Could ‘SpaceSAF’ Enable a Sustainable Future for Spaceflight?

Efforts to promote the switch to SAF have largely focused on the commercial aviation sector. But one Utah-based firm is looking at a different kind of aviation: spaceflight.

CleanJoule, a SAF producer backed by Texas’ Frontier Airlines, Europe’s Wizz Air, private equity firm Indigo Partners, and others, on Tuesday introduced what it bills as a “drop-in,” 100 percent SAF replacement for Rocket Propellant 1 (RP-1) called SpaceSAF. RP-1 is the fuel of choice for many first-stage rockets and boosters such as SpaceX’s Falcon 9 and Falcon Heavy, Rocket Lab’s Electron, and Astra’s Rocket 4.

“We hope everybody who uses RP-1 currently moves over to our stuff,” Mukund Karanjikar, founder and CEO of CleanJoule, told FLYING.

According to CleanJoule, SpaceSAF is designed to reduce spaceflight emissions while delivering a 4 percent improvement in energy density versus petroleum-derived fuels. It will be offered in liquid, solid, and hybrid forms for both civilian and military spacecraft.

The company will also offer a sustainable solid rocket fuel (SSRF) solution for solid rocket motors, such as those in use by the European Space Agency’s Vega and Vega-C, Virgin Galactic’s VSS Unity, and United Launch Alliance’s Atlas V. The fuel is derived from the same feedstocks—biomass, such as waste residue from agricultural or forestry activities—that CleanJoule uses to create SpaceSAF.

According to Karanjikar, CleanJoule first began developing SAF in 2012. But its focus, like others in the industry, was on commercial aviation.

“The question we had asked ourselves was something very specific, which is, if we want to accomplish total decarbonization of the aviation sector—including the long haul piece of it, which is the most important one and hardest to decarbonize—what should it look like?” he said.

Under current regulations, SAF must be blended with conventional fuel, like Jet A, up to a limit of 50 percent depending on the feedstock and production method used. In other words, SAF is only permitted to make up half of an aircraft’s fuel supply.

“So the math doesn't work,” Karanjikar said. “Forget about the physics of decarbonization. With 50 percent Jet A, you can never get to 65 percent [SAF] decarbonization contributions. However, our objective has always been, how do you develop full-performance SAFs that then do not need to be blended with petroleum-based Jet A?”

CleanJoule wants to shake up this paradigm by developing SAF from a type of hydrocarbon called cycloparaffins, using waste biomass as the feedstock. With this method, Karanjikar said, CleanJoule’s CycloSAF can achieve the density required to be considered jet fuel without being blended with Jet A. Most SAF producers, he said, get stuck at a lower density and must add higher-density Jet A to balance it out.

“Because we targeted high density hydrocarbons from the get go, they carry 10 percent higher energy content per unit volume,” Karanjikar said. “So you can fill up the tank to the same level and go 10 percent farther on our SAF versus other people’s SAF, or Jet A for that matter.”

ASTM International, which regulates SAF standards worldwide, will need to create a 100 percent SAF index before any commercial flights using CycloSAF can be approved, CleanJoule told FLYING in an email. But the firm said it is working with several airlines and original equipment manufacturers (OEMs) to conduct 100 percent SAF testing.

Compared to the tens of billions of gallons of fuel consumed annually by the aviation industry, spaceflight operations are a drop in the bucket. But with the development of reusable rockets like SpaceX’s Falcon 9 and Falcon Heavy, space launch cadence is increasing, and environmental groups already have concerns about what that means for life on Earth.

Karanjikar believes it would be counterproductive to expect space launch companies to also tackle a worldwide issue like global warming.

“[These companies] are doing their job of exploring the universe. It is for people like us to make that exploration far more sustainable, because one company can only do so many things,” he said. “We demand a lot from our space aviators, including from agencies like NASA. We can't hope and expect them to solve all the global problems. That's where companies like CleanJoule come into play.”

Using the same feedstocks and production method as CycloSAF, CleanJoule created SpaceSAF as a replacement for RP-1, which according to Karanjikar is actually quite similar to Jet A.

RP-1 and its cousin RP-2 are kerosene-based propulsion fuels typically used to launch first stage rockets. SpaceX’s Merlin engines, which power the company’s prolific Falcon 9 and Falcon Heavy rockets, run on liquid oxygen and RP-1, for example.

“Right as you take off, the big burning you see at the bottom—that's kerosene and [liquid] oxygen mixed,” Karanjikar said.

Some commercial space companies, including SpaceX, Blue Origin, and Rocket Lab, are developing methane- or hydrogen-based RP-1 alternatives. But the bulk of space business is conducted using the kerosene-based propellant.

SpaceSAF, which has largely the same composition as CycloSAF but is put through a modified refining process, is a direct replacement for RP-1 and RP-2. “The pumps, the tubes, whatever you fill up, the way it burns, all of that” will be identical, Karanjikar said. But SpaceSAF, by his estimate, offers 4 percent higher energy density than RP-1.

“It's a positive snowball that happens after that,” Karanjikar said.

Higher energy density means a rocket can get more range out of the same volume of fuel, allowing for extended flights. Alternatively, a launch provider could reduce the fuel load and use the extra capacity for actual cargo. Either way, SpaceSAF could allow operators to get more out of their missions.

“But it's one thing to say, ‘Here are the superior properties’—it's almost like the model during New York Fashion Week walking with whoever's gown or suit that needs to be showcased for the next year,” Karanjikar said. “It's another thing to walk into a clothing store and be able to buy it.”

The CleanJoule CEO said the firm is working with one unnamed private company to conduct static engine testing with SpaceSAF. In reduced scale engine testing, the company said, the solution reduced the formation of environmentally harmful particulate matter by 86 percent.

Full-scale engine testing with partners, including a major engine OEM, airframer and university, is scheduled for 2025. Within the next quarter, Karanjikar said, the company expects to share engine test data and the chemical characteristics of SpaceSAF with potential customers.

Those could include SpaceX, Rocket Lab, Astra, Firefly Aerospace, United Launch Alliance, Virgin Galactic, and just about any company launching first-stage rockets today, he said.

“Now, SpaceX and other rocket service providers have options, whether they want to buy petroleum-derived RP-1 or they want to fly with our SAF that would be fully sustainable,” Karanjikar told FLYING. “We help them address both the exploration and sustainability at the same time.”

Like this story? We think you'll also like the Future of FLYING newsletter sent every Thursday afternoon. Sign up now.