Let's see:

His remarks are in bold italics. My replies are in plain text.

A) It's not a spaceship or even a precursor to one. The energy required to boost SS1 into orbit would be about 50 times what it currently expends to make its short zoom-climb into "space".

There is no way a single-stage rocket plane built with existing materials can reach orbital velocity, even if it used real rocket fuels instead of SS1's mixture of rubber and laughing gas. And the trick of dropping SS1 from the White Knight carrier aircraft won't help much in gaining orbital velocity. The air-launched rocketplane configuration reached its natural performance limits with the X-15 (and even the X-15A-3 had to use disposable fuel tanks to reach Mach 6).

Funny, it seems the Russians and the Germans, among others, think otherwise. While technically very challenging and expensive, studies over the years have produced quite a few air launched designs including the operational Pegagus booster. I also seem to recall a recent X-43A hypersonic vehicle that reached Mach 8. A future planned flight is planned to hit Mach 10 or so.

More to the point, he's flat out wrong about some of the technical details. For example, the X-15 used ammonia and LOX for propellants with the resulting Isp of 294 seconds. That's far from the most efficient propellant combination out there. Designing a rocket plane with more efficient propellants would allow for higher velocities for a given launch weight.

Even more serious is the need to dissipate that x50 extra energy during reentry. SS1 borrows from Max Faget's original Shuttle design the concept of flying a spaceplane belly-first (that's "stalled" in pilot language) in the early part of reentry so it will loose most of its velocity at high altitude before it hits the thick lower air. Rutan has invented a neat way to make SS1stable in stalled flight, but I don't see how his "hinged P-38" configuration could work at orbital velocity and heating loads.

I don't know anyone, including Burt, who is planning on using the SS1 reentry approach for orbital flight. If Burt decides to design an orbital vehicle, then he'll have to address the reentry problem.

SS1 is really a stuntplane intended to whip up public interest and favorable news media coverage. Everything about the project -- the rat-shack high desert Right Stuff ambiance of Mojave, the air-launch format, the cute round portholes, even the 63-year-old test pilot -- is carefully calculated to push the "spend money" buttons in the brains of the aging Baby Boomers who are the only sane people who still have a romantic passion for space travel.

No, SS1 was designed to meet the criteria of the X-Prize contest. Period. Burt has worked out of Mojave since the 1970s, and Mike Mellville has been one of his test pilots for most of that time. The portholes are a good compromise between visibility and weight. Burt uses a design philosophy called "Plain Vanilla." He designs things as simply as possible to accomplish a specific task. It's a philosophy that has served him well.

It's not even a viable vehicle for the "suborbital tourism" market. SS1 is narrowly designed around the X-Prize competition and lacks many features customers would demand. Rutan has made it clear in recent interviews that SS1 will go to a museum not too long after the X-Prize is collected, and a bigger vehicle will be made for initial tourist flights. He believes that a viable tourist spaceplane must have major improvements: Longer time in zero-g so passengers can unstrap, abundant room to float around in, big windows to see space through, 6-10 seats to spread out the overhead costs.

And what's the problem with that? The Wright Brothers first plane was unstable as hell and barely managed to fly in ground effect for a few seconds. Less than 5 years later, they were able to carry a passenger for flights lasting over an hour. Why would Burt build a vehicle larger (and more expensive) than necessary to accomplish the intended mission - winning the X-Prize? Once that mission is accomplished, there is plenty of time to design a larger vehicle more suitable for tourism.

One necessary step in building a tourism market is exciting the public. As an analogy, most people still didn't trust airplanes well into the 1920s. Charles Lindberg's flight from New York to Paris caused tremendous excitement and the number of people who wanted to fly increased dramatically. The Spirit of St. Louis was a cramped single seat airplane with lousy flying characteristics. I know of only one time when Lindberg carried a passenger (Henry Ford). Still, that tiny plane, totally unsuited to anything other than winning the prize, had a dramatic impact on aviation development. Once the excitement was there, larger and more capable planes (like Henry Ford's Trimotor airliner) were developed to serve the market.

The big question is: Is is possible to stretch the basic WK/SS1 configuration to meet these goals? Some enthusiasts suggest that SpaceShipTwo is already half-built in a hangar somewhere. If so, it would have to be a pretty big hangar.

The problem with all aircraft-launch concepts is that as the launched vehicle scales up, the carrier airplane scales up even faster and soon the combination is too big and too heavy for any runway at Mojave Airport. To see what a real base for winged spaceplanes might look like, check out the gigantic hangar and endless runway at Groom Lake (Area 51).

The White Knight was designed to accomplish a specific task - carrying SS1 to about 50,000 feet high. It is powered with two jet engines from a T-38 trainer that produce about 5,000 pounds of thrust each using an afterburner. The design can be evolved to carry heavier payloads relatively simply. You'd need to increase the wingspan, the thrust, and perhaps the ground clearance. None of those are exactly insurmountable engineering challenges. Since speed isn't a big issue, to carry a large payload to high altitude, you typically need a low span loading (large wingspan for the takeoff weight) and good power to weight ratio. Furthermore, scaling up a plane doesn't automatically translate into longer runway requirements. For example, the giant 747 and C-5 aircraft need less runway than an early (and much smaller) 707.

Regarding the need for a gigantic hangar, Voyager, built in the same facility that Burt uses today, had a wingspan of 110 feet. The White Knight's wingspan is 82 feet. It sounds like they can build a considerably larger aircraft than the existing White Knight in their current facilities. Oh, and here's a newsflash for him - planes can be built with detachable wings! You can build a larger plane in his existing hangars! What a concept.

It's not clear that a real demand for suborbital tourism exists. While looking at a photo of Mojave Airport a while back, it occurred to me that some aircraft already parked there meet most of Rutan's criteria. There are many first-generation wide-body airliners in storage at desert airfields.

With fewer seats and more padding, they would be equivalent to NASA's famous "Vomit Comet" and could be flown in zero-gee parabolas. Put some space images on the windows and you have most of the suborbital tourism experience for a longer time at a much lower cost. If the suborbital tourism market really exists, why isn't somebody doing this?

They are. You can go to Russia and ride on their equivalent of the Vomet Comet for about $10,000. There are others interested in selling similar rides. This has been going on for years. Funny he seems unaware of that.

One might say that this would be fake suborbital flight, like a good copy of the Mona Lisa, which would lack the appeal of the real thing complete with real FAA-issued "civilian astronaut wings". But shouldn't the army of rich people allegedly wanting to pony up ~$100,000 for the real thing be willing to pay ~$2000 for the Vomit Comet experience? Would anybody want to buy or steal the original Mona Lisa if copies of it weren't selling?

There have even been one or two firms that offered zero-g flights for scientific experiments. Why has none of them branched out into "space tourist training"? It seems to me that if there really were a significant number of people who would actually pay big money for a suborbital flight (not just say so in a survey), there would already be a converted L-1011 making parabolic zooms above Mojave right now.

If all someone is interested in is a few seconds of weightlessness, I could probably do that in my Piper Cherokee. If they want a longer weightless period, then a jet would be much better, but more expensive. If they want to see the curvature of the Earth and experience several minutes of weightlessness, then you're going to need a vehicle like a scaled up version of SS1 or a ballistic rocket. Each step up in performance and capability has a corresponding increase in cost. My Cherokee costs a hell of a lot less than a business jet like a Gulfstream V, both to buy and to operate, but that doesn't stop Gulfstream from selling quite a few of their planes.

Burt Rutan is not the right guy to design profit-making tourist spacecraft. SS1 is a logical extension of Rutan's long history of designing one-off stuntplanes for rich sportsmen who want to set a record, or homebuilders with a garage going to waste. These aircraft are intended to make a few test flights plus one to win the trophy or impress the neighbors, and then be retired to a museum.

They are works of art, not commercial airplanes designed to serve the public and make money for their owners. Rutan doesn't consider mundane issues like maintenance costs or fatigue life, any more than Michelangelo calculated the potential gate receipts at the Sistine Chapel. On some of his aircraft, you have to saw a hole to replace a component that fails! It's no surprise that the only attempt to market a Rutan design for general use (Beech Starship) was a complete failure.

As for his "homebuilders with a garage to waste" crack, perhaps he needs to take a look at some of the planes available to homebuilders today. In addition to the low and slow puddle jumpers, you can get high speed pressurized planes like the Lancair IV-P and even homebuilt jets like the Viper. Many of these designs are built using composites first popularized by Burt back in the 1970s. Go walk the flightline at Oshkosh some time and see what the homebuilders are building, then compare it to the products from the old line companies. Some of the best production planes available today evolved from their homebuilt roots, such as the Cirrus and Laincair designs. While Piper and Cessna continue to sell decades old designs, Cirrus and Lancair are selling much more capable designs (for about the same price as the Cessnas and Pipers) and they're made from composites.

Burt's specialty is designing aircraft to meet specific needs. Many of them are one-off proof of concept designs, like his version of the Beech Starship. Once he turned the design over to Beech, they took the design and went through a long and very expensive certification process (at the time, the FAA still didn't have a handle on certifying composite aircraft). By the time they got it certified, it cost a fortune to manufacture and the performance wasn't any better than the old King Airs. They were expensive, especially when you're trying to recoup your R&D costs, and they came to market at a time when the entire industry was in a slump. Not very many were sold.

In a career spanning over 30 years, Burt has designed over 300 planes. Over 30 of those designs have been built. Some of them like the V-Jet II and ATTT were technology demonstrators. Others, like the Adam M309 and Vantage, were intended for production. The company trying to build the Vantage went bankrupt in 2002. The M309 (Burt's 309th design) is now called the A500 Carbonaero. It is nearing certification and may reach customers this year.

Oh, and about having to punch a hole to replace a component in a plane - a C-130 mechanic told me that they have to do exactly the same thing to replace a pump built into the wings. That's a design that has been in production for 50 years. There are a lot of planes out there that aren't designed for easy maintenance (e.g. Moonies, the Space Shuttle, and just about anything else that flies, according to most mechanics.)

Rutan's airplanes are the modern equivalents of the unlimited racers and long-endurance planes of the 1920-40 era. Aircraft like the Granville Brother's GeeBee and Ryan's Spirit of Saint Louis explored the limits of technology, and for that very reason could not become useful fighters or airliners without massive redesign by regular engineers who had to allow for the needs of the real world. There's a huge difference between a GeeBee and a P-36. I think the differences between SS1 and a reliable, long-lived tourist spaceplane will be just as great.

He makes some pretty absurd statements here. Vehicles are designed for a purpose, and record setting vehicles are usually designed for that specific task. The GeeBee racers were designed to win races, not as fighters. BTW: the Granville Brothers who built the GeeBees weren't engineers, but they managed to build the world's fastest plane in their day. The Spirit of St. Louis was designed by good engineers at Ryan, but it was designed to carry one person from New York to Paris. It was never intended to be an airliner. For that matter, my Honda CR/V is a pretty fair car but it wouldn't last very long as a freight hauler or serious off road vehicle. The SS1 was never intended to be a long-lived tourist spaceplane. It was designed to win the X-Prize. There's no reason why the basic design can't be scaled up to be a more practical tourist machine. If and when that happens, then factors like reliability and maintainability will get far more attention than they do with the SS1. After all, a vehicle that's seriously hard to maintain will cost a lot more to operate (see Space Shuttle).

Also, Rutan's pet structural material is carbon-based composites. This class of materials was designed specifically for transonic aircraft. For hypersonic space vehicles it has the severe drawback of igniting and burning at fairly low temperatures. Rutan's firm Scaled Composites made the outer shell of the DC-X military stunt rocket, which actually set itself on fire during a fast landing from the backwash from the rocket exhaust plumes. An aluminum skin would never have noticed this heat, which is far less than that of a reentry. Any serious rocketship made out of composites will need serious heat protection, probably more than one made out of plain old aluminum.

Gary has already addressed this point. Take a look at the reentry vehicles on ballistic missiles. Most of them are based on carbon-carbon and those things get very hot indeed. As for plain old aluminum, you can burn through it very easily with a welding torch. Again, see the Space Shuttle (Columbia) and what happened when the plasma breeched the carbon-carbon and reached the aluminum structure below.

So if I had to bet my money on someone to build the first real private spaceship, it wouldn't be Burt Rutan.

I'll take that bet, especially if Paul Allen stays interested in Burt's work.

Of all the players currently in the running, Elon Musk is the only one who seems to have both the right technical concept and a sufficiently deep pocket to perfect that concept without outside investors.

The problem with Musk's Falcon boosters is that they aren't sexy spaceplanes. They are just regular boring rocket boosters that look like storage tanks. The cheap construction and recovery features are invisible and don't make exciting stories that will appeal to the technically illiterate.

Musk has done some very good work with his Falcon boosters. I wish him nothing but success. His boosters are not designed for carrying people. They're designed to carry satellites into orbit. It isn't that his Falcon V couldn't possibly be man-rated to carry a small space capsule, say 2-3 seats, into orbit. To the best of my knowledge, Musk has not expressed an interest in doing so. Furthermore, at a cost of about $12 million per launch, not counting the capsule, the Falcon V would still be an expensive vehicle to carry paying passengers into orbit.

But dull, boring boosters that reduce the immense cost of orbital launches are just what we need right now. I am not convinced that flying a few rich Baby Boomers on short joyrides can possibly be the basis of a sustained human presence in space (even after reading a dozen articles by alt.space promoters that try to make this case).

Quite a few people were saying the same thing about airline flights up to and through the 1960s. They were still expensive and not too many ordinary people could afford to fly. Good thing there was enough people willing to pay the price or we'd still be depending on trains for passenger travel. It's the same for many technologies - the early adopters pay a premium to get the stuff first. Only the rich could afford the first automobiles. I remember in the late 1970s when the first VCRs players cost $1000 (about $3000 when adjusted for inflation). I remember when CD and later DVD players cost over $500 for basic units that sell for peanuts today.

An orbital booster that cuts the cost of reaching LEO by a modest factor of x5 or x10 would have far more impact. It would change the whole space industry beyond recognition and make real private space flight affordable. That is the private spaceship the world needs -- not Burt Rutan's stuntplane.

Sure, a CATS booster would be great. We may live long enough for someone to actually build one (Falcon is a step in the right direction). In the meantime, the world is big enough for city buses and sports cars, for airliners and racing planes, and for workhorse boosters and tourist spaceplanes. He's setting up a false either-or proposition, a strawman argument. It's simply bogus.