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  Painting the external tank and insulation loss

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Author Topic:   Painting the external tank and insulation loss
mjanovec
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Posts: 3811
From: Midwest, USA
Registered: Jul 2005

posted 08-03-2005 12:48 AM     Click Here to See the Profile for mjanovec   Click Here to Email mjanovec     Edit/Delete Message   Reply w/Quote
For STS-1 and STS-2, the external tank was painted white. From what I've read, the decision to go from a painted tank to an unpainted tank was mostly a weight reduction measure (and some cost savings too).

The question I have is whether debris problems were better, worse, or the same with the painted tanks versus the unpainted tanks. In some regards, I'm wondering if the paint, in any way, held the foam together better...or whether the paint chipped off during flights, only adding more debris to rain upon the orbiter.

Perhaps there is no clear answer to the question...especially if debris wasn't studied in great depth on those early missions. But I would have to think debris was on somebody's mind from Day One.

Any thoughts?

Ben
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Posts: 1917
From: United States
Registered: May 2000

posted 08-03-2005 12:59 AM     Click Here to See the Profile for Ben   Click Here to Email Ben     Edit/Delete Message   Reply w/Quote
From what I've read, there was just as much foam debris with the paint as without. But that information is only from prior discussion of this question (in recent days actually). I don't have any source.

Rodina
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Posts: 836
From: Lafayette, CA
Registered: Oct 2001

posted 08-03-2005 10:29 AM     Click Here to See the Profile for Rodina     Edit/Delete Message   Reply w/Quote
Or, more simply, you could go back to making the foam with CFCs. That stuff is a lot more stable. But let's not let engineering realities get in the way of public relations.

Spacepsycho
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Posts: 872
From: Huntington Beach, Calif.
Registered: Aug 2004

posted 08-03-2005 11:09 AM     Click Here to See the Profile for Spacepsycho   Click Here to Email Spacepsycho     Edit/Delete Message   Reply w/Quote
The paint on the ET weighed about 600 pounds, which was better used for valuable payload. The approximate cost of getting "stuff" into orbit aboard the shuttle is $8,000 per pound, so just to put the paint into space cost about $4,800,000. The paint had little aerodynamic affect and had no bearing on retaining the external tank insulation.

There were no reports of ET insulation coming off during the boost phase before the EPA forced a formula change of the ET material.

From what I've read, after the forced formula change by the EPA, there were at least 30 pieces of ET insulation seen coming off during the boost phase, resulting in nine reported impacts of ET insulation on various orbiters. The worst event leading to the loss of Columbia.

Because the ET foam was so light, nobody thought it was a serious problem or that it would damage the thermal tiles.

I don't understand why NASA wasn't given an exemption by the EPA, but we've all seen the results.

Robert Pearlman
Editor

Posts: 47165
From: Houston, TX
Registered: Nov 1999

posted 08-03-2005 01:53 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Spacepsycho:
I don't understand why NASA wasn't given an exemption by the EPA, but we've all seen the results.
I posted this earlier to another thread, but it appears to be applicable to this discussion as well:

According to Volume 1 of the Columbia Accident Investigation Board's report, on page 51, the tank that flew on STS-107 used foam on its domes, ramps and other areas that were hand shaped that was applied using CFC-11. Further, on page 129, the CAIB reports that while NASA did change blowing agents to reduce its use of CFCs, this only affected areas that were mechanically applied with foam. "Foam that is hand sprayed, such as on the bipod ramp, is still applied using CFC-11."

So the contention that using CFCs would somehow immediately fix the foam problems is not true.

Further, foam shedding was observed and considered a concern on STS-1 and on just about every mission since then.

Ben
Member

Posts: 1917
From: United States
Registered: May 2000

posted 08-03-2005 02:18 PM     Click Here to See the Profile for Ben   Click Here to Email Ben     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Spacepsycho:
There were no reports of ET insulation coming off during the boost phase before the EPA forced a formula change of the ET material.
No, foam has been a problem since April 12, 1981. Paint or no paint, freon or no freon, the foam still sheds. STS-27, the second mission after Challenger, had extensive foam strikes and raised a lot of eyebrows at NASA.

Paul78zephyr
Member

Posts: 733
From: Hudson, MA
Registered: Jul 2005

posted 10-13-2021 06:22 PM     Click Here to See the Profile for Paul78zephyr     Edit/Delete Message   Reply w/Quote
Reviving this 2005 discussion:
quote:
Originally posted by Ben:
No, foam has been a problem since April 12, 1981. Paint or no paint, freon or no freon, the foam still sheds. STS-27, the second mission after Challenger, had extensive foam strikes and raised a lot of eyebrows at NASA.
I don't believe this is correct. From everything I've read the vast majority of the damage to Atlantis' TPS on STS-27 was not caused by the failure of foam insulation on the ET but by — and impact by — ablative insulating material from the nose cap of the the right SRB.

I'm not saying ET foam failure was not on ongoing problem, I'm just saying that on STS-27 it wasn't the main cause of the damage.

oly
Member

Posts: 1296
From: Perth, Western Australia
Registered: Apr 2015

posted 10-13-2021 11:25 PM     Click Here to See the Profile for oly   Click Here to Email oly     Edit/Delete Message   Reply w/Quote
Hoot Gibson relives the harrowing STS-27 experience of being on a classified mission on a damaged space shuttle Atlantis in this Tell Me a Story.

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