Technology Demonstration Missions (TDM)
- Todd Ely
- Nathan Barnes
- Ian Clark
NARRATOR: Technology Demonstration Missions; taking the next step in deep space navigation, spacecraft propulsion and deceleration. Can a giant inner tube slow spacecraft for safe atmospheric entry? Will solar sails propel satellites through space? Check your space watch, it’s time to figure out how it all works on NASA EDGE!
CHRIS: Welcome to NASA EDGE.
FRANKLIN: Hey, I was looking forward to this new look but it’s not what I expected.
CHRIS: It’s kind of rough, isn’t it?
FRANKLIN: Yeah, it’s kind of rough around the edges.
CHRIS: What do you think?
BLAIR: Uh, you know, it’s intimate. It’s nice. It’s close quarters. I kind of like it. I don’t have any problems with it. I think it’s gold.
CHRIS: What are you talking about?
BLAIR: The show. The new look, this whole set up, it’s awesome.
CHRIS: No, we meant your beard.
FRANKLIN: That’s what we’re talking about.
CHRIS: That’s what we were talking about.
BLAIR: Oh. No, no, it looks rough but it’s actually smooth.
CHRIS: You’re talking about the studio? Oh.
BLAIR: I’m talking about the whole motif we have going here for our interaction during the show.
CHRIS: This looks pretty cool.
FRANKLIN: Yeah, this is actually awesome.
BLAIR: Wait. Are you saying the beard’s not cool?
BLAIR: The verdict is out.
CHRIS: Move on.
BLAIR: It is a demonstration. It is a fashion demonstration mission for me.
FRANKLIN: Is that fashion or grooming?
BLAIR: Grooming demonstration.
CHRIS: Is this a technology demonstration?
BLAIR: Actually, it’s technology withdrawal. I’ve actually not used any razor, or anything, or product. I’m going straight natural.
CHRIS: So the plan here is that we’re going to be discussing several technology demonstration missions, which is the focus of today’s show.
BLAIR: I actually have to say something. On the last technical demonstration mission episode that we did, I was knee deep. I was mired in an investigation of MEDLEY. I’ve got to say, by the way, that was very successful and I did a great job. In fact, it is now the standard, the de facto standard for all investigations across the agency.
FRANKLIN: I just don’t think that was the case.
BLAIR: Well… we agree to disagree.
CHRIS: I tell you what, since you are in that pre-investigative role, we’ll let you start off. Since we covered three TDMs this show, let’s talk about what you covered.
BLAIR: Okay, what I was looking at was the Deep Space Atomic Clock.
CHRIS: Or DSAC.
BLAIR: Or DSAC. When I first heard about this mission I immediately was fearful. I thought some kind of an atomic disruption in the space-time continuum might occur, which would be bad. It turns out that’s not the case at all. This is a very essential part of all spacecraft for flight and everything else. I was excited to actually get out to JPL and talk to Todd Ely and get into the nuts and bolts of what is the Deep Space Atomic Clock.
BLAIR: Todd, I have to confess right off the bat that atomic clock technology is not exactly in my wheelhouse of expertise. I was wondering if you could explain briefly what is an atomic clock and how is it used?
TODD: Sure. Let’s start with use. We all take advantage of atomic clocks today even though we might not know it. The GPS system that we use to navigate on Earth is based on atomic clocks. There’s an atomic clock on board each of the GPU spacecraft today, usually the size of a refrigerator. What we’re doing with this technology development is to reduce those refrigerator size atomic clocks and make them smaller, more suitable for space flight. The way the clock works is we’re utilizing a feature of nature and atoms and their ability to resonate at particular frequencies very precisely. They’re like a tuning fork but we’re using that atomic resonance to measure that frequency and compare to an oscillator that is generating a frequency or kind signal to correct that.
BLAIR: So, what’s the purpose of that? Why do we need that for our spacecraft?
TODD: We need to navigate. We need to know where we’re. The way in which we navigate today is we measure how long a signal takes to travel from the tracking station to the spacecraft and how fast the spacecraft is moving. To be able to do that, we need a very accurate frequency source and time source. Since today’s spacecraft clocks aren’t very accurate, we have to send the signal up, turn it around, and measure that time delay and that speed. With the Deep Space Atomic Clock, we’re able to put that in a spacecraft and we no longer need to turn that signal around. We can either send the signal from the spacecraft and measure it here at Earth or thinking a little forward in the future, measure it onboard the spacecraft for the spacecraft to use for navigation.
BLAIR: If this is successful, if you actually add them to spacecraft, how will we benefit from having this technology onboard the spacecraft?
TODD: Deep space navigation, it enables a more precise measurement. It also allows us to collect more tracking data. So, more data, better data, better navigation; by being able to put it onboard the spacecraft, if we have time critical events where the spacecraft needs to know where it is and how fast it’s moving at the time it’s needed, it allows that to happen. Thinking a little bit closer to home and GPS, the Deep Space Atomic Clock is an excellent candidate to replace the existing atomic clocks on board GPS today. It’s more accurate and precise than those atomic clocks. It has the potential to improve GPS performance.
BLAIR: No more “recalculating.” So, when I’m driving I can actually get to my destination without having to pass it and then turn around?
BLAIR: Awesome. I love this already.
TODD: There are some ideas that takes this technology and really miniaturize it. The version of the clock we’re building for our demonstration is maybe the size of two milk cartons but there are ways which we could reduce that even further. The key component of the clock is this thing we call a “trap” where we actually confine the mercury ions and measure that resonance that I talked about earlier. That trap is about this big, maybe an enlarged Starburst package.
TODD: But there are versions of that trap that get down to maybe a few sugar cubes.
TODD: Very tiny.
BLAIR: It’s interesting because you mentioned future. I’m just wondering are there any plans to use the Deep Space Atomic Clock for time travel possibly?
TODD: Well, I don’t think we could use the clock for time travel but we’d know how far we travelled in time if we were able to do time travel.
BLAIR: So there is hope? We might be able to find a future application for that.
BLAIR: I’ve got to tell you I was really surprised. I didn’t know how much we relied on atomic clocks for navigation. You think about it, it’s obviously difficult for boats. That’s why they use them but for spacecraft being in space, it’s really important to know exactly where you are. It’s really good technology.
CHRIS: The cool part about that is how small can they get the technology? How can they miniaturize?
FRANKLIN: Yeah, a double pack of Starbursts? I was sitting there, like yeah, how do you get from a refrigerator down to…
BLAIR: To a snack size basically.
FRANKLIN: Snack size.
BLAIR: You’re moving from a meal to snack size with all the effectiveness.
CHRIS: It is possible one day that you’ll see an atomic clock the size of a microchip.
BLAIR: Well yeah, I wonder because everything is getting smaller. And if it’s in every single spacecraft, pinpoint accuracy.
BLAIR: And like I said I long for the day where the GPS does not ask me to recalculate or do a U-turn in an uncomfortable spot.
FRANKLIN: It starts to buffer when you’re in the wrong part of a neighborhood. You like, wait. Oh, oh.
BLAIR: That can be bad sometimes.
CHRIS: You had a chance to go to L’Garde to talk about solar cell technology.
FRANKLIN: Yes, I talked to the company’s CEO, Nathan Barnes about the Solar Cell demonstration. We stood in their facility, their workshop and talked about this technology and what’s coming up with their mission.
FRANKLIN: I’m here with Nathan Barnes, the project manager for the Solar Sail Demonstrator, or SSD.
NATHAN: Yeah, that’s a little boring name. We like to call it the Sunjammer project.
FRANKLIN: Give us a little backstory on the name, Sunjammer.
NATHAN: Sure. Sunjammer is a short story written by Arthur C. Clarke. It was published in the 1963 Boys’ Life. We contacted Arthur C. Clarke’s estate and asked if he wouldn’t mind us using the name of the story for our project. The story is about a solar sail yacht race taking place far in the future and seemed very fitting.
FRANKIN: Now, you guys didn’t just come up with the Solar Sail. You had to have been working on this for some while before you got involved with NASA.
NATHAN: Very correct, very correct. We’ve been studying solar sails and writing designs of solar sails, papers about solar sails, and so on and so forth for many years.
FRANKLIN: What is the need for this technology?
NATHAN: What one must think about is there another form of propulsion. We have rockets. Everyone knows what rocket motors are. But solar sails are another form of propulsion just like them. They’re a very low thrust form of propulsion but they’re a perpetual form of propulsion. They keep going. They will continually be thrust by the light of the sun. So, there’s no need to carry consumables. There’s no need to throw stuff out the back in order to push us forward. Because of that, it will enable a whole host of unique missions that are specifically tailored to solar sails.
FRANKLIN: What kind of weight are we talking about with this solar sail?
NATHAN: We’re trying to conform it to a standard that says it needs to be about 28 inches by 28 inches by about 38 inches. We’re roughly the size of a dishwasher or a washing machine in your household. When we deploy, we’re huge. We’re 1200 m2, which is roughly a third of an acre. We’re very low mass. We’re targeting that once we’ve jettisoned a handful of consumable items our solar sail is in the neighborhood of 35 to 40 kg. We’re incredibly large, 1200 m2, and incredibly lightweight. Those two things, Newton tell us, force equals mass times acceleration. Therefore, if we increase the force by making the sail larger and collecting more of that photon pressure, and we decrease the mass by pinching every penny and removing every bulk that we don’t need, then we’ll have a higher and higher characteristic acceleration, which really defines the performance of our sail and tells us where the sail can go to and what it can do for us. For this particular mission, we’re going to take our sail and demonstrate that we can use solar sails for advance storm warnings. Currently, NOAA monitors coronal mass ejections and informs folks that are interested in the data of incoming solar storms, solar flares. They monitor this at the L1 point, which is roughly a million and a half km from the Earth towards the Sun on a line that connects the Earth to the Sun. With that station, they get roughly 40 to 45 minutes of warning time. That’s good. That’s great. We’d like to do better. We’d like to give them more warning time. What we want to do with this solar sail is fly to, and maintain a position that’s roughly 3 million km from the Earth instead of that 1.5. Three is twice 1.5. It means we’ll get about 80 to 90 minutes of warning time for the ground operators.
FRANKLIN: To get to a LaGrange point, the L1 point, you’re not the primary mission. You had to actually catch a ride.
NATHAN: That’s right. For those in the spacecraft and launch community, they sometimes call us secondaries, cockroaches. Yes, we’re hanging onto the side. We’re glad to be that and we’re glad to get a ride and get launched. We’re going to ride on a Falcon 9 v1.1, currently scheduled to launch in November 2014.
FRANKLIN: How does it maneuver? How does it work in space?
NATHAN: Yeah, very good question. The way we’re propelling ourselves is with this solar radiation pressure. Our square solar sail actually has small, little solar sails out of each corner of the solar sail. Those little solar sails can be tilted and twisted in order to increase or decrease the amount of solar radiation pressure they’re getting at each corner. You can imagine if we turn off the pressure on this side and increase the pressure on this side, we make the sail rotate. It’s very similar to the control surfaces or ailerons on an airplane.
FRANKLIN: When I think about this large sail that’s going to be put into such a small box, I’m thinking this has to be some lightweight material.
NATHAN: Our solar sail is built of a whole host of very lightweight, and very cutting edge materials. The material most visible, most recognizable is the material that the sail area itself is made of. I have a little piece here with me. Our sail area is built of a Kapton material. It’s incredibly thin. This is 5 microns thick which is many, many times thinner than a human hair. It’s been coated on this side with a blackened chromium. The chromium is so thin that you actually see mostly the yellow of the Kapton coming through. On this side, this is coated with an aluminum material. When the photons strike this, this is the side that reflects them back towards the sun or wherever they may go to. This is the side that actually faces the sun and propels the sail. The next step beyond that… this is…
FRANKLIN: Saran wrap.
NATHAN: This is…
FRANKLIN: Saran wrap.
NATHAN: This is .9 micron Mylar. This is incredibly difficult to work with but we have worked with it and built sail type materials out of it. This material is so gossamer so lightweight, that now it’s just stuck to me. Right? This is probably the direction of sails in the future.
FRANKLIN: I want to know who was your nemesis?
NATHAN: Our nemesis?
FRANKLIN: Your nemesis.
NATHAN: My nemesis?
NATHAN: I don’t know that I have one.
NATHAN: No, I think that’s okay.
FRANKLIN: Superman is okay?
NATHAN: Yeah, I think so.
FRANKLIN: Your sole mission of the Solar Sail was not to block out the light?
NATHAN: Absolutely not.
FRANKLIN: So that Superman will not have his powers.
NATHAN: For one thing out sail is pretty small compared to the Sun but we did have some notions of when we launched the sail maybe we could make it do this a couple of times; to wink at the Earth.
FRANKLIN: You’d be able to see that too, right?
NATHAN: Well, if we were close enough we probably could but the physics, I think, probably won’t work out for that.
FRANKLIN: You’re looking at the sail and you’re looking at the technology to say we could make this bigger. We could go further.
NATHAN: Much bigger, much bigger. One of the things we’re actually going to study with this, and it’s a very far out idea, very far out project, is using it to beam sunlight down to the Earth on the other side of the Earth when the Sun is not on it. We’ve studied and worked with a couple folks and written a proposal recently to study that and see if there’s any merit to it. It’s a good thing, right? No nemesis. That’s helping humanity there.
FRANKLIN: Was it me, or did Nathan look like Lex Luthor?
CHRIS: I thought someone was going to bring in a case and open it up and there was going to be Kryptonite in there. The resemblance was uncanny.
FRANKLIN: A real cool guy.
CHRIS: But he didn’t know Superman.
BLAIR: Okay, there’s some debate about that.
FRANKLIN: Yeah. It was the way I rolled out the question.
BLAIR: If he really is a super villain, then he’s obviously not going to admit that on camera.
CHRIS: That’s true.
BLAIR: I think he was playing close to the vest.
FRANKLIN: That is true.
BLAIR: I mean super villain with all do respect. It’s the first one we’ve had on the show.
FRANKLIN: Who had my camera on that shoot?
CHRIS: That was me.
FRANKLIN: Why didn’t you tell me I had a piece of macaroni on the bottom of my lip?
CHRIS: I didn’t see one.
FRANKLIN: Oh man, I’m sure Ryan is going to show it with a circle around it right now.
VOICE: Hey! Who put that there?
BLAIR: Chris, for the third technology demonstration, tell us a little bit about what you looked into.
CHRIS: I had a chance to talk with Ian Clark at JPL. His technology was LDSD or Low-Density Supersonic Decelerator.
CHRIS: What is LDSD all about?
IAN: Low-Density Supersonic Decelerators are describing a class of aerodynamic decelerators that we are developing to enable the next generations of missions to Mars. These include large robotic class, like what we just landed a year ago but bigger. We want to land at higher elevations then we have previously been able to get to before.
CHRIS: What are the new technologies that we looking at now?
IAN: Well, there are three new technologies that LDSD is developing. Two devices are things that we call Supersonic Inflatable Aerodynamic Decelerators or SIADs. These are similar to parachutes in that they are pressurized devices but rather then having an opening at the front, they’re closed volume devices. These are things that are inflated at speeds much higher than we typically use parachutes and they’re more integrated to the vehicle. They’re actually attached at the front of the vehicle to change the shape and size of the vehicle rather then being deployed behind the vehicle. The other one is a new improved, larger, supersonic parachute; the biggest parachute that will have ever been flown at the conditions we’re testing; that will ever be used at Mars. We take a parachute that weighs only 300 lbs. but it will generate 150,000 lbs. of drag.
IAN: An enormous aerodynamic load.
CHRIS: Very efficient.
IAN: Extremely efficient. The basic parachute design that we’ve had is a design we thought we could improve on. We’re improving on it in a couple different ways; the basic shape. How the geometry is actually laid out, we can improve on. We understand the aerodynamics a little better now.
IAN: We can take advantage. The other thing we can do is just make it bigger. Parachutes are very fickle devices, particularly supersonic parachutes.
IAN: When we have to use them like we do at Mars, it’s behind a very large, blunt vehicle. That vehicle is screaming through the atmosphere. It’s punching a hole in the atmosphere. All the air is rushing in behind it to fill the vacuum that it’s creating.
IAN: That creates a very turbulent, very unsteady environment for the parachute to live in. You need a particular kind of parachute. We’re going to develop a new shape and we’re going to make it bigger. The bigger it is, the more drag it can generate. The more area it encompasses, the better it’s able to slow the vehicle down, the bigger the vehicle you can have in front of it if you’re trying to slow down.
CHRIS: Right. You talk about a bigger parachute. How much bigger than the current technology that we’re using now?
IAN: Well, MSL parachute was a little over 60 ft. in diameter. We’re looking at parachutes that are over 100 ft. in diameter.
IAN: So, area wise, we’re about 2½ times the area, 2½ times the drag of the MSL parachute.
CHRIS: You developed another technology that actually will help release that parachute from the spacecraft.
IAN: We did. Again, when we tested the technology to scale, nothing was coming easy. The way we typically deploy a parachute is something we call a mortar. It’s like a giant cannon. When you get to parachutes the size we’re testing, you can still us mortars but the difficulty is the mortar wants to sit in the middle of the vehicle because it generates a very high reaction load, a lot of force. If that force is put off centerline of the vehicle, out on the perimeter, it can it generates torque. You can start to tumble the vehicle. We’re going to use another inflatable decelerator that’s deployed and inflated behind the vehicle, much smaller but can be shot by using a mortar without tumbling the vehicle. We’re going to use that to pull the parachute off the back of the vehicle but this one is a very particular design. We had to go back to something called a ballute It was a device that was originally developed in the early 1960s. We’ve gone back to the literature and said, yes, they tested some small ones. We’re going to build a very large one and we’re going to use that. That’s what we’re doing. We’re developing new parachutes to replace the one that we inherited. It’s bigger, better performing. And we’re developing something called SIADs, these inflatable devices. Things that are packed in very tight crevices on the periphery of the vehicle that we can inflate and deploy at speeds even greater than what we deploy parachutes. There are lots of different kinds. Part of LDSD, we’re developing two flavors of SIADs. Something we call SIAD-R. The “R” stands for robotic; and SIAD-E or exploration. The two flavors are targeted to different mission classes. Robotic would be the next evolution of the Curiosity rover, something a little bit bigger. Exploration is starting to look at what if we do want to start landing the 3, or 5, or 10-ton payloads on the surface of Mars? That SIAD looks very differently and behaves very differently then the one that we need for something that is just a little bit bigger than Curiosity.
IAN: The –R looks like an inflated donut. It’s a device that we can inflate to moderate pressure, about 4½ psi or a fraction of what you inflate your car tires.
IAN: Even at 6 meters and 4½ psi, it behaves very rigidly. We like rigid objects because we understand how they behave. You don’t have to worry about them deforming under different loads or interacting in their environment differently. Because it’s rigid it scales very well.
IAN: We know how to work with things that scale. We like to build little small 6 in. diameter models or 2 in. diameter models and put them in a wind tunnel and test them to understand the aerodynamics. We feel comfortable because they’re rigid, because their shape is the same. We can take them to 4½ meters in diameter and they will behave. The aerodynamics of that 4½-meter device will be the same as the little 2 in. or 6 in. model that we tested. We can only go so far with that. Six meters is about as big as we think we can build something and still have it behave rigidly.
CHRIS: Rigidly, right.
IAN: Eventually, we’re going to have to tackle the problem of what it means not to be rigid. So, we went with an entirely different device. It’s called an attached isotensoid and it’s much more flexible but it’s integrated to the vehicle. It’s right up at the front. It basically changes the shape of the vehicle and also makes the vehicle look bigger to the oncoming flow. Think about the ram air scoops that are on the top of your muscle car, pulling in air at 150 to 160 mph. We have similar scoops on sides of our SIADs that are pulling air at 2,000 mph. That air comes into it, helps inflate, helps give it a nice, good shape to the vehicle, and helps generate that shape necessary to slow our air shell down.
CHRIS: You have to develop a piece of material that will actually be able to withstand that. What kind of materials are these going to be made out of?
IAN: Parachutes are made from materials similar to what your camping tent might be made of, nylons for example. When we build science, we need things that are stronger. Because we’re using them at higher speeds, they see more heating. They need to be a little more temperature resistant.
IAN: We actually have two different materials that we’re working with. One is Kevlar, a very similar type Kevlar that is used in bulletproof vests.
IAN: It’s extremely strong, very flexible and still can be made very lightweight.
IAN: That’s what we build the SIAD-R out of. For SIAD-E, we’re using a slightly different material called Technora, very similar looking, similar behaving to Kevlar, just a little different properties that make it more amenable for something like SIAD-E. Otherwise, these are very thin materials, thinner then the fabric on your shirt for example; very lightweight.
CHRIS: What a great way to wrap up the show and a great technology with LDSD and all the three technologies we talked about.
BLAIR: It still stuns me how much development there is to slow things down. The balloon, the inflatable idea, that’s just really cool stuff.
FRANKLIN: New age space brakes.
BLAIR: Yeah, it’s definitely another; like the front brake on a 10-speed.
CHRIS: From clocks to solar cells to decelerators, we covered it all.
BLAIR: And what’s next mission? K10?
CHRIS: That’s right. Franklin and I had a chance to go out to NASA Ames to cover the K10 test where an astronaut from Space Station actually operated the K10 rover on the ground.
BLAIR: In conjunction with a sleep deprivation study.
FRANKLIN: Yeah, we were out there pretty early in the morning covering the test through the morning into the afternoon but it was a good time. I think you’re really going to enjoy the show.
BLAIR: Can’t wait.
CHRIS: You’re watching NASA EDGE.
BLAIR: An inside and outside look…
FRANKLIN: …at all things NASA.
BLAIR: I love the new look in here.
CHRIS: Are you keeping the beard?
BLAIR: I am keeping the beard until I get complaints.
FRANKLIN: It actually looks pretty good.
BLAIR: And it’s real. I did not apply this this morning.
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