< From the physics of g-force to weightlessness: How it feels to launch into space

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EMILY KWONG: You're listening to Short Wave from NPR.

REGINA BARBER: Hey, Short Wavers, Regina Barber here with some exciting news. All summer long, we'll be reporting out a new series we're calling Space Camp. Every Tuesday, for the next nine weeks, me and my copilot, Emily Kwong--

KWONG: Hi, Gina.

BARBER: Hey-- we're going to travel deep into space, Em.

KWONG: Yeah.

BARBER: And we're going to explore all of the wild, inspiring phenomena in our universe, like different kinds of planets, stars, and even black holes.

KWONG: And we're starting right here on planet Earth with "Launch" to quite literally launch our series, and also because there's been a lot of launches into space recently. In just the last week, there was Boeing's Starliner. Then there was SpaceX's Starship, which was crewless and a bit more of a test.

BARBER: Yes, so let's buckle up, Em, and let's start our launch of this series.

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BARBER: Launch is something that Navy Captain and NASA astronaut Wendy Lawrence is very familiar with. She was an astronaut from 1992 to 2006, and her first launch was in 1995 on the space shuttle Endeavour.

WENDY LAWRENCE: Launch is one of those things that you always look forward to. It never got boring.

BARBER: She remembers as a very surreal experience.

LAWRENCE: The moment that really kind of crystallizes it for you is when all the engines cut off, and suddenly you're kind of thrown forward in your seat up against your restraining harness. You have a view out the window, and you're like, wow, look, the Earth really is curved.

BARBER: Wendy said it was a beautiful view but that she couldn't really fully take it in, in that moment.

LAWRENCE: You would think you would have more of an opportunity to just really savor the fact that, oh, I'm in space. This is awesome. You unstrap from your seat, and instantly, you're not very coordinated.

BARBER: And so, with the help of Wendy and many other experts, we're about to boldly go where few have gone before-- to outer space.

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KWONG: Today, on the show, we launch. Short Wave gets into the basics of a launch, from the physics to the weightlessness experience. And we ask why there is an increasing amount of things to avoid once you reach Earth's orbit. You're listening to Short Wave, the science podcast from NPR.

BARBER: OK, Em, let's get more into what it takes to launch a rocket with astronauts into space.

KWONG: Yes. OK, so for answers on just a basic physics level, I reached out to Moriba Jah. He's a professor at the University of Austin, Texas, co-founder of Privateer and GaiaVerse Ltd. and an astrodynamicist.

BARBER: Academic speak for somebody that studies how things move in space.

KWONG: Correct, yeah, and he threw it all the way back to 1686.

MORIBA JAH: There's this dude whose name is Isaac Newton.

KWONG: [CHUCKLES]

JAH: He had, you know, a few cool things to say. And one of the things that we can attribute to his work was a set of laws of motion.

BARBER: Yes, I know those three laws very well. The law I think he's going to talk about is that for every action, there's an equal and opposite reaction, right? That's Newton's third law. So imagine you blow up a balloon, hold the end, then you let go. What happens?

KWONG: The balloon should, like, move away from us.

BARBER: Yeah.

JAH: But it's because the air in the balloon is going towards us. And the balloon itself is moving in the opposite direction. It's very similar to a rocket.

BARBER: So, Em, here's another example. So in physics 101, I used to do this demo when I teach in university, and I would sit on my knees on this, like, plank thing with wheels that mechanics use to go under cars.

KWONG: Uh-huh.

BARBER: And I would put a fire extinguisher between my knees. And I would, like, let it rip, and then it would shoot me backwards as it fired.

KWONG: That sounds so fun.

BARBER: Yeah, so, basically, the rocket has mass. It has fuel. And by this law, the Newton's third law, the fuel goes out. And that's what's known as exhaust. And it generates power, known as thrust. And we go up.

KWONG: In 5, 4--

EMILY & REGINA: EMILY & REGINA: --3 2, 1, lift off!

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KWONG: Gina, escaping Earth's gravitational pull is not easy, right?

BARBER: No, this is not easy. We're overcoming the curvature of spacetime itself. Like, just a reminder, the fabric of our universe, spacetime, can be thought of as, like, a bendable sheet. The mass of Earth is making that flat fabric of spacetime curve down into this, like, funnel-like shape. Moving up the funnel, escaping Earth's gravity is more difficult than moving down. So we need to go really fast.

JAH: You need to have enough velocity to be able to no longer succumb to the curvature of spacetime based on the Earth's presence.

BARBER: And as all this is happening, the people inside the spaceship are experiencing intense g-forces, Em.

KWONG: Ah.

BARBER: So gravitational forces, or g-forces, come when your body experiences acceleration. So when you're sitting or walking around on Earth, you're probably not noticing them, even though you're always getting this pull towards the center of Earth or Earth's gravity. And that's 1 G. When you're doing something like going up in an elevator, like, really fast, you feel heavier, and that's more than your regular 1 G. But it's nothing compared to like what astronauts experience during launch, like Captain Wendy.

LAWRENCE: I remember on my first flight, thinking, oh, my gosh, somebody just sat down on my chest. This was an incredibly heavy sensation. Then I tried to see if I could put my arm out in front of me, just extend my arm. And I'm like, no, I cannot hold it out there against this tremendous power and acceleration being produced by this amazing space vehicle.

BARBER: The g-forces Wendy experienced were so intense because the acceleration she was feeling was actually three times the gravity we feel on Earth. And of course, like, once the rocket reaches space almost nine minutes later, she feels almost weightless. Wendy says that once she got past that uncoordinated stage of floating--

LAWRENCE: It's just awesome. You're just perfectly suspended right in the middle of the air. And what's really fun about it is it doesn't take any effort on the part of your muscles or your body to maintain position. You just relax in front of a window and watch the world go by.

BARBER: Something that's actually really cool to me about weightlessness is it feels like you're floating-- and astronauts kind of are when they're in the International Space Station-- but in physics terms, you're actually very slowly falling towards Earth.

KWONG: You're falling.

BARBER: Yes.

KWONG: That's so bizarre. Do you feel like you're falling?

BARBER: Yeah, I asked Wendy that. And she said for her, personally--

LAWRENCE: No, I've never had that falling sensation. And sometimes you'll hear people who have had the opportunity to go out and do a spacewalk. They'll get that sensation when they first open the outer hatch of the airlock and now are typically looking down at planet Earth.

BARBER: Em, so I don't know if you know this, but you can actually experience this feeling here on Earth. Have you ever gone to the Tower of Terror in Disneyland?

KWONG: Actually, a lot. I love that ride.

BARBER: Awesome. So you feel weightless for a bit when it drops, right?

KWONG: Yes, you kind of hover in the air.

BARBER: Even though you're falling.

KWONG: Oh, right.

BARBER: Right.

KWONG: What? I don't get it.

BARBER: In physics, we call that freefall. All the astronauts--

KWONG: Oh.

BARBER: --in the ISS orbiting the Earth are just falling. That's why they feel weightless.

KWONG: Wait, so how are they falling, but still orbiting?

BARBER: Yeah.

KWONG: Like horizontal and vertical motion?

BARBER: Right.

KWONG: I don't get it.

BARBER: Well, it all starts with projectile motion. Here's Wendy again.

LAWRENCE: I think pretty much every kid has thrown a ball. Gravity pulls it eventually back down to Earth. So you know that ball kind of has an arc shape as it travels. So in general, that's happening to my spacecraft. It literally is falling back to Earth.

KWONG: I think I get it. But wait, can you explain this some more?

BARBER: Yes, Isaac Newton-- you know, the guy we've been talking about?

KWONG: That dude, yeah.

BARBER: He had this thought experiment that if you were to shoot a cannonball, let's say, like, horizontally, that that ball will first travel pretty flat horizontally, and then it'll start to fall in that curved path. Now, imagine that we're doing this on a very, very tall mountain. And the ball would hit the ground even farther away because it had farther to fall, and it would have been in the air longer.

KWONG: The arc would have been bigger.

BARBER: Yeah, the arc would have been bigger, longer. Now imagine you could shoot the cannonball even faster. It would travel even farther.

KWONG: I can see this in my mind. Like, the arc is just getting bigger and bigger and more stretched.

BARBER: Right, right. So now imagine that the mountain was so high and the launch was so strong that the cannonball, when you shot it out, the curved path matched the curvature of Earth so that it never falls and never hits the ground.

KWONG: It's just-- so it never falls and never hits the ground? Like, it just keeps missing the planet?

BARBER: Yeah, now you're in orbit.

KWONG: No, that's all it is?

BARBER: Yeah, that's all it is, projectile motion.

KWONG: That is so cool. Gina, thank you for explaining this to me. There is one thing that-- or I really should say, thousands of things that are just not so awe inspiring about getting to the International Space Station these days. And that is all the stuff that is starting to clog up low Earth orbit. You know about this, right, Gina?

BARBER: Yep.

KWONG: Yeah, we call it space junk. And looking into it for this episode, it reminded me a lot of that scene in WALL-E. Do you know the one I'm talking about?

BARBER: I do. I love WALL-E.

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KWONG: Where Wall-E and Eve had to, like, cut through a cluster of satellites to get off the planet. Right now, you know, that debris isn't as close. But yeah, there is debris out there.

BARBER: Yeah, like low Earth orbit is just becoming a little bit of a junkyard for orbital debris. It's generated from these satellite collisions and stuff just breaking down and falling apart.

LAWRENCE: Even a fleck of paint off an old satellite can do damage because we're talking about a tremendous rate of speed to stay in orbit. The Space Station right now is probably also about 250 miles above the Earth's surface. It's going 5 miles a second, 8 kilometers a second, to stay in orbit. Same with the orbital debris. So it doesn't have to have a high amount of mass to do a lot of damage.

KWONG: So that's why the Space Station has to monitor for space junk all the time. Moriba Jah, our astrodynamicist from earlier, says space junk is an escalating environmental issue, and we're on kind of a dangerous trajectory. Think about single use plastic and the danger it poses to the environment here on Earth.

JAH: But that's what we're doing in space because nothing that we launch into space is this reusable thing, except for maybe the Space Station.

KWONG: Yeah, the ISS, Gina, did you know it has to monitor for space junk to avoid a collision?

BARBER: I do. I did know that, yeah.

KWONG: It's, like, part of the gig. And when I spoke to Moriba five years ago, there were about 20,000 objects that the US Department of Defense was tracking, like satellites, rocket bodies, debris. Most of it, 90% of it, is just trash. Like, it doesn't work. Now the catalog has grown to over 45,000 objects.

BARBER: Wow. That's a huge jump.

KWONG: Yeah, and it has to do with this trend, OK? In the last few years, commercial entities have launched thousands of satellites. Like, SpaceX alone has launched 6,000 of the over 9,000 working satellites to create the internet network Starlink.

BARBER: Right.

KWONG: And Moriba, he supports a global internet, you know, giving people access in remote locations, but he's worried about these unforeseen costs to our environment.

BARBER: OK, you're really making me think very differently about launch. Like, once stuff is up there, like, what happens to it?

KWONG: This is the question for our age. I mean, there is no international treaty that, say, limits space junk or sets standards for negligence if a country creates more. Moriba wants to see space become a much more sustainable place.

JAH: Countries, governments need to incentivize their industry to say, you're going to get some kind of incentive or tax cut or whatever if you design, build, and operate reusable and recyclable satellites.

KWONG: And he thinks those same parties need to be held accountable for responsible disposal. But until that future comes to pass, we're going to see more launches, but also more space junk littering the sky.

BARBER: Oh, well, let's not contribute to the stuff in orbit right now. And let's move on to Pluto.

KWONG: I like how you think, Regina Barber. We will be back tomorrow with more regular Short Wave. But you don't want to miss this series. Every Tuesday, tune in to our next installment of Space Camp.

BARBER: Yeah, Tuesday, we will continue our exploration of the universe with a push deeper into space. So, Em, I have this clip ahead of our next Space Camp episode, reporting on something at the edge of our solar system. I have this, like, message from one of our experts.

WLADIMIR LYRA: This is Wladimir Lyra, your planetary officer here on Earth. This is ground control to Major Tom. You're about to pass Pluto after a long, cold journey. Say hello to Pluto and getting to know you close up and personal. Look at the other side, and you see the Crescent of Charon. I bet the stars look very different today.

BARBER: And before we head out, we want to hear from you. We want you to send us your favorite planet in a voice memo in 20 seconds or less. Say what your favorite planet is, why you love it, your name and location, and email it to shortwave@npr.org. And we may feature your voice in an upcoming episode.

KWONG: This episode was produced by Berly McCoy. It was edited by our show runner, Rebecca Ramirez, and fact-checked by me and Gina. The audio engineer was Gilly Moon, who is not from space, but is awesome.

BARBER: Julia Carney is our project manager. Beth Donovan is our senior director, and Collin Campbell is our senior vice president of podcasting strategy. I'm Regina Barber.

KWONG: And I'm Emily Kwong. Thank you for listening to Space Camp, a science summer series from NPR.

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BARBER: A space science summer series--

KWONG: The science--

BARBER: So many S's.

KWONG: Yes.

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KWONG: The science summer series.

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KWONG: A special space science summer series--

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KWONG: --from NPR.

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