Update: SpaceX made a historic first landing of the first stage of Falcon 9 on its autonomous barge, Of Course I Still Love You.

Step right up folks, for front row seats to Round 6 of giant rocket versus the floating barge. Later today, if it launches as planned at 4:43pm ET, SpaceX engineers will attempt once again to land a Falcon 9 rocket safely onto a football field-sized barge floating in the Atlantic Ocean.

Of course, sticking that landing is not the Falcon 9's mission per se. Before it comes down, the rocket is headed for low Earth orbit, where it will release a Dragon cargo capsule. The capsule is bound for the International Space Station, carrying 7,000 pounds of goods. Including an inflatable habitat module, several science experiments, plus parts, food, and other space station essentials.

This will be SpaceX's eighth resupply mission to the ISS. Probably the most exciting cargo is the Bigelow Expandable Activity Module, a collapsable live/work space. Packed up, the thing is less than 8 feet wide and 6 feet long, but expands to 13 x 10.5 feet, adding 565 cubic feet for the astronauts to float around in. Well, theoretically—they'll only be inside for a few hours total over the next two years.

The science portion of the module is carrying 20 mice from the pharmaceutical company Eli Lilly. Animals (including astronauts) in microgravity experience substantial bone loss, against which the mice will be dosed with a myostatin inhibitor. The results will help the drug company develop compounds for fighting terrestrial bone loss.

In fact, the space station is such a good lab for microgravity experiments that the Dragon capsule will be delivering two others to the ISS. The first will look at how fluids in microgravity behave at a nano scale, which can be very, very different from how they behave at larger scales. This is important for fields ranging from biology to computer science. The final experiment will explore how certain proteins crystallize in low-G, which will help pharmaceutical companies design better drugs.

And sure, delivering those experiments to the ISS is very important. But no matter what NASA or SpaceX say to play down the rocket landing, everybody knows what the main event today really is.

In order to land on the floating barge, positioned in the Atlantic Ocean, the Dragon 9 will use leftover fuel to slow down its descent. Computer algorithms monitored by human engineers will steer the thing down, where hopefully it will touch down slow enough and straight enough for the landing struts to deploy. Finally, if successful, the SpaceX team will collectively exhale and cheer like wild maniacs.

You should too. Reliable reusable rockets will be an inflection point in making space accessible. Each Falcon 9 costs somewhere around $60 million. Stop blowing the things up every time you launch a mission, and you open the door to low-cost space travel and shipping. (The cost of launch is currently around $3,000 a pound.) That could mean a vacation to low Earth orbit might affordable in your lifetime, but more immediately it means NASA spends way less money getting stuff out of the gravity well and more money on sending cool stuff into orbit. It also shortens the horizon for more ambitious stuff like asteroid mining.

Thus far, SpaceX CEO Elon Musk has been relatively glib about the company's repeated landing failures. (Ready for another rapid unscheduled disassembly, everyone?) Makes sense: He's an engineer, and that breed has a sick fascination with failure. Also, there are a thousand things that can go wrong with trying to land a rocket on a floating barge. The only way to figure out solutions is crash, crash, and crash again. So crash on, SpaceX, because once you succeed, it will be so, so worth it.