I Was Wrong About How Much Wind Tunnels Cost...

several days ago I had the opportunity to tour the NASA as research facility with some amazing fellow creators hello on that tour two things stood out to me the arcjet complex where NASA test re-entry heat shield materials and their multiple enormous wind tunnels I wanted to make this video as an addendum to the last two where we talked about heat shield materials and wind tunnels so let's start with the heat shields if you want to know how well your heat shield works but you don't want to risk flight Hardware you need to recreate the heating and plasma flow seen on re-entry you can do this by moving your heat shield really really quickly relative to the air around it or you can do the opposite you can keep the heat shield still and force air past it really really fast the second option is obviously much easier and it's what the arcjet is all about in order to create Hypersonic air flows for prolonged periods we can't go the traditional wind tunnel route so enter the arcjet this is the most science fiction steampunk looking object I've ever seen and it's got a matching 60s era light green control room to match so how does this thing work well when you create enough of an electrical potential across two leads you get an arc an arc turns non-conductive material like air into a conductive medium like plasma plasma is conductive because of all the free electrons and charged particles in it which means that once the ark is established it's much easier to maintain the arc than it is to initiate it for this reason NASA starts the arcjet by injecting argon into the combustion chamber before pumping DC power into it because the breakdown voltage for Argon is lower than air if you blow air over that Arc the plasma it forms can strip off and help recreate some of the thermal environment on re-entry you can also use this plasma for surface treatment on composite bonds all the charged particles in it can bond with dirt and surface contamination turning into gas which increases surface energy and makes the bond much better hold on wait a minute we are down a rabbit hole again sorry there's a video coming soon about plasma surface treatment back to the arcjet the ark can reach up to 30,000 de F and I'm not going to give it to you in Celsius or kelvin you're smart you can figure it out this many zeros should tell you all you need to know this regardless of units is beyond the melting temperature of any material so it might shock you pun intended to learn that copper which melts at a 15th of that temperature is used to construct the chamber for the arcjet it's getting more complicated now so let's hop into on shape and take a look at the cross-section as an example the whole assembly is built using smaller cylindrical discs Each of which has cooling channels for water and some of which have channels to inject argon or air as well these discs are made of copper because it's such a good thermal conductor it's okay that copper melts at a lower temperature because NASA flows lots of water through these discs to Wick heat away from the chamber technically this thing is is kind of a regeneratively cooled rocket engine it has a combustion chamber where the arc forms and air is injected then further down it has a converging section throat and diverging section to accelerate the gas to Hypersonic speeds out of the chamber sounds like a rocket engine to me here's a clip of me not understanding that the arcjet gets four times hotter than the melting point of graphite um so we got three sting arms there one sting arm up above one sting arm here one here um just like you saw the video we put the test article on the end we articulate the AR in and then swing it into the flow flow is going that way we look we look down through there wow is it graphite it's all copper all copper and and it's just all water cooled by controlling the power and gas flow we can recreate the environment of re-entry on various heat shield materials the samples swing out on rotating arms called stings and are subjected to The Inferno of the arcjet before we dive into the test footage if you can believe it sometimes this isn't enough sometimes it needs to be hotter that's why adjacent to the arcjet chamber NASA AMS set up four 50 KW continuous wave infrared lasers to boost the heating on the test sample the beam comes out of this window then through a port to heat up the sample and check this out if you're someone who enjoys film making you'll probably recognize these this is a red weapon Dragon or possibly a red weapon helium camera that's used to film the samples as they oblate so let's take a look at some test footage 6 5 4 3 2 AR God okay we're at conditions setting up overhead overheads going in in 5 4 3 2 1 NASA as was very generous in providing these clips to us and the coolest part is that we can see the samples a blading their photo and video team is no joke because the brightest part of the plasma is correctly exposed so we can see all the behavior on the surface I don't know exactly what material this is but we can assume it's either pika pika X or some type of phenolic a blader if you remember from the last video one of the important parts of a folic a blader is forming a Char layer but when you have a high enough Mass flux like in a re-entry or arcjet scenario you can't form that Char layer which is weakly attached instead what the phenolic does is create a very thin gas layer on the surface which helps with insulation so I don't know exactly what this material is but I have a better idea of what the next one is I could be wrong but I think this one is Av coat which is the same type of material used on the Apollo heat shield from what I've read we don't really know how to make avat anymore and this is somewhat evident in the tests that they show in these videos where we have a burn through during the test but the way you can tell the difference and again I'm very much guessing here is the honeycomb structure instead of using a linen carbon fiberglass Etc substrate the phenolic resin was cured straight into a honeycomb structure for the Apollo heat shield this next one is super cool this is a mockup of a heat shield that NASA calls adept which is made of a material that's flexible called spider weave NASA claims it does just fine up to 3000° F and is great for Mars entry and the selling point of the Adept heat shield is that it's foldable foldable heat shields are kind of all the rage right now so it's cool to see one tested in a re-entry like environment as I understand it this material is not meant to a blate and is closer to a refractory heat shield like we talked about with Starship space shuttle X-37B Etc but of course because it's foldable these heat shields can't crack in the way that starship's tiles crack or the space shuttle heat shield fractured I don't want to go on too long about this but like man is it exciting to see all these developments in thermal Protection Systems the last one I want to look at is kind of goofy it's a meteorite not a heat shield one of our tour guides told me they bought this meteorite on eBay then it looks like they milled it down to the shape of a regular heat shield test article and they stuck it in the arcjet I think it's so cool the way you can see this melting meteorite recirculate in the low pressure Zone behind it and I'm saying the exact same thing as Scott Manley who as I'm editing this just posted a video about this same exact subject I'll toss a link to that in the description below I'll let him talk more about it and let's move on now one of the other facilities we visited is called the unitary plan wind tunnel named that way because it's actually three sections the power plant I.E what creates the wind is a single unit and then the test sections are split up into different sizes with different goals for each this likely also allows for customers to take their time setting up and tearing down models without putting the whole facility out of commission we very briefly talked about wind tunnels two videos ago and this seems like a great opportunity to dive a little bit deeper a common question and one that was asked on the tour is will cfd get good enough that we won't need wind tunnels the answer on the tour was a pretty resounding no and in my limited experience here I agree with that in my personal case cfd makes a lot more sense for the Rockets I build but when you're building passenger airliners capsules that carry crew fighter jets you can't afford to leave things to the simulation there are four major techniques used by as to evaluate the performance of a wind tunnel model Shadow graph infrared thermography pressure sensitive paint and oil flow though our tour guide did say oil flow is not used much anymore I'm trying very hard not to go down every single tangent but I didn't know about oil flow being used in Wind tunnels before and it's super interesting basically you cover the model in oil run it in the tunnel then you can see the steady state surface Dynamics after the fact I imagine this is used less given the development of pressure sensitive paint the section of the Wind Tunnel we visited was the 11t X 11t it's hard to convey the scale of this in video but I was told that they pretty much built the building around the wind tunnel rather than the wind tunnel inside the building entering the test section is surprisingly creepy there's no audio equivalent to this in the natural world and it's hard to convey what it's like to hear this infinite echo down both ends hello I think I spotted where you plug in all of your equipment as well this is a panel on the back of the assembly that holds up the wind tunnel models and you've got all these little ports for sensors and thermocouples and anything you can think of you can also tell that the roof opens up I didn't really think about this before but how do you get large models into this tunnel that's a closed system you just take off the roof and crane it in we also got a chance to see some of the behind the-scenes Hardware as well the scale on this assembly is equally massive and it made me think a little harder about cost a few videos ago I took a shot in the dark at the cost of running a wind tunnel and said conservatively it might be between $200 and $2,000 per hour to operate so how close was I do you have an estimate on the cost to run this per hour um we do so uh you know there are different rates like a NASA specific research one pays a different rate than a commercial one right and on the record I don't think I can say anything publicly uh you can talk to Marine about our rates if you if you wish to come to us um if I guess between like 200 and 2,000 per hour you're you're way off okay all right we continued through the data processing section of the Wind Tunnel as seen in this footage and later on as we walked through the facility our tour guide clarified a few things I wish I had footage of this but as we were chatting more about what the price might be he followed up with think of it this way pg& had to build a separate power substation to run as the scale of the Wind Tunnel at ases which is actually one of several wind tunnels there is kind of mind-blowing this test facility has so much history and it wasn't even built under NASA but its predecessor the NACA in the 1950s which by the way I was instructed several times by the folks at ases is not NAA nobody called it NAA it was the NAA and once it became NASA we started using the acronym as a word but the history between Apollo shuttle SLS Military and Commercial the number of programs tested at this facility are just incredible you can even find photos of the Mercury program test articles that are in the same arcjet complex used today we got to see so much more of the Ames Research Center than I'm covering here and I'm sure more of that will come out on a few other channels because basically everyone had their cameras out at some point there is so much more to NASA as a whole than I think most people realize the programs and research they do span such a wide range it's not just astronauts it's not just exploration it's not just earth science it's not just sounding Rockets it's not just orbital Rockets it's not just robotics it's not just Aeronautics it's not just astrophysics it's not just re-entry it's not just the Deep B Network it's not just any of those things it's all of them under one umbrella getting the chance to see the as Research Center was a nice reminder that this publicly funded entity does so much more for the world than we usually give it credit for or than we usually give it the budget for an enormous thank you to Scott Manley for getting us in touch with am and the research center itself for being willing to take the day off their normal work to show us around the facility I hope I'm able to go back soon and a big part of this working out was also open sauce which took place this year in San Francisco just a little bit north of as the event was incredible with so many interesting projects both rocketry and otherwise and I will absolutely be there next year this video is a simple one and it's a little different from what I normally make so I wanted to take this endsection and say thank you thank you for watching these videos for giving me advice in the comments Thanks for believing I could land a model rocket before it happened and now for believing that I can figure out how to get a rocket to space I've been making and posting videos since 2008 purely because I have enjoyed it and I'm so grateful that I get to do it as a job now it's a dream to be able to share these projects with so many people and it means the world to me that you choose to spend your time watching them I always kind of feel like one day this magic YouTube thing will stop working I'll wake up and everyone will have gotten bored and moved on I don't really know how true that is but while y'all are here and hanging out again thank you so much I'll be back with more project videos very soon and for now I hope you enjoyed something a little different my name is Joe Barnard may your skies be blue and your winds be low

Channel: BPS.space

Views: 116,202

Keywords: BPS

Id: BuB4MiboJU0

Length: 14min 12sec (852 seconds)

Published: Sun Jun 23 2024