Re: The Cold Equations

"tomcat" <jlavine@xxxxxxxxxxxxx> wrote in
news:1133582763.214522.308260@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:

>
> Jorge R. Frank wrote:
>> "tomcat" <jlavine@xxxxxxxxxxxxx> wrote in
>> news:1133476681.252722.276050 @o13g2000cwo.googlegroups.com:
>>
>> > NASA is knocking titanium because it is covering up an error made
>> > back in the 70's.
>>
>> Really? I don't suppose you could produce a single citation of NASA
>> "knocking" titanium, could you?
>
>
>
> NASA pointed out, probably accurately, that if titanium had been used
> for Shuttle Columbia's skin the 'skin melt' would only have taken 13
> seconds longer. Aluminum melts at about 1000 deg. F., while titanium
> can hold out to about 2000 deg. F.

Really? Where did "NASA" point that out? That 13-second number came from
the CAIB, not NASA.

> Long ago, circa 1970, NASA had quite a feud over using 'steel' rather
> than aluminum for the Shuttle. Whether or not this was 'titanium
> steel' they were considering is uncertain. Steel, though denser than
> aluminum, is much stronger than aluminum as well. Steel can be,
> therefore, thinned to half the thickness of aluminum resulting in very
> little, if any, weight increase for the required strength.
>
> Aluminum was in vogue back in the 70's. It could be purchased cheaply
> and was easy to work with. The aviation industry was used to working
> with 'aircraft grade' aluminum. The cost of the Shuttle was of
> concern. So, a decision was made to go with aluminum, not steel.
>
> Today, we know that 'steel' would have been the better choice.

No, you don't "know" that. And stop using 'steel' as your codeword for
titanium; we all know what your particular hobby-horse is. As Henry
Spencer pointed out, titanium has poor thermal conductivity compared to
aluminum. When exposed to localized heating, as in the case of Columbia,
aluminum tends to spread the heat out a lot more, so although it has a
much lower melting point, it tends to reach that melting point more
slowly.

> Today,
> we also know that 'composite' is superior even to steel for most
> applications. The B-2 bomber and the F-22 are both made of composite
> materials.

Neither of them experience temperatures anywhere near what the shuttle
experiences.

> Niconel and ablatives are used on the Shuttle for heat dissipation as
> well as the ceramic tiles. It makes one wonder that if titanium had
> been used under the ablative blanket in the wheel well, if it might
> have held up. NASA says "no."

No, the CAIB says "no", unless you can produce a quote from NASA saying
otherwise.

> And, frankly, I don't know.

I'm not surprised. There's a lot you don't know.

> Today, we know that the extreme air friction of hypersonic flight was
> not exaggerated in the physics calculations. It takes careful
> engineering and the use of ceramics to defeat it. But it can be done.

It might help if you actually applied some careful engineering rather
than pulling ideas out of your ass.

--
JRF

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