Shuttle Clutter

For those who are not Space Cases (meaning fans of the whole Space Industry) here is a bit of a primer on the Shuttle.

The Shuttle is not that big.  Sort of the size of a DC-9/MD-11 airliner, except fatter through the middle where the payload bay and Canadarm are, but basically DC-9 sized.  There are plenty of other aircraft around that are significantly bigger.

The Shuttle and for that matter the International Space Station or any other satellite, have to be going around 17,400 miles an hour to stay in orbit.  That’s the same speed as the Earth spins at, so less than that speed, it falls, more than that, it goes further away.

The S-turns Columbia was performing when it came apart are perfectly normal.  An S-turn increases the drag of the Shuttle to what little atmosphere is there and slows it down.  If the Shuttle doesn’t slow down, the runway would have to be Arizona and New Mexico.

The Shuttle does not have engines like an airplane when it lands.  The whole thing is a big glider when it comes back to Earth.  However, computers can and do control all the landing flying.  The pilot of the Shuttle can take over, but the only time they really get involved is after the Shuttle is over the end of the runway, the last 30 feet or so of landing. 

Landing an airplane without engines running is called a dead-stick landing and is part of every pilot’s training.  Shuttle pilots train incessantly in landing because without an engine, you only get one shot at landing, which is also why the Shuttle lands quickly, moving more than 250 miles an hour at the end of the runway as it comes in.  This gives them lift from the Shuttle wings and body, rather than falling like a brick. 

Gliders do this too: you dive at the end of the runway to pick up speed, to have lift, to land gently.  A 747-400 Best Glide speed is 163 knots, meaning, yes, you can land a 747 without engines in an emergency as long as the forward speed is more than 163 knots the wings give you lift. 

The problem comes in the big S-turns to slow down the Shuttle.  Going so fast, what little air there is, creates friction and heat.  As an example, the Concorde, grows almost 2 inches as it flies.  That is the heat of the air going over the airplane at speed and altitude and is perfectly normal.

The tiles on the outside of the Shuttle are designed to reflect and dissipate that extreme heat.  These tiles aren’t installed by some guy named Gino singing Italian love songs and smoking a cigarette while laying up the tiles.  Each tile is unique, custom manufactured to fit one specific area of the outside of the shuttle.  The tiles can handle more than 2800 degree heat with no big problem. 

The risky bit is the Shuttle, although covered with these tiles, is made of aluminum, some of it not much thicker than the side of a can of Diet Coke.  And this is the way the vast majority of airplanes are made.  Thin aluminum, riveted, glued and bonded together.  Very strong and very light, but put a disposable aluminum pie plate on the stove at home and see it burn and melt and stink something fierce.  Lots of heat and aluminum is a bad thing, which is why the tiles are on the outside of the Shuttle.

Tiles do fall off the Shuttle on every flight.  A few failures are fine, as long as they are not too many in one place.  Each tile has a service life and a service history.  NASA knows everything about every component on the Shuttle, right down to the casting lot and who has ever touched a part of the Shuttle. 

For instance, to change the toilet paper in the lavatory, they don’t just jam a roll of Charmin in there.  The bum wad is custom manufactured for NASA.  They know the content of various fibres, what plant made it, what chemicals were used to make it, when it was made, what packaging went around it, who and what is in the packaging, when it was shipped, by whom, in what truck, what treatment was done to the paper for space use, how many fibres are loose if the sheet is tossed around, or used to blow your nose and so on.  Then, to swap out some paper, there is a written procedure for the technician, who is observed by his supervisor, who then inspects the work, signs it off and turns it over to a second or third team who inspect and check and then check again. 

The joke is, when the stack of paperwork is the same height as the Shuttle, it’s probably ready to fly. 

Could someone sneak a bomb onboard to kill the Israeli astronaut?  Almost impossible.  NASA knows who made the ink in the pens they use, so a stray box that had not been inspected, inside and out, by dozens of people, is not going to happen.  NASA knows.

There is, as best I can tell, no ‘black box’ on the Shuttle.  The whole Johnson Space Center in Houston is the black box. 

I figure about 2/3rds of the radio bandwidth from the Shuttle to Earth is taken up with telemetry.  Everything is measured, constantly, to make sure its working properly.  There are people at the JSC who do nothing but monitor the status of the lights in the lavatory.  Is it burnt out?  Does it work?  Is it overheating?  Does the circuit breaker have any problems? Will it work when needed?  Is it on now? Is it going to turn off properly?. 

This is why the last message from Columbia was about tire pressures.  Houston was checking the pressure in the Michelins to make sure they wouldn’t land on a flat.  If there was a flat, they’d all know about it as it lost pressure in orbit and have procedures for landing with a flat. The default response to anything abnormal is STOP.

Columbia went through a major overhaul in 2000.  This meant the Shuttle was completely taken apart and everything was x-rayed, tested, tapped and blessed.  In aviation this is called a D-Check, where the airplane is torn down to bare metal and inspected up the wazoo for anything even slightly bad, tired, worn out, or just marginal, then fixed, replaced, or given a bath and cleaned up.  Again, everything is signed off, then checked again and again and again then signed off again.  Then audited.

The Shuttle is also a brew of bad chemistry.  Hydrazine, Peroxide, Kerosene, Liquid Oxygen and so on.  These bad chemicals are needed to provide electricity, oxygen, water, rocket thrust and so on for the Shuttle.  NASA knows how to manage these bad things in space and on the ground, but there is still the concept that is core to space flight:  Acceptable Risk.

We take an Acceptable Risk every day.  Gasoline, in liquid form, is dangerous, but you can toss lit matches in a pool of gasoline with little or no problem, aside from stupidity.  Gasoline vapours are the really bad thing.  Toss a lit match in an old car gas tank and it will fly about 20 feet in the air.  If you’ve ever been to the drycleaner, your clothes have been subjected to PERC, perclorethane, or dry cleaning fluid.  PERC is highly flammable, probably carcinogenic and smells horrid.  We still drive around with 43 liters of flammable Regular Unleaded and look snappy when we go out in our dry cleaned dress up duds.

NASA is the Master at Acceptable Risk.  We don’t know, yet, why the Shuttle came apart, but we will in time.  It could be because of thousands of little things all combining at one point in time and space just stacked the cards the wrong way.  In crash investigation, its called the Golden Nugget.  The trick is to find it, document it and figure out how to never have it happen again. 

Give it time and they’ll find it. It could be very complex, or it could be something as simple as Columbia hit a little piece of space junk a week and a half ago that nobody knew about.  They’ll find it.