Elon Musk: "It's game over for all the other heavy lift rockets"

Quaoar · 2020-03-24 18:38:03

SpaceNut wrote:

Direct bond means that it will transfer to the shell but with layers of adhesive and blanket you isolate and slow that process of thermal conduction through them...

Tiles are glued to blankets which are glued to the steel shell with a UHT silicon adhesive. It seems to me a good solution.

kbd512 · 2020-03-24 21:12:18

Quaoar,

I would think nuts and bolts or studs would be used. It'll most likely be some kind of torque-to-yield design. So long as the loads applied don't exceed the clamping force, that should prevent fatigue failures. Achieving the correct preload when torquing the bolts is critical, though, which means training people to use a torque wrench. Millions of mechanics have figured this out, but once mechanics with PhD's are thrown into the mix all bets are off. The upside is that the mass associated with the fastening hardware should be minimized. The downside is that you have to throw that fastening hardware away whenever you need to replace a tile.

Edit:
Here's a good paper on why the Space Shuttle engineers selected the various materials that they used and some of the testing methods used to retire risk associated with the fatigue life of the orbiter's airframe:

Orbiter Structural Design

The structural engineers who designed the orbiter's airframe had direct access to the designers of the Concorde and SR-71, so they took the design elements from those two high speed aircraft that would work for the Space Shuttle program and blended them with various other techniques required to address the unique challenges of the extreme thermal flux produced during reentry. I had books on this stuff as a kid.

Last edited by kbd512 (2020-03-25 01:06:48)

Quaoar · 2020-03-25 03:30:09

kbd512 wrote:

Quaoar,
I would think nuts and bolts or studs would be used. It'll most likely be some kind of torque-to-yield design. So long as the loads applied don't exceed the clamping force, that should prevent fatigue failures. Achieving the correct preload when torquing the bolts is critical, though, which means training people to use a torque wrench. Millions of mechanics have figured this out, but once mechanics with PhD's are thrown into the mix all bets are off. The upside is that the mass associated with the fastening hardware should be minimized. The downside is that you have to throw that fastening hardware away whenever you need to replace a tile.
Edit:
Here's a good paper on why the Space Shuttle engineers selected the various materials that they used and some of the testing methods used to retire risk associated with the fatigue life of the orbiter's airframe:
Orbiter Structural Design
The structural engineers who designed the orbiter's airframe had direct access to the designers of the Concorde and SR-71, so they took the design elements from those two high speed aircraft that would work for the Space Shuttle program and blended them with various other techniques required to address the unique challenges of the extreme thermal flux produced during reentry. I had books on this stuff as a kid.

How to deal with the holes for the nuts in the tiles? By gluing over some kind of PICA-X corks?

Just another thing, please, the steel skin is a bulk plate or a honeycomb?
Another possibility is the steel foam sandwich: what do you think about it?

Last edited by Quaoar (2020-03-25 03:38:31)

SpaceNut · 2020-03-25 10:12:44

Well it was Nasa that did not like the Red Dragon legs poking through the Pica shield when landing as its going to create voids as it wears around the plug faster than if there is none. The best way would be to hide the fastener on the back side of each tile of pica but how to make then hold better than and adhesive means making the fastner with a fender like washer built into that hardware to cause the holding force to be around that surface and not just on the fastner.

GW Johnson · 2020-03-25 16:45:46

Kbd512 knows more about the newer materials than I do. I've been out of it for a long time now. What I know is the older stuff, up to shuttle's low-density tiles and carbon-carbon leading edges and nosetip. That would be the old reinforced phenolics, Avcoat as flown on Apollo, and what I have learned since about PICA and PICA-X.

For adhesive work, there are no epoxies with adhesion capability past 290 F, and there are no silicones not charred loose at 600 F. There are ceramic adhesives that go hotter, but they are for metal-ceramic bonds.

NASA has a real "not-invented-here" problem with holes in heat shields. They gave a used flight test Gemini to USAF for USAF's MOL program. USAF sawed a circular hatch hole in that used heat shield to test for its Gemini-B design, and then flew it (unmanned) for the one-and-only flight test that MOL got done before cancellation in 1969. It worked fine coming back from orbit. As a reflown, used heat shield, with a big hatch cut in it. The damned thing is still on public display today.

GW

Quaoar · 2020-03-26 04:44:20

GW Johnson wrote:

Kbd512 knows more about the newer materials than I do. I've been out of it for a long time now. What I know is the older stuff, up to shuttle's low-density tiles and carbon-carbon leading edges and nosetip. That would be the old reinforced phenolics, Avcoat as flown on Apollo, and what I have learned since about PICA and PICA-X.
For adhesive work, there are no epoxies with adhesion capability past 290 F, and there are no silicones not charred loose at 600 F. There are ceramic adhesives that go hotter, but they are for metal-ceramic bonds.
NASA has a real "not-invented-here" problem with holes in heat shields. They gave a used flight test Gemini to USAF for USAF's MOL program. USAF sawed a circular hatch hole in that used heat shield to test for its Gemini-B design, and then flew it (unmanned) for the one-and-only flight test that MOL got done before cancellation in 1969. It worked fine coming back from orbit. As a reflown, used heat shield, with a big hatch cut in it. The damned thing is still on public display today.
GW

Hi, GW

I have found this new 3M 1137 sealant: they claim it works up to 2000 F

https://www.3m.com/3M/en_US/company-us/ … 008&rt=rud

For the steel outer skin of my waverider: should it be a bulk plate or can it be a honeycomb or a steel foam sandwich?

kbd512 · 2020-03-26 09:45:38

Quaoar,

There are numerous methods for attachment of tiles or skin panels using overlaps or blind fasteners or even clamps that would work for this application. These methods are already in use for aircraft skin fabrication. Blind fasteners are commonly used for attachment of skins or composite parts on wings and control surfaces, even on home built aircraft. This covers everything from rivets to bolts to clamps / clips that use a cam action and steel spring tension to affix the part or skin panel to the airframe.

The "steel skin / airframe" is more like "steel propellant tank structure with external attachment points" than a separate outer layer of material to affix the heat shield to. I would weld rows of external brackets to the tanks / airframe to serve as attachment points for bolts or clamps to affix the tiles so the propellant tanks and tiles can expand and contract during thermal cycling to provide strain relief for the tiles, preventing the severe thermal loads from cracking the tiles due to the differences in coefficients of thermal expansion between steel and high temperature ceramics.

The arrangement for the control surfaces could consist of UHTC sharp leading edges bolted to stainless steel ribs or tubing with TUFROC tiles affixed to the faces of the control surfaces. That's very conventional stuff for aircraft wing and empennage structures. On second thought, perhaps angle iron ribs and brackets welded to a piece of steel honeycomb sandwich panel could create a stiffer structure for less mass.

Instead of trying to absolutely minimize the service temperature with thicker TPS and insulation to avoid melting light alloys or composites, we're using steel's higher strength at elevated temperatures to arrive at a structure that's still comparable in weight and doesn't run into so many maximum permissible operating temperature and service life limitations.

GW Johnson · 2020-03-30 12:02:25

Some of these things are amenable to attachment with fasteners, others are not, most notably the ceramics.

There does need to be an impermeable layer in the substrate to stop inflow of entry plasma. Fasteners through the substrate open up a plethora of possible failure modes, since there seems to be thousands of individual tiles. The gaps between tiles are not much of a threat, but any fastener holes through the shell beneath are a threat.

There is something else to worry about: the mismatch of deflections between the tiles and the substrate. These deflections are due to both thermal expansion and structural strains. Most of the ablatives, and certainly the ceramics, are brittle materials. They have very little elongation to failure. The opposite is true of stainless substructure.

If the tiles are to be bonded, the adhesive needs a huge elongation capability, as well as high temperature tolerance. The only material I know that fills that bill are the two-part silicone adhesives. They are good to about 600 F, and long-gone at 700 F, and they are very notch-sensitive. You would do well to use at least 3 blobs of adhesive holding each tile, to achieve redundancy, in case one or more decides to split.

I know of nothing that would go hotter and still have large elongation. So it will be the adhesive that sets max backside temperature, not the steel substrate. That's cold enough to use titanium, but titanium has no ductility and cannot be formed into sheet, much less rolled and welded. That's alpha-phase 6-4. There are a couple of ductile beta-phase alloys, but they age at room temperature into junk within 6 months.

600 F is way too hot for aluminum. So now you know why they selected steel, in particular stainless, so it won't scale, and it won't corrode if not painted. But it has a lousy emissivity for radiation cooling.

GW

kbd512 · 2020-03-31 01:29:18

GW,

I see you touched on why I suggested clamping to provide strain relief to the tiles. If anyone else is unfamiliar with what I'm talking about, it's the ability of the propellant tank to flex during the various heating and cooling cycles associated with ascent and on-orbit operations and reentry without cracking any of the tiles surrounding the tank. Stainless will flex quite a bit in comparison to the heat shield tiles. Also, the fiber-reinforced ceramics are not as brittle as the traditional tiles. Since those are attached to X-37 using bolts, I presume they can be attached to Starship using bolts. TUFROC is not a homogenous material / structure in actual implementations. It's a sandwich of different materials with different properties. The cap is a type of glass to prevent oxidation during reentry, followed by a toughened ceramic that absorbs and re-radiates the high thermal load, followed by a much tougher substrate that's used as the attachment point for the heat protected structure.

For those who are having a tough time visualizing how this would work, picture the large blunt foam tipped paint brushes with wooden handles sold at the hobby stores. Imagine that the foam is actually the high temperature fiber toughened ceramic tile. Imagine that the wooden handle serves as a stubby attachment point. The handle is just one of the non-homogenous portions of TUFROC (the other being the glass cap over the ceramic tile for oxidation protection) and is much tougher (greater tensile strength than the ceramic tile and greater ability to deal with shear loadings) attachment point / insulation that inhibits heat transfer between the hot ceramic tile and the protected structure (the propellant tanks of Starship, in this case). Now instead of a bolt drilled into the stubby "handle" of the tile / paint brush to attach it to the propellant tank, we develop a properly tensioned stainless steel ring that clamps around the entire circumference of the "handle" to permit the propellant tank it's attached to to expand / contract without fracturing the ceramic portion of the tile assembly. Bear in mind that we're talking about fractions of an inch, for any given tile, when we're talking about the tanks flexing under thermal load. In the NASA tech briefs, this is known as the "pylon" attachment system. We could have a single pylon per tile or a number of pylons, perhaps three of them, and much larger tiles.

I can even imagine a BNNT cable-pull system that locks / unlocks individual tiles so that you can stand under the tail of Starship and unlock tiles all the way at the top of the vehicle with the help of another crew member who will catch and remove the tile that requires replacement. The cable would be attached to a tensioning ring and threaded through pulleys that provide leverage. The edges of the tiles could be supported by additional steel springs that prevent the edges of the tiles from deflecting too much under thermal and mechanical loads.

GW Johnson · 2020-04-01 23:10:17

Kbd512:

That "pylon" attachment scheme is intriguing. I gotta think about that.

You know more about the newer materials than I do. I'm pretty good with the reinforced phenolics, and with low-density ceramics. I know a little about Avcoat, but not as much as the others. I also understand carbon-carbon.

I know a little about PICA/PICA-X, because I researched and read about them. Think "phenolic impregnated carbon ablator". It's actually similar to the reinforced phenolics, of which silica phenolic is probably the best. PICA/PICA-X is just lighter and even more capable.

I know quite a bit about DC-93-104, having used a lot of it in ramjet combustors. I know enough to know it is not a good candidate for an entry heat shield. It's a silicone polymer loaded with carbon fibers, silica particles, and some silicon carbide particles for reinforcement.

The carbon fibers help hold the char layer to the pyrolysis layer just below, but cannot take entry fluid shear forces. The silicon carbide is a reinforcing aggregate similar to the gravel in concrete. The silica melts and sort of glues the aggregate-bearing carbon char layer together, so it does not crumble so easily.

If you can mechanically retain the char layer to the engine case (and I know how to do that), you can use it as an insulator even after it has charred completely through and lost its adhesive bond to the case.

The virgin material is quite strong, and will support casting rocket propellant grains capable of "mil std" shake, rattle, and roll. Hot/cold, etc. That's a big part of how you put an "integral booster" inside a ramjet engine. But, you have to chemically isolate the propellant from the silicone ablator. I know how to do that, too.

GW

Quaoar · 2020-04-02 03:43:02

kbd512 wrote:

GW,
I see you touched on why I suggested clamping to provide strain relief to the tiles. If anyone else is unfamiliar with what I'm talking about, it's the ability of the propellant tank to flex during the various heating and cooling cycles associated with ascent and on-orbit operations and reentry without cracking any of the tiles surrounding the tank. Stainless will flex quite a bit in comparison to the heat shield tiles. Also, the fiber-reinforced ceramics are not as brittle as the traditional tiles. Since those are attached to X-37 using bolts, I presume they can be attached to Starship using bolts. TUFROC is not a homogenous material / structure in actual implementations. It's a sandwich of different materials with different properties. The cap is a type of glass to prevent oxidation during reentry, followed by a toughened ceramic that absorbs and re-radiates the high thermal load, followed by a much tougher substrate that's used as the attachment point for the heat protected structure.
For those who are having a tough time visualizing how this would work, picture the large blunt foam tipped paint brushes with wooden handles sold at the hobby stores. Imagine that the foam is actually the high temperature fiber toughened ceramic tile. Imagine that the wooden handle serves as a stubby attachment point. The handle is just one of the non-homogenous portions of TUFROC (the other being the glass cap over the ceramic tile for oxidation protection) and is much tougher (greater tensile strength than the ceramic tile and greater ability to deal with shear loadings) attachment point / insulation that inhibits heat transfer between the hot ceramic tile and the protected structure (the propellant tanks of Starship, in this case). Now instead of a bolt drilled into the stubby "handle" of the tile / paint brush to attach it to the propellant tank, we develop a properly tensioned stainless steel ring that clamps around the entire circumference of the "handle" to permit the propellant tank it's attached to to expand / contract without fracturing the ceramic portion of the tile assembly. Bear in mind that we're talking about fractions of an inch, for any given tile, when we're talking about the tanks flexing under thermal load. In the NASA tech briefs, this is known as the "pylon" attachment system. We could have a single pylon per tile or a number of pylons, perhaps three of them, and much larger tiles.
I can even imagine a BNNT cable-pull system that locks / unlocks individual tiles so that you can stand under the tail of Starship and unlock tiles all the way at the top of the vehicle with the help of another crew member who will catch and remove the tile that requires replacement. The cable would be attached to a tensioning ring and threaded through pulleys that provide leverage. The edges of the tiles could be supported by additional steel springs that prevent the edges of the tiles from deflecting too much under thermal and mechanical loads.

Please, let me know if I correctly visualized the pylon concept: every tile has one or more pylons with a groove on the base which is forced into a steel ring welded on the steel shell almost like a snap fastener. Does it work this way?

Can TUFROC tiles or leading edges withstand a 19 km/s atmospheric entry?

Last edited by Quaoar (2020-04-02 07:52:31)

GW Johnson · 2020-04-02 08:35:57

Quaoar:

I put some entry heat protection estimating techniques up on "exrocketman".

GW

Quaoar · 2020-04-02 12:00:17

GW Johnson wrote:

Quaoar:
I put some entry heat protection estimating techniques up on "exrocketman".
GW

Thanks GW

I'm one of your followers

kbd512 · 2020-04-02 13:01:05

Quaoar,

That's the idea, more or less. I was actually thinking of a sort of clamp that has just enough "spring" to it to enable thermal expansion and contraction. In other words, the clamp allows the pylon (that the rest of the tile is attached to) to move up and down as the tank expands and contracts. It's like the expansion joints on stainless steel exhaust headers, but swaged onto the tile's pylon and tempered to provide the correct amount of "spring" after it's affixed to the pylon. The pylon itself will have a "lip" on the end to keep the expansion joint from sliding off of it. The expansion joint is then rotated to clamp or un-clamp it to the tank, a bit like the blunt "threads" on a lightbulb, but also including a detent to lock it into place. This can all be done with a short section of tubular sheet steel.

It's way simpler in practice than it is to explain what it's doing. Once you see one of these devices, which have been in use in aviation for many decades, you'll laugh at how simple it is. It does require forming dies to progressively swage the steel tube over the pylon lip, but that's the extent of the special tooling required. Like I said, it's been in use for decades and it's a commercial product that's pretty cheap. I think they cost a dollar or so and we might need several thousand of them per Starship.

Alternatively, there are step-less screw clamps or hose clamps or collared slotted spring-loaded studs (used for fastening engine cowlings) that could serve the same purpose. In fact there are at least a half dozen different kinds of fasteners that would do what I had in mind. Those are more expensive, but you could just walk into the hardware store with your credit card and walk away with high quality stainless steel tensioning fasteners that does what we need it to do.

Quaoar · 2020-04-02 15:49:38

kbd512 wrote:

Quaoar,
That's the idea, more or less. I was actually thinking of a sort of clamp that has just enough "spring" to it to enable thermal expansion and contraction. In other words, the clamp allows the pylon (that the rest of the tile is attached to) to move up and down as the tank expands and contracts. It's like the expansion joints on stainless steel exhaust headers, but swaged onto the tile's pylon and tempered to provide the correct amount of "spring" after it's affixed to the pylon. The pylon itself will have a "lip" on the end to keep the expansion joint from sliding off of it. The expansion joint is then rotated to clamp or un-clamp it to the tank, a bit like the blunt "threads" on a lightbulb, but also including a detent to lock it into place. This can all be done with a short section of tubular sheet steel.
It's way simpler in practice than it is to explain what it's doing. Once you see one of these devices, which have been in use in aviation for many decades, you'll laugh at how simple it is. It does require forming dies to progressively swage the steel tube over the pylon lip, but that's the extent of the special tooling required. Like I said, it's been in use for decades and it's a commercial product that's pretty cheap. I think they cost a dollar or so and we might need several thousand of them per Starship.
Alternatively, there are step-less screw clamps or hose clamps or collared slotted spring-loaded studs (used for fastening engine cowlings) that could serve the same purpose. In fact there are at least a half dozen different kinds of fasteners that would do what I had in mind. Those are more expensive, but you could just walk into the hardware store with your credit card and walk away with high quality stainless steel tensioning fasteners that does what we need it to do.

The problem is that you don't have access to the space between the shell and inner face of the tiles, because the tiles and the shell cannot be pierced. So you need some sort of snap fastener which doesn't need to be screwed, bolted, riveted or rotated but only locked by pressing the tile over it, as when you glue the tiles of a parquet.

Last edited by Quaoar (2020-04-02 15:52:14)

SpaceNut · 2020-04-02 17:05:39

Think of how the auto industry uses a fender clip for attaching the trim molding to the vehicle only not of soft plastic but with some other barbed retaining system, just made from metals.

77e0fe9b-7dc0-4f68-a678-d7b1ae71a605_1.5da9e2511b57aeec62715a8f72233f7a.jpeg

make the head of the screw large to slide under a slot in the back of the tile and push the capture part into a hole followed by seating the tile to the shell.

Oh and I am glad you are doing ok....

kbd512 · 2020-04-02 18:33:26

Quaoar,

I think there's a fundamental misunderstanding of how this works. You're clamping the pylon to a welded attachment point on the exterior of the propellant tank. You don't need to penetrate the exterior heat shield to do that. There's going to be a small air gap between the back of the tile that the pylon is connected to and the exterior of the propellant tank- if nothing else, so that the tank and tiles can expand and contract. The entire back face of the tile isn't jammed up against the propellant tank and held in place with some comparatively weak adhesive. Instead, we're using a short little standoff in the form of the pylon and locking clamp. That's the space you have to work with. You can use tools to rotate the locking collar into place or tension the clamp, whichever system you choose to use.

kbd512 · 2020-04-02 18:56:15

SpaceNut,

The clamp is more like this:

Galvanized Steel Clamp, 12" Duct Fitting Diameter, 21" Duct Fitting Length

or that:

Oetiker Stepless Screw Clamps

or the other:

TE Connectivity P-Clamp

or yet another:

Quick Release V-Clamp

But let's read about how these types of clamping devices are used in hot turbocharged aircraft engine exhaust systems:

FAA: Best Practices Guide for Maintaining Exhaust System Turbocharger to Tailpipe V-band Couplings / Clamps

Edit:
Look at pages 15 and 16 of the guide to see how these clamps would be clamped over a heat shield tile pylon with a flange.

Last edited by kbd512 (2020-04-02 19:17:35)

Quaoar · 2020-04-03 14:36:56

kbd512 wrote:

Quaoar,
I think there's a fundamental misunderstanding of how this works. You're clamping the pylon to a welded attachment point on the exterior of the propellant tank. You don't need to penetrate the exterior heat shield to do that. There's going to be a small air gap between the back of the tile that the pylon is connected to and the exterior of the propellant tank- if nothing else, so that the tank and tiles can expand and contract. The entire back face of the tile isn't jammed up against the propellant tank and held in place with some comparatively weak adhesive. Instead, we're using a short little standoff in the form of the pylon and locking clamp. That's the space you have to work with. You can use tools to rotate the locking collar into place or tension the clamp, whichever system you choose to use.

But even if there is a small air gap between the tiles and the steel skin - which is very useful and can also act as a Whipple shield against meteoroids - the tiles form a continuous surface over the shell. So when you insert the last tile of the mosaic, you have no more gaps to insert a tool and lock the last clamp. That's why I thought to some sort of snap fastener.

Last edited by Quaoar (2020-04-03 14:56:53)

kbd512 · 2020-04-03 15:16:15

Quaoar,

Ever seen a bung wrench or speed wrench or used dog leg socket wrench extensions before?

Imagine you have a stack of drums on a pallet, stacked two pallets high. The teeth in the almost half-circle bung wrench grab the indentations on the cap of the drum. Even though you only have a small space to work with, you can come in from the side and open the drums, so long as you have just enough room to lift the cap off the drum. I know this works because I've done it. Heck, I've done stuff like this on plumbing pipes in tight spaces.

So, at least one of those fasteners I linked to in Post #93, you could come in from the side (the air gap between the propellant tank and the tiles), and fasten or loosen the clamp with a speed wrench or simply a long shaft dog leg socket wrench extension attached to an air wrench. Again, I know this works because I've extracted bolts from engines in places I couldn't get my hands or a traditional wrenches without further disassembly of the engine by using this method instead.

Maybe my explanations aren't very good, but it doesn't change the fact that it works. I think watching a YouTube video of someone using a dog leg socket wrench extension would explain everything. In the end, you're just using a long shaft tool to come in through a very small air gap to tighten or loosen a fastener.

Yes, one other potential solution is to use a final tile or cap strip that's fastened to another location on the vehicle not subjected to the oncoming flow of super heated plasma. However, if the gap is big enough to torque one clamped tile into place, it's big enough to torque the last one as well. And yes, we'd probably end up using cap tiles at the rear end of the rocket to present a single seamless heat shield surface. You'd start at the top or tip of the rocket and work your way back to the tail of the rocket. You'd either use some type of refractory metal or some kind of pad to serve as the bearing surface between Starship and its booster.

In any event, this type of attachment system can be made to work without any penetrations of the heat shield and, at least in my mind, it's not terribly complicated, being nothing more sophisticated than an application of existing technologies. Explaining it in internet posts is more complicated than actually doing the work.

Quaoar · 2020-04-03 15:49:15

GW Johnson wrote:

Quaoar:
I put some entry heat protection estimating techniques up on "exrocketman".
GW

Thanks GW,

After reading you lesson, I was able to calculate the heating rate of the leading edges of my waverider: R = 12.5 cm, v = 18.9 km/s, air density at 90 km = 0.000019 kg/m3 (It's an extra-solar super-earth).

It results 1456.6 W/cm2 of convective heating and 9834 W/cm2 of radiative heating, with a total heat rate of 11290.6 W/cm2, too much for PICA-X, for which I found an upper limit of 1000 W/cm.

So I made some research and discovered Surface Protected Ablators (SPA): an ablative material like phenolic carbon wrapped inside a hot hard material like C/SiC with ventilation holes. The C/SiC conserves its profile, withstands the air load and is cooled by the ablator. It was used on German capsule MIRKA and it can withstand up to 13000 W/cm2.

http://isa-space.eu/5th%20TPS-WS%20-%20 … 0final.pdf

Other promising materials are:

1) low density porous ceramics (foamed zirconia has the best performances) impregnated with ablative resins*, which conserve theirs profile while the resins evaporate cooling the ceramics.

https://books.google.it/books?id=xekfi1 … s+ceramic+

https://patentimages.storage.googleapis … 395035.pdf

2) The Sepcore concept: a sandwich with an ablative outer layer, a hot C/SiC core and an inner layer of insulating low density material.

http://www.esa.int/esapub/bulletin/bullet94/ROUM.pdf

*Porous ceramic coolers are very ancient devices, probably invented by the Egyptian to drink fresh beer in 3000 B.C.. They mixed clay whit salt and made jars. When they put water inside the jars, the salt dissolved in the water leaving a porous ceramic. They put beer in sealed amphorae, put amphorae inside porous jars and filled the jars with water. The water exuded over the outer surface and evaporated cooling the water inside and the beer.
Porous ceramic jars were still used in Italy in the sixties, when many country villages were not yet electrified. I remember my maternal grandpa used one of them in his vacation house in the mountains of Sila, to keep fresh his white wine.
It might be interesting to note how old ideas are recycled for new hi-techs

Last edited by Quaoar (2020-04-04 04:20:56)

GW Johnson · 2020-04-05 11:32:27

Quaoar:

Watch out using zirconia. It tends to crumble within a few reuses, especially if you take it up as hot as it can go, which is considerable. I got that warning from a zirconia maker.

The fancy modern materials Kbd512 may know more about. I'm too old and obsolete for that. But fiber-reinforced ablatives is a good way to go. carbon and silicon carbide fiber look promising to me, if the right matrix can be identified. Looks to me like there might be a large number of promising candidates these days.

GW

Quaoar · 2020-04-05 14:53:15

GW Johnson wrote:

Quaoar:
Watch out using zirconia. It tends to crumble within a few reuses, especially if you take it up as hot as it can go, which is considerable. I got that warning from a zirconia maker.
The fancy modern materials Kbd512 may know more about. I'm too old and obsolete for that. But fiber-reinforced ablatives is a good way to go. carbon and silicon carbide fiber look promising to me, if the right matrix can be identified. Looks to me like there might be a large number of promising candidates these days.
GW

Thanks, GW.
Following your advice, I'll use surface protected ablator (SPA) a carbophenolic ablator wrapped inside a C/SiC leading edge with ventilation holes. I have found it can withstand a heat flux up to 3.8 MW/m2 so it looks to be OK for the leading edges of my waverider, according to your formulas.
I also would like to use SPA for the other TPS tiles: It's a good idea or it's better to use PICA-X?

P.S.
My call has arrived. On Wednesday I'm going to be deployed on the battlefield.
I thank all of you, my friends, for the help you gave me during these years to write realistic hard-SF novels, and I hope I will continue to post on this forum.
If you don't see my new posts any more pray for me.
I hope you and your families will be safe, and we all will see the light at the end of this tunnel.
Best wishes for all of you

Quaoar

Last edited by Quaoar (2020-04-05 16:17:09)

GW Johnson · 2020-04-07 12:05:03

Quaoar:

We're all thinking of you. Be as careful as you can.

GW

SpaceNut · 2020-04-07 12:14:00

The good news is the flattening of the curve seems to be taking hold in part of your nation at a time when you go to duty.
Be safe in all activity of your profession.

We will be looking for you and your returns of what you can say for the reality that you see.

Best wishes and be safe.

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Re: Elon Musk: "It's game over for all the other heavy lift rockets"

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Re: Elon Musk: "It's game over for all the other heavy lift rockets"

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Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#79 2020-03-25 10:12:44

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#80 2020-03-25 16:45:46

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#81 2020-03-26 04:44:20

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#82 2020-03-26 09:45:38

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#83 2020-03-30 12:02:25

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#84 2020-03-31 01:29:18

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#85 2020-04-01 23:10:17

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#86 2020-04-02 03:43:02

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#87 2020-04-02 08:35:57

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#88 2020-04-02 12:00:17

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#89 2020-04-02 13:01:05

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#90 2020-04-02 15:49:38

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#91 2020-04-02 17:05:39

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#92 2020-04-02 18:33:26

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#93 2020-04-02 18:56:15

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#94 2020-04-03 14:36:56

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#95 2020-04-03 15:16:15

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#96 2020-04-03 15:49:15

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#97 2020-04-05 11:32:27

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#98 2020-04-05 14:53:15

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#99 2020-04-07 12:05:03

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

#100 2020-04-07 12:14:00

Re: Elon Musk: "It's game over for all the other heavy lift rockets"

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