Adam Savage's One Day Builds: NASA Retro-Reflector Replica!

hey everybody welcome to my cave I’m Adam Savage on Tested.com just calm and today’s one day build is a really cool device that I learned about while we were filming the Mythbusters NASA episode and it’s called a retro reflector a retro reflector well rather than just tell you about one I can show you one this is a retro reflecting prism and its features that make it a retro reflector are that it has three polished surfaces that are all at exactly 90 degrees to each other so in one sense you could say that the back of this retro reflector represents the corner of a cube right 90 90 and 90 why is that important well when you fire okay let’s say you’re firing a pellet gun at a 90 degree angle that pellet is going to come back at parallel to your original shot that’s a feature of a 90 degree angle no matter what angle it’s at it’s going to the math is gonna add up that the pellet comes back parallel that also means that when you shine a light into the corner of two mirrors it comes right back to the source you might have noticed this in hotel bathrooms which is where they often have mirrors that meet in corners that you can always see your face in the corner if you’ve noticed that you’ve noticed what is the rudiment and the main operating principle of a retroreflector the fact is is that you were looking at two 90-degree surfaces if you added a third your eyes would always be seeing your face your eyes right in that corner and it’s really neat um we use retroreflectors every single day a bicycle reflector is essentially if you take one and look at it close up you’ll notice it is made up of lots of little corners like this lined up in a row and nASA has built a several different retro electors that they have left on the moon for the purposes of scientific investigation in fact on one of the moon landing on the moon landing episode that we shot for Mythbusters we went down to to an observatory whose job was to fire a laser at the moon every single night at the retroreflector that was on the moon now the amount of spread you get even from a highly columnar laser from earth by the time it’s traveled the half a million miles to the moon and back total right it’s tuned in fifty miles to 50,000 miles each way about half a million miles to come back by the time it gets to the moon the spread is gargantuan no matter how columnar you try and make it and by the time it comes back you’re literally firing like quadrillions of photons at the moon and you’re getting 30 or 40 back but those 30 or 40 tell a tale they tell you exactly how far away the moon is they tell you they allow them to actually quantize and make even more precise confirmations of theory of relativity and when we discovered that a retroreflector was something they’d left on the moon I wanted to build one I built one for Mythbusters I built a flat array retroreflector but there’s another kind I found recently that uses retroreflecting prisms and nASA has used several of these as well and I want to make well here’s a picture of one of NASA’s retroreflectors this is what I want to make today and I have assembled the parts to do it it’s a fairly simple and straightforward build of course I’m gonna make it slightly more complex but I’m going to begin by gathering my parts shall we start first up is the dome that is going to be my dome second up the prisms I bought these on Amazon are some drills for making holes template I’m going to piece of paper for making a template I think first up this is going to be the color and this will sit on top of that color I kind of think I want to I got to mark this up and then I got to cut it to match that yeah and then I’ve got to drill the holes I shouldn’t mount them together until I’ve done that but that’s the first part is mmm-hmm this is tricky no I think I do want right now this is a somewhat flimsy piece of metal and I’m nervous about drilling these big holes through it first up is I got to do a bunch of layout that’s the photos I got to make

some lines on this and make some cut lines and figure out exactly how big this retroreflector actually is and I did some tests on another half of this oh yeah this is actually a circular cake mold so I bought two halves of an aluminum sphere of a six inch aluminum sphere fairly cheap it’s totally awesome I did some testing on another one so I’m going to use that to kind of get my bearings here a good drafting compass is so important I’m gonna make a series of some small lines in case I was not quite perfect about my measuring and this is just to make sure I’ve centered my my ball see here yeah it’s not quite perfectly round but it is round enough okay so now I want to make a XY and I want to find the top dead center of this bad boy you know I wish I had a large angle angle plate which I don’t have in my collection and I purchased one recently it’s on its way but it hasn’t arrived yet that would allow me to mount this this way and do it Oh actually Oh ah I got it right awesome I need a large flat thing that’s its parallel delimited plate and that would be my stone this is a machinist stone for doing layout work that’s great I gotta get some shims here’s how we’re gonna do this here’s no gonna find the top dead center of this thing push it down here alright and that is yep that’s the distance great so that distance is precisely that distance is precisely six point three inches great so 3.15 inches is the exact height that I’m looking for because I will set this height gauge at 3.15 inches that’s three point one five right great I’m gonna lock the top on just the bottom a height gauge is a great thing to have in your collection and you’re about to see why what you heard me doing was taking a piece of plywood and drilling a hole in its center I will now use this piece of plywood to hold on to this guy and leave the center so I should be able to clamp this these two clamp this is one of the things that makes it hard to work alone the third pair of hands be really helpful about now I don’t have a third pair of hands so just gonna have to make do no you stay there and you go here ladies and gentlemen okay so as long as this is touching the bottom I know that’s it that’s it great yes there we go bring in the height gauge and I’m just gonna because I just moved it I’m gonna check its measurement one more time and I like it it is accurate so here comes and I am just going to scribe sew the edge of a height gauge it’s very sharp and piece of steel and I’m going to scribe part of my X and then now I’m gonna loosen this just a little bit and I’m gonna turn this roughly 90 doesn’t have to be exactly 90 and we’re roughly 90 I bring in the edge of the height gauge and I simply scribe across now that should be Center and if I want to make sure that it’s Center I simply turn this again and if I turn it again

I should it should still cross Center when I scribe it just make sure double check and that is crossing within 20,000 er that is good enough for me so having properly scribed it I can put all this stuff away and I can start to mark up and I yes I can I can start to mark up my mic down so now I’ll put it back on my template and I’m going to make four cardinal marks I’ll clean these off later but for right now one two and I know these are perpendicular to each other because I measured them carefully and now all I need to do is carry that mark up and over here to its brethren and it would be great if I had a great way of mounting this then I could use the height gauge to do that but I don’t so what I’m gonna need to do is get a piece of flexible plastic and hold it on there it’s hard to know that you’re drawing a perfectly straight line on a curve from two points because you could rip tauf in the middle of those two points however because I have three points top bottom and centre I actually have the ability I actually have the ability to cross all three points and make sure that I am growing yeah yep and great that’s good that’s good so we’ll just draw come stop and then we’ll do another one after that all the way to all the way to that that kind of work ah great cool so I’m gonna start with a three quarter inch circle in the center and that’s gonna provide me my correct distances these circle templates have cardinal markings on them one and these little markings here 1 2 3 4 so I line those up with these and then I know that I’m drawing that circle on center I could also use the compass to do that and I actually will for some of the placement of the others oh the prisms the prisms that I’m using are one-inch retro reflective prisms and you can buy them in a batch of 10 there they are and I need I need them placed around and the arrangement exactly like the NASA one and I only need eight of them so I’ve got two sacrificial ones so here we go and I need those other remarks because you need to hit this on center great another one there are even more careful ways to do this kind of layout but since this is a sort of a sort of a prop I am I’m going a little fast and loose so now it’s incumbent on me to add another circle right here and I want that circle to be I want that circle in these two circles to draw an equilateral triangle and what that means is you need to know the center of this triangle in the center of this triangle and that is actually a knowable thing right so if I have an equilateral triangle and I know that that’s one of its sides I draw an arc of that length from the middle of one circle and actually I’ll do it across both sides because when I draw it from the center of its adjacent circle the points at which they cross describe the center of the third circle okay so now I

am simply going to set my compass to draw a 1-inch circle a third circle look at that there you have it okay so there you have all eight of the circles one two three four five six seven eight now I need to cut this off kind of about there the question is how to do that okay I’ve figured out how to match the outer cut of this so that it is the same external radius as this pipe here and what I’ve done is I’ve managed to put the dome down on the pipe so it’s totally flat so when I spin it it shows the same level with my height there we go so when I spin it it shows the same level with my height gauge then I only need to know the distance right so basically I put this totally level on top of the pipe and put it in there little pressure and checked it with the height gauge and it’s within a few foul all the way around so now all I need to know is the difference between is the distance actually here right there what is that distance and that distance is one point six five so now I use this to set the height gauge to one point six five inches good that is one point six five inches and then here’s what we do we simply oh this is a cool NASA proper making today everybody this line represents my cut line around this now how to cut it it’s a super thin material this is oh oh three oh it’s not going to like me cutting it I mean I could almost cut it with some airs nibbler and air nibbler that’s exactly how to do it but first I need to drill the holes that’s the most important Florence so you don’t use a normal drill bit to drill holes in super thin sheet material like this to do so would be folly and I’ll explain why I need a one-inch hole in this thirty thousands thick material this is a one inch drill bit so how does the drill bit walk well the drill bits front end I know I’ve beaten the crap out of the stro but I apologize the front end of this drill bit is a pair of chisels they are at about a 30-degree angle and they’re traveling around and there it is a little draft angle this chisel is peeling up material so it’s two chisels opposing each other turn tearing through material and then the spiral flutes carry that material up if you attempted to use this drill bit on this stuff it would dented the moment it broke through it would pull it in it was just be a horror show that’s why we use a thing called a unit and that is these these are some of the most important things you could have in your shop instead of pulling the drill bit into the material what this is is a side chisel that scrapes the material out with a very low draft angle at each level so each one of these little steps is a different sized hole you can drill and since I need a 1-inch hole and that’s on this big bad boy I’m actually going to creep up on that hole I am NOT going to try and drill it all at once because that way lies madness as a maker you learn early that you’ve got to incremental eyes that stuff I’m also going to use my smallest cordless so I have some sensitivity to the materials and I’m gonna start by drilling eight half inch holes in this piece that right there is a engineering miracle to me that that works there you have your eight holes for the primary prism shape it’s time to move on

to the bigger bit there is a really cool feature to these bits and that see how this hole is not perfectly centered in the line that is slightly problematic however I have just got over the Unova if I push slightly in that direction as it’s cutting I can bring into concentricity and each step provides me a little bit of an extra office now if you take a look you’ll see it’s far more centered in the hole and that’s because I can actually move I can move this bit while I am using it that is totally amazing to me those are eight 7/8 inch holes we’re going along gangbusters now it’s time to take each hole to its next what’s next diameter which is one inch and for this I want to be very very careful all right we are halfway there we have four of the four of the pieces cut and four of the holes cut and we’re gonna continue on the more the more I cut into this the more delicate it gets and the more dangerous my cuts get and so I have to be very very very careful on that front so just to be clear I’m like applying a clamping force on this but mostly below the line of the holes because I don’t want to crush it here I’m also trying to hold this really rigid and allow it to do it that works but I’m too scared of doing that for every cut because uh if it grabs and grabs really fast then I’m really bummed so now I have my holes cut I am gonna do a little bit of a little bit of cleaning up all right that’s pretty well cleaned up now the question is does my prison fit in each one let’s just try yes yes yes yes yes yes and yes great presume successful okay so now I want to cut it on this line this is what I think I’m gonna use to cut through to cut this line around here to meet up with this guy and it’s called an air nibbler we’re gonna do a testament on the other half of this globe the nibbler has this little tiny this little tiny notch up here you can’t see it’s moving too fast for the camera this little piston moves up and down so it’s basically you feed something in there like this and watch this it nibbles like that now I’m gonna have to practice with that without looking at the camera so I can see if I can get this right all right left side whoo all right that is a rough cut out this part ways grams at this point it is really really flimsy the next step is to clean this edge up on the sander I have my part cut out it’s not beautiful it’s gonna need a little more

beautifying and I think I’ve cut it slightly oversized for the piece but now I need to lay off the little half-inch thick section of the pipe so that I can come down here and be that part well I’m a little bit of a jerk and I cut this piece without filming it I totally forgot I forgot that I was filming I’m so sorry I cut a ring off that four and a half inch pipe I actually beveled the edge here to get a nice marrying surface I matched the angle and you can see we’re very close to our retroreflector right now I just need to trim off a bit more the question is yeah I’m going to trim off some more I gotta get a fair bit out of here actually okay with a little more work on the scotch brite wheel I’ve gotten it very close here’s what I’m gonna do though that’s very close but I wanna what a nice edge on that so I’m gonna glue it with some epoxy I’m gonna let it set and then I am going to do the last bit of the polish before putting in the lenses that should take me about 40 minutes really important when you’re gluing with epoxy not to just glue smooth surface to smooth surface you want to add some tooth to your bill I can’t believe I mixed two minute epoxy and now you’re watching me rush through this step but hey we are all flawed vessels why shouldn’t I show you huh these aren’t how-to videos these are more like what the hell happened videos great we’re still a little soft that’s awesome there’s probably some chemical engineers out there who know exactly what brand or what type of thermoset I’m using because I’ve reported that it smells like skunk or maybe they’ve put a skunk smell in it so that you’re sensitive to the files and what they’re gonna do to you alright so I’m gonna pop this in there great that’s awesome fabulous or centered now wait delightful very pleased excelsior yeah we were let’s see we have a few minutes oh I pulled off too much weight on one side and I thought I had unset the whole thing but luckily I have not it seems to be fairly stable alright I am gonna take this to the sander and start to clean it up cleaned up the edge on my belt sander you can see got a nice finish there I started with a coarse grit belton into a fine grit belt and they did some scotch brite on this it’s time to attach the mirrors I know I know there are four holes here here here and here but I am not comfortable installing those just yet that’ll it’s gonna be a later addition to this so to finish this we’re just putting in the mirrors in order to put in the prisms I don’t wanna get my fingerprints on them so I am going to put on some rubber gloves three six seven eight I’m gonna use a rings for my frame around II yeah I’m making them flush to the top and then I’m gonna pop them right in there and I am going to use a spot of the hot glue gracious I’m gonna use a spot of the hot glue in

order oh you weren’t on the thing about a retroreflector that makes it so useful is that it always reflects back to its point source which means it’s fantastic for range finding between two objects and I haven’t read too deeply into the use of retroreflectors and space with NASA but I would wager that when you’re trying to dock to differ vehicles in space and thus delta-v their relative speeds are and distance are really really vital the retroreflectors may play a key role in them understanding exactly where they are in relation to each other for me it’s just gonna be a cool thing well it’s really nice to be able to handle something without getting it greasy oh it’s starting to look pretty yeah see that look at that that’s starting to look like a professional thing mm-hmm this is so cool hey so let’s start okay for outside ones are glued in I don’t want any tendrils no tendrils on my glass damn it get off there if I have any tendrils they will show from the front and I can’t deal I don’t want that I want them to be there you have it this is my beautiful model replica of a NASA retro reflector shine light at it you will see it reflect right back to that light we will include some links to all of these pieces and parts and bits and bobs so you can order them yourself and maybe make one of these for your own collection thank you guys for joining me this has been a really fun super fast one day build thanks for joining me I will see you next time thanks for watching a hundred percent of whatever you just watched that’s awesome we get to add that to our completion rate you deserve something you deserve a t-shirt for all your hard work follow the link below buy yourself a tested official t-shirt