Re: Shuttle Rocket Booster Foam

On Fri, 29 Apr 2005 14:44:18 +0000, Craig Fink wrote:

> On Fri, 29 Apr 2005 11:54:17 +0000, Jorge R. Frank wrote:
>
>> "Cindy Chambers" <cchambers777@xxxxxxxxxxx> wrote in
>> news:_9udnRzqLOJXNezfRVn-qw@xxxxxxxxxxx:
>>
>>> Exactly what does the foam do? Is it insulating the shuttle from the
>>> tank?
>>
>> The foam on the external tank (ET) performs three functions:
>>
>> 1) Protect the ET from aerodynamic heating during ascent.
>
> A small subset of the larger group called insulation on the Tank. Taking
> all the insulation required prelaunch to orbit is overkill.
>
> Take a look at page 123 of CAIB report, notice all the charring on the
> external tank for STS-7 (Figure 6.1-2). Compare that to STS-112 (Figure
> 6.1-3) there's no charring. It's really debatable as what is protecting
> what. Is the foam protecting the huge heat sink, or is the huge heat
> sink protecting the foam?


Reduce the thickness of the foam, the R value goes down and more heat
flows. Conversely, it could be thought of as cold flowing the opposite
direction. The inner cold aluminum side of the tank becomes slightly
warmer, and the outside, the foam surface of the tank becomes slightly
colder. The rate of flow has increased. So the foam is being actively
cooled by conduction through the insulation.

Prettier tank pictures in orbit, but colder on the ground too and possibly
more ice.

> Why does the STS-112 tank look so much clean as compared to the STS-7
> tank? There is less insulation on the STS-112's tank, so surface of the
> foam is being cooled by the huge heat sink.
>
> Better yet, look at the ET presentation.
>
> http://www.caib.us/events/public_hearings/20030407/present_et.html
>
> Page 1, ET foam's purpose.
>
> Page 15, Aerodynamic Heating, look the very limited acreage called hot
> spots.
>
> Page 20, STS-26 ET in orbit picture, lots of charring
>
> Ditto Page 21, STS-32R, Page 22...

Anybody have any other pictures of the ET after the decrease in thickness
of insulation?

Seems only STS-112's picture is in the ET presentation.

> Page 26, A chart of effort to reduce ET debris. STS-87, ET#-89, was the
> precipitating event that caused the ET group to finally make a change
> that started to reduce debris. The EPA mandated changes had made the
> debris situation worst. What changes were made to improve the debris
> situation. The chart says, "Reduced foam thickness" and "incorporated
> ?verri? holes".
>
> After this change, look at the ET in orbit picture on page 32 (STS-112),
> what a difference the reduced foam thickness has made with respect to
> charring. The few aerodynamic hot spots (Page 15) are still visibly
> charred, but all the excess foam on the tank is really pretty, looks
> like it just rolled out of the factory. The foam is definitely being
> protected by the huge heat sink that the tank is.
>
> And then there is Page 51, a really good chart showing foam thicknesses
> and what it's there for. A lot of it's for ice/frost and entry heating.
> It shows the Ascent Heating area's too, but the picture on page 32 is
> probably best illustration of were and how big the ascent hot spots are.
> Really not that much insulation acreage.


Page 56, peak aero heating during ascent for the ET is at around 100
seconds. So, the tank is still pretty full at peak heating. Also,
interesting is that the "TPS cell burst" builds up after the loads on the
foam begin to decrease.


>> 2) Prevent ice formation on the exterior of the ET.
>
> A prelaunch function.
>
>> 3) Minimize ET propellant boil off.
>
> A prelaunch function.

4) Entry Heating

5) RTLS Heating

--
Craig Fink
Courtesy E-Mail Welcome @ WeBeGood@xxxxxxxxx
.

Relevant Pages

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