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Exposing an object to 1500° C does not instantly make the object 1500° C. The actual capsule temperature is different than the temperature of the gas passing over it. The abort motor burns for only a couple seconds, thus the temperature to which the exhaust heats the capsule is far less than 1500° C. The aerodynamic heating that occurs during boost is a more serious thermal issue.Originally Posted by gaetanomarano
Last edited by Bob B.; 2007-Feb-19 at 08:45 PM. Reason: grammar
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Also note that -as I've said multiple times- during re-entry a slightly protective boundary layer (stagnation layer) forms, which is quite less pronounced in the ascent attitude.
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if YOUR "upper thermal shield" is "ablative" (then BRUTALLY "ablated" by our atmosphere between 30 and 60 km. of altitude...) its extra-mass will NEVER reach the earth orbit, while, if it is "non-ablative" that extra-mass will be (simply) DETACHED (with the Orion's Nose Cone and the Ares-I's 2nd stage) in the elliptical orbit (and burned in the atmosphere) ...but you (quietly) want/try to forget/hide that THIS is the main/only (Apollo/Orion) BPC's purpose/dimension/mass/thickness:
image (c) Wikipedia
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LOL. Who's the one ignoring all our quotes on what is the BPC's use? You are the one putting fingers in your ears and saying it's just to protect against the LAS tower firing. That is wrong as we've shown with quotes from for example Boeing.but you (quietly) want/try to forget/hide that THIS is the main/only (Apollo/Orion) BPC's purpose/dimension/mass/thickness:
Note that a Progress capsule, featuring no LAS tower, is placed inside a protective fairing too.
And there is a huge difference between "main" and "only", so pick one.
Note that your ablative shield -which will indeed get lighter during launch but will not be totally gone if you want any protection and safety for underlying things- will not allow for a good thermal control such as a clean, BPC shedded Orion will. And thermal control is important in space. It will make design less efficient and far more difficult. With a BPC, you can design your capsule such that it is optimal for in space conditions and just survives re-entry, without having to worry a lot about ascent conditions. Those are being handled by the BPC. And this BPC is detached after ascent, removing its mass in its entirety for the path from LEO to luna and back.
(does anyone else see the exhaust isn't directly hitting the capsule in that picture?)
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the Apollo LES burn time was 5 seconds... however, I agree with you that 5 seconds at 1500 °C doesn't means the capsule reaches 1500 °C of temperature... infact (for the SAME reason) I don't think/believe that, after (only) 20 seconds at (only) 400 °C of thin-air hot flux, the Orion external surface may (really) reach 400 °C of temperature... maybe... 200 °C is a more relistic figure... also, in my "pizza-example" I forgot to say that a pizza's oven needs one-two hours to reach the right temperature to cook a pizza... (485 °C)
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Note that the burn is "nothing at all - 5 seconds burn - nothing at all".
The ascent profile makes everything heat up, increase loads, increase depth of heat, slowly during ascent, until the maximum load period is reached. So it isn't just 20 seconds.
Quit the pizza oven example, it doesn't blow air at mach 6 onto the pizza. And yes, that does matter. Heat channeling, for a start. You say the pizza oven needs time to warm up. Irrelevant. Air stagnation temperature increase is totally uncomparable to that. Slow down air from mach 6 to stagnation in 1 second, and that air will be 2500°C. So your capsule's "oven" is on temperature virtually instantly. Even that aspect of the pizza over example cannot be compared.
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since I don't like the obvious, I hate to say/post the obvious... but, since you ask me that... I just remember to you that vehicles like Soyuz, Progress and Shenzhou are the LESS aerodynamic objects we can imagine! ...also, the fairing is absolutely necessary to protect from launch dozens of (VERY FRAGILE) antennas, sensors, solar panels, etc. that these vehicles have on their surface (and they need to fly in space, dock, etc.)
my opinion is that a BPC is unnecessary with the newLAS (then, my choice is "only") ...however, assuming (just another second...) that you're right, the BPC can't be so "big, heavy and thick" just to protect the capsule from hot-air... then, "main" means "70-90% to protect from LAS motors"...there is a huge difference between "main" and "only", so pick one...
since the Apollo LES was never used to abort in a real flight (and the '60s color cameras was very big and heavy to make a picture like this from high altitude LittleJoeII's abort tests) the LES picture in my post can only be a launch-pad test ...then, you must add the capsule's supersonic speed to imagine/know the REAL "in-flight-abort" effect......does anyone else see the exhaust isn't directly hitting the capsule in that picture...
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It is detached even before then. The BPC is jettisoned along with the LAS tower fairly early during the second stage burn. The mass penalty the BPC imposes on the payload delivered to orbit is very small -- probably only about 30-35 kg in the case of Orion.
Yes.(does anyone else see the exhaust isn't directly hitting the capsule in that picture?
The 2 second burn time I quoted is for the Orion LAS.
According to Boeing the temperature was 1,200 degrees for Apollo, though they don’t say what scale. Our choices are (with Celsius conversion):
1200° C = 1200° C
1200° K = 927° C
1200° F = 649° C
1200° R = 394° C
So no matter what scale Boeing is using, the answer is higher than 200° C.
Mmm … Pizza. You’re making me hungry.
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Exactly the same argument can be made for Orion's in orbit system such as thermal radiators, parachute holes, exhausts, antenna's... Having them protected with a cover during ascent makes this design far more easy.since I don't like the obvious, I hate to say/post the obvious... but, since you ask me that... I just remember to you that vehicles like Soyuz, Progress and Shenzhou are the LESS aerodynamic objects we can imagine! ...also, the fairing is absolutely necessary to protect from launch dozens of (VERY FRAGILE) antennas, sensors, solar panels, etc. that these vehicles have on their surface (and they need to fly in space, dock, etc.)
Your opinion doesn't count, reality counts. I am not the one being right, I am quoting Boeing, people who designed the Apollo BPC. if they don't know why they built the thing, nobody does. The 70-90% figure again is pulled out of thin air. "just from hot air" once again shows you don't realize what hot air can do. And it shows that you still had your fingers in your ears when we listed other uses for the BPC.my opinion is that a BPC is unnecessary with the newLAS (then, my choice is "only") ...however, assuming (just another second...) that you're right, the BPC can't be so "big, heavy and thick" just to protect the capsule from hot-air... then, "main" means "70-90% to protect from LAS motors"
Yes that's true, the remark was simply an attempt at humour on showing the BPC protecting against exhausts with a pic showing exhausts not hitting the BPC. But anyway, Apollo designers told us that only the windows would get critical damage in an abort, so that alone shows that the BPC has more uses than LAS protection.since the Apollo LES was never used to abort in a real flight (and the '60s color cameras was very big and heavy to make a picture like this from high altitude LittleJoeII's abort tests) the LES picture in my post can only be a launch-pad test ...then, you must add the capsule's supersonic speed to imagine/know the REAL "in-flight-abort" effect...
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from this Wiki article: "The crew were subjected to an acceleration of 14 to 17 G's for five seconds. Reportedly, the capsule reached an altitude of 2000m (6500 feet) and landed 4 km (2.5 miles) from the launch pad."
the Ares-I 1st stage burn time will be two minutes and a 5 seconds... the Ares-I needs half of this time to reach 12 km. and Mach 1.6 ...probably, it needs a further 30-40 seconds to reach the altitude and speed of a some military fighters (25 km. and Mach 2.5)... a few seconds after the 2nd stage burn the LAS is jettisoned... so, the total time the Orion will experience (both) a Mach 3-6 speed AND a dense atmosphere is around 20-30 seconds MAX...the maximum load period is reached. So it isn't just 20 seconds...
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I don't know why you put that first part of your reply. Are you trying to prove, disprove, or expand on anything said before? Also, your incomplete quotation -that also lacks the parentheses- doesn't make clear I meant that the burn lasted for only 5 seconds.
The second part of your reply shows you don't get my point. Before reaching the maximum point, the capsule gradually goes towards that maximum, so it has time before that to heat up. Before reaching the maximum, heating has been going on. Before the LAS burn, no heating due to LAS engines has been going on. That was my point. Added to that is Bob B's overview of max temperature found on Apollo, also showing that 200°C is an unlikely low estimate.
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Here is another webpage that says...
And this one says...Boost Protective Cover (BPC)
Height : 11ft (3.35m)
Diameter : 13ft (3.96m)
Weight : 700lb (318kg)
Production :
This is the white cover on the CM, protecting it from the exhaust heat of the LES and air friction heat during launch. It is made of honeycomb cored-laminated fiberglass and cork. There are 12 RES engine blow-out ports and an 8in diameter window over the left CM rendezvous window. It jettisoned from the CM with the LES.
EDIT:1969 March 20
Deletion of Apollo CSM boost protective cover rejected
ASPO Manager George Low wrote NASA Hq. - referring to a briefing of George Low at Downey on October 25, 1968 - that "MSC has reviewed the possibility of deleting the CSM boost protective cover. We have concluded that deletion . . . would require the following spacecraft modifications: a. A new thermal coating would have to be developed to withstand the boost environment. b. Protective covers would have to be developed for the windows, EVA handholds, vent lines, etc. . . . We have further concluded that a resulting overall weight reduction is questionable, and . . . have therefore decided that the cost of this change could not be justified and that the boost protective cover should be retained."
Here's one more:
Boost Protective Cover - It is made of layers of impregnated fiberglass, honeycomb cored-laminated fiberglass, and cork. It has 12 "blow-out" ports for reaction control motors, vents, and an 8-inch diameter window in front of the commander's forward viewing window. It completely covers the command module to prevent charring of external surfaces during boost out of the earth's atmosphere. It is jettisoned with the launch escape tower assembly.
Last edited by Bob B.; 2007-Mar-02 at 04:48 PM.
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It will require some very thick fingers...
Another source (Wikipedia) also mentions impact protection.
I haven't found references for aerodynamic enhancements and increased ease of capsule design (though the latter is partially implied in the second quote) yet, but I think those are quite straightforward.
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That would seem to finish the argument fairly effectively Bob. Not that I expect our friend to take his fingers out of his ears. I predict his next post will totally ignore this quote.
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a spacecraft can be small or big, manned or un manned, capsule or winged, built for LEO or the Moon, but it's first step always is a flight to LEO, so, EVERY spacecraft must face the similar accelerations, speed, altitude, forces, temperatures, etc... the only difference is between orbital and lunar spacecrafts, with the latter built more resistant to temperatures since they must re-entry at higher speed and much higher TPS/sidewall/top temperatures (WITHOUT any BPC, nose cone, or other protection...)
Mercury was a very little and simple capsule built with '50s technologies and materials but WITHOUT a BPC since its tower-LAS was joined to the top of the capsule... the (triconic...) Gemini was similar to Mercury and built with (similar) '60s technologies and materials but WITHOUT any BPC nor a tower-LAS ...the top cone was NOT a BPC but (simply) the parachutes' protection cover and was not jettisoned at high altitude like a LAS but on re-entry (look at the several Gemini images on the web or the Bob B. avatar...)
Soyuz, Progress and Shenzhou need a fairing since great part of these ships are not so aerodynamic to fly alone and have many antennas, solar panels, etc. that other vehicles don't use (Apollo and Shuttle used fuel-cells) or protected by interstage fairings (like the Apollo antennas)
Apollo had a tower-LES and a BPC but (I think) it was mainly to protect it from the 1500°C LES engines' flames rather than the (30-60 km.) "hot-air" (however, I will examine this point ahead in this post)
if the earth-LEO ascent is so "dangerous" (only between 30 and 60 km...) for a capsule (that is small and very aerodynamic) it MUST be 100 TIMES more dangerous for a Shuttle since it has giant surfaces, wings, more and bigger windows (some in the less aerodynamic possition, just IN FRONT of the flight direction and the main air flow) ailerons, rudders, aerobrakes, many attitude jets (and some IN FRONT of the flight direction and the main air flow) great part of its sidewall fuselage and cargo-bay door has a protection for 370°C MAX (not 400°C or 650°C...) and the cargo-bay door is 4.5 m. large and 18 m. long and (both) the cargo-bay and the full Shuttle have HUNDREDS METERS of places very good for your "heat channelling" but WITHOUT any BPC or protections...
but, despite a Shuttle on ascent faces the SAME forces and temperatures of EVERY spacecraft (and has 100 times the "problems" of a capsule without BPC) it has accomplished EIGHT TIMES the Apollo earth-LEO flights WITHOUT any BPC or other extra-protections...
I think that an Orion, built with 2010's technologies and materials (and ALREADY able to resist 10+ minutes at re-entry on sidewall and top to temperatures between 800°C and 1300°C without any BPC, nose cone or other protection cover) absolutely IS able to resist (WITHOUT any BPC but only a nose cone) to (only) 20-30 seconds of (only) 400°C hot-air ...use a BPC for the "hot-air" is like use a thin sheet of cooking aluminium to "protect" an Abrahams Tank...
however, let's examine the problem in deep, assuming that a BPC is "absolutely necessary" for (both) hot-air protection AND solid motors flames...
about the LES burning time... from page 2-1 of this NASA document you can read that a REAL Apollo LES had a burning time of "approximately 8 seconds" ...then, NOT only 5 seconds (Wiki) nor 3.5 seconds (Apollomaniacs)
the "2 seconds" figure in the Orion's LAS factsheet clearly is WRONG, since, if the Orion must be carried 2000 m. away from the Ares-I on abort, "two seconds" of thrust means 1000 m/sec. or 60 km/min. or 3600 km/h and (compared with the 14-17G of the 8 seconds Apollo-LES thrust) about 40G for the astronauts... TOO MUCH
also, a last week news say that the Orion's LAS will be "less harrowing" than Apollo, then, its thrust will be "modulated" to have less G for the astronauts (but a longer burning time ...maybe... 10-15 seconds)
to better understand the REAL effects of 8 seconds of the LES motors' flames on a capsule, look at THIS Apollo-LES' pad-abort-test image from a NASA Dryden Flight Research Center document
again... don't forget that this is a pad-test from ground and zero starting speed... just imagine what may happen if you add the speed of a rocket... the 1500°C LES abort motors thrust directly hit (up to 8 seconds!) to the capsule surface may acts like an Oxyhydrogen Flame !!!
then, we must approach the "BPC problem" under another point of view, with a further example:
just imagine you have a shop with some display-windows... if you sell shirts or toys in your shop, all display-windows can be made with a common 5 m/m glass ...but, if you want to sell high-priced JEWELS (with hundreds of thousands or millions dollars of value in your display-windows) you need a strong 30 m/m armoured Bulletproof glass!!!
of course, if in your shop (e.g.) you sell (both) low cost toys and high priced jewels, your shop's display-windows must be ALL "bulletproof"!
well, we can imagine a standard Apollo/Orion BPC like a mixed (400°C hot-air) toys-shop AND a (1500°C abort motors flames) jewels-shop, while, if we put the Abort Motors UNDER the Orion, the BPC (that I still think is completely UNNECESSARY) must resist only to small forces and lower temperatures
about the BPC... don't forget that my latest Orion design already HAS part of your BPC on its top: the light Carbon fiber Nose Cone that protects the Orion's docking-system/hatch and the parachutes' outlets (and is detached in the elliptical orbit) ...so, if the Orion's ascent "hot-air problem" really exists... they only need to EXTEND this light cover to the rest of the Orion sidewall to have the full protection you want... (a larger protection that will be detached in orbit with the nose cone)
and, since the Carbon fibers are very light and very resistant to high temperature (since used in F1 cars, military jets and on the hottest places of a Shuttles on the nose cone and part of the wings where the temperature reaches 1260°C on re-entry) the increase of mass of this extra-shield will be in the order of 200 kg. (so you can put that extra-protection fixed on the capsule or joined with the nose cone to detach both in orbit)
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Bob B's avatar shows the capsule in orbit with the upper shield already jettisoned. Notice the lack of a white dish on top of the capsule.Gemini was similar to Mercury and built with (similar) '60s technologies and materials but WITHOUT any BPC nor a tower-LAS ...the top cone was NOT a BPC but (simply) the parachutes' protection cover and was not jettisoned at high altitude like a LAS but on re-entry (look at the several Gemini images on the web or the Bob B. avatar...)
As for your other remarks, you keep on thinking and putting fingers in your ears to make sure nothing else comes in. That's a pitty.
Very thick fingers indeed. It's amazing how you completely ignore or even negate sources brought to you in this thread. Quite disrespectful too.
On top of that, your physics of thrust and aerodynamics are quite wrong (not to mention your lines of reasoning), but as you won't listen anyway I will refrain from correcting things again and again.
Have fun, and by all means do not read anything the relevant sources say will happen but, to use your words, "just imagine what may happen".
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no, this is the full-scale image of the Bob B. avatar:
never seen that "dish" (do you have a picture?) but, if Gemini had a dish, it's main purpose was to protect the rendezvous radar and other devices in the top cone:Notice the lack of a white dish on top of the capsule.
no, my latest TBS-Orion/new-LAS design ALREADY has a light Carbon nose-cone/protective-shield for the Orion's docking-system/hatch/parachutes-outlets:...ignore or even negate sources brought to you in this thread...
and (as said in my previous post) IF the REAL wind-tunnel tests and the REAL flights with REAL capsules will show that a thin thermal shield is necessary also without the tower-LAS abort motors, they can (simply) EXTEND the Carbon shiled to fit the sidewall ...the mass increase will be small and the full shield/nose cone will be (simply) detached while reaching the elliptical orbit... problem solved (if any)
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Sounds like a good idea.
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Orion is not an historical vehicle, but a spacecraft that needs 7+ years to born and fly, so (literally) EVERYTHING can still happen about its design, shape, materials, etc. (including something like a different LAS...)
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That's why I have the guy on 'ignore'.
I have no patience for those that stick their fingers in their ears.
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do you really say that nothing in my proposals, ideas, suggestions, discussions, opinions, articles, threads, posts, sources, images, etc. have something of interesting or useful? ...just because I don't like the tower-LAS?
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I don't think anyone said it was not interesting, they only think that they are not an advantage when you consider all the factors.
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despite I believe in my ideas and I support them (clearly) I can't "dictate" nothing to the peoples/agencies/companies that build real vehicles ...so, just look at my proposals as alternative "concepts" like those you can find to-day on the web or developed (but never built) in the early years of spaceflights (as shown on Astronautix)
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Are you making a point here? I'm not sure what you are trying to say.
Anyway, the simple fact that everyone here is discussing your proposals, and the technology behind your proposals, means that they looking at them and not just dismissing them for no reason. It is unfortunate (for you) that they are uncovering reasons.
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on websites, blogs and forums there are many different proposals about space (some really strange) so I do the same thing with my ideas ...of course, I'm aware that great part of the space-hardware will be built as planned years ago, but that doesn't mean I can't suggest my alternatives
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I like discussing proposals and analyzing alternatives. The problem with Gaetano however is that as soon as something critical is said he’ll aggressively defend his position even when it is indefensible. He is simply incapable of rationally discussing the pros and cons of a proposal and working together with others to incorporate alternative ideas and suggests into a better and more workable concept. Every one of his threads turns into a confrontation because he’d rather defend a demonstrably wrong idea because it is his rather than acknowledge that someone else’s idea may be the better alternative.
Because Gaetano will rarely budge from his original concept, these threads never have the opportunity to evolve into a legitimate discussion of alternatives. For example, maybe there is a viable alternative to the tower LAS but despite several pages of discussion we are no closer to it because we’ve gotten bogged down arguing over a single flawed concept because the creator refuses to listen to valid criticisms. I’d enjoy kicking around ideas with others to see if we could come up with an alternate design, but Gaetano doesn’t want that. He just wants to cram his ideas down our throats and isn’t interested in the ideas of others. Gaetano stymies creative thinking rather than encourages it.
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it's very difficult if a comment is destructive ...just two examples from your post #432:
a) you find a source with the weight of the Apollo-BPC ...just 318 kg. ...but you forget to deduce/admit that an underside-LAS with a FULL (boost+motors protection) BPC always has less mass than a tower-LAS
b) you find a March, 20, 1969 source about "Deletion of Apollo CSM boost protective cover rejected" but you forget to notice that it was rejected comparing two similar options (both with a tower-LES) and that (clearly) if the Apollo tower-LES abort motors ALWAYS remain atop the capsule, the BPC can't be deleted without an HEAVY and EXPENSIVE reinforcement of the "windows, EVA handholds, vent lines" and EVERYTHING may be exposed to the 1500°C motors' flames!
no ...despite I think/believe that a (properly made and not so "heavier") Orion will be able to resists to the boost forces without a BPC, in my post #435 I accept the option of a BPC-light (used only if real tests show that it is necessary) extending the nose cone protection to the Orion sidewall ...but (clearly) the newBPC can't be so heavy like a BPC built to resist the (much higher) abort motors' temperature!...refuses to listen to valid criticisms...
I'm not against your BPC... I just think it's unnecessary with a properly made Orion (without any big increase of mass) or (maybe) only a very light BPC can be added
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On a side note, most carbon fibers have rather poor heat resistance, due to the resins used. A typical aerospace grade carbon fiber will soften at above about 250f (120c), with many softening before that due to the temperature resistance of the epoxy resins. Some ultra high temperature epoxies and other resin types can take up to 650f (close to 350c), however cost goes up immensely when dealing with resins like this. To take more than that, one must go to a material like reinforced carbon-carbon, a PHENOMENALLY expensive choice, resulting in a cost into the many tens of thousands of dollars per pound (standard carbon fiber plate can be made for a cost of perhaps a hundred dollars a pound at most). Also, note that even reinforced carbon carbon is not capable of taking a full, lunar velocity reentry, so would not be the choice for heat shielding on the capsule anyways.
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it's only an example/suggestion of a light material (used on the Shuttle) but I'm sure that LM engineers may use a lighter and lower priced alloy for that purpose
in my TBS-Orion/new-LAS design the carbon-carbon parts will NEVER used for the re-entry thermal shied but ONLY for the Orion's Nose Cone and (if necessary) a light-BPC (both detached after Orion reached the elliptical orbit)...note that even reinforced carbon carbon is not capable of taking a full, lunar velocity reentry...
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Lower priced? Yes. Lighter? Almost assuredly not. RCC is an incredibly lightweight substance, especially considering its strength and heat resistance. It would be overkill for a nose shield.
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