Virgin Territory


His name was Mike Alsbury, may the Lord rest his soul. Not yet forty years old, with a family, and no doubt with the future literally in his hands.

I spent much of the weekend scouring the space blogs for this news, as I served in the Marines with one of Virgin Galactic’s pilots and feared it might have been him (it wasn’t). It’s not like we were great friends, but like a good teacher he was one of those officers who left a lasting good impression.

This had to happen eventually, just as airline accidents are going to happen. Flying is inherently risky, something too many people lose sight of thanks to decades of learning how to mitigate those risks. Every now and then, the holes in the swiss cheese line up and something nasty falls through.

Spaceflight is even riskier and less forgiving. Machines are often performing at the edge of their capabilities, both the craft which have to withstand tremendous aerodynamic and gravitational forces, and their motors which contain (and release) enormous amounts of energy.

The nexus of these forces is something called Maximum Dynamic Pressure, or “Max Q,” a function of air density and velocity. If you’ve watched any space launches, you’ve probably heard this term. Put simply, it’s the point at which an aircraft or rocket experiences the greatest aerodynamic stress. Think of it as the normal static air pressure being amplified around a speeding vehicle; the air squeezes harder as the vehicle accelerates.

This generally happens around Mach 1, the transsonic flight regime. This is also the speed at which SpaceShip Two’s reentry feather was deployed, according to NTSB. They say it’s normally supposed to be unlocked at M 1.4, which makes sense. Standing shock waves and related compression drag are Max Q’s ugly sisters, and I wouldn’t be surprised if NTSB finds the tail booms were overwhelmed by them once unlocked.

Tail booms feathered for re-entry. This is not supposed to happen at Max Q.

It frankly doesn’t take a rocket scientist to see how that would be very bad thing at Mach 1 while still down in the relatively thick air at 50,000′.

I’m alternately relieved and concerned that they’ve already figured this out. To be released this soon, it must have been face-poundingly obvious. While this is currently a “finding of fact” and not a “cause” there’s plenty of reason to think it’ll eventually end up that way. “Root cause” is a whole other matter, something that could easily take a year to determine. Ignore the credentialed talking heads on TV, as they’re certain to be talking out of their collective ass.

There was an awful lot of early speculation that this had something to do with the already-troublesome hybrid motor, but the oxidizer tank and solid fuel core were both found largely intact and appear to have functioned as expected. That’s only a partially good thing, as hybrids are reputedly difficult to scale up in size and this motor has a lot of development work left in it. I’ve seen them used frequently at amateur/high-power rocket launches, but am told that N2O starts to behave in strange ways when it’s pressurized at the kinds of volumes SS2 needs to use. Then there’s the fear that a chunk of solid fuel breaks off during the burn and clogs the nozzle. So yes, there’s lots of ways for a supposedly “safe” rocket to go boom (back to my point about containing enormous amounts of energy).

The problem is the airframe was designed around the shape and mass properties of the motor, so it’s not like they could just walk over to XCOR’s hangar and buy a couple of their liquid bi-prop rockets (or substitute the liquid motor Virgin’s working on separately, either). It’s created a pretty nasty sunk-cost trap, and this accident may be the only way VG can break free of it.

What little solace there may be here is found in the knowledge that it happened during testing and not on a revenue flight with paying passengers. One can only imagine how infamous (especially considering their clientele) that would be. What frightens me for the industry is that it almost certainly will happen at some unknown point in the future – the question is whether space tourism is far enough along that it can recover. Think about it: how many ocean-crossing passenger blimps have there been since the Hindenburg? A similar horrific accident during the early stages of passenger spaceflight might doom this new industry in the same way.

I’ve been to the NTSB Academy and seen their reconstruction of TWA 800, the 747 that exploded off of Long Island several years ago. It is a creepy thing to stand in front of that big open nose, stare down the empty rows of shredded passenger seats, and contemplate what those people went through as they continued to climb before falling out of the sky with the entire front end of the airplane blown off. I don’t envy the go-team that has to pick through this, but in the long run I have high hopes that whatever they find will benefit the whole industry.

Some investors and ticket holders are predictably starting to bail, and we can only hope Mr. Branson’s commitment to the project is enough to see it through this tragedy. It took the Apollo 1 fire to uncover latent problems with the program, and one can make a pretty good argument that we might not ever have made it to the moon without it.

Here’s hoping Mr. Alsbury is remembered with the long list of other test pilots who have given their lives to open up previously-unknown frontiers for the rest of us.

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