Reusable TPS in the Ocean?

(quasarstrider) writes:

(Henry Spencer) wrote in message ...
In article ,
Kees van Reeuwijk wrote:
Delft University in the Netherlands has a test vehicle that uses an
internal water cooling system, see
http://dutlsisa.lr.tudelft.nl/dart/introduction.html. As far as I
known, this design has been flown, but landed on land.

By the looks of the web site, it hasn't flown yet, but it's hard to be
sure...

The guys who made the X-33 tile system seemingly worked on active cooling
at a certain point. See:
http://www.aerostructures.goodrich.com/html/rd_tps.asp

The history of just about every "reusable" spacecraft seems to _start out_
with ambitious plans that initially include "active cooling" --- which are
quietly replaced by passive insulation later on due to budget constraints...


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

(Mike Miller) wrote in message . com...
(SpaceSavant) wrote in message . com...
wrote in message ...
Can someone think off the top of their head of suitable materials for
use as reentry shielding/ external shell material that are compatible
with either a fresh water or salt water environment after reentry?

You may also want to check into Titanium and its alloys. It's widely
used in sal****er industrial processes and the material of choice for
submergence.

It does have excellent corrosion resistance, but titanium and its
alloys are only fit for "warm" applications, rarely being able to
handle the temperatures found in leading edge/belly re-entry
environments (or gas turbines).

For actively cooled TPS (transpirational cooling, for example),
titanium has an abysmal thermal conductivity (11-12 W/m*K vs 247 for
aluminum and 400 for copper) that'll make it hard to carry away heat.

Mike Miller, Materials Engineer

Actually, I am aware of it's low thermal conductivity of the alloys,
although at this point I'd probably debate the statement, "it's hard
to carry heat away".

Titanium alloys are used in high temperature heat exchangers in the
ocean and for tubing in geothermal vents for example and also on
unmanned submersibles in waters at 800 degrees range. In the
submersible case in particular, the titanium MUST be kept at low
temperature to avoid hull destruction due to pressure. THe only
limiting factor for the sub is the size of the cryogenic tank. The sub
is closer to what I was aiming at, my current reentry trajectory, has
the craft quite fluffy and less ballistic, so longer heat exposure
less extreme flux etc.

In fact one of the main problems they had with the submersible was
parts of it getting too COLD as water temperature changes caused ice
or flake to form.

Although, even at higher ballistic reentry profiles, they seem
confident they could handle it, but I'm not comfortable with those
profiles and it seem to push the edge of the alloy technology which I
am never comfortable with.


Either way, the engineers who suggested this, have the data on the
reentry profiles for a couple of current craft and they have no
problems with it. I'll have to take their word for it at the stage of
my study. They do this work for a living, while they dont do aerospace
work yet, thermal laws dont change.

They wont of course expand on the RFI response until money is
forthcoming but that's the devil in the detail that will have to wait
until I sort out the rest of the proposal.

(Mike Miller) wrote in message . com...
(SpaceSavant) wrote in message . com...
wrote in message ...
Can someone think off the top of their head of suitable materials for
use as reentry shielding/ external shell material that are compatible
with either a fresh water or salt water environment after reentry?

You may also want to check into Titanium and its alloys. It's widely
used in sal****er industrial processes and the material of choice for
submergence.

It does have excellent corrosion resistance, but titanium and its
alloys are only fit for "warm" applications, rarely being able to
handle the temperatures found in leading edge/belly re-entry
environments (or gas turbines).

For actively cooled TPS (transpirational cooling, for example),
titanium has an abysmal thermal conductivity (11-12 W/m*K vs 247 for
aluminum and 400 for copper) that'll make it hard to carry away heat.

Mike Miller, Materials Engineer

How about the Nickel based alloys, some of those seem corrosion resistant.
For the actively cooled TPS on temperature sensitive surfaces, Gold seems
to be corrosion resistant, have good thermal conductivity and a low
coefficient of linear thermal expansion, but then again, it is probably
too heavy, not to mention expensive. :-)

Couldn't you just nickel or gold plate something like copper to make it
corrosion resistant for the high-temperature TPS?

(SpaceSavant) wrote in message om...

Titanium alloys are used in high temperature heat exchangers in the
ocean and for tubing in geothermal vents for example and also on
unmanned submersibles in waters at 800 degrees range.

Which is fairly cool compared to re-entry.

Either way, the engineers who suggested this, have the data on the
reentry profiles for a couple of current craft and they have no
problems with it.

Could you post the links to the papers/websites suggesting a titanium
leading edge/belly heat shield?

Mike Miller, MatE

(Henry Spencer) writes:

The most promising reentry protection approach for either of these is
active cooling, either transpiration or circulation, with heat-sink as a
runner-up. (Ablators are fine too, but I assume you want reusability.)
Heat sinks would be copper, beryllium, or beryllium-based composites.
Active cooling would quite likely be either copper or aluminum, with a
small possibility of steel. Copper and beryllium don't get along with
seawater, steel is better, aluminum is fine.

Aluminum is fine?

I thought aluminum had problems with seawater unless protected with
various coatings (such as "anodizing," which I think is mostly a much
thicker layer of alumina than normal; some forms of anodizing are
advertised as more corrosion resistant than others, but I don't recall
the details off hand); however, I'm not sure how well the anodizing
coating stands up to the usual reentry heat loads. I seem to remember
that some of them are *hydrated* alumina.

There may be similar problems with whatever other coatings you
might apply on aluminum, or steel, or whatever else your material
of choice is.

Finally, there's the problem of various types of electrolytic
corrosion... I think that's the term, right?

pgf

(Henry Spencer) wrote:
Phil Fraering wrote:
Aluminum is fine?
I thought aluminum had problems with seawater unless protected with
various coatings...

Taken care of properly, it's okay in that environment (bearing in mind
that it generally won't spend long periods actually immersed). Note rows
of aluminum aircraft on aircraft carriers.

Note rows of aluminum aircraft that have protective coatings and
*still* require intensive maintenance and inspection. The problem
isn't just immersion time, but how long the shield is left before it's
cleaned, and salt air getting at the innards and being left uncleaned.

You can't simply haul it out of the water, give the bottom of the
shield a freshwater wash and call it good. Apollo didn't sweat the
long term corrosion potential because they were not going to be
reused, but if you are routinely going to land a reuseable capsule at
sea, then you have some real maintenance problems on your hands.

Even just an occasional sea landing will mean increased maintenance
loads. (Maybe just a slight overlay on top of existing inspection and
maintenance cycles, maybe something greater. Depends on the details
of the operational concept and specifics of vehicle design.)

It's not a huge or insurmountable problem, but it's not one that can
be ignored.

Right. Having different metals in electrical contact with each other and
in contact with seawater is bad, because they'll form a battery, and one
of the metals will start losing metal atoms into the water. But this is
a long-term problem rather than something affecting short exposures, by
and large.

Not really. If you have salt air condense inside the craft, you end
up leaving salts behind that can cause electrolytic corrosion in
conjunction with normal atmospheric moisture.

D.
--
Touch-twice life. Eat. Drink. Laugh.

In article ,
Derek Lyons wrote:
a long-term problem rather than something affecting short exposures, by
and large.

Not really. If you have salt air condense inside the craft, you end
up leaving salts behind that can cause electrolytic corrosion in
conjunction with normal atmospheric moisture.

That can be a problem even when no salt air is involved. XCOR lost all
electrical engine controls on the 11th flight of the EZRocket, thanks to
salt-water corrosion in the desert! "In Mojave, all water is salt water".

(Their FMEA revealed that having the engines quit on loss of electrical
control power was a bad idea -- what if it happens just after takeoff? --
so they stay running if that happens. There's a redundant *mechanical*
cutoff, but they normally run the engines to propellant depletion anyway.)
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

Can you glassify Aluminium?

Mike



Phil Fraering wrote:

(Henry Spencer) writes:

The most promising reentry protection approach for either of these is
active cooling, either transpiration or circulation, with heat-sink as a
runner-up. (Ablators are fine too, but I assume you want reusability.)
Heat sinks would be copper, beryllium, or beryllium-based composites.
Active cooling would quite likely be either copper or aluminum, with a
small possibility of steel. Copper and beryllium don't get along with
seawater, steel is better, aluminum is fine.

Aluminum is fine?

I thought aluminum had problems with seawater unless protected with
various coatings (such as "anodizing," which I think is mostly a much
thicker layer of alumina than normal; some forms of anodizing are
advertised as more corrosion resistant than others, but I don't recall
the details off hand); however, I'm not sure how well the anodizing
coating stands up to the usual reentry heat loads. I seem to remember
that some of them are *hydrated* alumina.

There may be similar problems with whatever other coatings you
might apply on aluminum, or steel, or whatever else your material
of choice is.

Finally, there's the problem of various types of electrolytic
corrosion... I think that's the term, right?

pgf

Abrigon Gusiq wrote in message ...
Can you glassify Aluminium?

Plain aluminum? Sure, in ultra-thin foils by splat cooling and other
ultra-fast cooling techniques. Pure elemental metals and lightly
alloyed materials crystallize very, very fast. You need cooling rates
on the order of 1 million degrees per second to glassify them.

By the time you find an aluminum alloy more conducive to
vitrification, you've got an alloy that isn't much like normal
aluminum alloys at all, and it still has all the manufacturing
headaches of amorphous metals.

It'd be much easier just to anodize the aluminum or select a more
corrosion resistant alloy to begin with.

Mike Miller, Materials Engineer

Abrigon Gusiq wrote:
Can you glassify Aluminium?

Can you make a telescope with wood?

"Glassy" metals have a wide variety of metals in, the aluminium if any
would be only one component of many.
It's not very meaningfull to classify any resulting metal as "aluminium"
even though it might have some in.