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SpaceShipOne Flight Not as Perfect as it Seemed
ArbiterOne writes "SpaceShipOne's flight wasn't as perfect as it seemed, according to Burt Rutan and New Scientist. Apparently, at one point in the descent, the pilot completely lost attitude control. According to him, "If that had happened earlier, I would never have made it and you all would be looking sad right now." Could this pose some problems for the X-Prize contender?"
Attitudeis the crafts orientation. The article originally said altitude control, I emailed CmdrTaco to fix it before the article went live.
"Prefiero morir de pie que vivir siempre arrodillado!"
Is this a mistake or do pilots really have control over their attitude?
Uh... I would hope they have control over the plane's attitude.
Main Entry: at-ti-tude
5 : the position of an aircraft or spacecraft determined by the relationship between its axes and a reference datum (as the horizon or a particular star)
SpaceShipOne does indeed have cold gas attitude thrusters. You can see a photo of one firing during a test flight here.
In Soviet Rush, today's Tom Sawyer gets high on you.
Once you are in space your inertia will carry you along what ever path you started. So if you start in the proper attitude, and under control, you'll return to the atmosphere in much the same condition. If you leave the atmosphere tumbling out of control, you'll hit it out of control and you'll be far less likely to ever regain it. Indeed, at that air speed, as you drop you into thicker air out of control you are far more likely to suffer complete structural failure. That's bad.
If brevity is the soul of wit, then how does one explain Twitter?
wrong.
Most objects do not spin cleanly about most axes. Rigid bodies (such as books, spaceships, rocks, lollipops, and bullets) have three "principal axes" that pass through the center of gravity and are determined by the mass distribution in the object. There's a "minimum" axis that minimizes the kinetic energy for a given angular momentum -- that's the axis around which the thing is the most clustered. For a screwdriver, the minimum axis generally points down the length of the scredriver shaft. There's also a "maximum" axis around which the thing is the most spread out of any direction. For a flat object like a book or a pancake, the maximum axis points directly out of the flat face. Those are the only two axes around which you can spin the object and have it stay stable.
Any other direction will give rise to precession and tumbling, even in vacuum! You can try it with a book -- most closed hardback books have the minimum axis pointing up through the top of the middle pages, and the maximum axis pointing out through the front of the cover. The third dimension -- pointing out through the spine -- is not stable. Tape a book shut and flip it in the air: if you flip it around the maximum or minimum moment axis it will do what you think -- just flip over before you catch it again. If you flip it around the intermediate axis (by, say, starting with the book facing you right-side up with the spine on the left, and pulling the bottom edge toward you as you throw it up in the air) then you might expect the spine to stay on your left side -- but it will flip back and forth, often ending up on your right side, as the book tumbles in the air. (Remember to tape the book closed before tossing it!).
Anyhow, that's a problem for stopping spin and tumbling, because it's not always obvious which way to fire the cold-gas jets to slow down your rotation: by the time you actually fire them you might have tumbled around so that they are speeding you up instead of slowing you down.
I guess that's why "carefree re-entry" is such a great feature of SpaceShipOne -- it's remarkable that they were able to land safely even without good attitude control at apogee.
The history geeks among us will remember that Yeager had the same problem with that modified F-104 used for NASA pilot training. Enough out of the atmosphere for the aerodynamic controls not to work, but not enough into space for the peroxide jets to function either. I hope SS1 recovers from a spin better than an F-104 does.
What if it is just turtles all the way down?
Say what you will about Reagan, regardless of how you felt about his policies (many were quite controversial), he sure could deliver great speeches.
The best lines in it, however, were paraphrased from John Gillespie McGee's famous poem "High Flight", which is also what Melvill was most likely thinking of. It's a standard reading at the funerals of pilots, and I personally feel that Reagan's speech would have been better, and perhaps more fitting, had he finished with the entire poem. It sums up the main reason why astronauts - military, governmental or private - will always want to strap themselves into something that will never be 100% safe and fly.