How Impulse Space’s Helios will democratize access to Earth’s farthest orbits

Danny Crichton:
Well, Tom, thank you so much for joining us. And I have to tell you, you relayed to me a story that happened a little bit over Christmas, so give me a little bit of context here. So, over Christmas we had a satellite in orbit, something called a CubeSat, so a standard sized, cubic-oriented satellite in orbit, and it got out of where it was supposed to be, and apparently that's not good in space.

Tom Mueller:
No, I think it was in its orbit. It was dead. So, it had lived past its life or whatever. It was a 3U, I believe, which is about the size of a small loaf of bread. But it was a dead CubeSat in retrograde orbit. Air Force warned us about it, once we got the warning and looked at it, and they said, "Yes, there's a conjunction." So, within 24 hours of telling us that there is a conjunction, that the two are coming together with some small probability of collision, we commanded a propulsion system to move us. And because we're many hours difference it doesn't take very much, just a little bit of a tweak, a few centimeters, 10 centimeters per second this way, and then you miss. I think it's kind of standard stuff.

Danny Crichton:
When I think about space, everything is much faster. We have this concept of, on Earth we're going 50 miles an hour. In an aircraft we're going a couple hundred miles per hour. But in space we're talking about 15 kilometers per second when we're having two objects coming straight at each other, or seven and a half when they're going in orbit. And so everything is happening so quickly, and so maneuverability becomes this precision game in a way that, if you have a steering wheel of a car, we're not going very fast. We can drive. We can go on circles. We can go on a corner. What is it like to do navigation though in space and to move these objects in place? Because that's really what's impulse space is focused on.

Tom Mueller:
Luckily space is big. So, even though you're going very fast, there's usually lots of time to maneuver. I think the perception of the speeds in space is, people don't have a good feeling for it. If you watch the show The Expanse, one of the things I would critique about the show, they had that... It was this giant space station. I think it was a LDS, a Latter Day Saints station, going towards an asteroid. And they showed it. It was doing 26 kilometers per second. Relative to what? But anyway, it said, "Closing at 26 kilometers per second." And it goes by. You see it coming up and it's like doing 200 miles an hour past the asteroid. I go, "Wait, no, it would be 26 kilometers away, so it'd be a dot and then it would be gone." So, I was critiquing. I'd go, "No, wait, that thing is not doing 26 kilometers per... It's not doing space speeds."

Danny Crichton:
It's funny, first of all, because the last episode of our podcast, we had a good endorsement of The Expanse.

Tom Mueller:
It's really cool, but they miss some things.

Danny Crichton:
Yes. It's a really good show, so it's interesting to get the different views. And one of the things, when we think about... You were one of the founding members of SpaceX. You left, building up Impulse Space, and you're really focused on propulsion systems. Why did that become the next challenge? Because I think from my popular perception of this, it was just like, how do we get stuff into orbit? And now we have a whole new set of problems, which is, well, we have a lot of stuff in orbit now. What's the next challenges that come with that?

Tom Mueller:
Challenges and opportunities. The opportunity is space debris removal, which we would love to help with that. Of course, the challenge is, there's so many things up there that space traffic control is more important.

Danny Crichton:
And when you think about Mira, so this was your first product, maybe describe what it does and why it matters in that context of low Earth orbit.

Tom Mueller:
So, Mira is basically our LEO, what we call our last mile transport. So, it's designed to go up on Falcon 9 transporter and pretty much optimize the amount of payload that we can carry and be able to move to other orbits. Because think about transporter as like a cargo ship coming into a port, the port being the orbit it goes to. And people want to be at different orbits. So, what we do is we can take a bunch of CubeSats or a small sat on Mira and move to other orbits, like higher or lower orbits.

Danny Crichton:
And the benefit here obviously is avoiding collisions and trying to reduce the risk of space junk. Because as these satellites potentially hit, not only do you lose those satellites, but all of the destructive material that comes out of those satellites suddenly goes in all kinds of different directions, and that can mess up the orbits for a lot of other things at the same time.

Tom Mueller:
Yeah, that's the cascading effect. The Kessler syndrome is that if they have two big satellites hit each other, now you have millions of small objects. So, it's bad.

Danny Crichton:
And for those who watched, what was it, Gravity, I think was the movie from '10 or '11, and one thing leads to the next and everything blows up, and one CubeSat leads to this Kessler cascade. I'm curious, when you think about the situation today, thousands of things in low Earth orbit, what is the risk of a Kessler effect? Is that real? Is that something that you are concerned about? Does Mira help with the ability to reposition either the debris that's trying to come down back to Earth or just making sure things stay in good position?

Tom Mueller:
I believe somebody said, I've never confirmed it, but I think I read somewhere that Kessler effect is already in place. If we just leave it alone right now, there'll be enough collisions in the future that it'll eventually become a problem. I think that we need to remove some of these big objects before they start hitting each other. Eventually they will. It's kind of like the asteroids hit the Earth thing every 60 million years. Well, big stages left up at 900,000 year orbits are eventually going to hit each other and then there're going to be a shotgun effect where they hit others, and it's a Kessler effect.
Whether there's enough up there right now to do that. Certainly the Kuipers and the Starlinks and stuff that take care of themselves, I don't think are that problem. I think the things that are dead or uncontrolled up there will be the problem in the long run. But definitely Impulse wants to be a good steward, so we want to remove our junk from causing these effects. We would love to go up and be the guys to help remove debris. I think that's our model, is to move things in space, bring things back.

Danny Crichton:
What does bringing something back mean? Because when we talk about space junk, you're not bringing it literally all the way down to the ground beautifully and we all walk out with the object off the launch pad, so to speak. What does it mean to try to get something out the way and out of that highway up there?

Tom Mueller:
If you want to get something out of the way that's likely not demisable, that means dropping it over Point Nemo, which is the center of the South Pacific. That means not using EP to do that. Not use electric propulsion, because electric propulsion can bring things down, but it brings it down very slowly and then you can't control where it comes in. That's the nice thing about chemical propulsion. With high thrust, you can actually do a reentry burn and target bringing it in. And that's something that we're going to demonstrate with our Mira that's up there right now, is a reentry type scenario.
If you want a really tight targeted reentry, like say over a space on Earth, you typically want to get pretty elliptical, like high on the apogee side and low on the perigee. And then at apogee, do a pretty big burn so it comes in with some angle of attack through the atmosphere. It doesn't want to skip and have a large dispersion, so you try to bring it in pretty steep. So, that's another trick that we could show, bring it in steep. It targets exactly where you want to land, a small landing ellipse.

Danny Crichton:
So, let's bounce ahead. So, obviously there's been a lot of attention on low Earth orbit. That's where the constellations are going for Kuiper and for Starlink. That's gotten a lot of press attention, but there are a lot of different orbits out there. There's middle Earth orbit. There's geostationary orbit, that are farther and farther away from the planet. It's one thing to get things up a hundred kilometers above the Earth. It's another thing as you're going to thousands of kilometers and tens of thousand, just a totally different challenge. What is the interest in getting to those later orbits? What can you do there that you can't do at lower Earth orbit?

Tom Mueller:
Well, geostationary orbit is probably one of the most important orbits. It's a 24-hour orbit at the equator, which means that, relative to the surface of the Earth, you're stationary in space. So, that's where you point your DirecTV dish, is that geostationary satellite. And there's only a certain amount of them. If you're half a degree, that's 720 slots that are available. So, it's a limited number of spacecraft that can go there.

Danny Crichton:
How do things get there today? How do we get things out all the way tens of thousands of kilometers out from Earth?

Tom Mueller:
There's two ways right now to do it. You can do it on a lower cost rocket, and I'll use SpaceX as an example since that was the company that I was a co-founder of. You can use single stick Falcon 9, which doesn't have very much payload capability directly to GEO, but it has good eight tons to GTO, geosynchronous transfer orbit, which is a single burn, highly elliptical still at the orbital inclination of the cave at 28 degrees. And then the spacecraft, using either chemical propulsion or these days more likely electric propulsion, will round out that orbit and take out the 28 and a half degrees of inclination to take it from GTO, geosynchronous transfer, to geostationary. And then the other way is to buy a very highly capable rocket like Falcon Heavy or like Vulcan, which just flew yesterday for the first time. And those can go directly to GEO, but now you're talking about a much more expensive launch vehicle.

Danny Crichton:
And so one of the big considerations here is not just the technology side, but the cost of actually delivering those payloads out into geostationary orbit.

Tom Mueller:
That is actually the main purpose of Impulse, is to lower the cost of access to the high energy orbits.

Danny Crichton:
And so when you think of the work at SpaceX, obviously that was part of getting launch vehicles, getting the stuff into orbit, most of that into LEO. You have an announcement of a new propulsion technology that you're focused on to take objects from geostationary orbit. Why don't we talk a little bit about that?

Tom Mueller:
Yeah. It's called Helios. We talked about it a little bit last year, but now we're coming out with the more detailed specification of it. It's basically a kick stage, which means it would act like a third stage on a typical medium lift rocket like on a Falcon 9. And it can take 5,000 kilograms, five tons, from LEO, from lower Earth orbit, directly to geostationary in a day. It's two burns and you're there. The first burn's a typical GTO burn, and the second burn is the one that rounds out the orbit and takes out the inclination.

Danny Crichton:
And when you think about comparing that to the two models you were just talking about earlier, where's the game for Helios?

Tom Mueller:
When you do a Falcon Heavy, you basically throw away the center core. Because it's going so fast that it can't be recovered without losing most of your payload advantage. So, they throw away the center core of Heavy, which you're throwing away a large rocket core with nine engines. So, Helios is also an expendable. Now you're talking about throwing away a small stage with a small engine, so the cost is much less. So, you get two-thirds of the GEO capability of Heavy at a much lower cost, actually 80%. Being able to throw five tons rather than eight tons to GEO.

Danny Crichton:
And part of the gain here is you're connecting the cost savings, from my understanding, the cost savings of going from Earth to LEO. And then Helios kicks in says, "Well, now we can save costs LEO to GEO," which means altogether the cost of getting those satellites all the way out tens of thousands of kilometers from Earth is exponentially cheaper than it was even a couple of years ago.

Tom Mueller:
I don't know about exponentially. To me that means a lot. That means orders of magnitude, but-

Danny Crichton:
A lot. That's a lot.

Tom Mueller:
Yeah, like fractionally. Yes. Like possibly cutting the cost in half. And the real economics come into play when Starship is flying commercially. We could fly, say, three of these at a time on Starship. Or our whole stack with the satellite and the propellant and the stage would be less than 20 tons. Starship could throw over 100 tons. So, we could fly as a secondary, basically as a ride share, on Starship. If Starship's flying to LEO, it's like, "Hey, you got room for another 20 tons?" And if that's only $10 million or something, now you talk about very low cost of access to GEO with Helios.

Danny Crichton:
And then the core of the technology for Helios is this engine which you've dubbed DNEB. Why don't we talk a little bit about how you developed this, because I think obviously there's a lot of different components that go into this, but the engine to me is the centerpiece of all of what Impulse Space is building. What went into building this engine as you're designing it?

Tom Mueller:
It's probably one of the highest performing, highest pressure space engines I've developed. You don't need to have very high combustion pressure in space because you're expanding the vacuum. So, you can have a large nozzle even if you have low pressure in your combustion chamber, but that makes the engine big. So, we're trying to find the right place where it's not crazy high pressure where it's really difficult to develop the [inaudible 00:13:07] pumps in the system, but high enough that the engines shrunk. So, there's some optimization to come up with a intermediate chamber pressure, combustion pressure, that keeps the pumps happy, where you're not very stressed on pumping the repellents into the combustion chamber at super high pressure, but you can keep the whole engine small and light because that's high pressure. That's one of the things. We're using stage combustion, which means it's closed cycle, so all the propellant goes through the main nozzle, so you get very high performance.

Danny Crichton:
And that's great. And so this is Helios. And so what's the timeline? So, you're doing the announcement today when this episode is published. What's the next steps to get that into production and into space?

Tom Mueller:
So, we're developing an engine right now. We've got our 3D metal printer out here printing parts for the engine. We're getting our test site ready out at Mojave. Start testing here this spring, be running the engine before summer, and first flight of the vehicle is in early '26.

Danny Crichton:
Well, you're just like, to analogize the Starship captain, "Get us into geostationary orbit." And I guess that's what you're doing with Impulse Space.

Tom Mueller:
Yeah.

Danny Crichton:
So, Tom, thank you so much for joining the podcast today.

Tom Mueller:
You bet. It was fun.

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