NASA Edge | Game-Changing Entry, Descent & Landing Part 2
NASA EDGE completes its look into the latest Entry, Descent and Landing technologies being developed at NASA. Chris Giersch is back in studio with Steve Gaddis (Game Changing Development Program Manager) and Michelle Munk (EDL Principal Technologist) to talk more EDL concepts and technology. Blair and Franklin provide interviews with Paul Wercinski (ADEPT), Jay Felman (3D-MAT) and Mairead Stackpoole (HEEET) in this second part of two episodes focusing on EDL.
Game Changing Entry, Descent and Landing Part 2
CHRIS: Welcome to NASA EDGE, an inside and outside look at all things NASA. How are you doing Michelle and Steve?
CHRIS: You’re back for part two of EDL. In part one we talked about some cool technologies from Entry System Modeling, to MEDLI-2 and HIAD-2.
CHRIS: And Steve, we’re going through at your second half of the portfolio. What are we going to talk about today?
STEVE: We’re going to talk about ADEPT, we’re going through about 3D-MAT and we’re going to talk about HEEET.
CHRIS: Awesome. And so, just kind of recap for those who folks didn’t see part 1, real quick, what’s EDL.
MICHELLE: Entry, Descent and Landing, it’s how we get a spacecraft from the top of an atmosphere to safely on the ground. So no matter what planet it is, we can do EDL.
CHRIS: I’ll tell you what, when we looked at the technology in part 1, we kind of said that EDL is not easy. It’s very hard, isn’t it?
CHRIS: And when NASA’s been working on EDL for a long, long time. And so I guess, as we – you know one of the things we didn’t talk about in part 1 was this journey to Mars. We eventually want to send humans to Mars.
CHRIS: I mean EDL is going to be one of the most important aspects of getting there, isn’t it?
MICHELLE: Yes it is.
MICHELLE: One of the two biggest challenges that have been identified through our national academy’s reviews.
CHRIS: Well, what’s the second one that we’re going to be –?
MICHELLE: Radiation protection of the crew.
CHRIS: Oh wow! Would you want to be on there?
STEVE: Yeah, I want –
CHRIS: Would you?
STEVE: Sign me up today.
MICHELLE: I’ll sign you up.
CHRIS: Now, in getting back to Entry, Descent, and Landing, we’re going to be looking at a different concept from HIAD-2 from the previous show. This one is called ADEPT.
CHRIS: And I’m sorry but I don’t have it memorized. So, I have to read on my paper. It’s the adaptable, deployable entry placement technology.
CHRIS: What is that about?
MICHELLE: It’s way to get a spacecraft where you wanted on the surface of a planet.
MICHELLE: So, it’s similar to HIAD in that it’s a way to expand a heat shield after you get to your destination but it’s all folded up in the rocket when you launch and this is especially useful at Mars where we need lots of drag area because we have a very thin atmosphere but the cool thing about ADEPT is that it has very high temperature capability. So, we can use it at more demanding destinations like Venus or Uranus.
CHRIS: Blair had a chance to sit down with the TPS engineer, Paul Wercinski at NASA Ames to learn more about ADEPT technology.
BLAIR: So Paul, tell us what is ADEPT?
PAUL: ADEPT is a new architecture for performing entry at planet surfaces. It’s breaking the paradigm of the rigid arrow shell that it had been used in the past exclusively for missions to other planets.
BLAIR: So, explain how it’s physically different?
PAUL: The easiest way to describe it to someone is, think of an umbrella, it achieves the deployed area that you need for decelerating at a planet but overcoming the limitation of the launch vehicle that you have to fit in when you’re leaving earth, the shroud puts a restriction on how big you can make you arrow shell. So, it turns out the best way to overcome that is once you leave the launch vehicle is to be able to open up to something bigger and that’s what we’re doing with this umbrella.
BLAIR: Well, imagine with something like that and all the extreme conditions that you faced on reentry, you have to have to some pretty strong material for this umbrella.
PAUL: Yeah, and that’s been sort of the major recent breakthrough in enabling this technology, is this carbon fabric. It utilizes practically pure carbon yarns that are woven three-dimensionally to give you a very durable surface, multiple layers that are intricately locked together and because it is carbon, carbon is a wonderful material for high-temperature applications. It is almost practically optimized for that. So, carbon is a great material, you just have to be able to now get around each challenges of what to do with the material that gets extremely got which is what we’re dealing with.
BLAIR: And how do you make sure that in the stress of reentry that your shield, if you will, remains deployed?
PAUL: We attacked that numerous ways. We do a lot of design and fabrication of prototypes to build and show that the skeleton, the underlying structure, actually functions to hold it open under the loads that we experience. That’s the mechanical portion of it. The other part is the thermal portion and that is where we look through facilities like the arcjets, to subject the carbon fabric and the underlying structure to the high-temperature environments we expect to see on planet entry. It turns out though that, especially in the case of a deployable like ADEPT, you can do ground-based testing but ultimately, it will come down to a flight testing, and the flight test will then demonstrate sort of your end-to-end functionality, all the way surviving your launch environments, out in the vacuum of space deploying, holding that shape and then subsequently, entering, in our case, for flight test would be Earth’s atmosphere. Now, one of the lessons that we’ve learned with soft goods or the fabrics, is you have to be very sensitive to the scalability. So, certain things may work at a meter or two scale work great, then you have to be careful and do the same properties and characteristic holds as you go five or ten times larger. The bottom line is you have to literally build it to actually know that it’s going to work.
BLAIR: What are some of the big challenges you faced from a design standpoint and getting this system to work on either side scale?
PAUL: There are a lot of challenges. Let’s make no mistake about it. We are at the cutting edge of a new technology. It has amazing promise. We’ve tested the fabric at a small scale in heating environments well beyond what we would expect to see at Mars but that’s at a small scale. The biggest challenge that I see are, just the payload that is carried along behind us is going to be exposed to environments that you maybe don’t typically see for a traditional entry vehicle that has a rigid heat shield and a rigid back shelf. And so that is going to be a challenge and that’s going to have to be done with analysis and test to convince ourselves that the ADEPT technology, this new entry system can, not only deliver a payload but protect it so that that payload is still use when it gets to its destination.
CHRIS: Steve, one of the trends I’m seeing in all these pieces is scalability.
CHRIS: You have HIAD-2, have ADEPT which are two completely different types of EDL systems. I remember HIAD-2 was the inflatable. ADEPT is more, Paul is saying, deploys like an umbrella.
CHRIS: It’s more of a mechanical underneath. You’re testing all types of technologies…
STEVE: We are.
CHRIS: That’s why your job is a game changing.
STEVE: Yeah. And so, I think to help explain those, if you were to think about two different architectures, you think about maybe a jeep car versus a sports car, right. They’re both cars but they’re designed for different things. So for HIAD, it’s inflatable, right? So, it’s a little softer. ADEPT is more rigid body deploys structure. Its TPS has a higher, can handle higher hear rate and HIAD can handle a little bit lower but they both have their applications.
CHRIS: Because there’s not going to be one technology that fits every single mission.
CHRIS: And depending on where you’re going.
MICHELLE: Right, for human Mars, for instance, that architecture trade is still being conducted and so depending on the assumptions that you make on the size of the payloads and how we’re actually going to get the humans there and all the things they need to support them, the different systems have different strengths and weaknesses depending on those assumptions. So, we’ve actually connected those EDL experts directly with the folks who are figuring out what we need to take to Mars so that they can work hand in hand on designing the best system.
CHRIS: Now, one of the things that I want to focus in now in the show is that in the past couple of systems, they were big systems with HIAD-2 and even MEDLI with this heat shield. I want to focus in now on the materials because materials are very important and what you decide in terms of can they take the amount of heat in the atmosphere, right?
CHRIS: And one of the technologies that in your portfolio, it’s called 3D-MAT.
STEVE: That’s correct.
CHRIS: And that stands for Three-Dimensional Multi-Functional Ablative Thermal Protection System. That’s a mouthful.
STEVE: It is but it’s an awesome technology.
CHRIS: Franklin had a chance to sit down with Jay Feldman who actually is a project leader for 3D-MAT. So, let’s learn all about that technology.
FRANKLIN: So Jay, 3D-MAT, tell us a little bit about 3D-MAT and why it’s a Game Changing Technology?
JAY: Well, 3D-MAT is going to be the compression pad for Orion, and the EM1 mission and all the subsequent missions and 3D-MAT is the material that we’ve invented and it serves as a compression pad on the Orion crew module. I can show you, this is the crew module. It contains the astronauts. They’re inside there and it’s actually mounted to the service module through the heat shield, that’s this bottom part that gets really hot when the vehicle runs through the atmosphere.
FRANNKLIN: When those points where it connects, where the compression pads are located, right?
JAY: That’s exactly right. Those are called the compression pads. Those points are structural. Now, they’re the only part of the heat shield that are structural, so it has to serve as heat shield, withstand the heat, keep the inside cool, the astronauts cool inside, but it also has a structural job before it becomes the heat shield.
FRANNKLIN: Explain to me the 3D, the 3D-MAT.
JAY: So, this is a small piece of 3D-MAT here and what you’ll notice about it is that we have fibers that run not just in the X and Y direction like a cloth but there’s actually fibers running in the Z direction. So instead of stacking layers of cloth like a 2D material, we actually have fibers running in all three directions and we’ve build a single woven pre-form, we call it that has the dimensions that we need. This makes it very structurally robust and if you look at this, all of the fibers are very straight. We call that 3D orthogonal lead, that lends itself to being structurally robust. For the EFT-1 flight, the first flight test, that compression pad just had a 2D cloth, the X from Y direction for the fibers and that was – it’s shortcoming structurally. So, 3D weaving is not brand new. It’s been around and it’s evolving and we’ve pushed the technology to its limits in 3D-MAT but it is used in other applications as well.
FRANNKLIN: But there’s also resin in that.
FRANNKLIN: How does that all work together?
JAY: Very good question. We start with weaving. So, the yarn is commercially available. It’s a quartz yarn woven with our weaving partner Bally Ribbon Mills and to what we called a woven pre-form. It’s quartz woven pre-form. Now, we take that and we put it inside a resin infusion vessel and we’re using a process called resin transfer molding and we essentially push the resin inside all of the pore spaces between the fibers and fill and try to get 100% of that space to be filled with the resin and, again, that makes it strong and robust.
FRANNKLIN: I notice that there’s actually a giant metal ball that goes right through the middle of the compression pad. How does that work with conducting heat?
JAY: So, the bolt is there to hold the two modules together. It’s an explosive bolt so that when the crew module no longer needs a service module, the bolt actually explodes and the two modules separate and then the Orion module can enter the earth’s atmosphere. The bolt does add some metal and it adds some thermal conductance to the system and that is something we have to deal with but in the first flight test, above and beyond the bolt, we have to put a lot more metal in the compression pad to handle those structural loads and that amount of metal was really too much for these future missions like Exploration Mission 1 where we’re going a lot farther away or coming back faster, the heat shield is getting a lot hotter.
FRANNKLIN: So Jay, what is the size of a compression pad?
JAY: Ah, it just so happens I have a three-quarter-scale compression pad right here. This is the new material, 3D-MAT. It can fill the way to that.
JAY: Yeah, it’s very dense, very heavy stuff.
FRANNKLIN: It’s like a dumbbell.
JAY: Yeah. It’s very heavy, very dense. It’s about 11 inches in diameter and then you can see the hole, that’s the representative of hole where the bolt will go through.
FRANNKLIN: That’s a big bolt.
JAY: It is a big bolt. We only have four of them to hold the entire crew module to the service module so there’s a lot of load going through that.
FRANNKLIN: What kind of heat stress are we going to talk about on this compression pads when this crew module returns to Earth from Mars?
JAY: So in my field, we talk about heat flexes and I want to give you some reference points. Everyone is familiar with the Space Shuttle. When the Space Shuttle used to reenter the Earth’s atmosphere from lower Earth orbit, the amount of heat generated was on the order of, let’s say 50 watts per square centimeter. That’s our heat flux. This is going to see 500, 700 watts per square centimeter. So, it’s a significant amount of heating.
FRANNKLIN: Are there any other uses for 3D-MAT other than usage on the crew module?
JAY: There are other potential applications. As a matter of fact, we designed it specifically for the compression pad area. It’s now being used in other parts of the vehicle on the back shell where we have some both heating requirements and structural requirement, so it’s already finding other uses on Orion other than its original designed one. And we have had conversations with other folks both on commercial space side, as well as the Department of Defense who are very interested in this material. There are other potential applications.
CHRIS: This 3D-MAT material is pretty incredible but how true is it a game changer? I mean I know they’re using it for the Orion EFT-1 compression pads but how is the material itself a game changer?
STEVE: It was a game changer from the get-go, originally thought about and designed by Ames and their CIF’s, Center Innovation Fund. They saw a promise back then and they took it to an SBIR to kind of mature the technology a little bit more.
CHRIS: That small business?
STEVE: Small Business Innovate Research.
STEVE: Yeah. And I think it was with Bally Ribbon Mills. That’s who the industrial partner is. And then from there, it got picked up for Game Changing because it was early stage like a TRL-3. Well before we could even advance it, we got approached by Orion saying, “Hey, you know our simulations and models are telling us that our compression pads are not going to hold up under the heat load but we hear that you have a material,” and so they started working with us from that point forward to get it to a TRL 5-4 and now, it’s the baseline design.
CHRIS: That’s incredible.
MICHELLE: That’s a really great infusion story.
CHRIS: So, the idea is you’ve taken this woven material, like you said, with the woven TPS.
STEVE: It’s a woven thermal protection system.
CHRIS: The 3D orthogonal design.
CHRIS: And I mean you know it’s heavy like Jay was saying but still it’s a great material to use for EDL entry.
MICHELLE: Right. So, the 3D woven capability that comes from the textile industry on Earth is really applied to several of our technologies. So, the ADEPT fabric that covers the umbrella is just a 12-layer carbon fabric that’s 3D woven. The 3D-MAT that we saw is quartz fiber and what makes it really heavy is not only that it’s densely woven but then it’s infused with resin.
MICHELLE: And then, we’ll see I think next, in HEEET technology, they also use 3D weaving and they do it in multiple layers with multiple types of fiber. So, it’s very tailorable.
CHRIS: tell you what, I mean she’s proactive because she knows what we’re going to be talking about next, HEEET.
CHRIS: H – triple E – T.
CHRIS: And that stands for Heat Shield for Extreme Entry Environment Technology.
CHRIS: It’s pretty cool.
CHRIS: And so Franklin had a chance to sit down with the TPS Manufacturer Lead for HEEET which is Mairead Stackpoole. And we’re going to learn more about that cool technology. Let’s check it out.
FRANKLIN: So Mairead, tell me about HEEET and why it’s a Game Changing Technology?
MAIREAD: Well HEEET is a thermal protection material development project. It’s stands for Heat Shield for Extreme Entry Environment Technology and that’s we saw a need for a new thermal protection or TPS material. I think NASA has a lot of materials in the lower-density range that don’t do well in very extreme environments and it also has some materials that are very heavy that do well for extreme environment. So, we saw a technology gap and the HEEET project fills that gap. It’s a 3D woven system. I brought some samples along with me just to show you. So here, we have an example of the HEEET weave. It’s a dual-layer weave. So, the outer side, the side that sees the heat, we’ve got a very robust 3D woven carbon. Then we transition to a better insulator. So, this helps to keep the heat away from your payload or whatever is of interest you’re trying to protect.
FRANKLIN: So, where is this HEEET material? Where is it on spacecraft?
MAIREAD: This 3D technology covers all of the actual heat shield itself. So, this would be your for body, as we called it, thermal protection material. For the HEEET project, we have a tiled configuration that we’re currently working to demonstrate. This is segmented each of those tiles you’re looking at, is a single piece, 3D woven HEEET tile that’s attached on and bonded on.
FRANKLIN: So, why would NASA make just a one-piece heat shield? Why is it tiled?
MAIREAD: Well if we have a wide enough weave, we could actually accomplish that. We’re currently making a one-meter max diameter engineering test unit for the HEEET project. You can imagine as you scale up to a much larger vehicles that would be more challenging. So, you’ll always need gap filler.
FRANKLIN: So when you say gap filler, what material was used to fill the gaps?
MAIREAD: So as I mentioned, the acreage material is a 3D weave. The gap filler is also that same 3D weave. It’s just softened. So, it’s a more compliant version. So in terms of composition, the gap filler and the tile themselves are the same.
FRANKLIN: Now, when I think of NASA missions, NASA has sent Landers and Spacecraft to other planet and they didn’t have any problems, what type of missions are we going to use HEEET on that we haven’t used it for in the past?
MAIREAD: If you look at other missions and look at the entry conditions that those TPS materials saw. They were a lot of more benign compared to the missions that HEEET is targeting. We recently just completed some arcjet testing here at Ames and we were at 7,000 watts per centimeter squared. The environments are lot more aggressive. So, we’re targeting Venus and Saturn missions currently.
FRANKLIN: Can you talk a little bit about the resin infusion process used to manufacture this material?
MAIREAD: Manufacturer this material? Definitely. So as I mentioned, we’re starting with a 3D weave. These weaves are delivered in flat planks. The woven material itself is quite formable. So, I can actually take this material and change its shape. We are able to design tooling and have this weave formed in that tooling to the tile shape that we want. So, it’s a near net-shape process.
FRANKLIN: So for instance, like the cap to the heat shield, what kind of tooling would be used to make that?
MAIREAD: Right. So, we start with a flat plank and we have metallic tooling that we can then take our flat woven piece, format into the nose-cap shape. It is locked in the tooling as it goes through the infusion process. The infusion adds the resin and that resin we have a proprietary approach where we’re able to add a low-density resin. It’s more like foam rather than a fully dense resin phase. Once the resin is in place, it’s now a rigid TPS material.
CHRIS: I’ll tell you what; this HEEET material is really cool. If it’s that good, do you possibly see using this material on all EDL systems down the road?
MICHELLE: It could be tailored to multiple vehicles like Orion coming back from the vicinity of the moon. In the future, we could do an upgrade human mission to Mars. If we use some sort of rigid vehicle that was long and slender, it could be applied to that as well.
CHRIS: I guess it boils down to and we talked about this several times, EDL is tough. It’s not easy.
STEVE: Absolutely, right.
CHRIS: You’ve got all these technologies in your portfolio that you’re testing. At some point, I’m assuming in the not too far in future, you’re going to have to start looking at which technologies are the best, let’s say when we first send humans to Mars.
STEVE: That’s correct. And what we’re finding out is that these different technologies, some of them are better applied to the different planets that we go to and their environments and attributes.
CHRIS: So, that’s not really one size fits all in this particular situation.
STEVE: I don’t think so.
MICHELLE: The environments are so different that we really tailor the systems.
CHRIS: Where do you see this technology – we’re looking humans to Mars in a 2030 timeframe. We have to really mature and test that technology before that 2030 timeframe, aren’t we?
STEVE: Oh, yeah. You’re getting her spun up!
CHRIS: Well, she’s the one that pass Blair’s initial MEDLI investigation. So, she’s experienced in it.
MICHELLE: That’s right.
CHRIS: Maybe the bottom line is people want to know we’re going to Mars one day.
CHRIS: The public thinks it’s cool but we want the humans to land safely on the surface.
CHRIS: So, the idea – and EDL is going to have to be there. If you don’t have an EDL system, it’s game over.
STEVE: Without EDL, we’re not going anywhere else and landing on another planetary body.
CHRIS: I’ll tell you what, this has been an exciting for the past two shows, to learn all about EDL from Entry Systems Modeling, MEDLI-2, HIAD-2, ADEPT today and some cool material with 3D-MAT and HEEET. So, you’ve got a tough task ahead of you.
MICHELLE: We have a lot of work to do.
CHRIS: Being the principal technology for EDL and you have all these technologies to work on and mature them to the next level.
STEVE: It’s exciting.
CHRIS: Thank you, guys, for coming here today. It’s been fascinating.
STEVE: Thank you.
MICHELLE: Thank you.
CHRIS: You’re watching NASA EDGE, an inside and outside look at all things NASA.
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