Slashdot Mirror
NASA Shakes, Bakes, and Rattles Lunar Spaceship
coondoggie writes to tell us that NASA has apparently successfully concluded putting the new Lunar Reconnaissance Orbiter through its paces. Using vibration and rotation tests NASA scientists were able to determine the center of gravity and were also able to observe the structural integrity during the vibration tests used to simulate launch aboard an Atlas rocket. "It is expected that the LRO will by the end of the year make its way to NASA's Kennedy Space Center in Florida for final launch preparations. The orbiter and the Lunar Crater Observation and Sensing Satellite, a mission to smack into the moon in search of water ice, are scheduled to launch atop an Atlas V rocket from Cape Canaveral Air Force Station in Florida sometime between Feb. 27, 2009 and the end of March 2009."
Seriously. We need to test the hell out of this thing:
* Test monster-proofness of hatches and bulkheads.
* Ensure that air filters can handle sapient moon-dust clouds.
Oh . . . this is just a damn unmanned orbiter?
OK. Please forget this post. I'll use it again when they test the Orion lunar craft.
To paraphrase, "So the engineers tested the ship against every conceivable thing that they knew it could withstand." I'm sure the spaceship is now safe.
If brevity is the soul of wit, then how does one explain Twitter?
Will it blend?
"But that's just the beginning, the orbiter will soon undergo four days of acoustics testing during which the spacecraft is placed near massive, multistory, wall-sized speakers that simulate the noise-induced vibrations of launch" Sweet... sign me up, brother.. it'll bring the bong..
... I'll have a Pan Galactic Gargle Blaster with a side of Plutonium Nyborg
. Using vibration and rotation tests NASA scientists were able to determine the center of gravity...
That should be:
If they couldn't determine the center of gravity before they built the thing, they have some serious issues. Vibration characteristics are a bit more difficult, but I suspect the folks at NASA are smart enough determine those before they built the thing too.
One of our competitors trademarked the term "hypothesis". From now on, we will call them "boneheaded ideas".
That's normal stuff. I used to work for a company that built satellites. One of their test fixtures was a shake table connected to a water-cooled voice-coil actuator with a megawatt amplifier driving it. They had accelerometer data from actual launches, and they'd use that to drive the shake table.
I happen to be an aerospace engineer (formerly at JPL), and the center of gravity is actually extremely important after launch as well. NASA is not pulling your leg.
You may replace the "center of gravity" with "mass distribution" or "center of mass" if it makes you feel better. The term is a hold-over from the early days, and is a term of art than any engineer would recognize and understand. You just need the contextual information that an engineering education provides.
The actual product of the test is both a location of the center of mass of the spacecraft and a mass distribution matrix, commonly called an inertia matrix or inertia tensor.
The attitude control system (my specialty) requires very accurate knowledge of where the center of gravity and the geometric centers are. These are used to compute both control and disturbance torques on the spacecraft. Without a C.G test it is almost impossible to get the pointing performance (sub-arc-second) many of the payloads require on modern spacecraft. The CAD/Solidworks models are rarely good enough for this, and although some things can be done to estimate the C.G. in-orbit, you still have to get through launch and initial checkout with whatever data you launched with. C.Gs are estimated in space to handle things like fuel loss.