The primary focus that SpaceX has in its endeavours is in re-usability of launch vehicles. The Falcon 9, in current form, is a launch vehicle in which the first stage is capable of making a controlled landing back at the launch site, or on a drone ship in the ocean (as launch needs permit) and can be refurbished and re-flown. The idea is that this will, in the long run, once it is fully developed, cut launch costs heavily. Of course, the second stage of the rocket is lost, but that’s something we will discuss in a future article.
Right now, Falcon 9 1st stages are apparently rated for only a few re-flights, and refurbishment is reported to be a somewhat involved process – as to be expected as they are developing the concept and the technology as they want to implement it. As things stand, at the time of this articles writing, 5 Falcon 9 1st stages have made more than one flight. Many others have flown and landed, of course, but they have yet to have been selected for another launch.
Now, as I said, this is a primary focus of the company – so much so, that they have a buzz word for these boosters. “Flight Proven.”
The engines of a flown Falcon 9. Note the carbon deposits on the engine bells. Imagine the shape of the internal components after a flight.
Now, this sounds nice, in the “Oh, we know this machine works” kind of way, like an airliner or a car – refuel when you need to and otherwise, things are fine, right?
That’s just not how these things are, though. The extreme environments that rockets operate in preclude any remote notion of just re-launching a freshly used stage. The stresses on the airframe, the force of landing, the vibrations and roughness of the flight on various mounted components and of course, the engines – they will always require at least some components to be replaced, if not the whole engine outright being swapped out for a new one.
The rockets simply have to be refurbished. Everything on the booster needs to be checked out, and parts that require replacement or repair getting the servicing they need. Airliners may get serviced every few hundred hours of flight, and your car gets various tune ups and standard repairs on average rates as well – the classic oil change every 10,000 miles comes to mind. Imagine if it needed these repairs every single time you went out and came back home? New spark plugs, tires, a new battery and a fresh paint job?
You also know, I’m sure, how it is any time you replace something – you want to break it in, make sure it isn’t going to just fail on you outright. New parts will either fail early on, or fail at the natural end of their lives. You don’t get that kind of grace period with rockets – you can test components, sure, but you when it’s all said and done it’s still new parts on an old rocket. When you fire it off, it’s got a few minutes of incredible stress to go through, and it has to work – you don’t know for sure, though, how those new parts will behave, do you?
A Falcon 9 1st stage landing. Note the charring on the outside of the booster.
As for the old components, while they seem fine and probably are, you can only check them to such a degree without taking the whole damn thing apart and testing it bolt by bolt – something that just isn’t going to happen. It’s entirely possible to miss something, somewhere, when checking the machine out. The part might damn well be okay, but you just can’t be sure. All you know is it didn’t fail on you yet.
So, with a “flight proven” booster, what do you actually have? A mix of new parts with the same chance of failure as any new, unflown booster, and used parts, which may be fine, or may have suffered some possibly mission-ending damage that slipped by detection during the refurbishment process.
To be fair, I don’t know all the details that go into the process of SpaceX making a booster ready to fly again, but I know enough about rocketry and machines in general to have an idea on just what certainly must go on in the process.
To me, the end result is a machine that has a slightly higher chance of failure than if it were fresh from the factory and unflown. I’m not saying this to discourage the concept of re-using a booster, although I do think the proper refurbishment of a flown rocket will cost more than is estimated or proposed, that’s another discussion.
Flight Proven in the end, means nothing to me though because the rocket being flown is a combination of used, possibly damaged or weakened parts, and new, “reliable as they could be” parts to replace those that need it.
Remember, this Falcon 9 second stage failed during on-the-pad testing, for no real reason beyond a component actually failing. New parts, old parts, both can fail.
This isn’t an airliner. This isn’t a car. This isn’t a new computer. It isn’t the same machine flying time and time again, this is a machine that’s been under tremendous stress over just a few minutes, one which, to be able to fly again, requires critical components be replaced. Those components themselves will have not been tested in flight, and once they are, who’s to say they won’t be replaced again, or be damaged subtly, but critically, in the process?
“Flight Proven” is just a meaningless buzz term, a part of the hype machine that SpaceX has set up. Again, I’m not inherently against the idea of re-using rockets – I’m just not accepting of it being treated so casually.
Rockets aren’t airplanes. Rockets operate for only a few minutes under stresses that an aircraft would generally experience over its entire operational life. They don’t just land, and then re-launch like a plane landing and taking off, they require heavy maintenance that I think people just don’t understand is the case – and quite honestly, I think that’s the way SpaceX wants it.
Why else would they use such a term to describe a used booster?