Cathodic protection of spacecraft

Good news: inert metal compounds such as platinum coated
titanium rods are sometimes used as the anodes. They
do not corrode in marine environment, so they may
survive in the aft end of the spacecraft.

Andrew Nowicki wrote in message ...
Good news: inert metal compounds such as platinum coated
titanium rods are sometimes used as the anodes. They
do not corrode in marine environment, so they may
survive in the aft end of the spacecraft.

...Maybe I'm missing part of the conversation. Why is cathodic
protection of spacecraft needed? Especially if you're using titanium
or platinum, both of which are pretty corrosion resistant already.

Mike Miller, Materials Engineer

Mike Miller wrote:
MM ..Maybe I'm missing part of the conversation.

Here is the entire message:

The outer shell of atmospheric reentry spacecraft
is made of expensive and frail materials. It may
be possible to replace the expensive materials
with cheap tungsten if we can protect the tungsten
shell with cathodic protection. Description of the
cathodic protection:
http://www.teamworknet.com/resourcel...odicProtection

The cathodic protection works well in a conductive
environment, for example marine environment.
When the spacecraft reenters the atmosphere,
it is in contact with electrically conductive plasma.
Inert metal compounds such as titanium rods
coated with platinum are used as anodes in
the marine environment and are very durable.
It is not known if these platinum anodes would
survive in the aft end of the spacecraft. Empty
fuel tank trailing the spacecraft may be used
as a cheap, sacrificial anode.

MM Why is cathodic protection of spacecraft needed?
MM Especially if you're using titanium or platinum,
MM both of which are pretty corrosion resistant already.

Titanium nose cone will not survive without cooling.
Platinum may survive, but it is expensive.
I guess that tungsten with cathodic protection
would be cheaper than platinum without the
cathodic protection.

On Mon, 10 Nov 2003 14:53:38 +0100, Andrew Nowicki
wrote:

How many people read the subject as 'Catholic' protection of spacecraft?

:-|

:-)


--
Steve.

Mike Miller wrote:
MM ..Maybe I'm missing part of the conversation.

Here is the entire message:

The outer shell of atmospheric reentry spacecraft
is made of expensive and frail materials. It may
be possible to replace the expensive materials
with cheap tungsten if we can protect the tungsten
shell with cathodic protection. Description of the
cathodic protection:
http://www.teamworknet.com/resourcel...odicProtection

The cathodic protection works well in a conductive
environment, for example marine environment.
When the spacecraft reenters the atmosphere,
it is in contact with electrically conductive plasma.
Inert metal compounds such as titanium rods
coated with platinum are used as anodes in
the marine environment and are very durable.
It is not known if these platinum anodes would
survive in the aft end of the spacecraft. Empty
fuel tank trailing the spacecraft may be used
as a cheap, sacrificial anode.

MM Why is cathodic protection of spacecraft needed?
MM Especially if you're using titanium or platinum,
MM both of which are pretty corrosion resistant already.

Titanium nose cone will not survive without cooling.
Platinum may survive, but it is expensive.
I guess that tungsten with cathodic protection
would be cheaper than platinum without the
cathodic protection.

Andrew Nowicki writes:

Mike Miller wrote:
MM ..Maybe I'm missing part of the conversation.

Here is the entire message:

The outer shell of atmospheric reentry spacecraft
is made of expensive and frail materials. It may
be possible to replace the expensive materials
with cheap tungsten if we can protect the tungsten
shell with cathodic protection. Description of the
cathodic protection:
http://www.teamworknet.com/resourcel...odicProtection

The cathodic protection works well in a conductive
environment, for example marine environment.
When the spacecraft reenters the atmosphere,
it is in contact with electrically conductive plasma.
[...]
Titanium nose cone will not survive without cooling.
Platinum may survive, but it is expensive.
I guess that tungsten with cathodic protection
would be cheaper than platinum without the
cathodic protection.

You are confusing the _ELECTROLYTIC CORROSIION_ of disimilar metals
immersed in salt water with high-velocity plasma erosion; these two
processes have _ABSOLUTELY NOTHING TO DO WITH EACH OTHER_. One is
the result of chemistry, while the other is the purely thermo-physical
result of ridiculously high temperature atoms striking a material
at ridiculously high velocities.

Please _do_ try to learn some basic physics and chemistry, so that
you will not make quite so many utterly false analogies.


-- Gordon D. Pusch

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

"Steve" wrote ...
On Mon, 10 Nov 2003 14:53:38 +0100, Andrew Nowicki
wrote:

How many people read the subject as 'Catholic' protection of spacecraft?

I thought they didn't believe in it.

Andrew Nowicki wrote in message ...

Titanium nose cone will not survive without cooling.
Platinum may survive, but it is expensive.
I guess that tungsten with cathodic protection
would be cheaper than platinum without the
cathodic protection.

If you're going to use a tungsten heat shield (especially with
platinum anodes), you can afford to coat the tungsten with a flash of
iridium for passive oxidation protection. You don't need to get into
sacrificial cathodic protection (requiring replacement) or impressed
currents (electrical equipment that can break down).

A few grams of iridium per square meter of tungsten will be
affordable, even if you need exotic deposition processes to put it
down. Figure 28 grams of iridium per square meter and the raw material
cost is only around $400 for the iridium (per square meter.)

Heck, you might end up beating out carbon-carbon heat shields on price
for an iridium-plated tungsten heat shield. (I recommend
tungsten-rhenium alloys, actually, for their low temperature
toughness).

Mike Miller, Materials Engineer

How many people read the subject as 'Catholic' protection of spacecraft?

Who's the patron saint of space travel?

Peter

On Fri, 14 Nov 2003 12:32:50 -0500, Peter Gardner
wrote:

Who's the patron saint of space travel?

Peter


St. Christopher?

:+)

James