More About SpaceShipOne

[Pangloss]

Great article at Aerospace America Online about SpaceShipOne. Lots of technical detail, which I've found to be generally hard to find, about the ship's unique design (even the Wikipedia article is skimpy).

 

http://www.aiaa.org/aerospace/Article.cfm?issuetocid=446&ArchiveIssueID=46

 

It's interesting to compare how remarkably different their flight profiles are from, say, the early Mercury suborbital missions. Rutan & Co'ss choices have been so astonishingly different from conventional wisdom that they could be said to be completely re-writing the way in which we think about space travel.

 

Just to give some examples of that, let's start with the flight parameters. Mercury/Redstone hit a higher altitude and a higher rate of speed (5600mph vs 2600mph, and 60 miles versus 120). Not that that's anything to be ashamed of on SS1's part, mind you. They must have realized that for these early missions, speed simply isn't important. What matters is getting the ship up there. But this is where their method flies in the face of conventional engineering wisdom, which states that you must fly FAST to achieve that altitude, because the air is so thin. But with modern lightweight composite materials, your whole outlook can change.

 

Of course, ultimately it is speed which gets you into orbit, not altitude. The suborbital Mercury/Redstone missions achieved altitudes *higher* than the low point in John Glenn's first orbital Mercury/Atlas mission. But instead of peaking at 5600 mph, Mercury/Atlas peaked at over 17,500 mph -- orbital velocity. This gives some idea of how far the SS1 team has to go in order to achieve orbital flight. (And they'll have to completely re-think their re-entry strategy; more about that below.)

 

Another interesting design choice is the engine, which is described as a "hybrid". The engine development that started the whole American rocket movement was Goddard's liquid-fuel approach. From a mid-20th-Century outlook, liquid fuels make a lot of sense, because they can be started and stopped on command (solid fuel rockets, like the Shuttle's SRBs, cannot be shut off once fired). The down side of liquid fuel is that it's incredibly dangerous and difficult to handle, and it requires very complex engineering to pump it around an engine at high speed. The bigger the engine, the more complex the pumping. The Apollo's Saturn engines and the Space Shuttle's main engines are amazing feats of engineering design. But those liquid fuel pumps alone would make a ship like SS1 *impossible*. On the other hand, solid fuel would have meant more danger.

 

So they went with a hybrid design, which combines solid fuel with a liquid oxidizer, essentially creating a controllable solid fuel design! And to get rid of the oxidizer side of the pumping requirements, they simply pressurize the fuel container. Ingenious. (This stuff wasn't invented for SS1, but it's the first time it's ever been used in a serious rocket system.)

 

And it even gets MORE interesting. Take a look at the video and what do you see? A guy in shirtsleeves doing Mach 3 and 355,000 feet! The TV shows don't really talk about that much; I don't think people realize what an incredible thing that is right there. They actually felt comfortable enough in their vessel design to go with a shirtsleeve environment. No pressure suit, no G suit. Wow. (The article above talks about the hull design a bit.)

 

Unique avionics were also invented, which are discussed in the article. That was interesting as well.

 

The story also talks about the system's unique approach to re-entry. Now it's not really going all that fast, but it's still an important engineering problem. Mach 3 is no slouch in the speed department (SS1, I believe, is the first civilian vessel to ever travel anything *like* that fast; a point which the press has missed completely), but it won't burn up if you just turn off the rocket, point it at the ground and wait. On the other hand, you might lose control of the vehicle, and you don't really want that. So they invented a system where they release the rear connection of the wing to the vehicle, allowing it to flap loosly on a front hinge, which sets up a proper angle of attack. The change in aspect ratio presents more drag than the now-empty vehicle registers in mass, so it slows down, and the whole thing drifts down like a shuttlecock, slow *and* under control.

 

Bizarre. And, by the way, totally computer-free. (Amazingly, there's no computer control of the vehicle at all. None was needed. The article also talks about the three control systems used for the three different aspects of flight, but none of the three are computer controlled.)

 

Anyway check out the article, it's really interesting.

[Alexa]

Whatever the technical choices of the roket, SpaceShipOne has very good chances to get the $10 million from Ansari X Prize. I don't think there will be any surprises for Monday during the second flight.

 

Canadian team, da Vinci tries to hide their disappointment and still want to do their launch this month.

 

Another team disappointed will be the Romanian one with Arca, as the first launch was a succes.

 

And there are the others, I think they were 16 teams in competition, with not a very huge budget.

 

Virgin Galactica already plans space tourism in the next years, so in my opinion our vision regarding the space travel will change very soon.