Former SpaceX Engineer Disrupting the Industry Again

To those familiar with the history of SpaceX and the development of the Falcon rockets, whether from the book or other sources, one name will be closest to being thought of as the Father of the Merlin engines, Tom Mueller.  As much as SpaceX and the Merlin have revolutionized space travel and pushed every other launch provider into "copy or die" mode, Mueller doesn't get the recognition he deserves.  

Mueller left the company some years ago and has quietly been positioning a new company to disrupt the space industry again.  The company is Impulse Space and the product is an orbital transfer stage called Helios.  An orbital transfer stage is often referred to as a "tug" - as in tugboat - and they're in fairly wide usage.  Rocket Lab, for example, has their version, called Photon, which is essentially a strap on module for a payload that slowly and gradually accelerates the payload until it can make the desired trajectory.  There are others from various companies such as D-Orbit, Momentus, Launcher, Spaceflight Inc., and several others, generally designed for satellites with a mass of a few dozen to a few hundred kilograms.  What has been missing is a tug for larger payloads capable of carrying them to higher orbits or escape velocity. 

That's the market segment Helios is aimed at. 

With a diameter of just under 5 meters, Helios is sized to fit within a Falcon 9 fairing. According to Impulse Space founder and chief executive Tom Mueller, the basic idea is to allow the low-cost Falcon 9 rocket to launch large satellites directly into geostationary space.

"We're basically adding a third stage to a medium launch vehicle," he said. "It's basically doing most of what a Falcon Heavy will do for much less money, and without throwing away a core."

Artist's concept of the Helios upper stage.  Impulse Space image. 

Despite the mention of the Falcon 9 fairing, Mueller says they're aiming the upper stage to be usable on a variety of vehicles.  For example, Helios is intended to propel up to 4 tons launched on a Falcon 9 or 5 tons on Relativity's Terran R vehicle directly into geostationary orbit.

This seems to be a potent offer to groups with a large payload to put in orbit.  

At present, for medium and large satellites, there are two ways to reach geostationary orbit directly. A customer can buy a launch on a Falcon Heavy or United Launch Alliance's Vulcan rocket, which is fairly expensive, likely about double the cost of a single Falcon 9 launch. Or a satellite can launch on a medium-lift vehicle and go into a transfer orbit to geostationary space, necessitating a robust on-board propulsion system, up to $5 million in Xenon or other propellant, and six to eight months of lost revenue during the ride up.  "We're offering to get there in a day, for a much lower cost than either of those," Mueller said.

In keeping with a group led by the "Father of the Merlin Engine," the Helios upper stage will be powered by an engine more akin to the SpaceX Raptor or smaller Blue Engine BE-3 engines in being a methane/oxygen based system.  While much lower in thrust than the Raptors...

Helios will be powered by one of the most robust in-space engines ever built, named Deneb. It is on par with the venerable RL-10 engine manufactured by Aerojet and will have a thrust of 15,000 pounds (67 kN), and be powered by liquid oxygen and liquid methane. The fuel choice is partly a nod to the reusable future of spaceflight that Impulse Space hopes to tap into. "SpaceX needs 1,000 [metric] tons to refuel Starship," he said. "Just give us a sip. We'll take our 14 tons, and we'll be glad to pay for it. And we can continue to reuse these."

No, the Helios isn't flying now nor will it fly this year, but they're targeting launch in 2026.  Impulse Space, though, has put a smaller prototype of the concept in orbit already, last year.  

... Designated Mira, the spacecraft has performed well on its debut mission LEO Express 1. After it deployed a few small satellites, Impulse has been putting Mira's propulsion system through its paces. This vehicle will compete with other spacecraft to provide last-mile services for small satellites, and it has also given Impulse confidence in its plans for Helios.

Image credit:  Impulse Space

Final words to Eric Berger at Ars Technica in the source article:

Now operating with about 90 employees, Mueller intends for Impulse to build upon the success of SpaceX. That launch company is well on its way to solving the problem of low-cost access to space with the Falcon 9 rocket now, and Starship in the near future. Impulse Space seeks to join other commercial space companies leveraging that capability by building spacecraft that can do new, interesting, and sustainable things in space.