Not Exactly to the Moon and Back

Why SpaceX is a story of small steps, not giant leaps

SpaceX went from a small, nearly bankrupt, startup to returning astronauts to space on an American launch vehicle for the first time in a decade. It has done so while driving down the cost of sending payloads to space. It is hard to argue that SpaceX hasn’t been successful. But how credible is the oft-repeated story about Musk’s genius revolutionizing spaceflight?

The Merlin 1D engine featured in SpaceX’s Falcon 9 provides more thrust for its weight than any other rocket engine. Saving on fuel, weight, and therefore money, is part of why SpaceX has achieved lower prices than previous NASA contractors.

Merlin 1D engines…shiny

But SpaceX engineers didn’t create any radically new engine technology to accomplish this. They did it by improving already well known technology. The 1D uses an already well established fuel cycle where rocket grade kerosene (RP-1) is combined with oxygen to create hot gas which propels the rocket. This is how Apollo flew on the Saturn V. 

In the 1990s, NASA and their contractors improved upon this technology as part of the X-34 program, which created the Fastrac Engine. Fastrac itself made small improvements to a few subsystems rather than radically change the design. The Merlin 1D uses the same systems as the Fastrac, and even the same manufacturers for some of the parts. SpaceX engineers made incremental improvements on a project that itself was incremental. A smart strategy, but hardly revolutionary.

Then again, SpaceX seems to have mastered full reusability, something NASA was unable to achieve with the space shuttle. Again, SpaceX engineers made many small improvements to existing technologies to achieve this outcome. They benefited from reusability advances pioneered in NASA’s X-34 program and in the DC-X, including the impressive feat of vertical takeoff and landing. Further aided by improvements in computing technology, SpaceX’s admittedly impressive achievements in full reusability aren’t revolutionary either, but rather build piecemeal upon the innovations of engineers at NASA and elsewhere. 

But the program dearest to Musk’s heart is Starship, the larger launch vehicle he claims will take humans to Mars. In addition to the already mentioned innovations regarding reusability, the key technical feature of the Starship is the Raptor engine.

The Raptor engine uses cryogenic methane rather than the kerosene of the Merlin. The idea for using cryogenic methane has been around since the 1960s. Russia conducted research into it in the 1990s, at the same time that NASA was experimenting with how temperature and pressure affect fuel performance in hydrogen with the X-30. NASA also explored using cryogenic methane fuel for the Orion spacecraft. The idea of using it isn’t exactly novel. 

And the Raptor’s combustion cycle, though it provides massive efficiency benefits, isn't any more dramatic. In most modern cars, the exhaust is pumped back into cylinders in order to burn more of the fuel. This results in a small improvement in fuel efficiency. Scaled up for rocketry, the fuel savings can be massive, but the exhaust is either too sooty if using rocket kerosene, or too hot if using hydrogen to be recirculated as is. SpaceX engineers, however, have been successful in recirculating the exhaust in the Raptor engine.

Although this improvement is extremely important, both Roscosmos and NASA had already tackled the same problem, so SpaceX engineers didn’t have to solve it from scratch. The Soviets, who used rocket kerosene, elected to clean up the exhaust by adding oxidizer to the first cycle so that the burn was more complete. In doing so they increased engine efficiency by 25%, using a technology American engineers at the time thought impossible. The RD-180 engine powering America’s Atlas rockets currently uses this system. 

The space shuttle engines demonstrate the opposite approach. Hydrogen fuel doesn’t have the same soot problem, but the exhaust is far too hot to recirculate. So engineers put extra fuel into the first cycle of the engine, just like adding cool water to a bath that's too hot. Neither of these approaches was perfect, so SpaceX engineers combined them, using both a fuel-rich and oxygen-rich cycle. Still, SpaceX wasn’t the first to try this method. Aerojet and Rocketdyne tested the same system 20 years ago in the joint NASA and Airforce “Integrated Powerhead Demonstrator.” 

The predecessor to SpaceX’s Raptor engine, the IPD engine was tested but never flown

SpaceX engineers haven’t succeeded because of Musk’s brilliant new ideas about spaceflight but by applying the same approach that made Thomas Edison a successful innovator: taking the ideas of others and working to make them more reliable and inexpensive. 

Recognizing that SpaceX’s technologies are not really as novel as they are usually portrayed, doesn’t take away from the incredible hard work by Musk and SpaceX employees. They have worked to continually (and largely successfully) improve upon those designs. Even if NASA is owed much of the credit for pioneering SpaceX’s technology, Musk’s company still succeeded in making it a commercial reality. 

Our point is to bring Musk’s image back to Earth, to humanize him. It is to see that innovation is driven by a large network of people and organizations, a space where their ideas and efforts mutually influence each other and combine to become greater than the sum of their parts. Separating the laudable successes of SpaceX from the hype is essential, once we start thinking about how to more effectively and reliably support innovation in the future. We ought to be wary of what happens when one person’s predilections, genius or not, begin to dominate. And in the next installment, we’ll see what has happened when Musk has had too much influence over the innovation processes within his firms.