Modification of Space Shuttle Tiles?

[Chris Walters]

Hello Lockheedmartin Space Systems
Media Reps Jan Wrather
(303) 971-5967
janet.wrather@lmco.com
Harry Wadsworth
(504) 257-0094
harry.wadsworth@lmco.com

I wanted to ask drop by and ask a brief question for the engineers
Lockheed Martin Michoud Assembly Center. Could the foam covering the
shuttle external fuel tank be coated with a silicone seal similar to
the type commonly used to coat roofs. The substance is water proof,
lightweight, inexpensive and usually guaranteed to last 25 years Would
have asked the engineering staff directly but don't know their email.

Chris Walters

Origional Question On modifying Shuttle
Thermal Tiles

1. Hello a website was set up to ask if it might
be possible to modify the space shuttle thermal
tiles or fuel tanks by interlacing and reinforcing the foam
with titanium wire, kevlar, or some other
substance-online:

http://www.geocities.com/shuttlequestion

2. If the idea is feasiable who would be contacted
at NASA or the contractor?

C Walters
chrissaidthanks2002@yahoo.com

 

[Astronuc]

Reinforcing the Shuttle foam with Kevlar mesh has been proposed. Don't know the status of that at the moment.

I don't believe reinforcing the tiles with interlace wire is practical. Each tile is a wholly separate piece. There is slight gap to allow for thermal expansion. The apprpriate place to reinforce a tile is just below the surface - which is also the hottest zone during reentry. Any metal like Ti would melt or become very soft, and organic material would probably gasify.

 

[Cliff_J]

I watched the show on Discovery a few weeks ago detailing the post-Columbia changes. They showed stuff the team was trying to develop to repair tiles and how the foam application was changed.

I was very surprised that the foam application is a manual process, and when viewing cutaways of the foam on TV, each layer is inconsistent like it would be expected if a human were involved. So a kevlar mesh on the shuttle side to reduce debris to an acceptable size seems so easy it makes little sense why it isn't being used and a reduction applied to the payload capacity to offset the extra weight of the mesh.

Also in regards to the tiles, the focus was on how to repair them once in space. I wonder if a computer simulation today could re-design the tiles so there would only need to be like 8 stock sizes of hexagonal tiles or something, so again the shuttle could carry up some replacements of each size and/or leave the extras on the ISS each time to create a stockpile of easily swapped replacements. At least then all they would need to do is re-examine the adhesion process of each tile and make that possible in space, I assume the adhesion layer is exposed to far less heat and only compressive forces since its protected by the tile. To me this seems far easier than designing a substance that can be applied in a space walk and survive re-entry heat.

I dunno, it seems odd when so much effort is put into optimizing a design that potentially limits the overall success, but since they only seem to get budget cuts and not allocations, it makes more sense.

 

[abercrombiems02]

Why does the foam on the external tank even need to be on the outside of the tank in the first place?

 

[Astronuc]

Why does the foam on the external tank even need to be on the outside of the tank in the first place?

It is easier to fabricate and inspect with the foam on the outside. On the inside, there are the tank support structures and limited clearance between LOX and LH2 tanks and outside shell.

When designing a complex engineered structure, manufactaring and quality control/quality assurance methods must be considered. Sometimes they dictate how something is designed, and sometimes these considerations are not trivial.

 

[Shawnzyoo]

according to national public radio's Science Friday
the foam is predominantly for aerodynamic purposes
it supposedly is a housing to hold cables in place during lift-off
and to reduce drag over the whole section
--shawn

 

[Danger]

I can't help wondering if de-icing the external tank immediately prior to lift-off might reduce stress on the foam enough to prevent it from breaking loose. It seems to me that the launch vibrations would be transmitted to the ice, which would then start tugging on the foam.

 

[Chris Walters]

Bid Process for NASA-Reply

From: "hq-public-inquiries"
hq-public-inquiries@nasa.gov
To: "'Chris W'" <chrissaidthanks2002@yahoo.com>
Subject: RE: UNSOLICITED PROPOSAL
Date: Fri, 29 Jul 2005 17:45:48 -0400


Dear Mr. Walters:

Thank you for your inquiry to NASA.


Under Federal regulation, NASA is authorized to accept technical proposals for evaluation only under one of two conditions: a proposal must either be (1) submitted in response to a formal competitive solicitation; or (2) presented as an unsolicited proposal. The procedure for submitting an unsolicited proposal is described in a NASA guidebook located at http://ec.msfc.nasa.gov/hq/library/unSol-Prop.html. The concept you describe is not structured as an unsolicited proposal as defined by the guidebook. Therefore, as submitted, it cannot be accepted for review. These rules are primarily intended to protect patent rights and copyright privileges of inventors.

Also, included in the above Web site are the respective NASA Centers and their particular technical areas of responsibility under the section entitled, “NASA Research areas and addresses for submission.” Perhaps you can address your questions directly to the respective NASA Center for an expedited response. After you review that information, should you continue to believe that your proposal would be more appropriately aligned with an area of research associated with a particular NASA Center, please forward a valid unsolicited proposal directly to that Center. You are strongly encouraged to follow the instructions as outlined in the “Guidance for the Preparations and Submission of Unsolicited Proposals,” Web site so that NASA Center personnel can process and fairly review your proposal.

NASA hopes that this information will be helpful to you as you pursue your goals. Again, thank you for your letter and interest in NASA.



Public Communications Management Office
NASA Office of Public Affairs

 

[Chris Walters]

Modification Shuttle System Assets

Question Modification of Space Shuttle System[/br]
Based on Improved Use of Existing Assets​

This is a generic idea which NASA refers to as an unsolicted bid to improve the use of existing space assets to extend the life of the space shuttle system and improve safety. It is believed the existing system could be reverse engineered to create a system which has fewer complexities and would be stastically less likely to fail:

#1 Replacement of Shuttle Outer Skin​

1. The shuttle would be stipped of it's various outer thermal tiles to the inner aluminum skin

2. A system of lightweight inner tiles would be place around the inner aluminum skin with an inner gasget of either silicone or other latex.

3. An out skin of possibly of titanium or other high tensile metal would form the shuttle outer skin.

4. We would need to create a small model to show the new configuration of outer skin of metal; inner layer of tiles; and inner layer of aluminium

#2 Revised Mission Profiles​

1. As the shuttle is basically a "space plane" it designed to spend most of it's time in orbit

2. When not in use the shuttle is docked on an oribital pivot or triangle with the other shuttles for maintence; fueling; and other aspects of mission preparation

3. Mission expendables are regularily lofted into orbit by what the Russians currently are experts at "big dumb rockets" which are reported to be magnitudes of order cheaper than shuttle launches and can easily include personnel and even science projects.

4. If the Russians are experts in "big dumb rockets" ask the space partners to use their expertise on this facet of the operations.

5. The shuttle would have to under go modifications to include docking devices on the wing tips; nose; under belly and probally under the tail to accommodate being moved by a remote space tractor.

6. The shuttle revised program requires few if any travels to Earth and has modifications to include refueling in space (details not explained here); ongoing maintence in space by a small resident crew.

#3 Use of Cocoon​

1. The Space Shuttle cocoon is an artifact which is lofted into orbit by "big dumb rockets" and designed to fit over the shuttle like a glove when it returns to earth.

2. The cocoon is metal shaped in the form of the front and sides of the shuttle covered with a extra heavy amount of thermal protection.

3. The space shuttle docks with the "cocoon" and attached by hard points in the nose; wing; and then then begins it decent

4. The cocoon is designed to take all the heat of reentry while permitting the shuttle inside to use it's front thrusters; rear engine; and wing slats to manuver

5. When the Shuttle has decended and slowed enough the cocoon is jetisoned by simply flying the shuttle upside down and backwards where air pressure will cause it to slip off

6. The space shuttle then lands as it would normally

#4 Discussion of Reverse Engineering​

It seems plausible that many of the design flaws in the current space shuttle system were created in the 1970's when engineers tried to incorporate too many new and untried technologies. Reverse engineering and revision of the space shuttle mission profile means the vehicles spend most of their time parked in space instead of the in the hangar. The Shuttle would be used primarily to fly only on missions in space instead of making endless trips too and from the Earth as a sort of low class ferry for shuttle crews.

 

[Astronuc]

I can't help wondering if de-icing the external tank immediately prior to lift-off might reduce stress on the foam enough to prevent it from breaking loose. It seems to me that the launch vibrations would be transmitted to the ice, which would then start tugging on the foam.

Reduction is ice accumulation is what the new heaters are designed to do. Basically one has to prevent water vapor from condensing and then freezing in the shuttle insulaiton. IIRC, the insulation is porous, hence the problem of water vapor getting to the cryogenic lines and freezing.

Ideally one would seal the outer surface of the insulation foam - but that might add mass, unless its a very thin laye. Alternatively, one only needs to seal the region adjacent to the LOX (and LH2) line. However, one issue would be any differential in deformation or shear forces as a result of the differences in properties of the adjacent surfaces.

According to one report, the foam which broke off from ER-121 may have been affect during some repair.

 

[Astronuc]

FYI - a nice overview of the Shuttle's thermal protection system can be found at -http://www.centennialofflight.gov/essay/Evolution_of_Technology/TPS/Tech41.htm

and

http://www.centennialofflight.gov/essay/Evolution_of_Technology/advanced_reentry/Tech20G4.htm

http://www-pao.ksc.nasa.gov/kscpao/nasafact/tps.htm

From Lockheed -

SPACE SHUTTLE THERMAL PROTECTION
Each time the space shuttle orbiter makes its fiery re-entry through the Earth’s atmosphere, a unique structural material called Reinforced Carbon Carbon (RCC) has one of the most demanding tasks of the mission — protecting the vehicle’s nose section, wing leading edges and chin panel against metal-melting temperatures approaching 3,000 degrees Fahrenheit.

RCC, developed by Lockheed Martin Missiles and Fire Control - Dallas, is basically an all-carbon material processed for increased strength and treated to resist oxidation during the orbiter’s encounter with the atmosphere at speeds near 17,000 miles an hour each time it returns from space.

At temperatures devastating to metals, RCC paradoxically increases in strength. It provides excellent shock resistance, permitting rapid transition from 250 degrees below zero (-156 C) in the cold of space to nearly 3,000 degrees above (1,648 C) during re-entry. The material also demonstrates outstanding structural fatigue life, necessary in meeting the design goal of 100 orbiter missions.

Each orbiter wing contains 44 RCC panels which form the leading edge airfoil structure, plus 44 sealing strips and numerous pieces of attachment hardware.

Together with the 4-1/2-foot-diameter nose cap and chin panel, these panels form more than 400 square feet of protective structure for the spacecraft ’s peak heat areas.

The RCC sections and associated insulation limit the temperatures reaching adjacent metal structure in the orbiter to 350 degrees (177 C) during ascent and re-entry, low enough to permit the use of conventional aluminum airframe materials in the vehicle’s design.

- from http://www.missilesandfirecontrol.com/our_products/spaceprograms/SHUTTLE/product-shuttle.html

Another nice historical overview of the TPS - http://history.nasa.gov/sts1/pages/tps.html

 

[Danger]

Very cool info, Astro! Thanks. I haven't been able to follow any of the proposed or incorporated modifications (time factors always work against me), so I was unaware of the heaters. As for moisture entry, could some kind of hydrophylic substance incorporated into the foam itself help? I'm thinking along the line of the silica dessicant sometimes found in medicine bottles or electronics packaging.

Chris;
One problem I see with your proposal is that you are essentially denying the shuttle its original role, which is to be a re-useable Earth to orbit transport. If the thing is going to be used exclusively for orbital work, it would be based upon a lightweight framework with enclosures for crew and cargo. You wouldn't have aerodynamic considerations, or re-entry heat issues, or anything else. You'd still need a regular Shuttle-type vehicle to return to Earth and get back up again. I think also that you're severely overestimating the Shuttle's aerodynamic manoeuvrablility when suggesting the method used to drop the 'cocoon'. The thing flies like a brick.

 

[PerennialII]

Sorry if side stepping a bit - I'm trying to get a grip on the overall criticality and performance of the RCC etc., have you guys come across anything which might enable one to carry out a simplified integrity assessment (or seen one reported somewhere)? Basically I'm thinking about fracture properties of the RCC, some mechanical info was given under links related to these threads.

 

[Chris Walters]

STS 1 & 2 flew with seal over foam

Hello Danger: and thanks for you input. We learned that
the process of sealing the foam was already flown on
STS Missions #1 & #2 as cited further below.

Astronuc certainly did have an excellent idea of placing
stip heaters in a silicone or latex sealer around the
foam.

The Cocoon or anyother proposed system if it could be designed
and engineered would have to be tested in a wind tunnel on
a model before it could actually be installed on the larger
system. Consider Q-Goest previous estimates of $10,000
a pound to lift materials into orbit and then consider the
cost of lifting the shuttle into orbit 123 times. The
billions in costs savings of leaving it in orbit might
have paid for the costs of modifications and purchase of
several more shuttle.

I am somewhat new to physics forms and have made the
mistake of having 2 similar conversations going on at
the same time. Thanks again Danger-Chris


Addressed Too:NASA HEADQUARTERS
Attn: Sandy Russo
Code 210.H
Goddard Space Flight Center
Greenbelt, MD 20771
Sandra.R.Russo@nasa.gov
Office of Space Flight Space Shuttle


It appears that NASA already used and discared Fire Resistant
Latex flown in STS-1 and STS-2 as described in the Book
Space Shuttle by Dennis Jenkins (1996) Library Congress
#9694309. On page 242 Dennis describes the ET Thermal Protection
System to include ETC PR2488 & Ablatos MA 255 and SLA 220.
The Fire Retartant Laxtes was removed to save 545 lbs and
$15,000 of cost to external fuel tank.

I making an unsolicited bid proposal I didn't realize the
idea of using latex or other rubber composite protection over
the foam system was already tried. Chris Walters

cc
Media Reps Jan Wrather
(303) 971-5967
janet.wrather@lmco.com
Harry Wadsworth
(504) 257-0094
harry.wadsworth@lmco.com

 

[Astronuc]

Astronuc certainly did have an excellent idea of placing
stip heaters in a silicone or latex sealer around the foam.

I cannot accept credit for the heater idea - I was simply reporting what NASA/Lockheed has already done. NASA implemented heaters in the foam insulation.

The newly designed heaters will be placed below the fitting, in covers made of a strong alloy composed of nickel, chromium and iron. They will sit on top of a copper plate sandwiched between the fitting and a hard, dense material that separates the heater from the tank.

from NASA approves new design for Shuttle external tank fitting

also -

GASEOUS OXYGEN VENT ARM (“BEANIE CAP”) - on top of External Tank

The Gaseous Oxygen (GOX) Vent Arm, located 265 feet above the launch tower, includes duct tips that were redesigned to provide more efficient delivery of heated gaseous nitrogen. The vent arm extends over the External Tank during prelaunch loading of hydrogen and oxygen to provide a means of preventing ice formation on the ET nose cone. Ice formation presents a debris concern to the tile and wing leading edge panels on the Shuttle. The vent arm has a system of heaters and tubing (ducts) that direct heated gaseous nitrogen to the ET nose cone vents to warm the gaseous oxygen and then carry it away from the Shuttle. The new tips as well as a large section of ducting has been built and installed to preclude any ice debris concern at the top of the External Tank.

GASEOUS HYDROGEN VENT ARM

The Gaseous Hydrogen Vent Umbilical provides a means of safely transporting hazardous gaseous hydrogen, vented during cryogenic loading from six hours through launch, away from the External Tank to the facility vent system. The vent line and umbilical system is located 215 feet up the launch tower and attaches to the tank’s intertank flight umbilical carrier plate, which provides a vent for the liquid Hydrogen tank portion of the External Tank. It also provides a connect point for the tank’s pneumatic and electrical systems.

from http://www.nasa.gov/pdf/112315main_RTF_changes_pk.pdf

and

http://www.nasa.gov/pdf/63908main_Bipod_Fact_Sheet.pdf

PerennialII - I am sure Marshall or Langley have the properties of RCC. For example - http://trs.nis.nasa.gov/archive/00000521/

 

[Chris Walters]

Saving $165 Million per launch

Hello Astro Nuc:

Thanks for your most recent reply. I got a nice reply from Lockheed Martin
which is shown below. Hope whatever they try they test it on a model in a windtunnel first.

I also considered your figure of $10,000 a pound to life the 165,000 empty pounds of the shuttle into orbit at a cost of $165 Million. This goes
back to the idea of enormous saving to leave the shuttles parked in space and use "big dumb rockets" to lift cargo into space as much cheaper.


From: "Buddy Nelson" <buddynelson@mac.com> Add to Address Book
Subject: Re: Submit Unsolicited Bid External Fuel Tank-Research
Date: Tue, 2 Aug 2005 10:21:15 -0700
To: chrissaidthanks2002@yahoo.com
CC: "Michelle Brown" <michelle.a.brown@lmco.com>,
"Jan Wrather" <janet.wrather@lmco.com>,
mary.jo.polidore@lmco.com


Mr. Walters -- Thanks very much for your ideas on the shuttle
external tank.

As you know, despite the foam shedding at the PAL ramp and a couple
other areas of concern, Discovery actually suffered 80% fewer "dings"
than average during launch. Nevertheless, we are working closely with
NASA to address and fix those few areas of the tank that remain
problematic.

We appreciate your suggestions.



Buddy Nelson
Lockheed Martin Space Systems Company
Communications