An image of the surface of Titan
As you may know, I try to keep my ear to the ground on matters of crewed space flight. I wanted to share with my readers a major development, a paradigm shift, going on right now in space transportation. At the close of the fifties the United States and the Soviet Union were competing with each other to fly higher, faster and farther than any before them. Yuri Gagarin lit the candle when he was the first human being to orbit Earth. But the less well known factoid about space flight has been in it’s irony: lifting objects into low Earth orbit (LEO) was a technological barrier for humanity that was briefly overcome only by sheer bravado and brute force in a way that would never be economical. Rockets were constructed that staged their fuel on the way up, dropped their airframe in pieces like a disintegrating totem pole and reached over 17,000 mph just to place a few hundred pounds into orbit. The truth is, no one really had the technology needed to do this economically. But both the US and the USSR convinced each other of one thing: While it may be a silly waste of money to do such a thing, both of them could place a relatively lightweight nuclear warhead into orbit and pose a threat to the other. Once they proved it, everybody went home. Space flight for the last 50 years has been a stunt that only governments could afford and that only mutually assured destruction could inspire. Unless someone could find a way to reuse these craft, especially the most expensive components, flying to LEO by throwing away all of your hardware on every flight would never make sense in the hard reality of economic necessity.
But reusing these machines was a technological leap beyond Sputnik and Apollo … a big leap. And for that reason space flight floundered for decades. And yes, we’ve all heard what a big waste the Space Shuttle was. But I want to offer a counterpoint that history gives us in 20/20 hindsight. The two most expensive components of rockets, by far, were absolutely dominating all discussion of space flight. Since we couldn’t overcome those two problems mass, yes weight, was the dominating factor in every discussion of space flight. From space probes to deep space to space stations, to the shuttle and to the moon and Mars; weight was the big nasty sea dragon that ensured that talk of frequent missions such as these was hopeless. You can’t go to Mars with a pocketknife and a Bunsen burner, as I like to say, but many proposed it anyway. But the reality was that limitations on weight, borne of the extremely constraining limits placed by the technological limitations that in turn affected the economics, ensured we’d get nowhere. Everything hinged on making LEO economical and loosening the maddening mass restriction that has bedeviled the human space enterprise for some fifty years now. I am happy to report that one of the two technological hurdles needed to overcome this limitation has been cleared and the second is being aggressively run to ground.
The first problem is that rocket engines are powerful; so powerful in fact that they are something like 20 times more powerful than jet engines by either weight or volume. The temperatures at which they operate are in the 6000 degree F range with combustion pressures over 1000 psi. Jet engines come nowhere near being able to handle this. And you need rockets because, frankly, we don’t have any other way to get to LEO. Air breathing hybrids are, contrary to popular myth, decades away (kind of like fusion power), because we still don’t know how to combust a fuel/air mixture over a wide range of speeds in a single scram jet design, for example. The only foreseeable technology is rocket engines. But there’s the rub. We can’t just throw them away on every flight because they are, along with the actual airframe itself, by far the most expensive components of the rocket. And that is what I meant by technological barriers: we threw these expensive things away before not just because we couldn’t carry their weight into orbit, but because our technology was too primitive to build a rocket that didn’t destroy itself after a single flight. Specifically, the key component is called a turbo-pump and in reality, rockets are just pipes and wires built around the turbo-pump. The turbo-pump is the key technology and the really expensive part of the machine. And we didn’t know how to build a turbo-pump that you could keep firing over and over, like driving your car to work every day. Previously, we had to throw them out after every drive, like throwing out your car engine every time you go to the grocery store. This would never be economically sustainable. And it took us nearly 50 years to solve this problem. And that’s where the Space Shuttle comes in.
The Space Shuttle was supposed to be reusable, but as we all know, it never really was. But the one component of the Shuttle that gets little attention is the high pressure turbo-pumps of its RS-25 engine. Over nearly 30 years of operating the Shuttle, and because it was supposed to be reusable, NASA kept tinkering away at the turbo-pumps; flying them, studying them and enhancing them. It took billions of dollars, years of time and thousands of people-hours. But over those years engineers at NASA finally began making headway on the engine that was supposed to be reusable, was a total throwaway, but which was gradually becoming a true, reusable, high powered rocket engine. They figured out how to reduce the temperature and pressure a bit and “Block I” was born. Then they figured out how to handle the massive cavitation and “out of round” motion of the turbo shaft at 37,000 rpm and 85,000 horsepower, calling it “Block II”. They shot-peened the turbine blades to resist Hydrogen wear and used Silicon Nitride as ball bearings, something that took months of jig testing trying all sorts of workarounds to resolve heavy wear on ball bearings and surfaces that was forcing them to either throw the engines out after one flight or overhaul them after every flight. The advantages of this new engine (10 flights before overhaul, an incredible advance) were so impressive NASA set about capitalizing on what it had learned with plans to build a new engine to replace this one, which would have a 100 flight before overhaul (this was to be the RS-83 and RS-84). In other words, for the first time they really knew how to build a truly reusable engine. Of course, by the time Block II came out and they had started on the new engine, the Shuttle was about to retire and the new engine program was cancelled. But NASA is more or less open source and their work and findings spread around the research community. People learned the lessons so hard-earned by NASA. People started building turbo-pumps with Silicon Nitride bearings, used new computer coding models developed by the NASA Shuttle team for dampening (another huge problem) and generally incorporating every lesson they could from NASA’s experience. Numerous papers have been written on this and Aeronautical Engineering professors write almost verbatim from NASA documents extolling the lessons learned. Around 2012 SpaceX tested a totally new turbo-pump. It’s overall thrust is a dramatic increase over its predecessor. The turbo-pumps can be re-fired and the rocket is reusable. Something big has happened. There are, of course, narcissists in our capitalist world that will never acknowledge credit where credit is due, but yes, all this came from NASA and it’s clear and unambiguous.
SpaceX is, for now, also the only company looking at reusing the airframe, the other truly expensive component, and is the first to make real, tangible progress in that direction. But interestingly, that problem is intermixed with the turbo-pump problem, for the simplest technological solution is just to fly the booster right back to the launch pad when it’s done lifting your cargo. This was unthinkable before reusable turbo-pumps were perfected (it would require three separate firings in one flight – most turbo-pumps will literally blow up if you try to shut them down gracefully, much less start them back up). It won’t be long before the rest of the industry jumps on this bandwagon and does the same. In fact, we think they have but cannot confirm that it is coming from NASA research directly. Everyone is now fascinated with reusable rocket engines and airframes. The engineering streets are abuzz with talk. To see why, for a 50 million dollar launch only about 200,000 dollars is used for fuel. The turbo-pump suite costs from 10 – 40 million (which today are just thrown away). When the books are settled, at the least, it costs about 3500 dollars or more per pound for taking cargo to LEO. But if you reuse the rocket and its turbo-pumps that cost will plummet to less than 100 dollars a pound. In the next 10 years the boundaries of space are about to explode with activity. There are more resources that are easy to recover and bring to Earth than anything imaginable from past experience. It will be like the 49 Gold rush squared. And all this talk about “lightweight” and “mass restrictions” will all sound rather quaint.
And btw, this is why NASA is now focusing on a new Space Launch System (that Mondo rocket that looks awfully like the Saturn V), which is for deep space flight. They already know the LEO problem is solved and they are leaving it to private industry. That’s what all the confusion and hoopla in the political world, vis-à-vis space flight, is all about; people are realizing that a paradigm shift is occurring. Bring it on!
Neil, I will wink at the moon for you Sunday night.