When you watch the above video of last night's historic landing of the Falcon 9 reusable rocket's first stage, it's hard not to get caught up in the sheer excitement of the SpaceX crew. (We didn't see SpaceX founder Elon Musk cheering, but he must've been, somewhere.) This is the first time a rocket has boosted a payload into orbit—in this case, 11 communication satellites—and then made a vertical landing at Cape Canaveral. Falcon 9 can now be reused in another launch.

The success comes less than a month after Blue Origin's New Shepard suborbital rocket successfully returned to Earth, and six months after another Falcon 9 rocket exploded shortly after liftoff.

Why is last night's landing so important?

Let's put it in the larger context of the American space program. For all the wondrous things our space program has achieved—and the impossible challenges it faces tomorrow—the whole enterprise rests on 7th-century technology. If you want to go to space, you need a giant tube of fire. Wth respect to both its exploration and defense purposes, our space program is defined by rockets—and oftentimes limited by them.

SINGLE-USE ROCKETS VS. REUSABLE ROCKETS

The problem with rockets, historically, is that they're expensive and single-use. A rocket lifts a payload to space, and then falls into the ocean. That's a lot of money, time, and engineering for 10 minutes of activity and an eternity of perplexing marine life. The space shuttle was intended to improve the process—its main engine, the RS-25, is reusable—but one could hardly point to the shuttle program as an example of cost efficiency in space exploration.

When the shuttle fleet was decommissioned, NASA extracted the engines from the spacecraft-turned-museums and put them in storage. It has since decided to use them for a new rocket—the Space Launch System (SLS). But rather than leverage the engine's signature feature—reusability—NASA has decided instead to push them a little harder than their intended design, and again, drop them into the ocean after a launch. We have enough engines for four launches. After that, the price of engines will have to drop, or hard decisions will need to be made.

The SLS is more Mayflower than cargo freighter, and when the enormous rocket is used, it's going to have to count. The two destinations most commonly discussed for its payload are Mars and Europa—one to send life to another world, one to find life on another one. For "day-to-day" work, American access to space relies heavily on the Atlas V rocket built by United Launch Alliance. The Atlas V uses the RD-180 rocket engine. That's a problem, because Congress has essentially outlawed the purchase of the RD-180.

What happened is this. Immediately after the collapse of the Soviet Union, the United States rightfully worried about what would happen to all of those ICBM-capable rocket engines—and the engineers who build them. (It's harder than you might think to build a rocket that can kill everyone on the other side of the planet.) To prevent a free for all, the U.S. invested heavily in the Russian rocket industry. It helped that the Soviets ran a truly great space program, and that their engine, the RD-171 (and later the RD-180), is a fantastic engine. The United States never bothered to cultivate serious domestic RD-180 development because the Russians could turn them out at $10 million a pop—a real bargain for a million pounds of thrust.

So we ended up relying entirely on Russian-made engines for our workhorse Atlas V rocket launches. Then conflict erupted in the Ukraine. The U.S. government, in an effort to punish Russia for its deeds, banned the purchase of RD-180s. ULA has since been working from a stockpile of the engines, though its numbers are growing thin indeed.

But while NASA and its commercial partners are taking reusable rockets and making them disposable, upstarts SpaceX and Blue Origin are taking disposable rockets and making them reusable.

ELON MUSK'S VENTURE

While planning his post-PayPal life, Elon Musk toyed with the idea of using his newfound riches to send a small lander to Mars. The prohibiting factor, he learned, wasn't a lander or interplanetary communications, but rather, the rockets necessary to get a spacecraft off the ground. After realizing the massive inefficiencies in the entrenched American rocket industry, and the market opportunities present for a nimble upstart, he founded Space Exploration Technologies Corporation—better known as SpaceX.

He has bitterly taunted the industry for resting on its laurels for 50 years. "One of our competitors, Orbital Sciences, has a contract to resupply the International Space Station, and their rocket honestly sounds like the punch line to a joke," said Musk in a WIRED interview in 2012. "It uses Russian rocket engines that were made in the '60s. I don’t mean their design is from the '60s—I mean they start with engines that were literally made in the '60s and, like, packed away in Siberia somewhere."

In 2008, SpaceX launched the Falcon I rocket into orbit. (It is named for the Millennium Falcon.) The company's present rocket, the Falcon 9, is comparable to the Atlas V and uses an American-made Merlin engine—removing Russia from the equation. This, coupled with an astoundingly lower launch cost, has made SpaceX attractive to NASA and the Defense Department. Presently, the Falcon 9 helps resupply the International Space Station, and will soon be human-rated to send astronauts into space. It has also been certified by the U.S. Air Force for national security space missions—only the second after uber-entrenched United Launch Alliance.

STICKING THE LANDING

Jeff Bezos, CEO of Amazon.com, founded Blue Origin in 2000 with the goal of sending humans to space. The company has largely operated under the radar, remaining virtually unknown outside of the space enthusiast community until September 2014, when a partnership was announced with United Launch Alliance to build new rocket engines for an Atlas V successor. Seven months later, Blue Origin mounted the first launch of its New Shepard launch system and capsule. (The system is named for Alan Shepard, the first American in space and the only Mercury astronaut to also go to the moon.)  Blue Origin's present focus is on space tourism and engine development. The company's goal is safe, reliable, and inexpensive flights into space.

SpaceX and Blue Origin have much in common. They were both founded by hyper-driven dot-com billionaires; they both threaten the hegemony of United Launch Alliance, Orbital ATK, and a handful of other defense contractors; and they both intend to lower the cost of space travel by developing reusable rockets. Once we stop dropping rockets into the ocean, the price barrier to space will plummet.

But while New Shepard's landing last month was a tremendous achievement, Falcon 9's landing last night was a much bigger triumph. As Elon Musk has been quick to point out, landing a Falcon is a far greater challenge than that of New Shepard. A Falcon rocket flies twice as high (124 miles compared to 62) and is 80 percent faster (Mach 6 to Mach 3).