Monday, June 8, 2015

Why isn't the future now?

As I stare down the barrel of an upcoming 14-hour flight back to the United States of Awesome--this time with a tiny human being--I ponder a different reality. A gentle universe where 14 hours is two hours, and "how on earth will we distract her for half a day!?" becomes "hey, maybe she'll just nap through it."

The thing about this scenario is that it was this close to being not an alternate reality, but simply reality. So pull up a chair and let's talk about VentureStar, a grand idea in the mid-90s that was derailed by something utterly mundane.

There's this proverb about how a horseshoe nail caused the downfall of a kingdom. There are lots of steps between the nail and the downfall, but the gist is simple: a bunch of things had to happen right, but one went wrong, and bam, all of a sudden the barbarians are there installing a new king and reorganizing your postal system.

What does that have to do with VentureStar? Let's first take a look at what VentureStar was.

The short version was that it was a single-stage-to-orbit, reusable launch system. In non-nerd terms, that means it takes off and lands in one piece, and like an airliner, you can refuel it, check the oil and shoot it back into space again. This is simpler that today's staged designs, and crucially, much cheaper because you're not dumping millions of dollars' worth of hardware into the ocean each time you launch.

Also looked awesome.

It was a joint venture between NASA and Lockheed Martin, neither of which were rookies in the shooting-things-into-space game. And the first step would be a technology demonstrator: the X-33, a suborbital spaceplane that could in theory be scaled up for passenger travel.

Passenger travel. Yeah. You see where I'm going with this?

The amazing thing about all of this is that despite the science-fictional feel of the whole endeavor, the technology was pretty much ready. One of the most complex bits of any rocket--the engine--was tested and worked great. Unlike conventional rocket nozzles, this was an "aerospike" design, in which the exhaust flowed around a central pillar. This actually simplified the design and allowed it to work well at many different altitudes, unlike a conventional engine, whose nozzle is most efficient in a relatively narrow band. Whatever, here it is:

OK, so the engine was good. Avionics--the electronic gizmos you use for naviation, communication and so on--all well-developed, thanks to the Space Shuttle program. Ditto for flight controls. Heat management for the X-33 wouldn't be a huge deal, as it didn't have to hit the blistering speeds necessary to make it to orbit.

But then there was the issue of the fuel tanks. Remember, this is a single-stage spacecraft. And the thing about staging is it allows you to drop excess weight as you go--are those engines done firing? Drop 'em! Fuel tank empty? Drop it! VentureStar would not be able to do that. So everything it carried would have to be as light as possible.

Rather than building the tanks from metal--as one does--these tanks would be made from composites, which are lighter and stronger. But they also had to fit in an oddly shaped space. To wit:

A very trying angle. Ha. Trying. Angle. Triangle. Sorry.

And that worked against composites. Being crammed into an asymmetrical space meant that the forces exerted on the tanks were not distributed evenly. And that worked against composites' strengths. In 1999, the hydrogen fuel tank for the X-33 failed during testing. And even with something like 90 percent of the spacecraft built, NASA threw up its hands and said, "Eh, not worth it." At the time, it seemed like an insurmountable problem. So after a bit more fiddling around with it, Lockheed Martin gave up too.

Could this be pulled off in 2015? Probably. Is anyone working on it? Not that I'm aware of. Does this mean I'm probably going to be stuck with a discombobulated kid on my lap for 14 hours instead of two? Absolutely.

So that's the story. The fuel tank, arguably the least complex piece of a multibillion-dollar rocket, ended up being the VentureStar's horseshoe nail. And for want of a nail... well, you know how this ends.