Saturday, February 14, 2009

Dog Days Come Early This Year

These truly are the dog days of the space age. A space station shaken almost to the point of bending. Space shuttles grounded by cracking valves. Satellites colliding just above the Hubble telescope. Pretty tough stuff for an acting Emperor to deal with, let alone a real one.

And an even larger problem may be lurking around the corner.

One does have to wonder, how the big eyes of the Pentagon, and its super computers on the ground, missed predicting the dust-up on orbit over Siberia. The Pentagon acknowledged that it did not anticipate the ka-boom. "We did not predict this collision," said Bryan Whitman, a Pentagon spokesman, "There are limits on your ability to track and compute every piece of orbiting man-made objects."

Ahhhhh, maybe not every piece, Bryan, but how about the stable bigger stuff? We sure knew how to blow a satellite out of the sky last year when its orbit was not so predictable near the edge of the atmosphere. That's a lot harder to track and predict than what happened last week.

Which also makes us wonder, if they missed that one, what about the smaller stuff aiming for the shuttle headed towards Hubble in May. What about the slightly bigger tool bag recently sent adrift by an astronaut near the space station? If we can't predict two car-sized objects are about to occupy the same box in space at the same point in time, what does that say about the models, the sensors, and the humans generating predictions that lives in orbit depend on every day?

There are only three answers possible. Either a big ooops happened last week, and no one in the five-sided building wants to come clean on that, or the collision was deliberately allowed to take place, and someone left us with a big mess as a result, or our prognostication capabilities are not all that they are cracked up to be. Any conclusion you come to is not a good one.

And we aren't even talking yet about the big asteroid with our name on it hiding in the deepest darkness.


Anonymous said...

strategic command has been falling apart badly
since the Iraq War started.

Stratcom used to be the obsessive watchmakers
of the DoD, they had a culture like the
Submarine force, details, procedure and

The Sub force has been sending dolphins
to Iraq, and i'm sure it's just as bad in
the Nuke force, so we have been seeing
major nuclear errors and now I suspect
somebody just didn't run the collision
prediction right or didn't know how
to interpret the data or wasn't
updating the drag models.

Stevo Harrington said...

There is no way to predict the orbit of satellites to within the precision to know if a collision is imminent. Each satellite is subject to orbital perturbations due to the earth's oblateness, the lunar gravity, the solar gravity, the solar pressure, remnants of atmospheric drag, and magnetic torques. All this are hard to predict with the accuracy necessary to determine if an orbit will intersect another within the ~4 m spacecraft envelope.
For the uncontrolled Cosmos satellite, with an ~800 km orbit at 74 degrees, the regression of nodes is about 1.5 degree per day. So the orbit is moving about 1.5 m/s from just that one effect. . This is not double entry accounting, the answers are not precise enough to predict and prevent collisions. We need to start working on collecting the defunct satellites and putting them in safe orbits or deorbit them entirely. A propulsive electromagnetic tether system,as proposed by Joe Carroll at Tether Applications, would do the job.

Steve Harrington
Lecturer in aerospace Engineering, UCSD

kT said...

There is no way

That's the American spirit!

pat said...

you don't need to predict orbit
within 4 Meters, heck, even NASA
has never predicted that closely,

but can you predict a close approach within
1 KM, it's the same thing the
FAA does in air traffic controller.

Now do we need better radar or
space surveillance?


but could we run bigger models?