the metal melts quicker.

Offline JasonAW3

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Re: Thermal Protection Systems
« Reply #41 on: 05/24/2010 04:50 pm »
Jason, 

That doesn't negate the fact that if you put an insulator behind the metal, yes, it protects the structure behind the metal but it only makes it so the metal melts quicker.

The insulator is for both the protection of the crew as well as acting as a porous material that the water can be sent through, removing the heat from both the insulator and acting to cool the heat shield via the steam disapation through the pinholes in the shield itself.
     The heated water, removing the heat from the insulation and the inner side of the heat shield would be released through the pinholes in the surface of the heat shield, creating a bow shock boundry layer of steam, in a fashion similar to the laminar airflow experimets from back in tyhe '70s and '80's.
     As this produces an OUTER insulated layer of steam, being vented from the radiation shielding layer between the inner and outer hulls, through the insulation layer between the craft and the metal TPS, thermal issues of metallic erosion are largely mitigated, although there may be some minor issues of high temperature steam erosion of the metallic TPS, including erosion around the pinholes and across the face of the TPS shield.
     While the water being vented into the bow shock will be many times hotter than standard water steam, it should be vastly cooler than the melting temperature of the high temperature alloys that would be used in this case.  If need be, a web of high temperature capillary tubing could be installed to allow heat transfer from the insulation layer to the water flowing in the web, and, again, out through the surface of the metallic TPS layer.
     As I seem to remember, this is a technique that has been tested in the past, as a method of heat disapation in high speed aerospace applications with similar thermal and pressure loads, albeit without the insulation layer.  What I am suggesting is a system that is mechanically, less complicated to mount to the surface of the craft, while affording the maximum potential of both safety and reusability.
     By using an active cooling system to disapate the heat from both infront and behind the metallic TPS layer, you reduce the damage to the TPS and provide an added layer of safety for the crew.

Jason
« Last Edit: 05/24/2010 09:07 pm by JasonAW3 »
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Offline JasonAW3

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Re: Thermal Protection Systems
« Reply #42 on: 05/26/2010 01:53 am »
Jason, 

That doesn't negate the fact that if you put an insulator behind the metal, yes, it protects the structure behind the metal but it only makes it so the metal melts quicker.

So cooling the insulation and inner surface of the metal TPS and venting the heat through the TPS via the steam generated in the insulation would STILL cause it to melt?  I would have thought that the steam blanket in front of the on coming air, in the bow wave as it were, would have acted as additional TPS insulation.   I guess that we wouldn't be able to vent enough heat from the insulation via the steam to compensate for the insulative properties of the semi-aerogel.  Is that what you're driving at?  The idea was to create a sort of "Water Fog" curtian in between the on coming air and the metal TPS sheild, in much the same way as a water fog curtain is used to protect firefighters in exceptionally hot blazes, or in a way similar to how a ballute could use the exhaust of the craft that it is around to act as both a slowing mechanism and as a way of creating a gap between the ballute and the oncoming air during reentry.
     A similar, fully active system has been used experimentally with metal TPS systems, I simply am trying to devise a simpler, semi-passive system to accomplish the same goal.

     Hmmmm....  Strange...  Alright, what about a spacer layer in between the TPS metal and the habitable section, using a sort of "wicking" system to allow water saturation in between the metal TPS and the outside skin.  As the "wicking" material goes above the boiling point of water, the steam starts being vented out of the pinholes in the outer surface of the metal TPS, assuming a waterproof insulating layer on the bottom of the habitable section and the spacer and "wicking" layer between the TPS shield and the insulation layer.

     Or perhaps simply get rid of the "wicking" layer completely and flood the space between the metal TPS layer and the insulation with water, (to be replenished as it is boiled off from the Radiation Shielding layer of the craft) again, venting through pinholes allover the metal TPS shield.  (Oh crud.  Jim, did you think that I was suggesting that the steam be vented from the EDGES of the TPS shield?  If so, that's where the confusion lies.  I meant to use a series of pinholes starting from the center of the metal TPS shield, spaced evenly along the entire surface of the TPS metal shield to vent the steam infront of the craft as it enters the atmosphere.  This way it would produce an even blanket of steam to both reduce the heat that the TPS is suffering as well as act to disapate the heat from the bow wave around the craft.
     Admittedly, such a system would create one heck of a contrail at high altitude, but it should still protect the craft quite readily.

Jason
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Offline mlorrey

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Re: Thermal Protection Systems
« Reply #43 on: 05/28/2010 09:10 am »
The first Chinese Shenzhou capsule used water saturated bamboo, which allowed for the water to create a boundary layer as it steamed out of the pores of the bamboo.

Why only the first one?

LOL I have no idea why, you should ask the Red Army next time you see them. I hear their transparency policies are unmatched outside of North Korea.

My opinion is that some political types thought that bamboo was too stereotypically chinese and made them look like primitives to the roundeyes in the west.
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Offline JasonAW3

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Re: Thermal Protection Systems
« Reply #44 on: 05/28/2010 01:44 pm »
The objective, I believe, was to come up with a reusable, relativly low cost, low maintenance, reusable, TPS system.
     A high temperature, metallic TPS, using steam venting through the blunt side of either a lifting body or a capsule, seems to be the best option, so long as it can be done so simply and relatively, cheap.
     Active cooling viadumping water between the inner shell and the TPS, and allowing it to boil off through pinholes in the face of the TPS looks like it may be the simplest, cheapest and most non-toxic option.
     The idea of decelerating a craft further than from basic ballistic deceleration, or using it to cool the leading edge of a hypersonic craft, frankly, hadn't occured to me.

     The main issue I have with either of these uses is that you would have a limited amount of coolant that is being rapidly boiled off, and might, if calculated correctly, last long enough to get through the hottest part of reentry from a Lunar or Mars return trajectory.

     Use of such a system for further deceleration, as a thrust system, would likely require more coolant than the craft could carry in its' voluume, although I could be wrong.  If the water was to super-heat, it could peoduce a significant thrust, but would then present issues of pressurization between the TPS and the inner hull, that could deform the inner hull, or even rupture into the main cabin itself, parbroiling the crew.
     Using it along the leading edge, wile requiring less water due to the smaller surface area being exposed to the high velocity and temperatures, would still require an excessive amount of coolant due to the longer duration of exposure.
     However; A stratigicly located set of LH2/LOX thrusters toward the center of the face of the capsule TPS, (offsetting it according to the angle of entry, making certian that it is directly in the center of the highest pressure and temperature zone during reentry) and along the centerline of a lifting body's TPS, (again, keeping the thrusters in the middle of the area of highest pressure and temperature) could act to further cool the TPS while adding a significant amount of deceleration during reentry.
     Leading edge cooling has its' own issues, but again, the use of small, relatively low powered LH2/LOX thrusters, strategically located just above the leading edge, and semi-conformally shaped,could, in theory, produce a sheath of gasses around the craft, both above and below the leading edge of the craft, with the majority of the sheath going over the top of the craft, adding to the lift.  Admittedly, this idea was cribbed from Supercavitation Torpedoes, (http://en.wikipedia.org/wiki/Supercavitation) but as this technique reduces the drag in water enough to allow rocket powered torpedoes to travel underwater at speeds in excess of 100 knots, (The fastest US subs can normally only do about 25 to 30 knots) I figure that a similar system should be able reduce drag, add a bit of lift, and cool the leading edges of a hypersonic aircraft.  I realize that hydrodynamics and aerodynamics are to seperate sciences, but as both are based in fluid dynamics, there may be enough similarity to be able to use this technique, or something similar to it.

Jason
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Offline Downix

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Re: Thermal Protection Systems
« Reply #45 on: 05/28/2010 01:49 pm »
At times, I'd thought of using a heat-transfer system, where, let's say that this is a powered landing craft using small jet engines to give some control for the final decent in the atmosphere.  The fuel for it, to save space, is frozen in a layer on the bottom-side of the craft.  The re-entry would melt this fuel, absorbing the energy through the state-change, making it useful for the final approach while also absorbing the heat energy away from the TPS.

Just random thoughts this morning.
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Offline A_M_Swallow

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Re: Thermal Protection Systems
« Reply #46 on: 05/28/2010 05:24 pm »
     Leading edge cooling has its' own issues, but again, the use of small, relatively low powered LH2/LOX thrusters, strategically located just above the leading edge, and semi-conformally shaped,could, in theory, produce a sheath of gasses around the craft, both above and below the leading edge of the craft, with the majority of the sheath going over the top of the craft, adding to the lift.  Admittedly, this idea was cribbed from Supercavitation Torpedoes, (http://en.wikipedia.org/wiki/Supercavitation) but as this technique reduces the drag in water enough to allow rocket powered torpedoes to travel underwater at speeds in excess of 100 knots, (The fastest US subs can normally only do about 25 to 30 knots) I figure that a similar system should be able reduce drag, add a bit of lift, and cool the leading edges of a hypersonic aircraft.  I realize that hydrodynamics and aerodynamics are to seperate sciences, but as both are based in fluid dynamics, there may be enough similarity to be able to use this technique, or something similar to it.

Jason

This is a re-entry system.  Do we want to minimise drag or maximise drag to increase the braking effect?

Offline JasonAW3

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Re: Thermal Protection Systems
« Reply #47 on: 05/29/2010 08:55 am »
The first Chinese Shenzhou capsule used water saturated bamboo, which allowed for the water to create a boundary layer as it steamed out of the pores of the bamboo.

Why only the first one?

LOL I have no idea why, you should ask the Red Army next time you see them. I hear their transparency policies are unmatched outside of North Korea.

My opinion is that some political types thought that bamboo was too stereotypically chinese and made them look like primitives to the roundeyes in the west.

Hmmm....

    Cheap, disposable, made from naturally grown and redily available materials, lightweight, uses water as a cooling system, can add layers as needed for higher velocity reentry?
     Gee, I wish NASA thought so primatively!  Sounds to me like they used an economical, readily availabe natural resource in a VERY clever way!  I say; Unless there is some issue where the really NEED to use another TPS material, the Chinese SHOULD continue to use water soaked bamboo as a TPS material!   Maybe, for disposable capsules, we should consider growing a grove of bamboo outside of the VAB, set up a "Basket Weavers" facility near by, (yes, I know that they wouldn't actually be weaving baskets, probably be more like rendering it down to fiber and applying it like layers of fiberglass to the hull as TPS material) and apply it on site.  To be honest, I look at it as a form of the KISS principle.  Keep It Simple Stupid!  We should applaud the Chinese for their solution.

     Only issue I can see here would be for long term flights where Ice crystals in the bamboo could degrade the overall structure, or the water could sublimate through outgassing. If so, a simple Mylar outer wrap of the TPS, or heck, maybe duct tape, could help resolve that issue.
     And yes, I AM serious about the Duct Tape.  If we can slap a decal onto the side of a space craft, have it last for months on orbit, and even survive reentry, why couldn't duct tape?
     Heck, if need be a reformulated version using the same materials as those self same decals, with a fiberglass backing, could be used.

Jason
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Offline Jim

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Re: Thermal Protection Systems
« Reply #48 on: 05/29/2010 02:10 pm »

    Cheap, disposable, made from naturally grown and redily available materials, lightweight, uses water as a cooling system, can add layers as needed for higher velocity reentry?
     Gee, I wish NASA thought so primatively!  Sounds to me like they used an economical, readily availabe natural resource in a VERY clever way!  I say; Unless there is some issue where the really NEED to use another TPS material, the Chinese SHOULD continue to use water soaked bamboo as a TPS material!   Maybe, for disposable capsules, we should consider growing a grove of bamboo outside of the VAB, set up a "Basket Weavers" facility near by, (yes, I know that they wouldn't actually be weaving baskets, probably be more like rendering it down to fiber and applying it like layers of fiberglass to the hull as TPS material) and apply it on site.  To be honest, I look at it as a form of the KISS principle.  Keep It Simple Stupid!  We should applaud the Chinese for their solution.

It isn't a new idea.  The Russians used wood on their early warheads.    The issue is voids and discontinuities in the wood and fibers, which makes it not reliable for manned use.

Offline JasonAW3

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Re: Thermal Protection Systems
« Reply #49 on: 05/29/2010 07:51 pm »

    Cheap, disposable, made from naturally grown and redily available materials, lightweight, uses water as a cooling system, can add layers as needed for higher velocity reentry?
     Gee, I wish NASA thought so primatively!  Sounds to me like they used an economical, readily availabe natural resource in a VERY clever way!  I say; Unless there is some issue where the really NEED to use another TPS material, the Chinese SHOULD continue to use water soaked bamboo as a TPS material!   Maybe, for disposable capsules, we should consider growing a grove of bamboo outside of the VAB, set up a "Basket Weavers" facility near by, (yes, I know that they wouldn't actually be weaving baskets, probably be more like rendering it down to fiber and applying it like layers of fiberglass to the hull as TPS material) and apply it on site.  To be honest, I look at it as a form of the KISS principle.  Keep It Simple Stupid!  We should applaud the Chinese for their solution.

It isn't a new idea.  The Russians used wood on their early warheads.    The issue is voids and discontinuities in the wood and fibers, which makes it not reliable for manned use.

I kind of figured that voids could be an issue.  I thought I meantioned reducing the bamboo to fiber and applying it kind of like layers of fiberglass, but I think I might of missed putting that down.  If so, I'm sorry about that.  Reducing it to fiber should avoid the voids, so to speak.

Jason
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Offline RanulfC

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Re: Thermal Protection Systems
« Reply #50 on: 06/10/2010 07:10 pm »
Bamboo fibers, (by the way) can also replace carbon fibers in many applications for composites.

Randy
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Offline JasonAW3

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Re: Thermal Protection Systems
« Reply #51 on: 06/10/2010 10:24 pm »
Bamboo fibers, (by the way) can also replace carbon fibers in many applications for composites.

Randy

Hmmmm...

     I did not know that.  How's the durability, weight and stress levels compare to carbon fiber?

Jason
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Offline cheesybagel

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Re: Thermal Protection Systems
« Reply #52 on: 06/16/2010 10:50 pm »
The solution to TPS? Why, base first reentry of course.

If do a rocket powered landing you can use the engine exhaust plume to help punch your way through the atmosphere. Plus, the rocket engine was already designed to handle high temperatures using ablatives, film cooling, transpiration cooling, or whatever.

It's a bit of a waste not to use all that reentry heat for something.

Offline Robotbeat

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Re: Thermal Protection Systems
« Reply #53 on: 06/16/2010 10:52 pm »
The solution to TPS? Why, base first reentry of course.

If do a rocket powered landing you can use the engine exhaust plume to help punch your way through the atmosphere. Plus, the rocket engine was already designed to handle high temperatures using ablatives, film cooling, transpiration cooling, or whatever.

It's a bit of a waste not to use all that reentry heat for something.

Without the first-stage engines running propellant through them, they are not cooled.
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Offline RanulfC

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Re: Thermal Protection Systems
« Reply #54 on: 06/18/2010 01:43 pm »
Bamboo fibers, (by the way) can also replace carbon fibers in many applications for composites.

Randy

Hmmmm...

     I did not know that.  How's the durability, weight and stress levels compare to carbon fiber?
Comparable in many cases and as I understand it not many people knew much about the idea until about 5 years ago when there was an major shortage of carbon fibers due to high demand. It seems that some manufacturers had replaced carbon-fibers with bamboo but where still selling the product as having CFs in them. I found out about it because a local bike frame builder stated directly though he'd read the studies and reports on replacing CF with bamboo his company would continue to depend only on CFs as that was what they felt was the better option.

A couple of google searchers later I found out that in order to NOT get sued into oblivion those companies that had been using bamboo instead of CFs had to both sponser a new series of studies and inform all the customers who had been sold non-CF equipment of that fact and offer free replacement. For the most part, while people were frakked about paying higher prices and not getting actual CFs once the companies payed back the 'over-charges' the majority went ahead and kept the bamboo based equipment as they felt there was no major difference between the two EXCEPT for price.

Several of the companies now market bamboo in composites instead of CFs.

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline JasonAW3

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Re: Thermal Protection Systems
« Reply #55 on: 06/18/2010 10:43 pm »
Bamboo fibers, (by the way) can also replace carbon fibers in many applications for composites.

Randy

Hmmmm...

     I did not know that.  How's the durability, weight and stress levels compare to carbon fiber?
Comparable in many cases and as I understand it not many people knew much about the idea until about 5 years ago when there was an major shortage of carbon fibers due to high demand. It seems that some manufacturers had replaced carbon-fibers with bamboo but where still selling the product as having CFs in them. I found out about it because a local bike frame builder stated directly though he'd read the studies and reports on replacing CF with bamboo his company would continue to depend only on CFs as that was what they felt was the better option.

A couple of google searchers later I found out that in order to NOT get sued into oblivion those companies that had been using bamboo instead of CFs had to both sponser a new series of studies and inform all the customers who had been sold non-CF equipment of that fact and offer free replacement. For the most part, while people were frakked about paying higher prices and not getting actual CFs once the companies payed back the 'over-charges' the majority went ahead and kept the bamboo based equipment as they felt there was no major difference between the two EXCEPT for price.

Several of the companies now market bamboo in composites instead of CFs.

Randy

One has to wonder if anyone has considered building pressure vessels out of bamboo composites.   Not really certainwhat temperature extremes that such composites could handle, but that would be an interesting research project.

Jason
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Offline mmeijeri

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Re: Thermal Protection Systems
« Reply #56 on: 10/23/2010 01:46 pm »
Some interesting TPS-related concepts I came across on NTRS:

INTEGRATED THERMAL PROTECTION SYSTEMS AND HEAT RESISTANT STRUCTURES
INTEGRATED THERMAL PROTECTION SYSTEMS AND HEAT RESISTANT STRUCTURES
A report and a set of slides about three ceramic-based heat shields for capsules: one fully reusable ceramic shield for LEO return, a hybrid using a similar shield with a reduced ablator on top and a ceramic shield combined with a deployable ceramic decelerator.

New Approach for Thermal Protection System of a Probe During Entry
Uses an ablative shield combined with heat pipes and a radiator on the afterbody as well as phase change materials.

Heat Sponge: A Concept for Mass-Efficient Heat Storage
A new concept for phase change materials that uses liquid-gas transitions instead of solid-liquid for much better mass efficiency.
« Last Edit: 10/23/2010 05:40 pm by mmeijeri »
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Offline mmeijeri

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Offline A_M_Swallow

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Re: Thermal Protection Systems
« Reply #58 on: 10/23/2010 05:21 pm »
A game changing technology in this area is a reusable Thermal Protection System that allows manned spacecraft to return to LEO from escape velocity.  A return to LEO spacecraft that does not need gigantic amounts of fuel can be much bigger than a return to Earth's surface capsule.

Offline corrodedNut

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Re: Thermal Protection Systems
« Reply #59 on: 10/23/2010 05:52 pm »
Some interesting TPS-related concepts I came across on NTRS:

Yes, very interesting. You want to know the "deployable decelerator" reminds me of?

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