We ask NASA's Jay Hollenbeck about the Space Launch System, a new rocket. 

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ERIC: From the Museum of Science in Boston, this is Pulsar, a podcast where we boldly go in search of answers to the most powerful questions we get asked from our visitors. I'm your host, Eric. And a theme we've seen in this podcast is that people want to know about the extremes. When we do a weather presentation, we get asked about the biggest hurricane in history. On stage with animals, we get asked what was the oldest one that ever lived? And whenever we livestream a rocket launch, we inevitably get asked: what's the most powerful rocket of all time? For 54 years, the answer to that question has been the Saturn V, which launched humans to the moon in the 1960s and 70s. No other rocket has come close to matching its ability to overcome the pull of Earth's gravity...until now. In March of 2022, the Space Launch System rolled out from NASA's VAB, or, Vehicle Assembly Building, for launch pad testing. As tall as a medium-sized skyscraper, this rocket will be able to carry more to space than any before it when it launches later this year. Joining me to talk about just how powerful this new title holder is going to be is Jay Hollenbeck from NASA's Marshall Space Flight Center. Jay, thanks so much for calling into Pulsar from Alabama.

JAY: Hey thanks Eric, thanks for having me.

ERIC: Now, we want to talk about how powerful this rocket is. And that's usually measured in pounds of thrust. The very first rockets had about 200,000 pounds of thrust, the Saturn V had over 8 million. What's the number for SLS?

JAY: We have 8.8 million pounds of thrust. That's about 1.6 million pounds of thrust from our core stage, which includes for shuttle heritage RS-25 engines. And then our real thrust comes from our two five-segment shuttle heritage boosters which equate to 7.2 million pounds of thrust. So a total of 8.8 millions of pounds of thrust that are going to get us into space.

ERIC: So rocket engines left over from the space shuttles dusting them off and using them in this new program.

JAY: Yeah, we had about 16 shuttle heritage RS-25s leftover and so we're gonna put those to good use for the next four missions.

ERIC: And the SLS is so tall that you have to assemble it inside of the VAB, NASA's Vehicle Assembly Building, one of the largest buildings in the world. Just how tall is the rocket?

JAY: So the fully integrated rocket, as it stands, is 322 feet tall. And just to kind of put that into perspective, we kind of always use the Statue of Liberty in New York City as a good comparison. The Statue of Liberty is 305 feet tall. So we're about 17 feet taller than the Statue of Liberty.

ERIC: Okay, that's super tall. What's it like to stand next to a rocket that size?

JAY: I got the chance to see it for the first time last week at the cape, right before the first wet dress rehearsal and I was just, I mean, I was in awe when I saw it in the VAB when we're stacking it, but when you see it out there on the on the mobile launcher it's just, I mean, it's definitely a wonder of the world. Definitely gives you goosebumps. So it's cool as the rocket's sitting there on the pad, the thermal protection system or the orange part of the rocket, you know, the part that it's kind of like its signature, is slowly getting tanner. It's getting its Florida tan as it's sitting there on the pad.

ERIC: Now we get asked this all the time as well, how fast can the SLS go?

JAY: It's amazing, the SLS, when fully loaded, weighs almost 6 million pounds with cryogenics and all the components, but this thing reaches a max speed of 24,500 miles per hour. It's insane that you can get that much weight to go that fast.

ERIC: So it's fast, it's powerful. But most importantly, it's going to be able to carry a lot to space. So just how much can the SLS lift to orbit?

JAY: This first block configuration of the rocket is going to be able to carry 27 tons which is about 54,000 pounds, which equates to about 12 elephants. I love equating it to things you can physically see, and that's, yeah, 12 elephants.

ERIC: Okay, even for the most powerful rocket of all time, that's a lot of elephants. Now, we already have big plans for this rocket: the Artemis program, which will send astronauts back to the moon for the first time in 50 years. Can you talk about the role of SLS in getting us back to the lunar surface?

JAY: With the SLS being as big as it is, we're going to be able to carry large payloads. For example, Gateway is going to be kind of like the space station around the moon. We'll get to carry components for that, we'll get to carry components that will end up being used as in situ resources on the lunar surface. And ultimately, it's going to be that transportation, that stable transportation component that's gonna be able to carry and transport these resources and be able to put them in place where we need them. So ultimately the moon is going to be a proving ground, humans are still learning to live in space. So we've been doing it for over 20 years on the ISS. And we still continue to create, you know, that data for humans being in space. And then eventually, once we go on to the lunar surface and start learning how to really live remotely in space and self-sustaining, we'll be able to take those lessons learned and apply them to Mars. And again, SLS is the rocket that's going to enable all this.

ERIC: It's really exciting. Not that going into the space station isn't exciting, but humans haven't left low Earth orbit in decades now. And that's still space, but it's only a couple hundred miles away. To think that the SLS is going to take humans hundreds of thousandss of miles out to the moon, imminently. Now that it's just about complete, it's awesome.

JAY: Yeah, I'm glad you brought that up. So to put it in perspective, the ISS is only 220 miles above the earth's surface, the moon is roughly a quarter million miles. So you're talking about a thousand times further out that we're going to be able to use this SLS rocket to get us to the lunar surface and beyond, it's definitely a deep space exploration vehicle. And that's what we've built it for, it will eventually evolve to a block 1B configuration with an exploration upper stage, and then eventually, even our boosters will evolve into what we call BOLE. And those are going to be composite wrap cases. And it's going to just increase performance even more. So this rocket, over the course of the years in the Artemis program, is going to evolve to something that's just insanely capable, and will enable that deep space exploration that we crave so much as humans.

ERIC: So it's just gonna keep getting more powerful as we go.

JAY: That's right, this orange rocket will keep getting more powerful.

ERIC: So what is your role in SLS coming to life?

JAY: I'm currently the Deputy Hardware Manager for the Interim Cryogenic Propulsion Stage or ICPS. It's the part of the SLS known as the second stage or the upper stage. My main job for for that second stage is to make sure that we have quality subcomponents that get integrated together, get stacked with the rest of the rocket elements at the Cape in the Vehicle Assembly Building, make sure that it gets tested, and then launches successfully with the entire integrated SLS rocket. The second stage provides the propulsion in space for the Orion crew capsule, which also includes the European Service Module. If you went back in time, you could kind of compare it to the CSM for Apollo.

ERIC: So the part that actually goes out and heads to the moon. The big boosters get the whole thing up into space. And then that second stage is what takes it on its cruise out to the moon.

JAY: That's right. So yeah, we gotta defeat gravity first. You know, Newton would be proud. But once we get out into space after that 8.8 million pounds of thrust, we're the stage that that takes the Orion crew capsule, crew and then any kind of payloads out to translunar injection and ultimately to the lunar orbit. We've got one super, super capable and tried and true Aerojet Rocketdyne RL-10 engine that provides about 24,000 pounds of thrust in space.

ERIC: The first SLS launch is going to be that first Artemis mission. It's Artemis 1. And that's coming up really soon. Can you give us an update on what's been going on? What's the scoop, how's it going right now?

JAY: So recently, you guys probably saw in the media, just a huge event for us to roll that stacked rocket out of the iconic VAB on our crawler down the crawlerway to Pad 39-B. Again, amazing to see one of the new wonders of the world roll out there. But as part of our test like you fly path to the first launch of SLS, we just need to verify the whole integrated rocket can can be safely fueled and controlled. So right now we're going through what we call the Wet Dress Rehearsal or WDR. WDR is sort of like a wedding rehearsal where we not only check out the ground side supplies of the rocket, but also the mobile launcher that's sitting on top of 39-B, but we're really trying to check out the vehicle systems integrated recently to you know, check connectivities, look for leaks. We're also trying to test our software with our Exploration Ground Systems partners down there at the Cape, their responsibility for EGS or Exploration Ground Systems is launching the vehicle. So during this wet dress rehearsal EGS gets learn how the vehicle behaves prior to launch activity. So it's a dry run for them. We've got launch commit criteria, hundreds of those that they're watching as we're filling up this vehicle with super-chilled cryogenic fuel, oxidizer, and then we're going to simulate a countdown so their team even gets to practice, the ones that are sitting on console are going to get to practice a simulated cryogenic load and then a countdown to T-minus 9.34 seconds. And that's the part in the timeline when normally the RS-25 engines would start up. With that we're gonna be able to learn the quirks of this entire integrated vehicle. We've been doing models and data, speculations of what it's going to do, but until you actually put it on the pad, fill it up with cryo, start running all the ground systems, you don't really know how it's gonna behave. This is the first time we've put all it all together and started testing it out. Up until this point, it's all been simulation. And the team has been working really hard with sims and practicing. But now we get to do the real thing. This past Sunday and Monday, I was actually down at Cape with the whole entire team. And we made our first attempts at the WDR, where we did get the core stage LOX tank filled up to about 45% before we did have some ground side issues. Again, first time this rocket has been put on the pad, first time it's been completely filled up with cryo. So we're learning. I mean, it was as simple as some fan issues that we had. Just valves, like a valve go bad groundside or, you know, somebody might have left something open or closed. It's again, just learning and applying those lessons learned to the next attempt.

ERIC: Yeah, that's what the testing is for. You gotta test it before you can fly it. You got to try everything out with so many moving parts because everything has to go right on launch day.

JAY: That's right. That's right. Heck, that's why we test. We're trying to find the quirks of this vehicle. So we know on launch day will be 110% ready to go.

ERIC: That's going to be so exciting, that we could be just a couple of months away from seeing this rocket actually take flight. Seeing it now, off the drawing board and onto the launch pad, has been awesome.

JAY: I think there's gonna be some tears when this thing starts leaving the pad and gets up into space. It's going to be amazing. I can't wait to share it with you guys.

ERIC: Well Jay, good luck with everything. We hope it goes super smoothly. And we will be watching from the Museum of Science when it gets off the ground.

JAY: All right. Well, thank you, Eric. And thank you Museum of Science, Boston. Can't wait for launch day.

ERIC: Final testing and preparations continue for the Space Launch System as of the middle of 2022. Be sure to follow NASA's Artemis blog for the latest updates on the rockets final adjustments and watch along with us at the Museum of Science virtually or in person when SLS finally takes to the stars. Until next time, keep asking questions.

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