OVERTALK
13th Aug 2004, 06:31
NASA’s RCC Leading Edge Tile Repair Plans Fizzle Out
See AW&ST article below. NASA is practicing their blinkered vision again. Read the article carefully and you'll see that they're trying all but the one measure that would afford real protection......and avoid the necessity for repair, rescue and etc (which measure(s) would remain as a last-ditch fall-back position).
Perhaps someone should suggest to them yet again the concept of a sacrificial glove over the vulnerable inboard leading edge RCC panels. Protects RCC tiles during extended on-pad time (against weather and corrosive gantry leaching contaminants), most importantly effectively shields the brittle carbon RCC tiles against impact during launch and burns away early (ablatively and completely) during re-entry interface super-heating. During launch, because of the low Mach numbers attained, it’s non-critical – and doesn't even have to be 100% conformal.
I sent a couple of explicit emails to their publicized email address way back (at www.caib.us) - but received no acknowledgement and I'm betting that they'd not have been read. I did receive an acknowledgement from Dow Corning that they had a suitable silastic material that would fit the bill (about a 1.5" thick coating out to two-thirds span for the wings' and vertical stabilizer's leading edges). That was also forwarded on to NASA (same email address) and to a few Space Industry Journo hacks - but nothing further was heard from them on that either. Search for “sacrificial” on Pprune and you’ll see where the idea came up some 18 months ago. It would appear that NASA isn't interested in avoidance but is fixated on heroic recovery. A Cart before horse mentality methinks.
NASA Abandons Rigid Overwrap For Patching RCC Holes
By Jefferson Morris
08/11/2004 09:41:02 AM
After encountering "significant technical challenges," NASA is abandoning attempts to develop a rigid overwrap to patch large holes in the space shuttle's reinforced carbon-carbon (RCC) panels in the event of damage during flight, and instead is pursuing other methods that probably won't be ready in time for the shuttle's return to flight, according to agency officials.
The shuttle program plans to fly again in March or April of next year. The Columbia Accident Investigation Board (CAIB) specified that NASA must develop methods of on-orbit thermal protection system (TPS) inspection and repair for the shuttle before that flight. Columbia was lost after foam debris from its external tank punched a large hole in one of the orbiter's RCC leading edge panels.
"The biggest problem with any of the TPS repair techniques outer mold line," Shuttle Program Manager Bill Parsons said during a teleconference Aug. 3. "The second [problem] is how do we connect something like that to the wing?"
Another problem is the variable geometry of the 22 RCC panels that run along the leading edge of each wing, no two of which are the same. "You'd have to make a wrap that would fit with that geometry, because that outer mold line is so important," Parsons said. "So you end up having to build a number of these panels that would be able to fit in the exact right place on the wing."
Instead, NASA is trying to develop a flexible overwrap with new materials, but this solution will not be ready in time for first flight. Other concepts such as sealing the hole with a ceramic filling also are being considered.
Implementation plan
The latest version of NASA's implementation plan for returning the shuttle to flight was released Aug. 3. For fiscal year 2005, a total of $643 million in return to flight initiatives has been approved or is under review, up from a January estimate of $238 million, according to the plan. Better estimates should be available by the fall, NASA said. The agency expects to spend a total of $465 million on return to flight in FY '04, compared with January's estimate of $265 million.
The shuttle and International Space Station (ISS) programs have completed analysis showing that for at least the first two flights following return to flight, if damage is discovered on a shuttle that prevents it from re-entering, it would be possible to launch a rescue mission within the window of time during which the first shuttle crew can be sustained aboard the ISS (DAILY, Feb. 20).
According to John Casper, deputy of NASA's Return to Flight Planning Team, the shuttle program has "conditionally closed" five of the 15 CAIB recommendations that the agency must implement before returning to flight. The Stafford-Covey Return to Flight Task Group has been charged with assessing whether or not NASA has fulfilled the recommendations.
[i]The five recommendations are:
* Develop and implement a comprehensive inspection plan for all RCC panels, using nondestructive evaluation techniques
* Modify the agreement with the National Geospatial-Intelligence Agency (NGA) to make the imaging of each shuttle while in orbit a standard requirement
* Require that at least two employees attend all final closeouts and inter-tank area hand-spraying procedures
* Kennedy Space Center Quality Assurance and shuttle prime contractor United Space Alliance (USA) must return to the industry-standard definition of "foreign object debris" and eliminate any alternate or statistically deceptive definitions like "processing debris"
* Develop an interim program of closeout photographs for all critical subsystems that differ from engineering drawings, and digitize the system so that images are available immediately for on-orbit troubleshooting.
The shuttle program also has closed out several other CAIB recommendations not specifically related to return to flight, according to Casper, and has made significant progress toward eliminating sources of debris from the external tank. "We have made significant progress also in understanding the ascent debris environment and the material characteristics of the TPS, which includes both the tile and the RCC," he said.
Casper said the shuttle program also is proceeding with a long-term plan for hardening the orbiter against debris impacts, which is the subject of another CAIB recommendation. The first phase of this plan includes measures such as adding insulation to the shuttle's front wing spars, changing the carrier panel bolts for forward RCC panels, eliminating corner voids in the main landing gear doors and adding stronger orbiter windows.
See AW&ST article below. NASA is practicing their blinkered vision again. Read the article carefully and you'll see that they're trying all but the one measure that would afford real protection......and avoid the necessity for repair, rescue and etc (which measure(s) would remain as a last-ditch fall-back position).
Perhaps someone should suggest to them yet again the concept of a sacrificial glove over the vulnerable inboard leading edge RCC panels. Protects RCC tiles during extended on-pad time (against weather and corrosive gantry leaching contaminants), most importantly effectively shields the brittle carbon RCC tiles against impact during launch and burns away early (ablatively and completely) during re-entry interface super-heating. During launch, because of the low Mach numbers attained, it’s non-critical – and doesn't even have to be 100% conformal.
I sent a couple of explicit emails to their publicized email address way back (at www.caib.us) - but received no acknowledgement and I'm betting that they'd not have been read. I did receive an acknowledgement from Dow Corning that they had a suitable silastic material that would fit the bill (about a 1.5" thick coating out to two-thirds span for the wings' and vertical stabilizer's leading edges). That was also forwarded on to NASA (same email address) and to a few Space Industry Journo hacks - but nothing further was heard from them on that either. Search for “sacrificial” on Pprune and you’ll see where the idea came up some 18 months ago. It would appear that NASA isn't interested in avoidance but is fixated on heroic recovery. A Cart before horse mentality methinks.
NASA Abandons Rigid Overwrap For Patching RCC Holes
By Jefferson Morris
08/11/2004 09:41:02 AM
After encountering "significant technical challenges," NASA is abandoning attempts to develop a rigid overwrap to patch large holes in the space shuttle's reinforced carbon-carbon (RCC) panels in the event of damage during flight, and instead is pursuing other methods that probably won't be ready in time for the shuttle's return to flight, according to agency officials.
The shuttle program plans to fly again in March or April of next year. The Columbia Accident Investigation Board (CAIB) specified that NASA must develop methods of on-orbit thermal protection system (TPS) inspection and repair for the shuttle before that flight. Columbia was lost after foam debris from its external tank punched a large hole in one of the orbiter's RCC leading edge panels.
"The biggest problem with any of the TPS repair techniques outer mold line," Shuttle Program Manager Bill Parsons said during a teleconference Aug. 3. "The second [problem] is how do we connect something like that to the wing?"
Another problem is the variable geometry of the 22 RCC panels that run along the leading edge of each wing, no two of which are the same. "You'd have to make a wrap that would fit with that geometry, because that outer mold line is so important," Parsons said. "So you end up having to build a number of these panels that would be able to fit in the exact right place on the wing."
Instead, NASA is trying to develop a flexible overwrap with new materials, but this solution will not be ready in time for first flight. Other concepts such as sealing the hole with a ceramic filling also are being considered.
Implementation plan
The latest version of NASA's implementation plan for returning the shuttle to flight was released Aug. 3. For fiscal year 2005, a total of $643 million in return to flight initiatives has been approved or is under review, up from a January estimate of $238 million, according to the plan. Better estimates should be available by the fall, NASA said. The agency expects to spend a total of $465 million on return to flight in FY '04, compared with January's estimate of $265 million.
The shuttle and International Space Station (ISS) programs have completed analysis showing that for at least the first two flights following return to flight, if damage is discovered on a shuttle that prevents it from re-entering, it would be possible to launch a rescue mission within the window of time during which the first shuttle crew can be sustained aboard the ISS (DAILY, Feb. 20).
According to John Casper, deputy of NASA's Return to Flight Planning Team, the shuttle program has "conditionally closed" five of the 15 CAIB recommendations that the agency must implement before returning to flight. The Stafford-Covey Return to Flight Task Group has been charged with assessing whether or not NASA has fulfilled the recommendations.
[i]The five recommendations are:
* Develop and implement a comprehensive inspection plan for all RCC panels, using nondestructive evaluation techniques
* Modify the agreement with the National Geospatial-Intelligence Agency (NGA) to make the imaging of each shuttle while in orbit a standard requirement
* Require that at least two employees attend all final closeouts and inter-tank area hand-spraying procedures
* Kennedy Space Center Quality Assurance and shuttle prime contractor United Space Alliance (USA) must return to the industry-standard definition of "foreign object debris" and eliminate any alternate or statistically deceptive definitions like "processing debris"
* Develop an interim program of closeout photographs for all critical subsystems that differ from engineering drawings, and digitize the system so that images are available immediately for on-orbit troubleshooting.
The shuttle program also has closed out several other CAIB recommendations not specifically related to return to flight, according to Casper, and has made significant progress toward eliminating sources of debris from the external tank. "We have made significant progress also in understanding the ascent debris environment and the material characteristics of the TPS, which includes both the tile and the RCC," he said.
Casper said the shuttle program also is proceeding with a long-term plan for hardening the orbiter against debris impacts, which is the subject of another CAIB recommendation. The first phase of this plan includes measures such as adding insulation to the shuttle's front wing spars, changing the carrier panel bolts for forward RCC panels, eliminating corner voids in the main landing gear doors and adding stronger orbiter windows.