Ep. 605: Sounding Rockets

Posted on May 17, 2021 in Astronomy, Missions, podcast, Science, Sky Phenomena, Spacecraft | 0 comments

Last week we talked about balloon-based astronomy. This week we’re going to talk about putting balloons on rockets and making observations mid-flight. Welcome to the world of sounding rockets.

Download MP3 | Show Notes | Transcript

Show Notes


VIDEO: Starship | SN15 | High-Altitude Flight Test (YouTube)

PODCAST: Ep. 604: Balloon Astronomy (AstronomyCast)

Parabolic flights (ESA)

PAPER: Biology on Sounding Rockets: History, Requirements, Results and Scientific Interpretation (ADSABS)

Model Rockets (NASA)

Falcon 9 (SpaceX)

Electron (Rocket Lab)

What Is Microgravity? (NASA)

What is Airglow? (Universe Today)

Patrick Space Force Base (Cape Canaveral)

White Sands Missile Range (U.S. Army)

Wallops Flight Facility (NASA)

Pacific Spaceport Complex (Alaska Aerospace)

Kerbal Space Program

Low Earth orbit (ESA)


Chandra X-ray Observatory (Harvard University)

Goddard Space Flight Center (NASA)


Supernova Remnant (Swinburne University)

What Is the Sun’s Corona? (NASA)

New type of aurora revealed in 19-year-old video (EarthSky)

Sunspots and Solar Flares (NASA)


Transcriptions provided by GMR Transcription Services

Fraser:                         AstronomyCast episode 605: Sounding Rockets. Welcome to AstronomyCast, our weekly facts-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, publisher of Universe Today. With me as always is Dr. Pamela Gay, a Senior Scientist for the Planetary Science Institute, and the director of CosmoQuest. Hey Pamela! How you doing?

Dr. Pamela Gay:         I am doing well, and oh my goodness, you said that quickly today!

Fraser:                         Did I?

Dr. Pamela Gay:         You did!

Fraser:                         Well, you say something 600+ times, and you just gotta find a way to mix it up, to add a little something to it.

Dr. Pamela Gay:         You’re just in a rush to launch our topic. That’s all. You’re just in a rush to launch our topic,

Fraser:                         Yeah, exactly. When you work in sounding rocket Astronomy, you gotta go fast. We’ll just slow it down. We’ll take our time. We’ll get there.

Dr. Pamela Gay:         When I laugh, it moves my camera. I need to not do that.

Fraser:                         Yeah, I noticed that. For the people who are listening to this as a podcast, you have no idea. But definitely, Pamela’s entire scene is wiggling and jiggling around. Sort of like a flap on SN15.

Dr. Pamela Gay:         And we would like to congratulate the good folks at SpaceX for their successful landing of the SN15 starship prototype. May all future rockets stand so steady.

Fraser:                         Yes! Congratulations! Now, do it from space!

Dr. Pamela Gay:         Yes.

Fraser:                         That’s it.

Dr. Pamela Gay:         Or at least to space.

Fraser:                         To space, I’m not too worried about.

Dr. Pamela Gay:         Okay.

Fraser:                         From space, that’s the key. We’ve seen rockets go to space, but to see a rocket, a two-stage fully reusable rocket system, go to space, return from space, land on the pad, that will be the game-changer. So, we can’t wait to watch how that heat tile works. All right. Last week, we talked about balloon-based Astronomy. This week, we’re gonna talk about putting telescopes on rockets, and making observations mid-flight. Welcome to the wild world of sounding rockets.

All right, Pamela, I think for people who aren’t even familiar with this topic, it sounds impossible. You take a rocket that’s on a parabolic flight, a fairly relatively short flight, measured in minutes, hours at the most, and you put a telescope on this rocket, and attempt to do Astronomy from a moving platform that is going to crash or land with a parachute at some point. How does this work? How is this even possible?

Dr. Pamela Gay:         So, what’s amazing is it’s not just Astronomy. It’s all sorts of different science. And while Astronomy seems hard, what really got me is one of the other types of science they do with sounding rocks is on the fertilization of different biologicals. And so, the idea that you’re launching critters that are alive, and expecting them to successfully reproduce in that short period of time, –

Fraser:                         Yeah.

Dr. Pamela Gay:         – yeah, it’s kind of amazing. So basically, sounding rockets, which get their name from the same process as sounding the bottom of the sea, the idea is instead of probing the depths of the water, you’re probing the heights of the atmosphere. These sounding rockets are giant model rockets, for all intents and purposes. They have a solid rocket engine, so once you fire them, they go. They go at a lower velocity than your standard orbital rocket, which means you’re not gonna be quite as shaky and long enduring, and violent of a takeoff.

And they go up super-fast, they then linger for typically – but, like you said, it can be longer – but typically 5 – 20 minutes at their highest point, and then they come down, and they expand a parachute, the engine drops one way, the scientific equipment hopefully flutters down gently. But as someone who’s launched my share of non-successful model rockets, occasionally things go slightly sideways. But these are just super simplistic systems, often actually military overstock, –

Fraser:                         Right.

Dr. Pamela Gay:         – and students, researchers trying to study the atmosphere, all sorts of different people, get to probe that place between how high the weather balloons go, and how high you have to go to actually be a satellite that keeps orbiting.

Fraser:                         So, if you were to just compare, – we’re all quite familiar with, say, a Falcon 9 rocket sitting on the launch pad.

Dr. Pamela Gay:         Yeah.

Fraser:                         If you were to look at a sounding rocket, what would it look like in comparison.

Dr. Pamela Gay:         You’d have this desire to go, “Oh, aren’t you so cute!” They’re shorter than a house in some cases. They’re small. They can be just 16 feet in length, in some cases. They’re much more similar to the electrons, which are still essentially a really big sounding rocket. They do hit lower Earth orbit. With –

Fraser:                         Yeah.

Dr. Pamela Gay:         – the electrons. But they’re tiny. And they’re essentially the same thing as a military missile. Which is discouraging.

Fraser:                         I imagine like a scaled-up version of one of those missiles that say, a fighter jet is carrying on the ends of its wing.

Dr. Pamela Gay:         In some cases, they’re almost identical.

Fraser:                         Or are.

Dr. Pamela Gay:         It’s not so much the ones that the fighters are carrying, as the ones that some of the bigger bombers are carrying.

Fraser:                         Mm-hmm.

Dr. Pamela Gay:         Yeah. You’re talking basically 16 foot in length. That is essentially 5 meters in length for the smaller ones. They do grow from there. And most of that is going to be your solid rocket propellant and engines. And then, above that, you stick your experiments. And just like with any rocket, sometimes it’s all one large experiment, and sometimes it’s a whole bunch of little, tiny experiments all going up together to get their 5 – 20 minutes of – well, microgravity experience, and exposure to vacuum, and exposure to a part of the atmosphere that’s super cool, because it’s where Aurora happens. It’s where airglow happens. And it’s someplace we don’t otherwise get to really explore.

Fraser:                         Well, and I guess that was my next question, was that typically, we’re very familiar with rocket launch facilities being Cape Canaveral, –

Dr. Pamela Gay:         Yeah.

Fraser:                         – in South America, and so on. But these sounding rockets often launch from different facilities.

Dr. Pamela Gay:         Yes. Yeah, so you see them launching – well, White Sands Missile Arsenal is one place.

Fraser:                         They got missiles. Sure, yeah.

Dr. Pamela Gay:         Right. And it’s cool, because that particular location, they’ve launched undergraduate experiments, and then they come down and land out in the white sands. And so, you go trekking through the dunes to go grab your parachuted-down experiment. They launch them also from Wallops on the east coast. So, you see these going up from still areas where you’re not flying planes overheard, but you still see them going up from smaller facilities that are a lot more accessible for people that just need someplace to go launch.

Fraser:                         And one that we see a lot of launches from as well is the one in Alaska. Kodiak?

Dr. Pamela Gay:         Kodiak, yes.

Fraser:                         Yeah. And I mean, that’s the place you study the magnetosphere, and Auroras, and things like that. Okay, so we know a little bit of the launch facility. Let’s talk a little bit about the kinds of flights that these rockets take. Are they straight up? Straight down? ‘Cause normally, when we think of a rocket launch, they’re going mostly sideways to get into orbit.

Dr. Pamela Gay:         And these do not. They go straight up, they come straight back down, and because of this essentially vertical trip that they go on, they hover above the point on the planet above where they launched essentially.

Fraser:                         Right. That’s very convenient, that you don’t have to go thousands of kilometers down range to find your experiment.

Dr. Pamela Gay:         Which is so much better than what so often ends up happening with weather balloons that can go across national borders, and buh-bye equipment. You do have to worry about how far things end up drifting due to parachutes, –

Fraser:                         Mm-hmm.

Dr. Pamela Gay:         – but that is a different problem. So, if it’s a nice still day, things go up. And the way it works is they don’t literally hover. Nothing except for a hummingbird or a balloon literally hovers. But as they go up, they eventually dispel all their fuel, and gravity takes over. They go slower and slower. And then, as they start to run out of upward momentum, microgravity kicks in.

And they’re also at this point high enough up that they can start to do the vacuum experiments, do the ionospheric experiments, do biological experiments that need the microgravity environment. And during that 5 – 20 minutes it takes for them to do that final hit zero and then start back down, as they’re coming back down, it takes them time again to build up velocity, and to lose that microgravity environment, which really goes away as soon as the parachute deploys.

Fraser:                         Right. If you’ve ever played Kerbal Space Program and failed to get your rockets into orbit, you’ve at least experienced what it’s like to have that process, where you’re out of fuel on your rocket, and yet it’s still gaining altitude because of the momentum left over. But as time goes on, your rocket is going up slower and slower, until finally you reach the top point, your apoapsis of your flight, and then you start to come back down faster and faster and faster until you crash. And so, in fact, once the rocket engine turns off, you still got a long time of upward flight.

Dr. Pamela Gay:         Yes. And the key for microgravity here is you are technically weightless as long as you’re falling at the acceleration of gravity. And so, the microgravity portion of your experiment can go from as soon as you start falling to when that parachute deploys, and you radically change velocities. But microgravity is only part of the experiments they do. The other stuff that requires them to be in the highest points in the atmosphere from 40 kilometers up to – they can go to 1,000 kilometers, but more often, it’s more like 120 kilometers –

Fraser:                         Hmm. So space.

Dr. Pamela Gay:         Yeah. So space. Most sounding rockets can find themselves to that region between top of weather balloon and bottom of lower Earth orbit, but it’s within that area that you can do the, “Hey, I’m above the atmosphere! Let’s look at the sky in x-ray.” “Hey, I’m above the atmosphere! Let’s look at the sky in ultraviolet.” “Hey, I’m in the cool part of the atmosphere. Let me study Aurora.  Let me study the magnetic fields.” And so, the same technology that gets used on satellites like TRACE and Chandra in the x-ray, all of these technologies got pioneered 5 – 20 minutes at a time on sounding rockets, and then put into orbit –

Fraser:                         Right.

Dr. Pamela Gay:         – when we knew they would work.

Fraser:                         So, when we were talking about balloon-based Astronomy, we talked about the interesting gimbaling systems, the procedures that they have to go through to try to balance out the various forces that a science payload dangling from the end of a balloon has to go through. So, what do they do to compensate for a vastly different experience of trying to put your experiment on a rocket?

Dr. Pamela Gay:         So, here, at least, they’re dealing with stuff where you’re not trying to narrowly focus the same way. A balloon-born experiment that is designed to map out the comic microwave background has to have fairly precise pointing. But x-rays, as we’ve discussed before, really do not like to be focused. They kind of deny you. So, if you can keep yourself reasonably pointed in the same direction, you’re reasonably not focusable x-rays are generally okay.

Most of the experiments they’re doing however, it’s more a matter of trying to see what the In-Situ experience is at that altitude. And sometimes, they’re just doing technological checks as well. So, one of the experiments that was recently launched by a group of students was to see if we can start replacing some of the more dangerous thruster fuels we use in space with green fuels.

Fraser:                         Mmm.

Dr. Pamela Gay:         And so, they did test firings, they tried a solar blanket, and the goal was to simply see what kinds of – well, pollutants do you end up mucking up the outside of your experiment or your spacecraft. So, you don’t need to be stable, you just need to be stable enough that your experiment doesn’t fall apart.

Fraser:                         Right. And so, I mean, I think that’s a great example, that you just need to be able to puff your propellant a couple of times when you’re in the microgravity as you’re falling down to Earth and detect whether or not that part is actually working. You already know what the chemicals are, so you’re just trying to find out will you get the kind of change and velocity that you require? You talked about this idea of In-Situ. So, you are sampling your local environment –

Dr. Pamela Gay:         Yes.

Fraser:                         – at various altitudes.

Dr. Pamela Gay:         And for a biological experiment, I don’t know. But if I was one of those little, tiny itty bitty little mostly not-brain-having biologicals, and you shot me upwards at 12G, once it got down to micro G, and I’m no longer being squished, I’m gonna be completely fine, if I’m wobbling a little bit.

Fraser:                         Right. And I guess that’s one of the other issues as well that I gotta deal with, is handling the G’s of the launch. ‘Cause it can be extreme. But then, also being able to handle the zero G’s as well, and all the rattling and shaking and so on. And I guess that is also a good chance to find out if your experiment is gonna be able to handle the rigors of a launch.

Dr. Pamela Gay:         Well, yeah. They have some amazing facilities, especially out at Goddard Space Flight Center for shaking the bejesus out of something before they launch it into outer space.

Fraser:                         Yeah.

Dr. Pamela Gay:         It was on such a shake table that JWST experienced the loss of a few bolts in a way that we probably shouldn’t get into today.

Fraser:                         Yeah.

Dr. Pamela Gay:         But what’s more to the point is while we can pull things down to vacuum on Earth, while we can shake things up on Earth, what we can’t do is figure out if you shake them, you vacuum them, and then you use them, do you get the data you want?

Fraser:                         Right.

Dr. Pamela Gay:         And it’s that extra stuff that you can do with sounding rockets. You shake them, you accelerate them, and then you ask them to do their job. And with x-ray detectors, this is how we figured out just what would be possible and got to the point that we have the amazing systems we have today.

Fraser:                         All right, so you were sort of starting to lead into this, about this idea of x-ray Astronomy. What are the things that can only be done at that high altitude that the sounding rocket regime, as opposed to the balloon regime, and the orbital regime? What can you really only do with a sounding rocket? Or best do? Inexpensively, affordably do? Yeah.

Dr. Pamela Gay:         So, while you can start to get into the infrared and microwave radiation with something like a weather balloon, you can’t so much get into the x-rays. You can start to. But our atmosphere is pretty stubborn when it comes to blocking out certain shades of light. And again, this is something we are grateful for. X-rays are dangerous, they cause cancers – small amounts. Get your teeth x-rayed at the dentist, people. That level of x-ray is not bad.

But if we were exposed to the amount of x-ray that is generally being produced in outer space, we wouldn’t be designed the way we are right now. We’d be something entirely different. But once you start getting up above the atmosphere, above that 40 kilometers in a weather balloon, as happiest stopping at, then you can start to open up to the entire x-ray sky. And now, you have supernova remnants. You have –

Fraser:                         Mm-hmm.

Dr. Pamela Gay:         – effects with the solar corona that you can’t see otherwise. There’s entire areas of science that we just otherwise can’t do, that we can start to do with sounding rockets for 5 – 20 minutes at a time. So, again, test your equipment with this, then –

Fraser:                         Right.

Dr. Pamela Gay:         – launch it and do the awesome stuff with the launch.

Fraser:                         What do you think the future holds? I mean, we’re starting to move into this world where we’re seeing reusable rocketry, we’re seeing smaller rockets that are capable of orbiting. Is there still a bold future for these sounding rockets?

Dr. Pamela Gay:         I think how they get used is going to evolve over time. One of the benefits of sounding rockets that we haven’t discussed so far is once you build something that fits nicely within the experimental compartment on a sounding rocket, it goes up, it comes down on a parachute, you tweak it, you relaunch it. These are experiments that can be run over and over again if you design them right. And if you’re trying to test and do incremental design on that new camera on that new sensor, if you want to sample the magnetosphere when it’s most active, and when it’s most passive, this ability to repeat your –

Fraser:                         Mm-hmm.

Dr. Pamela Gay:         – experiments over and over with sounding rockets is something that’s low-cost and unique.

Fraser:                         Yeah, that’s really interesting. This idea that you can iterate, because –

Dr. Pamela Gay:         Yes.

Fraser:                         – the iteration is absolutely key in any kind of engineering process that you’re doing. So, for example, you build some interesting infrared or x-ray sensor, and you wonder, “Can it see x-rays?” Well, you don’t know, because you have to go to space. But if you send this thing to space, then you can’t get it back.

Dr. Pamela Gay:         Right.

Fraser:                         Right? And so, you put the thing on a sounding rocket, you send it to space, it takes a bunch of pictures, it falls back into your arms, you take a look at the picture, and go, “Oh, this didn’t work. That didn’t work. Let’s make some tweaks.” Then you put it on another rocket, you send it, you throw it up into space, see it takes a look around, and then it falls back into your hands, and then you just keep doing this incremental approach until you feel like you’ve got something that you’re willing to throw so far into space that it never comes home.

Dr. Pamela Gay:         I now have this mental image of a graduate student pulling away from the hands of their advisor and racing across the dunes at White Sands to catch their experiment that probably weighs more than they can hold.

Fraser:                         Yeah, I’m sure it has happened more than once, with them driving going, “No! Don’t let it crash! Don’t let it crash!”

Dr. Pamela Gay:         But I mean, just beyond the incremental design, our atmosphere is changing. There are so many different kinds of Aurora, it’s starting to feel like a month doesn’t go by without a new, “And this new Aurora has been figured out.”

Fraser:                         You read the press releases today. A new one was discovered today.

Dr. Pamela Gay:         Yeah.

Fraser:                         When we’re recording this, yeah.

Dr. Pamela Gay:         And so, with all of these different atmospheric effects that change with the seasons, with the solar cycle, with the timing of when we get hit by a solar flare, being able to quick fire a sounding rocket with an experiment you have sitting there ready to go, –

Fraser:                         Yeah.

Dr. Pamela Gay:         – this gives us the chance to sample our changing atmosphere. And so, it’s iterative design on both sides where it’s space that iterates periodically, and we need to sample those changes, and it’s us being able to iterate the designs of our instruments, and test things that, as you stated, we get back.

Fraser:                         Yeah.

Dr. Pamela Gay:         Don’t catch your rockets, humans. Do not do this unless you are a Space-X barge.

Fraser:                         I do love that idea of seeing something interesting happening in the ionosphere. Some Aurora activity. You aiming your rocket, and going, “Now!”

Dr. Pamela Gay:         Yeah!

Fraser:                         “Let’s see what that is!” And then, away you go, and being able to get a device into the actual spot and see what’s going on locally.

Dr. Pamela Gay:         I mean, this is just such a cool topic as someone who flung rockets into space with more – never launch Earthworms, people. Never launch Earthworms. When the teacher sends you out in the field to find a cricket, and you find an Earthworm, don’t launch the Earthworm. All right, that’s all I have to say on that topic. But yeah, these are the things I launched as a kid, just built bigger. And they’re cool.

Fraser:                         Fascinating topic. Thank you so much Pamela! And we’ll talk to you next week.

Dr. Pamela Gay:         It’s my pleasure, Fraser!

Fraser:                         Now, do you have some names for us?

Dr. Pamela Gay:         I do! As always, we and our enthusiasm are brought to you by you. It’s because of your donations that we’re able to maintain our websites, edit our shows, and have an entire team of people that keep us sane.

And this week, I would like to thank Ben Lieberman, Laura Kittleson, William, Robert Palsma, Joe Hollstein, Paul Jarman, Jos Cunningham, Les Howard, Emily Patterson, cacoeraph, Adam Annis-Brown, Ed of the Universe, Just Joe, Gordon Dewis, Bill Hamilton, Helge Bjorkhaug, Nicole Vorisek, Frank Tippin, Jack Mudge, Joshua Pierson, Sydnie Walker, richard rivera, Thomas Sepstrup, Alexis, William Baker, Matt, Jean-Francois Rajotte, William Andrews, Ron Thorrsen, Jeff Collins, Harald Bardenhagen, Jordan Turner, and Arcticfox. Thank you all. Thank you for everything you do that allows us to do what we do.

Fraser:                         Thanks, everyone! And we’ll see you all next week!

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