So long, United Launch Alliance (and your one-shot rockets), we hardly knew ye. Today, it's SpaceX's reusable Falcon 9 that's all the rage in space -- cheaper than the rockets designed by Lockheed Martin (NYSE:LMT) and Boeing (NYSE:BA) for their United Launch Alliance, flying more missions, and now "flight-proven" to boot.

On March 30, as you've almost certainly heard by now, SpaceX conducted the first-ever relaunch of a Falcon 9 first-stage rocket. In so doing, SpaceX proved the concept of reusable rockets. But that's not all SpaceX wants to do.

It's also amending the very lexicon we use to describe space flight.

SpaceX SES-10 Falcon 9 rocket at liftoff.

On March 30, 2017, SpaceX's SES-10 mission blasted off, and blasted its way into the history books. Image source: SpaceX.

It depends on what the meaning of "rocket" is

For as long as humans have launched satellites into orbit, they've done so with the assumption that the very expensive rockets powering the launch would be discarded, to burn up as so much space junk after launch. Such rockets were called simply "rockets" -- because they were the only type built. But now SpaceX has created a new kind of rocket, one that is designed to be used over and over again.

So what do we call it?

Journalists have taken to calling SpaceX's Falcon first stages "used" upon their recovery, and "reused" when they make repeat trips to space. (SpaceX plans six such relaunches this year on Falcon 9s, plus a few reuses as strap-on boosters for its new Falcon Heavy rocket.) But SpaceX believes it's time to start thinking of rockets designed for multiple uses as the rule rather than the exception.

A SpaceX rocket designed for reuse will be described as "flight-proven" after its first successful trip to space. It will be deemed ready to fly an additional nine missions after undergoing quality inspection, or as many as 99 more missions with periodic refurbishment.

Epic dis, epic savings

If the new label sticks, this will be something of a marketing coup for SpaceX, as it builds an entire fleet of such "flight-proven rockets." Everybody else's rockets, on the other hand -- those not designed for reuse -- will be tagged with the label "disposable."

It'll be a dis of epic proportions.

At the same time, it will hammer home to potential customers how much better a value proposition SpaceX's rockets offer, relative to the competition at Boeing and Lockheed (and also, for that matter, at Arianespace and Roscosmos). The real point of reusing rockets isn't just to earn the "flight-proven" label, but to cut the cost of spaceflight for both SpaceX and its customers.

As SpaceX CEO Elon Musk explained to reporters at the launch, "if the cost of the rocket is, say, $60 million ... as we optimize the cost of reuse of the booster, we're really looking at maybe three-quarters of the rocket dropping by an order of magnitude [in cost], and maybe more."

Here's what that means in dollars and cents: $45 million of the $60 million cost of a Falcon 9 rocket is contained in its first stage. Reduce that cost by "an order of magnitude" by reusing the first stage, and first stages should cost SpaceX only $4.5 million per launch, on average.

Even if the rest of a Falcon rocket cannot be reused, and that residual $15 million cost remains constant, the total cost of all parts, reusable and non-, works out to just $4.5 million + $15 million = $19.5 million.

And even $19.5 million could be on the high side, because last week, SpaceX also conducted its first recovery of a used rocket nose cone (set down at sea using parachutes and reverse thrusters) worth $6 million -- about 10% of the rocket's cost. And it's considering trying to recover the spent second-stage rocket from its Falcon Heavy launch later this year. With each used rocket part sent floating gently back to Earth for reuse, the total cost of relaunch goes down a little more as well.

Meanwhile, United Launch Alliance partners Boeing and Lockheed Martin continue to market Atlas V launches at nearly $150 million a pop. If SpaceX keeps on logging success after success with its "flight-proven" project, Boeing and Lockheed may have more than just a marketing problem on their hands.