Michael Belfiore updates his previous post, to indicate that Rocketplane (as I was quite confident was the case) has in fact been in discussions with the FAA. But he persists in his misguided (in my opinion) fear of liquid propulsion:

I say a good healthy dose of skepticism never hurt anyone about to climb into a commercial spaceship fueled with explosive liquids.

While not denying that skepticism is always appropriate to some degree, he still seems to think that hybrids cannot explode. That would come as a shock to many (including me) who watched an Amroc 250,000-lb-thrust motor launch itself down the mountain up at the rocket lab in the early 90s, as a chunk of rubber got caught in the throat, blocking the flow and causing the internal pressure to build up to the point that it blew the bolts on the aft bulkhead, with spectacular results. Hell, even steam boilers can explode (this killed many people in the early days of river transportation).

It’s true that a hybrid can’t achieve total combustion in the same way that mixing liquids can, but it’s a big mistake to think of them as intrinsically “safe” (a term that is always relative, and never absolute). I would personally feel just as comfortable on a vehicle powered by one of (for example) XCOR’s rocket engines as by any hybrid, because I’d be confident that they would build adequate margins and safeguards into it to make it as safe as reasonably possible.

Michael Belfiore is concerned about Rocketplane’s business plan and technical approach:

These guys say they’ll fly paying passengers–and not just any paying passengers, but ones able to blow almost a quarter of a million dollars on a what amounts to a fabulously expensive roller coaster ride–in an experimental spacecraft built around a used business jet. Because its cheaper.

Well, there’s actually nothing wrong with that. It’s certainly an airframe with which we have a lot of experience (though not necessarily for this application). It’s not at all obvious to me that it’s better to use a new design from scratch. And the fact that it’s used doesn’t bother me, either. Many airliners are flying safely with aging airframes (and we now have B-52s flying some of whose current flight crews may have grandfathers who flew them). What matters is not age (or even cycles), but inspections.

And there’s more, unfortunately. Turns out the rocket engine is going to be preowned as well, of the highly explosive liquid fuel variety. That’s because the built-from-scratch engine they were going to use blew up on the test stand.

Without knowing more about this, I can’t really comment, but liquid engines are not intrinsically dangerous, marketing hype from SpaceDev aside. It depends on the design, and the margins.

And something for me to follow up on: a tipster tells me that Rocketplane hasn’t approached the FAA about certifying their hot-rodded Learjet–surely a requirement for following through with their business plan.

If they haven’t talked to the FAA at all, I’d be concerned (and surprised, if not astonished). But if the “tipster” is saying literally that they haven’t applied for “certification,” I wouldn’t expect them to, now or later. “Certification” has a very precise meaning in this context. The whole purpose of the new launch legislation last year was to allow passengers to fly without having to go through certification of a spaceplane (something that the FAA-AST doesn’t know how to do at all, and that FAA-AVR, the part that certifies aircraft, doesn’t know how to do it for spacecraft).

All that is needed is a launch license. Virgin Galactic may attempt to get their spacecraft certified (because that seems to be Burt’s druthers), but if they do, I suspect they’ll find out that it will throw a wrench into their business plans, cost them a lot more than they expect, and delay their entry into the market for years.

[Update on Sunday night]

Robin Snelson makes a good point in comments–Belfiore is comparing apples and orange. Virgin Galactic is a spaceline, whereas Rocketplane is a manufacturer. Better to compare the latter to the SpaceShip Company.