XCOR had a test flight incident that might have been a problem if the vehicle had been unmanned. One of the engines didn't shut down due to an electrical failure. Rutan let the engine burn long enough to give him the energy he needed to land, then shut it down with a manual valve and landed safely.

This is how you test vehicles--not with billions of dollars in software and simulations.

Right on.

Here's what I'm wondering: if the EZ-Rocket wasn't already in a position to glide to a safe landing then why did he command the engines to shut down in the first place? Sure, he was probably planning to start them again, but on a test flight like this you sure don't assume that they *will* start.

Not that it matters, and it's probably just the usual gap between reporters and reality.

It wasn't a reporter--it was a company press release. Presumably he was shutting them down for a purpose related to the test flight, but I don't know what it was.

Actually, Rand, both are needed. Certainly, Rutan's design was developed via computer simulation and validated in test flights. You need both flight tests and computer simulations to validate weapons and aircraft. Otherwise we're back in the '50s and losing test pilots by the dozens. And frequently not learning anything from the loss.

In addition, there's a great deal of difference between testing a manned vehicle and testing an unmanned rocket. I doubt if you could persuade Rutan to pilot a NMD kill vehicle to its target, for instance...

The Long EZ was developed on a computer?

I don't think so. Go check the history on that airplane. It was designed in the 1970s.

I'm not saying that computers shouldn't aid design. I'm saying that you need to go out and incrementally test vehicles, with pilots in them, rather than having an all-up launch system, simulating the hell out of it, and hoping that it works the first time (i.e., Space Shuttle, and all planned NASA follow-on vehicles).

I didn't say he designed the Long-EZ using computers. But if you check out this:
http://www.airspacemag.com/asm/web/twd/Rutan.html
you'll see that although computers don't help him much with the creativity, they greatly speed up the analysis.

Another thing I'd like to point out is it's a very different thing to design a gasoline-powered aircraft that flies at relatively constant, low Mach numbers and fairly benign temperature conditions, than to design a vehicle that has to fly between Mach 0.2 and Mach 15 (for the sake of argument), and at extremes of temperature and pressure that Rutan never has to consider. And I can practically guarantee that a LOT of computer analysis was done getting rocket engines in this thing.

In your article, if you meant "aircraft" when you said "vehicles", I'd say yes, there are probably some improvements in order. But Congress likes to see an answer that works on paper before you go fly a hundred-million-dollar piece of hardware. And I fail to see how you'd start incremental testing of, for example, the National Aerospace Plane by beginning at this level.

You incrementally test things like the NASP by flying less ambitious vehicles that test various aspects of it (and in fact there were some scramjet flight tests planned, but later cancelled).

I don't know where you got the idea that I don't think that we should do computer aided design. My point is that we cannot rely solely on it (as we did with, for example, the Shuttle), and that we have to do flight test, and a lot of it, with gradual envelope expansion, and that it will be cheaper and safer if we do it with pilots.

I misunderstood. My apologies.

I'm not sure if your idea is workable or not. I do know that at some point, you can't test scale models but must test full-scale, and at the proper conditions. DARPA has done quite a bit of scale-model testing in the past; maybe NASA should have an analogue. If your initial point was that NASA frequently chooses the opposite of cost-effectiveness in its product development, you're not going to get any argument from me.

However, when you said "vehicle", I took that to include any missile, which are commonly referred to as "vehicles" in the wonderful world of defense.

No, missiles are irrelevant to cheap space transportation, which is what XCOR is all about.